Back-azimuth Relocation of Monitoring Arrays

Microseismic monitoring of hydraulic fracture treatment is commonly carried out without accurate deviation surveys of monitoring boreholes. This can lead to significant errors in the observed azimuths and other parameters of the mapped fracture system geometry derived from microseismic event locations. We have developed a new technique to find the horizontal position of the monitoring geophones. This technique uses relative back-azimuths of perforations at known locations. It is particularly suitable for vertical monitoring boreholes and horizontally distributed perforations. It can be combined with travel-time measurements to achieve improved accuracy of the monitoring array positions relative to the perforations (i.e., injection points).