Publications

Air injection EOR operation for light oil reservoirs has drawn attentions as a low cost enhanced oil recovery process for more than 10years. Combustion Tube (CT) test which is commonly used for the evaluation of in-situ combustion is also adopted to indicate the degree of oil recovery by air injection in a laboratory scale. In our study, CT tests were conducted at two different initial oil saturation conditions (40 percent and 17 percent, respectively) with the oil samples taken from our candidate domestic oil field. Results indicated high oil recoveries (71 percent and 76 percent, respectively). Many experimental results including PVT, Accelerating Rate Calorimetric (ARC) and CT tests were used to construct a thermodynamic model. Based on the calculation results by the constructed model, we concluded that the predominant mechanism of high oil recovery of CT tests is distillation process which takes place at the high temperature combustion front.Our candidate oil field has a strong aquifer support and the most part of the field have been already watered out. Especially some part of the reservoir area is believed to be reached to irreducible oil saturation (13 percent). Air injection simulation was carried out for the field with a simplified sector model and the constructed thermodynamic model. The simulation results indicated that oil bank can be created by air injection but the injected air overrides the oil bank and causes early oxygen breakthrough in case of low residual oil saturation, resulting in a low incremental oil recovery. On the other hand, in the area where some amount of oil remains, a larger oil bank is created and early oxygen breakthrough is mitigated. For example, more than 10 percent of incremental oil recovery will be expected if residual oil saturation is as high as 30 percent.