Evaluation of CO2-EOR and Storage Potential in Mature Oil Reservoirs

Abstract

Abstract The selection of candidate reservoirs for future CO2 enhanced oil recovery (EOR) and storage projects greatly relies on methodical screening and detailed site specific evaluations. Once suitable reservoirs are identified in an initial screening for further evaluation, CO2-Prophet screening model could be used for a better understanding of proposed EOR project performance and site specific incidental CO2 storage prior to launching detailed and time consuming reservoir simulation studies. This paper reports on the use of publicly available geological and reservoir data and CO2-Prophet model for performing such analysis for two deep mature light oil reservoirs situated in the Kern County, California. In initial screening, these reservoirs have already been found amenable for CO2-EOR and storage. Often, calibration of CO2-prophet model is either overlooked or just performed for achieving a material balance for oil and water phases. In addition to commonly used calibration step that involves a match for field water cut versus cumulative oil recovery history since waterflooding to achieve material balance for oil and water phases, we propose the use of an average gas-oil ratio match plot for obtaining a reasonable material balance for produced gas phase. A reservoir specific calibration of CO2-Prophet model for obtaining material balance for all three phases is aimed to increase confidence in future performance prediction results. We describe calibration procedure of the CO2-Prophet model in detail and use appropriately calibrated models for predicting CO2-EOR performance and incidental CO2 storage potentials in the reservoirs which have been already found ameable for CO2-EOR and storage in initial screening. Beyond EOR based volumetric predications or other simple estimations made in initial screening of candidate reservoirs, appropriately calibrated CO2-Prophet model can provide more robust and reservoir specific estimates of CO2-EOR and incidental CO2 storage potential for a candidate reservoir. Such approach can be used for making initial business decisions such as selection of propective pilot sites or field acquisition while avoiding the need of detailed reservoir simulation studies. The results presented in the study clearly demonstrate that deep and mature light oil reservoirs of Kern County, California have potential for large scale (injection of more than 1 million metric tons of CO2 per year) CO2-EOR and storage projects.