陆相与海相页岩水相润湿渗吸特征

针对鄂尔多斯盆地延长组陆相页岩和四川盆地龙马溪组海相页岩开发现状,研究了不同沉积环境下各层位页岩水相作用特征。实验选取了西北地区富页、延页和云页等页岩气探井岩心,对比涪陵气田焦石地区钻井岩心,进行了矿物组分分析、自然孔隙观察和岩石力学测试,探索了页岩表面水相接触角和基质自发渗吸。实验结果表明：陆相页岩黏土矿物含量更高,易水敏导致储层伤害;涪陵地区海相页岩气储层基质较为致密,裂隙形态简单,填充物少,微裂隙和微孔隙较陆相延长组发育更充分;脆性矿物含量高导致涪陵地区页岩杨氏模量和泊松比较大,利于提高改造体积和裂缝复杂度;页岩表面表现为强亲水性,不同层位页岩水相润湿性存在差异,不同类型表面活性剂对页岩润湿性作用效果不同;通过调整减阻剂、粘土稳定剂和表活剂能够促进水相对页岩基质的浸润。研究可见不同层位页岩与水相作用差异明显,需研究开发具有针对性液体体系。

Study on characteristics of wettability and imbibition between continental and marine shales

In view of the development status of continental shale of Yanchang Formation in Ordos Basin and marine shale of Longmaxi Formation in Sichuan Basin, the characteristics of shales in different sedimentary environments were discussed. Shale cores from wells of Fuye, Yanye and Yunye were selected in the experiment, compared with cores from wells of Fuling gas field. Mineral composition analysis, natural pore observation and rock mechanics tests were carried out, water contact angle of shale surface and spontaneous imbibition test of matrix were explored. The experimental results show: The continental shales have higher mineral content and easy to cause reservoir damage by water sensitivity; the marine shale gas reservoir in Fuling area has more denser matrix, more average fracture morphology, fewer fillers, and more fully developed micro-fractures and micro-pore than the continental Yanchang Formation; the high content of brittle minerals results in larger Young"s modulus and Poisson"s ratio of the shale in Fuling area, which is beneficial to improving the stimulated reservoir volume and fracture complexity; Shale surface shows strong hydrophilicity, with different water wettability varies, and different types of surfactants have different effects on shale wettability. By adjusting drag reducing, clay stabilizer and surfactant, imbibition of water into shale matrix can be promoted. It can be seen from the study that the interaction between shale and water in different structural position is obviously different, and it is necessary to study and develop specific liquid systems.