September Luncheon

Please RSVP by 3:00pm on Friday, September 25, 2026.

Reservations made after the deadline will incur an additional fee of $10.

LOCATION: In-Person luncheon meeting will be held at the Bush Convention Center. Virtual meeting on Zoom. 

TOPIC: Integrated Tectonics, Geological, and Geochemical Insights into Oil Sources, Maturity, and Migration Pathways of the Pennsylvanian (Desmoinesian) Strawn Group, North-Central Texas SPEAKER: Lucy Tingwei Ko

AUTHORS: Lucy Tingwei Ko, Xun Sun, Eric Radjef, Kelly Hattori, Peter Flaig

AFFILIATION: Bureau of Economic Geology, Jackson School of Geosciences, the University of Texas at Austin

ABSTRACT: The Strawn Group, deposited during the Pennsylvanian icehouse period, represents significant sandstone, carbonate, and mixed carbonate-sand reservoirs on the Eastern Shelf of the Permian Basin in Texas. These reservoirs have long been of interest due to their complex depositional histories, heterogeneous reservoir properties, and substantial hydrocarbon production potential. 

This ongoing study integrates regional tectonic and burial history with depositional framework and geochemical analyses, including bulk oil compositions, biomarkers, and diamondoids of produced oils, together with bulk geochemical analyses on source rock cores and cuttings, to investigate the petroleum system of the sandstone and carbonate reservoirs of the Strawn Group. Core and cuttings XRF data from source rock candidates in both the Fort Worth and Midland Basins, as well as shelf-to-basin core, were incorporated. The objectives are to better constrain oil sources, maturity, and the timing of hydrocarbon generation, migration, and entrapment. We also assess source rock distribution, richness, quality, and thermal maturity, linking these parameters to oil fingerprinting and typing.

Geochemical results show that oils from carbonate reservoirs in southeastern Scurry County, sandstone reservoirs in western Fisher County, and sandstone reservoirs (Flat Top JC) in Haskell County could be primarily sourced from a late oil window origin, with additional evidence of minor mixing with a secondary, higher-maturity source like a gas condensate or wet gas. In contrast, oils from the Goen Limestone reservoirs (Runnels Co.), Gray Sand reservoirs (Coleman and Taylor Counties), Katz Field (Stonewall Co.), and Cisco Group Tannehill sand share biomarker affinities with the Barnett Shale of the Fort Worth Basin, yet diamondoid signatures indicate mixing with a different secondary, more mature source. Similarly, mixed sourcing is evident in oils from the Truby Sand Field (Jones Co.) with dominated sources from Wolfcamp D/Cline Shale with a secondary, more mature source. 

Biomarker and diamondoid data, combined with regional thermal maturity assessments of the Barnett Shale in the Fort Worth Basin (FWB) and the Wolfcamp D/Cline Shale in the Midland Basin, indicate contrasting migration histories. Oils from the Barnett Shale, which contain thick, laterally extensive source rock intervals, migrated continuously beginning in the middle of the oil window — a scenario that aligns with current geochemical data. In contrast, oils from the Wolfcamp D appear to have charged the Eastern Shelf much later, near the end of the oil window, in a one-time or instantaneous event rather than as a continuous process. This interpretation is further complicated by the Wolfcamp D depositional cycles, where the most effective source rock intervals are relatively thin and encased by thick clay-rich units, making the timing and efficiency of migration and expulsion more uncertain.

Petroleum system modeling, incorporating burial history, generation kinetics, and tectonic evolution, indicates that the peak hydrocarbon generation from the Barnett and Woodford Shales occurred during the Permian to Triassic, whereas the Wolfcamp D/Cline Shale reached maximum generation later, from Jurassic to Cretaceous. If the Strawn reservoir is effectively sealed and enclosed by surrounding shales, reservoirs in the Eastern Shelf area would most likely receive oil charges from the Barnett and Woodford generation first. Migration distance is affected by oil column height, faulting, and stratigraphic complexity, particularly carrier bed heterogeneity. Ongoing oil sampling, reservoir characterization, and data acquisition in the Strawn Group will continue to refine our understanding of petroleum system elements, including carrier beds, sealing and migration roles of faults, and trap efficiency. Migration losses via carrier beds and leakage along faults remain important factors to assess.

BIO: Dr. Lucy Ko is a Research Assistant Professor at the Bureau of Economic Geology (BEG), Jackson School of Geosciences, The University of Texas at Austin. Her research focuses on mudrock sedimentology, stratigraphy, geochemistry, organic matter characterization, and diagenesis in unconventional and conventional systems. Much of her work examines the geologic controls on reservoir quality and fluid deliverability in unconventional plays, as well as the petroleum systems of conventional reservoirs in Texas.

Lucy integrates core-based sedimentology, elemental and organic geochemistry, petrography, and scanning electron microscopy to investigate depositional systems, organic and inorganic components, reservoir quality, fluid–rock interactions, and subsurface heterogeneity. Her research has encompassed the Eagle Ford, Pearsall, Haynesville–Bossier, Barnett, Woodford, Marcellus, Wolfcamp, and Bone Spring, along with other Paleozoic and Mesozoic petroleum systems.

More recently, Lucy has expanded her research into emerging energy resources in Texas and brackish aquifer hydrogeochemistry. Her work characterizes groundwater composition and spatial variability to better understand water-treatment and desalination requirements. She also works closely with graduate students on Texas subsurface projects, including studies of the Woodbine and Buda intervals in the East Texas Basin and the Boonsville Conglomerate in the Fort Worth Basin.

Her industry experience includes working as a geologist with Platte River Associates and completing geoscience internships with ConocoPhillips, where she contributed to Eagle Ford and Gulf of Mexico projects. At ConocoPhillips, she integrated PVT and fluid-property data with petroleum geochemistry and stratigraphic frameworks to better understand the processes that influence petroleum systems and fluid properties. These experiences continue to inform her applied, multidisciplinary approach to subsurface geoscience and her collaborations with the energy industry.

At BEG, Lucy leads the e-MAGE and HAWK Laboratory and collaborates closely with students, academic researchers, and industry partners on applied subsurface research. She earned her Ph.D. in Geological Sciences from The University of Texas at Austin and her M.S. in Geology from the Colorado School of Mines.