Dong Zhentao, Xue Haitao, Li Bohong, Tian Shansi, Lu Shuangfang, Lu Shudong
Key Laboratory of Deep Oil and Gas (China University of Petroleum (East China)), Qingdao 266580, P. R. China.
China Petroleum Logging Co., Ltd., Xian, Shanxi, 710000, China.
J Nanosci Nanotechnol. 2021 Jan 1;21(1):85-97. doi: 10.1166/jnn.2021.18468.
Wettability is an important physical property of shale. This parameter is related to the shale material composition and the fluid properties in the shale pores and plays an important role in the exploration and development of shale oil. Wettability is affected by the scale and roughness. The contact angle at the nanoscale on a smooth surface can better reflect the wettability of shale than the contact angle at higher scales. Molecular dynamics simulations can be used to measure the contact angle on a smooth surface at the nanoscale. This paper focuses on the effects of organic matter and minerals in shale and different components of shale oil on shale wettability. Wetting models of "organic matter-oil component-water," "quartz-oil component-water" and "kaolinite-oil component-water" at the nanoscale were constructed. Molecular dynamics simulation was used to study the morphological changes of different oil components and water on different surfaces. Studies have shown that organic matter is strongly oleophilic and hydrophobic. Polar components in shale oil can make organic matter slightly hydrophilic. It was recognized by quartz wettability experiments and simulation methods at the nanoscale that the cohesive energy of a liquid has a significant influence on the degree of spreading of the liquid on the surface. The "liquid-liquid-solid" wettability experiment is an effective method for determining mineral oleophilic or hydrophilic properties. The nanoquartz in the shale is strongly hydrophilic. The water wetting angle is related to the crude oil component. Nanokaolinite can have a tetrahedral or an octahedral surface; the tetrahedral surface is oleophilic and hydrophobic, and the octahedral surface exhibits strong hydrophilicity. The wettabilities of both surfaces are related to the crude oil component.
润湿性是页岩的一项重要物理性质。该参数与页岩材料组成以及页岩孔隙中的流体性质相关，在页岩油勘探开发中起着重要作用。润湿性受尺度和粗糙度影响。光滑表面上纳米尺度的接触角比更大尺度的接触角能更好地反映页岩的润湿性。分子动力学模拟可用于测量纳米尺度光滑表面上的接触角。本文聚焦于页岩中的有机质和矿物以及页岩油的不同组分对页岩润湿性的影响。构建了纳米尺度下“有机质 - 油组分 - 水”“石英 - 油组分 - 水”和“高岭石 - 油组分 - 水”的润湿模型。利用分子动力学模拟研究不同油组分和水在不同表面上的形态变化。研究表明，有机质具有很强的亲油性和疏水性。页岩油中的极性组分可使有机质略带亲水性。通过纳米尺度的石英润湿性实验和模拟方法认识到，液体的内聚能对液体在表面的铺展程度有显著影响。“液 - 液 - 固”润湿性实验是确定矿物亲油或亲水性质的有效方法。页岩中的纳米石英具有很强的亲水性。水润湿性角度与原油组分有关。纳米高岭石可具有四面体或八面体表面；四面体表面亲油且疏水，八面体表面表现出很强的亲水性。两个表面的润湿性均与原油组分有关。
