Study on the microseismic clouds induced by hydraulic fracturing

Microseismicity has become a primary tool for detecting the hydraulic fracturing process. However, whether hydraulic fracture (HF) geometry can be accurately inferred from the microseismic (MS) data is in debate. A dynamic geomechanics code is applied to investigate the correlation between the geometry of the HF and the induced MS clouds. Effects of HF length and cohesion on the correlation are studied. Some examples of the rupture patterns along the NFs are presented. The stability around a dynamically propagating HF is also studied. The inclination of the NFs relative to the maximum horizontal principal direction affects the correlation. When the inclination of the NFs relative to the maximum horizontal principal direction is nearly optimal in geomechanics point of view, the induced MS events spread far away from the HF and are almost symmetric about the HF. The MS cloud has a large discrepancy with the HF in length but small discrepancy in strike. When the inclination of the NFs is either high or low relative to the optimal, the induced MS events could be very close to the HF but quite asymmetric about the HF. The MS cloud has a small discrepancy with the HF in length but large discrepancy in strike.