Evaluation of the performance of acids for effective stimulation of a sandstone formation

Abstract

Optimum acid selection based on reservoir condition is one of the key elements in achieving a successful treatment in sandstone matrix acidizing. This work will investigate the effectiveness of several type of acid in sand stone reservoir stimulation. PROSPER well modeling package was utilized for the model development. Pre- acid job analysis was carried out to establish the well performance before acidization. Acid stimulation was implemented with Hydrochloric (HCl), Formic, Acetic, Propionic and ChloroAcetic acids. Thereafter, post-job analysis was done to ascertain the improvement in well productivity index for each of the acids. Result shows that the reservoir will deliver 11296.5 STB/day of liquid into the wellbore for a production index of 3-STB/day-psi without acid stimulation and the well will produce 6726.05 STB/day of liquid. Results reveals a decrease in productivity index as the treatment acid was change from HCl acid to formic acid, acetic acid and propionic acid. A productivity index values of 3.07074STB/day-psi, 3.0375 STB/day-psi, 3.01038 STB/day-psi, 3.00791 STB/day-psi were obtained when the formation was acidized with HCl acid, formic acid, acetic acid and propionic acid. A percentage increase of 15.1973%, 7.5731%, 1.95684% and 1.47001% in permeability was observed as the formation was treated with HCl acid, formic acid, Acetic acid and Propionic acid. Results reveals that HCl acid resulted in highest permeability increase. It was therefore concluded that the formation should be acidized with HCl acid since it gave the highest productivity index, percentage increase in permeability, porosity and the highest improvement in skin factor.