资源环境科技发展态势分析平台

Studies of CO₂‐brine two‐phase flow are predominantly carried out on core samples or reservoir‐scale domains. In this work we investigate intermediate‐scale flow considering a cubic rock with 1 m³ volume incorporating sub‐core (mm) scale heterogeneity. First, a coreflooding experiment is analysed to estimate sub‐core permeability spatial distribution and the results are used as input into the meter‐scale model without any upscaling required. High resolution numerical simulations are conducted to model CO₂ injection into a brine saturated rock. We find significant differences between the meter‐scale rock simulation and core experiment saturation distributions resulting from highly influential boundary effects on the core scale and pronounced gravity impact on the meter scale. A detailed analysis of flow and brine trapping in rock simulations is presented considering different flow models and permeability structures. It is shown that gravity and capillary heterogeneity have substantial impact on the saturation in the deeper regions, which exhibit sufficiently low capillary pressure, and these regions also show increased trapping of brine. Two trapping mechanisms are discussed: Type I which is a result of entry pressure considerations and Type II, which occurs due to lack of CO₂ connectivity. The two types of trapping are found to be correlated to the permeability structure. A formula is presented relating between trapping and permeability statistical parameters, i.e., variance of log permeability and correlation length scale, as well as to the Bond number characterizing the ratio between gravity and capillary effects.