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

The Influence of Slim Tube Length on the Minimum Miscibility Pressure of Hydrocarbon Gas-crude Oil and the Improved Prediction Model

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。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,最小混相压力逐渐降低,油藏最终采出程度略有增加,因此,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C 7+相对分子质量、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,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MMP计算,提供了一种参考方法。

The determination of the minimum miscibility pressure(MMP)of hydrocarbon gas-crude oil and the evaluation of its influencing factors in low permeability reservoirs are generally based on numerical simulation method,and lack of indoor physical simulation experiment of hydrocarbon gas drive.Hence,the miscible drive of hydrocarbon injection in deep clastic rock reservoir in Tarim was taken as an example.By using different length of slim tube as experimental variables,the influence of slim tube length on the minimum miscibility pressure and the recovery degree of reservoir was explored and compared.The experimental results show that with the increase of slim tube length,the minimum miscibility pressure decreases gradually,and the final recovery degree of reservoir increases slightly.Thus,the longer the injection production well spacing,the higher miscibility efficiency of injected gas and crude oil is.Finally,based on genetic optimization algorithm(GA),an improved model of MMP prediction considering the length of slim tube was proposed.The model selected reservoir temperature,middle component mole fraction of crude oil,volatile component mole fraction of crude oil,C 7+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 good prediction ability.This study provides a reference method for the analysis of the influence factors of the slim tube parameters on the minimum miscibility pressure of hydrocarbon gas drive and the calculation of MMP.