页岩储层的体积压裂能有效沟通天然裂缝使其形成缝网系统,极大地提高了页岩气的产能,让页岩气的开采尽快获得经济效益,因此对体积压裂缝网形成研究显得尤为重要,在对国内外大量页岩储层测试数据和体积压裂缝网形成研究成果全面系统调研和深入分析,息结的基础之上,认为页岩储层体积压裂缝网的形成主要受控于3个方面的因素:①储层本身质量好,高的脆性矿物含量、杨氏模量,低的断裂韧度、泊松比、应力衰减速率和储层敏感一陛等,即储层的可压裂性越高,越易形成缝网;②地质背景条件优越,低的应力各向异性、天然裂缝发育、小的逼近角等,利于压裂裂缝延伸并扩展成缝网;③压裂工程措施适当,包括起裂方位和压力、支撑剂及压裂液性能、施工液量及排量等施工参数设计合理,有利于水力裂缝的充分扩展;另外,对以上控制因素的评价方法主要有室内实验、软件数值模拟及现场监测等,这些认识对体积压裂缝网形成机理研究及压裂优化设计具有重要的理论价值和实践意义。
Volume fracturing in shale reservoirs can effectively connect the natural fractures for forming fracture network system. It can enormously improve the productivity of shale gas, and obtain the economic benefits of shale gas exploitation as soon as possible. Thus, the fracture network formation of volume frac- turing is particularly important. On the basis of the literature research of volume fracturing research find- ings and shale's test data around the world, research shows the fracture network formation of volume frac- turing is mainly influenced by three controlling factors. According to quality of shale reservoirs, higher brittle mineral contents of rock and Young modulus, lower fracture toughness, Poisson's ratio, strain en- ergy release rate, and reservoir sensitivity (good fracture-ability) will be constructive to easier formation of fracture network. According to favorable geological background conditions, lower stress anisotropy, better developed natural fractures and smaller approaching angle can be good for better extension and prop- agation for hydraulic fractures extending into network. According to opportune engineering conditions of fracturing operations, including the pressure and orientation of fracture initiation, the performance of proppant and fracturing fluid and fluid volume and pump delivery of fracturing and so on, their rational use will be more helpful to the formation of fully propagated fracture-network. Additionally, the evaluation methods of the above controlling factors are laboratory experiments, numerical simulation software and fracturing monitoring. This study has important theoretical value and practical significance to the under- standing of shale reservoir's fracture-network formation mechanism and can improve the science of shale reservoir fracturing desiun.