Effect of thermal stimulation on gas production from hydrate deposits in Shenhu area of the South China Sea

The Shenhu area on the northern continental slope of the South China Sea (SCS) is one of the promising fields for gas hydrate exploitation. The hydrate-bearing layer at drilling site SH2 is overlain and underlain by permeable zones of mobile water. In this study a vertical well was configured with a perforated Interval I for producing gas and a coiled Interval II for heating sediment. The hydrate is dissociated by a small depressurization at Interval I and a thermal stimulation at Interval II. The numerical simulations indicate that the thermal stimulation has a significant effect on gas release from the hydrates in the production duration and improves the gas production in the late period. The gas released by thermal stimulation cannot be produced as quickly as the production gets operated because of the hard pathway for fluids to flow in the sediments. The gas production is enhanced due to the heating for 7242 m3 in the whole production. Increasing heating temperature at Interval II can improve gas production and restrain water output, and advance the arrival time of the gas flow from the zone at Interval II. The absolute criterion and relative criterion suggest that the thermal stimulation in the production schemes is pronounced for releasing gas from the hydrate deposit, but the production efficiency of gas is limited by the sediment of low permeability. The study provides an insight into the production potential of the hydrate accumulations by thermal stimulation with depressurization in two wells, and a basis for analyzing economic feasibility of gas production from the area.