Source Parameters of Hydraulic Fracture Induced Microseismicity

摘要

Microseismic results are presented for hydraulic fracturestimulations monitored in the Cotton Valley, East Texas. Inparticular, we examine whether additional information on themicroseismic source such as the apparent stress release valuescan be used to effectively identify differences in thegeneration process of individual or clusters of microseismicevents and the development of the overall hydraulic fracture inboth space and time. Trends in apparent stress have been usedto establish different modes of failure, with increased apparentstress values at the leading edge of the hydraulic fracture andlower apparent stress values behind the leading edge. Wesuggest that the failures are along a pre-existing network offractures and include significant non-shear components offailure for events occurring behind the hydraulic fracture front.At the extremities of the hydraulic fracture as the stimulationproceeds we suggest that the redistribution of stresses as aresult of the injection increase the average shear driving stressresulting in shear dominated failures. Overall, the hydraulicfracture can be characterized by regions of shear and nonsheartype failures, further suggesting that the relativepermeability of the fracture network can possiblybe identified.