"Classification of syndepositional structural systems, northern Gulf of Mexico"
Date: Monday, February 7, 2000
Place: Westchase Hilton, 9999 Westheimer
Time: 5:30 Social 6:30 Dinner
Syndepositional structures form in response to sedimentary loading. Because deltaic and turbidite complexes, which comprise the sediment load, are on a size scale of tens of miles, then the resultant structures must be of similar size. We have come to recognize that hydrocarbon trapping structures are actually quite small components of larger-scale structural systems. We define syndepositional structural systems as complexes comprised of a number of different but genetically related types of structures that occur in generally repetitive and predictable patterns, linked causally with reservoir distribution and the nature of the unstable substrate being loaded. There are three primary types of syndepositional growth-fault systems observed in the northern Gulf of Mexico: shale-based detachment fault systems, salt-withdrawal mini-basin systems, and salt-based detachment (Roho) systems.
Shale-based detachment fault systems are strike-linear gravity slides. Characteristically they exhibit a highly listric master expanding fault, a rollover anticline, a planar synthetic fault, a syncline, a planar antithetic fault, and a horst block. Compressional toe folds may be visible, but are usually obscured by younger systems. The listric faults share a common sole plane, most often a locally thick transgressive shale. Delta progradation stalls at the head of the system and sands tend to be stacked in the rollover, or are conveyor belted down dip along the fault ramp to form rotated wedges while the synclinal region is typically filled with prodelta slope facies
Salt-withdrawal mini-basin systems consist of large (12-20 miles), elliptical withdrawal basins. They consist of a deep turtle structure, a syncline, and a series of subsidiary faults and diapirs that outline the basin s margin. In the slope region, tabular salt may obscure all or part of the underlying mini-basin. The overall geometry of the mini-basin, and the nature of the sedimentary fill within the basin vary considerably depending on whether the mini-basin was loaded primarily in a shelf or slope environment. In shelf loaded mini-basins, characteristically the shelf margin stalled along the basin-rimming hinge faults resulting in a section of stacked deltaic sands and shales overlying massive prodelta shales.. In slope loaded mini-basins turbidite ponding is more or less continuous so long as there is salt withdrawing from the basin
Salt-based detachment faults or Roho are combination gravity slide and salt evacuation structures. Roho systems undergo a two phase evolution. Evacuation of salt from a starved mini-basin first forms an extensive salt wing, which subsequently is remobilized by deposition onto the wing of upper slope and outer shelf sediments. This deposition initiates formation of a series of highly listric down to basin faults that sole into remnant salt resulting from salt evacuation into, primarily, the edges of the wing. The growth faults of Roho systems are generally a series of nested horseshoe-shaped faults along which deltaic sands and shales tend to be stacked . These listric normal faults grade laterally into strike slip fault zones and dip-oriented salt diapirs and the system has a complex toe thrust zone of salt and compressional structures at the down dip edge of the salt wing. Because of the two phase evolution, Roho separates two regions of discordant structure with geopressured slope section below and hydropressured shelf stratigraphy above.
Poster Session:
Classification of Structural systems and Tectonic Provinces of the Gulf of Mexico by John Karlo and Bob Shoup
Biographical Sketch:
Dr. John F. Karlo
Has worked 20 years for differing divisions of Shell both domestically and internationally. Building on a background in tectonics and structural geology (Phd S.U.N.Y. Buffalo and MA Univ Missouri, Columbia), his career has encompassed both geologic scales of regional synthesis and play definition, and prospect evaluation as these are applied to greenfield exploration. He is an expert on the geologic architecture of passive margins, particularly those with mobile substrates. Most recently he has been doing turbidite exploration in deep water basins of India, Brazil and Nigeria.
Robert C. Shoup was born in St. Paul, Minnesota, where he attended Winona State University, receiving a B.A. in geology in 1978. After receiving his B.A. degree, Bob attended the University of Oklahoma in Norman, receiving an M.S. in geology in 1980.
Upon graduation, Bob was employed by Shell, mainly doing geological evaluation of the South Texas offshore. In 1983, he became a member of a team evaluating the tectonic and stratigraphic architecture of the Gulf of Mexico. After working onshore and international, Bob was transferred to China in 1993 where he was offshore team leader. At the end of 1995, he was transferred back to New Orleans, overseeing generation and evaluation of prospects in the eastern deep water of the Gulf of Mexico. After 18-plus years with Shell, Bob retired and is now working in Houston with Samson Offshore where he oversees all Gulf of Mexico exploration.
Bob is a Certified Petroleum Geologist and an active member of AAPG, HGS and NOGs. He has also been very active in the DPA, serving as editor of the DPA Correlator in 1993–1994, DPA Advisory Board member for the Gulf Coast, 1998–2001, DPA vice president in 1999, and vice chairman of the DPA New Orleans Year 2000 National Convention. In addition to this service, Bob has been a co-author or senior author of several publications and conducted short courses for the AAPG.
"The Katy Prairie: past and present "
Date: Wednesday, February 9, 2000
Place: Jalapeno's - 2702 Kirby (at Westheimer)
Time: 6:00 - 7:00 PM - Dinner; 7:00 - 8:30 PM Lecture, Career Opportunities, and Networking
Abstract:
The Located in the Coastal Prairie region of Texas and Louisiana, which is considered to be a southern extension of the tallgrass true prairie, is the relatively small and locally named Katy Prairie. It was originally about 500,000 to 750,000 acres in extend. Currently only about 200,000 acres are left undeveloped. The Coastal Prairie region, in general, and the Katy Prairie specifically, is a diverse mosaic of emergent wetlands, upland grasslands, and riparian hardwoods. Two unique soil features are found on the Katy Prairie. These are mima mounds, associated with sandy soils found inland, and gilgai, which are associated with the clay soils toward the coast. Both of these features contribute to the diversity of the region by providing topographic relief in a relatively low-relief landscape. In many cases, an elevational gradient of only a few inches will produce a plant community shift from wetland dominants to purely upland plant species.
More recently, this natural prairie wetland system has been replaced with an artificial wetland system, rice farming. The shift from a natural to an artificial system has actually contributed to an increase in the diversity and numbers of waterfowl found on the Katy Prairie. The Katy Prarie is home to an estimated 350 to 400 species of resident and migratory birds, along with 110 species of mammals, reptiles, and amphibians.
Currently the remaining Katy Prairie is under strong devlopment pressure. Houston is expanding westward and development is inevitable. The Katy Prairie Conservancy hopes to acquire and protect from development 30,000 to 50,000 acres through the purchase of property and the use of conservation easements. Property owned and managed by the Conservancy will be maintained to rep4resent the diversity of uses, current as well as historical, found on the Katy Prairie. Activities willinclude farming, cattle grazing, wetland restoration through mitigation projects, and prairie restoration. It is the goal of the Katy Prairie Conservancy to protect and ultimately provide access to an important historical, cultural, and natural resource.
"Keys to exploration: lake-basin type, source potential, and hydrocarbon character within an integrated sequence-stratigraphic-geochemical framework."
Date: Monday, February 21, 2000
Place: Westchase Hilton, 9999 Westheimer
Time: 5:30 Social 6:30 Dinner
Abstract:
Rocks associated with lakes probably account for more than 20% of current worldwide hydrocarbon production (Kulke, 1995; Britannica Yearbook, 1999), and lacustrine organic-rich rocks are significant sources of these hydrocarbons. Lacustrine sources and reservoirs are important in many areas of current and future exploration opportunities: Africa, South America, southeast Asia, China (Hedberg, 1968; Powell, 1986; Smith, 1990; Katz, 1995).
We have developed the concept of lake-basin type, which is useful for sorting out the complexities of lacustrine deposition to derive a predictive framework (Carroll and Bohacs, 1995, 1999). Three lake-basin types are recognized from recurring lithofacies associations and stratal stacking patterns at scales of meters to dekameters, based on numerous observations of lake strata from Cambrian to Recent age.
Lacustrine strata record the integrated history of lake hydrology arising from the interaction of potential accommodation and the supply of sediment+water. These two factors together govern the major stratigraphic features of ancient lake deposits, and, in conjunction with lake ecology, geologic age, basin shape, and drainage-basin lithology, exert a strong influence on source character, reservoir-rock distribution, and hydrocarbon potential.
The three lake-basin types are named overfilled, balanced-fill, and underfilled, based on the interpreted relation of potential accommodation and sediment+water supply (Figure 1). Expression of parasequences and sequences ranges from very similar to shallow-marine sequences in some overfilled lake basins to very different in underfilled lake basins (Table 1). Balanced-fill lake systems contain the most prolific lacustrine source rocks and beneficent facies juxtapositions for hydrocarbon accumulation, based on observations of lacustrine strata of many different ages and basins (e.g.: East Africa Quaternary; U.S.A. Tertiary; Africa, Brazil, and China Cretaceous).
Lake-basin type commonly evolves among the three end members on a variety of time scales due to changes in climate or tectonic subsidence, commonly recorded within a single formation. Different lake types can also coexist in adjacent basins. Note that the lake water depth and overall thickness of lacustrine strata are a function of both total subsidence and sediment+water supply, and are not necessarily related to lake-basin type.
This lake-basin-type approach offers significant advantages over previous models based on paleoclimate alone, and allows lacustrine source rocks to be genetically linked with reservoir and seal lithofacies through sequence stratigraphy. However, sequence-stratigraphic models specific to each type of lake basin are necessary because, unlike most marine systems, the supply of sediment in lake basins commonly can be closely linked to the supply of water and lake level. The integrated framework provides an approach to predicting hydrocarbon character from stratigraphic information or lake-strata character from geochemical data and suggests strategies for successful exploration and exploitation. This framework also enables one to appreciate and begin to comprehend small-scale variations and complexities of lake strata within a bigger picture.
References:
Carroll, A.R., Bohacs, KM, 1995, A Stratigraphic Classification of Lake Types and Hydrocarbon Source Potential: Balancing Climatic and Tectonic Controls. First International Limno-geological Congress, Geological Institute, University of Copenhagen, Denmark, August 21-25th, 1995, p. 18-19.
Carroll, A.R., K.M. Bohacs 1999, Stratigraphic classification of ancient lakes: balancing tectonic and climatic controls, Geology v. 27, p. 99 - 102. Hedberg, H.D., 1968, Significance of high-wax oils with respect to genesis of petroleum: American Association of Petroleum Geologists Bulletin v. 52, p.736-750.
Katz, B. J., 1990. Lacustrine Basin Exploration-- Case Studies and Modern Analogues: American Association of Petroleum Geologists Memoir 50, 340 p. Kulke, H., 1995, Regionale Erdöl- und Erdgasgeologie der Erde: Berlin, Gerbrüder Borntrager, 2 volumes.
Powell, T.G., 1986, Petroleum geochemistry and depositional setting of lacustrine rocks: Marine and Petroleum Geology v. 3, p. 200-219.
Smith, M., 1990, Lacustrine oil shale in the geological record, in B.J. Katz, Lacustrine Basin Exploration-- Case Studies and Modern Analogues: American Association of Petroleum Geologists Memoir 50, p. 43-60.
Biographical Sketch:
Kevin M. Bohacs is a sedimentologist and stratigrapher with the Petroleum Geochemistry section of Exxon Production Research Company in Houston, Texas. He received his B.Sc.(Honors) in geology from the University of Connecticut in 1976 and his Sc.D. in experimental sedimentology from M.I.T. in 1981. At EPR, he leads the application of sequence stratigraphy and sedimentology to organic-rich rocks from deep sea to swamps and lakes, in basins around the world. As a Research Associate, his primary focus is to keep the geo- in geochemistry, integrating field work, subsurface investigation, and laboratory analyses. He has written numerous papers on the stratigraphy and sedimentology of mudrocks and hydrocarbon source rocks. He was co-recipient of the AAPG Jules Braunstein Memorial Award for best poster session paper in 1995 for work on coal sequence stratigraphy and the AAPG award for best international paper in 1998.
PGS Reservoir - Brazil Services
Geology, geophysics and engineering, including:
Offshore basin reports
Bibliographic reference list
Stratigraphic services
Seismic interpretation
Technical Poster One:
"Paleosols as Top Seals in Rift Basin Petroleum Systems"
William C. Dawson and William R. Almon, Texaco Upstream Technology, Houston, TX
Paleosols, sampled from conventional cores of nonmarine lithofacies successions in SE Asian Tertiary rift basins, have been analyzed (mercury injection capillary pressure) to determine sealing capacity. Mercury injection data are supplemented with petrographic, SEM, and XRD analyses to document the texture and mineralogy of the paleosols. These paleosols range from fine-grained argillaceous sandstones to silty claystones. Detrital quartz ranges from 45 to 77 percent. Illite is the dominate (62%) clay constituent. Kaolinite (15 to 30%) and authigenic siderite (5 to 10%) are accessory components. The clay matrix is densely compacted, cemented with quartz and/or carbonates, and partly recrystallized. Porosity ranges from 1.5 to 9.7 percent, and permeability varies from 0.200 md to 0.007 md. All samples exhibit well-developed mega- and microscopic pedogenic features. These paleosols are interstratified with fluvial, lacustrine, and estuarine (incised valley) lithofacies. Thick regionally extensive paleosols occur along some sequence boundaries.
Mercury injection data indicate that the paleosols are good to excellent top seals. Calculated column heights range from 470 to 4,610 feet (oil) and 570 to 5,860 feet (gas). The excellent sealing capacity is related statistically to the degree of quartz and carbonate cementation, total clay content, and position within the soil zone. C-horizons form excellent top seals (0.983 correlation coefficient). B-horizons are very good top seals, but offer less overall sealing capacity (0.832 correlation coefficient) than C-horizons. Where breached by erosion (fluvial/estuarine incision) or faulting, hydrocarbons can leak across paleosol horizons. Paleosols associated with sequence boundaries may influence hydrocarbon migration pathways.
Technical Poster Two:
Tectonic and sequence stratigraphic controls on facies distribution in a deep, balanced-filled lake: seismic and dropcore evidence from Lake Malawi, East Africa
by Jack E. Neal, Kevin M. Bohacs, David J. Reynolds, ExxonMobil Upstream Research, and Christopher A. Scholz, Syracuse University
Technical Poster Three:
Examples of non-marine rift basin drainage systems and lacustrine shorelines from satellite imagery
by David J. Reynolds, ExxonMobil Upstream Research
Technical Poster Four:
Facies architecture and sequence stratigraphy of gravelly and sandy Lake Bonneville deltas, northern Utah and southern Idaho
by David R. Lemons, ExxonMobil Production
"The English Basin, Kentucky: a seismic study of the relationship between a Proterozoic basin and subsequent Paleozoic structure and strata"
Date: Monday February 28, 2000
Place: Westchase Hilton, 9999 Westheimer
Time: 5:30 Social 6:30 Dinner
Abstract:
The English basin is interpreted as a Meso-, Neoproterozoic and Cambrian-age depocenter, forming a portion of the East Continent rift complex in areas of Kentucky and Indiana. Both proprietary and published seismic sections show a complex structural depocenter with a depth to crystalline basement exceeding 6100 m. Two boreholes penetrate the Proterozoic sequence of the depocenter and have strata similar in lithology to both the Precambrian Middle Run Formation (Centralia Group) described in Ohio and Kentucky and low-density clastic sediments of the overlying Marengo Formation.
A newly discovered thrust-fault system in the lowermost Mesoproterozoic-age Centralia Group is referred to as the Hoosier Thrust Belt and corresponds to the positions of overlying Paleozoic fault systems, pinnacle reefs, and shallow petroleum production. Above a major angular unconformity truncating Centralia strata, the newly described clastic sediments of the Marengo Formation are locally deposited within the English basin.
The eastern basin margin is defined by the Louisville uplift, a 600 m.y. old foreland-style basement thrust with approximately eight kilometers of uplift. Paleozoic strata at the margins of the uplift are cut by a series of shallow fault systems, currently being developed for fractured shale reservoirs of Devonian age.
Extending north of the bounding feature is the Mt. Carmel Uplift. Features interpreted on seismic data are flanking Proterozoic basins, forced folds, and complex faulting associated with gas storage fields and Ordovician oil production. Petroleum fields along the margins of the basin appear to be associated with remobilization of bounding fault systems that have controlled the structural and stratigraphic development of the area.
Potential field data tied to regional seismic reconnaissance of the basin illustrate the lateral geometry of the basin and underlying thrust belt system. Epicenters of earthquakes recorded in the area may be localized along detachment structures within the Precambrian thrust belt, relating contemporary seismicity to the current east-west horizontal maximum principal compressive stress along the Hoosier thrust belt.
Biographical Sketch:
T. Joshua Stark received his B.S. in geology from the University of Missouri at Columbia in 1980. He began his oil field career as a mudlogger, working the Rockies, Williston and Permian basins. Since then, he has held positions with various companies working as a senior exploration geologist in the Illinois, Forest City, Appalachian, Michigan, Santa Maria, and San Joaquin basins, as well as mid-continent and international regions. Currently, Josh is a senior exploration geologist with Aurora Energy Ltd. of Tulsa, OK, where he is working the Illinois, Appalachian and Michigan basins. Josh received the A.I. Levorsen Award for his presentation regarding the tectonic history of northwestern Ohio at the 1998 AAPG Eastern Section Meeting. He is a member of the Indiana/Kentucky Geological Society and AAPG, and has authored or co-authored numerous publications on rift systems and the geology of the midwest.
"Big Gas in the Rockies"
Date: Wednesday February 23, 2000
Place: Hyatt Regency Downtown 1200 Louisiana
Time: 11:15 social, 11:45 lunch
Abstract:
In the past fifteen years, technology has struggled in the battle to exploit more restricted and difficult-to-extract parts of the resource base. This is graphically shown on a gas resource pyramid. In the past five years, technology has been winning the battle, resulting in the discovery and exploitation of at least five giant fields (one oil and four gas) in the Rocky Mountains.
The greater Rocky Mountain petroleum province contains a large number of high potential, unconventional, Cretaceous and Tertiary, oil and gas plays.
Many thousands of feet of interbedded source rock and tight sand potential reservoir rocks are currently in the "kitchen" (within the gas- generating window).
One gas field, with an estimated ultimate recovery of between one and five TCF, is a sweet spot in a basin-center gas deposit and will be discussed in detail. Recognizing similar sweet spots with geophysics will play a large role in future discoveries. Another field was discovered under a thrust fault. New hydraulic fracturing technology has been important to the success of both fields.
Three other giant fields will be discussed along with another potential giant accumulation in a basin-center oil deposit.
Biographical Sketch:
Dr. Thomasson received undergraduate and masters degrees from the University of Missouri and a Ph.D. in geology from the University of Wisconsin in 1959. He formed Thomasson Partner Associates, Inc., in 1990 after 17 years with Shell Oil Company. During his tenure with Shell, he was manager of various divisions including Geologic Research; the Texas, Louisiana and Atlantic Offshore Division; Forecasting, Planning and Economics (in the US); and Strategic Planning for Shell International in London. This gave him a broad socio-political-economic business perspective. His last position was as chief geologist for Shell Oil USA.
Dr. Thomasson is on the board of trustees of the American Geological Institute Foundation, gives lectures yearly at various universities in the US, and was a 1987-1988 distinguished lecturer for the AAPG on stratigraphic geophysics in carbonates. He received the Distinguished Service award from the AAPG in 1995, the Distinguished Alumnae award from the University of Wisconsin, and, this coming spring, will receive the Distinguished Alumnae award from the University of Missouri. He is currently president of AAPG.
TECH 2000 & Prospect Expo
Location: Rose Garden Center in Tyler, Texas
Contact: For more information, contact TECH 2000 & Prospect Expo, P.O. Box 216, Tyler, Texas 75710, visit the East Texas Geological Society's website at www.tyler.net/etgs , or send e-mail to: jlbedfo@ibm.net , jefflauman@pidwights.com, or mjggallag@aol.com
The Prospect Expo provides a venue to display prospects and acreage and allow companies new to East Texas to introduce themselves to the local oil and gas community. Are you interested in certain types of prospects or acquisitions? ETGS invites you to set up a booth and let the industry know.
Exhibition booth space is available for $125 per 10 x 6 ft. booth. Registration begins at 9:00 a.m. at the Tyler Rose Garden Center, 420 South Rose Park Drive, Tyler, Texas 75702.