2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 4
Presentation Time: 8:45 AM

Integrated Core, Well Log, and Seismic Interpretation of Lower Glen Rose (Albian) Buildups in Maverick Basin, SW Texas

ACONCHA, Enzo, Jackson School of Geosciences, University of Texas at Austin, 2727 W 18th st, Apt. # 443, Houston, TX 77008, KERANS, Charles, The Jackson School of Geosicences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 and ZENG, Hongliu, Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Rd, Bldg130, Austin, TX 78758, ezsener@hotmail.com

Stratigraphic analysis of well logs and seismic stratal-slices indicates that the Lower Glen Rose Formation, Maverick Basin, comprises four units. From bottom to top, the units record the HST of sequence 6 and all of sequence 7. The reef interval comprises sequence 7 and consists of three reef levels throughout units 2-4. Buildups in unit 2 change from transgressive isolated buildups into a flat biostrome. Unit 3 buildups record a landward shift relative to the biostrome of unit 2, as shown on well logs. Unit 4 buildups record seaward shift of bioherms relative to unit 3.

Development of an individual reef level occurred mostly in decreasing accommodation trends of high-frequency sequences, as described for two cored buildups in unit 4. Shoaling-reefal buildups correlate with a distinctive clean, blocky gamma-ray response and strong negative seismic amplitude anomalies. Off-reef deposits correlate with a higher, variable gamma-ray response and positive seismic amplitudes. The shoaling-reefal facies may be gas reservoirs; gas potential concentrate in units 2 and 4.

Geomorphometric analysis based on seismic stratal slices and > 30 buildups of unit 4 determined that the domal features elongated NNW-SSE, with steeper SW flanks. Asymmetry of the shoaling-reefal buildups may be the result of NW-directed far-field paleo-currents and NNE-directed, wind-driven paleo-waves. Independently of the size scale, the elongation axis of buildups is 1.5-2.5 times larger than its perpendicular direction. Results imply best reservoir facies in the SW side of the Lower Glen Rose patch reefs.