The oil and gas industry heavily relies upon the use of acid systems as a stimulation strategy to increase permeability in the reservoir and thus pave the way for production of hydrocarbons from the targeted pay zone. The mineralogy of the reservoir and/or chemical composition of the damage to be removed dictates the type of acid and concentration required for the treatment. For example, carbonate reservoirs are routinely stimulated using hydrochloric acid (HCl); whereas, a so-called mud acid (i.e. mixture of HCl and hydrofluoric acid (HF)) is commonly used to stimulate sandstone reservoirs. The advantages of such acid systems are well known. The industry however is faced with the persistent challenge of developing new acid systems that overcome the limitations of existing technologies such as premature acid spending before reaching the zone of interest. We recently developed a method to generate strong acids, in an in situ fashion, by employing a redox chemistry approach whereby bromate selectively oxidizes ammonium-based salts. Importantly, the induction period leading to acid generation could be fine-tuned based on counterion selection as it was observed to scale with the pKa of the acid being formed. Here, we report on new developments in our quest to prolong the induction period and hence further delay the delivery of acid to site-specific zones in the subterranean environment. Movement towards a fit-for-purpose counterion selection strategy may improve the chance of success in applications where delayed generation of acid is needed.

Fit-for-purpose counterion selection: Ammonium oxidation as a platform for on demand acid generation

2019 Spring National Meeting

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