4D Seismic Monitoring Technique during Modern Coal Mining

To study the impact of modern coal mining on the overlying formation, a full life-cycle 4D seismic monitoring study has been carried out. Four seismic data campaigns have been performed using flexi-bin geometry with square bins, with total duration of 170 days. Our 4D seismic monitoring of modern coal mining shows that mined and unmined areas have significant zoning characteristics; coal mining has direct impact on the overlying formation. The mining leads to obvious event subsidence, which reflects that overlying formations undergo subsidence during the mining process. The overlying formation appears as two zones, called caving zone and fractured zone. We see that during the coal mining process, over time, the overlying formation has a self-recovery capability which gradually strengthens from the roof of the mine up to the unconsolidated formation near the surface. The stability of a 20m barrier pillar between working faces displays a strengthening trend and remains safe during the mining process due to both coal seam supporting and formation compaction effects.