Evaporation Process and Pore Size Distribution in Tight Sandstones: A Study Using NMR and MICP

Measurement and Visualization of Tight Rock Exposed to CO2 Using NMR Relaxometry and MRI

Understanding mechanisms of oil mobilization of tight matrix during CO₂ injection is crucial for CO₂ enhanced oil recovery (EOR) and sequestration engineering design. In this study exposure behavior between CO₂ and tight rock of the Ordos Basin has been studied experimentally by using nuclear magnetic resonance transverse relaxation time (NMR T₂) spectrum and magnetic resonance imaging (MRI) under the reservoir pressure and temperature. Quantitative analysis of recovery at the pore scale and visualization of oil mobilization are achieved. Effects of CO₂ injection, exposure times and pressure on recovery performance have been investigated. The experimental results indicate that oil in all pores can be gradually mobilized to the surface of rock by CO₂ injection. Oil mobilization in tight rock is time-consuming while oil on the surface of tight rock can be mobilized easily. CO₂ injection can effectively mobilize oil in all pores of tight rock, especially big size pores. This understanding of process of matrix exposed to CO₂ could support the CO₂ EOR in tight reservoirs.