March, 2002
HGS Meetings

HGS Environmental / Engineering Dinner Meeting

" QA/QC Requirements for Laboratory Analysis under the Texas Risk Reduction Program"

Abstract:

Ms. Lynch will compare the environmental data reporting requirements that are required under the TRRP program with the standard requirements that have been required in the past. She will discuss TRRP acronyms and how they relate to the data in your report. She will also summarize the key issues that should be discussed with the laboratory prior to project initiation to ensure that the data meet TRRP requirements.

Biographical Sketch:

Ms. Lynch is Senior Project Manager and Technical Consultant for SPL, Inc. Ms. Lynch obtained a BS Degree in biology in 1970 from Juniata College in Huntingdon, Pennsylvania and has over 30 years of experience in the environmental laboratory industry. During this time, she has held numerous technical, quality assurance, and customer support positions. Currently, Ms. Lynch manages TRRP projects and any project that requires reporting for data validation

HGS International Dinner Meeting

"Global Geomorphic Survey of Large Modern Fans: Distribution and Exploration Implications"

Figure One: Space Shuttle view of Northwest Botswana

Abstract:

Large modern fluvial fans are partial cones of sediment, each fan generally formed by a single dominant river. These features display gentle slopes (compared with small alluvial fans) and their apices are tied to mountain fronts or low scarps. Large fans are mesoscale continental sedimentary systems (radii arbitrarily defined as >100 km) barely recognized in geological literature, mainly because they are not readily visible on the ground or from low-altitude photographs because of their great size and gentle slopes. Space Shuttle and International

Space Station photographs (see figure 1), supported by 1:1,000,000 maps, reveal basinal geological settings with relatively young sediments and distributary drainage in many parts of the world, leading to the identification of 96 large fans. Large fans appear on all continents between 55N and 55S, which constitutes our survey area. Fan areas range between ~7000 and 210,000 km2. Most radii (90%) fall between 100 and 300 km. Fifty-eight percent lie in foreland and peripheral basins; 39% lie in cratonic settings.

The remaining 3% occur in rifts and intra-orogenic settings. Asia displays the largest number of modern large fans and North America the smallest number. Large areas of nested fans occur in Australia and Africa. The largest group of contiguous fans occurs in South America, from northern Bolivia to central Argentina where the basin between the Andes Mts. and the Brazilian craton is entirely occupied by seventeen fans, covering ~750,000 km2. Large fluvial fans are thus a significant feature of the global landscape, and probably have been so throughout much of Earth's history.

Understanding the distribution of large modern fans may help direct exploration for such features in past landscapes. Large modern fans may also provide models for detailing the architecture of paleo-fluvial reservoir systems. For example, the early Paleozoic oil and gas reservoirs of North Africa accumulated in settings which may have been analogous to the modern foreland basins of Central Asia and India. The large fan analog may also prove appropriate for the Witwatersrand basin of South Africa.

Biographical Sketch:

Justin Wilkinson trains astronauts in earth science and geography at the Johnson Space Center in Houston and conducts research using Space Shuttle photos. Born in South Africa he obtained his Bachelors (with honors) and Masters degrees in Physical Geography from the Johannesburg University. After a year as Chairman of the South African Voluntary Service, which built schools and clinics in rural communities in and around South Africa, he came to the USA in 1976 to the University of Chicago for doctoral study. His dissertation on landscape evolution and uranium mineralization in the central Namib Desert has been published in book form.

After three years teaching geography back at his alma mater in Johannesburg (1985-1988), and after becoming a US citizen in 1987, he immigrated back to the USA to take a position training astronauts in earth science and geography at the Johnson Space Center in Houston with Lockheed Corporation.

The study of a new database of Space Shuttle photos has resulted in a series of research initiatives-on inland deltas worldwide, involving travel to South America; on fish evolution dynamics (related to inland deltas); and on worldwide dust movement and dust sources. With astronaut Jay Apt, Justin co-authored the book "Orbit," a coffee table collection of Space Shuttle photos of the Earth. "Orbit" has run to three printings since it was published in 1996, and now appears in ten languages. Justin Wilkinson is the main author on a new book, "Costa Rica From Space", due to be launched in Costa Rica in April this year.

Two Texan children aged 13 and 9 have based the Wilkinsons firmly in Houston. Justin enjoys traveling, sailing and reading history.

He can be contacted at jwilkin1@ems.jsc.nasa.gov

HGS Lunch Meeting

"Evolution and High Dissolution Porosity of Woodbine Sandstones in a Slope Submarine Fan, Double A Wells Field, Polk County, Texas-A Deep Water Gulf of Mexico Model Onshore"

Figures: Note: The figures for this article did not transfer well from the Bulletin. To see the figures, please look at them in the Bulletin.

Abstract:

The subject field, a gas condensate giant located 75 miles NE of Houston, Texas (Figure 1) will eventually produce close to half a TCFG and 20 MMBC. The gas is trapped in lenticular sandstones that pinch out updip or have reduced permeability along thinned edges. Buried nearly 14,000', the slightly overpressured (0.7 gradient) fine-grained quartz sandstones have unusually good reservoir quality (cover inset, Figure 5), up to 23% porosity and 1 darcy permeability.

The sandstones are the terminal fill of a submarine canyon, initially 700-800' deep and 4 1/2 miles wide (Figure 2), which probably resulted from gravitational failure of oversteepened, progradational shales, seen as clinoform reflections on dip seismic lines, above the buried Sligo (LK) shelf margin (Figures 2, 3). The clinoform sequence is overridden by landward, onlapping deposits of a major marine transgression (late Cenomanian- Turonian) consisting of the Woodbine sandstone sequence, thin Rapides shale, and Austin chalk. As shown in Figure 3, the Woodbine sandstones, comprising the basal member of the transgression, are considered to be contemporaneous with and connected to producing sandstones of updip fields.

Sandstones of the submarine fan are encased in organic-rich source rocks including interfingering and underlying Eagle Ford shale, overlying Rapides shale, and basal Austin chalk. The organic content level of the shales has been established by previous workers, and the basal Austin chalk lime mudstone is a well-known producer from fractured reservoirs in the area (Brookland Field). The source rocks at Double A Wells Field are presently discharging gas at a temperature of 325-350° Fahrenheit.

The exceptional reservoir quality of multiple sandstones at Double A Wells Field (Figure 4) involves the early emplacement of pore-filling calcite cement after incipient quartz overgrowths, followed by cement dissolution by acidic waters during deeper burial. Note the calcite cement (orange) undergoing dissolution in the center of the cover photo. Acidic waters containing dissolved CO2 (carbonic acid) are postulated from two sources:

  1. organic-rich proximal source rocks; and
  2. inorganic chemical reactions of kaolinite with other minerals in very thick, hotter shale sections downdip, connected to field reservoirs by sandstone “pipelines”. The latter inorganic source is favored to supply the greatest volume of acidic waters needed for cement removal. Both the organic and inorganic sources have been documented by geochemists.

After cement dissolution the restored, born-again “surrogate” pores, mimicking early primary porosity, were invaded by oil (left as part of the black stain around grains, cover inset, Figure 5) then replaced by gas with increasing burial temperature. The gas contains 4 to 6% CO2.

Hopefully, the geological model presented here, combined with 3-D seismic data, will lead to the discovery of other Woodbine sandstone “sweet spots” containing future giants waiting to be found in this heavily explored trend.

Acknowledgements

I wish to gratefully thank Dr. John T. Smith, retired “Professor Emeritus” formerly of Shell Development Company, who spent 35 years working on geochemical problems related to oil and gas exploration. John patiently helped me to understand the role of circulating subsurface fluids involved in pore preservation and destruction. Appreciation is also extended to Dr. Michael Lloyd, likewise retired from Shell and now President of Roxanna Petroleum, who assisted in the same capacity. Many thanks are also due Tom Carter, CEO of Black Stone Energy, the company that discovered Double A Wells Field, for permission to use the data presented in the paper and talk.

References Available Upon Request.

Biographical Sketch:

Fred L. Stricklin, Jr. graduated from Louisiana State University just after the middle of the last century with a PhD in geology. After working 21 years with Shell as a research and exploration geologist, achieving the rank of Senior Staff geologist, Fred left Shell during the “Great Boom” of the 1970s to become an independent geologist. For the past 21 years, he has worked primarily conducting exploration analyses of Texas oil and gas trends for sale to industry under his company names of Exploration Trend Analyses and Wilcox Exploration Enterprises.