Improving gas production of hydrate deposits by increasing reservoir permeability nearby production well in the South China Sea

Abstract

The hydrate deposits in offshore were mainly hosted in the clayey silt sediments, which had the characteristics of looseness and low permeability. Improving the permeability of hydrate reservoirs is the key to promote gas production efficiency. In this work, the enlarged permeable well wall method based on the local reconstruction around the production well was employed for the gas production. The enlarged permeable well wall was created by filling the hydrophobic porous materials to form a cylindrical high permeability area around production well. The gas production of hydrate deposits at the site W-17 in Shenhu area of the South China Sea was simulated by depressurization method. The simulation results showed that the enlarged permeable well wall method could promote the propagation of pressure drop and ensure the continuity of the high-permeability channel around the well. When the radius of enlarged permeable well wall were 1, 3 and 5 m, the gas production increased by 1.45, 2.08 and 2.66 times than that without the enlarged permeable well wall method for 10 years, respectively. Compared with the results of the first actual trial production in the South China Sea, the enlarged permeable well wall method has better production promotion effect on hydrate reservoirs. Moreover, the gas production was sensitive to the intrinsic permeability of the sediments, but not to the thermal conductivity.