SiO2-Based Nanofluids for the Inhibition of Wax Precipitation in Production Pipelines.

Wax deposition in high-wax (waxy) crude oil has been an important challenge in the oil and gas industry due to the repercussions in flow assurance during oil extraction and transportation. However, the nanotechnology has emerged as a potential solution for the optimization of conventional wax removal and/or inhibition processes due to its exceptional performance in the alteration of wax morphology and co-crystallization behavior. In this sense, this study aims to study the performance of two commercial wax inhibitor treatments (WT1 and WT2) on the wax formation and crystallization due to the addition of SiO2 nanoparticles. Differential scanning calorimetry experiments and cold finger tests were carried out to study the effect of the WT on wax appearance temperature (WAT) and the wax inhibition efficiency (WIE) in a scenario with an initial temperature difference. In the first stage, the behavior of both WT in the inhibition of wax deposition was achieved, ranging in the concentration of the WT in the waxy crude (WC) oil from 5000 to 50,000 mg·L-1. Then, NanoWT was prepared by the addition of SiO2 nanoparticles on WT1 and WT2 for concentrations between 1000 and 500 mg·L-1, and the performance of the prepared NanoWT was studied at the best concentration of WIT in the absence of nanoparticles. Finally, the role of the nanofluid concentration in wax inhibition was accomplished for the best NanoWT. Selected NanoWT with nanoparticle dosage of 100 mg·L-1 added to WC oil at 5000 mg·L-1 displays reductions in WAT and WIE of 15.3 and 71.6 for NanoWT1 and -2.2 and 42.5% for NanoWT2. In flow loop experiments for the crude oil at temperatures above (30 °C) and below (16 °C), the WAT value indicates an increase of 8.3 times the pressure drops when the crude oil is flowing at a temperature below the WAT value. Therefore, when NanoWT1 is added to the crude oil, a reduction of 31.8% was found in the pressure drop in comparison with the scenario below the WAT value, ensuring the flow assurance in the pipeline in an unfavorable environment. Based on the pressure-drop method, a reduction greater than 5% in the wax deposit thickness confirms the wax deposition inhibitory character of the designed NanoWT.

Development and Evaluation from Laboratory to Field Trial of a Dual-Purpose Fracturing Nanofluid: Inhibition of Associated Formation Damage and Increasing Heavy Crude Oil Mobility.

This study aims to develop and evaluate fracturing nanofluids from the laboratory to the field trial with the dual purpose of increasing heavy crude oil mobility and reducing formation damage caused by the remaining fracturing fluid (FF). Two fumed silica nanoparticles of different sizes, and alumina nanoparticles were modified on the surface through basic and acidic treatments. The nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, zeta potential and total acidity. The rheological behavior of the linear gel and the heavy crude oil after adding different chemical nature nanoparticles were measured at two concentrations of 100 and 1000 mg/L. Also, the contact angle assessed the alteration of the rock wettability. The nanoparticle with better performance was the raw fumed silica of 7 nm at 1000 mg/L. These were employed to prepare a fracturing nanofluid from a commercial FF. Both fluids were evaluated through their rheological behavior as a function of time at high pressure following the API RP39 test, and spontaneous imbibition tests were carried out to assess the FF's capacity to modify the wettability of the porous media. It was possible to conclude that the inclusion of 7 nm commercial silica nanoparticles allowed obtaining a reduction of 10 and 20% in the two breakers used in the commercial fracture fluid formulation without altering the rheological properties of the system. Displacement tests were also performed on proppant and rock samples at reservoir conditions of overburden and pore pressures of 3200 and 1200 psi, respectively, while the temperature was set at 77 °C and the flow rate at 0.3 cm3/min. According to the effective oil permeability, a decrease of 31% in the damage was obtained. Based on these results, the fracturing nanofluid was selected and used in the first worldwide field application in a Colombian oil field with a basic sediment and water (BSW%) of 100 and without oil production. After two weeks of the hydraulic fracture operation, crude oil was produced. Finally, one year after this work, crude oil viscosity and BSW% kept showing reductions near 75% and 33%, respectively; and having passed two years, the cumulative incremental oil production is around 120,000 barrels.