Optimization of CO2 Foam EOR Processes: A Case Study from Lab-scale Model Fit to Field-Scale Development Planning

Abstract

Lisama field, located in the eastern part of the Middle Magdalena Valley Basin in Colombia, was discovered in 1935 and estimated to hold approximately 0.25 billion STB of oil in place. Mainly consisting of two primary sandstone formations, the field moves gradually from the primary to the secondary and tertiary recovery methods. Injection of water and gas is considered as a possible solution in the next phase. This study performs a simulation study by using CMG STARS for a sector with an inverted 5-spot pattern to evaluate a wide range of development strategies for gas-water co-injection and foam treatments. After performing reservoir simulations varying gas and liquid fractions (from 100% CO2 injection to 100% liquid injection) at four different levels of gas mobility reduction (mobility reduction factor (MRF) = 1, 10, 100, and 1000 for no foam, low-strength, intermediate-strength and high-strength foam, respectively), this simulation study reveals the following findings. First, compared to gas-water injection with no foams, injection of foams can improve cumulative oil recovery and sweep efficiency significantly. Such a tendency is observed consistently at three high, intermediate, and low total injection rates tested. Second, the use of sweep-efficiency contours as a function of injection foam quality (fg, or 1-fw) and MRF, at given total injection rate, provides a useful insight to understand graphically how effective an injection strategy can be. If an MRF-vs.-fg coreflood experimental data is imposed on the contour plot, the results can assist important business and technical decisions about optimum field development planning. Third, if certain constraints exist in the field, they can be mapped out on the sweep-efficiency contour map to predict how the optimum injection strategy should change. In addition, the simulation results show that this field of interest has gravity-dominant environments such that the injection at wetter condition, with or without foams, can be viewed as a better injection strategy in general to obtain higher oil recovery. The business decision, however, can have the injection condition skewed depending on the costs of supercritical CO2 and surfactant solutions.