页岩气开采压裂技术分析与思考

FRACTURING TECHNOLOGY FOR SHALE GAS

页岩层较为致密,且渗透率较低,在天然状态下难于直接开采出页岩气。现阶段主要采用水力压裂技术产生人工裂缝,同时使天然裂缝间能够互相贯通,获得较为复杂的裂缝网格,以期增加页岩气层的连通性和流动性,提高页岩气产能,最终获得可观的开采量。然而,利用水力压裂技术改造天然的页岩储层过程中,也引发了如有效体积压裂、压裂液的合理选择、清水的耗费、环境污染及压裂液的返排等问题。通过分析现存的各种压裂技术的优缺点和适用性,依据中国特有的地质地貌特征,提出解决这些问题的方法和建议。从微观和宏观尺度研究页岩体积压裂断裂机制,为体积压裂工艺设计提供理论依据。

With tight framework and low permeability, shale bed is difficult to be recovered directly in a natural state. At present, a technology of hydraulic fracturing is mainly adopted to make some induced fractures, further to connect them with natural ones. Then a complex fracture grid can be obtained so as to improve the connectivity and flowability of a shale-gas layer, increase the productivity, and finally acquire the considerable gas production. However, there are some problems occurring in this fracturing stimulation, including selection of both effective volume fracturing and fracturing fluid, water consumption, environmental pollution, and fracturing fluid flowback. Through analyzing advantages, disadvantages, and applicability of this existing fracturing technology, this paper puts forward some suggestions and measures against these problems. In addition, the mechanisms of volume fracturing are studied in micro and macro scales, in order to provide a theoretical basis for its design.