Reservoir stress from microseismic source mechanisms

Abstract

Microseismic monitoring allows an inversion of advanced parameters that characterize a reservoir such as a stress-field orientation in addition to usual locations and source mechanisms. By inverting source mechanisms of microseismic events induced by hydraulic fracturing in a shale reservoir and using those mechanisms, one can obtain the stress field. Stress-field inversions using source mechanisms inverted from manually and automatically picked P-wave arrival amplitudes were compared. Stress fields determined from manual and automated P-wave arrival amplitudes are consistent. This implies that one can use the automated inversion of source mechanisms to reliably determine the stress field. The resulting stress fields are stable and consistent with the regional stress field measured in the region on the World Stress Map. Obtained maximum regional stress in the vertical direction, which is typical for most sedimentary basins, and a maximum horizontal stress oriented approximately 75° from the direction of the drilled lateral sections of wells. Finally, an inverted-shape ratio is used to plot Mohr diagrams that illustrate the most likely fault planes activated through hydraulic fracturing.