Interwell seismic logging for formation continuity at the Gypsy test site, Oklahoma

Abstract

The continuity logging (or in-seam) method has been used extensively in the coal industry to determine continuity. Continuity logging is an alternative approach to multiple-offset crosswell seismic measurements using guided waves propagating parallel to the layering; in particular, to determine the continuity of sand and shale stratigraphy in oil and gas fields. The present work is a study of rock physical properties and seismic data for reservoir continuity using interwell logging techniques. Processing methods are used to delineate the reservoir boundaries and to relate seismic waves with rock physical parameters. The specific application has been 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, including trapped seismic events, suggests the presence of a continuous low-velocity clean sand in the Gypsy sandstone interval. The correlation of sand and shale stratigraphy with well logs and guided waves is consistent with available pressure pulse test data, indicating that the sands are in pressure communication between the wells and that an impermeable barrier exists between the top and bottom of the sand units in the Gypsy sandstone reservoir.