An improved correlation to estimate the minimum miscibility pressure of CO2 in crude oils for carbon capture, utilization, and storage projects

Abstract

The utilization of anthropogenic CO2 for enhancing oil recovery while sequestering CO2 in depleted oil and gas fields is increasingly being viewed as an attractive economic proposition for reducing greenhouse gas emissions. Typically, CO2 assisted enhanced oil recovery projects are operated at the minimum miscibility pressure (MMP), beyond which the CO2 and oil phases are completely miscible and the incremental oil recovery from CO2 displacement does not increase dramatically anymore. Thus, the MMP is a critical parameter in screening-level performance assessments of potential CO2 floods. The MMP can be measured from displacement experiments in a laboratory using a slim tube apparatus. Alternatively, it can be estimated from statistical correlations developed using reservoir temperature and detailed crude oil composition and analytical methods such as equation of state based simulations. In this paper, we describe the development and validation of an improved correlation to estimate the MMP of CO2 in crude oil based only on: (a) reservoir temperature, and (b) molecular weight of the C5+ fraction, which can also be estimated from the oil's specific gravity. A power law based predictive model for MMP has been developed through statistical analysis of data from published literature pertaining to crude oil with a wide range of temperatures and molecular weights. The resulting predictions were compared with those obtained from previously established and widely used correlations (e.g., Cronquist, 1978) and found to have a higher degree of accuracy.