页岩水力压裂的关键力学问题

页岩气是指以吸附和游离时而还有流体相的形态状态赋存于泥页岩中的非常规天然气.页岩气开采成为我国绿色能源开发的新领域.尽管北美页岩气革命取得了成功,但目前仍仅有预期产量5~15%的油气采收率,问题出在什么地方?水力压裂被认为是提高采收率的关键一环,但水力压裂过程中复杂缝网的形成和力学控制机理尚不清楚,这给力学家提出了巨大的挑战和机遇.结合本课题组近期研究成果,论文从理论、计算和实验三个方面对页岩水力压裂中的关键基础力学问题进行介绍和总结.主要内容包括发展页岩人工裂缝扩展的大型物理模型实验,建立页岩本构模型和断裂力学理论,发展耦合断裂力学和流体力学的裂缝网扩展数值模拟方法.页岩水力压裂研究对发展断裂力学的实验技术、理论模型和数值模拟方法起到推动作用,对提高我国页岩气高效开采技术具有重要意义.

The Key Mechanical Problems on Hydraulic Fracture in Shale

Shale gas is unconventional natural gas stored in shale in free or absorbed form, and sometimes in free fluid phase. The exploitation of shale gas has become a promising field of green energy development in China. Although great success has been achieved in shale gas revolution in North America with the technique of hydraulic fracturing, only 5~15% of the stored oil and gas could be exploited. In order to improve the production of shale oil and gas, a huge challenge accompanied with great opportunities is presented to the mechanics researchers. Based on the recent study results of our research group, this paper introduces and summarizes the key mechanical problems of shale hydraulic fracturing from the aspects of theory, numerical simulation and experiment. The main contents include developing a large-object experiment, establishing the shale constitutive model and fracture mechanics theory, and developing the numerical simulation method for coupling fracture mechanics and fluid mechanics of fracture network. The investigation on hydraulic fracture is of great significance and innovation and will lay a solid foundation for the physical experiment model, fracture mechanics theory and numerical simulation techniques of effective exploitation of shale gas in China.