Three-Dimensional Physical Simulation Characterization of Carbon-Driven Oil Storage Patterns in Ultra-Low-Permeability Reservoirs

【Objective】CO₂ enhanced oil recovery (EOR)-sequestration is a key component of carbon capture, utilization, and storage (CCUS). Pilot tests of carbon-driven oil recovery and sequestration in the deep, ultra-low permeability S229 block of the Liaohe Oilfield have shown initial success. However, gas migration has occurred in some frontline wells, and the patterns of CO₂ miscible drive propagation and well performance characteristics remain unclear. Therefore, urgent research is needed on the production dynamics and patterns of CO₂ enhanced oil recovery and storage in ultra-low permeability reservoirs. 【Methods】This study employs a three-dimensional physical simulation method. Although model construction is challenging, it better reflects actual reservoir conditions, yielding more instructive and valuable experimental results. Using a typical well network from the S229 test area in the Liaoning Oilfield as a template, an artificial three-dimensional physical model was designed and constructed. Based on this model, a three-dimensional physical simulation experimental platform was established. Drawing upon preliminary research that had already optimized injection rates, gas-bubble-type foaming agents suitable for ultra-low permeability reservoirs, and injection-production control methods (continuous gas injection, asynchronous injection-production). Three sets of three-dimensional flat-plate physical model experiments were designed under different sealing methods, ultimately comparing cumulative oil production and recoverable reserves under various sealing approaches. 【Results】Experimental cumulative oil production ranked as follows: Asynchronous injection-production transition to foam sealing (2.37×10^-4 t) > Continuous gas injection transition to foam sealing (2.2×10^-4 t) > Continuous gas injection transition to asynchronous injection-production (2.01×10^-4 t) ; Residual oil content ranking: Asynchronous injection-production followed by foam sealing (0.728 g/ml) > Continuous gas injection followed by foam sealing (0.703 g/ml) > Continuous gas injection followed by asynchronous injection-production (0.684 g/ml). Continuous gas injection yields low cumulative oil production. Upon gas detection in oil wells, the gas-oil ratio rapidly increases. Once flow pathways form, ineffective CO₂ circulation occurs, severely impacting production in other wells. Asynchronous injection-production transitioning to foam-sealed flow control effectively manages flow and seals, achieving high cumulative oil production and substantial reservoir storage. 【Conclusion】 This study established a three-dimensional physical simulation technology for CO₂ flooding and sequestration in ultra-low permeability reservoirs. This technology confirms that asynchronous injection-production effectively controls flow migration, enabling thorough CO₂ diffusion within formations. Earlier implementation further delays gas migration, mitigates inter-well interference, and expands CO₂ coverage. Gas-soluble foam demonstrates high-efficiency flow control by effectively sealing gas migration pathways, promoting CO₂ mobilization in low-permeability zones, significantly enhancing recovery rates and CO₂ storage efficiency. The integrated application of flow control and flow sealing techniques can effectively mitigate inter-well interference, improve development outcomes in target blocks, and increase storage capacity.