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`BEFORE THE PATENT TRIAL AND APPEAL BOARD
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`PETROLEUM GEO-SERVICES INC.
`Petitioner
`v.
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`WESTERNGECO LLC
`Patent Owner
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`CASE IPR: Unassigned
`Patent 7,162,967 B2
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`DECLARATION OF DR. BRIAN EVANS, PhD.
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`TABLE OF CONTENTS
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`INTRODUCTION ............................................................................................... 1
`I.
`II. QUALIFICATIONS ........................................................................................... 2
`III. COMPENSATION AND RELATIONSHIP TO THE PARTIES ..................... 7
`IV. LEGAL STANDARDS ....................................................................................... 8
`A. Claim Construction .......................................................................................... 8
`B. Anticipation ..................................................................................................... 8
`C. Obviousness ..................................................................................................... 9
`D. Person of Ordinary Skill in the Art .................................................................. 9
`V. SUMMARY OF OPINION .............................................................................. 10
`VI. TECHNICAL BACKGROUND ....................................................................... 11
`B. Streamer Steering Overview .......................................................................... 19
`VII. THE ’967 PATENT ....................................................................................... 41
`A. Brief Description of Relevant File History ................................................... 41
`B. Relevant Time Frame for Analysis of the ’967 Patent .................................. 43
`C. The Specification of the ’967 Patent ............................................................. 43
`D. The Challenged Claims – Claims 1 and 15 of the ’967 Patent...................... 45
`VIII. Construction of Relevant Claim Terms ......................................................... 46
`A. Streamer positioning device: “a device that controls the position of a
`streamer as it is towed (e.g., a ‘bird’)” ................................................................. 47
`B. Location information: “Information regarding location” ............................. 49
`C. Global control system: “a control system that sends commands to other
`devices in a system (e.g., local control systems)” ................................................ 49
`D. Local control system: “a control system located on or near the streamer
`positioning devices (e.g., birds)” .......................................................................... 51
`E. On or in-line with: “either in-line with the streamer or attached to the
`streamer, whether fastened on the streamer by clamping or other means” .......... 52
`IX. DETAILED OPINION ...................................................................................... 53
`A. Claims 1 and 15 are Anticipated by the ’636 PCT. ....................................... 56
`B. Claims 1 and 15 are Obvious Over the ’636 PCT. ........................................ 68
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`D. Claims 1 and 15 are Obvious Over Ambs. .................................................. ..82
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`E. Claims 1 and 15 are Obvious Over Elhom in vew of the ’636 PCT. .......... ..83
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`C. Claims 1 and 15 are Anticipated by Ambs. ................................................... 70
`C. Claims 1 and 15 are Anticipated by Ambs. ................................................. ..70
`D. Claims 1 and 15 are Obvious Over Ambs. .................................................... 82
`E. Claims 1 and 15 are Obvious Over Elhom in vew of the ’636 PCT. ............ 83
`X. CONCLUSION ................................................................................................. 97
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`X. CONCLUSION ............................................................................................... ..97
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`I, Dr. Brian Evans, hereby state the following:
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`I. INTRODUCTION
`1.
`I have been retained by Petroleum Geo-Services, Inc. (“PGS”) to
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`provide technical assistance related to the filing of a Petition for Inter Partes
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`Review of U.S. Patent No. 7,162,967 B2 (“the ’967 Patent”) (Ex. 1001). I am
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`working as a private consultant on this matter and the opinions presented here are
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`my own.
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`2.
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`I have been asked to prepare a written report, including comments
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`related to whether Claims 1 and 15 of the ’967 Patent are unpatentable because
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`they are anticipated or would have been obvious to one of ordinary skill in view of
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`the prior art. I have reviewed the documents set forth in the appendix attached
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`hereto and have relied on my decades of knowledge and experience in the field of
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`seismic marine surveys (detailed in Section II) in reaching my opinions regarding
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`validity. This report sets forth the bases and reasons for my opinions, including the
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`materials and information relied upon in forming those opinions and conclusions.
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`A list of materials that I consulted in preparing this report appears in Appendix A.
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`3.
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`This report is based on information currently available to me. I reserve
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`the right to continue my investigation and analysis, which may include a review of
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`documents and information not yet produced. I further reserve the right to expand
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`or otherwise modify my opinions and conclusions as my investigation and study
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`continues, and to supplement my opinions and conclusions in response to any
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`additional information that becomes available to me.
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`II. QUALIFICATIONS
`4.
`I am a Professor of Geophysics in the Department of Petroleum
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`Engineering at Curtin University located in Bentley, Western Australia. I have
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`worked continuously in the field of marine seismic surveying for over 44 years,
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`since the 1970s. I have been involved in the design of dozens of marine seismic
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`surveys, and have been onboard seismic vessels as they were conducting a marine
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`seismic survey over one-hundred times.
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`5.
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`I authored a textbook devoted to marine seismic surveying and data
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`acquisition, entitled “A Handbook for Seismic Data Acquisition in Exploration.” I
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`began writing the textbook in 1985 for use in my “Seismic Acquisition” class, and
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`continued to update it over the years. It was first published in 1997 by the Society
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`of Exploration Geophysicists (SEG), the premier international organization for
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`seismic professionals and researchers, including marine seismic professionals. At
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`the time of its publication, it was considered the authoritative textbook in the field
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`of seismic data acquisition. Over the past 15 years, it has been used throughout the
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`world in seismic surveying courses and on seismic survey vessels.
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`6.
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`I obtained my Diploma of Electrical Engineering, the equivalent of a
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`bachelor’s degree, at the J.M. University of Liverpool in the United Kingdom in
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`1969. I took my first job in the marine seismic industry in 1971, working as an
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`instrument engineer for Geophysical Service, Inc. In that role, I monitored and
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`repaired the seismic recording and navigation instruments, including the equipment
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`that positioned marine seismic streamers and source arrays. As a qualified
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`electrical engineer, I also repaired electronic equipment on seismic vessels,
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`including on-board computers, and navigation/positioning systems. While with
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`Geophysical Services, Inc., I traveled the world working offshore West Africa,
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`South America, India, Vietnam, the Persian Gulf, Indonesia, the Philippines, the
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`South China Sea, and the Gulf of Thailand—all offshore oil exploration areas.
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`7.
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`After leaving Geophysical Service, Inc. in 1974, I joined Aquatronics,
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`a London-based seismic company, where I managed seismic survey ships used in
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`seismic surveys. In 1975, I joined Southern Geophysical Consultants of London as
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`a Seismic Acquisition and Surveying Consultant. In that capacity, I represented
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`many oil companies while onboard seismic survey ships to ensure the quality of
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`the acquired seismic data and that the seismic data was within the oil company’s
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`specifications. I was also involved in deep water operations and rig relocations for
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`different oil companies during my time at Aquatronics.
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`8.
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`In 1976, I established my own seismic-acquisition consulting
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`company in Perth, Australia, called “Offshore-Onshore Exploration Consultants
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`PTY LTD.” As an independent consultant, I participated in seismic surveys on
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`behalf of my oil company clients to ensure the quality of the seismic data acquired
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`and that the seismic data was within the oil company’s specifications. My
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`consulting company, which employed four other employees, was the only
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`company that did this type of work in Southeast Asia at the time. From 1980 to
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`1983, while at the peak of my consultancy operations, I also worked at Shell
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`Development Australia in Perth, Australia, as a Senior Operations Geophysicist.
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`My responsibilities at Shell Development included managing three marine-
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`seismic-survey ships and two land-seismic-survey crews.
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`9.
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`In 1983, I enrolled at Curtin University (known then as West
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`Australian Institute of Technology). From 1983 to 1985, as part of a Masters
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`program in Applied Physics, I wrote a thesis entitled “The Establishment of a
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`Digital Seismic Acquisition System and its Subsequent Application in the Field.” I
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`also designed and built a seismic recording system.
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`10. After receiving my Masters in Applied Physics in 1985, I enrolled in a
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`Geophysics Ph.D. program at Curtin University, focusing on 3D Seismic
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`Surveying Data Processing. As part of the Ph.D program, I taught seismic
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`acquisition, processing, and interpretation and lectured short-courses for industry
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`(including marine seismic companies) on conventional and 3D seismic acquisition
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`methods. While working on my Ph.D, I continued to consult on marine seismic
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`data acquisition. I also established the Department of Exploration Geophysics at
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`Curtin University. In 1997, I completed my Ph.D. program, and produced a Ph.D
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`thesis titled, “Advancements in the Techniques of Low-fold Three Dimensional
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`Seismic Reflection Surveying.”
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`11. After completing my Ph.D. in Geophysics in 1997, I continued to
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`teach seismic data acquisition, processing, and interpretation as an Associate
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`Professor at Curtin University. I also continued to teach short-courses to the
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`industry on marine seismic data acquisition. Over the years, I have supervised
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`twenty Master’s and Ph.D. students, many of whom have written theses pertinent
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`to the marine seismic industry. I continue to supervise four Ph.D. students today.
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`12.
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`I became a tenured Professor of Geophysics in 2002. I served as
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`Chair of the Department of Petroleum Engineering from 2007 to 2012. I then
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`became the Director of Curtin University’s Faculty of Science and Engineering’s
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`Oil and Gas Training and Research Project Initiatives in 2013. In that role, I
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`establish research projects with industry, establish teams to run projects, and
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`consult with industry and the research staff to ensure the projects stay on track.
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`13. Much of my research over the years has involved numerical and
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`physical modeling of the seismic data acquisition process, including in the context
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`of 3D and 4D seismic marine surveys. This has entailed both field and laboratory
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`research, in which I would frequently work onboard seismic survey ships during
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`marine seismic surveys; and later attempt to improve on marine seismic data
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`acquisition techniques by testing in the laboratory. Building on my research to
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`optimize 3D and 4D data acquisition, I have built three seismic physical
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`acquisition simulation labs in Houston, Dhahran, and Rio de Janeiro. These labs
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`involved the use of physical models to simulate 3D marine seismic surveys. The
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`Houston lab was built in 1991 and later moved and reconstructed at Curtin
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`University; the other labs were built in 2005 and are presently operated in Dhahran
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`and Rio de Janeiro. All of these labs are still in use today. I have also developed a
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`seismic numerical modeling lab at Curtin University, and a landmark seismic
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`interpretation lab, which oil companies use to train their employees and to interpret
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`3D marine seismic data.
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`14. Throughout the 1990s and 2000s, I have continued to consult in the
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`marine seismic survey field while working at Curtin University. I have consulted
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`with various marine seismic survey companies as part of my job representing oil
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`companies and in my independent consulting company. In this role, I am typically
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`asked to evaluate seismic survey plans and advise companies on their plans’
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`suitability for an optimal survey. This often requires me to determine whether the
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`seismic data acquisition and processing plans are adequate to produce quality
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`seismic data considering the survey area’s 3D geology. To fulfill this role, I
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`closely follow the literature and other available information regarding the latest
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`marine seismic acquisition technologies. I continue to do this consulting work to
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`this day. I have also consulted on a wide range of other issues relating to marine
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`seismic data acquisition, processing, and interpretation. For instance, I have had
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`an Independent Advisory Group since 2004 to review and evaluate oil companies’
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`seismic data, drilling plans and proposed operations.
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`15.
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`I am currently a member of several professional organizations related
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`to the marine seismic industry, and the oil and gas industry in general. I have been
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`a member of the Australian Society of Exploration Geophysics since 1983 and the
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`Society of Exploration Geophysicists (“SEG”)—widely recognized as the principal
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`international society in the field—since 1993. I was President of the Australian
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`state chapter of the SEG twice, in 1986 and 1993. In addition to SEG, I have also
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`been a member of the Society of Petroleum Engineers (SPE) since 1994 and the
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`Petroleum Club of Western Australia since 2009, of which I am currently a Board
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`Member. From 2006 to 2012, I was a Board Member and Education Scholarship
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`Committee Chair of the West Australian State Government Minerals and Energy
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`Research Institute (MERIWA).
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`III.
`16.
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`COMPENSATION AND RELATIONSHIP TO THE PARTIES
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`I am being compensated at an hourly rate of three hundred and fifty
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`dollars ($350), plus expenses, for the time I spend in Australia studying materials
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`associated with this matter and providing testimony, and six hundred twenty five
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`euros (€625) for the time I spend on this matter outside Australia. This is my
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`standard consulting rate. I am an independent party and my compensation is not
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`contingent upon the outcome of this matter.
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`17.
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`It is my understanding that WesternGeco L.L.C. (“WesternGeco”), is
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`the assignee of the ’967 Patent. Prior to this matter, I have not been employed or
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`retained by WesternGeco or PGS. I own no stock in WesternGeco or PGS, and am
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`aware of no other financial interest I have with those companies.
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`IV.
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`LEGAL STANDARDS
`18. Although I am not an attorney and do not expect to offer any
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`opinions regarding the law, I have been informed of certain legal principles that I
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`relied on in forming the opinions set forth in this report.
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`A. Claim Construction
`19.
`I understand that for purposes of this matter the terms in patent
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`claims are to be given their broadest reasonable interpretation in light of the
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`specification of the ’967 Patent, as understood by one of ordinary skill in the art as
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`of the priority date of the ’967 Patent.
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`B. Anticipation
`20.
`I understand that for a claim to be anticipated, a single prior art
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`reference must disclose to a person of ordinary skill in the art, either expressly or
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`inherently, each and every limitation set forth in the claim. I understand that
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`claims are unpatentable if they are anticipated by the prior art.
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`C. Obviousness
`21.
`I understand that even if a claim is not anticipated, an invention that
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`would have been obvious to a person of ordinary skill at the time of the invention
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`is not patentable. I understand that obviousness is determined by considering
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`several factors, including: the state of the art at the time the invention was made;
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`the level of ordinary skill in the art; differences between what is described in the
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`art and the claims at issue; and objective evidence of nonobviousness (such as
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`commercial success, long-felt but unsolved needs, failure of others, and
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`unexpected results). I understand that claims are unpatentable if they would have
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`been obvious in view of the prior art.
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`D.
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`Person of Ordinary Skill in the Art
`22.
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`I have been informed that a person of ordinary skill in the art is a
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`hypothetical person who is presumed to have known all of the relevant art at the
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`time of the invention. I have been informed that a person of ordinary skill in the
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`art may possess the education, skills, and experience of multiple actual people who
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`would work together as a team to solve a problem in the field. I have been
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`informed that factors that may be considered in determining the level of ordinary
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`skill in the art may include: (1) the educational level of the inventor; (2) type of
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`problems encountered in the art; (3) prior art solutions to those problems; (4)
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`rapidity with which innovations are made; (5) sophistication of the technology; and
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`(6) educational level of active workers in the field.
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`23. On the basis of my consideration of these factors and my
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`experience in solving problems in the area of marine seismic surveys for decades,
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`including my familiarity with the education, expertise, and experience of the teams
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`that devise solutions to those problems, I have been asked to opine as to the person
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`of ordinary skill in the art to which Claims 1 and 15 of the ’967 Patent are directed.
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`In my opinion, such a person of ordinary skill in the art should have a Master’s
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`degree or Ph.D. in ocean engineering, mechanical engineering, geophysics, applied
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`physics, or a related area, who has preferably taken coursework in hydrodynamics,
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`advanced control systems, and other related fields. Additionally, the person should
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`have at least three years of experience designing and/or operating marine seismic
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`surveys, as well as significant experience aboard marine seismic survey vessels
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`during the course of several marine seismic surveys.
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`V. SUMMARY OF OPINION
`24.
` It is my understanding that PGS (or “Petitioner”) requests Inter
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`Partes review of Claims 1 and 15 of the ’967 Patent, titled “Control System for
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`Positioning of Marine Seismic Streamers,” which was issued to Oyvind Hillesund
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`and Simon Hastings Bittleston on January 16, 2007, and has been assigned to
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`WesternGeco. It is my opinion that Claims 1 and 15 would have been well known
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`and obvious to a person of ordinary skill at the time of the October 1, 1998 prioirty
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`date.
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`VI.
`TECHNICAL BACKGROUND
`A. Overview of Marine Seismic Surveying
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`25. The ’967 Patent is directed to marine seismic surveying technology.
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`Marine seismic surveys use reflected sound waves to determine geological
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`properties of the earth’s subsurface. Seismic surveying ships (also known as
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`vessels) tow equipment referred to in the industry as “seismic sources” or “guns”
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`to create small, controlled explosions underwater. The explosions generate
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`acoustic sound waves that travel down through the water, penetrate the ocean floor,
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`reflect off geological formations in the earth’s subsurface, and travel back towards
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`the seismic vessel. The reflected acoustic signals are recorded by seismic receivers
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`known as “hydrophones,” which are towed behind the vessel in long cables called
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`marine seismic “streamers.” Because recorded sound waves have different
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`properties depending on the geology of the ocean’s subsurface, the acoustic signals
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`recorded by the hydrophones provide information regarding characteristics of the
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`ocean’s subsurface, including evidence about the existence of oil and gas.
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`26.
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` In modern marine seismic surveys, a towing vessel will typically tow
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`a plurality of streamers in a large areal spread known as an “array.” Each streamer
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`in the array contains groups of hydrophone located at pre-determined intervals
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`along the streamer. The acoustic data acquired by each hydrophone group is
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`recorded as a function of time and provides information about a two-dimensional
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`vertical slice of the earth’s surface below the area traversed by the streamer. By
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`towing a plurality of streamers, the seismic surveyor covers a large area and is able
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`to record reflected seismic signals at several locations simultaneously. This
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`technique results in seismic data from various locations that can be combined and
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`processed by computers to construct a three-dimensional image of the earth’s
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`subsurface.
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`27. Below is a graphical depiction of a modern marine seismic survey
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`system:
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`28. This figure depicts a survey vessel towing four streamers, each of
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`which contains hydrophones to record seismic data that reflects off the ocean’s
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`subsurface, and one air gun array (the acoustic source). This multiple-streamer
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`seismic surveying system became commonplace beginning in the late 1980s. See
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`Ex. 1032 (Brian J. Evans, A Handbook for Seismic Data Acquisition in
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`Exploration (David V. Fitterman & William H. Dragoset, Jr. eds., 1997))
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`(“Evans”) at 250.
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`29. Seismic data are recorded on a shot-by-shot basis. In a typical marine
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`seismic survey, the vessel will travel at approximately five nautical miles per hour
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`and fire a shot from one or more seismic sources approximately every ten seconds.
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`The data recorded by each hydrophone group for each seismic shot is known as a
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`“trace.” The “shot” from the seismic source emits acoustic signals (i.e., sound
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`waves) that are reflected at different points on the ocean’s subsurface. These
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`signals are received by the various hydrophones on the towed streamers, as
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`depicted below:
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`See Ex. 1032 (Evans) at 9.
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`30. For each shot or “trace,” the hydrophones record the reflected acoustic
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`signals as a function of time. Each hydrophone group occupies a different location
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`and thus, for each shot, will record different acoustic signals at different positions.
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`The recorded data from each hydrophone group for each shot are then sent from
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`the streamers back to the towing vessel via a communications line that may be
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`comprised of twisted pair cables or, in more modern implementations, fiber-optic
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`lines. This shot-by-shot process is repeated continuously during seismic surveys,
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`resulting in a vast amount of seismic data being transmitted to the vessel. The
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`seismic data acquired during a survey are maintained on the towing vessel by an
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`on-board computer or other storage device, along with data reflecting the position
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`and time the signals were received. This data can later be processed to create a
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`three dimensional image of the earth’s subsurface in the surveyed region.
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`31. Marine seismic surveys are carefully planned in advance. Marine
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`seismic survey data are acquired and organized using a process known as
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`“binning.” When designing and conducting a three-dimensional marine seismic
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`survey, the area of the ocean subsurface being surveyed is represented as a grid.
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`Each cell in the seismic survey grid is called a “bin.” In a conventional 3D marine
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`seismic survey, the survey plan calls for the streamers to traverse the survey area
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`grid in straight lines back and forth, creating parallel lines of seismic data
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`coverage. As practitioners in the marine seismic data acquisition field have long
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`recognized, one of the primary goals of 3D marine seismic data acquisition is to
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`conform the actual survey to the survey plan’s specifications, including
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`maintaining the streamers’ positions along the pre-planned designated course,
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`thereby producing the desired quality and efficiency of the survey as planned. See,
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`e.g., Ex. 1025 (U.S. Patent No. 4,033,278) (“Waters”) at 2:15-36; Ex. 1026 (U.S.
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`Patent No. 4,404,664) (“Zachariadis”) at 1:16-40; Ex. 1031 (U.S. Patent No.
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`5,790,472) (“Workman”) at 1:10-11 (“During a typical marine seismic survey a
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`seismic vessel traverses programmed tracks . . . .”).
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`32. The graphic below depicts (without the streamers, for ease of
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`understanding) a survey area divided into bins. Although their size can vary, bin
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`sides typically measure about 10-25 meters in length. See Ex. 1033 (E. J. W.
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`Jones, Marine Geophysics (1999)) at 89. Also depicted (but not to scale) is the
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`vessel conducting the survey. A typical vessel would be about 100 meters long
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`and 25-40 meters wide.
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`33. As part of the survey design process, seismic surveyors pre-determine
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`a minimum number of trace data points that they must sum together in each bin to
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`obtain the desired seismic data quality. If the surveyor does not obtain the
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`minimum data points required for a particular bin, there will be data of inadequate
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`quality or simply gaps in the survey data. The presence of inadequate data quality
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`or gaps often requires the survey ship to repeat the survey over those areas to fill
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`the bins. The process of re-acquiring seismic data, known as “in-filling,” is very
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`time-consuming and expensive. See Ex. 1032 (Evans) at 254. Gap or inadequate
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`data problems were frequently known to occur when currents cause the streamers
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`and their hydrophones to veer off course from their pre-planned paths, so that in
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`certain bins, the hydrophones do not record as many data points as planned,
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`desired, or required. Ex. 1034 (W.R. Cotton & J.I. Sanders, The Reality of Trace
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`Binning in 3-D Marine Surveying, (1983) at 565; see also, infra, at ¶¶ 44, 50, 53,
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`69, 71.
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`34.
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`In addition to ensuring that sufficient traces are recorded in each bin,
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`seismic surveyors also desire to have the data points as evenly distributed in the
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`bin as possible. Having the data points unevenly or irregularly spaced within a
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`bin—often the result of streamers (in which the hydrophones are contained)
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`veering off the planned course—creates “uneven illumination or incomplete
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`illumination of the subsurface.” See Ex. 1035 (Biondo L. Biondi, 3D Seismic
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`Imaging (2006) (“Biondi”) at 123; see also Ex. 1036 (Christopher L. Liner,
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`Elements of 3-D Seismology (1999)) (“Liner”) at 104-05; Ex. 1032 (Evans) at 238.
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`35.
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`It was well recognized before October 1, 1998 that this irregular
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`spatial sampling and resultant uneven or incomplete illumination of the subsurface
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`reduces the quality of the survey data and makes it more difficult and expensive to
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`process the data. See, e.g., Ex. 1037 (Gerald H.F. Gardner & Anat Canning, Effect
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`of irregular sampling on 3-D prestack migration, SEG Abstracts (1994)) at 1553-
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`56; Ex. 1032 (Evans) at 238. For example, where there is regular spatial sampling
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`in a survey, the individual seismic data points in adjacent bins are generally one
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`bin length apart. But, if there is irregular spatial sampling, such as where the data
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`points collect on one side of a bin and on the far opposite side of an adjacent bin, it
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`results in a substantial amount of space between seismic data points, creating large
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`gap areas with no data. On the 3D image, that area could show up having less
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`detail than the rest of the survey, thereby reducing the quality of the overall survey
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`data. See Ex. 1035 (Biondi) at 123. This problem is referred to as “spatial
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`aliasing”:
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`Spatial aliasing is an effect of [data point] spacing
`relative to frequency, velocity, and slope of a seismic
`event. With adequate [data point] spacing, the points
`along a seismic event are seen and processed as part of
`the continuous event. When [data point] spacing is too
`coarse, individual points do not seem to coalesce to a
`continuous event, which confuses not only the eye but
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`17
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`
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`processing programs as well. This can seriously degrade
`data quality and the ability to create a usable image.
`
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`Ex. 1036 (Liner) at 104.1
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`36. Irregular spatial sampling caused by irregular streamer positioning
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`also has “a detrimental effect” on data processing, thereby making it more difficult
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`and expensive to process the data. Ex. 1036 at 104-05; Ex. 1035 (Biondi) at 123-
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`24. Accordingly, though obtaining the prerequisite number of seismic traces
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`within each bin is important, that alone does not ensure adequate data quality. To
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`avoid these degradations and distortions in the data, seismic surveyors seek to
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`position streamers (and their hydrophones) to achieve regular spatial sampling in
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`bins, thereby avoiding holes or uneven distributions of seismic traces.
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`
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`1 Although Liner’s book was published in 1999, he was summarizing what was
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`previously known in the field about spatial aliasing. Indeed, Liner cited prior art
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`that describes the spatial aliasing problem. See, e.g., Ex. 1038 (Christopher L.
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`Liner & Ralph Gobeli, Bin Size and Linear v(z), Society of Exploration
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`Geophysics Technical Program Expanded Abstracts (1996)) at 47. I also wrote
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`about this problem in my book, see Evans, supra, at 238, and noted the problem in
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`my class notes in the late 1980s.
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`18
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`B. Streamer Steering Overview
`37. Effective streamer steering has long been recognized in the field to
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`provide many benefits for seismic surveys. During the seismic survey, the
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`streamers are typically intended to remain straight, parallel to each other and
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`equally spaced. Due to environmental factors such as wind and sea currents,
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`however, seismic streamers frequently bow and undulate, thereby introducing
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`deviations into this desired path and shape. As explained above, without the ability
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`to control the streamers, deviations from desired streamer positions can create gaps
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`in the seismic data coverage, reducing data quality and the efficiency of seismic
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`survey operations. See Ex. 1004 (PCT Application No. WO 98/28636) (“’’636
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`PCT”) at 2; Ex. 1031 (Workman) at 1:28-41; supra ¶¶44, 50, 53, 69, 71.
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`Therefore, an advantage of being able to steer a streamer laterally is the ability to
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`ensure that streamers remain straight and parallel, along their intended path of
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`travel, throughout the seismic survey.
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`38.
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` Streamer steering also was known to be desirable to avoid
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`accidents that could damage the survey system. If streamers veer substantially off
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`their intended course, for example due to local currents, they can become
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`entangled and thereby disabled, which creates significant expenses. The efficient
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`conduct of the survey, with minimal downtime, is essential to the profitable
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`conduct of the survey. See Ex. 1004 (’636 PCT) at 2.
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`19
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`39. The ability to control the depth of the streamers also has long been
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`recognized to be desirable. Streamers are typically towed at a constant depth of
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`approximately 10 meters. Maintaining streamers at a constant depth is important
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`because depth variations between hydrophones in a seismic array introduce
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`complications into seismic data processing. See Ex. 1007 (U.S. Patent No.
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`3,605,674) (“Weese”) at 1:41-45 (“In order that the signals received can be
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`properly and correctly interpreted, the position of the cable relative to the water
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`surface . . . must be known and maintained as uniformly as possible.”)
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`40. One of the complications resulting from deviations in streamer depth
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`is caused by a phenomenon called “ghost” reflections. When seismic sources are
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`fired, the energy reflected from geological formations travels up to the receivers
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`and is recorded; but time-delayed reflections from the sea surface create additional,
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`unwanted acoustic recordings that interfere with the acoustic signals. See Ex. 1032
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`(Evans) at 149-51. These signals reflected from the ocean surface are known as
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`“ghost” reflections or “receiver ghosts.” Id. Although these unwanted “ghost”
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`reflections are often inescapable when using conventional seismic arrays, the
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`acoustic interferences caused by the