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Stable polyethylene glycol-in-silicone oil phase change emulsions were successfully prepared with a selected silicone surfactant. These oil-in-oil (o/o) emulsions have been scarcely examined up, despite the highly remarkable properties of both phases for energy recovery applications and cosmetic/pharmaceutical compositions. The objective of the present work was to study the effect of composition (surfactant and disperse phase concentrations) and the post-processing conditions (further agitation at the processing temperature for 24 h) on the final features of the emulsion. For this purpose, optical morphology, thermo-physical and the rheological behaviour of the emulsions and binary blends of their compounds were measured and analysed. Special attention has been paid to structural changes and crystallinity modifications of the emulsion disperse phase. The observed miscibility of the silicone surfactant and silicone chains with the disperse phase reduces its crystallinity degree and modifies in the crystallization mechanism of the polyethylene glycol, from heterogeneous to homogeneous nucleation. Interestingly, the change in the disperse phase crystallinity remarkably modifies final thermal and rheological properties of the emulsion.

This study investigates the development of novel montmorillonite/castor oil blends to formulate sustainable lubricating greases to promote the replacement of petrochemicals industry-derived materials by substances obtained from renewable sources. Specifically, the effect of the thickener concentration on the rheological, chemical, thermal, tribological properties, and atomic force microscopy (AFM) microstructure of these systems were studied. The results showed that the C20A nanoclay content could be used to modulate the viscosity values, the linear viscoelastic functions, and tribological properties of these montmorillonite dispersions. In general, these gel-like dispersions exhibited remarkable lubricant properties; the samples showed values of the friction coefficient and wear scars similar or lower than those obtained with model bentonite grease.

Nowadays, the reduction of the environmental impact associated with the operation of the oil industry is a primary concern. A growing trend is to develop low-toxicity formulations based on biodegradable components. In this sense, vegetable oils structured with nanomaterials could be an alternative to mineral or synthetic oils for sustainable fluid formulations. Hydrophobic fumed silica nanoparticles have the capability to change the rheological behavior of oil in suspensions, providing a large variety of non-Newtonian behaviors over a wide range of temperatures, from shear-thinning to gel-like, depending on the concentration and the nanosilica’s hydrophobicity, that permits the design of fluids with selected characteristic and applications. This work explores the microstructure and the rheological behavior of hydrophobic fumed silica dispersed in a sunflower oil as a function of temperature and pressure. The results suggest that the suspensions of hydrophobic silica in sunflower oil reveals appropriate rheological and thermal properties over a wide range of temperatures and pressures to serve as components of sustainable drilling fluids.

Xanthan gum solutions have gained increasing interest for their use as environmentally friendly chemicals in the oil industry. Xanthan is compatible with most concentrate brines used for controlling formation damage and fluid loss. Particularly, formate brines reinforce the ordered structure of the biopolymer in solution, gel strength, and the specific gravity of the resulting fluid. In this paper, we studied the effect of thermal aging on the rheological behavior of xanthan solutions as a function of the concentration in potassium formate. Ionic strength below a threshold concentration does not prevent the degradation of the structure of xanthan after being submitted to aging at 165 °C. Aged solutions show an important loss of strength in their mechanical properties, lower pH, and higher content in furfural and hydroxymethylfurfural. Highly concentrated formate brines are necessary to maintain the strength of the rheological properties after exposure to high-temperature environments, This research was funded by the EU-FEDER Program, grant numbers P18-RT-4684 and CTQ-2017-89792-R

Drilling operations performed on geothermal wells require the ongoing search for sustainable fluids that will offer maximum performance and minimum environmental impact. Therefore, studies on the replacement of traditional clay suspensions in mineral and synthetic oils with clay suspensions in vegetable oils have offered some promising results. These preliminary results suggest the need for more extensive studies, including those considering high-pressure/high-temperature (HPHT) conditions, to assess the real capacity of biodegradable oils as substitutes for mineral and synthetic oils in oil-based muds (OBM) formulations. This work analyses the structure and thermomechanical properties of commercial organo-sepiolites dispersed in vegetable oils, as a function of temperature and pressure. This serves as the principal criterion for the development of environmentally-friendly OBM for HPHT drilling applications. The results suggest that organo-sepiolites in vegetable oil suspensions have suitable thermal and mechanical properties to produce sustainable and environmentally-friendly drilling fluid for application at a wide range of temperatures and pressures.

Drilling and completion operations in HP/HT environments demand the use of environmentally friendly fluids with suitable properties such as solid-free high-density and pseudoplastic behavior. Xanthan gum solutions in different brines may be an interesting alternative to ensure a suitable thermo-rheological behavior and biodegradability. Nevertheless, xanthan exposed at high temperature experiences thermal degradation that can modify the flow properties over time and limits the ceiling temperature of oilfield applications. To gain insight on this issue, this paper characterizes the flow behavior of low concentration XT solutions in calcium and potassium brines, evaluating the effect that potassium formate exerts on both the flow properties and the resistance to thermal degradation of xanthan solutions as a function of the biopolymer concentration. Xanthan in formate brine retains the pseudoplastic behavior up to 190 °C, however, low concentrate solutions undergo a thermal degradation that decreases the recovery of pseudoplasticity after being exposed to high temperature.

This work has been focused on the preparation and characterization of gel-like dispersions based on sepiolite and castor oil potentially suitable as eco-friendly lubricating greases. Particularity, the effect of sepiolite content exerted on rheological, chemical, thermal and tribological properties was studied. The system exhibited a gel-like behaviour for all the concentrations considered (20–40 wt%) related to the development of a sepiolite three-dimensional colloidal network due to its characteristic nanoscale structure formed by fibers, laths and bundles. The values of both apparent viscosity and viscoelastic functions in the linear viscoelastic region increased with sepiolite content, as a consequence of a strengthening of the gel network. An empirical correlation between viscoelastic modulus and sepiolite concentration was proposed. From tribological point of view, the friction coefficient values and wear marks obtained after the frictional tests became lower when sepiolite concentrations decrease. Gel-like dispersion formulated with 30 wt% sepiolite showed appropriate rheological and tribological behaviour to be used as biolubricating greases.

Xanthan gum solutions are used in the oil industry for flooding, drilling and completion operations. The stabilization of the structure of xanthan gum solutions in presence of salts increases the value of both the order-disorder transition temperature and the gel strength. This effect is very important in order to design drilling and completion fluids since not only density and viscosity of the fluid can be improved by increasing the concentration of salts but also the range of temperature where the solution shows viscoelastic behaviour can be extended. This paper presents results from a study on the rheological behaviour of xanthan gum solutions in different saturated brines. Chloride and formate potassium brines not only increase the viscosity of the solution but also extend the shear thinning behaviour to temperatures near 200 °C, maintaining a simple relaxation mechanism over the whole range of temperature where the ordered conformation dominates the rheological behaviour.

The main goal of this research was to compare the modification capability of two different types of bitumen modifiers: non-reactive plastomers and elastomers, and reactive polymers. The group of non-reactive polymers included a block copolymer (SBS), recycled thermoplastic polymers (EVA/LDPE blends), and crumb tire rubber, which were mixed at a processing temperature of 180 °C. In the second group, a reactive MDI–PEG prepolymer, a low processing temperature modifier (90 °C), was considered. The study was mainly focused on the characterization of the thermorheological behaviour of selected modified bitumen samples. In addition, the thermal behaviour (by modulated DSC), and morphology (by optical microscopy) of these modified bitumen samples were also evaluated. All of these bitumen modifiers significantly improve the thermomechanical properties of the resulting binder, especially at high in-service temperatures. However, whereas bitumen modified by non-reactive polymers undergo marked oxidation events due to the high processing temperature used (180 °C), MDI–PEG modified bitumen does not experience this phenomenon because of the lower processing temperature involved (90 °C). In general, non-reactive polymers should be added in much larger concentrations than the reactive polymer to obtain similar results, although the latter requires a further period of curing, at room temperature, to induce suitable modification. Finally, only MDI–PEG modified bitumen is stable when stored at high temperature (163 °C), whereas all the non-reactive polymer-modified bitumen studied undergo either phase separation or particle precipitation.

Reactive polymers are lately gaining acceptance to give added value to a residue of the crude oil refining process such as bitumen. The resulting material should display enhanced mechanical properties to be considered for advanced applications in construction. In the present paper, we report the effect of processing temperature on the reaction between bitumen compounds and an isocyanate-based reactive polymer, synthesized by reaction of polymeric MDI (4,4′-diphenylmethane diisocyanate) with a low molecular weight polyethylene-glycol (PEG). Rheokinetics experiments, viscosity measurements at 60 °C, atomic force microscopy (AFM) characterization, thin layer chromatography (TLC-FID) analysis and thermogravimetric studies (TGA) were performed on the reactive polymer and on samples of MDI-PEG modified bitumen containing 2 wt.% of the polymer. Results showed the existence of an optimum processing temperature arisen as a consequence of opposite effects: microstructural availability for the formation of a polymer–bitumen network, reaction ability and polymer thermal degradation. Consequently, this study aims to serve as a guideline for the refining and asphalt industries facing the stage of selecting the optimum processing parameters.

Asphalt, roofing, and sealing markets strongly demand new materials for being used, for instance, as bituminous coating membranes. In that sense, this paper deals with the effect on these bitumen-b...

In this study, the suitability of a reactive polymer, synthesized by reaction of 4,4′-diphenylmethane diisocyanate (MDI) with a low molecular weight polyethylene-glycol (PEG), as a modifying agent for the manufacture of bitumen-based waterproof membranes, was evaluated. With that purpose, rheological and thermal analysis tests, and microstructural observations by AFM were carried out on different samples of modified bitumen having a MDI–PEG content ranging from 0 to 10 wt.%, cured at room temperature for a period of time within 0–30 days. The results obtained demonstrate that the addition of the reactive polymer proposed in this work to bitumen is very suitable at high in-service temperatures, because a noticeable increase in the values of viscosity, at 60 °C, of the resulting modified bitumen samples is observed on a time-scale of days. AFM observations, carried out at 50 °C, evidenced that the reactive polymer MDI–PEG leads to a new microstructure, displaying a higher level of stiffness. Therefore, this polymer should be seriously taken into consideration as a modifier of bituminous coatings for the waterproofing industry.

This paper deals with the influence that both pressure and temperature exert on the viscosity of heavy petroleum fractions, such as bitumen of different penetration grades, in temperature and pressure ranges comprised between 60 °C and 160 °C and 0–400 bars, respectively. From the viscous flow tests carried out, it is apparent that bitumen behaves as a Newtonian liquid in the above-mentioned range of temperature and pressure. The temperature–pressure–viscosity relationship for bitumen of different penetration grades, mainly used for paving applications, can be modelled using a modified WLF model, the FMT model. This model includes different physical parameters, such as material compressibility and expansivity, which have been obtained from pressure–volume–temperature (PVT) measurements.

Transportation and consumption of petroleum products around the world have created a potential risk for oil spills in the environment. Knowledge of high-pressure rheological behaviour of heavy crude oil fractions, which are usually transported in oil tankers, is very important to design deep recovering operations of the oil remaining in the tanks after an accident. The effect of pressure on the viscosity of these materials is not well understood, this is mainly due to experimental constraints involving high-pressure rheology measurements at low shear rates. Consequently, the overall objective of this work is to model the temperature–pressure–viscosity dependence of a selected heavy fuel oil in a wide range of pressure and temperature. With this aim, viscous flow tests at different temperatures and differential pressures and modulated differential scanning calorimetry tests were carried out on the heavy fuel oil selected. A temperature–pressure–viscosity model (FMT model) fits fairly well the experimental results obtained in the whole differential pressure range studied. However, viscosity values at temperatures lower than 10°C cannot be predicted due to microstructural changes associated with the solidification process of the heaviest components of the fuel oil tested.