Development of Acid Nanocapsules with Tailored Breaking Reservoir Temperature for the Removal of Formation Damage by Fines Migration

The main objective of this study was the development of novel acid nanocapsules with tailored breaking reservoir temperatures for the controlled release of acids to dissolve fine particles. For this, thermolabile nanocapsules (NC) were synthesized using hydrofluoric acid (HF) as core and a resin/asphaltene (R/A) mixture as the shell. For the controlled release of HF under reservoir temperature, shells with different softening points were developed through changes in the R/A ratio. The nanocapsules were characterized in terms of structure, size, and chemical using transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy, respectively. A nanofluid (NF) was formulated based on the dispersion of NC in the injection brine to achieve an acid concentration of 3% w·v–1, which is a concentration commonly used for fine particles dissolution. Measurements of pH, anticorrosive power, and dissolution kinetics tests were carried out using the free and encapsulated acid at 120 °C. The characterization results verified the capsular shape, the presence of the synthesis components, the size in the nanometric regime, and the capsules’ release at different temperatures. Regarding the performance tests, the nanofluid (NF) pH was 5.67, unlike the free acid, which was lower than 1. Likewise, the corrosion rate increased by 94% for free HF concerning the encapsulated acid. Dissolution kinetics were fitted to the pseudo-first-order Lagergren model with R2 ≥ 0.90. It was observed that in the first 20 h, the dissolution rates are reduced up to 70% using encapsulated acid. Accordingly, the development of HF-based nanocapsules can increase the lifetime of the acid and reduce corrosion during the stimulation process.