关键词: 火山岩气藏储层, 渗透率, 有效应力, 应力敏感, 孔隙结构

Abstract: Stress-dependent permeability of volcanic gas reservoir rock has been studied using the larger size rock samples because the volcanic gas reservoir has some special features including complex pore structure, mineral composition and different diagenetic mechanism compared with the conventional sandstone reservoir. The experimental results indicate that the low permeability volcanic rock has strong permeability stress-dependent. The permeability of rock decreases with the increase of effective stress but most of the permeability reduction happens when the effective stress is less than 20 MPa. The rock permeability continuously decreases when the effective stress is larger than 30 MPa. It has been also found that difference in rock pore structure is the main factor affecting the feature of stress-dependent permeability. Rock samples containing fractures demonstrate the strongest stress-dependent permeability. Repeated loading and unloading experiments suggest that stress release caused by drilling is the key factor leading the hysteresis phenomenon. The rock samples occurs mainly elastic deformation when loading and unloading in the second cycle. Rock permeability under high effective stress is only fifty percent of that under low effectiveness.

Key words: volcanic gas reservoir, permeability, effective stress, stress sensitivity, pore structure