Eastern Section Meeting

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Development of Dimensionless Performance Curves to Estimate CO2 EOR of Illinois Basin Oil Reservoirs


Dimensionless performance curves (DPCs) derived from geologic and reservoir models have been used to project carbon dioxide (CO2) enhanced oil recovery (EOR) using readily available — but general — data. Time dependent fluid production and injection data calculated from DPCs are needed to estimate oil recovery and make cursory economic analysis when screening specific oil fields for CO2 EOR potential. The Kinder-Morgan dimensionless curve and CO2 Prophet stream tube model are examples of popular CO2 EOR screening tools used.

The purpose of this study is to develop general CO2 EOR DPCs based on three geologic models of each one of the three most prolific Illinois Basin (ILB) geologic formations, each representing various degrees of reservoir heterogeneity and compartmentalization. The prolific ILB formations include the Aux Vases, Cypress, and Ste. Genevieve formations.

The scenario characteristics represented by these DPCs are: miscibility type, injection scheme, degree of heterogeneity, and 5-spot pattern size (20-, 40-, and 80-acre). Miscibility type was limited to immiscible and miscible; injection scheme included continuous CO2 injection and two water-alternating gas (WAG) injection options (20% and 40% HCPV slug of CO2 followed by 0.5:1 WAG ratio) for different pattern sizes. Prior to simulating the CO2 EOR period, each model was run through 25 years of primary production followed by 40 years of water injection to ensure that each recovery process was near its termination. The DPCs were calculated from the cumulative production and injection from simulation output by normalizing each to the hydrocarbon pore volume of the respective model.

For screening studies, dimensioned projections of oil, CO2, and water production, and CO2 and water injection are made from DPCs using the original oil in place of an area of interest. A database tool is presented that shows the use of the DPCs. The oil, CO2, and water production, and CO2 and water injection estimates from the DPCs were compared to those of a calibrated reservoir simulation of Iola Consolidated to validate the general CO2 EOR DPCs.