Influence of Heterogeneous Reservoir on Carbon Sequestration and Carbon Displacement

Abstract Carbon Capture, Utilization and Sequestration (CCUS) is a method of burying CO 2 captured in various ways into the reservoir and extracting the remaining oil from the reservoir. It is one of the important methods to reduce carbon emissions and achieve carbon neutrality in the next few decades, and it is also considered to be the most economical and effective method to slow down the greenhouse effect. It is very important to study the influence of reservoir heterogeneity on CO 2 storage and oil recovery in order to make CCUS scheme store more CO 2 and recover more remaining oil. Firstly, the numerical simulation model of reservoir is established in this paper. Its injection-production mode is gas injection in vertical wells at the top of the reservoir at a fixed gas injection rate, and oil production in horizontal wells at the bottom of the reservoir at a fixed pressure. Secondly, the distribution of reservoir porosity and permeability is designed, and four reservoir models are established: homogeneous reservoir, heterogeneous reservoir, positive rhythm heterogeneous reservoir and reverse rhythm heterogeneous reservoir. Finally, the effects of four reservoir models on CO 2 storage and oil recovery are studied, and the migration law of CO 2 is comprehensively analyzed according to the characteristics of reservoir pressure distribution. The reverse rhythm reservoir has the best CO 2 storage effect, and the positive rhythm reservoir has the highest oil recovery. That is, when burying is the main method, the reverse rhythm heterogeneous reservoir is preferred; When oil displacement is the main method, positive rhythm reservoir is preferred. Among the four homogeneous or heterogeneous reservoirs, the migration law of CO 2 in reservoirs is quite different, mainly due to the influence of reservoir heterogeneity. CO 2 preferentially migrates from the dominant channels in the reservoir, but regardless of the reservoir type, the molar fraction of CO 2 at the top of the reservoir is the highest. In addition, the CO 2 invasion of four kinds of reservoirs in different stages of caprock is analyzed and its safety is analyzed. This study provides an effective reference for the establishment of numerical simulation models of different types of heterogeneous reservoirs, the migration characteristics of carbon dioxide in reservoirs and the effective operation and evaluation of CCUS scheme.