An Investigation of the Robustness of Physical and Numerical Vanishing Interfacial Tension Experimentation in Determining CO2 + Crude Oil Minimum Miscibility Pressure

Dayanand Saini

doi:10.1155/2016/8150752

Abstract

Different experimental and theoretical methods are used for predicting the minimum miscibility pressure (MMP) of complex CO2 + reservoir crude oil systems that are of particular interest to petroleum industry. In this paper, published physical and numerical vanishing interfacial tension (VIT) experimentations are critically examined for identifying best practices to reliably predict the CO2 + crude oil MMP. Some of the reported physical VIT experimentation studies appear to follow a portion of full scale VIT experimentation (i.e., a combination of the pendent drop method and the capillary rise technique). The physical VIT experimentation method in which the IFT measurements are made at varying pressures but with the same initial load of live oil and gas phases in the optical cell seems to be the most robust mechanistic procedure for experimentally studying the pressure dependence of IFT behaviors of complex CO2 + crude oil systems and thus determining the MMP using the VIT technique. The results presented here suggest that a basic parachor expression based on numerical VIT experimentation can reasonably follow the physical VIT experimentation in low IFT region, provided measured input data such as equilibrium phase densities and compositions are used in calculations.

Highlights

Accurate knowledge of minimum miscibility pressure (MMP) is crucial for designing and implementing successful miscible CO2 flooding based enhanced oil recovery (EOR) projects
According to Nagarajan et al [8], near-critical region where interfacial tension (IFT) between injected CO2 and reservoir crude oil approaches zero is of particular interest in EOR applications, since improved efficiency of oil displacement by CO2 occurs when the IFT becomes low
They concluded that the vanishing interfacial tension (VIT) approach to determine the MMP for multicomponent gas-oil displacements should be used with caution given the potential for significant errors in the resulting estimate of the Nobakht et al [19] used the parachor model and linear gradient theory (LGT) model for predicting the equilibrium IFT versus equilibrium pressure data of a crude oilCO2 system

Summary

Introduction

Accurate knowledge of MMP is crucial for designing and implementing successful miscible CO2 flooding based enhanced oil recovery (EOR) projects. They tested the performance of the proposed mechanistic model for two reservoir crude oil-gas systems and claimed to find an excellent match between the experiments and the mechanistic model predictions They used the predicted IFT data for determining MMP using the VIT approach. Orr Jr. and Jessen [34] presented a numerical analysis of VIT experimentation by studying the pressure dependence of IFT behaviors of several CO2 + standard hydrocarbon mixtures and CO2 + crude oil mixtures They concluded that the VIT approach to determine the MMP for multicomponent gas-oil displacements should be used with caution given the potential for significant errors in the resulting estimate of the MMP. They mentioned that other parachor models such as mechanistic parachor model [14] can be used for obtaining VIT trend

Different Versions of Physical VIT Experimentation

Results obtained

Discussion