Abstract: Depositional History and Seismic Attributes of Wolfcamp-Leonard Carbonate Buildups, Midland Basin, Upton County, Texas

MERRIAM, CATHERINE O'H., Texas A&M University, Dept. of Geology and Geophysics, College Station, TX

A series of Wolfcamp-Leonard carbonate buildups occur in ft southwestern Midland Basin, Upton County, Texas although the depositional history of these buildups is still controversial. Some workers contend that they are in situ shallow water bioherms that were constructed by algae and tubiphytes, whereas other workers believe that the buildups are allochthonous blocks shed from the Central Basin Platform. The carbonate buildups are located in ft southwestern Midland Basin, just off the eastern edge of the Central Basin Platform. The buildups are generally at depths of 8500-9000 feet and are surrounded by organic-rich shales, which are both source rocks and sealing facies. The buildups attain a maximum thickness of 1100 feet and have very low porosity (mostly fracture porosity) and permeability.

Some of these buildups contain significant petroleum reserves. Because of their economic potential, Chevron USA acquired over 300 mi{2} of overlapping 3D seismic surveys along the mound trend. Chevron has donated these 3-D seismic surveys, along with digital well logs, petrophysical data, and production data, to Texas A&M University. Over 1300 feet of core through several mounds are also available for this study. No detailed integrative study of this impressive data set has been done to understand the seismic attributes of these buildups.

The main objectives of this study are to understand the depositional history of these buildups, to place the buildups within a regional stratigraphic framework, and to understand the seismic attributes of individual buildups. All components of Chevron's impressive data set will be examined for the seismic attribute analysis. This integrated study will provide insights into the sedimentology and stratigraphic framework of other late Paleozoic carbonate buildups, which are common petroleum reservoirs globally. The seismic attribute analysis may also provide techniques for improved recognition of subsurface petroleum accumulations in other fractured carbonate buildups.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid