Seismic Inversion for Engineering Applications in Unconventional Reservoirs

Abstract

Summary Economic production from unconventional reservoirs requires increasing the surface area in contact with the reservoir via hydraulic fracturing. Important to the design of efficient hydraulic fractures is knowledge of the orientation and magnitude of principal stresses, geomechanical rock properties, and the density and orientation of any natural fractures. The use of seismic AVOAz (Amplitude Variation with Offset and Azimuth) inversion to determine fracture density and orientation as well as horizontal stress anisotropy and the orientation of the principal stresses is illustrated using examples from the Middle East and North America. An example is shown of using the results of seismic AVOAz inversion calibrated to geomechanical measurements on cores, to build a 3D MEM (Mechanical Earth Model) for an area in North America. The variation in principal stresses over the area is evaluated using the Finite Element Method. Computed stresses are found to be consistent with variability in production over the area and show stress rotations near faults in agreement with microseismic data.