B.J. Ben Shiau, Tzu-Ping Hsu, Sang-Ho Bang, Bruce L. Roberts, and Jeffrey H. Harwell
Enhanced Oil Recovery, Ammonium Carbamate, CO2 Generation, Chemical Flooding
In this endeavor, laboratory studies show promising results of a novel approach, enhanced oil recovery (EOR) by combining carbon dioxide-generating chemicals and chemical flooding to improve viscous oil recovery. The advanced low interfacial tension (IFTs) surfactant system is formulated by a ternary surfactant/cosurfactant mixture to prevent the negative impact from divalent cations. Before injection of the surfactant slug, in situ CO2 generation was first initiated by decomposition of the CO2 produced reagent to decrease oil viscosity and achieve favorable mobility ratio which can further improve sweep efficiency of the trapped oil. We evaluated several potential CO2-generating reagents exposed to elevated temperature to improve surfactant-only chemical floods. Ammonium carbamate showed the ability to generate CO2 when exposed to elevated temperatures (> 85 °C) in batch reactors. Performance of oil recovery for carbamate was further studied in both one-dimensional sand pack and a high-pressure steel column apparatus. Injection of a 0.5 PV of 3% carbamate solution with a surfactant/polymer flood improved oil recovery by 9.7% OOIP compared to similar surfactant/polymer flood in the absence of carbamate pre-treatment. It is concluded that the use of carbamate can have a positive impact on the mobility ratio for heavy crude by reducing crude oil viscosity.
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