Tue, Sep 12|
FWGS September Luncheon
Join us for a luncheon and talk at the Fort Worth Petroleum Club. John Holbrook of Texas Christian University will be our speaker. Quantifying and qualifying reservoir characteristics and processes for upper-flow-regime-dominated river systems using the Triassic Dockum Group of West Texas.
Time & Location
Sep 12, 11:30 AM – 1:00 PM
Petroleum Club, 40th Floor, 777 Main St, Fort Worth, TX 76102, USA
John Holbrook is a Professor in the Department of Geological Sciences at Texas Christian University. He previously served as a Professor at University of Texas at Arlington and Southeast Missouri State University, and has held adjunct/guest professor positions at Enugu State University, Nigeria; St Petersburg State University, Russia; University of Texas at Dallas; and Hebrew University, Jerusalem. His research interests are field oriented, focusing mostly on both modern and ancient fluvial systems and physical stratigraphy. Current interests include controls on permeability trends and connectivity of flow paths in sediments, quantifying fundamental sedimentary processes at small and large scales, preservation of modern processes in the stratigraphic record, and tectonic and climatic impact on rivers. He applies his research widely across petroleum, geothermal, and environmental issues, and is well published, well cited (<5000), and active professionally in each of these fields. He has thus far graduated 39 M.S. and four Ph.D. thesis students in these fields. He gained his B.S. at the University of Kentucky, his M.S. at the University of New Mexico, and his Ph.D. at Indiana University, all in Geology. He was PI for the NSF Research Coordination Network for research in geothermal energy from sedimentary basins. He has served on several committees at SEPM, GSA, and AAPG. He is a past member of GSA Council, past Chair of the GSA Sedimentary Geology Division, past Chair of the GSA Publications Committee, and is a GSA Fellow. He has served SEPM on SEPM Council and as President of Gulf Coast and Mid-Continent sections, and he teaches short courses and serves/chairs committees for AAPG. He a licensed Professional Geologist and served as Vice Chair of the Board of Geologist Registration in Missouri. He works on numerous funded research projects globally and has sat proposal review panels for PRF, AAPG, NSF, and USGS. He was an AAPG Distinguished Lecturer in 2015/2016, teaches AAPG short courses in fluvial and sequence stratigraphy, and won the Madsen Award for Best Oral Presentation at the annual meeting (ACE) in 2019.
Quantifying and qualifying reservoir characteristics and processes for upper-flow-regime-dominated river systems using the Triassic Dockum Group of West Texas
Once considered practically abstractions, fluvial systems dominated by upper-flow-regime structures (UFR systems) are now considered common. Accordingly, they have gained consideration as potential reservoirs. Fundamental data and models for reservoir properties of these systems though are still lacking. Triassic strata of the Tecovas and Trujillo formations in the Palo Duro Canyon of West Texas provide an opportunity to develop models for vertical sequences and reservoir architecture of UFR systems, and lend insights into the processes that form UFR systems. Two channel-fill reservoir elements dominate the Dockum Group, a thin channel fill with low-Froude structures and a thicker channel fill with high-Froude structures. Thicker channel-fills (~2 m, aspect ratio ~24) host upper-plane-bed, symmetrical antidune, breaking-antidune, chute-and-pool, and cyclic-step structures. The thinner channel-fill population (<1 m, aspect ratio ~35) comprises upper-plane-bed and some antidune structures. Both channel-fill elements tend to record single cut-and-fill events. Bars are transverse, but include the first recorded example of a laterally accreting side-attached bar. Lamina follow accretion surfaces as these follow the bed orientation of the time. A generalized vertical sequence for large UFR channel stories has upper-plane-bed structures above the basal scour, transitioning upward into higher flow regime structures (e.g., antidunes, cyclic steps, etc.), then back to a mix of upper-plane-bed and antidunes or lower-flow-regime structures toward the top. The Tecovas Formation and overlying Trujillo Sandstone both preserve cross-cutting multivalleys and are separated by a regional sequence boundary. Calculated paleodischarges are for the flow stage where antidunes form and are ~90 m3/sec (Tecovas) and ~76 m3/sec (Trujillo). Slopes for the rivers were on the order of 10-4 – 10-5, consistent with typical continental-interior rivers. The channel fills thus record supercritical flow conditions from flashy discharge instead of excessive slopes. The abundant UFR channels in the Dockum Group provide insights into reservoir trends not previously definable from existing more isolated examples. The study provides vertical profiles and aspect ratios needed for recognition and modeling of UFR river systems from subsurface data sets. The Dockum rivers developed in a tropical to subtropical megamonsoonal environment, prone to meter-scale channel-fill events. This and related catastrophic inundations of floodplains and lakes in single floods has also made the Dockum Group a prolific preserver of large Triassic vertebrates.
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