Abstract

The ability to high-grade oil and gas shales is essential to optimizing completions and maximizing stimulating rock volume (SRV) in the capital-intensive development of the Permian Basin resource plays. To assist in optimizing stimulation efforts, seismic data are used to estimate and map four parameters that influence hydraulic fracture effectiveness: rock properties, in-situ stress, natural fractures, and reservoir geometry.

Predicting rock properties is performed through isotropic pre-stack inversion to estimate and map “brittleness” of oil and gas shale zones. The combination of isotropic pre-stack inversion with an analysis of amplitude variations with azimuth (AVAZ) is used to estimate in-situ stress in the context of fault stress equilibrium for completion design and understanding fracture propagation. Furthermore, the potential presence of (HTI) anisotropy and natural fractures that enhance in-situ permeability is also estimated through azimuthal variations in amplitude. Wide-azimuth broadband reflection seismic data, in conjunction with rock property estimates, are used to estimate reservoir geometry and map potential hydraulic fracture barriers. Through estimation of these four quantities, this presentation describes the fit-for-purpose seismic data acquisition, subsurface imaging, and reservoir characterization methods that can be applied to map “sweet spots”.

Beyond what might now be considered a standard industry approach to predict “frackability”, results of the unconventional reservoir characterization can be confirmed and calibrated by a joint analysis of microseismic data with the use of permanent seismic monitoring for SRV mapping. The combination of these independent measurements enables for an improved SRV estimate validated by stage-specific well completion pressure and production measurements.