September, 1998
HGS Meetings

HGS Dinner Meeting

Structural and Sedimentological Response to Diapirism in La Popa Basin, Mexico

Abstract:

Upper Cretaceous to Lower Tertiary evaporite diapirs and evacuation structures exposed in La Popa basin, northeast Mexico controlled depositional patterns of sediment that accumulated adjacent to the rising salt masses. The superb exposures in La Popa basin provide an excellent, accessible outcrop analog with which to test and calibrate salt-tectonic models derived from scaled laboratory and computer models or high resolution seismic and well log studies of subsurface salt bodies ubiquitous in the Gulf of Mexico and other areas of petroleum exploration such as the Caspian Sea and offshore West Africa.

Strata interpreted as diapiric growth deposits flanking the diapirs display depositional thinning towards the diapir, abrupt lateral facies changes, and intense local deformation. Growth strata deformed by uplift of the rising evaporite masses were subsequently locally truncated by erosion associated with diapiric flaring or the movement of salt glaciers that repeatedly advanced and retreated over the seafloor surface. Advancement of the glaciers provided a mechanism of deforming and completely overturning underlying strata. Retreat of the glaciers corresponded to formation of erosional unconformities (locally angular) overlain by conglomeratic debris derived from failure of sediment mantling the salt glaciers. Repetition of this process resulted in the formation of progressive unconformities and growth strata analogous to those described in the proximal portions of fold and thrust terranes. However, this distinctive growth stratal geometry and unconformity bounded repetition of facies is primarily the result of halokinetic processes forming "halokinetic sequences". Periods of salt flaring and glacier development apparently correspond to periods of slow sedimentation during regional maximum flooding events.

Two types of salt bodies are recognized in La Popa basin, small scale (< 2 km across) salt stocks with subcircular cross sections and large scale (>10 km long) arcuate salt walls. One of the largest salt bodies referred to as La Popa structure displays an evolution from salt wall diapiric rise to late stage salt evacuation and formation of a counter-regional salt weld. Sediment dispersal patterns adjacent to this structure show drainage patterns roughly paralleling the structure and sediment pending in the axis of withdrawal basins formed adjacent to the structure.

Biographical Sketch:

Katherine A. Giles is an Associate Professor in the Department of Geological Sciences at New Mexico State University. Katherine received her BS in Geology in 1981 from the University of Wisconsin, her MS in 1985 from the University of Iowa, and her Ph.D. in 1991 from the University of Arizona. Her research interests are in the interaction between tectonics and sedimentation patterns with specific emphasis on carbonate successions. Her research areas include phylloid algal mound complexes associated with Ancestral Rocky Mountain basins, structural and stratigraphic evolution of the Antler foreland system in Nevada and Utah, and Upper Paleozoic through Paleogene tectonic evolution of northeast Mexico with emphasis on reef atolls associated with salt diapirs in La Popa basin, NE Mexico. Before joining the faculty at NMSU in 1993, Katherine worked for Exxon Production Research Company in Houston as a Senior Carbonate Research Scientist. It was here that she first became aware of the fantastic exposures of salt diapirs in La Popa basin while working on a regional study of the circum-Caribbean basins.

Katherine has received a honorable mention award from SEPM for excellence in oral presentation at the 1997 Annual AAPG meeting. She is currently servingon the Executive Committee of the New Mexico Geological Society and is a member of AAPG, GSA, NMGS, WTGS, and PBS-SEPM.

AAPG Student Expo

Mark your calendar, you're not going to want to miss this one. The AAPG has a new program which undoubtedly will be a huge success. Plan to attend the AAPG Student Expo, Rice University, September 20-22.

The Expo is part of the AAPG Internship/Mentorship Program which was created to provide an opportunity for geoscience students and recent graduates to gain work experience in the energy industry. The backbone of the program is the Student Expo (poster session) and Conference.

Students are invited to showcase themselves to potential employers by presenting their work during a poster session. Such an event in a single day creates a chance for employers of all sizes to become familiar with more students and schools than they could ever visit.

Highlights of this Expo include an Iceberg Breaker BBQ, Sunday, September 20th, 4-8pm (location to be announced).

Expo Poster Session, Monday September 21st, 9am-5pm in the Grand Hall, Rice University.

Companies and Geoscience Departments are also invited to participate in the poster session. As a follow-up, on Tuesday students will be doing one-day internships and office visits.

International Dinner Meeting

A 3D Seismic Volume of A Major Buried Thrust Front, Foredeep to Emergent Thrust Sheets, Quiriquire Block: Platform for Improved Exploration & Production, Eastern Venezuela Basin

Summary

Sizeable 3D seismic surveys over buried thrust fronts provide the start of a full 3D work process that greatly improves the exploration and production efforts of multiple plays in complex geologic trends in order to maximize their profitability. This full 3D platform not only improves seismic imaging and interpretation, but allows continuous 3D analysis of the projects, from structural modeling and mapping, to cost reduction efforts for well and development programs, to stratigraphic, structural and fracture modeling input for full field simulation and in-fill drilling. For this 3D work process to effectively function and have positive impact on the E&P bottomline, it is essential that there is interaction of all disciplines throughout the project life and continuity of experienced, highly motivated team members.

Introduction

YPF/Maxus and its partners have achieved a full 3D image of a buried thrust front in one of the most prolific hydrocarbon-bearing trends in the world with two merged 3D seismic surveys totaling 550 km2 of surface coverage (excluding overlap). This 3D volume covers the series of stacked thrust sheets, which form the eastward continuation of the Furrial Field complex in the Eastern Venezuela basin. These data and the interpretive products were performed as a part of our technological commitment to Lagoven in the service contract of the Quiriquire Block, awarded to Maxus in the 1993 Second Marginal Field Bid Round. The technical drivers that helped determine an aggressive bid on this block were:

  1. Proven basin with prolific hydrocarbon charge due to the world-class Tethyan Cretaceous source rock in a ìcoolî thrust front setting with a low geothermal gradient,
  2. Multiple reservoir objectives help mitigate the increasing reservoir quality risk on this east side of the basin,
  3. Evidence of reasonable amounts of quartz arenite sand systems which tend to retain effective permeability with depth,
  4. Evidence for a continuation of the Furrial and Orocual structural trends into the block with large thrust-induced anticlines (Viboral in particular),
  5. A structural model which supported well-developed 4-way closure in spite of the difficult, low-resolution 2D seismic.
The interpretation and mapping of the poorly imaged Viboral structure, in particular, was key. Many companies interpreted this structure as a continuation of the Furrial-Boqueron trend, but the depth of the first major reservoir interval and the size of the structure marked the difference between an aggressive or moderate bid. A 3D survey was part of the Maxus bid in order to help ease the concerns on reservoir target depth and the size and detailed geometry of the structural closure. Reservoir quality, however, loomed as the most serious risk and due to the low frequency of the seismic at these great depths, only the drill bit reveals these answers.

The first survey, the Viboral 3D, was acquired in 1994 and represents one of the first exploratory 3D seismic sets in Venezuela. The second survey, the Quiriquire Norte 3D, was completed in 1997 to the north of the first survey and has both exploration and development objectives. The surveys were designed with sufficient apertures to adequately migrate and image a full interpretive view of this complex, stacked thrust front.

The Viboral 3D (Southern Survey): 1994-5:, 325 km2, 8 Second Record Length; Dynamite Source
The primary target of the southern survey lies in the deep Viboral thrust structure at 16,000 to 20,000 feet, into which the San Luis-Lagoven-1X discovery well was drilled in 1996 and was followed by the SLL-2X well this year. The survey also included a shallower secondary objective in the syntectonic Carapita sands on the backlimb of the Viboral thrust structure ñ in part prompted by the Cachipo wells of the 1950ís which proved that the upper Carapita sands were marginally productive out of thin syntectonic sands. The Quiriquire Norte 3D (Northern Survey): 1996-7:, 244 km2, 7 Second Record Length; Dynamite (92%) & ViborseisÆ (8%) Sources
The northern survey was much more difficult to design and acquire due to the diversity of objectives at varying depths and the more difficult surface conditions (rugose topography, outcrops, culture and Quiriquire Field infrastructure). Target depths range from around 2000 to 15,000 feet. This wide range is primarily due to the stacked nature of this imbricated thrust front and our desire to include the Quiriquire Shallow Field with its post-thrust alluvial reservoir section.

Geologic Setting & 3D Survey Objectives

The principal objective section of the combined surveys ranges from greater than 18,000 feet in the south, as the target section descends into the foredeep, to the partially emergent and outcropping thrust sheets in the north which form the transition into the Serrania del Interior. This sequence of thrust sheets consist of Paleogene and Cretaceous reservoir-prone formations which ride on, or detach with, the prolific Cretaceous Querecual source rock. After the majority of the compressional deformation in the Miocene, these thrusts were rapidly buried under the sealing syntectonic Miocene Carapita, Mio-Pliocene La Pica and the post-thrust, monoclinal Plio-Pleistocene Quiriquire Formation. This burial effectively hides the immense underlying dimensions of five major thrust sheets which can have displacements of greater than 5000 feet and a combined structural relief of well over 20,000 feet. To the north, the Quiriquire alluvial sequence holds the historic Quiriquire Field, a stratigraphic accumulation of nearly 4 billion barrels of oil in place, 760 MMB of which have been recovered to date (around 15? API). Under this shallow monoclinal deposit lies the Quiriquire Deep Field, a long-known productive thrust anticline in the third thrust sheet of this buried thrust front succession.

It is important to realize why this thrust front tends to develop pronounced anticlines with well-developed 4-way closure. Part of this deformational pattern is due to the nature of the stratigraphic succession in this foredeep basin and the resulting fault and fold geometries. In particular, the under-compacted, ductile and shale-prone nature of the Carapita molassic section, which was rapidly deposited over the competent pre-thrust section, has a profound effect on the hangingwall and leading edge geometries. Thus, thrust faults in this trend are considered to ride on basal detachments in the Cretaceous Querecual or deeper shale sections, ramp through the massive sand-prone layers of the Upper Cretaceous and Paleogene and detach into this freshly deposited Miocene Carapita section. This defines large-scale flat-ramp-flat geometries which tend to form extremely well-developed anticlines with long, steep forelimbs and good structural closures. This fold style may be most pronounced in buried thrust fronts where the upper detachment levels emerge out into unconsolidated, shale-prone or even starved basin settings. Thus, for this and other reasons, fault and fold style can change through time during the evolution of a thrust system, and can determine differences in the degree of trap risk and structural definition of the prospect portfolio.

3D Seismic Target Summary: Five Stacked Thrust Sheets
The entire Quiriquire-Viboral stacked imbricate thrust front affords at least 5 major target thrust sheets, consisting of the following sequence, from south (deep) to north (shallow):

  1. Viboral Thrust Sheet,î 16,500 to 25,000 feet,
  2. Second Step Thrust Sheet,î 12,000 to 15,000 feet,
  3. Quiriquire Deep Thrust Sheet,î 6,000 to 11,000 feet,
  4. 609 Thrust Sheet,î from around 4,500 to 8,000 feet and covering a smaller area
  5. Northern Thrust Sheet,î which actually consists of a series of more diversely deformed sheets and fault blocks at around2,000 to 6,000 feet.

Each thrust sheet contains huge fold structures with 1500 to 4000 feet of vertical relief, 10 to 15 kilometers in length and some 3 to 6 kilometers in width. The flanks of these structures typically reach 45? angles and greater. Thus, the 3D survey designs took into account not only the necessary migration apertures, but also factored in what might be referred to as "interpretation aperture" in order to ensure sufficient lateral image of this low-angle thrust environment with the diagnostic forelimb, backlimb, footwall, hangingwall, lateral ramp and tear fault features.

Examples of Exploration & Delineation Wells Based on 3D

San Luis-Lagoven-1X Well: Viboral Thrust Sheet (Actual Total Depth: 19,165-feet)
Deep Thrust Anticline
The main work commitment of the Quiriquire Block service contract for Lagoven was the drilling of the deep exploration well, SLL-1X, on the principal deep thrust anticline of Viboral, the next structure in the eastward continuation of the prolific Furrial to Boqueron trend. As one of the deepest wells in the trend, it required large amounts of pre-planning and full multi-discipline coordination, taking into account Lagovenís considerable experience. We elected to first shoot the sizable exploratory 3D seismic survey in 1994 for a number of reasons. Some of the prominent factors were:

The results of the Viboral exploration 3D survey were excellent (parameters to be given) and clearly showed the large dimensions of a thrust anticline with nearly 4000 feet of closure. A comparison between the original 2D and the 3D seismic illustrates remarkable improvement. With a high quality 3D data set, it was possible to be selective in terms of these and other location criteria.

Not only is the crest and classic fault bend fold feature clearly imaged, but the steep forelimb, internal faults and fold geometry, lateral ramps, tear faults, footwall and even the subthrust segments are all exceptionally imaged ñ especially considering the depth and the resulting low frequency of the data. The quality of the 3D data also provided a way to continuously ìviewî the drilling progress in the troublesome overlying La Pica and Carapita section, especially with the critical casing points near the top and base of overpressure (10,300 and 16,500, feet [MD] in the first well). Detailed analysis and treatment of the 3D seismic velocities helped provide accurate depth prognoses, casing depths and contingency plans.

The second well, San Luis-Lagoven-2X, is currently being drilled. Greatly aided by the 3D data, this second well was positioned at a structural level in context with the results of the first well and on the basis of 3D cumulative dilational strain modeling which will allow a contingency high-angle borehole to optimally intersect the predicted fracture sets for improved effective permeability.

Cachipo-6X Well: Overlying Backlimb of ìViboral Thrust Sheetî (Actual Total Depth: 16,077 feet [MD]) Syntectonic Carapita Play
The second well commitment of the Quiriquire service contract was the Cachipo-6X well which targeted seismic amplitudes within the 3D volume in the syntectonic Miocene Carapita section over the backlimb of the Viboral thrust anticline. The general nature of this play is considered to be a deeper analogue to the proven play-types in the trend which can be described as stratigraphic accumulations within small piggy-back sub-basins on the backlimbs of the underlying thrust anticlines. The prospect concept was that these amplitudes were sand-prone units of several thousand feet which were laid down within an extensional slump block above Viboralís backlimb as the unconsolidated syntectonic sediments rotated and collapsed during the growth of the thrust anticline. The Cachipo wells, which were drilled into the shallower Carapita level during the 1950ís, proved that some of these types of sands had been charged with light oil. The results of the Cachipo-6X well showed a predominance of siltstone, with insufficient reservoir quality sandstone.

Tropical-1X Well: ìSecond Step Thrust Sheetî (Planned Total Depth: 14,865 feet [MD]) "Hidden" Imbricate Thrust Sheets
One of the immediate results of the Quiriquire Norte 3D, even with its fast-track version, was the imaging of a hidden imbricate on the ìSecond Step Thrust Sheetî which the previous 2D seismic had not succeeded in resolving. Even with the new 3D data in mind, it is difficult to pick out the position and geometry of this extra thrust imbricate on the 2D seismic. The 2D seismic shows only a ìsmearedî image of these overlapping sheets and does not resolve the top of the principal thrust sheet as it ìdisappearsî under the overlying imbricate. Thus, the 2D data show only a small structure with regional dip. The 3D data, however, clearly show that this structure continues under the upper imbricate, thereby gaining considerable structural relief. This difference in structural interpretation is significant since the prospect increases from a few hundred feet to 1500 feet of structural closure with a four-fold increase in area. This prospect is scheduled to be drilled by the Tropical-1X well this year.

QQ-685: Delineation Well of the Quiriquire Deep Oil Rim With a Follow-up Horizontal Well (Planned Total Depths: 10,300 [MD] feet +2000í Horizontal Leg)
The Quiriquire Deep Field was discovered below the stratigraphic Quiriquire Shallow Field in 1952 with a gas blowout that later proved to be part of a gas column of around 2900 feet with an additional 500 to 700+ feet of oil rim under the gas. With the 3D control, the QQ-685 well will target this oil rim, offsetting the prolific QQ-676 well. Although the oil column is relatively thick, the steep flanks of the anticline make the 100-foot thick Oligocene Los Jabillos reservoir a difficult target. After gaining the necessary structural and stratigraphic control from a vertical pilot hole, a separate well will be drilled with a 2000-foot horizontal leg through the 100-foot thick Oligocene reservoir, parallel to the oil/water contact. Once positive results are obtained from the QQ-685 well, further development wells and a gas cycling project will follow.

The 3D Platform & Multi-Discipline Team Aspects: Risk Assessment & Optimization of Complex Projects

One of the principal benefits of this sizeable 3D seismic volume is that it established a platform from which many other aspects and disciplines could continue to evolve in a 3D framework:

It is essential that there is continuous interaction of all disciplines and individual team members for this 3D work process to properly function and maximize the profitability of these complex geologic trends.

Technical Risks: Reservoir Quality and Hydrocarbon Phase
Due to the extremely favorable petroleum system in the Eastern Venezuela Basin and the large size of the thrust structures (1500-4000 foot closures, perhaps filled to spill), the most serious technical risk is reservoir quality. The other important prospect risk is that of hydrocarbon phase which varies considerably throughout the trend, from gas-condensate, to volatile oil, medium gravity undersaturated oil and heavy oil to even tar. Tar mats can occur not only due to biodegradation, but also due to asphaltene drop-out at great depths. In many cases, of course, the hydrocarbon phase and reservoir risks are intimately coupled since, for example, some low quality reservoirs produce due to the high mobility ratio of that structureís unique hydrocarbon phase and high reservoir pressures, while in other structures, better quality reservoirs fail to effectively produce due to somewhat heavier gravity crudes. Our evaluation and approach to the reservoir risk is considered to be one of the most challenging technical problems we face in the frontier areas of the Eastern Basin and as deeper and more subthrust plays are pursued throughout the basin. Solutions with respect to the reservoir risks are likely to include:

Conclusions

The 550 km2 combined Quiriquire-Viboral 3D seismic volume provides coverage over an entire buried thrust front and is one of the first in what we believe will be an industry trend to increasingly use 3D technology to optimize the exploration and development of complex geologic trends. Rather than yielding an image of a single structure, this 3D volume provides a unique, continuous view of the geometry and development of stacked and buried thrust fronts, from the deep thrust anticlines encroaching the foredeep, to the highly elevated and partially eroded emergent thrust sheets that form the outer ramparts of the Serrania del Interior. The huge 1500 to 4000-foot thrust structures form a stacked imbricate sequence of Paleogene and Cretaceous reservoir-prone section, underlain by world-class Cretaceous Querecual source rock and draped by excellent Miocene Carapita seal, all of which provide the economic incentive to undertake such extensive 3D efforts. Reservoir quality looms as the most serious threat to the successful outcome of projects in this trend. In tandem with reservoir quality, hydrocarbon phase can also be a limiting factor. Finding solutions and achieving success in regards to reservoir quality is one of industryís greatest challenges as the proven reservoir systems are pursued into the less known areas. Optimum success will depend upon our industryís ability to deal with low-porosity and fracture-enhanced reservoir systems. Thus, it is even more critical that the other technical risks, such as structural definition, are efficiently assessed by using advanced concepts within a robust 3D framework.

The Quiriquire-Viboral 3D seismic volume acquired over this Eastern Venezuela buried thrust front allows continuous 3D treatment and analysis of the projects, from structural and stratigraphic modeling to drilling and reservoir simulation. Thus, the 3D platform is not only for structural interpretation and visualization, but also 3D fracture/strain analysis, stratigraphic modeling, borehole planning ñ including high-angle and horizontal drilling ñ on-the-fly adjustments while drilling, well and prospect evaluation, reservoir simulation, early and optimum reservoir pressure maintenance programs, and finally, secondary sweep programs with in-fill drilling. The benefits include more accurate well planning and drilling programs which provide one of the best ways to reduce individual well and total development costs, while minimizing the chances of missing productive fault compartments, especially in the case of ìhiddenî low-angle imbricates. This becomes even more critical when facing complex fluid phase changes and thin oil rims which demand precise imaging, targeting, drilling and evaluation. The scope and economic implications of these complex projects require a realistic understanding of how all this must fit together into seamless project phases in which continuous interaction of all disciplines and the individual team members throughout the course of these projects is essential. We trust that the results of the Quiriquire-Viboral project with continued full implementation of this team process, will have important implications on the future exploration and production efforts in the Eastern Venezuela Basin, especially in its more frontier areas such as to the east in Guarapiche and in the progressively deeper and subthrust positions throughout the basin.

Acknowledgments

The authors are grateful to YPF/Maxus, Lagoven and our other partners, BP-Venezuela and Otepi, for their permission to present this talk. The list of contributors to this part of the Viboral and QQ North project is incomplete without Martin Emery, Les Niemi, Dave Rolling, Qingming Yang, Jean Jew, Jeff Ventura, Carl Burgman, and David Miller. We appreciate and always will remember their contributions to the Maxus Venezuela effort. We are more than grateful to the patience and diligence on the part of our drilling engineers, in particular, Doug MacAfee and John Bell. We are grateful to Mike Giambra for his high quality acquisition monitoring and the many ways in which he went the extra mile. We wish to acknowledge the quality of effort and work product provided by Western Geophysical (Venezuela, Dallas, Houston, Denver) during the past 3 years of acquisition and processing.

Special thanks go to Lagoven staff and managers for providing their experience in the trend and facilitating the progress of the Quiriquire Block effort.

We thank Ray Young for his helpful review of this extended abstract on such short notice.

Vincent Rigatti Biography

Vincent Rigatti is an exploration coordinator and senior geophysicist for Maxus Venezuela in Dallas, Texas. He has been employed with Maxus/YPF/Diamond Shamrock for 14 years. He has worked in Dallas, Jakarta, Midland, and Amarillo, and during that time he has worked many of the basins in SE Asia, and the continental US. Previously, he worked for Getty Oil Co. He has a BS degree in Geology/Geophysics from the University of Connecticut in 1981. His technical interests are in seismic imaging in difficult/complex trends, 3D interpretation/mapping, and visualization.

Joint HGS & SIPES Lunch Meeting

Global Warming or Just Hot Air?

Abstract:

Environmental issues have assumed a prominent place in today's political and scientific thought in the western industrialized countries. Within the last 50 years, these countries have attained a comfortable control over man's historic struggle with the elements of nature. Although natural disasters of earthquakes, drought, hurricanes and flooding still occur quite regularly, the affluent, industrialized countries deal effectively with these occurrences and the loss of life and general impoverishment that has historically resulted from these disasters has been greatly diminished. This relatively new position of strength to withstand the results of natural disasters has spawned a new vision of man's relationship to nature. Out of this new vision, concern for global trends and possible trends has generated several issues that are being addressed by political leaders and policy makers across the globe.

Global warming caused by man is probably the most significant environmental/political issue of the day. A crescendo of news reports proclaiming consensus among global climatologists was unleashed upon the public prior to the Kyoto gathering in Japan in December of 1997. Subsequent reports note that the scientific community is now in agreement that man induced global warming is occurring and that steps must be taken to avert a global disaster. At the very least, additional funding will be required for further research and monitoring of the situation. At every opportunity, Vice President Gore, a notable proponent of the global warming hypothesis, declares the scientific debate to be closed and attempts to focus attention on his plan to save the world from the reckless behavior of man.

Contrary to the opinion of Vice President Gore, the scientific discussion of the global warming issue is not over. As evidence of this, a petition drive led by Dr. Arthur Robinson from the Oregon Institute of Science and Medicine has gathered signatures, as of June, 1998, from over 16,500 individuals who hold degrees in science on a petition which states in part, "There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth's atmosphere and disruption of the Earth's climate."It appears that serious scientific discussion of the topic is just now beginning.

The subject of the global warming debate is the Greenhouse Effect that results when greenhouse gases in the earth's atmosphere absorb infrared heat radiating from the earth and hold that heat close to the surface of the earth preventing its escape back into outer space. The Greenhouse Effect is necessary and essential to life on this planet and maintains the earth's temperature and climate that we enjoy today.

From the geologic record of the earth's climate history, abundant evidence exists that the earth's temperature is in constant flux when viewed over geologic time. Ice ages and warm periods have come and gone in the past without any influence from man. Such changes should continue in the future from natural causes (most likely from slight fluctuations in heat generated by the sun). The crux of the political debate today is whether or not activities of man, namely the release of carbon dioxide, are affecting or will affect the earth's climate.

Measurements taken over the last 40 years at the Mauna Loa Observatory in Hawaii and confirmed by measurements taken around the world show a steady increase in atmospheric carbon dioxide. Since carbon dioxide is a greenhouse gas, it has been reasoned that the observed increase should cause an increase in the earth's greenhouse effect. Although Dr. James Hansen's analysis of land based temperature points, which is regularly cited in discussions on this topic, indicates an increase in global temperature during the last 100 years, the bulk of the temperature increase occurred before any significant man-induced increase in carbon dioxide concentration began. In fact, as illustrated on Graph 1, the earth's temperature exhibited a 30-year cooling trend from 1940 through 1970 while carbon dioxide concentrations were rapidly increasing. The reasonable conclusion from these data is that carbon dioxide concentrations were not the controlling factor in global temperature during this period. This conclusion is not surprising in light of the fact that carbon dioxide comprises less than 2% of the earth's greenhouse gases.

Since the proponents of man induced global warming have no hard data to support their hypothesis, they rely primarily on anecdotal justification bolstered by computer simulations of the earth's climate for the next 100 years. These computer simulations are comprised of hundreds of assumptions and estimated data points which can and do yield variable results depending upon the individual doing the estimating. The results are so sensitive to the initial input data that a 1% difference in the input parameters can change the result from a global temperature increase over 100 years to a global temperature decrease over the same time period. In addition, none of these global climate models has yet produced anything that resembles a history match of the observed temperature data over the last 100 years.

Considering the dramatic implications from the political proposals currently being considered, scientific discussion must be continued on man-induced global warming and proponents of this hypothesis should be challenged to support their contention and explain the observed facts and data. Earth scientists especially need to be informed on this matter and need to lead the public debate regarding the theory's merits. While man-induced global warming may have little scientific basis, it is a very real political issue with very severe consequences for all of us. It is imperative that knowledgeable earth scientists confront this issue and not sit idly by and allow special interest politics to achieve their goal.

Editor's Note: This abstract is unedited and unabridged, and printed as presented by the author. The views and opinions expressed do not necessarily reflect those of the Houston Geological Society, its Executive Board, or the Bulletin staff, nor does publication constitute endorsement.

Author Biography

William M. Kazmann received a B.S. and M.S. in Petroleum Engineering from the University of Texas at Austin in 1973 and 1974. His career as a petroleum engineer began with Texas International Petroleum Corp. based in Midland and Oklahoma City and then Bonray Drilling Company. Bill became a geological engineer with Wessely Energy Corporation in Dallas in 1978 to 1980 where he was involved in development and sale of drilling prospects to industry partners and provided technical testimony at various state regulatory hearings. In 1980 through 1984 he worked for Resource Evaluations, Inc. as petroleum engineer and vice president. He organized his own exploration partnership Onset Petroleum Corporation with capitalization of $1.2 million to fund a secondary office in Houston. He co-founded Primary Petroleum Corporation in 1984 where duties included all aspects of evaluation, selection, and development of drilling prospects for sale to industry partners. Bill joined LaRoche Petroleum Consultants, Ltd., in Dallas in 1996 where he is a partner, preparing field studies, reserve estimates, and reports on domestic and international oil and gas properties. His areas of expertise include the Gulf Coast, Permian Basin waterfloods, and the Mid-Continent.

Emerging Technologies Dinner Meeting

Prediction of Rock Properties Using Well Logs, Seismic Attributes and Neural Networks

Abstract:

This case study shows the benefit of using multiple seismic trace attributes and the pattern recognition capabilities of neural networks to predict reservoir architecture and porosity distribution in the Pegasus Field, West Texas and net pay and reservoir property distribution in the Zafiro Field, offshore Equatorial Guinea.

The study used the power of neural networks to integrate geologic, borehole and seismic data. Illustrated are the improvements between the new neural network approach and the more traditional methods of estimating rock properties from seismic data, such as seismic trace inversion, amplitude mapping, and AVO studies. Our procedure is straight forward but does require careful quality control to insure reliable predictions from the seismic data. Network training, test, and validation data sets provide calibration of seismic attributes with well log data, optimize the network parameters, and estimate the performance of the system to predict hidden representative data.

Comprehensive statistical methods and interpretational/subjective measures insure that only attributes providing true relationships and a physical basis are used in the prediction of rock properties from seismic attributes. The result is a 3-D volume of seismicly derived rock properties for the reservoir interval of interest. In effect, we are transforming the seismic trace attributes into seismic-scale petrophysical logs. The advantage of this transformation is the additional interwell information this method provides. The additional reservoir detail allows for optimum placement of horizontal wells and improved field development.

Author Biography

Jim Schuelke is a Senior Geophysical Advisor with Mobil's Technical Center in Dallas, Texas. He is the Team Leader for a multi-disciplinary team researching and developing new geophysical analysis and interpretation technologies. His latest work is the development of a method to use more of the seismic attribute information and to integrate it with geologic, borehole and engineering data. This technique has been very successful in quantifying the seismic information and deriving more accurate rock and fluid properties from the seismic data. Jim started his career in geophysics with Geophysical Service, Inc. twenty five years ago. He came to Mobil via the Superior Oil merger and joined their research and services group in Dallas. Jim has a very diverse work record having put in his time in seismic data processing and acquisition, geophysical interpretation, special projects work, research, consulting, training and project management. In addition, he has worked both domestic and international, exploration and production.