Kinetics of Tertiary Reaction of HF on Alumino-Silicates

Abstract

Abstract The standard description of HF acidizing chemistry clearly demonstrates a primary and secondary reaction of HF with alumino-silicates. Field experience has taught our industry that possible precipitation during the secondary reaction can adversely affect treatment success. This statement has been particularly true in formations with high K-feldspar content or formations having temperatures above 300°F. Recent work has also reported the existence of a third, or tertiary reaction of HF with alumino-silicates. This paper reports how the rate law and kinetics for this tertiary reaction are determined on kaolinite and feldspar over a broad temperature range. This document also discusses the discovery of how most clays were thermally unstable to HCl at temperatures above 250°F. These findings were made possible by recently applied experimental techniques including F NMR Spectroscopy, fractional pore volume flow experiments, and an accurate knowledge of the HF stoichiometry.