A redox chemistry approach has been employed to synthesize an assortment of acids under the harsh conditions of the subterranean environment for the purpose of enhancing productivity from hydrocarbon-bearing rock formations. Experimental studies revealed that bromate selectively oxidizes a series of ammonium salts NH4X where X = F-, Cl-, Br-, SO42-, and CF3CO2- to produce 5-17 wt% HX. Importantly, the in situ method allows strategic placement of the acid in the zone of interest where the fluid is heated, and the reaction is triggered. Ammonium counteranions are shown to influence the kinetics of the bromate-ammonium reaction, and the conditions are tailored to promote oxidation of ammonium at reservoir temperatures. The reaction is observed to be autocatalytic, where acid generation prompts rapid product delivery. As a result, an induction period that scales with the pKa of the acid being formed allows strategic tailoring of the reaction profile according to the needs of the application. The utility of this approach for stimulating carbonate and sandstone reservoirs with different acid packages will be shown.

Bromate oxidation of ammonium salts under harsh reservoir temperatures for strategic acid placement

2019 Spring National Meeting

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