MOLECULAR SIMULATION OF OIL-BRINE INTERACTIONS ON CLAY SURFACES

Low Salinity Water Flooding (LSWF) has been a well-studied EOR method, with several experimental and theoretical scientific papers published in peer-reviewed journals over the last few decades. Despite this, there is still a debate about the dominant mechanisms underlying this complex EOR process, and some issues remain a mystery. The scale of investigation, which ranges from sub-pore scale (atomic and electronic scale) to pore scale, core scale, and reservoir scale, contributes to the complexity. In the last decade, Molecular Dynamics (MD) simulation has been used as a research tool to investigate the nano-scale interactions between reservoir rock, crude oil, and brine systems in the presence of impurities (e.g., clay minerals). The interaction mechanisms between the oil and brine layers in the presence of a Na-MMT clay layer were investigated in this thesis. For the oil layer, 18 decane molecules and 5 decanoate molecules were used. Brine layers with varying ionic contents were created, with the majority containing NaCl and CaCl2, as it was discovered that both NaCl alone and NaCl with CaCl2 are good ionic contents for mobilizing polar decanoate anions in the oil layer in brine composition. The simulations were carried out in either NVT or NPT ensembles. According to the computational results, the polar decanoate ions mostly interact with the Na-MMT via an ion-dipole interaction between the oil's polar oxygen atoms and the clay's Na ions. Furthermore, it was discovered that for more realistic and accurate MD simulations, clay layers must be constrained, and simulation boxes should be dense. Moreover, when the Clay/Oil/Brine/Oil system was simulated, it was discovered that the lower the salinity, the greater the water mobility, and the lower the water/oil intersection. Temperature and pressure also play an important role, as it was discovered that high temperatures and pressures of 410K, 0.03 GPa, and 360K, 0.01 GPa produce good MD Finally, MD simulations of sour gas injection were run to compare the results to those of low salinity water flooding. Because no H2S and oil separation was observed after 5 ns of simulation, it was concluded that the sour gas injection method is less efficient than low salinity water flooding. Furthermore, more research in this area is required