Numerical simulation of gas production potential from permafrost hydrate deposits by huff and puff method in a single horizontal well in Qilian Mountain, Qinghai province

Abstract

Based on the geological data of the Qinghai-Tibet plateau permafrost, such as the permafrost ground temperature, the thermal gradient within and below the frozen layer, we numerically investigate the gas production potential from hydrates at the DK-3 drilling site of the Qilian Mountain permafrost, which is located in the north of the Qinghai-Tibet plateau. We employ the huff and puff method using a single horizontal well in the middle of the Hydrate-Bearing Layer (HBL). The simulation results indicate that desirable gas-to-water ratio and energy efficiency can be obtained under suitable injection and production conditions in the huff and puff process. However, the absolute gas production rate remains low during the whole production process. The sensitivity analysis indicates that the gas production performance is strongly dependent on the intrinsic permeability of the hydrate deposits, the sediment porosity, the injection and production rates, the temperature of the injected water, the irreducible water saturation and P01. The relative permeability exponents appear to have limited effect on the gas production behavior using the huff and puff method. The sensitivity analysis also indicates that the production potential of the natural gas hydrate deposit will be better than that of pure methane hydrate in this simulation.