Peter P. Flaig is a Research Associate Professor at the Bureau of Economic Geology, UT-Austin. His Master’s and Postdoctoral work took him to the Central Transantarctic Mountains of Antarctica where he examined sedimentation across the Permian-Triassic boundary. Peter collaborated with paleontologists during his PhD research on the North Slope of Alaska identifying ancient depositional systems and ecosystems of the dinosaur-bearing Prince Creek Formation. He joined the Bureau of Economic Geology in 2009 for a postdoctoral fellowship, and then spent 7 years as lead scientist on fluvial, deltaic, and shallow marine research at the Quantitative Clastics Laboratory Industrial Associates Consortium. Peter now works for the State of Texas Advanced Resource Recovery program, specifically on the Strawn, Wilcox, and Woodbine.

Peter’s research focuses on deposits of clastic and mixed carbonate clastic systems,  typically integrating sedimentology, ichnology, paleopedology, high-resolution image capture and analysis, reservoir characterization, and petroleum geology. He has worked extensively on deposits of the Cretaceous Western Interior Seaway from Texas through the southwestern US (UT, CO, and WY including the Book Cliffs), Canada, and Alaska. Peter has continuing investigations on strata deposited across the Paleocene-Eocene Thermal Maximum Texas, Colorado, and Wyoming, reservoirs on the Eastern Shelf of the Permian Basin, and the Brookian Megasequence on the North Slope of Alaska.

A Survey of Current and Recent Strawn Group Projects by the State of Texas Advanced Resource Recovery (STARR) Group at the BEG, UT-Austin

Peter P. Flaig

With contributions from Kelly Hattori, William Ambrose, Andrew Roberts, Jerry Jensen, Stephen T. Hasiotis, David Carr, Eric Radjef, Chris Ogiesoba, Lucy Ko, Qilong Fu, and Lorena Moscardelli

This talk is a survey of recent and current research that the State of Texas Advanced Resource Recovery (STARR) group at Bureau of Economic Geology is pursuing on the Strawn Group in the Fort Worth Basin and Eastern Shelf of the Permian Basin. Our main goals are to: 1) integrate core-based sedimentologic and ichnologic observations with wireline log data to refine depositional system interpretations for siliciclastic, carbonate, and mixed systems of the Strawn; 2) identify allogenic (external) versus autogenic (internal) controls on facies-stacking variability; and 3) provide semi-regional correlations to improve predictive models for the characteristics, stratal geometries, regional distribution, and spatial-temporal evolution of Strawn deposystems.

Recent work on the Lower Strawn Group in the subsurface in Jack and Wise counties, Fort Worth Basin identified laterally and vertically heterogeneous deltaic deposits and discontinuous carbonates reflecting cyclothems deposited during icehouse conditions. We develop a stratigraphic and depositional framework, identify individual sequences, provide net sand maps, and propose depositional controls for reservoir predictability in the region.

Outcrops of the Lower Strawn from a quarry in San Saba County expose similar fluvial-deltaic deposits as those interpreted from core in Jack County. Channel systems that transition to sandy mouth bar deposits with mud-draped sedimentary structures suggest tidally-modified delta deposits.  These delta deposits also contain a marine trace fossil assemblage. Well-preserved paleobotany is consistent with a Pennsylvanian, coastal setting.

Core and wireline logs from the Upper Strawn Group in Stonewall and King Counties reveal both extensive siliciclastic and carbonate intervals. Correlation of surfaces across siliciclastic and carbonate systems is challenging. Quartz-rich sandbodies are trough to current-ripple cross-stratified with intervals of well-developed herringbone cross-stratification mud rip-up clasts, mud balls, and mud-drapes. Sandbodies are moderately to heavily bioturbated with a diverse and abundant marine trace-fossil assemblage. Interbedded intervals of carbonate-clast rich sandstone with fragments of crinoids, bivalves, and ooids are typically trough-to-ripple cross-stratified with mud drapes, mud clasts, mud balls, and some dipping beds. Bioturbated wavy-to lenticular bedded siltstones and flaser-bedded sandstones are interbedded with the quartz-rich and carbonate-clast rich sandstone. Carbonates are internally highly complex and suggest significant variations is water depth and sea level. The interfingering nature of the siliciclastics and carbonates suggest that these are deposits of prograding and retrograding, highly complex, tidally modified deltaic deposystems that interfinger with carbonate factories along a shallow-dipping tidal shelf-ramp. Recent probe permeameter measurements on a wide variety of facies, ongoing seismic facies identification, and diagenesis analysis are also briefly discussed.