A new empirical correlation of minimum miscibility pressure for produced gas reinjection

Congge He,Chenshuo Zhang,Erhui Luo,Lun Zhao,Anzhu Xu,Xing Zeng,Zifei Fan

doi:10.1177/0144598719898572

Abstract

Minimum miscible pressure is a key parameter to screen and design miscible gas injection projects. The aim of this paper is to establish a correlation with only a few input parameters to easily and accurately predict minimum miscible pressure for the reinjection of produced gas with high acidic components. First, the critical parameters of equation of state for each component of the crude oil were obtained through fitting pressure-volume-temperature (PVT) experimental results. Based on the analytically calculated minimum miscible pressures from mixing-cell method, an empirical correlation for predicting minimum miscible pressure in the displacement of crude oil by produced gas was regressed. Finally, the correlation’s accuracy was tested by comparing the minimum miscible pressures predicted from the new proposed correlation to other previous correlations and 20 experimental slim-tube minimum miscible pressures of 12 oil samples. The results indicate that the analytically calculated minimum miscible pressures from the mixing-cell method have a relative error of 0.5% compared to the slim-tube experiment results, which supports its reliability. Furthermore, the new proposed correlation is observed to be superior in terms of the average relative error being only 6.4% for all the 75 analytically calculated minimum miscible pressures and 20 experimental slim-tube minimum miscible pressures, which is lower than the average relative error obtained from other previous correlations.

Highlights

Gas flooding is regarded as a promising enhanced oil recovery method for oil reservoirs by achieving miscibility (Arne et al, 2000; Chen, 1995; Knut and Lars, 2002; Murty and AlKhayat, 1989; Teletzke et al, 2005; Zhang et al, 2013)
CO2 often is used as injection gas because it can achieve miscibility with crude oil at relatively low reservoir pressure, and because there are potential environmental benefits of reducing the greenhouse effect (Hrvoje et al, 2009; Izgec et al, 2005; Li et al, 2006; Song et al, 2019; Sumeer and Xingru, 2014)
In the vaporizing gas drive (VGD) process, generally referred to as lean gas drive, miscibility develops at the flood front

Summary

Introduction

Gas flooding is regarded as a promising enhanced oil recovery method for oil reservoirs by achieving miscibility (Arne et al, 2000; Chen, 1995; Knut and Lars, 2002; Murty and AlKhayat, 1989; Teletzke et al, 2005; Zhang et al, 2013). Benham et al (1960) established some graphical correlations based on calculated critical temperatures and pressures of selected fluids system to predict the approximate conditions for a miscible displacement of reservoir fluid by enriched gas. The critical parameters of the EOS for each component of the crude oil were obtained through fitting pressure-volume-temperature (PVT) experimental results On this basis, an empirical correlation for predicting MMP in the displacement of crude oil by PG was regressed. The maximum (average) relative error for the 20 experimental slim-tube MMPs is 246% (80%) for Abbas correlation, 155% (29%) for Kuo correlation, 161% (50%) for Glaso correlation, 120% (30%) for Eakin correlation, and 32% (14%) for the new proposed correlation. The new proposed correlation is limited to the conditions of MOC7þ ranging from 183 to 302 g/mol, MGC2þ ranging from 30 to 44 g/mol, the molecular percentage of C1 ranging from 10 to 91.7%, the molecular percentage of CO2 ranging from 0 to 45%, the molecular percentage of H2S ranging from 0 to 45%, and the reservoir temperature ranging from 90 to 330F

Conclusions

MGC2þ MOC7þ pc PC2–C5 pm T