An improved method for microseismic source location based on grid search

Microseismic source location is the core problem for microseismic monitoring. As for the downhole monitoring cases, microseismic sources are normally located by minimizing the misfit between the observed and predicted travel times. Conventional method tends to be affected by many factors, such as ambient noises, arrival picking errors and velocity model errors, therefore produces results with larger discrepancies. We propose an improved method for microseismic source location. This method is based on grid search algorithm and some improvements are incorporated to enhance its location accuracy. The improvements include the use of a probability distribution function, which is calculated using the polarization attributes of P-wave, to estimate the source azimuth and the adoption of a new objective function and an improved search algorithm to find the optimal radial distance and depth of the source. The results from testing the proposed method on synthetic and real datasets have shown that this method has a strong noise resistibility and can produce more accurate estimate of the source azimuth. The new objective function shows better convergence than the traditional ones and its location results are less affected by the errors in the arrival times and velocity models. The improved search algorithm can mitigate the impact of erroneous picks on the location results.