Downhole microseismic monitoring for low signal-to-noise ratio events

作者：Zhou, Hang; Zhang, Wei^*; Zhang, Jie

来源：Journal of Geophysics and Engineering, 2016, 13(5): 805-816.

DOI：10.1088/1742-2132/13/5/805

• microseismic monitoring
• single phase
• grid search
• Monte Carlo

Microseismic monitoring plays an important role in the process of hydraulic fracturing for shale gas/oil production. The accuracy of event location is an essential issue in microseismic monitoring. The data obtained from downhole monitoring system usually show a higher signal-to-noise ratio (SNR) than the recorded data from the surface. For small microseismic events, however, P waves recorded in a downhole array may be very weak, while S waves are generally dominant and strong. Numerical experiments suggest that inverting S-wave arrival times alone is not sufficient to constrain event locations. In this study, we perform extensive location tests with various noise effects using a grid search method that matches the travel time data of the S wave across a recording array. We conclude that fitting S-wave travel time data along with at least one P-wave travel time of the same event can significantly improve location accuracy. In practice, picking S-wave arrival time data and at least one P-wave pick is possible for many small events. We demonstrate that fitting the combination of the travel time data is a robust approach, which can help increase the number of microseismic events to be located accurately during hydraulic fracturing.

• 出版日期2016-10
• 单位中国科学技术大学