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THOMERSON, MARKUS D., and STEVEN K. HENDERSON, Department of Geosciences and the Center for Applied Petrophysical Studies, Texas Tech University, Lubbock, TX

ABSTRACT: Composition, Diagenesis, and Morphology of Chlorite and Illite/Smectite Mixed-Layer Clays in the Cherry Canyon Formation, Delaware Mountain Group, Screwbean Field, Reeves County, Texas

Oil and gas production in the Screwbean field of Reeves County, Texas, is predominantly from the subarkosic Bell Canyon (Ramsey sand member) and upper Cherry Canyon sandstones of the Permian (Guadalupian) Delaware Mountain Group. Authigenic clays compromise up to 10% of the bulk rock and can seriously degrade the production potential and performance of reservoir rock. The chlorite and illite/smectite mixed-layer clays can have several effects on the reservoir: loss of permeability as a result of swelling, formation damage because of acid sensitivity, and high irreducible water saturations (bound water) caused by microporosity.

Twenty-five powdered samples from whole core taken in the Cherry Canyon Formation from a well in Reeves County were analyzed by x-ray diffraction. The actual x-ray diffraction patterns from the powdered samples were compared to simulated x-ray diffraction patterns generated by a microcomputer. Once matched, the computer models give the fractional clay composition of that particular sample.

The prominent morphology of the authigenic clays is also very important. Photomicrographs taken with a scanning electron microscope were employed to delineate the clay morphologies and illustrate the intergranular habits of these clay minerals.

The failure to recognize the aforementioned problems can lead to prematurely abandoning and bypassing possible productive zones. The data generated by this study will allow us to better use these reservoirs and more effectively explore future zones.

AAPG Search and Discovery Article #90991©1993 AAPG Mid-Continent Section Meeting, Amarillo, Texas, October 10-12, 1993.