Development and Field Application of a New Measurement Technique for Organic Acid Additives in Stimulation Fluids

Abstract

Summary Formic and acetic acids, with and without HCl, have been used extensively over the last 40 years as stimulation fluids and as acid additives. A measurement method for these organic acids was not previously available for highly contaminated acid stimulation samples that contain high acid concentrations, dissolved oil, suspended solids, and several different acid additives. Citric and acetic acids are also used in acid treatments as iron control agents at temperatures less than 200 and 150°F, respectively. An analytical method using capillary electrophoresis was developed to simultaneously measure the concentrations of formic and acetic acids in stimulation fluids. The developed method was used to evaluate flowback samples from pickle treatments and stimulation treatments of several high-temperature wells. The following conclusions are made: A method for the simultaneous measurement of formic and acetic acids was developed, evaluated, and implemented for acid stimulation samples. Citric acid concentration can be determined in certain cases, which are identified in the paper. Results of formic and acetic acid concentrations in sandstone and carbonate corefloods were evaluated. Flowback samples from pickle treatments and acid fracture treatments were evaluated. Results from treatments of super chrome-13 and low-carbon steel tubing with 15 wt% HCl/ 9 wt% formic acid show that a small decrease in formic acid relative to chloride concentration occurred over time with carbon steel. No significant decrease of formic acid relative to chloride concentration was observed in the flowback of a well with a super chrome-13 completion.