Microseismic Monitoring of Hydraulic Fracture Propagation and Seismic Risks in Shale Reservoir with a Steep Dip Angle

Hydraulic fracturing is an essential technique to increase reservoir permeability and enhance the production of shale gas. When the dip angle is steep and geological condition is complex, hydraulic fractures may behave complexly, and research on this topic is critical for the shale gas industry. This paper reports a case study of hydraulic fracturing in a shale reservoir with a steep dip angle. We monitored pump data, including the injection rate and fluid pressure. Microseismic monitoring was also used to record the seismic events and monitor the hydraulic fracture propagation. Our results validated that microseismic monitoring is a feasible technique to monitor the hydraulic fracture propagation in shale reservoirs with steep dip angles. Moreover, the variation in depth of shale reservoir induces significant alternation of local in situ stress states, in which cases the fracture propagation pathway is more complex, and where microseismic monitoring is necessary to acquire the hydraulic fracture distribution. Besides, all sound sources, including quarries and rivers, should be eliminated during microseismic station arrangement to improve accuracy of microseismic signals. Moreover, the relationship between the maximum magnitude of seismic event and fluid injection volume was validated further in this study. Finally, unexpected faults and aquifers may affect hydraulic fracture propagation due to the steep dip angle of the target shale reservoir. Thus, a comprehensive geological survey is essential for better hydraulic fracturing design. Our results provide first-hand in situ hydraulic fracturing data and provide important implications for shale gas development, especially for those shale reservoirs with steep dip angles.