Using microseismic frequency-magnitude distributions from hydraulic fracturing as an incremental tool for fracture completion diagnostics

摘要

Microseismic measurements are becoming increasingly routine with many large, pad scale hydraulic fracturing programs particularly in the prolific unconventional shale basins of North America. Spatial and temporal frequency-magnitude distributions or 'b-value' measurements can provide useful information, which can help with hydraulic fracturing diagnostics as well as design. In this study, we discuss the significant differences in the seismicity distributions in the upper and middle Wolfcamp formations at the Hydraulic Fracturing Test Site located in the Midland Basin, a sub-basin of the Permian. We validate observed seismicity behavior in relation to other reservoir properties of interest, including 3D seismic derived attributes and petrophysical data. The in-situ stress state has a significant bearing on b-value and we validate this using various observations. Specifically, we observe an inverse correlation between b-value distribution and in-situ differential stress. We correlate observed microseismicity with available 3D seismic data. We see significant impact of in-situ discontinuities and rock brittleness on the microseismicity distributions. In particular, in areas with large identifiable discontinuities, which are ideally aligned for shear failure, we see lower b-value slopes when compared with areas, which lack significant discontinuities or where they are not ideally aligned. We also look at hydraulic fracturing treatment data, specifically, injection pressure, and tie it with variations in microseismicity during pumping. The analysis of microseismic b-value as shown in this study provides a template for future applications where microseismic surveys are available.