Abstract: Diagenesis, Morphology and Reservoir Effects of Authigenic Illite and Chlorite in the Cherry Canyon Formation, Delaware Mountain Group, Screwbean Field, Reeves County, Texas

M. D. Thomerson, S. K. Henderson

Oil and gas production in the Screwbean Field of Reeves County, Texas, is predominately from the subarkosic Bell Canyon (Ramsey Sand member) and upper Cherry Canyon sandstones of the Permian Delaware Mountain Group. Authigenic clays constitute up to 10 percent of the bulk rock and can seriously degrade production potential and performance of reservoir rock. Illite and chlorite clays may 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.

Ten powered samples from whole core were taken from the Cherry Canyon Formation in Reeves County. X-ray diffraction analysis of oriented slides of these samples permits the identification of the different clay minerals present in the reservoir. Because morphologies of authigenic clays are also important to reservoir performance, scanning electron microscopy is used to delineate the clay morphologies and to illustrate the intergranular habits of the clay minerals.

Failure to recognize the aforementioned problems can lead to bypassing and premature abandonment of possible productive zones within the Cherry Canyon Formation. The data generated by this study can be employed to better understand these reservoirs as well as more effectively explore future ones.

AAPG Search and Discovery Article #90960©1995 AAPG Southwest Section Meeting, Dallas, Texas