Abstract
Carbon dioxide (CO2) injection is the most promising technique to enhance the recovery of high gravity oil with the existing oil price situation. Even though, challenges still exist for thick and heterogeneous reservoirs at very high temperature. The problems faced in such reservoirs are low displacement efficiency and very high injection pressure requirement for a miscible displacement. The effort being done by researchers to overcome the situations is the use of silica nanoparticle as an agent to form CO2-silica nanoparticle foam. Currently, the related literature shows that CO2 miscible displacement is rarely performed at very high temperature and consequently no relevant effort has been made to investigate the stability of CO2-silica nanoparticle foam, while there are many oil reservoirs with temperature of higher than 250 oF. Therefore, related studies on such situations are needed. The present work consists of two stages. First, slimtube and coreflood experiments of CO2 injection are conducted at about 270 oF, respectively, to both determine the Minimum Miscibility Pressure (MMP) of the selected live oil system and the oil recovery. Secondly, CO2-silica nanoparticle foam stability in various brine salinity at such high temperature will be investigated and effectiveness of the selected stable foam will be tested through an oil displacement using native cores.In this paper, the results of both slimtube and coreflood experiments are first presented. A live paraffinic oil with 34 oAPI is used. The standard slimtube apparatus is employed. Stacked core composing of three native core plugs of different permeability ranging from 75 to 503 milidarcies are used to represent rock heterogeneity. At a temperature of 270 oF, MMP of the oil obtained from the slimtube experiment is 2960 psi, about 100 psi higher than that obtained from the coreflood experiment. The slimtube test gives oil recovery 94.2% and the coreflood as expected yields lower recovery, 84% of the initial oil in place. The importance of the tests is two folds that the MMP of the oil system is firmly known while the existing empirical correlations estimate the values ranging from 2718 to 5578 psi and a relatively low coreflood oil recovery suggests further investigation of stability of CO2-silica nanoparticle foam at that temperature in an attempt for enhancing the oil recovery.
Highlights
Proven CO2 injection as an Enhanced Oil Recovery (EOR) technique has been implemented successfully in many oil fields worldwide
The oil recovered at 1.2 pore volume injected (PVI) for estimating Minimum Miscibility Pressure (MMP) is commonly adopted in slimtube tests
The present experimental results provide very important information concerning with the limitation of CO2 injection pressure when the formation fracturing pressure of 3400 psig is considered in order to avoid the formation from fracturing
Summary
Proven CO2 injection as an Enhanced Oil Recovery (EOR) technique has been implemented successfully in many oil fields worldwide. CO2 at certain conditions can dissolve into oil, make the oil swelling, and reduce both oil viscosity and interfacial tension. Such oil property changes result in easier oil removal from rock pore spaces. At a given reservoir temperature, the degree of the oil property changes depends mainly on CO2 injection pressure, the purity of CO2 injected, and chemical composition of the live oil. The higher all CO2 injection pressure, purity and hydrocarbon intermediate content, the larger the oil property changes. Lower both injection and CO2 purity and higher content of heavy hydrocarbon components or lower oil gravity, the lesser the oil property changes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
