Characterization of microseismic data in gas shales using the radius of gyration tensor

Abstract

Gas shales have very low permeability, and hydraulic fracturing of the reservoir is required for economic production. Microseismic monitoring provides data that allows an assessment of the geometry and development of hydraulically‐induced fracture systems. Such data sets have demonstrated that complex fracture networks can form in tight gas shales. Monitoring such networks is key to optimizing production in such reservoirs, since their low permeability requires the creation of an extremely large fracture surface area. One can characterize the geometry of such fracture networks using the radius of gyration tensor. This tensor provides the principal axes of the microseismic cloud, while the principal radii of gyration provide the length, width and height of the fracture treatment. The shape anisotropy can be defined in terms of the ratios of the eigenvalues of the radius of gyration tensor. The shape anisotropy of the hydraulic fracture treatment is sensitive to the anisotropy of the in‐situ stress field and to the orientation of preexisting fractures.