Chemical EOR projects were very active during 1980's, however, during 90's the interest in chemical EOR has fallen due to the low oil prices and also technical challenges that the methods poses. While surfactant flooding has difficult design considerations of chemicals, large capital requirements and is very sensitive to local reservoir heterogeneities, alkali can react strongly with minerals in the connate water and reservoir rocks may adversely impact the process. This complex process is yet to be understood. If the field is offshore, chemical EOR becomes even more challenging due to sophisticated logistics, incremental costs, highly deviated wells, larger well spacing and limited well slots on the platform. However, recently there has been a renewed interest in chemical flooding mainly due to valuable insights gained through chemical floods done in the past and better technical understanding of the processes and favorable economic conditions.
For robust production forecasts, various uncertainties due to complex chemical processes should be quantified thoroughly. Some of the important uncertainties for full field production forecasts are chemical adsorption on rock surface, interfacial tension (IFT) and residual oil saturation reduction by chemical. Proper coreflood experiments are critical to reduce these uncertainties. Careful matching of coreflood experiments in numerical simulations is also important which provides key inputs for full field forecast. Another important element in the successful commercial application for chemical EOR process is a well-designed pilot. After the completion of pilot, the results should be carefully matched in the simulation model. Once satisfactory match is obtained, the key step would be to upscale the results to the full field level.
Discussed in this paper are the impact of some of these uncertainties and the method used to reduce them. In this paper the workflow and key tasks in dealing with the simulation of chemical EOR process elements like residual oil saturation, IFT reduction and adsorption parameters are discussed. The results show that the incremental oil is very sensitive to the various simulation inputs.