EOR screening criteria revisited

Abstract

Screening criteria have been proposed for all EOR methods. Data from EOR projects around the world have been examined and the optimum reservoir/oil characteristics for successful projects have been noted. The API gravity ranges of the oils of current EOR methods have been compiled and the results are presented graphically. The proposed screening criteria are based on both field results and oil recovery mechanisms. The current state of the art for all methods is presented briefly, and relationships between them are described. Steamflooding is still the dominant EOR method. All chemical flooding has been declining, but polymers and gels are being used successfully for sweep improvement and water shutoff. Only CO 2 flooding activity has increased continuously. Screening criteria are useful for cursory examination of many candidate reservoirs before expensive reservoir descriptions and economic evaluations are done. For example, we have used our CO 2 screening criteria to estimate the total quantity of CO 2 that might be needed for the oil reservoirs of the world. If only depth and API gravity are considered, it appears that about 80% ofthe world's reservoirs could qualify for some type of CO 2 injection. Since the decisions on future EOR projects are based more on economics than on screening criteria, future oil prices are important. Therefore, we examined the impact of oil prices on EOR activities by comparing the actual EOR oil production to that predicted by earlier NPC reports. Although the lower prices since 1986 have reduced the number of EOR projects, the actual incremental production has been very close to that predicted for $20/bbl in the 1984 NPC report. Incremental oil production from CO 2 flooding continues to increase, and now actually exceeds the predictions made for $20 oil in the NPC report, even though oil prices have been below that level for some time.