Study On Feasibility Of Enhanced Oil Recovery By Injecting CO₂ In Volatile Reservoir Of Block X

Formation pressure drops to the bubble point pressure,and a large amount of oil volatilizes,When the volatile oil reservoir is developed,.In order to avoid volatilization of crude,the formation pressure is generally maintained above the bubble point pressure by means of gas injection or water injection.The oil production test results of the low-permeability volatile oil reservoirs in the X block are not good,water injection contradicts is prominently,the moisture content rises rapidly,and the development effect of the water injection deteriorates.Combined with the geological characteristics of the X block and the oil displacement effecttcy of CO2 in the low permeability reservoir,So carrying out the feasibility study of CO2 enhanced oil recovery.In this paper,Study is the feasibility of CO2 enhanced oil recovery in the X block volatile oil reservoir.Firstly,the CO2 suitability evaluation of X block is carried out by fuzzy mathematics,and then the formation fluid phase and formation fluid gas injection are studied through laboratory experiments.After,minimum miscibility pressure of the formation fluid and CO2 was measured by a thin tube experiment.Finally,the optimal development plan for X block was found by numerical simulation technology.Mainly achieved the following conclusions:(1)The method of fuzzy mathematics is used to establish the evaluation criterion of CO2 injection.The comprehensive evaluation shows that the block can enhanced oil recovery by CO2 injection.(2)Through the laboratory experiments,the phase fluid characteristics of the formation fluid are studied.The formation fluid of the X block is light and weak volatile oil,and the elastic energy of the formation is insufficient.The formation pressure is 31.13MPa,the saturation pressure is 11.03MPa,and the ground pressure difference is large.The compatibility test between injected COZ and crude oil gives better effect in pressure holding,viscosity reduction expansion and extraction;the two gas injection and formation fluid can not achieve one-touch miscible,which can realize multi-level contact mixed phase,pressure are 27.85 MPa and 29.2 MPa respectively,the effect of CO2 injection is better than associated anger.(3)The minimum miscibility pressure of CO2 and formation crude oil was tested by thin tube experiment.The minimum miscible pressure of CO2 and crude oil was 23.56 MPa,and the simulated minimum miscibility pressure error was within 2%.(4)Development situation under different development modes by numerical simulation method.Finally,the better development plan is to deploy the adjustment well H1-7x,use H1-3x and H1-7x as injection wells,and adopt the method of early gas injection.The injection speed is maintained at 40t/d,the injection period is 6 months,and the gas-water slug ratio is 2:1.The oil increase in this way is 140195m3,the oil change rate is 0.67t/t,and the sweep coefficient is 0.52.The degree is 24.5%.In summary,it is feasible to increase recovery by CO2 in the volatile oil reservoir of Block X.