Monitoring of coal-mine goaf based on 4D seismic technology

The range of coal-mine underground goaf has continuously expanded over time. Caving, fracture, and deformation zones have also changed, thereby inducing coal-mine water inrush and other environmental disasters. In this study, 4D seismic monitoring technology that is effective in reservoir development was used to monitor abnormal changes in coal-mine underground goaf to explore the feasibility of the method. Taking a coal mine in Hancheng, Shaanxi as an example, we used the aforementioned technology to dynamically monitor the abnormal changes in the goaf. Based on the 4D seismic data obtained in the experiment and the abnormal change characteristics of the coal-mine goaf, the method of 4D seismic data processing in reservoir was improved. A set of 4D data processing flow for the goaf was established, and the anomalies in the surface elevation and overlying strata velocity caused by collapse were corrected. We have made the following improvements to the method of 4D seismic data processing in the reservoir: (1) the static correction problem caused by the changes of surface elevation and destruction of the low-velocity layer has been solved through fusion static correction to comb the low-frequency components of elevation statics with the high-frequency components of refraction statics; (2) the problem of overlying strata velocity changes in the goaf caused by collapse has been solved through the velocity consistency method; (3) the problem of reflection event pull-down in the disturbance area has been solved through space-varying moveout correction based on cross-correlation; and (4) amplitude anomalies in the coal seam caused by the goaf have been addressed using the correction method of space-varying amplitude. Results show that the 4D seismic data processing and interpretation method established in this study is reasonable and effective.