Twenty-five acid return samples taken extensively throughout the post-treatment flow from an offshore Louisiana well showed almost complete consumption of excess hydrochloric acid (HCl) by the HF acidizing chemical process. The high HCl consumption was not due to dissolution of carbonate minerals. This observation appears to run counter to the oil industry belief of several decades that HCl was not significantly consumed in the process of stimulation with HF acid apart from calcite dissolution. Acid returns analysis also revealed an efficient ion exchange acid spending process, almost complete reprecipitation of silicon with an associated dissolution of aluminum, and good surface tension reduction for most of the acid returns.

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