May, 2000
HGS Meetings

HGS Dinner Meeting

"Into the unknown: a history of the discovery of the giant fields of the western Mississippi Fan foldbelt, Gulf of Mexico"

Book Signing: Allen G. Hatley, author of the book: "The Oil Finders: A collection of Stories about Exploration" will be available to sign his excellent book.

Abstract:

Over the last 15 years, several giant petroleum accumulations have been discovered in the Mississippi Fan foldbelt, deepwater Gulf of Mexico. In the mid 1980s, initial work was driven by interest in the nature of sections at the edge of, and immediately inboard of, the Sigsbee Escarpment. Outboard and counter-regional dip beneath an allochthonous salt canopy was recognized in early speculative 2D seismic transects.

In the first area-wide sales in 1984 and 1985, all but the exclusively subsalt features of the foldbelt were leased. Progress in assessing the foldbelt slowed with the oil price collapse of 1986. In 1987, Shell drilled the first foldbelt structure in Atwater Valley Block 471. The well mitigated the chief concern, a lack of reservoir, but dampened hopes due to a lack of petroleum. By mid-1994 only four of the trend's features remained leased.

In 1993, BP's regional work suggested that the potential of these very large structures merited another look. In addition to Neptune, which appeared to be of substantial size, several other features were leased, including Atlantis and Mad Dog.

Rumors of the 1995 Neptune discovery re-ignited interest in the area. Pre-merger Amoco had established a position in the very competitive 1996 and 1997 sales and further leveraged into the trend in 1998 by bringing a rig to expiring acreage. In 1998, three wells were drilled in the trend. The Neptune appraisal well was drilled in Atwater Block 574, the Atlantis discovery was drilled in Green Canyon Block 699 and the Mad Dog discovery was drilled in Green Canyon Block 826.

Seismic imaging was key in exploring the area. A combination of shallow salt sheets, significant seabed topography, and steep dip panels within the folds themselves created a significant imaging challenge. Integrated teams seismic contractor and oil company personnel addressed the issue aggressively, working with both proprietary 3D post-stack and pre-stack depth seismic volumes for the initial discovery at Neptune. Subsequent studies have utilized proprietary 3D seismic volumes.

Biographical Sketch:

John J. Farrelly is a subsurface team leader for BP. He attended the University of Texas at Austin receiving BS and MS degrees in 1984 and 1987. John joined the industry in 1988. He has worked in exploration and appraisal across the deepwater Gulf of Mexico and several other regions including Trinidad, Colombia, the northwest shelf of Australia, and New Zealand.

Julie d'Ablaing is a geologist at BP, Houston, Texas. She received a BSc degree in geology from Hull University, England in 1984 and an MSc degree in micropalaeontology from University of London, England in 1985. Julie began her career in BP Exploration in 1985 at Sunbury Research Center, transferring to Houston in 1989. Since moving to Houston, Julie has worked in deepwater exploration for BP, including exploration and early appraisal of the Mississippi Fan foldbelt trend prospects for six years. She recently began to work on the appraisal of the deepwater BP Amoco Crazy Horse discovery.

Gary Grubitz graduated from the University of Oklahoma in 1979 with a BS in geology and joined Cities Service Oil Co. Since 1981, he has worked in exploration for BHP Petroleum in Oklahoma City, Houston, and Melbourne. In 1995, he became BHP's exploration team leader for the Atwater fold belt.

Mike Moore graduated from the University of Alaska at Fairbanks in 1979 with an MS degree in geology. He went to work for Exxon holding several exploration and development positions, mainly in the Gulf of Mexico. Mike joined BHP in 1993 and has been involved in the exploration and appraisal of the Western Mississippi Fan foldbelt for the past five years.

Poster One:

"Gulf of Mexico evolution, from basement to seafloor"

by Allen Lowrie and Susan Moffett

Petroleum exploration has entered a critical phase, with the search for hydrocarbons extending to deeper water and deeper strata. There is a real need to determine how the entire stratigraphic column responds to existent stresses, from basement to seafloor. To the present, there has been a genuine neglect of effects arising from basement and near-basement. Deep-sea surveys show the existence of mid-ocean ridges (MOR), extinct or active, intersected by fracture zones of various sizes, ranging from basin-spanning, first-order features at approximately 110 km spacing to much smaller features. Detailed bathymetry reveals that fracture zones are generally perpendicular to MOR and parallel to each other and that spreading ridge segments may be offset from each other. Free-air gravity data represents MOR, fracture zones, transitional and oceanic crust, and Louann Salt beneath sediment cover in the Gulf of Mexico.

Mapped fracture zone trends coincide with some salt trends north of the Sigsbee Escarpment. This may indicate a causal relationship. Deep-sea data suggest greater heat flux along fracture zones. Greater heat flux rising through overlying sediments should impact continuity of the Louann salt wedge and surrounding groundwater flow. Hot groundwater can transport hydrocarbons in solution, serving as part of the fluid migration system, and dissolve salt, re-precipitating it elsewhere.

The Gulf of Mexico is seismically active in some regions, with at least 150 seismic events since 1963. These events occur at different depths: events less than 10 km deep occur within sediments; those between 10 - 20 km occur along sediment/basement interface, and those deeper than 20 km are within the crust. Earthquake data must be combined with other geophysical data in the emerging basin synthesis.

There is a need to discern how principal stresses within the continental margin operate. There is also the growth through time of the Gulf Coast geosyncline, which has been linked to extrusion of Louann Salt. The implications are that the salt transmits lateral stress. Review of geophysical data from the Nigerian and Gulf of Cadiz margins suggests the entire slope is sliding, similar to the Gulf of Mexico passive margin.The Louann Salt may diffuse the confining pressure, creating the Mississippi Fan foldbelt. Regional confining stress at base of slope, with possible basement interaction, makes the fan fold belt an area of dynamic geology. Finally, resolution of the evolution thereof will be a major key to understanding how passive margins operate.

Biographical sketches

Allen Lowrie has been an explorationist for the past 37 years, having worked for Lamont-Doherty Geological Observatory of Columbia University, Mobil Oil and the U.S. Navy. In those years, he has sailed all the world's oceans save the Arctic and been to all continents except Antarctica (and freezing is not now a life goal). He has written three books and some 60 technical publications, taught at Tulane University, University of Southern Mississippi and continuing education for SEG and AAPG. His abiding interest has been in continental margins and their evolution. The distribution of tectonics from province to province and how they interact is the question to be answered. Allen's present objective is to gain entrance into the massive database held by oil exploration companies and to work with company personnel.

Susan Moffett earned an MS in the field of marine science with a thesis topic including micropaleontology, biostratigraphy and sedimentology. She is employed by the U.S. Navy to interpret and synthesize geophysical/geological data. Susan's current interests include sedimentary processes along continental margins.

Poster Two:

"Importance of depositional facies, early diagenesis and unconformity karstin Arbuckle reservoirs from Central Kansas by D. Mark Steinhauff, ExxonMobil Exploration Co. Evan K. Franseen, Alan P. Byrnes, and Jason R. Cansler, Kansas Geological Survey"

Arbuckle strata account for about 40% of the produced oil and known reserves in Kansas. Much past production has come from the upper 25 feet of the Arbuckle in areas with structural highs and regional uplifts related to basement structural elements that were enhanced by karstic processes related to the overlying unconformity. A detailed analysis of facies and reservoir characteristics of the Arbuckle has not been performed. Results from our study of more than a dozen cores from several regions in central Kansas suggest that Arbuckle reservoir characteristics are strongly related to depositional facies, early diagenesis, and dolomitization. Development of brecciation, fracturing and dissolution related to the post-Arbuckle unconformity is variable and alternately created or destroyed porosity.

Five main depositional facies account for more than 85% of the cored intervals described from eleven cores. Listed in order of decreasing relative abundance, these include (1) clotted algal boundstone, (2) laminite algal boundstone, (3) peloidal packstone-grainstone, (4) packstone-grainstone, and (5) wackestone-mudstone. Intraclastic conglomerate and breccia, cave fill shale, depositional shale, and chert account for the remaining 15% of the total rock. Matrix and grain size are the controlling petrophysical properties of the facies at the core plug scale. All lithologies exhibit increasing permeability with increasing porosity and can be characterized as lying along the same general porosity-permeability trend. Clotted algal boundstones, pelodial packstone-grainstone, wackestones, mudstones, and shale generally have porosities of less than 10%. Absolute permeabilities are generally below 0.1 md and frequently below 0.01 md. The facies also exhibit high to very high irreducible water saturations (Swi), and effective hydrocarbon permeabilities at Swi are one to several orders of magnitude less than the absolute permeability values.

In contrast, laminated algal boundstones with abundant grains have porosities ranging from 10% to 30% and absolute permeablities ranging generally from 0.1 md to 1,500 md. Irreducible water saturations in these facies are related to permeability but are generally low. Effective hydrocarbon permeabilities range between 30% and 100% of absolute permeabilities. Early chert replacement, early and late dolomitization, and early to late brecciation and fracturing have variously created and destroyed porosity. These processes, in conjunction with depositional facies, have created a vertical herogeneity resulting in complex compartmentalization of Arbuckle Group strata.

While much attention has been directed previously at karst features, results from this study indicate that matrix properties also play an important and even dominant role in some reservoirs. Arbuckle strata have experienced pervasive but mostly non-fabric destructive dolomitization(s), allowing inference of depositional facies and the paragenetic sequence of events that affected these strata. The striking feature in the cores is the abundance (>50%) of matrix porosity (intercrystalline, moldic, fenestral, vuggy) throughout the length of the cores related to depositional facies, early diagenesis, and dolomitization, unrelated to the upper post-Sauk subaerial exposure surface.

The facies and paragenentic sequence of events described here are characteristic of most Arbuckle strata in Kansas. Although production strategies typically have been based on karst- controlled models associated with the post-Sauk unconformity, study of a dozen cores and reconnaissance of others in Kansas indicate that matrix properties unrelated to the unconformity are significant and may be the dominant control on reservoir properties and architecture. The relative lack of karst-associated fracture, breccia, and dissolution porosity in the cores was surprising, especially considering that the cores come from the flanks or tops of structural highs where karst processes would likely have been most extensive.

Arbuckle strata in Kansas comprise original shallow water subtidal to peritidal carbonate facies that have been overprinted by pervasive, but mostly non-fabric destructive dolomitization(s) and late diagenesis. Much of the matrix porosity (intercystalline, moldic, fenestral, vuggy) is associated with coarse-grained, laminated to bedded facies that are differentially cemented or with algal (stromatolitic) intervals that show differential porosity development likely due to differences in original texture (e.g., mud content) and early diagenesis (e.g., development of fenestral and vuggy porosity during early subaerial exposure). As evidenced by oil stains and (in many cases) a prolific production history, the intervals apparently are significant in their potential as reservoirs.

The regional stratigraphic and sedimentological framework of Arbuckle strata is providing an understanding of the relative importance of depositional facies, diagenesis, and unconformity-related karst processes for controlling reservoir architecture and properties in various structural settings. Integrated with quantitative petrophysical data for individual depositional facies and diagenetic features, the comprehensive framework will provide: (1) a predictive capability for identifying favorable reservoir facies that intersect the post-Sauk unconformity on structural highs; (2) improved ability to identify additional horizons deeper in the Arbuckle that have favorable reservoir potential; (3) quantitative data that can guide production strategies and determine if zones are best produced with vertical, horizontal, or target infill drilling; and (4) quantitative data that can be used in reservoir simulations to aid in determining production strategies.

Biographical Sketches:

Mark Steinhauff holds BS degrees in anthropology and geology, and MS and PhD degrees in geology. He completed internships with the California Division of Mines and Geology, Shell USA, and Exxon USA and gained more than six years of experience in the environmental industry before and after completing his dissertation at the University of Tennessee. During his tenure in the environmental industry he was employed as a hydrogeologist and later as risk assessment team leader at the Oak Ridge National Laboratory, responsible for managing risk assessments for the Portsmouth Gaseous Diffusion Plant in Ohio, and as an instructor with the University of Tennessee Evening School. He spent one year as carbonate sedimentologist at the Kansas Geological Survey before joining Exxon Exploration Company in 1998 where he has worked on regional stratigraphy in the Gulf of Mexico. His publications and presentations include topics on Miocene marine microfossils from Antarctica, stratigraphy and diagenesis of Paleozoic strata, and environmental risk analysis.

Evan Franseen received his BS, MS and PhD in geology from the University of Wisconsin-Madison. Since 1989 he has worked at the Kansas Geological Survey, University of Kansas, where currently he is an Associate Scientist in the Petroleum Research section. His research interests are in carbonate sedimentology, diagenesis and sequence stratigraphy and integration of seismic, ground-penetrating radar, geochemistry and modeling techniques to understand controls on sedimentary systems and reservoir character.

Alan Byrnes received his BS in geology from the University of Illinois at Chicago and his MS in geophysical sciences from the University of Chicago. He has been a research geologist at the Institute of Gas Technology, Marathon Oil Company Research Center, Core Laboratories, and Tetra Tech. He owned and operated GeoCore, a special core analysis laboratory, prior to joining the Kansas Geological Survey as a research geologist-petrophysicist in 1997. He presently does applied research in lithologic controls on petrophysical properties with emphasis on CO2-enhanced oil recovery, formation evaluation, reservoir characterization and modeling.

Jason Cansler received his BS in geology from Kansas State University in 1997, and is currently working on his MS in geology at the University of Kansas. While attending KU he also works as a Graduate Research Assistant in the Petroleum Research section at the Kansas Geological Survey. His specific research interests are in examining the paleogeomorphology of the pre-Pennsylvanian surface over the Central Kansas uplift.

Environmental / Engineering Dinner Meeting

Growth Faulting in Houston - an update

Abstract:

In the Gulf Coast region of Texas, over 200 faults are known or suspected to be active. Many of these faults, which cover an area from Conroe to the offshore Gulf of Mexico, are located in greater Houston.

Fault movements are relatively slow and earthquakes are nonexistent. A considerable body of work was published in the late 1970s and early 1980s mostly by the HGS, USGS, and NASA documenting the Houston area fault problem. Although no comprehensive detailed maps have been published, several regional maps have been, and they portray most of the major faults. This paper will present a summary of methods used in conducting Phase I and Phase II fault studies and provide examples of how several publicly-funded projects have dealt with potential fault movements. Examples of projects will include sanitary sewer crossings, an HOV overpass, and buildings crossing or in proximity to an active fault.

Predicting future movement of a growth fault is difficult withouthistorical data. It is also one of the questions most often raised by owners of properties and/or facilities on or near a fault line. Literature on previous fault movements is limited to several articles and MS theses of selected faults for relatively short periods of time. One of the most useful methods of documenting movement is the use of surveyed profiles across fault lines. Combined with historical data, such as the date that a particular section of pavement was installed, profiles can be used to provide a rough estimate of the historic fault movement rate.'

Mitigating fault impact is dependent upon the sensitivity of structures involved and the potential activity of the fault. In most cases, avoidance is recommended. Some projects or facilities may not require a Phase II fault study. For example, designing and placing a rigid pavement (e.g. concrete) across an active fault may not be as cost effective as periodic maintenance and repairs of asphalt pavement. In such a case, where the fault location can usually be identified within a few feet, Phase I may be the appropriate level of study.

For land development, if a fault can be identified early in the design stage, a fault hazard zone can usually be accommodated with drainage easements or open space. Where sensitive facilities, such as bridges, must be placed across a fault, care must be taken to place the foundations away from the fault plane and to accommodate some amount of horizontal displacement. Displacement is directly related to the fault dip angle and the angle of crossing of the specific structure.

Figures:

One View of fault damage on sidewalk of Hillendahl, looking west. Note the "bow" in the roof line of the building in the background. The fault passes through the center of the building.

Two Looking east from the west side of Hillendahl along the strike of the Long Point Fault. Car is crossing the fault scarp from downthrown to upthrown sides. Note angle of car relative to objects and structures in the background.

Three West side of building shown in Figure One. Note flexure of sidewalk adjacent to the "auto insurance" sign. Of interest in this photo is the four inches of horizontal separation displayed in the sidewalk adjacent to the newspaper stand. Dark area crossing sidewalk appears to be a 3-inch extensional crack between concrete slabs. The photo shows both downward separation and horizontal extension of the concrete sidewalk slab.

Biographical Sketch:

Eli Zlotnik is senior hydrogeologist with HVJ Associates in Houston, Texas where he is the environmental department manager. He joined HVJ Associates in 1992. Previously he was with Groundwater Technology, Harding Lawson Associates in Houston, and Arco Oil and Gas Co. in Denver and Dallas. He has been conducting environmental and geologic studies in the Houston area since 1987 and has conducted numerous Phase I and Phase II fault studies for public infrastructure projects and private developers.

He graduated from California State University, Northridge in 1978 and, following a brief stint as a mining geologist, went on to San Diego State University, where he received his MS in geology in 1981. His thesis was on the Cretaceous turbidite deposits that crop out in the coastal area of San Diego. He is a registered geologist in Florida and Wyoming and is a TNRCC CAPM.

International Dinner Meeting

"Libya: Petroleum potential of under-explored basin centers, a 21st century challenge"

Abstract:

Recoverable reserves in approximately 320 fields in Libya's Sirt, Ghadamis, Murzuq, and Tripolitania basins, exceed 52 billion barrels oil and 40 trillion cubic feet gas. The great majority of these reserves are located in the Sirt Basin, where there are about 250 discoveries with reserves of 45 billion barrels oil and 33 trillion cubic feet gas.

Approximately 80 percent of the reserves were discovered prior to 1970. Since then a less active and more conservative exploration effort has persisted. Complex, subtle and, in particular, deep plays were rarely pursued during the 70s and 80s because of a lack of definitive imaging technologies, limited knowledge of the petroleum systems, high costs, and risk adversity.

Consequently, extensive petroleum resources remain to be discovered in Libya. These resources will be accessible with the prudent integration of geological and geophysical knowledge, innovation, state-of-the art technology and computer power. For example, 3D seismic acquisition, sequence stratigraphic concepts, and other effective methods will be required.

Most of the undiscovered resources will probably be found in the vast, under-explored deep areas of the producing basins. These areas have rich, well-established petroleum systems. Six specific basin or trough centers, which are the subject of the paper, are exceptional in this regard. Three of the under-explored sectors are in the Sirt Basin, a Cretaceous to Paleogene rift basin. The Sirt Basin areas are: the south part of Ajdabiya Trough, the Maradah Graben the and south part of the Zallah Trough, including the Tumayam Trough. The other three subject areas are in western Libya: the Paleozoic age central Ghadamis Basin and central Murzuq Basin; and the extreme eastern part of the offshore Tripolitania Basin, a Mesozoic-Tertiary domain. These highly prospective basin sectors encompass a total area of nearly 150,000 sq. km.

Libyan petroleum potential is certainly not limited to the above under-explored areas. In all four of the producing basins, opportunities are far from exhausted. Considerable potential remains near to, and on trend with, the prolific producing fields in moderate to small, subtle structural and stratigraphic traps. Several sectors of the Cyrenaica Platform, in eastern Libya, are virtually unexplored. Also, the unexplored deepwater areas of the offshore Sirt Basin and Sirt Rise, and, further east, the offshore Derna and Benghazi basins cannot be excluded.

Donald C. Rusk, consulting geologist for international exploration, received a BA in geology from the University of Colorado in 1952. After 3 years of geological work in western Venezuela for Creole, he joined Pan American International Oil Company (Amoco). His 31 years of service with Amoco, which included 17 years at overseas locations, were exclusively in the international arena. For the past 10 years Mr. Rusk has worked as a consultant for numerous major and independent oil companies on a wide range of petroleum projects. During this same period he co-authored major geological and geophysical studies on Libya, Ecuador, Algeria and Syria.

In the capacity both as geologist and supervisor over his career, he has been active in basin and prospect evaluation, regional studies, operations and new venture matters in more than 150 basins in 55 countries.

Biographical Sketch:

Donald C. Rusk, consulting geologist for international exploration, received a BA in geology from the University of Colorado in 1952. After 3 years of geological work in western Venezuela for Creole, he joined Pan American International Oil Company (Amoco). His 31 years of service with Amoco, which included 17 years at overseas locations, were exclusively in the international arena. For the past 10 years Mr. Rusk has worked as a consultant for numerous major and independent oil companies on a wide range of petroleum projects. During this same period he co-authored major geological and geophysical studies on Libya, Ecuador, Algeria and Syria.

In the capacity both as geologist and supervisor over his career, he has been active in basin and prospect evaluation, regional studies, operations and new venture matters in more than 150 basins in 55 countries.

Poster One:

"Anadarko's Success Story in Algeria, more than 5 Billion Barrels in Place in the TAGI Reservoir"
by Pablo Eisner and the Anadarko Algeria Team

Poster Two:

"The Tectonic Evolution of the Atlas Mountains, North Africa"
by Weldon H. Beauchamp,Atlas Exploration and Production Company

Poster Three:

"NEW INSIGHTS ON LIBYA'S PETROLEUM POTENTIAL FROM SATELLITE DATA."
Nigel Press, Mike Oehlers, Robin Cleverly and Alan Williams; NPA Group, UK.

There is a limit to how much exploration judgement can be made in a mature area from the re-analysis of old data without the addition of something new. Often satellite is the only source of new data in areas that are politically or geographically inaccessible Satellite data provide a very cost effective tool to update older existing mapping, add structural detail and investigate possible seepage patterns, both on- and offshore. Comparing these results to other existing data may then reveal some interesting new exploration insights which have yet to be tested. The results can provide an important input to Risk Segment Analyses and significantly change perception of YTF (yet to find) estimates.

The poster illustrates this concept with respect to the entire country of Libya. We have made full resolution (30m.) digital mosaic of Landsat TM imagery which has been interpreted photogeologically for both stratigraphic/lithologic and structural features. The result provides a more detailed geological map than those previously published and a better understanding of the basin architecture and it's surface expression. The interpretation identified a very large number of surface features that resemble similar structures that have proved to contain signifcant hydrocarbon accumulations. When these new interpretations are overlain with depth to basement derived from mag/grav data, hydrocarbon play maps and known fields and well locations, a number of apparently untested exploration targets are immediately apparent. Furthermore, mapping of the areas obscured by sand shows several broad zones where targets might continue beneath the sand cover.

We have used several other techniques to examine newly identified areas in more detail in Libya. These include high-resolution imagery to create and vizualize digital elevation models for mapping section thickness and planning seismic, the use of dual frequency satellite radar to achieve penetration of thin surficial cover and map shallow buried structure, thermal and spectral techniques to search for secondary signs of hydrocarbon microseepage zones at the surface onshore and the use of satellite radar to detect sea-surface slicks resulting from seepage offshore.

Poster Four:

"Libya Country Screening for Petroleum Exploration."
Martin Insley, Adrian Huntley, David Peace, Ted Snedden, NRSC Exploration Services.
Dr. Huntley and Mr. Peace are located at NRSC's offices in Farnborough, England. Dr. Insley is located in NRSC's offices in Barwell, England. Mr. Snedden is NRSC's representative in Houston, Texas.

Vendor Information:

GETECH Global Gravity and Magnetic Services
Libya Basin Analysis Study -The tectonic evolution, basin history and hydrocarbon potential of Libya
In association with Mr Adil Jawzi and Associates See www.getech.leeds.ac.uk/data/libya_study.htm for more info.

Lynx Information Systems Ltd.
Live GIS Demo of Lynx Exploration Adviser Project for Libya
See www.lynxinfo.co.uk/libya.htm for mor einformation.

Emerging Technologies Dinner Meeting

"Geovolume visualization interpretation: Components and techniques"

Abstract:

New visualization technology has created a paradigm shift in the workflow of 3D seismic interpreters. This change in workflow is answering the growing demand for improved accuracy, cycle time and cost. The geovolume visualization interpretation (GVI) components allow interpreters to implement techniques that have previously not been possible. Four main components make up geovolume visualization interpretation: recognition, color, motion, and isolation. Recognition is essential to an accurate interpretation and is dependent on the ability of the interpreter to process data in a method that will separate an important geologic event from surrounding data. Color allows scanning of large volumes of data, using color as a way to stimulate the brain through memory, attention and experience. Motion is the ability to move an object in a manner appearing continuous to the eye of the interpreter, while synchronizing with control movements. Isolation is the determination of a set of viewing parameters that will separate an event from its surroundings. Understanding and combining these components in various techniques is essential to achieving a

GVI workflow that identifies geologic events. The presentation involves both slide and live demonstrations of visualization components and techniques.

Figures:

Figure 1.

A seismic amplitude volume, interpreted along with three interactively processed seismic attribute volume (Instantaneous Amplitude, Dip Semblance and Phase). Each seismic attribute volume is processed to enhance the recognition of a specific event or feature in the data, in this case, a stream channel.

Figure 2.

This figure shows the use of volume rendered probes to locate a channel. The left probe is on the up-thrown side of a fault and the right probe is on the down-thrown side. The occlusion of one probe over another gives a depth perspective to the two probes, and shaving ads contrast and texture to the channel. The use of volume rendering isolates the event of interest.

Figure 3.

Both color and transparency further enhance the recognition and isolation of the anomaly identified in Figure 1 and 2.

Figure 4.

Two geostatistically derived volumes. (sand vs. shale, and steam). The center volume is a combined rendering of both. The cross-section view is shown in back and the volume rendered view is shown in front. This technique allows the interpreter to visualize steam-penetrated sands. Displaying the steam volume at different time steps shows which sands take on steam the fastest. The co-rendering technique illustrated here shows the use of visualization technology to fully integrate all of the diverse data types available in an interpretation project.

Biographical Sketch:

Tatum M. Sheffield is a Geovolume visualization interpretation (GVI) specialist with Magic Earth LLC. He holds a BS in geology from Lamar University, 1979, and an MS in geology from the University of Texas at El Paso, 1981. He joined Texaco in 1981 and worked a variety of interpretation projects resulting in the drilling of over 50 exploration wells. In 1997, he joined the Upstream Technology department of Texaco in Houston where he participated in the development and application of new visualization technology to 3D exploration. During his tenure at Texaco, he received the Texaco Denver Outstanding Contributor Award 1987, Texaco Star Quality Award 1993 and the Texaco Outstanding Partner Satisfaction Award in 1998. He joined Magic Earth in January, 2000.

HGS Lunch Meeting

Sequence stratigraphic framework and depositional variations of Miocene lowstand systems tracts, South Louisiana

Abstract:

Facies of Miocene lowstand systems tracts comprise a large portion of the remaining exploration potential for deep untested objectives in southwest Louisiana. The complex and highly variable section is contained in 22 major depositional sequences deposited from 21.9 to 7 million years ago. Each sequence ranged in duration from 0.5 to 1.5 million years. Regional well log, seismic, and biostratigraphic correlation and mapping of the sequence stratigraphic framework defines the occurrence and extent of lowstand facies that filled intra-slope basins across south Louisiana's coastal zone.

From oldest to youngest, the sequences encompass the Cristellaria R. through Cristellaria K. biozones. In onshore and state water areas, 14 sequences contain regionally correlative lowstand systems tract components. Amalgamated, massive turbidite facies of basin floor fan complexes are not recognized in intra-slope basins in association with rapid depositional cycles. Deepwater fan and channeled levee facies of slope fan complexes and deltaic facies of prograding complexes are well-developed throughout the early and middle Miocene section. Late Miocene lowstand deposits are best developed in the offshore trend.

Syndepositional fault movement and salt withdrawal controlled thickness trends, facies patterns, sandstone content, and the position and trend of the shelf/slope break. Sandstone-rich basin floor fans, slope fans, and prograding deltaic complexes are best developed in intraslope basins where paleobathymetric confinement and accommodation were greatest.

Biographical Sketch:

Barbara Luneau is a principal consultant with Schlumberger Holditch-Reservoir Technologies. She has worked as a geologist in the Reservoir Technologies group for the last 8 years, participating in regional stratigraphic studies and reservoir modeling.

Barbara holds an MA in geology from the University of Texas at Austin, and a BA in geology from the University of Vermont. She has worked at the Texas Bureau of Economic Geology, RPI International, and Intera Information Technologies.