Implication of Fault Seal Analysis Method to Evaluate the Sealing Conditions of Major Fault Planes at Barapukuria Basin, North-West Bangladesh

Abstract The Barapukuria Coal Mine is Bangladesh's first and only producing coal mine. The basin is characterized by two major faults that encompass the basin's periphery, as well as multiple minor faults and mine-induced reactivation faults. An extensive Upper Dupitila aquifer and Gondwana Upper Sandstone aquifer are the probable sources of inundation. This study focuses on determining the unsealed faults that can create a potential threat of water leakage in the mine area based on the superposition of lithological sequences, aquifer properties, and sealing capacity of the fault plane using the fault seal analysis method. The superposition of lithological sequences proposed that the northern portion of the study area is more vulnerable to underground inundation due to the presence of very thin or no impermeable layers between the upper UDT aquifer and the underlain Gondwana formation. The fault seal analysis, reveals that the SGR values for the largest Eastern Boundary Fault were estimated to be 0.08 and 0.13; 0.05 for the second largest fault FB; 0.35 and 0.53 for the fault FB-1; and 5.65, 1.69, and 1.22 for the three smaller faults, BGP-N-F11, BGP-N-F2, and F-24. According to Yielding et al classifications of fault sealing, these SGR value represents that the largest Eastern Boundary and the FB fault dip to the west and have an angle of dip of 750-800, indicating that they are susceptible to inundation. An incident of underground flooding along the FB fault plane was reported in 1998, which resembled the study's outcomes.