Workflow For Multi-Scale Data Integration in Onshore CO2 EOR Project

Abstract

Abstract The planning stage of CO2 EOR evaluation of remaining oil volume including immovable oil is one of the most important work because of its significant impact on field performance and project economics. However, planning becomes very challenging when the concerned field is a legacy field where historical data are insufficient unless reliable data were later supplemented. This paper describes how to evaluate CO2 EOR project for a legacy field with insufficient historical data. To estimate the remaining movable/immovable oil volume in the field, the following multi-scale data were reviewed. Varying results were captured by review as shown below; SCAL (Special Core AnaLysis) ReviewSWCTT (Single Well Chemical Tracer Test)Material Balance CalculationCO2 Pilot Test Residual oil saturation measured in-situ by SWCTT in wellbore scale was cross-checked with past SCAL results in core scale. Remaining oil saturation was estimated by utilizing a full-field reservoir model with material balance check. CO2 Pilot Test confirmed oil saturation decrease after CO2 injection in well-logging scale. As a result, uncertainties were identified in the residual and remaining oil saturation. A Type Curve that represents production performance of a certain area/zone was established based on numerical pattern model incorporating reservoir characteristics including the above oil saturation profiles. By superposing the Type Curves as per the pattern development schedule, total field production profile was predicted. Incorporating the above uncertainties of residual/remaining oil saturations, several Type Curves were prepared. Additionally, a reservoir simulation study indicates that the WAG scheme, for instances WAG ratio and slug size, would impact on an incremental oil recovery. Accordingly, an optimization study of the WAG scheme is currently in progress and this will impact on oil recovery. In summary, oil recovery estimate for this particular legacy oil field required detailed data reviews mainly due to uncertainties of the volume of remaining oil. CO2 Pilot Test results provided direct evaluation of EOR effectiveness and supported oil saturation change with CO2 injection. Residual/remaining oil saturation need to be revisited with the additional information acquired during project execution stage to improve the accuracy of estimated incremental oil recovery.