Microseismic Monitoring and Hypocenter Location

Lejia (Lilly) Han

Well fracturing or CO₂ sequestration produces microseismic events that indicate the location of the injected fluids, providing feedback on the stimulation objectives. This thesis provides improvement to standard procedures to locate the microseismic events more accurately.

Three methods, for arrival time-picking, propagation polarization approximation, and hypocenter localization of microseismic events, are proposed in this thesis along with a particular noise attenuation approach to pre-process raw microseismograms. The three proposed methods are named as modified energy ratio analysis, hodogram analysis, and back-propagation analysis. They are stable and robust for microseismic monitoring.

Effective noise attenuation, event-detection trigger, propagation polarization by weighted least-squares regression on hodograms, and hypocenter estimation are also included. A novel approach for finding the nearest point to two spatial lines is included to estimate a source location.

The joint procedure integrating all proposed methods was implemented in MATLAB software and can consistently produce hypocenter locations at a signal to noise ratio of 3.