A Joint Study Combining Seismology And Reservoir Geomechanics On Microseismic Data

In the past few years, multi-stage hydraulic fracturing technique has been widely used in tight oil/gas production. Microseismic events, which are induced by hydraulic fracturing can help increase the permeability at the hydraulic region. Therefore, this technique can help enhance the production performance. Microseismic monitoring has been used in field operation due to its ability in providing valuable information about the fracture zone. Currently, microseismic monitoring is mainly focusing on two clusters of issues. One of them is location uncertainty, whereas the other is source focal mechanism inversion. In this study, we apply the methodology of seismology to microseismic data. Furthermore, we introduce geomechanics to analyze the inverted focal mechanisms.1. We discuss the location uncertainties Firstly, we discuss the two kinds of classic locating methods, i.e., traveltime locating method based on arrival picking and migration locating method based on amplitude stacking. We compare the two methods and analyze their uncertainties. Then we discuss the possibility to locate microseismic events using only S-wave data. Moreover, we conduct some preliminary experiments for inverting location and velocity simultaneously.2. We discuss source focal mechanism inversion We develop an inversion method for microseismic data based on two monitoring arrays. After validating the capability of this method through synthetic data, we invert 123 focal mechanisms using real data. In the last Chapter, we discuss the search engine method for inverting source parameters of nature earthquakes.3. Using geomechanics to analyze inverted focal mechanisms We introduce the methodology of geomechanics to conduct further analysis on inverted focal mechanisms. The results that we derive from focal mechanisms include stress pattern, actual fault plane, fracture network, and pore pressure distribution. From the results we can conclude that, the pore pressure decreases with the increasing distances between events and injection wells.