页岩气储层水力裂缝网络的延伸规律

Hydraulic Fracture Network Propagation Rule of Shale Reservoir

为了深入认识页岩气储层水力压裂裂缝的延伸规律及裂缝网络形成条件,通过建立页岩气储层水力裂缝延伸的二维模型,分析地应力差异系数、天然裂缝及层理面等因素对水力裂缝延伸方向的影响规律,并对页岩储层水力裂缝网络的形成机制进行研究.研究结果表明:水力裂缝在层理面内转向、分岔及沟通天然裂缝是形成裂缝网络的关键,层理面和天然裂缝逼近角和地应力差异系数需在一定临界组合条件下才形成裂缝网络,偏离该条件均形成单一裂缝;最大水平主应力方向与页岩的层理面和开度较好的天然裂缝之间的逼近角呈大角度时,更有利于形成裂缝网络.

To deeply understand the hydraulic fracturing crack propagation rule of shale gas reservoir and crack network formation conditions,a two-dimensional model of hydraulic fracture extension in shale was established.The influence of in-situ stress difference coefficient,natural fracture and bedding plane on hydraulic fracture extension was analyzed,and the mechanism of hydraulic fracture network formation was studied.The results showthat the steering and bifurcation of hydraulic fracture along the bedding plane and coalescence into natural fracture are the keys to the formation of crack network.Crack network can form on condition that the approaching angle between bedding plane and natural fractures and the stress difference coefficient are combined properly with critical values,or a single crack will form.The fracture network in shale gas reservoir is easy to form when the angle is large between the maximum horizontal principal stress direction and bedding plane or natural open fracture.