Understanding the Phase Behavior of the Steam-Flue Gas Hybrid Process as a Strategy to Improve Oil Recovery and Reduce Carbon Intensity
Authors: Pérez R. , Osma L. , Jaimes J. C. , Sánchez M. R. , Cañas W. , Rueda L. G. , García H. , Manrique E. 
Published: April 2024

In the energy transition era, Colombia has been evaluating different technologies as a commitment to increasing oil recovery and energy efficiency (EE) while at the same time reducing carbon intensity (CI), which represents a big challenge, particularly for heavy oil exploitation. One of the hybrid technologies under evaluation involves the combination of steam and flue gas (FG) to replace volumes of steam with a waste stream of FG from different industrial sources, including gas from steam generators. In that sense, Ecopetrol has been developing an R&D program that includes experimental studies such as a phase behavior evaluation for steam hybrid processes to support numerical studies [Pérez, R. et al., 2020; Pérez, R. et al., 2023].

The methodology for constructing a phase behavior model based on experimental tests that contemplate Carbon dioxide (CO2) solubility in oil and water and its impact on crude oil production and CI is developed and incorporated into a field-sector model for the hybrid steam + FG process. The CO2 and FG (15.24% CO2-84.76% N2) solubility in heavy crude oil at 19.2 SCF/STB were measured to identify its effect on the viscosity, density, and possible compositional changes at two different temperatures (110°F and 302°F) and three pressure conditions (250, 700, and 1,200 psi) to represent the effect of steam injection. In addition, heavy oil fractions were characterized by distillation curves analysis. The use of data from laboratory experiments allowed the development of a numerical fluid model that represents the CO2-Oil interaction through the vapor-liquid K-values obtained by fitting an EOS model, and the liquid-liquid K values that define the interaction CO2-water interaction were calculated using Henry´s model.

Experimental evaluations showed at low temperatures, solubility increases with pressure, reaching gas-oil ratios (GOR) values close to 376.7 SCF/STB and 49.7 SCF/STB at the highest-pressure condition and reducing the viscosity of crude oil by 98% and 56% with CO2 and FG, respectively. However, at high temperatures, solubility decreased by 62% and 52% with less impact on oil viscosity reduction. The compositional profiles of the gas and liquid phases showed no increase in intermediate components, which indicates that the injected gases do not have the capacity to extract light hydrocarbons from the liquid phase. Incorporating the phase behavior into the field-sector model was a key feature for estimating an equivalent CO2 storage of 1,360 tons associated with retaining part of the CO2 injected in the remaining water and crude oil coupled with an incremental oil production of 33,000 barrels.

This phase behavior study contributes to a better understanding of phenomena associated with steam-based hybrid technologies that positively affect the production of hydrocarbons and the reduction of emissions due to CO2 trapping effects associated with solubility in reservoir fluids, contributing to Colombian energy efficiency goals.