THE NOT SO SIMPLE RELATIONSHIP BETWEEN SEISMICITY AND OIL PRODUCTION IN THE PERMIAN BASIN, WEST TEXAS

We have relocated seismicity occurring in the Permian Basin of west Te xas between 1975 and 1979 using three-dimensional velocity models cons tructed from well log information and compared the locations to detail ed geological and geophysical models of specific oil fields. The seism icity appears to be related to a variety of causes including migration of naturally occurring overpressured fluids, tectonic activity, reser voir production, and enhanced recovery operations. Many earthquakes ma y represent a combination of these effects. Although the Permian Basin is the site of numerous oil and gas fields, only a limited number of fields appears to be associated with seismicity. We find that there ar e similarities in the structural setting in the fields associated with seismicity. Furthermore, fields within the Delaware Basin that are as sociated with seismicity are located in regions of high vertical and l ateral fluid pressure gradients related to an overpressured zone withi n the Delaware Basin.