School of Energy Resources, China University of Geosciences (Beiing)

针对地应力对煤储层初始渗透性及水力压裂裂缝扩展研究,从煤储层地应力状态影响因素、地应力对渗透率的影响规律及控制机理方面进行分析,总结了国内外地应力对煤储层渗透性影响规律及机制研究的最新进展。研究结果表明:煤储层地应力状态影响因素包括构造作用、埋藏深度和煤岩类型3个方面,其中构造作用和埋藏深度占据主导地位。目前捕获地应力大小多利用水压致裂法和物理试验测试,当前主要研究了现代地应力场特征、实验室模拟、数值模拟不同地应力对煤储层渗透率影响,其实质是对煤储层孔隙-裂隙结构产生变形。区域应力场产生区域性的裂隙系统,控制着煤储层渗透性区域性分布,而局部构造地带控制着不同区块渗透率的非均质性分布。渗透率随着有效垂直应力、有效最大水平主应力和有效最小水平主应力增加均呈负指数减小。相对于地应力差,应力差系数才是影响水力裂缝沿着最大主应力方向扩展的主要因素。

According to the great significance for the study on the effects of geo-stress on coal initial permeability and the expansion fractures during hydraulic frac turing, based on the controlling factors of stress state in coalbed methane (CBM) reservoir, the influence of geo-stress on the permeability and its controlling mechanis m, the paper summarizes the recent progress about geo-stress vs.permeability.The results show that the influencing factors of geo-stress state include three aspects: te ctonism, burial depth and coal lithotypes, dominating by the first and second aspects.The geo-stress generally captured by hydraulic fracturing method and experimenta | test.The current researches focused on the effects of in-situ tectonic stress field characteristics, laboratory and numerical simulation of different geo-stress on coal res ervoir permeability. The essence of its controlling mechanism is the pore-fissure structure deformation in CBM reservoir dynamics.The regional stress field that develope d a regional fissure system controls the regional distribution of coal permeability, whereas the local tectonic zone controls the anisotropic permeability in different block s.The permeability decreases exponentially with increasing the effective vertical stress, the effective maximum horizontal principal stress and the effective minimum hori zontal principal stress.Compared with the geo-stress difference, the coefficient of stress difference is the major factor that affects the expansion of hydraulic fracturing a long the direction of maximum principal stress.

国家科技重大专项资助项目(2016ZX05043-001)；国家自然科学基金资助项目(41602170)；中央高校基本科研业务专项基金资助项目(35732016129)；