Acid Stimulation of Injectionwells in San Jacinto Geothermal Project, Nicaragua

Abstract

Acid stimulation with mechanical workover was applied in injection wells SJ1-1, SJ10-1, SJ11-1 and SJ12-1 in the San Jacinto Geothermal Project, Nicaragua to recover lost injection capacity caused by mineral (silica) deposition along the wellbore and also improve their permeability. Detailed well testing and analyses and improved acid treatment design were implemented to increase the effectiveness of the acid stimulation.
The use of memory pressure-temperature-spinner logs and improved well test interpretation became essential for better candidate evaluation, acid treatment design and quantification of pre-acidizing well parameters and evaluation of acidizing results. Further improvements in acid treatment design were also achieved with application of higher main HF acid concentration up to 12% HF acid, increased injection rates and the use of mechanical diverter. Post-acid treatment results showed around 30% to 700% increase in injection capacities.