Miscible CO2 flooding for EOR in the presence of natural gas components in displacing and displaced fluids

Abstract

Carbon dioxide (CO2) flooding is a complicated process as it involves phase behavior. The objective of this work was to understand the mass transfer mechanisms during flooding with CO2 and CO2/C1/C3 (CO2/HC) based on experimental and simulated composition changes. Three model oil compositions were used (n-C10, n-C10/C1, and n-C10/C1/C3). For a comparison, crude oil from a North Sea field was included. The second part of the investigation was to compare the effect of the combined light components (C1/C3) with CO2 as a displacing fluid on enhanced oil recovery (EOR). Equation of State EOS SRK–Peneloux was used for the simulations to predict composition changes. The highest recovery was obtained from model oil (n-C10) displaced with CO2 compared to model oil containing light components with the highest recovery recorded from model oil/C1 (live oil A) compared to model oil/C1/C3 at all of the tested temperatures. The presence of light components (C1/C3) in the injected CO2 at miscible conditions increased the oil recovery for crude oil compared to flooding only with CO2. Transverse dispersion of CO2 helps in eliminating/reducing the effect of viscous instabilities by shortening fingering travel/widening the fingers. The collected samples contained water, although the flooding was done on dry sandstone cores. Possible mechanisms are discussed in a later section.