David H. Johnston is Managing Director of Differential Seismic, LLC, a geophysics consultancy. Johnston retired from ExxonMobil in 2017 after a 38-year career in research, exploration, and production. He earned a Bachelor of Science degree in earth sciences from the Massachusetts Institute of Technology in 1973 and a Ph.D. in geophysics in 1978, also from MIT. After graduation, Johnston joined Exxon Production Research Co. (later ExxonMobil Upstream Research) and held assignments in rock physics research, velocity analysis and interpretation, and seismic reservoir characterization and monitoring. He moved to ExxonMobil Exploration Co. in 2002 where he was responsible for the worldwide application of time-lapse seismic technology. In 2008 Johnston transferred to ExxonMobil Production Co. where he provided technical and business stewardship of ExxonMobil's global production geophysics activity, including 4D seismic.
Johnston is a member of SEG, SPE, AAPG, EAGE, and AGU. He served as Secretary/Treasurer of the SEG in 1990 and has chaired the SEG Development and Production and Interpretation Committees. He was an editor of Seismic Wave Attenuation (1981), Reservoir Geophysics (1992), and Methods and Applications in Reservoir Geophysics (2010), all published by the SEG. He is an editorial board member for Interpretation, the new SEG/AAPG journal.
Johnston was awarded Best Presentation by the SEG in 1993, honorable mention for Best Presentation in 2010, and Best Paper in The Leading Edge in 2005. He was an SPE Distinguished Lecturer from 1992 to 1993, the SEG Distinguished Lecturer in 1999, and an AAPG Distinguished Lecturer in 2008. In 2003 he received Honorary Membership in the Geophysical Society of Houston and in 2004 he was awarded Life Membership in the SEG. In 2007 Johnston was the first recipient of ExxonMobil's Peter Vail award for distinguished technical achievement.
Making a Difference with 4D: Practical Applications of Time-Lapse Seismic Data
Time-lapse (4D) seismic technology is a key enabler for improved hydrocarbon recovery and more cost-effective field operations. By analyzing differences of multiple seismic surveys acquired over a producing reservoir and by integrating with conventional reservoir monitoring data, 4D seismic data provides valuable insight on dynamic reservoir properties such as fluid saturation, pressure and temperature. Changes in these reservoir properties that occur during hydrocarbon production are identified and quantified by 4D analysis and used to identify areas of bypassed and undrained pay and to improve geological and engineering models. The purpose of this course is to provide an overview of the fundamentals of 4D seismic technology, starting from its role in field lifecycle planning and then through seismic acquisition, processing, and analysis. However, a primary focus of the course is interpretation and data integration. Case study examples will be used to demonstrate key concepts and will be drawn upon to demonstrate the range of interpretation methods currently employed by the industry and the diversity of geological settings and production scenarios where 4D is making a difference.
The classical meaning of the word dispersion is frequency-dependent velocity. Here we take a more general definition that includes not just wave speed but also interference, attenuation, anisotropy, reflection characteristics, and other aspects of seismic waves that show frequency dependence. At first impression, the topic seems self-evident: Of course everything is frequency dependent. Much of classical seismology and wave theory is nondispersive: the theory of P- and S-waves, Rayleigh waves in a half-space, geometric spreading, reflection and transmission coefficients, head waves, and so forth. Yet when we look at real data, strong dispersion abounds. This course is a survey of selected frequency-dependent phenomena that routinely are encountered in reflection-seismic data.
The following topics will be addressed in this course:
- Introduction to 4D seismic technology: A review of reservoir management concepts and the incentives for seismic reservoir monitoring, key 4D concepts, technical issues, success factors, and the role of 4D in field lifecycle planning.
- Reservoir engineering fundamentals: Describes how different reservoir depletion mechanisms influence fluid and pressure distributions in hydrocarbon reservoirs and how 4D seismic might be used to monitor them. Hydrocarbon fluid systems and conventional reservoir surveillance tools are also discussed.
- The petrophysical basis for 4D: Understanding the rock physics link between the geological and engineering properties of a reservoir and the elastic properties is essential to 4D interpretation. This section presents a review of the acoustic properties of fluids and how seismic velocities and density depend on rock properties, stress, temperature, and fluid saturation.
- 4D seismic modeling and feasibility studies: Where and when can 4D seismic methods be successfully applied? Time lapse seismic modeling is taken from simple spreadsheet approaches to well-log fluid substitution and then to seismic models derived from reservoir flow simulation. Approaches to estimate the business impact of 4D data are also discussed.
- Seismic acquisition and repeatability: The reliability of 4D seismic data is determined in large part by the similarity of repeated seismic surveys. Measures of repeatability and causes of non-repeatability are discussed along with strategies for acquiring repeatable seismic data in both marine and land settings.
- 4D seismic processing, data analysis and QC: The objectives of 4D processing are to maximize repeatability, preserve and resolve differences associated with production, and retain true relative amplitudes. Critical factors in 4D processing are discussed along with cross-equalization and data QC methodologies.
- Interpretation and data integration: What time-lapse seismic attributes are most effective for interpretation? How is production data used to validate 4D interpretation? When can map-based or volume-based interpretation methods be used? How can 4D inversion add value? How can 4D data be used to update geological and reservoir flow simulation models? What are the pitfalls in 4D interpretation? These issues and others will be discussed in the context of case studies that demonstrate 4D seismic application for water and gas sweep, pressure depletion and compaction, steam and CO2 floods, and CO2 sequestration.
- The future for geophysical monitoring: Other geophysical methods such as gravity and microseismic monitoring are seeing increased application within the industry. In addition, 4D seismic technology is moving from qualitative interpretation to quantitative analysis, enabled in part by the development of permanent monitoring systems and the instrumented oil field.
At the end of this course, the student should have an understanding of the fundamental principles of time-lapse 4D seismic monitoring applied to reservoir surveillance of saturation and pressure changes. The student will know:
In which geological settings, reservoir and fluid property conditions, and production scenarios 4D monitoring may be appropriate.
- How seismic acquisition and processing of seismic data can impact the ability to detect reservoir changes and what can be used to measure and maximize repeatability.
- The basic concepts and workflows for time-lapse seismic interpretation and integration with geological and production data.
- How 4D seismic data can be used to impact reservoir management.
- How 4D seismic data have been applied in a number of case studies.
- Recent advances in time-lapse geophysical technology.
The accompanying textbook is available for purchase.
SEG Life Membership 2004
David H. Johnston is being awarded Life Membership in recognition of his status as a world-class geophysicist who has made fundamental contributions and has shared those ideas with the greater geoscience and engineering communities. Dave received his PhD in geophysics from MIT. He has been employed by ExxonMobil Upstream Research Company and is currently worldwide coordinator and leader for time-lapse 4D seismic with ExxonMobil Exploration Company. He was honored for presenting the best paper at SEG's 1993 Annual Meeting, was selected as a Distinguished lecturer in 1999, and edited Reservoir Geophysics Volume 2. His service to SEG includes a term as secretary-treasurer and as technical program chairman for the SEG/CPS convention in Daqing. Dave has recently been awarded Honorary Membership in the Geophysical Society of Houston for his outstanding contributions. This is just one example of his long and valuable service to the geophysical community. He has also been a key fundraiser for the SEG Foundation, the organizer of numerous technical sessions, an inspirational spearker, mentor to younger geophysicists, and an active supporter of and frequent participant at the Offshore Technology Conference.
Biography Citation for SEG Life Membership 2004 
Contributed by Dan Ebrom
There is a world-famous David Johnston (of the financial world), who is similar to our own David Johnston (of the geophysical world) in that, when David speaks, the whole world listens!
For over 25 years, David Johnston has made fundamental contributions to geophysics in areas ranging from rock physics to time-lapse seismics. But from the beginning, his passion has been to extract the maximum rock and fluid information from seismic data and to extend the applications of reservoir geophysics across the life cycle of a field— from exploration to production.
His impact has been felt beyond ExxonMobil because Dave and his research teams have shared the results of their work through a substantial body of publications and presentations. SEG has benefited from David's significant leadership and service in geophysics in many ways, particularly his articles in GEOPHYSICS and THE LEADING EDGE. As SPE Distinguished Lecturer in 1992-93, he focused on applications of 3D seismic data to development and production. As an SEG Distinguished Lecturer, in 1999 he looked to the future of 4D seismic data in our industry. Dave's service to SEG also included serving as chairman of the Development and Production Geophysics Committee from 1988 to 1990, which helped kick off what has turned out to be a spectacular growth in reservoir geophysics within the Society. Dave was co-editor of the book Reservoir Geophysics, published by the SEG in 1992. He was a founder of the SEG Interpretation Committee, and served as chairman in 1991-92.
Just as importantly, Dave has been tireless in raising funds for the SEG Foundation. Twisting arms just enough to produce a smile (and a check!) is a special Dave Johnston strength! As SEG secretary-treasurer in 1989-1990, he established the Corporate Trustee Associates program and convinced Exxon to be the first member. As a graduate student at MIT, he improved our understanding of seismic wave attenuation through both laboratory studies and theoretical modeling. The 1981 SEG Reprint Series volume on Seismic Wave Attenuation, co-edited by Dave, was a primary reference for many years. After joining Exxon Production Research Company in 1979, he built on this experience and established a rock physics laboratory and was responsible for studies of the electrical and acoustic properties of sandstones and source rock shales.
In the mid 1980s, Dave participated in some early work on the analysis of anisotropy in multicomponent seismic data, coordinating field measurements and processing both surface and borehole data. His analysis of anisotropy in a fractured chalk was presented at the 1986 SEG Annual Meeting— the same year Amoco presented its seminal papers. Dave's research at Exxon went on to include velocity analysis and interpretation, focusing on lithology prediction and time-depth conversion. In 1989 he became group leader for velocity analysis, AVO, and borehole seismic interpretation research and in the early 1990s helped establish 3D seismic attribute research at Exxon. His paper on neural network calibration of seismic attributes was honored as the best at the 1993 Annual Meeting. In 1995 Dave initiated time-lapse seismic research at Exxon and is currently responsible for coordinating the worldwide application of 4D technology at ExxonMobil Exploration Company.
Dave was one of the visionaries who pioneered in extracting significant meaning from 3D seismic data. For a number of years, he has been an industry leader in expanding the applications of geophysics, especially in development and production activities, and in building an understanding of how geophysics can help solve problems in petroleum engineering. Throughout David's entire career he has been a consistent and strong supporter of SEG and its activities. We will continue to look to David in the future for his continued leadership and future contributions.
- Honors and Awards Program and Presidential Session, COLORADO CONVENTION CENTER • DENVER, COLORADO 4 P.M., SUNDAY • 10 OCTOBER 2004.