Hydrocarbon reservoir studies, San Andres/Grayburg formations, Permian Basin : proceedings, research conference, October 7-9, 1986, Midland, Texas / sponsored by the Bureau of Economic Geology, the University of Texas at Austin, and the Permian Basin Section/Society of Economic Paleontologists and Mineralogists ; co-chairmen and editors, D.G. Bebout and P.M. Harris