Characterization of a Fractured Reservoir Using DAS VSP—A Model-Based Reflection Amplitude Study

Abstract

Summary Distributed acoustic sensing (DAS) technology offers the time-lapse capability of monitoring hydraulic fracturing and reservoir depletion processes. This paper uses a model-based study to explore the feasibility of using DAS vertical seismic profiling (VSP) to detect and characterize fracture-induced azimuthal variation in P-wave reflection amplitude. The study particularly focuses on seismic amplitude vs. offset and azimuth (AVOAz) to answer two questions. First, which fracture-induced seismic responses can be detectable by a three-dimensional (3D) DAS VSP survey. Second, how shots can be arranged to detect such seismic responses and image the extent of the fractures. Waveform data were simulated for two types of fractured reservoir models using full-elastic anisotropic algorithms. P-wave reflection amplitude was mapped in incidence angle intervals for the top of each reservoir model. Analyses of the amplitude variation with AVOAz revealed distinctive patterns for the two fracture models. These patterns of amplitude variation can be used to detect fractures, if the fractures have uniform density and similar orientation around the well.