Molecular Simulation Study of Rock-Water-Oil Systems

石油开采是一项重要的世界性事业，具有重要的社会、经济和环境影响。当从地下油藏中开采石油时，只有大约10%的石油通过压力和泵送被开采出来。二次和三次采油方法用于提取剩余的石油，分别涉及对油井进行物理和化学增产。其中一种增产技术是向地下注入高盐度盐水或表面活性剂（肥皂）。这些化学物质不仅取代了石油，而且还改变了石油与地下岩石的化学相互作用或“润湿性”。减少岩石“抓住”石油的化学相互作用有助于石油的采收率。润湿行为是如何随着储层条件的变化而演变的还不完全清楚。该项目使用计算工具来探测决定润湿行为的分子相互作用，并阐明储层大环境与岩石、油、盐水/表面活性剂的微观细节之间的联系。本研究项目采用分子模拟的方法来探测润湿现象，包括盐水-油和盐水-矿物界面的分子相互作用。已知这些界面性质会影响毛细压力，而毛细压力是决定多孔岩石润湿性的关键因素。该项目还量化了酸、碱和沥青质在岩石表面的吸附程度，以及这种吸附改变岩石表面化学和岩石-盐水-油界面相互作用的潜力。润湿性随温度、表面浓度和表面化学特性的变化程度将阐明润湿性如何随储层条件的变化而变化。表面活性剂在改变界面相互作用中的作用也在探索中。由于这个系统非常复杂，项目目标是建立宏观性质与微观结构之间的定量关系。这些关系将有助于合理设计安全、高效、环保的石油开采解决方案。学生们正在接受表面热力学、统计力学和计算机模拟方面的训练。在当地高中开展的外展活动正在教育学生工程学研究对社会和日常生活的影响。

Oil recovery is an important world-wide enterprise with significant social, economic, and environmental impacts. When oil is extracted from an underground reservoir, only about 10% is removed via pressure and pumping. Secondary and tertiary recovery methods are used to extract the remainder of the oil, and these involve physical and chemical stimulation of the oil well, respectively. One such stimulation technique is the injection of a high salinity brine or surfactants (soaps) into the subsurface. These chemicals not only displace the oil, but also alter the chemical interaction, or "wetting", of the oil with subsurface rock. Decreasing the chemical interaction by which the rock "holds onto" the oil facilitates oil recovery. How wetting behavior evolves with changing reservoir conditions is not fully understood. This project uses computational tools to probe molecular interactions that dictate the wetting behavior and to elucidate the connection between the larger environment of the reservoir with the microscopic details of the rock, oil and brine/surfactant. This research project uses molecular simulations to probe wetting phenomena, including molecular interactions at the brine-oil and brine-mineral interface. These interfacial properties are known to affect capillary pressure, which is the key determinant in the wettability of porous rock. The project also quantifies the extent to which acids, bases, and asphaltenes adsorb onto the rock surface, and the potential of this adsorption to change both rock surface chemistry and rock-brine-oil interfacial interactions. The extent to which wettability evolves with temperature, surface concentration, and the chemical identity of the surface will elucidate how wettability evolves with changing reservoir conditions. The role of surfactants in altering interfacial interactions is also being explored. As this system is quite complex, the project goal is to develop quantitative relationships that connect macroscopic properties to microscopic structure. These relationships will enable the rational design of safe, efficient, and environmentally friendly solutions for oil extraction. Students are being trained on surface thermodynamics, statistical mechanics, and computer simulations. Outreach activities to area high schools are educating students about the impact of engineering studies on society and everyday life.