Flue gas injection for EOR and sequestration: Case study

The combination of carbon dioxide enhanced oil recovery (CO2-EOR) and permanent CO2 storage in mature oil reservoirs has the potential to provide a critical near-term solution for reducing greenhouse gas (GHG) emissions. This solution involves the combined application of carbon capture and storage from power generation and other industrial facilities with CO2-EOR. In order to reduce CO2 capture costs flue gas, which consists mainly of N-2 and CO2, injection has been proposed. The main aim of this research is to investigate flue gas injection in a mature oil field located in Turkey where CO2 EOR had been applied between 2003 and 2012. Injected CO2 was produced from a nearby small natural CO2 reservoir with limited resource. Due to the availability of nearby flue gas source (cement factory) and a pipeline for gas transportation, which was built to transport natural gas from the oil field to cement factory, there is a huge opportunity to decrease project costs. A 3D compositional simulation model was built after a detailed fluid characterization. After history matching 31 years of production, injection, saturation and pressure history, a comparative study was conducted to examine the efficiency of flue gas injection compared to CO2 injection for simultaneous EOR and storage purposes. Storage capacity of the oil field as well as the contribution of raw flue gas injection and CO2 injection to oil recovery were studied. Effect of injected gas type, gas solubility and operating parameters on storage and recovery were investigated. Results showed that pure CO2 injection leads to higher oil recovery and CO2 storage, if injection continued for at least 25 years. Before this threshold injection time, flue gas injection and pure CO2 injection resulted in comparable oil recoveries. It was also concluded that pressurizing the reservoir with raw flue gas injection followed by pure CO2 injection may improve the project economics.