Abstract

Devonian chert reservoirs in West Texas have produced over 750 million barrels of oil equivalent, and still have considerable potential for exploitation. Heterogeneity of the chert reservoirs results in low recovery ratios and is a function of depositional facies and fractures. The abundance of well logs, cores and 3-D seismic data makes the reservoir an excellent candidate for detailed study of the relation of fractures and rock properties to seismic attributes. Fractures in the rock influence the rock properties of chert as a media of P-wave propagation, and sonic logs can be used to tie velocity anomalies to fractured intervals identified in cores. Fluid saturations in the pores/fractures can be modeled with Gassmann’s Equation. We are integrating log, core, and production data from Devonian chert reservoirs in Crane County to provide ground truth calibrations for new 3-D seismic attribute algorithms being developed at the University of Houston, and to provide input for small-scale, two phase reservoir simulation studies. The current preliminary research indicates good relationships between P-wave velocity and porosity measured from cores, and between published production volumes and seismic lineaments. We present our results in terms of a detailed 3-D geologic model suitable for input into a reservoir simulator.