Abstract:

Addressing issues such as poor water injection capacity, substandard water quality and wax deposition of high pour point crude oil in low permeability reservoirs of Shuanghe Oilfield in Henan, an independently designed water-CO₂ reservoir injection capability evaluation device was utilized to conduct flowability experiments and CO₂ displacement tests. Combined with core scanning electron microscopy and other testing methods, the main mechanism of poor water injection capacity of Shuanghe low permeability reservoirs was clarified, and the main mechanism of CO₂ improving the injection capacity of low permeability reservoirs was explored. The results show that the deposition of suspended particles in the produced water and wax crystals in the oil can lead to pore blockage, thereby reducing the water injection capacity of the reservoir. CO₂ has a significant dissolving effect on inorganic suspended particles in produced water and on alkaline minerals and carbonate minerals in rocks, which is the main mechanism for significantly enhancing the reservoir's water injection capacity. CO₂ can dissolve paraffin deposits on the rock surface, effectively improving the reservoir's water injection capability. At the same time, the effect of CO₂ flooding is obvious, the recovery rate is increased by 13.01% ~ 21.51%, and the subsequent water flooding is further increased by 5.40% ~ 6.04%. This study shows that CO₂ injection can significantly improve the injection capacity of low permeability reservoirs in Shuanghe Oilfield, and provides theoretical support for the field application of CO₂ injection and oil displacement technology.

Key words: low permeability reservoir, high pour point crude oil, wax deposition, water quality of injection, CO₂ injection technology