A Multidisciplinary Framework for CO₂-EOR Evaluation: Integrating Geological Screening, Compositional Reservoir Simulation, WAG Performance Analysis and Project Economics

This paper presents a comprehensive evaluation of the possible implementation of a CO2-enhanced oil recovery (CO2-EOR) strategy within a geologically heterogeneous reservoir, which was discovered in 1996 and initiated production in 2001. The field's geological framework comprises six distinct limestone layers, with data collection spanning seven drilled wells. The project reassesses the geological and simulation models of the field, implements a CO2-EOR screening process utilizing extensive methodologies, develops a detailed field-scale compositional reservoir flow model, and executes a history-matching exercise to refine the model based on actual production data. In addition, EOR development strategies, including waterflooding, continuous CO₂ injection, and water alternating gas (WAG) injection, are presented. In each scheme, multiple cases are run to determine the best operating conditions for field performance optimization. The reservoir simulation model was developed utilizing an integrated dataset comprising geophysical, geological, and engineering information, including three-dimensional surface seismic surveys, well log data, and fluid property analyses. A representative fluid sample extracted from the reservoir was subjected to detailed analysis and employed in the calibration of the equation of state to ensure accurate characterization of the reservoir fluids. The history-matched model was then used in the forecasting process under two main development scenarios, namely, the 3 injectors/3 producers’ custom pattern and the 12 injectors/6 producers’ five-spot inverted pattern. These were further categorized into three main divisions, including waterflooding, continuous CO₂ injection, and WAG. Based on the specific reservoir conditions, the operating parameters of the continuous CO₂ and WAG injections with 1:1 and 1:2 cycles were modified to achieve the highest oil recovery. Furthermore, the five-spot inverted infill drilling method produced more oil than the custom 3/3 method, and our economics show that the five-spot inverted infill drilling is more profitable but cost-intensive as compared to the custom method.