Abstract:

According to the existing weakness of oil displacement by CO₂ with vertical well pattern in low-permeability reservoir, the article first takes some low-permeability blocks in Daqing as an example to build a geologic model of oil displacement by CO₂ with inverted seven-spot horizontal well pattern. Based on the phase behavior matching of physical parameters, comparative study is demonstrated between the development effects of inverted seven-spot horizontal well pattern and five-spot vertical well pattern, and the other parameters of inverted seven-spot horizontal well pattern are optimized, meanwhile, the influential factors of the reservoir heterogeneity (e.g. permeability, heterogeneity of the reservoir, fracture development state and so on) are also analyzed. Results show that: the development effects of the horizontal wells pattern are better than that of the vertical wells pattern under the same conditions; In the horizontal wells pattern, the recovery varies with the vertical distance ratio of production to injection, and the recovery is the highest when the ratio is 1.4; Horizontal wells pattern with CO₂ injecting is more suitable for low permeability positive rhythm reservoir; In the case of the reservoirs with fracture development, the more the number of fractures is in the reservoir, the more obvious the phenomenon of non-uniform advancing is, the lower the ultimate recovery is.

Key words: low permeability reservoir, horizontal well, CO₂ flooding, heterogeneous, numerical simulation