Abstract:The determination of the hydrocarbon gas-crude oil minimum miscibility pressure (MMP) and the evaluation of its influencing factors in low permeability reservoirs are generally based on numerical simulation method, which is lack of indoor physical simulation experiment of hydrocarbon gas drive. The slim tube method is a fast and accurate experimental method to determine MMP and the recovery degree of reservoir. In this paper, the miscible displacement of hydrocarbon gas injection in the deep clastic rock reservoir of Tarim is taken as an example, by using 15 m, 30 m and 45 m slim tubes as experimental variables, the effects of the length of the slim tube on the MMP and the recovery degree of the reservoir are explored and compared. The experimental results show that with the increase of the length of the slim tube, the MMP decreased from 60.4 MPa to 56.3 MPa, and the final recovery increased from 91.51% to 92.88%, thus, the longer the injection production well spacing is, the higher the miscibility of injected gas and crude oil is. Finally, based on genetic optimization algorithm (GA), an improved prediction model of MMP considering the length of slim tube is proposed. The model selects reservoir temperature, middle component mole fraction of crude oil, volatile component mole fraction of crude oil, C7+ molecular weight of crude oil and critical temperature of injected gas as independent variables. The results show that for the three groups of experimental data, the improved MMP model has high accuracy, and the AARD are 0.08%, 0.24% and 0.34%, respectively. This study provides a reference method for the analysis of the influence factors of MMP and the calculation of the MMP.