CO2 Foam Field Trial at North Ward-Estes

Abstract

ABSTRACTA CO2 foam field trial was conducted in the North Ward-Estes field in Texas to evaluate the effectiveness of foam in improving CO2 sweep efficiency. This paper describes the design, results, and analysis of foam treatment with emphasis on the design methodology of applying foam in grossly heterogeneous reservoirs, characterized by uneven areal and vertical sweep in most patterns.Over a period of nearly two years, foam was emplaced into an injector four times by alternately injecting CO2 and surfactant solution, and followed by continuous CO2 injection after each emplacement. Foam was generated in situ, which reduced CO2 injectivity by 40 to 85%. Gas production in the problem producer decreased dramatically, while gas and oil production in other offset producers increased, indicating areal diversion. Vertical diversion also occurred, as evidenced by significant increase in oil production in the problem producer, where tertiary oil response had peaked prior to the foam treatment.The field test shows that a properly designed foam treatment can significantly improve the CO2 sweep efficiency and be economically successful. The methodology developed in the design and analysis of the foam test may be applied to other conformance improvement processes.