Volume 63, Nº 4 (2023)

The Hildebrand solubility parameter has been applied in several areas of science and engineering, assuming a relevant role in new scientific developments and practical applications in industry. This review shows its importance and relationship with development of research in flow assurance activities, especially involving heavy fractions of oils such as asphaltenes, resins and wax. The examples described illustrate its relevance and scope in the approaches of interest of flow assurance. They also show that it is a versatile property for many new applications, including the development of methodologies to obtain more reliable values for the various petroleum fluids and theoretical developments for its estimation in a wide range of temperature and pressure.

The major contemplation in the recent decades is to minimize the operational difficulties during any drilling activity by improving the characteristics of water-based drilling fluids (WBDF). Such problem as a poor hole-cleaning because of settling of drill cutting and debris are extremely common. This problem will eventually convert into a serious non-productive time event in the form of pipe sticking. The most common additives added in the mud system to improve its rheological properties and tackle sedimentation issues are polymeric materials. During this study, four different polymers including sodium alginate and pure-bore as biopolymers, PHPA as a synthetic polymer, and the L-grade polyanionic cellulose (PAC-L) as a modified natural polymer have been used to improve rheological characteristics of WBDF. Laboratory measurements have indicated no considerable changes in the mud weight in the case of addition of these polymers. Moreover, these results reveal that all the systems behave as shear thinning fluid (flow index <1). A decrease in the dynamic viscosity with an increase in the shear rate has been observed for all samples. The disentangling of polymeric chains occurring at high shear rate eventually reduces the viscosity of these systems. In addition, samples that comprised of pure-bore and sodium alginate exhibit the desired operating magnitude of rheology (PV, YP, GS, AV, and YP/PV). These results show such particles minimize operational problems arising because of a poor hole-cleaning. In contrast, a system with PHPA and PAC-L has shown detrimental rheological characteristics. The high molecular weight of PHPA and the hydration of PAC-L in the presence of potassium chloride decrease their performance.

Flow assurance is one of the main challenges in the oil industry. Many factors can affect the oil fluidity, including the oil °API and the formation of water-in-oil (w/o) emulsions that increase the fluid viscosity. The demulsification process aims to decrease as much as possible the water content in the crude oil. Chemical products known as demulsifiers can be used to aid in this process. In laboratory, the chemicals can be evaluated under temperature and water content conditions similar to those in the oil field. In this work, the effect of demulsifier aging on its performance, simulating oil field storage, was evaluated using synthetic w/o emulsion prepared with a heavy crude oil and brine at 55 000 ppm. The crude oil was characterized and some demulsifier properties were measured along the time. The crude oil was identified as a heavy oil containing 11.6% of asphaltenes, contributing to the w/o emulsion stability. The demulsifier performance increased with aging time, and the results strongly suggested that a mere evaporation of the additive solvent occurs, concentrating its active matter

The effect of quinoline additions and amount of the sulfiding agent added on the activity of the in situ prepared NiWS catalyst in naphthalene hydrogenation was studied. In the presence of 1 wt % quinoline, the obtained catalyst shows high activity (>95% naphthalene conversion). The physicochemical properties of the catalyst were studied by XPS, X-ray diffraction analysis, and TEM. At the W : substrate molar ratio of 1 : 40 and 360°С, an increase in the amount of the sulfiding agent from 1 to 5 wt % leads to a decrease in the selectivity with respect to decalins from 68 to 39%, respectively. The degree of decoration with nickel on adding 1 wt % sulfiding agent is 0.1. As the amount of the sulfiding agent added is increased to 5 wt %, the degree of decoration with nickel increases to 0.3.

The study investigates the main routes of liquid-phase hydrogenation of endo-tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, (1)) in the presence of a PK-25 palladium catalyst (Pd/γ-Al2O3, 0.25% Pd). All the reaction products were identified, and the material balance was examined. Mild conditions were chosen for the hydrogenation of (1) to ensure that the norbornane framework was retained. For (1), like for other norbornene derivatives, the effect of prevalent adsorption of a norbornene double bond on an active site (AS) of palladium was confirmed, in contrast to other types of double bonds. Based on a combination of experimental and theoretical data, a consistent mechanism was proposed for the process, in which endo-tricyclo[5.2.1.02,6]decane (3) is obtained as the only final product. The kinetic order with respect to (1) was found to be zero within a wide range of its initial concentrations; the hydrogenation of the intermediate cycloalkene—endo-tricyclo[5.2.1.02,6]deca-3-ene (2)—was shown to have the first kinetic order. The activation parameters of the liquid-phase hydrogenation of both (1) and (2) were further determined. Based on the Langmuir–Hinshelwood approach and the concept of multiple adsorption of substrates on a single AS, an adequate kinetic model of the process was developed. It was shown that three process steps occurring by two routes significantly contributed to the reaction rate. The rate constants of these reaction steps and the adsorption constants of AS complexes with unsaturated compounds were estimated.

The study investigates interactions between palladium and silver in Pd–Ag bimetallic catalysts supported on a mesoporous carbon material Sibunit and, in particular, the dependence of these interactions on the deposition sequence of the metal precursors. Using XRD and TEM results, it was shown that impregnating the support with an aqueous solution that contained nitrate salts of both metals, followed by hydrogen treatment at 500°C, generates uniformly sized Pd0.6Ag0.4 particles (dav = 5.6 nm). These particles exhibit high selectivity (79%) in the reaction of acetylene hydrogenation to ethylene. The catalysts synthesized by sequential impregnation of the support with solutions of Pd and Ag nitrates interleaved with heat treatment in H2 exhibited a lower selectivity (68–73%) due to the formation of particles non-uniform both in composition and size (about 4 to 60 nm). The IR spectroscopy data suggest this effect is presumably associated with the removal of O-containing functional groups from the carbon surface during the reduction of the supported precursor. Given that O-groups act as anchoring sites for the precursors of active components and suppress the ability of Sibunit to reduce metals from their salt solutions, the subsequent deposition of the second metal salt causes a non-uniform distribution of this metal on the surface and the generation of larger particles.

This study investigated, for the first time, the effects of the tropical climate of Vietnam on the properties of synthetic greases with urea thickeners. The greases were exposed to seven-month field tests at climatic test stations of the Joint Russian–Vietnamese Tropical Research and Technological Center in three regions of Vietnam. This short-term exposure decreased the ultimate strength and affected the colloidal stability of the samples (in the colloidal stability measurements, the amount of separated oil was reduced). At the same time, the chemical composition of the greases remained essentially unchanged, as confirmed by IR spectroscopy. It would be reasonable to assume that the degradation of polyurea greases in tropical climates is primarily associated with their colloidal structural changes. This assumption, however, requires confirmation in further research that should involve longer exposure and a larger number of grease samples prepared from different base oils. It was additionally found that introducing a heterogeneous modifier into polyurea greases impairs their stability in tropical climate.