Microseismic source location imaging using in-well distributed fiber-optic monitoring data during horizontal well fracturing in shale gas reservoir

Hydraulic fracturing is an indispensable technology for the development of unconventional oil and gas resource reservoirs. To improve the efficiency of fracturing, microseismic monitoring is widely used to monitor and evaluate the reservoir stimulation. Recently, fiber-optic distributed acoustic sensing (DAS) technology has been applied to microseismic monitoring in hydraulic fracturing and shown great potential. By installing the fiber permanently outside the casing of the horizontal well and playing fracturing in the monitoring well, we perform a real-time DAS monitoring of in-well hydraulic fracturing of horizontal well. In the in-well monitoring, the monitoring well is close to the fracturing zone, and its acquisition azimuth perpendicular to the monitoring well is relatively narrow, resulting in poor resolution of the conventional source location stacking algorithm; furthermore, the strong polarity reversal of the waveforms, which will affect the accuracy of stacking image. In this study, we propose a hybrid imaging condition based stacking algorithm using waveform envelopes. The synthetic examples show that the proposed method has the following two advantages : (1) using the waveform envelope can reduce the polarity reversal and improve the accuracy of stacking image; (2) using hybrid imaging condition can suppress stacking artifact and improve the resolution of the source location image. We further analyze real data from Zhaotong shale gas project, and the results show that the proposed method can improve the spatial resolution and accuracy of the source location image.