The Optimum Mixture of Organic Acid and HCL for the Matrix Acidization of a Carbonate Reservoir

Abstract

Due to high dissolving power, Hydrochloric acid is the most common acid for acidizing of carbonate reservoirs. Two factors limit the usage of this acid: The high reaction rate and the resulting corrosion of facilities. In order to control the reaction rate, it is beneficial to mix HCL and organic acids that helps in optimizing the wormhole penetration and as a result enhance the productivity. There are several studies that have investigated the effect of adding organic acids to hydrochloric acid at elevated (>200˚F) temperatures in the limestone carbonate reservoir. The objective of this work is to investigate the effect of different organic-HCL mixtures and concentrations at the lower reservoir temperatures of 140˚F. We carry out reaction rate and dissolving power measurements and compare the results with that of HCL only case. We add acetic acid with 8-13% concentration and formic acid with concentrations ranging from 5 to 9%. We find that mixture of HCL and organic acids outperforms the HCL solely at the lower reservoir temperatures. We observe that using HCL and acetic acid with 15 and 13% concentration, respectively, increases the neutralization time and has the most optimum reaction and dissolution rate in comparison with other mixtures studied.