Title: Thermo-EOR effect during steam injection in carbonate heavy oil reservoirs

Authors: Junwoo Seo; Wonmo Sung

Addresses: Department of Natural Resources and Environmental Engineering, Hanyang University, Seoul, 133791, Korea ' Department of Natural Resources and Environmental Engineering, Hanyang University, Seoul, 133791, Korea

Abstract: When the thermal method is applied to carbonate rock, the imbibitional flow into tight matrix can be increased by thermally induced wettability alteration. Furthermore, CO₂ is generated by geochemical reaction between steam and carbonate rock, resulting in thermo-EOR, which is similar to CO₂ flooding. In this study, we developed geochemical model to predict the generation of CO₂ and implemented this model into a thermal simulator. Using this thermal model, we investigated thermo-EOR effect by the generated CO₂ in heavy oil carbonate reservoirs and analysed the capillary imbibition resulting from the wettability alteration. From the results, we determined that thermo-EOR effect from the generated CO₂ only occurred under the influence of immiscible flow, which yielded additional 12.5% of oil recovery. This gain was obtained from additional decrease in oil viscosity by the dissolved CO₂ in oil and further increase in pore pressure due to the volume of the CO₂ gas. [Received: September 10, 2014; Accepted: January 19, 2015]

Keywords: carbonate reservoirs; steam injection; wettability alteration; capillary imbibition; in-situ CO2; carbon dioxide; carbon generation; thermo-EOR effect; enhanced oil recovery; heavy oil reservoirs; imbibitional flow; geochemical modelling; simulation; immiscible flow; oil viscosity; pore pressure.

DOI: 10.1504/IJOGCT.2016.074288

International Journal of Oil, Gas and Coal Technology, 2016 Vol.11 No.2, pp.111 - 126

Received: 15 Sep 2014
Accepted: 19 Jan 2015
Published online: 21 Jan 2016 *

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