Experimental study on dual benefits of improvement of CO2 enhanced oil recovery and its storage capacity for depleted carbonate oil reservoirs

Abstract

The utilization of supercritical CO2 in oil and gas reservoir engineering, particularly for enhanced oil recovery, has garnered considerable attention due to its potential to boost hydrocarbon production while reducing CO2 emissions. This study investigates the improvements achievable in CO2-enhanced oil recovery and subsequent carbon storage capacity within heterogeneous carbonate reservoirs through supercritical CO2 miscible injection after seawater flooding. Utilizing a dual-core flooding setup with carbonate core samples exhibiting significant permeability contrast, experiments were conducted under reservoir conditions using live oil, seawater, and supercritical CO2 miscible injection. To enhance CO2-enhanced oil recovery and storage within low-permeability zones, a thermal foam gel system was introduced into a highly permeable core after initial supercritical CO2 miscible injection, effectively sealing off high-permeability zones and improving displacement and storage capacity. Results demonstrate that reservoir heterogeneity notably influences supercritical CO2-enhanced oil recovery efficiency and sequestration in low permeable regions, with bypass flow in high-permeable regions hindering displacement efficiency and CO2 storage capacity. However, plugging high-permeability zones using a thermal foam gel system after the initial supercritical CO2 miscible injection, about 15% extra oil recovery of the pore volume from low-permeability zones was recovered during the second supercritical CO2 miscible injection, and the equivalent pore space provides a site for storing CO2 also. Additionally, dynamic characteristic parameters such as injectivity, permeability loss, and endpoint relative permeability related to supercritical CO2 storage are discussed in this study. The study’s outcomes contribute to advancing the understanding of CO2-enhanced oil recovery and sequestration, facilitating the development of more effective and sustainable reservoir management practices.