Injection And Production Parameters Optimization Of Air Foam Flooding In Low Permeability Oil Reservoirs

Air foam flooding combines the advantages of air flooding and surfactant flooding which can selectively plug high permeable channel and greatly reduce gas relative permeability.Thus,air foam flooding is especially effective for heterogeneous oil reservoirs.Ganguyi oilfield is famous for its low permeability and low porosity where air foam has been injected to enhance oil recovery.Obvious effect of oil increment and water cut declination is achieved in field trials.However,some problems of air foam flooding become exposed such as oil rate drop quickly in responding period of air foam flooding.Furthermore,most injection and production parameters are generated from laboratory experimental results which have insufficient applicability in field trials.The unique generation mechanism and flow characteristics of air foam are studied in this paper.A prediction model of foam resistance factor is built which can be used to quantify the ability of sealing horizontal fractures.A typical anisotropic oil reservoir with low permeability is built,and effects of ten injection-production parameters on air foam flooding are numerically studied.Sensitivity analysis shows that injection scheme and injection timing are extremely sensitive parameters,gas liquid ratio,main slug size and alternating cycle are sensitive parameters,injection-production rate and producing layers are less sensitive parameters,injection pressure,surfactant concentration and pre-slug size are non-sensitive parameters.Then the optimization principle of injection-production parameters is proposed.According to the dynamic and static data of research area,a numerical model including four well groups is built.Eight schemes of air foam flooding taking account of gas liquid ratio,main slug size and alternating cycle is designed and put into simulation.The principal component projection method is applied to evaluate different schemes with same production index and economic index.Calculation results show that the optimal injection-production parameters specific to research area are SAG injection,gas liquid ratio of 3:1,surfactant concentration of 0.5%,pre slug of 0.5%×0.02 PV,main slug of 0.5%×0.2PV,alternating cycle of 45 days and balance of injection-production rate.