天然裂缝影响下的复杂压裂裂缝网络模拟  

Simulation of a complex fracture network influenced by natural fractures

作　　者：赵金洲[1] 李勇明[1] 王松[1] 江有适[1] 张烈辉[1] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.西南石油大学

出　　处：《天然气工业》2014年第1期68-73,共6页Natural Gas Industry

基　　金：新世纪优秀人才支持计划(编号:NCET-11-1062);国家自然科学基金(编号:51344005);四川省杰出青年学术技术带头人资助计划(编号:2012JQ0010);国家杰出青年基金(编号:51125019)

摘　　要：水力压裂缝与页岩储层中的天然裂缝沟通后,多因素影响下的起裂与延伸变化规律将决定裂缝网络的几何尺寸及复杂程度。根据断裂力学基础理论,引入裂缝起裂与延伸判定准则来研究裂缝延伸过程中角度变化趋势及延伸压力影响因素。在此基础上建立页岩气压裂复杂裂缝数学模型,分析不同岩石力学参数、地应力分布、裂缝物性参数以及施工参数对裂缝网络形态的影响。求解过程中以等压力梯度值划分裂缝延伸方向上的计算节点,能在迭代拟合流量分布之前显式求解裂缝几何参数,加快求解速度;将起裂与延伸准则作为分支缝扩展依据,能避免常规拟三维裂缝模拟中对缝长延伸的拟合,减少迭代次数。模拟结果表明,优选天然裂缝发育、地应力差较小的储层是形成缝网的充分条件;通过暂堵、转向等方式保持较高的缝内压力有利于分支缝以较大的曲率半径延伸更远的距离,扩大增产作用区域;模拟得到的缝网形态能够与现场微地震测试数据点的存在范围、分布密度实现较好地吻合,佐证了上述模型的准确性。When hydraulic fractures intersect mined by the initiation and propagation under with natural fractures, the geometry and the impact of various factors. Based on the complexity of a fracture network are deter fracture mechanics, the criteria for initiation and propagation of a fracture were introduced to analyze the tendency of a propagating angle and the impacts of propagating pressure. On this basis, a novel model with a complex fracture network of a shale gas well was established to investigate how the fracture net work form changes with different parameters, such as rock mechanics, in situ stress distribution, fracture properties, and frac treat- ment parameters. The solving process in this model was accelerated by classifying the calculation nodes on the extending direction of the fracture by equal pressure gradients, and solving the geometrical parameters prior to the iteration fitting flow distribution. With the initiation and propagation criteria as the bases for the propagation of branch fractures, this method decreased the iteration times through eliminating the fitting of the fracture length in conventional 3D fracture simulation. The simulation results indicated that the formation with abundant natural fractures and smaller in-situ stress difference are sufficient conditions for fracture network forma- tion. If the pressure in the hydraulic fractures can be kept at a high level by temporary sealing or diversion, the branch fractures will propagate further with minor curvature radius, thus enlarging the reservoir stimulation area. Compared with the field microseismic mapping, the simulated configuration of the fracture network can be well matched in presenting ranges and distribution density, which validates the accuracy of this model.

关 键 词：页岩气 水力压裂 起裂与延伸准则 延伸角 延伸压力 裂缝网络 复杂裂缝模型 

分 类 号：TE37[石油与天然气工程—油气田开发工程]