생산유전의 CO2 공법 적용성 평가를 위한 평가차트 개발 및 응용

In this study, we present the evaluation chart for assessing the applicability of CO2 flooding method to oil reservoirs. The evaluation chart consists of four categories as source availability, miscibility, applicability and injecting method of miscible flooding. The applicability of reservoir and oil in the chart has basic items of the properties such as oil gravity, viscosity, oil saturation, reservoir temperature and permeability, and these are quantitatively graded. Meanwhile, for additional items of CO2 purity, reservoir thickness and formation dip, they are graded as “highmediumlow”. In the case of evaluating the injection method of either continuous injection or WAG (CO2), the qualitative decision will be made according to formation dip, vertical permeability, reservoir thickness, etc. The recommended score in the chart was assigned by utilizing 51 oil producing fields which CO2 flooding is successfully being applied. The evaluation chart developed in this work has been applied to the Captain oil producing field located in Scotland as well as to the Onado oil field of Venezuela, which Korean oil companies have participated in. For the Captain field, the reservoir quality in terms of permeability and porosity is considered to be very excellent to flow the oil. The oil in captain field contains heavier component of C21+ as 54%. Therefore, this heavy oil could be immiscibly displaced, hence the evaluating result with the basis of immiscible criteria shows that CO2 immiscible flooding in this field could be properly applied. In the case of Onado oil producing field, since the estimated minimum miscibility pressure is lower than the reservoir pressure, it was assessed that the Onado field would be efficiently conducted for CO2 miscible flooding.