Enhanced oil recovery (EOR) techniques play an essential role in the maintenance of petroleum production worldwide. These techniques are receiving special attention due to the continuous decline in availability of oil resources. The study of surfactants and correlated systems have been considered due to their capacity to alter the wettability and interfacial proprieties, consequently reducing residual oil saturation and increasing oil production. In this context, heterogeneity becomes one of the main challenges to overcome, for it makes the fluid flow preferably thought the highest permeability regions, affecting sweep efficiency. It is also known that acids react with carbonate formations promoting matrix dissolution. However, few works in the literature report the use of reactive fluids in EOR. Therefore, this work analyzes the effects of reactive acid flow on porous carbonate media and its impact on advanced oil recovery operations. It presents an experimental study of the effects of acid microemulsion flooding in the enhancement of oil recovery in carbonate reservoirs. Acid microemulsions studied were characterized by surface tension, droplet diameter, viscosity, and corrosiveness. Flooding experiments demonstrated that the reactive flow of acid microemulsions in porous media increases oil recovery, achieving up to 30% additional recovery of the total oil in place. However, by increasing the reactivity of the systems, severe dissolution of the porous matrix can occur. The results presented open a new path on the use of low reactive fluids in enhanced oil recovery.

MICROEMULSIONS AND NANOEMULSIONS APPLIED TO WELL STIMULATION AND ENHANCED OIL RECOVERY (EOR)

The present work demonstrates the production of chlorapatite (ClAp) through thermal decomposition of chemically treated fish scales, originating from an Amazon fish species (Arapaima gigas). The scales were treated with hydrochloric acid (HCl) solution for deproteinization. Afterwards, the solution was neutralized by sodium hydroxide (NaOH) treatment to obtain an apatite-rich slurry. The heat treatment was carried out at different temperatures including 600 °C, 800 °C, and 1000 °C. The powders obtained were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). The XRD analysis and FTIR spectra confirmed the incorporation of chlorine into the apatite structure. The FTIR results showed absorption bands relative to the OH^–, PO₄³⁻ functional groups which are a characteristic of chlorapatite. Moreover, the intensity of the OH–Cl elongation could be observed. Chlorapatite Ca₅(PO₄)₃Cl, NaCl, and NaCaPO₄ phases were identified, achieving up to 87.4 wt% for ClAp. The SEM observations show that with increasing temperature, the ClAp obtained consists of slightly larger, more crystalline grains. Furthermore, the grains ranged in size, between 1-5 μm and ClAp1000 sample recorded crystallinity of 84.27%. ClAp and NaCaPO₄ can be used in electronics as phosphor materials due to their luminescence and biomedical applications.

The subject of rock–fluid interaction is important in cases where flow through porous media is occurring. One special case is when the fluid reacts with the porous matrix. In this case, the mass transfer and reaction rate control the dissolution pattern. This article aimed to study the interaction between an acid nanoemulsion system and a carbonate porous media. Nanoemulsions were developed to retard the rock’s dissolution and to promote the formation of conductivity channels. Nanoemulsions were prepared using ALK100 (alkyl alcohol ethoxylate) and RNX110 (alkylphenol ethoxylate) (nonionic surfactants), sec-butanol (co-surfactant), xylene isomers (oil phase), and a solution of HCl (aqueous phase). The obtained systems were characterized in terms of surface tension, droplet diameter, and reactivity. X-ray fluorescence/diffraction (XRF/XRD) and X-ray microtomography (microCT) were performed on carbonate porous media samples treated with the acid systems in order to observe the effects of the fluid–rock interaction. The results showed that the acid nanoemulsion, presenting a low oil content formulation, showed the low surface tension and droplet size characteristic of nanoemulsions. It was experimentally verified that the reactivity in the nanoemulsion media was mass-transfer-retarded, and that the wormhole pattern was verified under the studied conditions.