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Water Alternative Gas Process Optimizing for CO2-EOR and Carbon Storage


Carbon capture, utilization and geological storage (CCUS) is a promising way to reduce the emissions of the anthropogenic CO2 into the atmosphere. Sequestering the CO2 into depleted hydrocarbon reservoirs is the most achievable approach under current economic constraints, which not only increases the recovery of existing oil reserves but also bridges the gap between regional-scale CCUG. The Upper Devonian fluvial sandstone reservoirs in Jacksonburg-Stringtown oil field in West Virginia is an ideal candidate for CO2 sequestration coupled with EOR, which have produced over 22 million barrels of oil since 1895. This work illustrates an example of CCUS, in which CO2 is simultaneously sequestered and oil recovery enhanced in a depleted oil reservoir by water alternating gas (WAG) method. Three mechanisms for CO2 storage including structural/stratigraphic trapping, dissolution trapping, and residual trapping are considered. This model is based on a highly detailed geological model constructed based on existing legacy geological data from the field. A composition model of 0.4 PVI of water injected before WAG process is considered as a benchmark for this study. The results of numerical simulation show that over 26 years of WAG injection, oil recovery increased from 0.16\% to 1.9\% due to various injection strategies. WAG injection rate, injection time ratio and cycle period play important roles in the storage CO2. As a conclusion, this research constructs and validates a basic workflow for CO2 storage and CO2-EOR that can be applied to other super-mature oil fields, which have abundant conventional legacy data and limited high-quality data.