(35) A NEW METHOD TO ASCERTAIN THE HF STRENGTH OF ACIDIZING FLUIDS USING ION SELECTIVE ELECTRODE
Ion selective electrodes (ISE) can accurately measure the strength of hydrogen fluoride (HF) acids used for acidizing jobs. The accurate measurement of free fluoride generated from the hydrolysis reaction, especially with weaker organic acids, is important to ensure that the desired acid fluid strength is delivered downhole during well stimulation operations.
Unlike inorganic acids such as hydrochloric that dissociates completely, organic acids only partially dissociates in solution, and as such do not completely hydrolyze the fluoride ion source such as ammonium fluoride or ammonium bifluoride to generate the required amount of HF. Furthermore, the presence of multiple dissociable protons with different acid strengths on organic acids such as citric acid and Etidronic acid further exacerbates the problem. Therefore, there is the need to accurately measure the amount of hydrogen fluoride generated for acidizing fluid treatments.