Increasing CO2 storage in oil recovery

Oil fields offer a significant potential for storing CO2 and will most likely be the first large scale geological targets for sequestration as the infrastructure, experience and permitting procedures already exist. The problem of co-optimizing oil production and CO2 storage differs significantly from current gas injection practice due to the cost-benefit imbalance resulting from buying CO2 for enhanced oil recovery projects. Consequently, operators aim to minimize the amount of CO2 required to sweep an oil reservoir. For sequestration purposes, where high availability of low cost CO2 is assumed, the design parameters of enhanced oil recovery processes must be re-defined to optimize the amount of CO2 left in the reservoir at the time of abandonment. To redefine properly the design parameters, thorough insight into the mechanisms controlling the pore scale displacement efficiency and the overall sweep efficiency is essential. We demonstrate by calculation examples the different mechanisms controlling the displacement behavior of CO2 sequestration schemes, the interaction between flow and phase equilibrium and how proper design of the injection gas composition and well completion are required to co-optimize oil production and CO2 storage.