One of the main issues during waterflooding is the early-breakthrough of the injected water through high permeable strata that reduces oil production. One remedy to postpone this problem is the implementation of pH-sensitive gel polymers. Acid pre-flushing is sometimes required to decrease near-wellbore pH and guarantee deep conformance control. Microgels have low viscosity at a low pH environment. The geochemical reactions between rock minerals and microgels increase the rock pH; consequently, microgels swell and close high permeable strata far from injection wells.

In this study, various experimental analyses are performed to investigate the application of pH-sensitive polymers as a deep conformance control agent in a Middle East carbonate formation. Our rheological analysis reveals the viscosity dependence of the implemented pH-sensitive polymer (Carbopol 934) to the environmental pH. Moreover, the formic acid pre-flushing into the carbonate sample decreases the rock pH, which provides a good condition for the microgel propagation deep into the sample. Furthermore, the gel polymer shows excellent performance on reducing the permeability of the carbonate sample (>90% permeability reduction) during the sandpack flooding experiments. Furthermore, post-acid injection shows that the de-gelling process of the gel polymer is not entirely reversible in the carbonate sample.


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