Location:
Westchase Hilton, 9999 Westheimer. Social Hour at 5:50pm. Dinner at 6:30pm.
Social Hour and Posters or Demonstrations 5:30 PM, Dinner and
Talk 6:30 PM
Speaker:
Dr. Virgil (Buck) Sharpton, NASA Lunar and Planetary Institute, Johnson Space
Center, Houston.
Abstract:
The collision between a large extraterrestrial object (probably a meteor) on
the surface of the Earth 60 million years ago in the Yucatan led to the
extinction of about 70 percent of the planet's species, including all
dinosaurs, at the end of the Cretaceous Period. The Chicxulub impact
basin on the northern coast of Yucatan appears to be the site of this
catastrophic impact event. The crater is completely buried by Cenozoic
platform rocks, so conventional geophysical techniques and drilling must
be employed to study the style and extent of deformation associated with
its formation.
Bouguer gravity anomalies indicate a configuration of multiple concentric rings, the largest of which has a diameter of nearly 300 km. Recently acquired seismic data substantiates this morphology and delineates in remarkable detail the smaller central basin formed by inward slumping of the excavation crater walls. Central crater diameter is of nearly 200 km and modest extensional deformation extends the area to approximately where the outer gravity ring is located.
The weakly circular northwest quadrant of the crater is interpreted as the superposition of the impact onto an older linear gravity high, rather than a post-impact fault as assumed by other workers. Such a linear feature may have resulted from processes that tore the Yucatan Peninsula away from the southern United States as the Gulf of Mexico opened during the Jurassic.
Several lines of evidence suggest that the basement rock under the crater is 500 million years old. Zircon minerals found in the strata in the western United States that mark the 65 million-year-old impact event have been determined to be about 550 million years old, consistent with the emplacement of the zircons as debris from the K-T-age impact basin.
Stratigraphic and paleo-environmental constraints derived from deep exploration drilling by Pemex and shallow drill coring by UNAM indicate that the higher standing topography associated with the inner basin flanks has undergone substantial deformation. Large blocks, some exceeding 50 m in thickness, were ejected more than 70 km from the edge of the excavation cavity. The breccias and melt rock s are mixtures of Pan-African crystalline rocks and Cretaceous sediments. The abundance of anhydrite and carbonate in the plat form section, which was melted and vaporized by this impact event, contributed to the destructiveness of the impact deformation.
Biographical Sketch:
Buck Sharpton received his Ph.D in geological
sciences from Brown University in 1984. Dr. Sharpton first became a
post-doctoral fellow at the Geological Survey of Canada's Earth Physics
Branch. In 1986 he joined the research staff at the Lunar and Planetary
Institute in Houston. His research interests center on meteorite impacts
and their geological consequences.
For the past eight years he has investigated several large impact scars on Earth, including the Chicxulub crater in Yucatan , and has published extensively on other craters. He is currently the chairman of the IUGG/ IUGS Global Impact Studies program, and leads an international Gallagher Research and Development Company team interested in deep drill sampling of the Chicxulub crater. Sharpton has authored over 60 research papers on impact cratering and he currently holds four research awards to study impact structures on Earth and the Earth-like planets.
Sharpton received distinguished performance awards from the government of Canada and the National Aeronautics and Space Administration. He served as guest investigator on the NASA Magellan Mission to Venus , was editor of the Proceedings of Lunar and Planetary Science, and is a member of NASA's Lunar and Planetary Geoscience Review Panel. He served as co-investigator on the recent project of reflection seismic profiling over the offshore portion of the Chicxulub crater.
Topic:
"3-D Seismic Visualization"
Abstract:
Michael J. Zeitlin will give a "live" computer presentation showing
interactive 3-D visualization technology applied to 3-D seismic
interpretation. The presentation will show examples of how visualization
technology can be used to reveal complex geologic patterns hidden within
3-D seismic data. Zeitlin will discuss how analyzing 3-D seismic attributes
with visualization techniques can reveal, in remarkable detail, subtle
depositional features. These features are often missed when using
conventional methods. Subtle features can be easily examined in their 3-D
structural context by using volume rendering, opacity, animation, lighting
and shading. The presentation will high-light visualization technology
trends including details about Texaco's new Visualization Center.
Zeitlin and the Texaco Visualization Center were featured in a 1997 Houston Chronicle article by Nelson Antosh. The title was "Looking into Nooks and Crannies, Oil Now Showing at a Theater Near You: Underground Formations Seen in 3-D Movies at Texaco Computer Facility." The article stated that Texaco is spending $3 million to build a 3-D visualization center behind its Exploration and Production building on Briarpark, the first such facility in the oil industry. It features a 160-degree screen on one interior wall. The rapidly changing images on the walls of the pod depend on three powerful new computers costing a total of $1 million. Silicon Graphics was a major software provider for Texaco, which also relied on Landmark Graphics and in-house efforts.
Biographical Sketch:
Michael J. Zeitlin is Port folio Manager of
Texaco's Integrated Reservoir Information and Global Visualization
Technology. Zeitlin heads a team of 14, whose work is about 18 months
ahead of the industry in the field of turning representations of underground
rocks into images. Zeitlin has worked for Texaco since 1980 in expert
systems design, computer aided exploration and hydrogeology. During
the past 6 years Mr. Zeitlin has been the driving force in Texaco's effort to
acquire, develop and deploy 3-D visualization technology throughout
Texaco's business units including the first commercial installation of the
industry's first visualization center. He received Texaco's outstanding
contributor award in 1993 and again in 1995 as well as other Texaco
awards for bottom-line contribution.
Before joining Texaco, Mr. Zeitlin received a B.S. double degree in earth/ space science and biology from the State University of New York at Stony Brook, Long Island. He also received a Master's Degree in geological oceanography from the Marine Science Research Center at Stony Brook. He is an active member of the AAPG, the Institute of Electrical Engineers' Computer Society, and serves on the Spring Branch School District's Partners in Education.
Speaker:
Pinar O. Yilmaz*, Ian O. Norton, et.al, Exxon Exploration Company,
P.O. Box 4778, Houston, TX 77210-4778
Abstract:
Tectonic domains of greater China are discussed with a summary of
stratigraphy, structure and timing of events. Tectonic assemblages include
Precambrian and older domains, accretionary complexes, melange and
flysch belts, sutures, rifted crust and oceanic crust. Our study also
mapped igneous rocks and their chemistry, major structures and
deformation timing.
There are several blocks which consist of continental or accretionary crust. The relative positions and interactions of these blocks during Phanerozoic time resulted in development of greater China. Amalgamation of these blocks created an extremely complex mountain system and diverse sedimentary basins. Activity continues to present day with deformation partitioned between thrusting in mountain belts and sliding along great strike slip faults.
There are four major events that play a significant role in the amalgamation of greater China. These are:
Biographical Sketch:
Pinar O. Yilmaz is a geologist, responsible for
external technology coordination at Exxon Exploration Company. She
received a Ph.D degree in 1981 from the University of Texas at Austin,
and a M.A. degree in 1978
from Bryn Mawr College, Pennsylvania, and B.A. degree in 1976 from
Hamilton College, New York. Yilmaz worked at Mobil Oil Corporation in
Dallas and Denver (1980- 1984) before joining Exxon Production Research
Company. She transferred to Exxon Exploration Company in 1994 into the
Global Studies Group and began her present position in the Technology
Department in 1997.
Ms. Yilmaz she is an active member of the HGS, AAPG and GSA. She has been the International Explorationists group technical program coordinator (1985-1992) and chairperson (1990-1992). She served on the HGS Board (1992-1993). At GSA, Yilmaz was president of the International Division and served on several commit-tees. She is a member of the following AAPG committees: International Liaison, Distinguished Lecture, Committee on Committees, Technical Program and House of Delegates. Currently, she is the Technical Program co-chair for the 1998 AAPG International Conference in Rio de Janeiro.
Poster Presentation:
"Punctuated Equilibria Plate Tectonics and Exploration
Strategies: Examples from Australia and South America"
by Malcolm Ross, President, Earth in Motion Technologies; and Vitor
Abreu and Peter R. Vail, Rice University, Houston.
A thorough understanding the interplay between plate tectonic events, subsidence, flexure and depositional systems, is critical to successful exploration, play concept development, and maturation modeling in frontier exploration. Conventional exploration techniques (seismic/well log mapping, geohistory, geophysical and forward modeling) can be used to quantitatively describe the stratigraphic pack-ages observed in basins, but the driving forces that are creating and destroying these packages are typically described qualitatively as "subsidence/ uplift events." In order to successfully predict depositional systems patterns, the timing and driving force of these events must be more quantitatively described. We observe that the tectonic history of plates is characterized by long periods of fairly constant motion interrupted by short events ("punctuated equilibria") of change in plate azimuth and/or rate of motion. These tectonic events express themselves either regionally or globally and cause changes in basin-wide stress fields and in subsidence patterns. These changes in subsidence cause shifts in major depositional center locations and characteristics. Analysis of the plate tectonic history of motion can predict times of quiescence and times of rapid changes in basin stratigraphy and therefore produce more effective exploration strategies. We have performed integrated sequence stratigraphic analysis in three basins (Barrow/Dampier, Otway, and Santos-Pelotas) on two continents (Australia and South America), spanning the Cretaceous Period. Although each continent has a different tectonic history, each basin responds to its unique tectonic history in a similar and predictable pattern : slow (or negative) subsidence diminishes volume and recognizability of transgressive and highstand system tracts and increases the volume and recognizability of lowstand system tracts. Exploration strategies and play concept development must take into account these patterns to be effective predictors of hydrocarbon reserves. Malcolm I. Ross presently serves as the director of the Paleomap Foundation, an industry-sponsored plate tectonic, paleo-geographic and paleoclimatic research consortium. He is also the principal consultant and owner of Earth in Motion Technologies, Inc. and is a certified Landmark ZMAP+ consultant trainer. He is also an ESRI Arc View registered developer. His e-mail is: Malcolm I. Ross
Location:
Hyatt Regency Downtown.
Speaker:
Wayne Tittle, Sonat Exploration.
ANNOUNCEMENT:
HGS President Jeff Lund is pleased to announce that AAPG President
Eddie David will be attending the HGS Luncheon and will make
introductory comments before the main presentation. Michael Halbouty,
John Amoruso, Jim Lewis and Merrill Haas, who are AAPG past
presidents, and future AAPG president Dick Bishop, have been extended
special invitation to this March luncheon as well.
Abstract:
The Cotton Valley reef trend of East Texas has undergone a dramatic
increase of interest and activity rarely seen in mature, domestic, onshore
basins. It is one of the most closely watched natural plays in the United
States. The reserves and opportunities for high-volume wells are
enormous. Drilling targets in the trend are small pinnacle reefs of Jurassic
age, with an average size between 20 and 60 acres, located at depths that
often exceed 15,000 ft. Cost and risk are high as a result of hostile
conditions including high temperature, pressure, sour gas content, and
dense rocks. High success rates in the trend are possible due to the
technological and economical evolution of 3-D seismic methods within the
last few years. Discoveries typically have recoverable reserve estimates
between 6 and 60 BCF.
Although 3-D seismic is the driving exploration tool to locate and pinpoint productive reef development, the technical requirements for 3-D to be successful are complex. Minor residual errors in deter-mining correct processing parameters like migration velocities can skew the true position of a reef, resulting in a dry hole. It is possible to lower the exploration risk by integrating surface and borehole seismic methods. Velocities measured in the well-bore at intermediate casing point can be used to remigrate a small volume of surface data around the target. This can happen in a short enough time to steer the well toward the crest of a more crisply-imaged reef, thanks to the new migration velocities. Integration of all three data sets results in a more precise image of the reef crest and can help lower the exploration risk. Introduction The Cotton Valley reef play had a promising start in the early 1980s when TXO drilled two wells in Freestone County (#1 McSwane) and Leon County (#1 A Marshall). Wells tested between 9 and 15 MMCFD. Recoverable reserves are estimated between 60 and 100 BCF. In 1996, Sonat Exploration drilled 137 ft of reef in the Fountain well that tested at 30 MMCFD and is estimated to hold reserves between 50 and 80 BCF. These discoveries generated much enthusiasm. They underline the high potential of the play that has seen an exponential growth in drilling activity. The average success rate in the reef play in now greater than 50% based on 29 reef discoveries out of 56 attempts. Primary exploration risk is reservoir uncertainty. Considering our drilling experience, it has been deter-mined the best reservoir production results from wells where the reef is penetrated at the crest. Therein lies the greatest challenge in geophysics. Imaging and defining the exact crest of these targets is only achieved as a result of meticulous attention to the details of seismic processing and thorough data interpretation.
Rapid development of 3-D has turned the trend into a new high-technology play. In this paper we illustrate the use and limitations of 3-D seismic for discovering pinnacle reefs and present our approach to minimize the exploration risk. A case study illustrating the integration of bore-hole and surface seismic is presented.
3-D or 2-D Seismic?
East Texas reef buildups are lithologically composed
of relatively clean carbonate rock of the Haynesville formation encased in
thick basinal shales of the Bossier formation. This interface creates a
high-reflectivity event in the seismic wave field as a result of a strong
velocity increase from the lower Bossier shale to limestone. In most cases,
pinnacle reefs denote amplitude dim spots along the regional limestone.
Different patterns of shape, structure, and amplitude have been observed
in the corresponding seismic data. Reefs discovered to date have ranged
in size between 20 and 80 acres. Considering the shape and small size of
drilling targets, the main geophysical exploration requirements for success
are:
Additional Risk Reduction Using Borehole Seismic The accuracy of 3-D images depends on quality and redundancy of seismic data as well as on the knowledge of correct subsurface velocities used for data processing. Pitfalls include residual errors in seismic velocities; a major problem in the most critical processing step of migration imaging. These errors tend to skew the true location of the small reefs not only vertically but laterally as a result of dip. Risk analysis reveals that the chance to miss the drilling target increases with greater structural dip and target depth.
We have used borehole seismic techniques successfully to fine tune the migration process. One benefit is to be able to calibrate 3-D processing and measure true seismic velocities by directly accessing the structure from the borehole. This allows us to migrate the surface seismic data set more accurately. We have obtained borehole seismic images that are higher resolution than surface seismic. These images help to identify the actual location of a reef around a well missed by an original hole or sidetrack.
More importantly, we have exploited the benefit of vertical seismic profiles (VSPs) being able to image ahead of and around the drill bit. We developed an innovative concept to steer drilling toward a pinnacle reef by interpreting a look-ahead borehole seismic survey. Our approach aims to evaluate a well trajectory before it reaches its final depth by interrupting the drilling process to run a multi-offset VSP survey. The results are spatial coordinates for optimum intersection with the drilling target.
From P&A to 18 MMCFD This case study presents an example of how an abandoned prospect with a marginal well, that included a dry sidetrack, was turned into a successful well by imaging around the borehole using VSPs. The sidetrack was based on dipmeter and surface seismic attribute interpretation. It missed reef structure entirely. Finally, the well was plugged and abandoned. Our new interpretation was based on subtleties in data processing and a more conservative interpretation. The look-ahead VSP pro-gram was developed in order to confirm our interpretation of the actual position of the reef structure.
Sonat drilled a new well at a location based on our interpretation and the integration of the VSP data. The distance between the marginal original hole and the successful new well was about 400 ft. The crest of the reef was penetrated and production established at an initial rate of 35 MMCFD from an estimated natural gas reservoir of between 40 and 60 BCF.
Conclusions:
The use of modern 3-D seismic technology is essential for success in
prospecting for pinnacle reefs in East Texas. Good results must be
achieved in the field and meticulous detail must be maintained during the
processing phase. Integrating surface, borehole seismic and the
interpretation of the look ahead multiple offset VSPs has further reduced
the risk and helped avoid missing small reef targets. Future emphasis will
be on remote evaluation of carbonate buildups to distinguish between
tight and porous reefs.