考虑氧化作用的富有机质页岩吸附水量

页岩气井大型水力压裂后压裂液返排率普遍较低，滞留压裂液可能诱发页岩产生裂缝，但在水力裂缝与天然裂缝中占据有效气体传输通道，影响压裂效果。选取四川盆地龙马溪组典型富有机质页岩，采用填砂管与粒状页岩模拟体积改造的页岩气层，开展了蒸馏水与氧化液体积改造后页岩气层吸附水量的对比实验，明确了氧化对压裂液渗吸分散到裂缝附近基块孔隙的作用与机理。结果表明，与蒸馏水相比，氧化作用可以增强页岩渗吸分散水相作用，降低页岩孔隙空间内的自由水量，增加页岩吸附水量；富有机质页岩氧化作用消耗有机质，分解有机黏土复合体，裂缝与孔喉壁面更多的黏土矿物接触压裂液，增加黏土矿物吸附水量，降低裂缝面及基块孔隙含水饱和度，释放渗流空间。建议根据具体工程地质特征，优选氧化性流体的加入时间及用量，充分发挥滞留氧化性压裂液的造缝能力，促进压裂液渗吸分散，实现压裂液少返排或零返排，增大气体在裂缝中有效渗流通道。

Water Absorption of Organic Shale with Oxidation

Shale gas reservoirs generally need to be fractured for the industrial production. However, the flowback of fracturing fluid is low. Residual fracturing fluid can induce fracture in shale gas reservoir, but it also occupy seepage channels in shale gas reservoirs. This paper takes typical organic rich shale samples from the Longmaxi Formation in the Sichuan Basin, and recoustructed the fractured shale gas reservoir by sand pack and granular shale. Through comparative experiments of water absorption of shales treated with water and oxidation liquid, we find out mechanism of oxidation effect on fracturing fluid imbibition and dispersion to pore of matrix near fracture. The experiment results show that the liquid imbibition range increase after oxidation of granular shale, free water in shale pore space decreases and water absorbtion of increases. It is concluded that the oxidation-induced dissolution of organic matter can increase the contact area between water and clay minerals, and promote the imbibition of clay minerals and the growth of micro-fractures. The water saturation of fractures decreases, and increase seepage channels of gas. It is suggested to optimize the formula of fracturing fluids and the soak system according to the specific engineering geological characteristics, and optimize the adding time and amount of oxidizing fluid. so as to improve to the fracturing capacity of the retained oxidizing fracturing fluid, promoting the dispersion of fracturing fluid, minimize the return of fracturing fluid, and to increase effective seepage channels of gas in fractures.