细管长度对烃类气-原油最小混相压力的影响及其改进预测模型

低渗透油藏烃类气-原油最小混相压力（MMP）确定及影响因素评价一般多采用数值模拟方法，缺乏烃类气驱室内物理模拟实验。细管法是一种快速、准确确定最小混相压力及油藏采出程度的实验方法，本文以塔里木深层碎屑岩油藏注烃类气混相驱替为例，通过采用15 m、30 m、45 m不同长度的细管作为实验变量，探究细管长度对最小混相压力以及油藏采出程度的影响并进行对比分析，实验结果表明：随着细管长度的增加，最小混相压力由60.4 MPa降低至56.3 MPa，油藏最终采出程度由91.51%提高至92.88%，即注采井距越长，注入气与原油混相相率越高。最后，基于遗传优化算法（GA），提出了一种考虑细管长度的MMP预测改进模型，该模型选取油藏温度、原油中间组分摩尔分数、原油挥发组分摩尔分数、原油C7+分子量、注入气临界温度为自变量。结果表明：针对本次3组实验数据，改进的MMP模型精度较高，预测误差分别为0.08%、0.24%、0.34%，具有良好的预测能力。该研究为细管参数对烃类气驱最小混相压力影响因素分析以及最小混相压力计算，提供了一种参考方法。

Study on the influence factors of hydrocarbon gas-crude oil minimum miscibility pressure based on different length of slim tube and the improved prediction model of minimum miscibility pressure

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.