Numerical Simulation Research On Non-darcy Flow Of CO₂ Flooding In Yushulin Oilfield

?There are rich resources of low permeability oilfields in China, whose recovery can only reach 20% commonly limited by the current technical conditions. In order to improve oil recovery and production of the low permeability oilfield, new displacement agents and methods should be urgently investigated. Domestic and foreign research results indicate that CO₂ flooding can greatly improve oil recovery, and has no pollution favorable to environment protection, so using CO₂ flooding to develop the low permeability oilfield has wide prospect.In order to accurately predict the variations in dynamic indexes of different CO₂ injection schemes and determine the optimal scheme, besides indoor physical simulation, numerical simulation research should be conducted before carrying on the production test and the formal application. But the existing commercial CO₂ flooding numerical simulation software was developed based on the Darcy flow without considering the influence of actuating pressure gradient, which could not fully reflect the whole CO₂ displacement process of low permeability reservoirs, and therefore it is necessary to establish a CO₂ flooding numerical simulation model considering non-Darcy flow pattern.In this paper, through the studies on CO₂ flooding mechanisms and the non-Darcy flow pattern of this paper low permeability reservoirs, considering the actual situation of Yushulin oilfield, based on the existing component model, a three-dimensional three-phase multi-composition percolation mathematical model suitable for CO₂ flooding of the low permeability reservoirs has been established, which considered the actuating pressure gradient of oil, gas and water. After that, numerical solution was brought out by finite-difference method and IMPES method, and a set of CO₂ flooding numerical simulation software suitable for low permeability reservoirs was then developed. According to the geological characteristic, well pattern and development status of Shu101 block in Yushulin oilfield, facies-controlled geological model was established by using PETREL geological modeling software. At last, based on producing history matching, the CO₂ injection schemes were numerically simulated by the developed numerical simulation software, the CO₂ injection parameters were optimized and then the optimal development scheme was determined.The established model and developed software could simulate CO₂ displacement process in Yushulin oilfield particularly and was suitable for designing the development scheme of Yushulin oilfield, which has important guiding significance for other same type oilfields to improve oil recovery by CO₂ flooding.