A method for locating acoustic emission events using amplitude stacking weighted waveform correlation

Abstract

Acoustic emission monitoring has been the best technique to evaluate hydraulic fracturing which is the most common method used to induce fractures for stimulating hydrocarbon reservoirs. Correlation-based and amplitude-stacking-based methods, both are based on migration and are all suitable for locating acoustic emission events induced by hydraulic fracturing without the need to pick the arrival times of the P- and S-waves. By comparing and analyzing the advantages and disadvantages of the two location methods, we propose a weighted correlation method using both amplitude and waveform correlation. First, we calculate the travel time of acoustic waves from the trial point in the formation to each receiver by the ray-tracing method, and further to determine the time-window positions of the P- and S-waves on all waveforms. Then, we calculate the correlation of the waveforms in the windows and the amplitude stacking of the average energy ratio between the short-time window and the long-time window on the original acoustic waveforms. Finally, we use the correlation weighted by amplitude stacking to image space locations of acoustic emissions. Tests with synthetic data show that the weighted correlation method has stronger stability and lower location uncertainty than the existing migration-based location methods.Acoustic emission monitoring has been the best technique to evaluate hydraulic fracturing which is the most common method used to induce fractures for stimulating hydrocarbon reservoirs. Correlation-based and amplitude-stacking-based methods, both are based on migration and are all suitable for locating acoustic emission events induced by hydraulic fracturing without the need to pick the arrival times of the P- and S-waves. By comparing and analyzing the advantages and disadvantages of the two location methods, we propose a weighted correlation method using both amplitude and waveform correlation. First, we calculate the travel time of acoustic waves from the trial point in the formation to each receiver by the ray-tracing method, and further to determine the time-window positions of the P- and S-waves on all waveforms. Then, we calculate the correlation of the waveforms in the windows and the amplitude stacking of the average energy ratio between the short-time window and the long-time window on the orig...