A method of improving gas injection capacity by CO₂ injection for old oilfield

In view of the low gas injection capacity of old oilfield in CO₂ injection development, the feasibility of using surfactant to improve the injection capacity is verified by the method of long core laboratory test, and the quantitative relationship of the factors affecting the gas injection capacity is determined. The results show that gas injection capacity is greatly improved after the injection of 0.2 PV surfactant slug into the core at a certain stage of water injection, which is 19.31% higher than that of water injection development, and 8.86% higher than that of direct gas injection without surfactant injection, the injection effect is very obvious. The better the physical properties of the reservoir are, the longer the fracture and the smaller the dip angle are, the better the gas injection is. On the contrary, the more water injection in the early stage and the larger the injection production well spacing are, the worse the gas injection is. The water injection volume has the greatest influence on the injection index, the next is the influence of injection production well spacing and fracture, and the least influence of physical properties and formation dip angle. The research results provide a method to improve the injection capacity for the gas injection development of the old oilfield, enrich and develop the gas injection development technology system, and provide an important technical reference for the field implementation of gas injection development.