Effects of slick water fracturing fluid on pore structure and adsorption characteristics of shale reservoir rocks
Effects of slick water fracturing fluid on pore structure and adsorption characteristics of shale reservoir rocks
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滑溜水压裂液对页岩储层孔隙结构及吸附特征的影响
DOI：
10.1016/j.jngse.2017.12.030
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发表时间：
2018
影响因子：
--
通讯作者：
Yang Hui
中科院分区：
文献类型：
--
作者：
Sun Zepeng;Zhang Hailong;Wei Zhifu;Wang Yongli;Wu Baoxiang;Zhuo Shengguang;Zhao Zhe;Li Jing;Hao Lewei;Yang Hui
页岩-压裂液相互作用及其对页岩孔隙结构和吸附特性的影响是影响页岩气勘探的关键因素。为了解决这一问题，利用流体-岩石相互作用模拟仪，在100 °C、50 MPa的模拟条件下，对取自四川盆地下志留统龙马溪组的黑色页岩样品进行了72 h的滑溜水压裂液暴露试验。滑溜水压裂液含有0.2重量%的减摩剂，1重量%粘土控制剂，0.15重量%清洁剂和0.05重量%破乳剂采用X射线衍射（XRD）、场发射扫描电镜（FE-SEM）、低压氮气吸附和甲烷等温吸附实验，采用重量法测定了滑溜水压裂液处理前后页岩样品的矿物组成、孔结构和甲烷吸附量。结果表明，碳酸盐矿物在处理过程中发生溶解，形成了许多直径2-5 μm的溶孔，而其它矿物相对未受影响。反应后泥页岩样品的比表面积和总孔体积减小，泥页岩-压裂液相互作用对中孔的影响更大。然而，反应后纳米孔的平均孔径增大，从4.29 nm增加到4.78 nm。分形维数的变化表明，孔表面粗糙度增加，孔结构变得更加规则。压裂液处理后页岩的甲烷吸附量由1.23mmol/g降低到0.95mmol/g。页岩孔隙结构和吸附特性的变化会影响气体的流动和气体吸附能力。这些结果表明，滑溜水压裂液在页岩基质增产中可能发挥重要作用。
The shale-fracturing fluid interaction and its effects on the pore structures and adsorption characteristics of shale are the key factors affecting shale gas exploration. To address this problem, the black shale samples obtained from the Lower Silurian Longmaxi Formation in Sichuan Basin, China were exposed to slick water fracturing fluid at the simulation conditions of 100 °C and 50 MPa for 72 h through a fluid-rock interaction simulation instrument. The slick water fracturing fluid contained 0.2 wt.% friction reducer, 1 wt.% clay control agent, 0.15 wt.% cleanup agent and 0.05 wt.% demulsifier. The mineral composition, pore structure and methane adsorption capacity of shale samples before and after slick water fracturing fluid treatment were measured by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), low-pressure nitrogen adsorption and methane isothermal adsorption experiments using the gravimetric method. The results showed that the carbonate minerals were dissolved during treatment, and as a result, the samples developed many dissolution pores measuring 2–5 μm in diameter, while the other minerals remained relatively undisturbed. The specific surface area and total pore volume of shale sample were reduced after the reaction, and the shale-fracturing fluid interaction exhibited a stronger influence on the mesopores. However, the average pore diameter of nanopore was enlarged after the reaction, increasing from 4.29 nm to 4.78 nm. The changes of fractal dimensions suggested an increase in the roughness of pore surfaces, and the pore structure became more regular. The methane adsorption capacity in shale treated with fracturing fluid was reduced from 1.23 mmol/g to 0.95 mmol/g. The changes in the pore structure and adsorption characteristics of shale could affect the gas flow and gas adsorption capacity. These results indicated that the slick water fracturing fluid may play an important role in shale matrix stimulation.