Three-dimensional physical simulation and characterization of CO₂ flooding and storage patterns in ultra-low permeability reservoirs

Objective CO₂ flooding and storage are integral components of Carbon Capture, Utilization and Storage (CCUS). While pilot tests in Liaohe Oilfield’s deep, ultra-low permeability Reservoir Block S229 have shown initial success, gas channeling in several production wells remains a challenge. Currently, the CO₂ miscible flooding sweep patterns and corresponding oil well response characteristics are poorly understood. Consequently, targeted research into the production performance and dynamic laws of CO₂ flooding and storage in ultra-low permeability reservoirs is essential.

Methods A three-dimensional physical simulation method was employed for this research. Based on the typical well pattern of the Liaohe Oilfield S229 test area, a three-dimensional physical model was designed and established, and a corresponding experimental platform was constructed. Using optimized injection rates, a gas-soluble foaming agent for channeling control, and specific injection-production regulation modes (continuous gas injection and asynchronous injection-production), three groups of three-dimensional plate physical model experiments were designed under varying channeling control measures. Cumulative oil production, cumulative gas-oil ratio, storage efficiency, and storage volume were comprehensively compared across the different measures.

Results Both the cumulative oil production and CO₂ storage capacity followed the same descending order across the three groups of experiments: asynchronous injection-production followed by foam blocking (cumulative oil production: 2.37×10⁻⁴ t; CO₂ storage capacity: 0.728 g/mL), continuous gas injection followed by foam blocking (cumulative oil production: 2.20×10⁻⁴ t; CO₂ storage capacity: 0.703 g/mL), and continuous gas injection followed by asynchronous injection-production (cumulative oil production: 2.01×10⁻⁴ t; CO₂ storage capacity: 0.684 g/mL). Continuous gas injection yielded low cumulative oil production, as rapid gas breakthrough triggered a sharp increase in the cumulative gas-oil ratio. The formation of dominant channeling pathways led to ineffective CO₂ circulation, severely compromising the productivity of adjacent wells. The development mode of asynchronous injection-production followed by foam blocking could effectively control and block gas channeling, featuring high cumulative oil production and large CO₂ storage capacity.

Conclusion Three-dimensional physical simulation of CO₂ flooding and storage in ultra-low permeability reservoirs demonstrates that asynchronous injection-production effectively mitigates gas channeling, while gas-soluble foam provides efficient blocking. Consequently, asynchronous injection-production followed by foam blocking is identified as the most effective and viable development strategy. A comprehensive regulation technology for channeling control has been developed to address gas channeling during CO₂ flooding and storage. Its primary function is the precise inhibition of ineffective CO₂ cross-flow through high-permeability channels, ultimately enhancing both oil displacement efficiency and CO₂ storage capacity.