Miscibility Process of Hydrocarbon Mixture Gas and Crude Oil: Insights from Molecular Dynamics

Abstract

Using molecular dynamics simulations, we investigate the miscibility process of hydrocarbon mixture gas and crude oil in Tarim Oilfield, which was not well understood from the microscopic points of view. The results show that the increase of the pressure of hydrocarbon mixture gas is favorable for the gas−oil miscibility until the interfaces vanish under a minimum miscible pressure (MMP). The identified MMP (37.3 MPa) is well consistent with the experimental value. With increasing gas pressure, the parallel diffusion coefficients of gas molecules in the gas− oil interfaces decrease, while the perpendicular ones increase. We also analyze the profiles of potential of mean force between different gas and various oil components, identifying the components which dominate the process of gas−oil miscibility from the perspective of molecular forces. In addition, the introduction of gravity in gas flooding slightly increases the MMP. These results can guide the optimization and design of the enhanced oil recovery technology with hydrocarbon mixture gas flooding.

A Regulation Method of the Wettability of Solid Surfaces: Oil–Water Wettability Alteration by Replacing Adsorbed Polar Molecules via Salt Ions

“…The substrate is constrained, and the polar functional groups and ions move in an NVT ensemble during calculations. The grids are divided in the z -direction of the whole system with an interval distance of 0.02 nm, and the number of samples per grid is set to 40 . In the PMF curves, the deeper the potential wells are, the more attractive the substrate with molecules and ions is.…”

“…The grids are divided in the z-direction of the whole system with an interval distance of 0.02 nm, and the number of samples per grid is set to 40. 12 In the PMF curves, the deeper the potential wells are, the more attractive the substrate with molecules and ions is. Obviously, the substrate is more attractive to ions than to polar molecules; among them, the interaction between calcium ions and substrate is the strongest.…”

“…People can but dedicate to regulate the surface wettability by modifying the rock-oil interactions through the addition of chemical species. Low salinity water flooding (LSWF) technology is gaining attention as a tertiary oil recovery technology. − This technology is directed to inject low-concentration ionized water into the oil reservoir to promote the desorption of crude oil and enhance the oil recovery (EOR) rate. − Compared with traditional chemical flooding technology, LSWF is more environmentally friendly and has the advantages of low cost and simple operation . Since Morrow et al , found that oil recovery can be enhanced by injecting low salinity water, a wide range of studies was conducted to show that crude oil can be effectively extracted through LSWF.…”

Critical Contribution of Water in Hybrid CO2/Water Enhanced Shale Oil Recovery: Insights from Molecular Dynamics

“…Enhancing shale oil recovery through fluid injection into shale reservoirs has emerged as a prominent research topic in recent years. − A large number of studies ,− have shown that gas injection is an efficient method to enhance unconventional oil recovery in low permeability shale reservoirs because of its better injectivity and higher sweep efficiency. ,, CO 2 , N 2 , and natural gases are commonly used for injection, in which CO 2 has gained more attention due to its advantages, such as low minimum miscibility pressure . Enhancing shale oil recovery by injecting CO 2 is recognized as a remarkable technology and has attracted higher attention lately, not only because of conquering the energy resource exploitation problems, but also for the possibilities achieving CO 2 storage .…”

“…Molecular dynamics (MD) simulations, in conjunction with experimental techniques, provide powerful methods to study the dynamics, structure, and energetic properties of nanoscale systems, including those encountered in shale oil reservoirs. ,,, MD simulations have been effectively utilized to model fluids in diverse reservoir rocks, such as clays, quartz, carbonates, and kerogen . However, most of the existing research studies involve pure water or gas phase , replacement fluid; little attention has been paid to hybrid fluids.…”