含煤系产层组多气合采水力裂缝穿层致裂机理研究

含煤系产层组（砂-煤）赋存的致密砂岩气和煤层气合采可以提高累计产量，延长生产周期，但在压裂改造砂-煤组合层时常会遇到起裂时裂缝难以沟通砂-煤互层、容易砂堵、主裂缝扩展不充分等问题，其核心问题是在地应力空间中对产层组压裂产生的非平面多裂缝起裂及穿层扩展机理认识不清。因此有必要开展产层组岩石变形破坏和断裂实验，探索流-固耦合条件下产层组损伤断裂机理及规律，建立产层组力学本构关系和I、II与III型断裂韧性模型。研究水力裂缝在砂-煤岩性过渡带中扭曲扩展的数学模型，提出三维空间水力裂缝穿层扭曲扩展的判别准则，形成非平面多裂缝扭曲扩展控制理论，通过砂-煤组合的真三轴压裂物模实验验证，揭示水力裂缝非平面扩展规律与层间胶结面的交互作用机理，解决穿层致裂时裂缝转向、扭曲并同时与层间胶结面相互作用的理论难题，形成产层组压裂裂缝可控的理论和可行性方法，解决制约鄂尔多斯东缘多气合采压裂时的瓶颈理论和工程难题。

The accumulated gas production and production cycle would be significantly increased by exploiting the unconventional gas resources of coalbed methane and tight gas jointly in coal measure strata (tight sandstone-coal Interbedding reservoir). However, difficulties of insufficient interaction between sandstone-coal Interbed, sand blocking as well as limited main fracture propagation might be encountered during simulation process due to the clouds on mechanisms of nonplanar propagation and penetration of fractures networks. In which case, experiments considering formation rock sample deformation and fracturing needed to be conducted to understand formation fracturing mechanism and establish mechanics constitutive relations as well as the type I, II and III fracture toughness models with fluid-solid coupling method. Mathematical model of the hydraulic fracture distortion in the sand-coal lithologic transition zone and criterion of the distortion propagation of the hydraulic fractures in the 3D space were also studied. A control theory of the non-planar multi-fractures distortion propagation was thus established. Through true triaxial fracturing experiment of sand-coal interbed, the interaction mechanism between non-plane propagation of hydraulic fractures and cementing property of layer interface is revealed, which can be used to solve the problem of uncertainty of propagation orientation during fracture interlayer penetration. A theory and an operable engineering method were thus formed to solve the problem when fracturing before jointly exploitation of coalbed methane and tight gas on the eastern margin of Ordos.