Seismic‐guided waves for reservoir continuity at the Gypsy test site, Oklahoma

Abstract

The gas and oil industry is continuing to emphasize research and development efforts on advanced technology to improve reservoir description through the producing life and development history of heterogeneous hydrocarbon reservoirs. Existing methods for reducing uncertainty in heterogeneous reservoir compartments, such as VSP and multiple offsets crosswell techniques may enhance resolution, but these methods are not economically justifiable in oil and gas fields. Continuity logging using guided waves is an alternative approach to analyzing interwell seismic data to confirm the continuity of heterogeneous hydrocarbon reservoir compartments; in particular, the continuity of sand and shale stratigraphy in reservoirs. The present work includes a study of rock physical properties and seismic data for hydrocarbon reservoir continuity using interwell logging techniques. Processing methods are used to delineate the reservoir structure and to relate seismic wave dispersion with rock physical parameters. The principal application of this study is to identify and analyze the propagation characteristics of guided waves in the Gypsy-fluvial sandstone formation at the Gypsy test site in Oklahoma. The integration of well logs and interwell seismic data using guided waves indicated the presence of two low-velocity clean sands to be continuous in the Gypsy sandstone interval. In addition, the results of this work confirmed the presence of a continuous shale above the sandstone. The correlation of sand and shale stratigraphy with well logs and leaky modes is consistent with crosswell and pulse test data acquired by BP Exploration. These pulse tests indicated that the sands are in pressure communication between the wells as well as the existence of an impermeable barrier between the top and the bottom of the sand units in the Gypsy sandstone reservoir.