Enhancing the gas production efficiency of depressurization-induced methane hydrate exploitation via fracturing

摘要

Most of the existing field tests of gas recovery from hydrate-bearing sediments suffer from the difficulty in pressure propagation, leading to a low productivity and energy efficiency. Fracturing has shown enormous potential in the shale gas production; thus in this study, we introduced this technique into the laboratory-scale gas hydrate production. The performance of gas production was investigated through numerically analyzing the gas hydrate dissociation behavior under different fracturing patterns. The results indicate that fracturing can significantly facilitate the pressure propagation in the hydrate sediments with a low intrinsic permeability during depressurization, thereby contributing to a better gas production performance. Fracture depth plays a critical role in promoting the gas production efficiency; the maximal enhancement ratio of average production rate by fracturing could attain 13.1%. Moreover, the contribution of reservoir's sensible heat in hydrate dissociation is limited in the core with a low permeability; timely and sufficient heat supply is thus important for the successive gas production. The findings of this study illustrate the effects of fracturing on enhancing the gas production efficiency of depressurization-induced gas hydrate exploitation; this will provide important guidance for its potential application in the field test of marine and permafrost hydrate reservoir where low permeability is commonly encountered and an enhancing technique is much required.