공극 규모에서의 초임계상 이산화탄소 거동 가시화를 위한 마이크로모델의 개발과 적용

Abstract

Geological CO2 sequestration is one of the most important technologies to mitigate greenhouse gas emission into the atmosphere by isolating great volumes of CO2 in deep geological formations. Despite of significant effects on macroscopic migration and distribution of injected CO2, however, only a limited information is available on wettability in microscopic scCO2-brine-mineral systems. In this study, a micromodel had been developed to improve our understanding of how CO2 flooding and residual characteristics of pore water are affected by the wettability in scCO2-water-glass beads and scCO2-water-quartz sands systems. The micromodel (a transparent pore structure made of glass beads or quartz sands between two glass plates) in a pressurized chamber provided the opportunity to visualize spread of supercritical CO2 and displacement of porewater in high pressure and high temperature conditions. CO2 flooding followed by fingering migration and dewatering followed by formation of residual water were observed through an imaging system with a microscope. Measurement of contact angles of residual porewater and areal displacement of porewater by scCO2 in a micromodel under various conditions such as pressure, temperature, salinity, flow rate, etc. were conducted to estimate displacement efficiency in a micromodels. The measurement revealed that the porewater (deionized water or NaCl solutions) is a wetting fluid and the surface of micromodels are water-wet. It is also found that the contact angle at equilibrium decreases as the pressure decreases, whereas it increases as the salinity increases. Also, the displacement efficiency at equilibrium decreases as the salinity decreases, whereas it increases as the pressure and temperature increases. The experimental observation results could provide important fundamental information on capillary characteristics of reservoirs.