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

Abstract

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 R 2 ≥ 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.

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“…They can also solubilize the system by penetrating the inner layers of the shell, thus reducing its mechanical resistance and making it break more easily. The predominant interaction in the current case is London dispersion forces. , Also, the temperature is an important parameter for capsular rupture, as shown in a previous study focused on developing nanocapsules with a tailored breaking reservoir temperature . According to the results of the previous work, it is recommended that, for reservoirs that are at temperatures above 60 °C, the use of thermostable and resin-type covers be considered given the strength of their covalent bonds.…”

“…39,40 Also, the temperature is an important parameter for capsular rupture, as shown in a previous study focused on developing nanocapsules with a tailored breaking reservoir temperature. 14 According to the results of the previous work, it is recommended that, for reservoirs that are at temperatures above 60 °C, the use of thermostable and resin-type covers be considered given the strength of their covalent bonds. However, given the temperature of interest, the use of lecithin as a covering agent is recommended because its softening temperature is above 70 °C.…”

“…These nanoparticles are composed of a core that could be solid or liquid, covered by a shell specially designed to a targeted purpose. 14 For example, Corteś et al 15 developed surfactant (core)−resin (shell) nanoparticles for enhanced oil recovery processes. In this case, the nanocapsules were specially designed to liberate the surfactant at the oil/water interface and promote interfacial tension reductions with little surfactant adsorption over the porous medium, increasing the oil recovery.…”

“…Nanocapsule-type and core–shell-type nanoparticles have also been developed for different applications in the oil and gas industry, mainly focused on the target delivery of some chemicals in the reservoir. These nanoparticles are composed of a core that could be solid or liquid, covered by a shell specially designed to a targeted purpose . For example, Cortés et al developed surfactant (core)–resin (shell) nanoparticles for enhanced oil recovery processes.…”