Abstract:

A CO₂ flooding pilot test was carried out on the low permeability fractured reservoirs in Huang-3 block. The research results indicated that there were obvious oil-increasing effects in the overall area, but the gas channeling phenomenon was serious in some wells, resulting in a poor effect of CO₂ flooding. In order to improve the CO₂ flooding efficiency of low permeability fractured reservoirs, the dominant flow channels were identified by tracer monitoring combined with production dynamic analysis and numerical simulation of production history fitting. On this basis, a numerical simulation model of the well group considering the dominant channels was obtained. The effects of the dominant channels on the CO₂ displacement were studied by the numerical simulation technology of the component reservoirs, and four measures to improve the oil displacement efficiency were simulated. The results showed that the dominant channels reduced the CO₂ flooding oil recovery by 7 %. The best effect was obtained by blocking the dominant channels with high-intensity plugging measures, and the RF had increased by 1.8 %. The second best effect was when the dominant channels wells were shut down in the early stage of the gas channeling. Then followed when the water injection maintained the formation pressure. Shut in of the well was relatively poor when the GOR of production well reached 2 000 m ³/m ³, and the RF only increased by 0.11 %. The research results have guiding significance for the design of gas injection drive scheme for low permeability fractured reservoirs.

Key words: low permeability reservoir, dominant channel, CO₂ flooding, improve sweep efficiency