Fracture detection using 3D P‐wave seismic data: An integrated study from Southwest China

Abstract

Summary Here, we present a case study of fracture detection using 3D P-wave seismic data from the Sichuan Basin in Southwest China. A major aspect of this study is the integration of outcrop, core and wireline logs with seismic data for reducing the uncertainties in the seismic results. To guide seismic data analysis, a physical modeling study is also carried out to compare the use of different P-wave seismic attributes and different analysis techniques. The target is a gas reservoir buried at about 1700m depth, and the reservoir rocks are tight sandstones with an average porosity of only about 2%. Fractures are the main fluid pathways. Analysis of core and log data from 21 boreholes reveals that there are two major sets of fractures in the study area striking northeast and northwest, respectively, with an average linear fracture density of about one fracture every two meters. We have processed and analyzed 50km 2 of 3D P-wave seismic data in order to evaluate the fracture characteristics between the boreholes. The seismic data is of average quality. Nevertheless with carefully-calibrated processing, the final fracture orientation and intensity maps estimated from the amplitude attributes compare reasonably well with the regional pattern in the area, and the seismic results at the well locations are consistent with the borehole results. The physical modeling study provides a good benchmark for the selected seismic attributes.