November 2003 Events Calendar

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Friday, November 7, 2003: SIPES Fall Social: 7:00 pm at the Petroleum Club, 800 Bell St, Downtown. Dr. Michael Economides, author of "Color of Oil" and worldwide energy issue expert, will have us spellbound with his observations and predictions on worldwide energy related events.

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Friday, November 7, 2003: HGS/GSH Shrimp Peel: 6:00 pm to 10:00 pm at Sam Houston Race Park, 7275 N. Sam Houston Pkwy West. Tickets $25 advance, $35 at the door. Look for reservation form in the GSH and HGS newsletters.

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Wednesday, November 12: GSH Technical Breakfast: 7:00 am Breadkfast, 7:30 am Presentation at Shell Lecture Hall, 3737 Bellaire Blvd. Note: Before 7:00 am, please enter via the guard station between 3737 and 3747 Bellaire Blvd. On street and off street visitor parking is available at 3747 Bellaire Blvd. Speaker: Vladimir Grechka (Shell E&P Technology Center). Topic: Generation and processing of pseudo shear-wave data: Theory and case study by Vladimir Grechka (Shell) and Pawan Dewangan (Colorado School of Mines). Contact: For further information, please contact John F. Parrish at 281-300-2570 or email GSHTechB@PeriSeis.com Please make reservations by noon Monday, 11/10.

Summary:
Processing of converted (PS) waves currently adopted by the exploration industry is essentially based on resorting the PS data into common conversion point gathers and using them for velocity analysis. In this presentation, we explore an alternative procedure. Our key idea is to generate the so-called pseudo-shear (YS) seismograms from the recorded PP and PS traces and run conventional velocity analysis on the reconstructed YS data. This results in an effective S-wave velocity model because our method creates data that possess kinematics of pure shear-wave primaries. We never deal with such complexities of converted waves as moveout asymmetry, reflection point dispersal, and polarity reversal, therefore, these generally troublesome features become irrelevant.

We describe the details of our methodology and examine its behavior both analytically and numerically. We apply the developed processing flow to a four-component ocean bottom cable line acquired in the Gulf of Mexico. Since the obtained stacking velocities of P- and YS-waves indicate the presence of effective anisotropy, we proceed with estimating a family of kinematically equivalent vertical transversely isotropic velocity models of the subsurface.

Biography:
Vladimir Grechka received his MS (1984) in geophysical exploration from Novosibirsk State University, Russia and a PhD (1990) in geophysics from the Institute of Geology and Geophysics, Novosibirsk, Russia. He worked in the same Institute from 1984 to 1994 as a research scientist. He was a graduate student at the University of Texas at Dallas from 1994 to 1995.

Vladimir joined the faculty of Colorado School of Mines, where he became Associate Research Professor of and co-leader of the Center for Wave Phenomena. He joined Shell International E & P in 2001 and currently works as Senior Geophysicist at Bellaire Technology Center. Vladimir's research is focused on theory of seismic wave propagation in anisotropic media, velocity analysis, multi-component seismics, and effective media theories. Vladimir received J.Clarence Karcher Award from the Society of Exploration Geophysics (1997) and the East European Award from the European Geophysical Society (1992). He is a member of SEG and EAGE and Associate Editor of Geophysics.

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Thursday, November 13: GSH Auxiliary Luncheon at the Houston Racquet Club. Join us as we welcome Valerie Koehler from Blue Willow Books, who will tell us all about the latest and greatest books for our reading enjoyment or for us to give as gifts for the upcoming holidays.
Please join us as we look forward to a year of entertaining, enjoyable and enlightening programs. Yearly dues are only $15.00. Call Membership Chairperson, Donna Parrish at 281-859-8088, GSH Liaison, Luann Cefola at 281-759-7338, or President, Carol Gafford, at 281-370-3264 for a membership application and information on how to join.

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Monday, November 17, 2003: HGS International Dinner Meeting: University of Houston Department of Geosciences AND U.H. Geoscience Alumni Association in association with the HGS International Group Presents: The 5th Annual Robert E. Sheriff Lecture Series: Social 5:30 pm, Dinner 6:30 pm at the Westchase Hilton, 9999 Westheimer. Featured Speaker: Dr. Brian P. Wernicke, Chandler Family Professor, Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, California. Title: "Large Scale Continental Extension".

Robert E. Sheriff Lecture Series:
The lecture series is sponsored by the University of Houston Department of Geosciences and UH Geoscience Alumni Association in association with the Houston Geologic Society International Group. Mr. Bill Beck, president of the University of Houston Geological Alumni Association (UHGAA) will serve as Master of Ceremonies. Dr. John F. Casey, Department of Geosciences Chairman, will present an overview of current activities at UH. There will be posters and presentations on current thesis and dissertation research activities of UH graduate students.

Come and meet the next generation of geoscientists from UH!!

The Robert E. Sheriff Lecture Series was initiated in 1999 by the UHGAA. For the past four years it has been co-sponsored by the International Explorationists Group of the Houston Geological Society.
The series honors Dr. Sheriff as an educator, scholar, and a proponent for the geosciences. Its mission is to:
1. Bring some of the best known geologists and geophysicists in the world to the Houston community in order to share highly relevant ideas to exploration geology and geophysics and,
2. Showcase geoscience activity at the University of Houston.

Cost: Members with reservations $25, non-members and walk-ins $30. Please make reservations by Friday, 11/14 to joan@hgs.org.

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Tuesday, November 18, 2003: GSH Technical Luncheon: 11:30 AM at Hess Building, 5430 Westheimer, Houston. Title: 3D Seismic Data Acquisition In Southern Louisiana: Considerations For Technical And Commercial Success, By Steve Knapp, Kevin Callaghan and Randy Sides, Seitel. Speaker: Steve Knapp (Seitel). Cost: $22 w/reservation, $27 at the door. Reservations: GSH 713/463-9477 or Email: Joan@hgs.org (reservations are encouraged)

Abstract:

Over the last two decades 3D seismic data has changed the way exploration and production companies discover and exploit subsurface hydrocarbons. Technical and commercial drivers that have made this high-resolution image available to a wide audience have accelerated its impact. Several key technical milestones have aided the advancement of the technique over the course of time: portable recording systems which can withstand the elements, recording systems that can acquire a large number of channels, radio telemetry, GPS positioning, and processing capabilities (prestack migration, AVO). On the commercial side, non-exclusive surveys rather than proprietary ownership has allowed for many explorers to benefit from one dataset with shared cost and limited liability, thereby lowering the cost for accessing the seismic data. In the end it is the team effort combining the data owner, the acquisition company, and the oil company that results in success from both a technical and commercial viewpoint.

The planning and execution of current 3D surveys bear little resemblance to their predecessors, especially when operations encroach upon urban areas. Project management has taken on added dimensions that require coordination of a multifaceted operation with stringent quality control procedures. Land work to secure permits, both surface and mineral, in the area of seismic operations is clearly one of the major logistical hurdles. In urban areas, nearly half of the project costs are allocated to permitting. In addition, the regulatory approval process involves interaction with many different municipal entities, ranging from local (town council), parish (Utilities Commission or Parish Police), state (Wildlife and Fisheries Commission), and federal (U.S. Army Corp of Engineers).

Project management also includes survey design, a cumbersome task in areas of restricted access due to environmental and cultural considerations or other factors that may restrict shot and/or receiver placement. Planning that considers these limitations facilitates efficient operations once the crew is actually in the field. In order to ensure optimal shot and receiver placement, aerial photographs or satellite images are typically used to determine exclusion zones and to assist in making adjustments in shot/receiver positioning and charge sizes for dynamite shots.

Surveys require extensive planning and this management, along with other considerations control costs, while maintaining data integrity. Typically data acquisition comprises half of the project cost distributed as follows: surveying (10%), drilling (15%) and recording (25%). Permitting and other land work constitutes an additional 45%, with miscellaneous extras filling out the remaining 5%. These include quality control in the field, data processing, and other items such as maps, aerial or satellite imagery and deliverables. Non-exclusive surveys allow for these costs to be shared while at the same time limiting liability.

In summary one finds that careful attention to the technical requirements for a given area, combined with close control of the decisions that effect cost yield a 3D seismic program with can be considered successful on both technical and commercial aspects. Cooperation and teamwork between the data owners, the acquisition contractors and the oil
companies ensures that the geophysical objectives are satisfied in a manner that benefits everyone. Technical and commercial risk needs to be managed when making decisions, not only by the oil company consumer, but also by the data owner provider. With these concepts in mind one can foresee an exciting future for seismic data acquisition in south Louisiana and in other challenging operational areas.

Biography:

Steve Knapp (stknapp@seitel-inc.com) is currently Business Unit Manager for Seitel Solutions and Chief Geophysicist for the Seitel Group of companies, with responsibilities that include data management and technology implementation in the USA and Canada. After obtaining a Bachelor's degree in Geology and Materials Science from Rice University in 1980 and a Master's degree in Geology from Texas A&M in 1983. Steve joined Digicon Geophysical in the Data Processing division, where he progressed through special projects into management. There followed a couple of overseas assignments; first with the NAM data processing center in the Netherlands and second in Digicon's commercial data processing center in Bogota, Colombia where Steve was the processing manager. Upon his return to the USA, Steve transferred from the vendor community to the E & P community when he joined Triton Energy as an international explorationist. In this role Steve was responsible for coordinating seismic data acquisition and processing on many projects covering the globe. In 1999 he joined Seitel and has been involved in the advancement of emerging technologies such as AVO, attributes, imaging, inversion, visualization and multicomponent seismology and has published a series of technical papers within these areas, one of which received the "Best Paper" award at the 2001 SEG Meeting held in San Antonio. He is a member of the AAPG, SEG, and EAGE.

Steve enjoys cooking, reading and spending time in the great outdoors with his wife, Mariela and their two sons, Thomas and George.

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Tuesday, November 18, 2003: GSH Rock Physics SIG: 5:30 p.m. at Visualization Center, Veritas DGC, Inc., 10300 Town Park Dr., Houston. Title: A Simple Method for Fitting P-wave Velocity Versus Water Saturation Curves by John Castagna, University of Oklahoma, and John Hooper, Fusion Geophysical Contacts: Keith Katahara (keith@spinexp.com) or Tad Smith (tad_smith@veritasdgc.com)

Abstract:
Gassmann's equation, which predicts a strong drop in P-wave velocity when a minor amount of gas is introduced into sandstone, is the low frequency limit of the more general Biot theory. Laboratory and log velocity measurements do not generally conform to Gassmann's equations and it is generally accepted that Biot theory cannot reproduce observed saturation curves. This discrepancy between observed velocities measured at high frequencies and Biot theory is sometimes referred to as non-Biot dispersion. However, we find that most measured saturation curves can be fit within the context of Biot theory if two additional concepts are employed (1) using only acoustically connected porosity rather than total porosity as suggested by Brown and Korringa, and (2) using an effective fluid modulus as suggested by Alain Brie to account for non-uniform distribution of gas in the pore space. In selecting the effective fluid modulus three saturation regimes must be considered. (1) Uniform distribution of gas in the pore space where a Reuss average of the fluid modulus is used (2) Segregated distribution where gas occurs preferentially in high aspect ratio pores and a Voigt modulus is used as observed by Domenico and explained by Knight, and (3) An intermediate regime containing patches of uniform and segregated distributions. Saturation curves predicted using this approach differ greatly from Mavko's patchy saturation model but agree with a wide variety of laboratory measurements

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November 19-21, 2003: HGS International Explorationists: Africa Oil & Gas Forum, at the Wyndham Greenspoint, Houston, Texas. View agenda at http://www.africacncl.org  Any questions please contact Mr. Christopher Alion, conference director and Sponsor, The Corporate Council on Africa at calion@africacncl.org, or Tel: (202) 835-1115.

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Speaker #1: Professor Robert Nowack, Purdue University

Subject: Gaussian Beams for Forward Modeling and Seismic Migration

Abstract:
The Gaussian beam method is an asymptotic method for the computation of high-frequency wavefields by the summation of paraxial Gaussian beams. It was proposed by Popov (1981) and initially applied by Cerveny, Popov and Psencik (1982) and Katchalov and Popov (1981). An advantage of Gaussian beam expansions is that the individual Gaussian beam components have no singularities along their paths which assures that the summation is regular everywhere. In contrast, the Maslov method needs well-separated caustics and pseudo-caustics. The Gaussian beam method also does not require two-point ray tracing which can be important for seismic imaging when multiple arrivals occur. Felson et al. (1991) and others investigated expansions of Gaussian Beams in which the wavefield is expanded over a position and wave number phase-space lattice. In terms of Gabor expansions, stable summations can be made over discrete, over determined frames of window functions. Gaussian beam expansions were applied to the migration of seismic reflection data by Hill (1990, 2001) and this resulted in a very efficient imaging algorithm in laterally varying media. I will first give several examples of using Gaussian beam expansions for forward modeling of seismic wavefields. I will then give several examples of using Gaussian beams for the seismic migration of sparsely sampled common-shot data. This will be applied to the SEG/EAGE salt model and compared with the Ray/Born inversion.

Biography: Robert L. Nowack

Robert L. Nowack received a BS (1975) in physics from Beloit College, an MS (1977) in geophysics from Stanford University and a PhD (1985) in geophysics from the Massachusetts Institute of Technology. Since 1986, he has been a professor of geophysics at Purdue University specializing in ray and beam methods applied to seismic imaging and tomographic inversion applied to the earth's crust. He was a visiting professor at the Institut de Physique du Globe at the University of Paris in 1989, at the University of Utrecht in the Netherlands in 1992, at the University of Texas at Austin in 2002, and at the University of California at Santa Cruz in 2003. He has served as an associate editor for the Bulletin of the Seismological Society of America since 1995 and Studia Geophysica and Geodaetica since 1999. He is a member of AGU, SEG, and SSA.

Speaker #2: Dr. Samuel Gray, VeritasDGC, Inc., Calgary

Subject: Nuts and Bolts of Beam Migration

Abstract:
Gaussian beam migration (Hill, 1990, 2001) is an elegant, accurate, and efficient depth migration method. It has the ability to image complicated geologic structures with fidelity exceeding that of single-arrival Kirchhoff migration and approaching that of wave-equation migration. In fact, its accuracy can exceed that of most wave-equation migrations in imaging very steep dips, especially in three dimensions.
We can view Gaussian beam migration as a generalization of Kirchhoff migration that operates in the frequency-wavenumber, as well as the time-space, domains, and allows for multipathing in a natural way. The key to this generalization is the use of Gaussian beams for the Green's functions. These are generalizations of standard rays that compute the wavefield at points some distance away from the raypath. Propagating the recorded energy along a particular beam, and applying an imaging condition, gives part of the total migrated image; the total image is the sum of the contributions from all the beams. Each beam can be specified to be planar at the Earth's surface, and the downward continuation can be performed on beams, or slant-stacks, of the input traces. Migrating a limited number of slant stacks over a limited number of initial directions makes Gaussian beam migration efficient, and assuring that the number of directions is adequate to sample the entire wavefield makes it accurate.
There are trade-offs, however. Gaussian beam migration is not quite as flexible as Kirchhoff migration, and it is also much more complicated because of its localizations in space/wavenumber and time/frequency. By relying on velocity along the raypath, the computed wavefield can be inaccurate away from the raypath, resulting in a less accurate image than wave-equation migration can provide. These trade-offs need to be understood and exploited for Gaussian beam migration to reach its full potential, and they are the subject of my talk.

Biography: Samuel H. Gray

Samuel H. Gray received a BS (1970) from Georgetown University and a PhD (1978) in mathematics from the University of Denver. Between 1978 and 1982 he worked at the US Naval Research Lab in Washington, DC, and was a faculty member at General Motors Institute (now Kettering University) in Flint, MI. From 1982 to 1999 he worked for Amoco and BP, first in Amoco's Tulsa Research Center and later at Amoco Canada. While at Amoco and BP, he was a member of several teams building and using depth migration and velocity estimation tools. Since 1999, he has been at Veritas DGC, where he continues to work on depth imaging, velocity estimation, and seismic modeling techniques. He has served as Associate Editor of Geophysics, and he has co-authored papers which have won the Best Paper in Geophysics award (1999) and Honorable Mention for Best Paper in Geophysics (1998 and 2001).

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