CO2 Injection is one of the EOR methods that holds potential to be widely implemented. However, the underlying issues in implementing CO2 injection include the availability of CO2 sources as well as the steep capital cost associated with the surface facilities required to deliver and process the CO2. In such case, the cyclic injection, so-called Huff & Puff CO2 injection is seemingly more feasible. In this study, we propose an alternative predictive model to determine the performance of CO2 cyclic injection. This model can be utilized as a preliminary screening tool and to understand the feasibility of the operation in a quick manner. In addition, the uncertainties associated with the reservoir conditions can also be considered within the model.
Most of the efforts to develop predictive model for CO2 cyclic injection have been concentrated around empirical approach, and hence, only limited parameters are considered. In this study, we establish experimental design through reservoir simulation and perform machine learning to construct the predictive model. Therefore, most important factors driving the performance of the well underwent CO2 cyclic injection including reservoir rock and fluid properties, interaction between rocks and fluids, drainage geometry, and operating condition are incorporated. Compared to the simulation results, the proposed predictive model shows an acceptable accuracy with R-squared of above 0.95.
The result of this study can be used to help find suitable well and reservoir to be injected with cyclic CO2 injection, as preliminary analysis on the individual well performance can be conducted before performing full field simulation. The model can also be utilized to determine the optimum amount of CO2 needed, as well as the length of injection and soaking time before the well is put into production.