Strand, London, WC2A 2LL
B e f o r e :
| SCHLUMBERGER HOLDINGS LIMITED
(a company incorporated in the British Virgin Islands)
|- and -
|ELECTROMAGNETIC GEOSERVICES AS
(a company incorporated in Norway)
MR. G. BURKILL Q.C. and MR. G. PRITCHARD (instructed by Lovells LLP) for the Defendant.
Hearing dates: 17th, 18th, 19th, 20th, 24th, 25th, 26th, 27th, 30th June 2008
1st, 2nd, 3rd, 22nd, 23rd, 24th, 25th July 2008
Crown Copyright ©
Mr Justice Mann :
The scientific and physical background
Terminology and concepts
d = 1/√πμσf
Where d is distance, µ is the permeability of free space (a constant for these purposes) σ is the electrical conductivity of the substance and f is the source frequency. In layman's terms, it works out to a reduction to approximately 37% of the original signal - in other words, the skin depth of a substance for any given frequency is the distance over which the signal has attenuated to 37% of its original strength. It will be apparent from that formula that the lower the frequency, the greater the skin depth. Since a lower frequency also means a longer wavelength, it also means that the longer the wavelength, the greater the skin depth or degree of penetration possible. Longer wavelengths give greater penetration. Greater resistivity (lower conductivity) also allows greater penetration.
Wave physics vs diffusion physics
TE & TM mode
If they are broadside, they are effectively parallel, and are positioned thus:
Frequency domain, time domain and transient signals
Dr Terje Eidesmo
He is the President and CEO of EMGS and has worked for it since its birth in 2002. It was spun out of the Norwegian state oil company (Statoil) and he was involved within the Statoil group prior to taking up his present rule. He has a doctorate in Physics awarded by the Norwegian University of Science and Technology and has held a professorship in Petrophysics. He is plainly experienced in the techniques of oil exploration and oil reservoir management. Dr Eidesmo claims to be one of the inventors of the invention embodied in the 019 patent, and he gave evidence of how it came to him, how he procured its testing and what the reaction of others was. His first language is Norwegian, but his English was very good - he did not require an interpreter. The fact that English was not his first language probably explained an apparent unwillingness sometimes to give a simple yes or no answer where he could probably have done so - he was being cautious, not tricky. He came across as a man who plainly wished to defend his invention and who plainly thought that it was an invention. I think that he viewed the reaction of others, to some extent, through those spectacles. I can safely take as accurate his factual account of how the invention was conceived and developed, but I regard with a little more care his accounts of the reaction of others to it. I make it plain that I do not consider that he has told deliberate untruths; it is just that his strength of view as to the novelty of his invention might be thought to have tended to colour his view of the expressed perception of others.
Professor Adam Schultz
Professor Schultz is professor of Marine Geology and Geophysics at the College of Oceanic and Atmospheric Studies at Oregon State University, and gave expert evidence for EMGS. He has a background in geology, physics and mathematics, has a PhD in geophysics, and has done research in both terrestrial and marine geophysics generally. Although he spent a limited time working in the oil industry, his main point of view is that of the academic - a solid earth geophysicist. He gave evidence about the skilled addressee, the 019 and 887 patents and the prior art. He is plainly an experienced man and his evidence was helpful to my understanding of the case. However, I sometimes had the impression that he was a little too concerned to defend a particular corner and be an advocate for his client's cause rather than a completely dispassionate expert. That feature was certainly not so strong as to taint the whole of his evidence, and he had a cross-examination to contend with that was at times quite hostile, but it is a feature which I had to bear in mind when considering the totality of what he said to me. There is, however, one thing I acquit him of. In his final speech Mr Silverleaf sought to paint him as a witness who "sought refuge in obfuscation and diversion". I do not consider him to have been guilty of that. He was plainly uncomfortable with some of the hypotheses that Mr Silverleaf invited him to accept, particularly in relation to the piece of prior art called "Srnka", and wished to consider the matter carefully. To a large extent the sometimes laboured nature of the exchanges is really more attributable to the difficulties in understanding the prior art; I do not consider that Professor Schultz sought to obfuscate.
Professor Martin Landro
He is a professor of Applied Geophysics at the Norwegian University of Science and Technology and was the second expert witness for EMGS. He was able to give me evidence about the use of seismics in geological (and particularly oil) exploration; seismics was (for these purposes) his principal area of expertise, though he obviously had an understanding of wider issues. Again, his first language was Norwegian, not English, but he spoke clear and fluent English without an interpreter. He was inclined to be a bit dogmatic, but subject to that I did not detect the same tendency to fight his side's corner that I detected in Professor Shultz.
Dr Alan Chave
He is currently a senior scientist at the Woods Hole Oceanographic Institution at Woods Hole, Massachusetts. He has had over 32 years experience in studying, teaching, researching, experimenting and consulting in marine geophysics, physical oceanography and oceanographic technology, and was the sole expert who gave evidence for Schlumberger. Unlike the other experts, he had considerable expertise in CSEM, and indeed was the author (or principal co-author) of one of the key pieces of prior art. His expertise was unquestioned, and he was plainly a thoughtful witness, although at times, like Prof Schultz, he tended to defend a particular corner as if defending or arguing a particular case. He brought to bear a strictness of approach, and from time to time found the inaccurate use of scientific language and concepts irritating and frustrating. He might be thought in some ways to be a purist, and a little vein of that sometimes ran through his evidence. It sometimes led him into a degree of dogmatism that was not always appropriate, but he was not overall as dogmatic as EMGS sought to portray him. What I think that I have to bear in mind in relation to his evidence is that his great expertise might have tended to have led him to treat as obvious or clear things which those with lesser experience might have found less so.
The Patents in suit – generally
The 019 patent
" The present invention relates to a method for determining the nature of submarine and subterranean reservoirs. The invention is particularly suitable for determining whether a reservoir, whose approximate geometry and location are known, contains hydrocarbons or water, though it can also be applied to detecting reservoirs with particular characteristics.
"  Currently, the most widely used techniques for geological surveying, particularly in sub-marine situations, are seismic methods. These seismic techniques are capable of revealing the structure of the subterranean strata with some accuracy. However, whereas a seismic survey can reveal the location and shape of a potential reservoir, it cannot reveal the nature of the reservoir.
" The solution therefore is to drill a borehole into the reservoir. However, the costs involved in drilling an exploration well tend to be in the region of £25m and since the success rate is generally about 1 in 10, this tends to be a very costly exercise.
" It is therefore an object of the invention to provide a system for determining, with greater certainty, the nature of a subterranean reservoir without the need to sink a borehole."
"0006 According to the invention, there is provided a method of performing a survey of subterranean strata in order to search for a hydrocarbon containing subterranean reservoir, or to determining [sic] the nature of a submarine or subterranean reservoir whose approximate geometry and location are known, which comprises: applying a time varying electromagnetic field to the subterranean strata; detecting the electromagnetic wave field response; seeking, in the wave field response, a component representing a refracted wave; and determining the presence and/or nature of any reservoir identified based on the presence or absence of a refracted wave component; in which the transmitted field is in the form of a wave, and in which the distance between the transmitter (37) and a receiver (38) is given by the formula
0.5 λ ≤ l ≤ 10 λ ;
where λ is the wavelength of the transmission through the overburden (34) and l is the distance between the transmitter (37) and the receiver (38)."
Again, I have emphasised words whose meaning and effect are important later. The "overburden" is essentially the layer (or layers) beneath the seawater but above the potentially oil-bearing layer. What is sought to be detected, or investigated, is the layer underneath that. That is apparent from the drawing in Fig 2 of the patent which is reproduced at Appendix 2 to this judgment. The patent goes on:
"0007 Given that the distances and geometry of the reservoir will be known from previous seismic surveys, an optimum λ and l would be selected."
"l", the distance between the transmitter and receiver, is known as the "offset". The general nature of the overburden will be known, and the wavelength of the transmission through the overburden can be chosen (if it is to be chosen at all - that is an issue that arises later and I do not intend to pre-judge it here) by reference to the skin depth formula, so that it is not so short as to be likely to fail to get through the overburden, or so long as to penetrate too far.
"0008 It has been appreciated by the present applicants that while the seismic properties of oil-filled strata and water-filled strata do not differ significantly, their electromagnetic resistivities (permittivities) do differ. Thus, by using an electromagnetic surveying method, these differences can be exploited and the success rate in predicting the nature of a reservoir can be increased significantly. This represents potentially an enormous cost saving."
The word "permittivities" was agreed by the parties to add nothing except a modicum of confusion, and should be ignored.
" The present invention arises from an appreciation of the fact that when an EM field is applied to subterranean strata which include a reservoir, in addition to a direct wave component and a reflected wave component from the reservoir, the detected wave field will include a 'refracted' wave component from the reservoir. The reservoir containing hydrocarbon is acting in some way as a wave guide. For the purposes of this specification, however, the wave will be referred to as a 'refracted wave', regardless of the particular mechanism which in fact pertains.
" Be that as it may, a refracted wave behaves differently, depending on the nature of the stratum in which it is propagated. In particular, the propagation losses in hydrocarbon stratum are much lower than in a water-bearing stratum while the speed of propagation is much higher. Thus, when an oil-bearing reservoir is present, and an EM field is applied, a strong and rapidly propagated refracted wave can be detected. This may therefore indicate the presence of the reservoir or its nature if its presence is already known.
"Preferably, therefore, the method according to the invention further includes the step of analyzing the effects on any detected refracted wave component that have been caused by the reservoir in order to determine further the content of the reservoir based on the analysis."
" The transmitted wave also results in a refracted wave 43. This is composed of a downward portion 43a which descends through the overburden 34, a refracted portion 43b which travels along the layer 35, and an upward portion 43c which travels back up through the overburden 34. Since the refracted portion 43b travels much faster through the oil-bearing layer 35 and with far less attenuation, the refracted wave 43 is detected first by the detector 38 and at a relatively high signal level, compared to the direct wave 41 and the reflected wave 42a, 42b."
" Preferably, the applied electromagnetic field is polarized. Preferably, the polarization is such as if created by in-line horizontal transmitter and receiver antennas".
"If the offset between the transmitter and receiver is significantly greater than three times the depth of the reservoir from the seabed (ie the thickness of the overburden), it will be appreciated that the attenuation of the refracted wave will often be less than that of direct wave and the reflected wave. The reason for this is the fact that the path of the refracted wave will be effectively distance from the transmitter down to the reservoir ie the thickness of the overburden, plus the offset along the reservoir, plus the distance from the reservoir up to the receivers ie once again the thickness of the overburden."
" The technique is applicable in exploring land-based subterranean reservoirs but is especially applicable to submarine, in particular sub-sea, subterranean reservoirs."
Claim 1 as granted includes all subterranean reservoirs, but as will appear EMGS proposes an amendment to add a claim 1A which confines itself to submarine reservoirs.
" However, while longer wavelengths applied by electro-magnetic techniques cannot provide sufficient information to provide an accurate indication of the boundaries of the various strata, if the geological structure is already known, they can be used to determine the nature of a particular identified formation, if the possibilities for the nature of that formation have significantly differing electro-magnetic characteristics. The resolution is not particularly important and so longer wavelengths which do not suffer from excessive attenuation can be employed.
" The resistivity of seawater is about 0.3 ohm-m and that of the overburden beneath the seabed would typically be from 0.3 to 4 ohm-m, for example about 2 ohm-m. However, the resistivity of an oil reservoir is likely to be about 20-300 ohm-m. This large difference can be exploited using the techniques of the present invention. Typically, the resistivity of a hydrocarbon-bearing formation will be 20 to 300 times greater than the water-bearing formation.
" Due to the different electro-magnetic properties of a gas/oil bearing formation and a water-bearing formation, one can expect a reflection and refraction of the transmitted field at the boundary of a gas/oil bearing formation. However, the similarity between the properties of the overburden and a reservoir containing water means that no reflection or refraction is likely to occur.
" The transmitted field may be pulsed, however a coherent continuous wave with stepped frequencies is preferred. It may be transmitted for a significant period of time, during which the transmitter should preferably be stationary (although it could be moving slowly), and the transmission stable. Thus, the fields may be transmitted for a period of time from 3 seconds to 60 minutes, preferably from 3 to 30 minutes, for example about 20 minutes. The receivers may also be arranged to detect a direct wave and a wave refracted from the reservoir, and the analysis may include extracting phase and amplitude data of the refracted wave from corresponding data from the direct wave.
" Preferably the wavelength of the transmission is given by the formula
0.1s ≤ λ ≤ 5s;
where λ is the wavelength of the transmission through the overburden and s is the distance from the seabed to the reservoir. More preferably λ is from about 0.5s to 2s. The transmission frequency may be from 0.01Hz to 1kHz, preferably from 1 to 20 Hz, for example 5Hz."
" Preferably, the analyzing means is arranged to analyze phase and amplitude. The data can be analyzed using time domain and frequency domain techniques, and other pulse sharpening techniques. Thus, the data can be made to mimic seismic data so that the conventional seismic post-processing techniques can be employed."
" The present invention also extends to a method of surveying subterranean measures which comprises; performing a seismic survey to determine the geological structure of a region; and where that survey reveals the presence of a subterranean reservoir, subsequently performing a method as described above."
The inventive concept
"The inventive concept of this claim is the realisation that the presence or absence of the refracted wave can act as a discriminator for hydrocarbons."
This makes various things clear. First, there is no claim to have discovered the refracted wave itself. It is accepted that the refracted wave is a physical phenomenon which has always existed and has been identified before. Nor is it claimed that the invention is the detection of the wave. It is narrower than that. It is the use of the wave for the direct detection of hydrocarbons.
The skilled addressee
"The contrast with the EM expert is, in one person there is a much broader range of expertise at their mastery and they would have not to buy in additional help to that extent."
So the CSEM expert shortcuts the need to put together the expertise in bits; but there is still a need to acquire some expertise.
"3. An invention shall be taken to involve an inventive step if it is not obvious to a person skilled in the art …"
Section 14(3) provides:
"14(3) The specification of an application shall disclose the invention in a manner which is clear enough and complete enough for the invention to be performed by a person skilled in the art."
And section 72(1) provides for the revocation of a patent on grounds which include that:
"(c) the specification of the patent does not disclose the invention clearly enough and completely enough for it to be performed by a person skilled in the art."
"30 It seems to me that as a matter of principle invention cannot lie in bringing into a notional team working on a particular problem a new notional member with different skills from those of the existing notional team. The specification necessarily describes the attributes of the team to which it is addressed. Here, the team consists (notionally) of a microbiologist and an enzymologist. There was some suggestion that the patent is addressed to a microbiologist alone, who would have sufficient knowledge of enzymology to put the invention into effect but insufficient insight to appreciate the significance of enzymes in the survival of bacteria or of their spores. I reject this suggestion. The addressee of a specification is the person likely to have practical interest in an invention: here, it is the maker and seller of sterilisation indicators who wishes to make an indicator following the directions of the patent, and I am satisfied that for this purpose he employs a microbiologist with interests in the relevant area and an enzymologist who can carry out the directions of the specification. The notional team will also have a good knowledge of the relevant standards existing in 1988, and will be aware of the simple statistical assumptions which underlie sterilisation detectors."
"In the present case, however, the principle of introducing a rare earth chelate by a dyeing process quite clearly forms part of the solution to the technical problem to be solved … The expert in dyeing cannot therefore be the skilled person who was faced with the task of solving the problem, because the very fact of choosing to introduce rare earth chelates by a dyeing process is the essential feature of the solution proposed. The board consequently takes the view that the skilled person faced with the task of solving the problem posed was not an expert in dyeing, but rather an expert in security materials …"
Later, the board warned against hindsight:
"The technical problem addressed by an invention must however be so formulated as not to contain pointers to the solution, since including part of a solution offered by an invention in the statement of the problem must, when the state of the art is assessed in terms of that problem, necessarily result in an ex post facto view being taken of the inventive step."
"My Lords, a patent specification is a unilateral statement by the patentee, in words of his own choosing, addressed to those likely to have a practical interest in the subject matter of his invention (ie 'skilled in the art'), by which he informs them what he claims to be the essential features of the new product or process for which the letters patent grant him a monopoly … The question in each case is: whether persons with practical knowledge and experience of the kind of work in which the invention was intended to be used, would understand that strict compliance with a particular descriptive word [etc]". (My emphasis)
"I would add that although it has to be remembered that a specification may fail to provide sufficient details for the addressee to understand and apply the invention, and so be insufficient and invalid, it is often possible to deduce the attributes which the skilled man must possess from the assumptions which the specification clearly makes about his abilities."
That is the case in the matter before me. It is clearly possible to deduce that the skilled addressee is to have an expertise in CSEM techniques, surveys and analysis. The skilled addressee is assumed to have the ability to carry them out.
"In some cases a patent claim may cover a wide field so that some parts of it will be obvious to the notional skilled person in one field and other parts will be obvious to the notional skilled person in another. That is not unfair to the patentee … but [is] simply a reflection of the fact that the scope of the protection sought is wide. I accept, of course, that in some cases there will be invention in marrying together concepts from two unrelated arts, but that is not what Mr Carr is arguing for here."
"It is therefore clear that the relevant person must have skill in the art with which the invention described in the patent is concerned. In some cases the patent may include within it information derived from or utilising more than one aspect of science or technology and in such cases the notional skilled addressee, the person skilled in the art, will consist of a combination of scientists or technicians having those skills …"
Points of construction
Contemporaneous evidence going to obviousness
i) The expert evidence is the primary evidence; the contemporaneous evidence is relevant, and has the merit of being untainted by hindsight, but secondary. It can be used to test the expert evidence.
ii) There is a danger in getting too caught up in an investigation of what was and what was not obvious to certain identified (and even more so unidentified) individuals, because they may not all have been aware of the state of the art - the state of the art (within the meaning of the statute) is the important starting point.
iii) The evidence may invite a degree of inadmissible speculation as to the inventiveness of the persons involved.
iv) Commercial success (if relied on) may be attributable to novelty (want of obviousness), but there may be other factors operating. Care must be taken to ensure that is not the case.
v) The importance and weight of the evidence will vary from case to case.
The history of the invention and subsequent events
"Statoil proposes the use of seafloor electromagnetic (EM) sounding as a fluid predictor over existing prospects. The seafloor EM method is not new - it has been in development for nearly 20 years and is being carried out by universities such as Cambridge, Toronto, and Scripps Institute of Oceanography. I personally have been active in this field for 16 years. The method works by injecting EM energy of around 1 Hz into the seafloor. Measurements of attenuation as a function of range and frequency provide estimates of seafloor resistivity. The proposed application to direct detection of hydrocarbons is, to the best of my knowledge, novel." (My emphasis)
The emphasised words are relied on by EMGS. I shall return to them. The letter goes on (omitting irrelevant parts):
"The conclusions of the model assessment are that if the target is not too small compared with its depth of burial, and the water depth is sufficient to suppress the air wave, then the controlled source signature of the oil-filled layer is detectable, yielding the controlled source amplitudes that are a factor of 2 to 10 different than for models without the oil layer. The signals are above the noise threshold, and the experimental parameters (frequency, range, antenna length, and power) are practicable."
That paragraph is merely approving techniques. It does not purport to express a view on novelty. The letter goes on:
"The study also showed that (i) an inline Tx/Rx gives a stronger signal than the parallel Tx/Rx case, (ii) the method is robust to variations in overburden resistivity typical of well logs, and (iii) that controls on location and depth from seismic studies can be used to optimize survey parameters and generate off-target/on-target discriminators.
"There are weaknesses to the study: computer models of a 3D source and 1D target could have been carried out fairly easily with publically [sic] available code, and one of the analogue model studies used radar frequencies and wave propagation rather than the diffusive propagation necessary to detect deep targets. However, the work took the group from almost no experience in this field to having a reasonable physical insight into the method. Their conclusions are not only basically correct, but they have discovered properties of the method known only to a very few experts (ie that the parallel/inline mode split is diagnostic of buried layers)."
This commends the techniques, and the research, but does not suggest novelty. On the contrary, it concludes that the work has brought the group up to speed with others, albeit only a very small number of others.
"I used a 3D source/1D target code during my visit to verify Statoil's qualitative and quantitative conclusions. I would also note that the choice of controlled source EM is appropriate, as a thin resistive layer is invisible to other commonly used EM method, magnetotelluric sounding. In conclusion it is my opinion that the proposed method has a reasonable chance of success for sufficiently large targets (the type being suggested)."
"I wish Statoil every success in its endeavour; it is pleasing to see innovative research coming out of the industry sector."
"However, I explained to Nancy Wilson (my contracts officer) that (a) this was a great research project that was going to make us all famous …"
That, again, is relied on by EMGS to demonstrate contemporaneous views of novelty.
"'I will say that in my opinion a positive field test will change dramatically the field of active source EM (and may be MT) because of the large impact this will have for the oil industry.' I'm continuing with some modelling, but nothing I've seen yet discourages me at all."
"Sea Bed Logging (SBL), a new method for remote and direct identification of hydrocarbon filled layers in deepwater areas."
"The array of sea floor receivers measures both the amplitude and the phase of the received signal that depend on the resistivity structure beneath the sea bed. A survey consisting of many transmitter and receiver locations can be used to determine a multi dimensional model of sub-sea floor resistivity."
No-one has suggested that so far this describes anything new. The epitome goes on:
"In deepwater areas the geological strata are generally dominated by shale or mud rocks with rather low resistivity. A hydrocarbon reservoir can have resistivity perhaps 10 – 100 times greater. With an in-line antenna configuration the transmitted electric field enters the high resistive carbon layer under a critical angle and is guided along the layer. Electro magnetic signals constantly leak from the layer and back to the sea floor. The guiding of the electric fields significantly alters the overall pattern of current flow in the overburden layer."
"A broad-line antenna configuration does not generate guided waves, and thus the two antenna configurations have different sensitivity to thin buried resistive layers. This so-called 'split' effect that is diagnostic for buried resistive layers is verified by 1-dimensional modelling. 1- and 2-dimensional modelling and real data acquired offshore West Africa also demonstrate that by careful positioning of transmitter tow tracks and receivers relative to suspected hydrocarbon bearing structure, the SBL technique can provide detailed information on the presence and lateral extent of the hydrocarbon reservoir."
This last part of the epitome describes the technique used by the 887 patent, and the essence of the invention is described in the closing reference to the detection of hydrocarbons.
It goes on to describe the method which depends on differential resistivity.
"The objective of the survey was to demonstrate that the SBL technique could be used in a practical situation to directly detect hydrocarbon filled layers in the subsurface in deepwater areas…."
The paper claims to have proved that the results of the survey coincided with the modelling predictions.
i) Another paper by Prof Constable, in which he said:
'The marine CSEM method is not new, but the application to hydrocarbon detection is.'
ii) A talk given by Mr Dave Peace to the Petroleum Exploration Society of Great Britain in October 2005 in which he said:
"These methods have however been rightly regarded as somewhat fringe geophysical methods of use only as regional exploration tools of low resolution and then only suitable for applications in certain more difficult geological provinces such as sub-salt, sub-basalt, sub-carbonates etc.
"EM methods have recently undergone a metamorphosis and the new Controlled Source Electro-Magnetics (CSEM) techniques are now showing that modern electromagnetic techniques can and are being used around the world to help evaluate the fluid content of reservoirs, define reservoir extent and even 'quality' to some extent."
"The method has been used in academia for many years, primarily to study ocean basins and active spreading centers. However, this survey is the first application to direct hydrocarbon detection."
"From an academic point of view, this project was an application of standard CSEM practice and represents no new techniques, just a novel target. However, I don't see any harm in introducing SBL as a terminology - I can appreciate that it looks good within Statoil, and it will probably help 'sell' the technique."
And on 3rd May 2002 he returned to the topic in an email, apparently in the context of a request to keep certain "proprietary know-how and technology" confidential. He was obviously a little puzzled about this, because he said:
"However, as someone who has worked in marine controlled source electromagnetic sounding (CSEM, aka 'seabed logging') for nearly 20 years, it is not clear to me what intellectual property Statoil is claiming in this regard. CSEM as practised off Angola is an innovation pioneered by Scripps Institution of Oceanography over 20 years ago, and indeed your colleagues visited me and Charles Cox in late 1998 to learn more about it from us. Also, the use of CSEM for hydrocarbon exploration has been advocated for some time, see for example Hoversten … and indeed appears in my proposals for my 'Seafloor Electromagnetic Methods Consortium' since at least mid-1998."
i) At the hearing Prof Sinha said that Dr Eidesmo and Mr Ellingsrud told him that they had found the "split" - the difference between in-line and broadside signals when compared in and in the absence of a hydrocarbon layer. Prof Sinha said he was not initially convinced there would be one. That is said in these proceedings to support the novelty of the invention in the 887 patent.
ii) No evidence was produced by Prof Sinha or Dr MacGregor to show that they contemplated using EM methods for the direct detection of buried hydrocarbon reservoirs despite contacts and presentations to oil industry representatives in the late 1990s. The hearing officer found that when asked in 1998 by an oil company whether an EM survey could be used for direct hydrocarbon detection, Prof Sinha said it would not be possible using magneto-telluric techniques and apparently did not even consider whether CSEM techniques would work.
iii) Prof Sinha and Dr MacGregor were offering CSEM techniques for detecting sedimentary layers below basalts. Nothing in their evidence suggested they contemplated using CSEM directly to detect thin relatively resistive layers in more conductive substrates.
Industry reaction and commercial success
"Electro-Magnetic explorations methods have been around … as deep water marine methods since the mid-1990's when Marine MT was essentially declared a commercial exploration tool. These methods have however been rightly regarded as somewhat fringe geophysical methods of use only as regional exploration tools of low resolution and then only suitable for applications in certain more difficult geological provinces such as sub salt, sub basalts, sub carbonates etc.
"However with the addition of higher frequency source and a change in the basic geophysical technique, EM methods have recently undergone a metamorphosis…"
"He was hired by Exxon in the 1980s to apply the method [of using the electromagnetic properties of earth water and rock] to finding oil but was stymied for years by technological and funding hurdles."
It goes on to describe how electromagnetics was referred to at a certain workshop, and comments:
"This was hardly a breakthrough concept in the industry. Oil is a resistive material … Scientists have nurtured the notion that the same technology could be used to explore for oil from the surface … But the idea had been discredited by a succession of failures … All the computer models looked good, but Dr Srnka told his bosses [at Exxon] that the project would take years, cost millions and be very risky … Executives decided to pass. At that time, 3D seismic technology was all the rage. And companies weren't yet able to work in the deep waters suited to Dr Srnka's method."
"However, with modern recording equipment in low noise environments, higher frequency signals can be detected in moderate water depths."
This potentially attributes the new-found preferences to better equipment.
Common general knowledge and mindset
"The common general knowledge is the technical background of the notional man in the art against which the prior art must be considered … It includes all that material in the field he is working in which he knows exists, which he would refer to as a matter of course if he cannot remember it and which he understands is generally regarded as sufficiently reliable to use as a foundation for further work or to help understand the pleaded prior art. This does not mean that everything on the shelf which is capable of being referred to without difficulty is common general knowledge nor does it mean that every word in a common text book is either. In the case of standard textbooks, it is likely that all or most of the main text will be common general knowledge." (My emphasis)
Mr Burkill stresses the underlined words as excluding the more arcane and detailed parts of the Chave paper. So far as the exploration geophysicist is concerned, he is in my view right to do so. Such a person would not have that material as part of his common general knowledge. However, he is also right to accept that the overall significant pieces would be common general knowledge by the priority date. They would be added to Kearey and Brooks for that purpose.
" … some knowledge latent or otherwise, of the working of commercial cyclones" (para 33)."
Despite that, the mindset of the vacuum cleaner industry, of which the engineer was part, was such that there was an "addiction" to bags such that he would not have thought of using a cyclone as a dust separator. Mr Fysh does not seem to have relied on latency as a reason for suppressing the realisation of the utility of cyclones; rather he remarked on the latent general knowledge as existing despite the "addiction". Mr Burkill says that in the present case there would be latent knowledge of CSEM generally (and of the less detailed parts of the Chave prior art) in the same way. It co-existed with a mindset in the industry which held that CSEM had nothing particularly useful to contribute over seismic techniques when it came to discerning potentially hydrocarbon-bearing layers.
"Since most hydrocarbon reservoirs are deeper, it is reasonable to say that EM methods lived a life in the shadow of seismic methods."
The prior art and the 019 patent
"Recent developments in instrumentation and submarine geology have spawned increasing interest in the use of electromagnetic (EM) methods for seafloor exploration. Previously, little attention had been given to their use in the marine environment, due both to the success of the seismic techniques in delineating sub-surface structure and to a pervasive belief that the high electrical conductivity of seawater precluded the application of EM principles. Marine EM exploration of the solid earth has progressed substantially in academic circles over the past two decades; the adaptation of this technology for commercial purposes is only beginning.
"Over three-fifths of the Earth's surface is covered by oceans. Even though petroleum is produced from huge deposits on the relatively shallow continental shelf, the immense area of the ocean represents a largely unexplored and an exploited resource base. Until recently, little economic interest was shown in the ocean floor environment ... however, the recent discovery of intense hydrothermal activity and poly-metallic sulphide deposits of unprecedented concentration and scale on the crest of the East Pacific rise ... has aroused interest in the possibility of deep-sea mining and spurred research into the mid-ocean ridge ore genesis as an analog to terrestrial occurrences ... While [ visual location is] capable of examining its surficial geology, they are not able to adequately assess the actual extent of the deposits and the nature of the geological structures in which they are found. Seafloor conductivity mapping is one of the few geophysical tools suitable for this purpose, just as the EM methods are one of the major geophysical techniques used in mineral exploration on land.
"Over the past few decades, the search for petroleum reserves has been extended from the continent's off-shore into progressively deeper water, making the continental shelves a focus for geophysical exploration. The principal geophysical tool for this is the seismic method, and the success of the seismic approach is attested to by the level of offshore drilling activity and the subsequent production of oil. However, there are marine geological terranes [sic] in which the interpretation of seismic data is difficult, such as regions dominated by scattering or the high reflectivity that is characteristic of carbonate reefs, volcanic cover, and submarine permafrost. Alternative, complementary geophysical techniques are required to study these regions.
"... This paper emphasises the differences between seafloor and terrestrial EM applications, especially with regard to noise, resolving ability, and apparatus....Most of the existing work on seafloor EM has been motivated by solid earth problems as opposed to exploration ones. The real data discussed reflect this difference, which is principally one of scale."
"The choice of operating an EM system in either the frequency domain, transmitting a set of discrete frequencies one or a few at a time, or the time domain, transmitting a square or triangular step and measuring the transient response of the seafloor-ocean system, also exists. The physics of the two methods are identical, the response in one domain being the Fourier transform of the response in the other domain. Because of the finite and inexact nature of practical measurements, this transformation cannot usually be made outside the realm of theoretical studies. The choice of one system over another must be made on the basis of practical and logistical considerations."
"It is instructive to examine the behaviour of the horizontal electric field for geometric (range-dependent) and parametric (frequency-dependent) soundings in the presence of the simplest structural complication, a buried layer. In each case a specific model consisting of a half-space of conductivity 0.05S/m containing 1 km thick layers either 10 times more or less conductive and centered at depths of 1.5 and 5.5 km is considered; these values are intended only to be illustrative. Figure 16 shows the geometric sounding curves. The low conductivity zone behaves as a lossy waveguide which traps and guides the signal, resulting in slower attenuation with range when compared to the half-space case. The deep buried layer produces a smaller effect, as expected from the diffusion nature of EM induction, and requires a larger range for the trapping to become apparent. If the buried layer has a higher conductivity than the surrounding material, greater attenuation will ultimately result at long range, but the low conductivity waveguide created between the seafloor and the layer results in an increase in signal strength at intermediate distances. The HED [horizontal electric dipole] method is preferentially sensitive to relatively low conductivity zones due to the presence of the TM mode. The existence of a minimum usable source-receiver spacing of 1-3 times the burial skin depth, depending on the sense of the conductivity contrast, is also apparent. Longer ranges are required to detect low conductivity material. Figure 17 shows parametric sounding curves for the same model at ranges of 5 and 10 km."
"The layout is based on the same frequency domain dipole-dipole system used for deep sounding, so the theory developed by Chave and Cox (1982) and Chave (1984b) is directly applicable. In particular, it may be shown that resistive features such as permafrost layers and basalt flows can be mapped using frequencies and source-receiver ranges attainable by the experimental system ..."
I cite this and the previous reference to basalt because they are relied on by Mr Burkill.
i) It does not teach a method for searching for a hydrocarbon-containing reservoir;
ii) It does not teach a method of determining the nature of a submarine reservoir;
iii) It does not teach seeking a component representing a refracted wave and determining the presence and/or nature of any reservoir identified based on the presence or absence of such a component.
iv) It does not teach the relationship between source-receiver separation and wavelength (integer 10).
"First, if the prior art describes something falling within its scope then, assuming that the description is enabling, the claim is anticipated. In such a case it is not necessary to carry out any experiments, or give evidence of what would have happened if the prior art were put into practice, because it already describes what it achieves …
"The second way of proving anticipation is by showing that the inevitable result of carrying out what is described in the prior art would be a product or process falling within the scope of the claim." (p436)"
He relied on the well-known statements in General Tire and Rubber Co v Firestone Tyre and Rubber Co  RPC 457 at 485:
"To anticipate the patentee's claim the prior publication must contain clear and unmistakable directions to do what the patentee claims to have invented … A signpost, however clear, upon the road to the patentee's invention will not suffice, the prior inventor must be clearly shown to have planted his flag at the precise destination before the patentee." (my emphasis)
"Given that the distances and geometry of the reservoir will be known from previous seismic surveys, an optimum λ [wavelength]…would be selected."
A wavelength would be chosen by reference to the thickness of the overburden - one would certainly not want one which gives a shorter skin depth than that thickness. The maths works out with the effect that the wavelength corresponding to a skin depth can be related as follows:
λ = 2π times skin depth (δ).
2π is roughly 6, so the formula becomes:
λ = 6δ
That can be treated as common general knowledge. Dr Chave gave undisputed evidence about that. If one then applies that to the wavelength formula in claim 1, one sees that the offset is said to be between 3 and 60 times skin depth. The outer limits are very extreme, but what this integer teaches is that the offset is to be greater than three times skin depth, and perhaps much greater than three times skin depth. The Chave paper, in commenting on the modelling, teaches that:
"The existence of a minimum usable source-receiver spacing of 1-3 times the burial skin depth, depending on the conductivity contrast, is also apparent."
It extracts this from graphs of the modelled results which show a less attenuated signal emerging at different ranges depending on the depth of the buried layer. There was a dispute between the parties as to whether the Chave paper was confining itself to suggesting offsets within the range of 1 to 3 skin depths (Professor Schultz's view of the paper), or whether the range of 1-3 times skin depth was the starting point for an extending range of offsets going beyond the 3. I consider that Schlumberger's arguments on this are correct. Professor Schultz's arguments ignore the effect of the word "minimum". The Chave paper proposes 1-3δ as a starting point for offsets - the offsets might be greater (see the word "minimum"). Relatively conductive layers are at the bottom of the range, and relatively resistive layers are at the top. That means that the latter starts at 3. That is the starting point for wavelength formula in Claim 1. What the integer does is introduce a non-inventive refinement of what has already appeared in Chave. If there is a difference, it is covered by obviousness.
Claims 1B and 1C
Claims 2, 11 and 16
The remaining prior art in relation to the 019 patent
"There are numerous regions in the world where the presence of shallow high velocity layers makes the imaging of deeper structure using conventional seismic reflection techniques a difficult task. Of particular interest are continental shelf areas where potentially oil bearing sedimentary structures are obscured by layers of basalt, carbonate or salt. These high velocity layers limit the penetration of seismic waves and can cause reverberations which mask reflections from deeper sedimentary structures, leading to ambiguities in interpretation.
"Additional constraint on the structure can be gained by studying the electrical resistivity. The resistivity of basalt, carbonate and salt is typically in the range 100-1000 Ωm, whereas the resistivity of the surrounding sedimentary sequences are typically 1-10 Ωm. This marked contrast provides an ideal target for electromagnetic prospecting techniques. By mapping such variations in resistivity many of the ambiguities inherent in conventional seismic techniques can be resolved. In addition sediment resistivity is in itself an interesting property to measure."
The method is then set out -- it is essentially an abbreviated account of CSEM:
"The controlled source electromagnetic sounding method uses a horizontal electric dipole source ... to transmit a discrete frequency electromagnetic signal to an array of sea bottom receivers which record two orthogonal components of the horizontal electric field at the seafloor. Because the resistivity of the seawater is less than that of the seafloor, the signal in the water is rapidly attenuated, with the result that the fields measured by a receiver remote from the source have followed crustal diffusion paths. During the experiment the source is towed at a height of about 50 m from the sea bottom, within the array of receiving instruments. By studying the variation in the amplitude and phase of the received electric field as a function of source receiver separation and geometry, and the frequency of the signal, the resistivity structure of the underlying crust can be determined. Frequencies in the range 0.25-40 Hz are transmitted in a typical experiment. Lower frequencies lack the resolution of crustal scale structures which are of interest ... At higher frequencies only signals at the very shortest source-receiver separation can be detected above the ambient noise level. Such signals contain little information about the sub-surface resistivity structure. The range of frequencies which in practice can be employed is therefore quite limited.... Although depths of resolution up to 30 km have been achieved in the past … the strength of this technique lies in the resolution of shallower (0-5 km depth structure)."
Of particular interest is the problem of imaging conductive sedimentary structure beneath more resistive layers such as basalt...
We wish to establish if the controlled source electromagnetic technique can detect the sub-basalt sediments, and if so how accurately their depth of burial, thickness and properties can be determined."
"It is clear that the presence of the sub-basalt sediments can be detected, and that the three models can be distinguished using these synthetic datasets, which are comparable to those which could be collected in practice. The resistivity of the sub-basalt sediments is recovered well, and the presence of the basement beneath can also be detected.... for the examples shown this method locates the base of the basalt layer to within 200 m.…"
"The variation of the electric field with source-receiver separation and geometry and the frequency of the transmitted signal can be used to determine the sub-seafloor resistivity structure."
The refracted wave is part of that, but is not clearly identified as a key thing that is utilised.
"An improved method and apparatus for electromagnetic surveying of a subterranean earth formation beneath a body of water. An electric dipole current source is towed from a survey vessel in a body of water substantially parallel to the surface of the body of water and separated from the floor of the body of water by a distance less than approximately one-quarter of the distance between the surface and the floor. Alternating electric current, preferably including a plurality of sinusoidal components, is caused to flow in the source. An array of electric dipole detectors is towed from the survey vessel substantially collinearly with the current source. Each electric dipole detector of the array is separated from the current source by a distance substantially equal to an integral number of wavelengths of electromagnetic radiation, of frequency equal to that of a sinusoidal component of the source current, propagating in the water. A gradient detector array is also towed by the survey vessel in a position laterally separated from, or beneath, the mid-point of the current source. Additionally, an array of three-axis magnetic field sensors mounted in controllable instrument pods are towed by the seismic vessel on the flanks of the current source. Frequency-domain and time-domain measurements of magnetic and electric field data are obtained and analysed to permit detection of hydrocarbons or other mineral deposits, or regions altered by their presence, within sub-floor geologic formations covered by the body of water."
"Electromagnetic survey systems are being used increasingly to explore for oil and gas on land. However, at present, practical methods for exploring for oil and gas in the offshore environment are restricted to the measurement of the natural magnetic and gravitational fields at the earth's surface, of the reflection of seismic energy from subsurface structures, or the seepage of chemical substances from mineral deposits beneath the sea floor into the sea water or atmosphere. Although passive techniques such as natural-source magnetotellurics can provide useful information about the lower crust and upper mantle, electromagnetic sounding techniques employing an active source are better suited for surveying subterranean formations within five to ten kilometres beneath the sea floor. Because practical techniques for active electromagnetic sounding of earth formations beneath the sea floor have not hitherto been known, the electrical structures of continental margins and offshore basins remain largely unknown, despite the scientific and economic importance of these areas….
"'Resistivity' methods using an active source of direct electric current, or very low frequency alternating current…have been proposed for determining the apparent resistivity of geologic formations beneath the sea…"
"According to the method of the invention, an electric dipole current source is towed from a survey vessel in a body of water substantially parallel to the surface of the body of water and separated from the floor by a distance less than approximately one-quarter of the distance between the surface and the floor. Alternating electric current is caused to flow in the source, said current including at least one sinusoidal frequency component. At least one electric dipole detector, including a pair of detector electrodes, is also towed from the survey vessel substantially collinear with the current source and spaced from the current source by a distance substantially equal to an integral number of wavelengths of electromagnetic radiation propagating in the water and having frequency equal to that of the sinusoidal component. A characteristic of the current emitted by the source and a characteristic of the potential difference between the pair of detector electrodes are measured. From these measurements, a characteristic of the "complex mutual impedance" of the current source and the dipole detector is determined. Preferably the current emitted by the source includes a plurality of sinusoidal components, each having a distinct frequency. Preferably, several dipole detectors are towed collinearly with the source. Measurements of the current characteristic and the potential difference characteristic should preferably be made at a plurality of frequencies for each source-detector pair…
"Potential difference measurements at the electrode pairs of the gradient array and dipole array, and magnetic field measurements at the magnetic field sensors, are made while the vessel is moving or stationary, and the measurements are interpreted to permit the detection of hydrocarbons or other mineral deposits, or regions altered by their presence, within sub-floor geologic formations covered by the body of water. Frequency-domain measurements of magnetic and electric field data are analysed to construct the complex impedance spectrum of the sub-floor formation beneath each survey station…"
"…The potential differences between [the source and transmitter electrodes] are measured and amplified, and thereafter further processed and recorded by electrical equipment…aboard [the] vessel. The measured data is interpreted in a manner to be discussed below, to permit characterisation of earth formation beneath floor of body of water and to locate regions in sub-floor formation which possess 'anomalous' properties indicative of mineral deposits. In a particular application, the measured data is interpreted to determine the presence and depth of a buried resistive layer, such as resistive layer 25, which has a resistivity different from the average resistivity of that portion of [the formation above that layer]."
Layer 25 is a reference to one of the drawings (I have omitted other numeric cross-references to drawings). It shows a layer below the overburden similar to the layer shown in the drawing of the patent. The italicised words in the above passages are my emphasis in order to identify terms which are important to the patent and which cause problems of interpretation.
"It is preferred that [the source dipole] and the electric dipole detectors be towed substantially collinearly, substantially parallel to [the] surface, and in approximately the lower quarter of the column of [the] water between [the] surface and [the] floor. As the depth below surface at which dipole current source and the dipole detectors are towed decreases to less than three-fourths the distance between the floor and the surface, the strength of the signal at the dipole detectors which is indicative of the electrical resistivity of the sub-floor formation (the 'anomaly' signal) rapidly decreases due to masking by the water between the floor and the dipole detectors. It is additionally desirable to tow the apparatus within the lower quarter of the column of water between surface and floor because in that region, the sensitivity of the anomaly signal to the height above floor at which the apparatus is towed is sufficiently weak that fish need only control the actual tow depth to within about 5% of the desired tow depth.
"If [the source electrodes] are separated by a first distance, and adjacent pairs of [detector electrodes] are also separated by substantially the first distance, then for direct detection of buried resistive layer located a second distance D, below floor, the mid-point of current source and the mid point of one of the electric dipole detectors should be separated by at least two D and preferably should be separated by at least three D. Also for detection of [the] buried layer, the output current at [the source dipole] should preferably include a sinusoidal component having frequency equal to the 'skin depth frequency' associated with [the] buried resistive layer. Such skin depth frequency [and here the patent sets out the skin depth formula referred to above]…is that frequency which makes the electromagnetic skin depth in the [overburden] equal to the depth, D, of the buried resistive layer". [This recitation omits the cross-referencing to the drawing but is sufficiently clear without it.]
"...I have found that the influence of the electromagnetic coupling directly between [the] source and each dipole detector (which coupling is independent of the characteristics of earth formation [in the overburden]) on the potential difference measurements at such dipole detector may be desirably reduced by spacing each such dipole detector from the source an integral number, n, of wavelengths λw of the electromagnetic signal from [the] source. Wavelength λw is given by [a given expression]. If [the source and detector] are so spaced from each other, all of the changes in the phase of the signal measured at each detector (relative to the phase of the output current at [the] source) are due to electromagnetic signals propagating along or below [the] floor…
"If it is desired to make the surveying system particularly sensitive to a resistive layer buried at a depth D below the floor, and if the average conductivity…of [the overburden] is known to a depth just above depth D, then the separation between [the source and detector] should be chosen to be substantially equal to an integral multiple of 2πD(ρωσ)½ and the source current should be chosen so as to include a sinusoidal component having frequency substantially equal to the skin depth frequency associated with depth D.
"It is desirable to generate, from the potential difference measurements made at each dipole detector, a signal indicative of the complex mutual impedance of [the source and detector]. From analysis of variations or 'anomalies' in the phase and amplitude of such complex mutual impedance signal, the presence of a buried resistive layer such as [the layer shown in the drawing] may be determined. I have found that the depth to such buried layer may be estimated by employing a plurality of detector dipoles in the electric dipole detector array and employing a variable frequency dipole source, and making potential difference measurements at each detector for each of a plurality of distinct source frequencies. In particular, it has been found that the frequency at which the phase or amplitude anomalies indicative of [the] buried layer are at a peak (or maximum) will decrease as the separation between source and detector increases, until such separation increases to a critical separation equal to three times the depth of [the] buried layer beneath [the] floor. Beyond such critical separation, the value of source frequency giving the peak signal anomalies remains substantially constant. By determining the value of such substantially constant frequency…the depth of [the] buried resistive layer may be estimated as…"
"the linear relationship between the EM field and a source current for a given frequency source receiver offset in geometry." (Dr Chave)
In more everyday terms it can be viewed as the strength and phase of the received signal. The complex mutual impedance instructions involve comparing the amplitude and phase of the received signal with the amplitude and phase of the source signal. They will vary in accordance with the frequency and in accordance with offset.
i) What does it actually teach?
ii) Does its teaching enable?
iii) Does its teaching anticipate? This raises two points - does it teach sufficiently unambiguously to anticipate; and if so, does it actually anticipate?
What does Srnka actually teach?
i) The carrying out of a marine CSEM survey with fairly conventional equipment, though not conventionally arrayed.
ii) Looking for and analysing an "anomaly" signal.
iii) There is some teaching about spacing of source and detector and frequencies.
iv) There is some teaching about spacing source and detector by reference to whole wavelengths of the signal in water.
v) It plainly has in mind the context of a hydrocarbon (or potentially hydrocarbon) layer, though it also refers to minerals generally.
Disputes arise out of a number of those elements.
"All that the skilled addressee reading Srnka could do is to measure the electromagnetic field as a function of range, frequency and geometry. Srnka refers to different readings as 'variations' or 'anomalies'. Analysis of such 'anomalies' to determine the resistivity of the reservoir under investigation is, and would have been understood by the skilled addressee to be, the same as 'seeking the refracted wave' … Neither Srnka nor the 019 Patent discloses the details of this analysis/seeking."
I am not sure how clear that is as to what Dr Chave actually thought the expression meant, as opposed to what he thought the "anomaly" reflected in experimental results. It does, however, appear that he did not view the determination of the anomaly as a comparative exercise; he regarded the measurement taken as being an absolute measurement. His position became clearer in cross-examination, when it seems he accepted that his initial view was the same as Professor Schultz's.
"the solid earth geophysicist or EM Expert would regard Srnka's statement as indicating that variations in the phase or amplitude of the complex mutual impedance are equivalent to 'anomalies'.
"116 … I conclude that the dependent variable ie the observable, is the amplitude or phase of the complex mutual impedance, and that there must exist independent variables (eg source-receiver offset, source signal frequency, resistivity) which, by varying, would lead to changes in the complex mutual impedance. It is those changes that Srnka calls the 'anomaly' ..
"124. The EM Expert would understand Srnka to teach that one should scan at various frequencies to find, for each offset, the frequency at which the phase and/or the amplitude is greatest. I believe that Srnka is teaching that behaviour between the offset and the frequency of the peak value would be something similar to the following:
"126. Therefore it is my belief that the reader would expect that by graphing the amplitude or phase of the complex mutual impedance as a function of both offset and frequency, he could identify a constant frequency Fc (ie the frequency at which the above curve levels off) that indicates the presence and depth of a resistive layer."
At paragraph 123 he had observed:
"123. Srnka expects that this relationship will have two distinctly different behaviours depending on the separation between the source and the receiver.
"(a) At separations less than approximately three times the depth to the buried layer, Srnka says that as the separation between source and receiver increases the frequency giving rise to the peak 'anomaly' will decrease.
"(b) Srnka then says that at a critical separation equal to three times the depth of the buried resistor, there will be a change in behaviour, namely that the value of frequency giving the peak 'anomalies' will then remain substantially constant."
Professor Schultz did not seek to justify his view by reference to any textual or other reasoning, but he did elaborate on the meaning.
"To anticipate the patentee's claim the prior publication must contain clear and unmistakable directions to do what the patentee claims to have invented . . .
"A signpost, however clear, upon the road to the patentee's invention will not suffice.
"The prior inventor must be clearly shown to have planted his flag at the precise destination before the patentee."
Jacob J reinforced the need to have "clear and unambiguous instructions to do something within the claim" in Hoechst Celanese Corp v BP Chemicals Ltd  FSR 586. In BSH Industries Ltd's Patents  RPC 183 Aldous J was minded to come to a conclusion as to what a drawing in some prior art showed, but considered that that conclusion was not sufficiently clear to amount to clear and unmistakable directions, and that therefore the prior art did not anticipate.
"1. A deviation from uniformity in physical properties; a perturbation from a normal, uniform, or predictable field. 2. Observed minus theoretical value. 3. A portion of a geophysical survey, such as magnetic or gravitational, that is different in appearance from the survey in general. 4. A gravity measurement that differs from the value predicted by some model, e.g., a Bouguer or free- air anomaly (q.v.). 5. In seismic usage, generally synonymous with structure. Also used for unexplained seismic events. 6. A deviation that is of exploration interest; a feature that may be associated with petroleum accumulation or mineral deposits …"
"… If electrodes 33 and 34 are separated by a first distance … then for direct detection of buried resistive layer 35 …
"From analysis of variations or 'anomalies' in the phase and amplitude of such complex mutual impedance signal the presence of a buried resistive layer … may be determined."
There are other references to determining the depth, but the patent as a whole is not devoted solely to that issue. I find that it is not so devoted. It purports to deal with both depth and presence.
Hördt & Strack
"A surface method which supplements seismics by providing information concerning porosity, permeability and possibly the actual fluid in order to be able to interpolate with greater reliability between the wells is desirable. Electromagnetic methods suggest themselves here. These measure electric conductivity, which depends precisely on the important parameters porosity, permeability and conductivity of the fluid.
"The long-offset transient electromagnetics (LOTEM) method suggests itself for use in reservoir surveying as penetration depths of up to several kilometres can be achieved with this method… Hitherto it has been used inter alia for crustal studies…and used in hydrocarbon exploration…Compared with other electromagnetic methods, the LOTEM method has the advantage that an earthed electric bipole is used as transmitter. Good resolution even of poorly conductive layers is therefore possible through the measurement of electric fields. This is particularly important because hydrocarbons are generally poor conductors…
"The aim of this paper is to show that there are cases where the LOTEM method can serve as an important aid to characterisation.
"The LOTEM method
"LOTEM is a transient electromagnetic depth-sounding method which uses a horizontal electric bipole as transmitter….A direct current of ca 30 amperes is fed through [a] cable into the ground which has its polarity reversed at regular time intervals…every switching event produces induction currents in the subsurface, which spread sideways and downwards in time. The form of the propagation depends on the conductivity structure of the sub-surface. Expressed in simplified terms, a high conductivity produces a low velocity of propagation and vice versa".
"An important property of the LOTEM method is the possibility of the resolution of thin, poorly conductive layers. This is made possible by the direct supply of a current into the earth, as vertical currents are also produced in the sub-surface. By contrast, in the case of methods which use a loop as a transmitter, only horizontal currents are induced…Horizontal currents penetrate thin, poorly conductive layers while vertical currents are blocked, with the result that charge accumulations form. These can in turn be interpreted by measuring the electric fields".
"The interval velocity of the P-waves decreases as the porosity increases, regardless of the pore liquid. The conductivity depends on the fluid. For salt water, it increases with the porosity, said increase being not just but of a higher order [sic]. Hydrocarbons are poor conductors, for which reason the conductivity decreases here as the porosity increases. If the porosities are therefore successfully determined with seismics, electromagnetics help with a direct recognition of hydrocarbons".
i) It is a land-based system.
ii) It is a transient-based system, whereas the 019 patent is frequency based.
iii) There is no indication that it exploits the refracted wave.
iv) The importance of using in-line orientation is not taught or appreciated.
"Given that the distances and the geometry of the reservoir will be known from previous seismic surveys, an optimum λ and l would be selected."
This envisages a process of choice for the purposes of the integer, not an indication of how to extract information from results. Again, paragraphs 18 and 19, which refer to the advantages and disadvantages of short and long wavelengths, indicate that there will be a choice of wavelength in order to achieve a useful result, which again supports the idea that integer 10 is a limitation and not just an observation.
"The fact that they are able to detect a buried thin layer inevitably means that there is a refracted wave present or you would not be able to do it. Just because they do not use that term does not mean that the physics is not there."
But again that misses the point. The point, on anticipation, is whether or not the document discloses the refracted wave. The form of that disclosure does not matter. If it had done so by a different metaphor, or in some more scientific terms, it would have disclosed it. However, it is not disclosed merely because it is there as a matter of physics. If that were not the case then the whole of the invention would be disclosed by anything which described a conventional CSEM survey, because the refracted wave (and, incidentally, all wavelengths within integer 10) would be disclosed because they exist as a matter of physics. In fact, a very large number of other principles or features of physics would be disclosed, because it is impossible to conduct a physical activity without complying with the laws of physics. But that is not what anticipation, in the realms of patent law, is concerned with. It is concerned with clear and unmistakable directions to do something. Hördt & Strack does not do that in relation to the refracted wave.
"The assessment of off-shore methane hydrate is relevant because the deposits are expected to become a very important natural energy resource…."
Under the problem of "assessment", she says:
"It is difficult to assess the total mass of hydrates from conventional geophysical remote sensing. While the base of hydrate deposits stands out clearly on seismic sections as the Bottom Simulating Reflector (BSR), the diffuse upper boundary is not well delineated.
"Our group is developing a number of complementary geophysical techniques, one of which, the use of an electromagnetic method, is described here."
"Marine sediment conducts electrical current ionically through saline fluid present in interconnected pores and fractures. Methane hydrate, like ice, is electrically insulating. Deposits of hydrate in sediment replace the conductive pore water, restrict the flow of electric current and thereby increase the bulk resistivity of the rock. Refraction electromagnetic data are obtained by measuring the analogue of the time taken for an electrical disturbance generated in a sea floor transmitter to diffuse through the sediment to a sea floor receiver (Edwards 1997). The travel time is related linearly to the resistivity: the higher the resistivity the shorter the travel time. The analog used is the phase difference between the transmitted and received signals viewed as a function of frequency. In simple terms, a linear variation in phase difference with frequency between the transmitted and received signals corresponds with a simple time delay and may be converted to an apparent resistivity."
"The amount of hydrate present can be directly related to conductivity."
"Using this scheme we inverted all data in frequency domain with half space models."
"A plot of the difference in phase measured at a given site and the phase of the signal in the water column against corresponding theoretical models having a variable sea floor conductivity."
"1. We have designed and constructed a marine sea floor transient electric dipole-dipole apparatus suitable for assessing offshore methane hydrate.
"2. The apparatus has been tested successfully over known hydrate deposits west of Vancouver Island.
"3. Estimates of apparent electrical resistivity of the sea floor have been obtained with an experimental accuracy of better than one per cent for a wide range of transmitter-receiver separation using a differential phase analysis method.
"4. Preliminary results reveal that the resistivity of the sea floor is remarkably uniform at about 1.15 ohm.metres to a depth of in excess of 100 metres. There is some evidence for higher resistivity values near [a relevant site] which may indicate the presence of hydrate."
"A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids. Sedimentary rocks are the most common reservoir rocks because they have more porosity than most igneous and metamorphic rocks and form under temperature conditions at which hydrocarbons can be preserved. A reservoir is a critical component of a complete petroleum system."
This is said to be an appropriate meaning in the context in which the word appears in the patent in suit. Emphasis is placed on the reference to "fluids". Methane hydrate is a solid, and what is more the evidence showed that it was not always contained in anything which might be called a reservoir - it can be found simply lying on the ocean floor. Therefore a layer of methane hydrate is not a reservoir. Professor Landro agreed with the definition but said that in his view an oil exploration expert would not call a hydrate layer a reservoir, "because it is not producible". He went on:
"Maybe in 20 years from now, I do not know, if technology has advanced, that we will include it as a reservoir; but presently I would not consider it as a reservoir. But I see your point that reading this [viz the Schlumberger glossary], you can end on both interpretations, I think."
"I would describe this experiment as being an inconclusive experiment" (Day 8 pp1107-8); and
"It is a preliminary - how to say, it is reporting the first attempt at doing this. It is not the final attempt." (Day 8 pp 1112-3)
He also pointed out that Yuan sought to measure a model with a buried layer, but failed to do so (Day 8 p 1111). All that lacks the flag-planting clarity required for anticipation.
The 887 Patent
"In particular, the propagation losses in hydrocarbon stratum are much lower than in a water-bearing stratum while the speed of propagation is much higher. Thus, when an oil-bearing reservoir is present, and an electromagnetic field is applied, a strong and rapidly propagated refracted wave can be detected. This may therefore indicate the presence of the reservoir or its nature if its presence is already known."
This is setting out the characteristics of the physics underlying the 019 patent.
"0015 Due to the different electromagnetic properties of a gas/oil bearing formation and a water bearing formation, one can expect a reflection and refraction of the transmitted field at the boundary of a gas/oil bearing formation. However, the similarity between the properties of the over-burden and a reservoir containing water means that no reflection or refraction is likely to occur."
"Depending on the angle of incidence and state of polarisation, an electromagnetic wave incident upon a high resistive layer may excite a ducted (guided) wave mode in the layer. The ducted mode is propagated laterally along the layer and leaks energy back to the overburden and receivers positioned on the sea floor. The term 'refracted' wave in this specification is intended to refer to this wave mode."
"0017 Both theory and laboratory experiments show that the ducted mode is excited only for an incident wave with transverse magnetic (TM) polarisation (magnetic field perpendicular to the plane of incidence) and at angles of incidence close to the Brewster angle and the critical angle (the angle of total reflection). For transverse electric (TE) polarisation (electric field perpendicular to the plane of incidence) the ducted mode will not be excited. Since the induced current is proportional to the electric field, the current will be parallel to the layer interfaces for TE polarisation but, for TM polarisation, there is an appreciable current across the layer interfaces.
"0018 A horizontal dipole source on the sea floor will generate both TE and TM waves, but by varying the orientation of the receiver antennae, it is possible to vary the sensitivity to the two modes of polarisation. It appears that an in-line orientation (source and receiver dipoles in-line) is more sensitive to the TM mode of polarisation, whereas a parallel orientation (source and receiver dipoles in parallel) is more sensitive to the TE mode of polarisation. The TM mode is influenced by the presence of buried high resistive layers, whereas the TE mode is not. By measuring with the two antenna configurations and exploiting the difference between the two sets of measurements, it is possible to identify deeply buried high resistivity zones, i.e. a hydrocarbon reservoir."
"The present invention has arisen from this realisation and comprises methods as set forth in the independent claims 1 and 2."
There are then set out the equivalent of claims 1 and 2, which appear in Appendix 4 to this judgment. The difference between the two is that the ducted wave referred to in the latter claim is to be one which has been "caused by a high resistivity zone". Paragraphs 0022 and 0023 elaborate on this:
"The first mode may be considered to be a TM mode, and the second mode a TE mode.
"0023 Thus, according to the invention, measurements are taken with the transmitter and receiver both in-line and parallel and the two sets of measurements are compared. A characteristic difference in values indicates a highly resistive layer located beneath highly conductive strata. High resistivity indicates the presence of hydrocarbons and so the difference in values is a direct hydrocarbon indicator."
The inventive step
The attack on the patent
The skilled addressee
The prior art
"The most intriguing feature in the data is the large difference in amplitude between fields transmitted along and across the AVR axis. A significant zone of low-resistivity material is required at approximately 2 kilometres depth beneath the ridge crest in order to explain this difference. It is coincident with the low-velocity zone required by the seismic data and has a total electrical conductance in excellent agreement with the results of the magnetotelluric study. The low-resistivity zone can be explained by the presence of a body of partially molten basalt in the crust."
"The electrical resistivity of solid, dry basalt exceeds that of molten basalt or seawater by orders of magnitude, so seawater penetration into cracks, the presence of hydrothermal systems, or the presence of melt will all decrease crustal resistivity. Electrical exploration methods, sensitive to these resistivity variations, thus provide information on the amount, distribution and temperature of fluid present, all of which are important parameters in understanding the processes occurring at mid-ocean ridges.
"Controlled-source electromagnetic (CSEM) methods utilise time-varying electric and magnetic fields from an artificial source. At frequencies sufficiently high that electromagnetic fields are attenuated rapidly in the seawater, energy detected by a receiver remote from the transmitter follows diffusion paths through the crust, and is therefore sensitive to its resistivity structure…..
"Several CSEM experiments using a horizontal electric dipole source operated in the frequency domain have been performed to study the resistivity structure of normal oceanic crust…. Evidence against the presence of a low-resistivity anomaly in the crusts led to the conclusion that any melt present must be in the form of small isolated pockets, suggesting that at 13 degrees north the East Pacific Rise is in a state of magmatic quiescence compared with other parts of the ridge."
"The noticeable feature of the off-axis data is the large difference in amplitude between the 0.75 Hz data recorded by [the receiver in a tow recording broadside mode] and the 0.35 Hz data recorded by the same instrument during [an in-line tow].
"….The large difference in amplitude between these two groups of data can be explained by the geometrical effect on the response of buried conductive layers. The magnitude of the radial fields is increased by the presence of buried conductive layers, an effect described in terms of galvanic current channelling by Unsworth (1991) or a lithospheric wave guide by Chave, Flosadóttir & Cox (1990). In contrast, azimuthal fields are more strongly affected by the attenuative effects of a conductive layer. If there is any increase in the field magnitude, it is much less than that observed in the radial component. This results in a distinctive radial/azimuthal field split."
"The resistivity structure to a depth of one kilometre on the axis of the AVR is constrained by the on-axis data recorded by [a particular receiver] during the first tow. Below this, the resistivity must be increased to fit the off-axis data (the 40 Ωm zone in the model)."
"Controlled source electromagnetic sounding can provide useful constraints on submarine geological structures that are overlain by significant thicknesses of basalt lava flows or sills. Experience of conducting and interpreting the CSEM surveys over oceanic lithosphere has led to the development of viable instrumentation and survey methodologies for such applications. Even in the case of a layered earth, the CSEM response of a structure depends strongly on receiver locations relative to the orientation of the source dipole. Particularly in situations where the target structure is likely to include conductive structures overlain by more resistive layers, it is essential to collect data along more than one receiver azimuth. A 1-D modelling and inversion study shows that a CSEM survey that could be readily undertaken within the limits of current technology could reliably detect sediments beneath two kilometres of basalts, and could provide useful constraints on sediment resistivities and on the depths of their upper and lower boundaries."
"Such studies have driven the development of practical methodologies for data acquisition and analysis, suitable for application to studies of relatively conductive geological targets underlying thicknesses of 1-3 kms of basalt and in water depths of 1.5 kms or more.
"One consideration that makes electromagnetic techniques potentially attractive for studying sub-basalt structures is that the sequences of basaltic sills or lavaflows tend to have high electrical resistivities. This property means that electromagnetic signals can propagate through them with relatively little attenuation. The result is that these structures – which are commonly distressingly opaque to seismic waves – can act as electromagnetically transparent windows to the underlying structure in electromagnetic surveys."
"Hence by determining signal amplitude and phase for a large number of source and receiver positions, corresponding to many different propagation paths through the sea floor, it is in principle possible to determine the resistivity structure beneath the survey by the application of suitable modelling and geophysical inversion techniques."
"However, for vertical current loops, the situation is more complex. The current loops themselves cross boundaries between layers, transferring charge vertically through the structure by means of galvanic coupling. Away from the plane through the dipole itself, vertical current loops are coupled to each other inductively. Thus both galvanic and inductive effects are occurring in this mode.
"Since a horizontal dipole source generates both of the above modes, the response can in general include both galvanic and inductive contributions. The extent to which each affects the response depends on the receiver azimuth. For a receiver azimuth of 90 degrees – i.e. a receiver placed along a direction orthogonal to the dipole axis – the observed field is dominated by horizontal current loops generated at the transmitter. The result is that the coupling between the source field at the sea floor and the currents flowing beneath the sea floor is dominantly inductive. Hence higher resistivities lead to larger amplitudes and smaller phase delays, while lower resistivities lead to smaller amplitudes and larger phase delays… The largest signals are those that have propagated along the most resistive paths – making any data collected using this geometry particularly sensitive to the more resistive parts of the underlying resistivity structure. It is this feature of the CSEM response that has led to the common assertion that 'controlled source EM is sensitive to resistive structures'.
"However, for a receiver placed along the direction of the source dipole axis – i.e. an azimuth of 0 degrees – both horizontal and vertical current loops contribute significantly to the response. Since the vertical current loops include an element of galvanic coupling between layers, the result is that buried conductive layers can lead to an increase in the total current flowing in themselves and hence in the layers above and below them.
"The extra current leads to larger electric fields in these layers. Thus for this configuration, a buried conductive layer can actually increase, rather than decrease, the amplitudes of fields at the sea floor."
"[in the broadside configuration] inductive effects dominate, and the presence of the more conductive lower layer leads to reduced amplitudes at ranges comparable to, or greater than, the thickness of the upper layer… however for an azimuth of 0 degrees, both inductive and galvanic effects occur. This leads first to an increase in amplitude at moderate ranges, and ultimately to a decrease at larger ranges. This increase in amplitudes along the transmitting dipole axis due to buried conductive structure has been described by various authors as 'a wave guide effect'….or as 'current channelling'… The important point, though, is that the interplay between inductive and galvanic effects means that the data from a CSEM survey will show extremely different patterns from source azimuths of 0 degrees and 90 degrees. Specifically, buried conductive layers lead to a 'splitting' of amplitudes for the two geometries at particular ranges with the observed amplitudes along the 0 degrees azimuth significantly exceeding the amplitudes along the 90 degrees azimuth. The consequence is that, provided data are collected at both (or all) azimuths, CSEM surveys are extremely sensitive to the presence of buried conductive layers".
"A simple model study based on the principles outlined above, that investigates the resolving power of a realistic EM survey in the case of a region of conductive sediments sandwiched between an overlying layer of resistive basalt lava flows and an underlying resistive basement."
In terms of the sort of sandwich referred to before, this is a relatively conductive layer between two more resistive layers. He creates a model of data, introduces noise, and then carries out an inversion. He concludes:
"Thus, based on a 1-D modelling and inversion approach and a realistically achievable data set, this study shows that a CSEM survey would be expected to provide very clear evidence of the presence of conductive sediments between a thick basalt sequence, and of the presence of an underlying resistive basement below the sediments. It would also provide reasonable estimates (~±30%) of the resistivities within both the basalts and the sediments. Although the inverted structure contains no sharp boundaries, it would set
useful limits (~±300 metres on the depths of the top and bottom boundaries of the sediments)."
"Controlled source electromagnetic sounding represents a viable method for obtaining sub-seafloor structural information to depths of several kilometres, and in the presence of thick basalt sequences. Since the target – sub-basalt sediments – is likely to represent a relatively conductive sequence underlying a more resistive overburden, it is essential to use a survey geometry that incorporates receivers placed both along and orthogonal to the axis of the transmitting dipole….
"A simple one-dimensional model study shows that a CSEM survey that could be readily undertaken within the limits of current technology could reliably detect sediments beneath two kilometres of basalts, and could provide useful constraints on the sediment resistivities and on the depths of their upper and lower boundaries."
"Q. This is a practical description of a survey carried out on the mid-ocean ridge with no prospect whatever of finding oil reservoirs when doing it?
A. No intent of finding oil reservoirs either."
"… (3) The most striking feature of the model is the presence of a large zone of anomalously low resistivity at mid-crustal levels beneath the AVR axis... …
"(4) The resistivity of the sub-axial anomaly must be less than 2.5 Ωm in order to produce an adequate fit to the data...… Although the shape of the low-resistivity anomaly is not constrained by the CSEM data …"
The patent deals with relative resistivity. Claim 2 expressly relies on the patented technique "to determine the presence and/or nature of any high-resistivity zone". Ramesses does not profess to do that. It is differently focused and looks at higher conductivity zones. To that extent at least it does not anticipate. Claims 1 and 1A do not contain that express limitation, but it is inherent in the use of the expression "ducted wave" in those claims, because when that expression is used earlier in the patent it is done in the context of ducting in a resistive layer (see the extracts from para 0016 above). Dr Chave points out that Ramesses refers to the phenomenon of a ducted wave, using the expression "lithospheric waveguide", but it does not do so in relation to relatively resistive layers. Again, therefore, Ramesses does not anticipate. Mr Silverleaf also points out a cross-reference in the paper to a paper by Chave, Flosadottir and Cox on the split, which concerns itself with resistive layers. It is true that there is such a cross-reference, and that earlier paper does indeed consider it in that context, but that does not affect the thrust of what Ramesses seems to be discussing, with is the split in the context of investigating a relatively conductive layer.
"conductive sequence under a resistive layer …[of] basalt, which is the exact opposite of the 887 problem where you are trying to find a resistive oil layer buried amongst conductive targets"
To which he responded:
"A. The 887 is certainly a different problem, yes." (Day 8, page 1173)
That encapsulates the point. The 887 patent was addressing a different problem. That would not, of itself, prevent anticipation, but it makes anticipation much more difficult, and there is in fact nothing there to achieve it.
"The consequence is that, provided data are collected at both (or all) azimuths, CSEM surveys are extremely sensitive to the presence of buried conductive layers." (my emphasis)
The result is that the emphasis on looking for or detecting conductive layers, which was seen in Ramesses, is continued. Professor Schultz thinks that Sinha has got things a bit back to front in his description of the physics. He thinks that the correct exposition is that the inline response would be more sensitive to the resistive, rather than more conductive, layers, and that Professor Sinha has got this the wrong way round in his paper. Dr Chave disagreed. I tend to think, after extensive debate, that Professor Schultz is right about this, but that does not matter for present purposes. What matters is that Prof Sinha is, on the face of the paper, apparently concentrating on the effects of conductive layers, not resistive layers, contrary to the thrust of the 887 patent. To that extent, and for that reason, thus far it does not anticipate. What is important is what he says, not what he might have meant had he not, arguably, got the physics (or his expression of it) the wrong way round. If an aspect of a piece of prior art contains a slip or mistake which would be obvious to the skilled addressee, then it would be proper to read the prior art as if the slip were corrected. However, that is not the case here. There is no obvious mistake which can be thus corrected. The paper should be taken to mean what it says. It is talking about conductivity not resistivity.
"a region of conductive sediments sandwiched between an overlying layer of resistive basalt lave flows and an underlying resistive basement".
In other words, a conductive sandwich not a resistive sandwich, which is the converse of the sandwich which is contemplated by the 887 patent. The result of his model is to show:
"… very clearly the presence of a substantial conductive region beneath the basalts, and also shows an indication of the presence of the resistive basement." (again, my emphasis)
This is not the model of the 887 patent. Nor is there any reference to ducted waves being detected having passed along a resistive layer. The whole purpose of this experiment is to rely on the fact that the basalt is relatively resistive, so that the fields can, as it were, get through to the conductive layer beneath. That is not the language or concept of the 887 patent.
"in an effort to try to understand something about the resistivity of the sediments and something about their thickness". (Day 10 page 1590)
He also recognized that this effort would be of interest to oil companies. He did not accept that the Sinha paper was a deployment or description of EMGS's Seabed Logging process, and I think he was right about that, since the actual technique described was different. However, I think that his answers referred to above, and the rest of his evidence, were consistent with Dr Chave's evidence that what was being mapped was areas by reference to resistivity. I find that while the focus of the two papers (and particularly Ramesses) was on relative conductivity, the techniques involved, or resulted in, a mapping of the structure, including layers of relative resistivity. That is built into the physics, as Dr Chave would say, and is demonstrated by the fact that in Ramesses the authors had to map in a relatively resistive layer (or 2 dimensional shape) in order to produce a model that coincided with the data. They were not looking for that layer/shape, but it arose from the mapping. There was considerable debate in the cross-examination of Professor Schultz about the modelling process that resulted in this, and the fact that this layer was introduced as a result of 2D modelling which was different from the 1D modelling process, or 1D study, which the 887 patent envisages. The Ramesses study, in the view of Professor Schultz, was complicated by the fact that there were long tow lines which would involve the EM signals being affected as the tow crossed the vertical edges of the structures underneath. That, he said, meant that the physics was different from that involved in the 887 patent, which did not involve vertical edges. I am prepared to accept that he was correct about that, and that that introduces a complicating factor which is not present in the 887 patent. Nevertheless, the material in that paper, particularly when combined with Sinha, was such that it was obvious to take the studies of relative conductivity, carried out by passing signals through layers of resistivity, and apply it to map layers of relative resistivity (which is inherent in the process anyway), and apply that to the search for hydrocarbons (to which Sinha makes express reference). Accordingly, taking that scientific evidence by itself, I would conclude that the invention is rendered obvious by it. The inventive step (applying the split to the search for resistive layers, and resistive layers containing hydrocarbon) would be one that the skilled person would see as obvious.
"This approach is now applied to the case of surveying for thin hydrocarbon reservoirs."
The 640 patent
"It is an object of the present invention to provide a method and apparatus for reliably locating and identifying submarine reservoirs, in particular, hydrocarbon reservoirs, but at a reduced cost and with reduced operational requirements."
"Seismic surveying techniques, however, can detect the boundaries of subterranean strata with some accuracy, but cannot readily identify the nature of the strata located. Thus by using both techniques, the results can be combined and potential hydrocarbon-bearing reservoirs can be identified with greater certainty."
"Preferably, the receiver antenna and seismic receiver are mounted on the same structure and the EM field and the seismic event are applied simultaneously. Alternatively, the EM field and seismic event are applied closely sequentially, for example five to 25 seconds.
"In a preferred system, the EM wave field response and/or the seismic response is analysed to identify the respective refracted wave component. Then, the two refracted wave components are used to determine the presence and nature of the strata. Preferably, the system additionally includes extracting and using phase and/or amplitude information from the responses, more preferably from the refracted wave responses. Preferably, the reflected wave is also identified in the seismic response, and the reflected wave component is also used to identify subterranean strata."
"The electromagnetic signals are sensitive to the electrical resistivity of subterranean layers and, therefore, electromagnetic methods are well suited for the detection of high resistive layers such as H/C reservoirs. However, layers without hydrocarbons may also have high electrical resistivities, e.g. layers consisting of salt, basalt, calcite strings or other dense rocks with low porosities and low water content. High-resistive layers of this type will generally have higher seismic velocities than the low-resistive overburden, whereas high-resistive H/C reservoirs generally have lower seismic velocities than the low-resistive overburden. Seismic methods can therefore be used to distinguish high resistive H/C reservoirs from other high-resistive layers.
"A distinction between H/C reservoirs and other high-resistive layers can be made on the basis of available seismic reflection data for the prospect in question. However, a more reliable distinction will be obtained from seismic refraction data recorded with large offsets between the seismic source and the seismic receiver. This can preferably be carried out in combination with the electromagnetic data collection….
"It will be appreciated that the absence of any refracted wave component in either the EM wave field response or the seismic response will indicate no formations with a differing resistivity or differing acoustic properties present. The presence of a refracted wave component in both the EM field response and the seismic response will indicate the presence of a formation with high resistivity and high acoustic velocity (low porosity) which would suggest e.g. basalt or a salt dome. The presence of a refracted EM wave component and the absence of a refracted seismic wave component will indicate high resistivity together with low acoustic velocity and so low porosity, which would suggest an H/C (hydrocarbon) reservoir in perhaps a porous rock formation such as sandstone."
"and where that survey reveals the presence of a subterranean reservoir, subsequently performing a method as described above [i.e. a CSEM survey]"
"It would have been obvious to the skilled addressee that he/she should approach the task of designing the seismic and CSEM surveys with a view to obtaining the best set of information on the area being surveyed in the light of cost and logistical constraints. It would have been obvious to the skilled addressee that the EM and seismic surveys could be carried out simultaneously, or closely sequentially, and with the equipment and method of analysis described in the 640 Patent. That is what the skilled addressee would have done if he/she considered that it would give the best results depending on the geological and other conditions."
"... the idea of combining seismic refraction and CSEM, or in fact any other particular kind of seismic information, is something that the skilled addressee would normally do. He would normally take whatever, and collect whatever useful information you could, and the issue of whether you would collocate sources and/or receivers would be made on a variety of grounds. Whether the physics allows it would be one of them. It would not necessarily be something that you would feel you have to do. It would be something that you might or might not do.
"... it may very well be that combining the logistics does not gain you anything. That would have to be decided on a case by case basis.
"[the statement that you would approach the task of designing seismic and CSEM surveys with a view to obtaining the best set of information] would apply independent of whether it is refraction or any other kind of seismics, you want the best set of information and you are going to do that in the light of cost and logistical constraints ... The idea of combining CSEM with seismic refraction or any other kind of seismics would be well within the normal working practices of the skilled addressee."
i) "Magmatic processes at slow spreading ridges: implications of the RAMESSES experiment at 57º 45'N on the Mid-Atlantic Ridge", by Sinha, Constable, Peirce, White, Heinson, MacGregor and Navin
ii) "The RAMESSES experiment – II: Evidence for accumulated melt beneath a slow spreading ridge from wide-angle refraction and multichannel reflection seismic profiles" by Navin, Peirce and Sinha
iii) Ramesses III – the Ramesses paper which is prior art to the 887 patent.
"A mere placing side-by-side of old integers so that each performs its own proper function independently of any of the others is not a patentable in combination, but that where the old integers when placed together have some working inter-relation producing a new or improved result then there is patentable subject-matter in the idea of the working interrelation brought about by the collocation of the integers."
"The invention claimed must normally be considered as a whole. When a claim consists of a 'combination of features', it is not correct to argue that the separate features of the combination taken by themselves are known or obvious and that 'therefore' the whole subject-matter claimed is obvious. However, where the claim is merely an "aggregation or juxtaposition of features" and not a true combination, it is enough to show that the individual features are obvious to prove that the aggregation of features does not involve an inventive step. A set of technical features is regarded as a combination of features if the functional interaction between the features achieves a combined technical effect which is different from, e.g. greater than, the sum of the technical effects of the individual features. In other words, the interactions of the individual features must produce a synergistic effect. If no synergistic effect exists, there is no more than a mere aggregation of features ..."
"If the two integers interact upon each other, if there is synergy between them, they constitute a single invention having a combined effect and one applies s3 to the idea of combining them. If each integer "performs its own proper function independently of any of the others", then each is for the purposes of s3 a separate invention and it has to be applied to each one separately."
1. A method of performing a survey of subterranean strata in order to search for a hydrocarbon containing submarine
subterraneanreservoir (35), or to determining [sic] the nature of a submarine or subterraneanreservoir (35) whose approximate geometry and location are known, which comprises: applying a time varying electromagnetic field to the subterranean strata; detecting the electromagnetic wave field response; seeking, in the wave field response, a component representing a refracted wave (43,43C); and determining the presence and/or nature of any reservoir (35) identified based on the presence or absence of a refracted wave component (43,43C); in which the transmitted field is in the form of a wave, and in which the distance between the transmitter (37) and a receiver (38) is given by the formula
0.5 λ ≤ L ≤ 10 λ ;
where λ is the wavelength of the transmission through the overburden (34) and l is the distance between the transmitter (37) and the receiver (38).
Claim 1A is like claim 1 above, but with additional differences indicated below:
1A. A method of performing a survey of subterranean strata in order to
search for a hydrocarbon containing submarine reservoir (35), or to determining the nature ofdetermine whether a submarine reservoir (35), whose approximate geometry and location are known, contains hydrocarbons or water, which method comprises: applying a time varying electromagnetic field to the subterranean strata; detecting the electromagnetic wave field response; seeking, in the wave field response, a component representing a refracted wave (43,43C); and determining the presence and/or nature of any reservoir (35) identifiedwhether the reservoir (35) contains hydrocarbons or water based on the presence or absence of a refracted wave component (43,43C); in which the transmitted field is in the form of a wave, and in which the distance between the transmitter (37) and a receiver (38) is given by the formula ... [etc]
The other relevant claims are the following:
1B. A method as claimed in Claim 1 or Claim 1A, in which the electromagnetic field
applied is a coherent continuous wave.
1C. A method as claimed in Claim 1B, in which the electromagnetic field is applied with stepped frequencies.
2. A method as claimed in Claim 1, or Claim 1A, Claim 1B or Claim 1C, characterised by the further step of analyzing the effects on any detected refracted wave component (43C) that have been caused by the reservoir (35) in order to determine further the content of the reservoir (35) based on the analysis.
11. A method as claimed in any preceding Claim, characterised in that the wavelength of the transmission is given by the formula
0.1s ≤ λ ≤ 10s;
where λ is the wavelength of the transmission through the overburden (34) and s is the distance from the seabed (33) to the reservoir (35).
16. A method as claimed in any of Claims 11 to 15, characterised by suppressing the direct wave (41), thereby reducing the required dynamic range of the receivers (38) and
increasing the resolution of the refracted wave (43, 43C).
Integers of claim 1
(1) A method of performing a survey of subterranean strata
(2) in order to search for a hydrocarbon containing
(3) submarine reservoir (35),
(4) or to determining [sic] the nature of a submarine reservoir (35) whose approximate
geometry and location are known,
(5) which comprises: applying a time varying electromagnetic field to the subterranean
(6) detecting the electromagnetic wave field response;
(7) seeking, in the wave field response, a component representing a refracted wave
(8) and determining the presence and/or nature of any reservoir (35) identified based on the presence or absence of a refracted wave component (43,43C);
(9) in which the transmitted field is in the form of a wave,
(10) and in which the distance between the transmitter (37) and a receiver (38) is given by the formula
0.5 λ ≤ L ≤ 10 λ ;
where λ is the wavelength of the transmission through the overburden (34) and L is the
distance between the transmitter (37) and the receiver (38).
[Note: capital L used for legibility: original uses lower-case l].
EP (UK) 1,309,887
0.1s ≤ λ ≤ 10s;
wherein λ is the wavelength of the transmission through the overburden and s is the distance from the seabed (33) to the reservoir.
0.5s ≤ λ ≤ 5s;
wherein λ is the wavelength of the transmission through the overburden and L is the distance between the transmitter (34) and the receiver (35).
14A method of surveying subterranean measures which comprises: performing a seismic survey to determine the geological structure of a region and where that survey reveals the presence of a subterranean reservoir, subsequently performing a method as claimed in any preceding Claim.
GB 2,399,640 AMENDED CLAIMS
1 A method of producing a survey report of subterranean strata to determine whether a reservoir containing hydrocarbons or water is present therein and to determine whether the reservoir contains hydrocarbons or water, which method comprises: deploying an electromagnetic(EM) field transmitter; deploying a seismic source at substantially the same location as the EM field transmitter,; deploying an EM field receiver at a predetermined offset distance from the transmitter; deploying a seismic receiver at substantially the same location as the EM field receiver; applying an EM field to the strata using the EM field transmitter; detecting the EM wave field response using the EM field receiver; applying a seismic event to the strata using the seismic source at substantially the same location as the EM field transmitter; detecting the seismic response using the seismic receiver at substantially the same location as the EM field receiver; analysing the EM wave field response; analysing the seismic response; identifying the refracted wave component of the EM wave field response; identifying the refracted wave component of the seismic response; and reconciling the two responses using the two refracted wave components in order to produce a report on the presence and nature of the strata.
2 A method as claimed in Claim 1, which additionally includes extracting and using phase and/or amplitude information from the responses.
A method as claimed in any preceding Claim, which includes identifying the refracted wave component of the EM wave field response, identifying the refracted wave component of the seismic response, and using the two refracted wave components to produce the survey report. (Deleted)
4 A method as claimed in
Claim 3 any preceding Claim, in which phase and/or amplitude information from the two refracted wave components is used.
5 A method as claimed in any preceding Claim, in which the EM field transmitter, the seismic source and the two receivers are all in the same plane.
6 A method as claimed in any preceding Claim, in which the EM field transmitter comprises an electric dipole antenna.
7 A method as claimed in any preceding Claim, in which the EM field receiver comprises an electric dipole antenna.
8 A method as claimed in any preceding Claim, in which the EM field receiver and the seismic receiver are mounted on the same structure.
9 A method as claimed in any preceding Claim, in which the EM field and the seismic event are applied simultaneously.
10 A method as claimed in any of Claims 1 to 88, in which the EM field and the seismic event are applied closely sequentially for example 5 to 25 seconds.
11 A method as claimed in any preceding Claim, in which the reflected wave component of the seismic response is also identified and the reflected wave component is also used to identify subterranean strata.
12 A method as claimed in any preceding Claim, which includes: additionally, deploying a magnetic receiver at substantially the same location as the EM field receiver; detecting a magnetic field response and using the magnetic field response in combination with the EM wave field response and the seismic response.
13 A method as claimed in any preceding Claim, which comprises repeating the procedure with the EM field transmitter and seismic source, and/or the EM field receiver and seismic receiver, in different locations for the plurality of EM transmissions and seismic events.
14 A method as claimed in any preceding Claim, in which the procedure is repeated at different offsets.
15A method as claimed in any preceding Claim, which includes the deployment and use of a plurality of EM field receivers and/or a plurality of seismic receivers.
16 A method as claimed in Claim 15, in which the EM field receivers and the seismic receivers are mounted on a cable.
17 A method as claimed in any preceding Claim, in which the EM field transmitter and receiver and/or the seismic source and receiver, are located on or close to the seabed or the bed of some other area of water.
18 A method as claimed in Claim 17, in which the seismic source is located at or near the surface of the area of water.
19 A method as claimed in any preceding Claim, in which the frequency of the EM field is continuously varied over the transmission period.
20 A method as claimed in any preceding Claim, in which the EM field is transmitted for a period of time for 3 seconds to 60 minutes.
21 A method as claimed in Claim 19, in which the transmission time is from 10 seconds to 5 minutes.
22 A method as claimed in any preceding Claim, in which the wavelength of the transmission is given by the formula
0.1s ≤ λ ≤ 5s;
Wherein λ is the wavelength of the transmission through the overburden and s is the distance from the seabed to the reservoir.
23 A method as claimed in any preceding Claim, in which the offset between the EM field transmitter and the EM field receiver is given by the formula:
0.5s ≤ λ ≤ 10s;
where λ is the wavelength of the transmission through the overburden and L is the distance between the transmitter and the receiver.
24 A method as claimed in any of Claims 11 to 23, in which the transmission frequency is from 0.01 Hz to 1 kHz.
25 A method as claimed in Claim 24, in which the transmission frequency is from 0.1 to 20 Hz.
26 A method as claimed in any preceding Claim, in which the seismic receiver records a full flow component seismic recording, comprising three displacement vector components and a pressure component.
27 Apparatus for use in carrying out a method as claimed in any preceding Claim, including a receiver assembly comprising: a support structure; an electric dipole receiver antenna mounted on the support structure; a three axis seismic receiver mounted on the support structure; a geophone arrangements mounted on the support structure; a hydrophone mounted on the support structure and an anchor arranged to attach the support structure to the sea bed.
28 A survey report produced by a method as claimed in any of Claims 1 to 26.