超临界二氧化碳与页岩相互作用机制

Interaction mechanism between supercritical carbon dioxide and shale

李一波 陈耀旺 赵金洲 王志强 魏兵 Valeriy Kadet

Yibo LI Yaowang CHEN Jinzhou ZHAO Zhiqiang WANG Bing WEI Kadet Valeriy

超临界二氧化碳与页岩相互作用机制及规律对页岩油气开发非常重要。目前缺少对超临界二氧化碳注入页岩储层后页岩润湿性、孔隙度和渗透率变化规律的研究。为了明确在不同条件下经过超临界二氧化碳浸泡处理后页岩矿物成分和微观结构的变化规律，以四川盆地龙马溪地区页岩为研究对象，对其总有机碳含量、矿物成分、表面形貌及低压N和CO吸附进行了测试。通过对不同浸泡时间、压力和含水条件下页岩处理前、后的物理性质和微观结构进行定量表征，研究了超临界二氧化碳对页岩孔隙度、渗透率以及润湿性的影响。研究结果表明：①随着浸泡时间和浸泡压力的增加，页岩中的黏土矿物和碳酸盐矿物（方解石和白云石）含量降低，石英含量增加，有机质含量降低明显。②扫描电镜图像显示页岩中微观孔隙结构变化受萃取作用、溶蚀作用和吸附膨胀作用共同影响。页岩中微观孔隙结构的变化导致了页岩孔隙度和渗透率的改变。页岩渗透率变化受到黏土矿物、碳酸盐矿物和有机质含量的影响。③超临界二氧化碳浸泡处理后页岩的润湿性发生改变，随着浸泡时间和压力的增加，页岩-水接触角增大，页岩的润湿性由强水湿转变为弱水湿和中等润湿。

Understanding the mechanism and pattern of interactions between supercritical carbon dioxide （SC-CO） and shale is crucial to the exploitation of shale oil and gas. However， there is a lack of studies on the changes in shale wettability， porosity， and permeability after SC-CO injection into shale reservoirs. In this study， the changes of mineral composition and microstructures of shales are quantitatively characterized before and after SC-CO soaking under different soaking time， pressure and fluid type， while taking the shales in the Longmaxi area in the Sichuan Basin. Analyses and tests of the total organic carbon （） content， mineral composition， surface morphology， and low-pressure N and CO adsorption of shales are conducted， and the impacts of SC-CO on shale porosity， permeability， and wettability are explored. The results indicate that an increase in the soaking time and pressure leads to a decrease in the contents of clay and carbonate minerals （i.e.， calcite and dolomite）， while an increase in the quartz content results in a significant decrease in the organic matter content in shales. The scanning electron microscopy （SEM） images reveal that the changes in the microscopic pore structures of shales are jointly affected by extraction， dissolution， and adsorption-induced swelling and， on the other hand， further alter shale porosity and permeability. Additionally， the variation in shale permeability is influenced by the contents of clay minerals， carbonate minerals， and organic matter. The shale wettability also changes after soaking in SC-CO. Specifically， as the soaking time and pressure increase， the shale-water contact angle enlarges， with the shale transitioning from strong hydrophilic to weak and moderate hydrophilic type.

10.11743/ogg20240420