A New Approach to Designing the Optimum Acid Treatment for Sandstone Reservoirs

Abstract

Since the early days, various acid types have been developed along with additives to help make acidizing more effective. Hydrofluoric acid (HF), unlike other acids, has a specific reactivity with silica which makes it more effective for use with sandstone reservoirs. Despite the significant advancements made in the area of acidizing, the success rate of treatments remains low with some companies reporting failure in 25 to 30% of treatments.

There have been great efforts in developing a systematic method for designing matrix acidizing treatments. Previous guidelines have highlighted the main factors affecting the treatment design to be mineralogy, permeability, and temperature. In this study our goal was to integrate the past experiences highlighted in the literature, the previously developed advisory systems, and the practical experiences of the research team to develop new software that can help design acid treatments.

A comprehensive examination of sandstone acidizing chemistry, previous guidelines, and practical experiences in the literature show that the HF concentration significantly controls the output of the treatment. It is clear that previous guidelines have emphasized the importance of using lower HF concentrations with the increase of mineral content. This hypothesis was represented graphically and experiments were designed to investigate its accuracy. Results show that these curves present a useful tool for better designing field treatments.