Assessment of Fault-seal Integrity for Underground Storage of Natural Gas in Porous Sandstone

Underground gas storage is widely employed for balancing the supply and demand of natural gas, mostly during cold winter periods. We investigate Banzhongbei gas storage (BGS) bounded by B816 and Banqiao fault in Dagang gas storage facilities acting as a swing-supplier to meet peak demand for Beijing, Tianjin and Hebei province. There was wasted natural gas exceeding 7.7×108m³in BGS from 2003 to 2013 that has been one of the most serious problems. There would be big risks on fault-seal integrity. Two aspects included fault membrane seal and fault stability are congsidered in the assessment of fault-seal integrity. We have calibrated the fault membrane seal capacity with the pressure differences across faults from three depressions in Bohai Gulf Basin. Based on that, we conclude that the B816 fault has low lateral capillary sealing capacity resulting in BGS and B814-B to be just one trap bounded by BQ fault. Lateral and vertival membrane seal assessment suggests BQ fault has higher capillary entry pressure (>4.5MPa) than that of stable fault chould sustain (3.0MPa). Hence, according to the stability of BQ fault that the risk of fault seal integrity focus on, modled maximal injection volumn is 13.7×108m3.