滑溜水压裂液与页岩储层化学反应及其对孔隙结构的影响

Chemical reactions and effects of slick water fracturing fluid on the pore structures of shale reservoirs in different deposition environments

为探究页岩气井压裂作业过程中,滑溜水压裂液对不同沉积环境(海相、陆相、海陆过渡相)页岩储层孔隙结构的影响,利用盆地深层流体-岩石相互作用模拟仪,模拟地层条件(100℃,50 MPa)下滑溜水压裂液注入过程中与不同沉积环境页岩的相互作用实验。通过对比反应前与反应72 h后3套页岩样品矿物组成、孔体积和比表面积的变化,对不同类型页岩孔隙结构的变化进行剖析。结果表明,滑溜水压裂液处理后的不同沉积环境页岩矿物组成和孔隙结构都发生了变化。海相页岩反应之后,碳酸盐矿物发生溶蚀,形成大量直径为2~8μm左右的溶蚀孔,导致纳米孔孔体积和比表面积减小。因含有较多的伊/蒙混层矿物,陆相和海陆过渡相页岩遇压裂液容易发生膨胀、分散作用,导致其孔体积及比表面积减小。该实验结果为研究滑溜水压裂液对不同沉积环境页岩储层的物理、化学作用,以及为压裂液的改造提供了一定的科学依据。

In order to study the effects of slick water fracturing fluid on the pore structures of different deposition environments（marine,continental,and marine-continental transitional）shale reservoirs in the process of shale gas exploration,the deep basin fluid-rock interaction experimental device was used to simulate the interaction between the slick water fracturing fluid and different shales in the condition of formation（100℃,50 MPa）.Through comparing the changes in mineral composition,pore volume,and specific surface area of three different deposition environment shales before and 72 h after reaction,the transformation effects of pore structure were analyzed.The results showed that the mineral composition and pore structure of different deposition environment shales changed after reaction with fracturing fluid.After reaction,the carbonate minerals（calcite and dolomite）of marine shale were corroded and many dissolution pores with diameter of 2-8μm occurred,which caused the reduction in pore volume and specific surface of nanopore.Because of the continental shale and marine-continental shale contain a large amount of mixed-layer illite/smectite mineral which is liable to dispersion and swelling when reacting with slick water fracturing fluid,the pore volume and specific surface area of these shales decreased after reaction.The results of this study provide scientific basis for study of the physical and chemical interactions between slick water fracturing fluid and different deposition environment shale reservoirs and of the transformation of fracturing fluid.