Potential of CO2-eor associated with CCS in Vietnam

Abstract

CO2-EOR has a potential not only in enhancing oil recovery but also in CO2 storage. It is, however, necessary to understand the technical, operational and economic uncertainties by conducting a pilot test for applying CO2-EOR to actual oil fields. This paper describes the methods and procedures to design an inter-well CO2-EOR pilot test and discusses the potential of CO2-EOR in offshore fields, Vietnam.
We devised screening criteria in terms of saturations and reservoir pressure to select locations for pilot tests based on the reservoir model developed and calibrated with the actual field data. The number of pilot wells was determined to be one (1) injection well and two (2) production wells in order to estimate areal sweep efficiency during CO2 injection at a minimum cost. To confirm the effects of CO2-EOR, well interval, cumulative CO2 injection volume and duration were determined to be 300m, 2,000 tons and two weeks, respectively. The oil production rate began to increase after 1 month from the beginning of the pilot test, and the gas production rate and the vapour phase CO2 mole fraction also began to increase at the same time. Then, the oil production rate reached the peak, which corresponds to oil bank, after 1.5 months from the beginning, and the effect of CO2-EOR was confirmed clearly. If oil saturation is high at the target reservoir, it would be difficult for confirming the oil bank clearly. In such case, pre-water injection before CO2 injection is conducted to reduce the oil saturation at the target reservoir.
In parallel, a CO2 procurement and a new platform were designed through the process optimisation study. Manufactured CO2 was selected as CO2 source for the pilot test due to easy availability and minimum cost. The packed manufactured CO2 into tank containers was transported to the injection site by trucks and supply vessels. From a CO2 impact study, the potential risks related to corrosion and scale formation can be manageable by suitable countermeasures such as corrosion resistant alloys (CRAs) and inhibitors.
We also estimated the CO2 volume for storage in the reservoir when CO2 injection was applied. We found about half of the injected CO2 volume to remain in the reservoir at the normal operational conditions for CO2-EOR. Through this study we proposed a methodology to devise a pilot test plan of CO2-EOR in any offshore, remote oil field.