Upper Cretaceous Formation Lithostratigraphic Correlation Study for Madison and Leon Counties, East Texas Basin
The East Texas Basin contains several important reservoir formations. Our work includes the Upper Cretaceous formations from Del Rio at the bottom, up to the Austin Chalk at the top. A dataset of wireline logs from 130 wells distributed throughout Madison and Leon counties were collected and analyzed. A base map with the location of wells was constructed. Structure contour maps were generated for the top and base of the Austin Chalk. In addition, isopach maps were produced for the Del Rio, Buda Limestone, Woodbine, Eagle Ford, and Austin Chalk. Moreover, several cross sections were generated to understand the changes on the different formations across the two counties. Also, it was noticed that the top of Woodbine Group (i.e., base of Eagle Ford) identification is still questionable. This work will investigate this debate.
Results obtained using well logs, cross sections, and contour and isopach maps were studied and analyzed. The depth of the base of Austin Chalk range from 4500 to 9400 ft. In the southeast side, the depth becomes deeper. Austin Chalk appears to have better thickness homogeneity. The overall thickness between 250 and 350 ft. The Eagle Ford Shale overlays the Woodbine Group. The average thickness is 400 ft. The Woodbine formation contains both sandy and shaly intervals. An abrupt change in thickness between the sandy and shaly section was observed. We believe the sandy woodbine to be a channel, based on the lithostratigraphic correlations. The thickness is 200 ft at the northwest side. Moving to the northeast side, the Woodbine thickens to approximately 900 ft. The Buda Limestone has a thickness of 45 to 100 ft. The Buda Limestone gradually thins from the north to the south. For the Del Rio Formation, has an average thickness of 25 ft, and no significant change in the thickness was noticed.
AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015