Experimental study and application of tannin foam for profile modification in cyclic steam stimulated well

Background: Tannin foam is a good blocking agent with permeability selection and high temperature tolerance. Tannin foam can improve strength and stability of aqueous foam. Methods: The aim of the study was to investigate whether tannin foam has good performance for profile modification in cyclic steam stimulated well. Through sandpack displacement experiments with single and parallel sandpacks under high-temperature, the effects of foam quality, permeability, injection mode, temperature, permeability ratio, and oil saturation on blocking and profile modification capabilities of tannin foam were studied. The performances of tannin foam and conventional high-temperature foam were compared. Results: Experimental results indicate that blocking capability for tannin foam first increases and then reduces with the foam quality, and the best foam quality is 50% in the experiments. The resistance factor increases with permeability, and decreases with temperature. Co-injection of tannin solution and gas is better than SAG injection. Gelled tannin may enhance the bubble film strength, and increase the foam stability and blocking capability compared to the conventional high-temperature foam. When the permeability ratio of two sandpacks is less than 4.18, the profile modification is good. As the permeability ratio increases, tannin foam is easy to flow out of the high permeability sandpack, and profile modification decreases. Although irreducible oil in the sandpack reduces foam strength, tannin foam still has obvious profile modification capability in sandpacks with water-flood irreducible oil. Tannin foam was applied for profile modification in two cyclic steam stimulated wells. The wellhead pressure for steam injection with tannin foam increased at least 2 MPa, indicating that tannin foam blocked steam channels in formation. Oil production improvement and water cut decrease are obvious. Conclusion: Tannin foam is effective for modifying steam profile, increasing oil production, and decreasing water cut in cyclic steam stimulated wells with high water cut. (C) 2014 Elsevier B.V. All rights reserved.