On the accuracy and efficiency of the joint source scanning algorithm for hydraulic fracturing monitoring

We have developed the joint source scanning algorithm (JSSA) to determine the locations and focal mechanisms (FMs) of microseismic events simultaneously. However, the computational expense of using JSSA is too high to meet the requirements of real-time monitoring in industrial production. We have developed several scanning schemas to reduce computation time. A multistage scanning schema can significantly improve efficiency while retaining accuracy. For the optimized joint inversion method, a series of tests has been carried out using actual field data and synthetic data to evaluate the accuracy of the method, as well as its dependence on the noise level, source depths, FMs, and other factors. The surface-based arrays better constrain horizontal location errors (< 20 m) and angular errors of P-axes (within 10 degrees for S/N > 0.5). For sources with varying rakes, dips, strikes, and depths, the errors are mostly controlled by the partition of positive and negative polarities in different quadrants. More evenly partitioned polarities in different quadrants yield better results for locations and FMs. Nevertheless, even when some FMs have bad resolutions, the optimized JSSA method can still significantly improve location accuracies.