煤储层水基压裂液用表面活性剂的筛选实验

Laboratory study on screening and optimizing surfactant of water-based fracturing fluid for coalbed methane reservoir

水力压裂会对煤储层造成水锁伤害,在压裂液中加入表面活性剂是减缓水锁伤害的有效途径。采用1.5%KCl溶液为基液,在其中加入不同浓度的阴离子型表面活性剂AS和非离子型表面活性剂NS,配置出8种压裂液,分别对河东煤田柳林沙曲矿的焦煤样和太原西山屯兰矿的瘦煤样进行静置沉降实验、毛细管压力测试和离心分离实验,最终优选出煤储层水基压裂液用最佳表面活性剂为0.05%AN复配溶液(AS:NS=9:1),由此构成了表面活性剂压裂液(1.5%KCl+0.05%AN)。研究结果表明,在水基压裂液中加入0.05%AN复配溶液(AS:NS=9:1),可以大幅度降低压裂液的表面张力,改变压裂液的界面状态,从而增加煤表面的亲水性,降低煤孔隙的毛细管压力,使得压裂液的可排性增强,进而能够有效控制储层的水锁伤害,实现增产。

Hydraulic fracturing can cause water blocking dasmage to coal reservoir, and adding surfactant to water-based fracturing fluid is an effective way to mitigate this damage. In this paper, 1.5% KCl solution was used as the base fluid, adding surfactant with different types and concentrations; 8 types of fracturing fluids were prepared, used for coal dust sedimentation experiment, contact angle measurement, surface tension measurement and centrifugal separation test with coking coal in Liulin zone of Hedong Coal Field and lean coal of Xishan Coal Field of Taiyuan, 0.05% AN combination solution was selected as the best surfactant system, which led to the composition of 1.5%KCl＋0.05%AN active fracturing fluid. This fracturing fluid changed the wettability of coal reservoir, and the low surface tension of the fracturing fluid can decrease the capillary pressure, and the water blocking damage of coal reservoir will be controlled so as to decrease the start-up pressure gradient and increase the permeability. Regarding to the coalbed methane reservoir, the surfactant fracturing fluid（1.5%KCl＋0.05%AN） has the stimulation effect, reduces the capillary pressure of fluid in coal pore, making the fracturing fluid easily access into the coalbed methane reservoir, thus significantly reducing the water blocking damage.