CO2 flooding in oil reservoirs to enhance oil recovery is successfully applied in many ongoing projects in the world. The bulk of industry research and field testing of CO2 has been directed towards miscible displacement. This method of using CO2 appears to have the greatest potential for recovery of oil that would not have been recovered using conventional production methods.

The main objectives of this paper are to investigate the most important reservoir and operational parameters in CO2 flooding and to provide guidelines to maximize CO2 injection performance for different levels of reservoir heterogeneity. Several compositional simulation models were generated using actual field data. For each model, reservoir heterogeneity was evaluated using Lorenz and Dykstra Parsons coefficients. The different compositional simulation models were setup to investigate the effects of key parameters such as injection rates, injection patterns, well spacing, injection scheme (Continuous CO2, WAG, and SWAG), WAG cycle length, vertical to horizontal permeability, and horizontal injection wells on the recovery factor and production of CO2 projects.

Those different heterogeneous models were used to simulate different scenarios over a wide range of both reservoir and operational parameters and provided a comprehensive data set to evaluate the CO2 flood effectiveness in a variety of conditions. More than 700 simulation runs were designed using Experimental Design techniques to test those parameters. Several correlations (proxy models) were also developed and blind tested to check their effectiveness in predicting the performance of combination of parameters that were not even tested. As a result of this work, it is possible to use experimental design to test the performance of CO2 injection. It can be performed with acceptable accuracy by performing a limited number of runs; hence, reducing the time, effort, and money.

It was observed that the use of different heterogeneous models resulted in different overall field performance. Our results also showed that implementing WAG and horizontal wells enhance the oil recovery significantly.

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