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Experimental Evaluation of Oxidizing Breakers for a Polyacrylamide-Based Re-Crosslinkable Preformed Particle Gel

Wang, Ze, Bai, Baojun, Zhou, Enze, Pu, Jingyang, Schuman, Thomas
Energy & fuels 2019 v.33 no.6 pp. 5001-5010
calcium hypochlorite, fuels, gels, sodium hypochlorite, temperature
Re-crosslinkable preformed particle gel (RPPG) is a newly developed conformance control agent that can reassemble as an integrity after swelling in water. However, the RPPG has the potential to plug the injection facilities or wellbore if a treatment is not properly designed. This study focuses on selecting and evaluating the oxidizing breakers that can effectively degrade the RPPG. Bottle tests were conducted by immersing the re-crosslinked RPPG in the breaker solutions. The RPPG weight change was measured with time to analyze the breaking process. Four types of oxidizing breakers, NaClO, Ca(ClO)₂, heat-activated Na₂S₂O₈, and NaOH-activated Na₂S₂O₈ were examined. The effect of factors, including breaker concentration, temperature, RPPG concentration on the gel breaking rate and completeness, was investigated. According to the results, three of the breakers were proven effective, excluding the Ca(ClO)₂, which impaired the breaking process by generating a compact cover on the surface of RPPG. The NaOH-activated Na₂S₂O₈ was the most effective breaker benefitting from its wide practical temperature range and effectiveness at the conditions of low breaker concentration or high RPPG concentration. More generally, the RPPG breaking was faster and more complete with a higher breaker concentration or a higher temperature. However, the increment of the RPPG concentration significantly increased the breaking time and the percentage of residue weight to the RPPG original weight.