深层页岩气水平井储层压裂改造技术

四川盆地南部深层页岩气资源量大,但由于埋藏深、构造复杂,适于3 500 m以浅页岩气储层的分段体积压裂主体工艺技术在3 500 m以深页岩气储层的压裂改造中出现了不适应性,难以形成复杂缝网。为此,借鉴埋深为3 500 m以浅的页岩气实现规模效益开发的压裂工艺技术,结合深层页岩的构造与储层特征,形成了一套适合于深层复杂构造页岩气水平井的储层改造技术,并在渝西地区深层页岩气井的压裂改造中进行了现场实践。研究结果表明:①天然裂缝综合预测技术实现了对天然裂缝带的精细刻画及天然裂缝发育强度的定量预测,为后续压裂施工优化提供了依据;②在页岩储层可压性评价参数中,脆性指数、缝网扩展能力指数及含气性指数越大,储层可改造潜力越大、气井增产效果越好;③采用大规模前置液工艺,"高强度注液、低孔数、低浓度段塞式加砂"工艺,以及实施暂堵转向的缝网复杂度提升工艺,单井储层增产改造体积(SRV)与产能得到了有效提升。结论认为,所形成的储层改造技术适用于深层页岩气储层的压裂改造作业,可以为同类型页岩气井的压裂施工提供借鉴。

Horizontal well fracturing stimulation technology for deep shale gas reservoirs

There are huge shale gas resources in the deep reservoirs of southern Sichuan Basin, but due to their great burial depth and complex structures, the main technology of staged stimulated reservoir volume (SRV) suitable for the shallow shale gas reservoirs lower than 3 500 m is not applicable to the fracturing stimulation of deep shale gas reservoirs over 3 500 m and can hardly generate complex fracture networks. In this paper, a set of reservoir stimulation techniques based on horizontal well suitable for the shale gas reservoirs in deep complex structures were developed referring to the fracturing techniques used for the large-scale benefit development of shale gas above 3 500 m, combined with the structural and reservoir characteristics of deep shale. And they were applied on site to the fracturing stimulation of deep shale gas wells in the western Chongqing area. And the following research results were obtained. First, by virtue of the comprehensive natural fracture prediction technique, the natural fracture belts are characterized precisely and the development intensity of natural fractures is predicted quantitatively, so as to provide a basis for the optimization of subsequent fracturing operations. Second, among the parameters for evaluating the fracability of shale reservoir, the higher the brittleness index, fracture network propagation index and gas content index, the greater the reconstruction potential of reservoirs and the better the stimulation effect of gas wells. Third, the adoption of large-scale prepad fluid technique, "intense liquid injection, small number of perforations, and proppant injection of low-concentration slug type" technique and temporary plugging and diversion technique for improving the complexity of fracture networks increases single-well SRV and productivity effectively. In conclusion, the reservoir stimulation techniques developed in this paper are suitable for the fracturing stimulation of deep shale gas reservoirs and can be used as reference for the fracturing operations of similar shale gas wells.