Integrated reservoir characterization in Delhi field, Louisiana: a continuous CO₂ injection EOR project

Abstract

In assessing the efficiency of any CO2 enhanced oil recovery projects, it is essential to track the flow path of injected CO2. Time-lapse seismic is an effective tool for monitoring CO2 movement and deciphering flow paths in the reservoir. Reservoir simulation is used by reservoir engineers to determine displacement efficiency and dynamic changes of pressure and saturations in the reservoir, using production-injection data. Reservoir simulation also serves as a prediction tool to evaluate the economics of the CO2 projects. Both time-lapse seismic analysis and reservoir simulation can complement each other to increase the understanding of CO2 flow paths and CO2 effectiveness. This study reports the findings from a comprehensive workflow and methodology for integrated reservoir study of enhanced oil recovery in conventional reservoirs. The major components of the workflow include data collection and validation, geologic modeling, reservoir modeling, history matching assisted by seismic monitoring, model calibration, and economic evaluation. Specifically, the study involves an integrated study of geology, geophysics, and engineering applied to a continuous CO2 injection EOR project in Delhi Field, Louisiana. The CO2-targeted formations are the Tuscaloosa and Paluxy sandstones of the Early Cretaceous time. The production and injection activities in Delhi Field result in changes in fluid saturations and pore pressure. These changes affect properties of the reservoir rock and fluids, which can be detected by time-lapse seismic data. A geologic model was built using well logs, petrophysical measurements and seismic inversion for the Reservoir Characterization Project (RCP) area. Simulation models, including a black oil model and an eleven-component compositional model, were built based on the geologic model. Production history matches were performed for the primary, secondary and tertiary production phases of the field. Then, simulation results were compared against seismic monitor interpretations to calibrate the reservoir model. The results show that the simulated flow paths of the injected CO2 agree with the time-lapse seismic interpretations. The agreement validates the effectiveness of integrating geologic modeling, reservoir modeling, and time-lapse seismic analysis in assisting field operations to maximize oil recovery efficiency. Furthermore, this agreement can close the loop of geomodel-4D-seismic-reservoir simulation in a dynamic reservoir characterization process, and can minimize the non-uniqueness in the reservoir model.