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Molecular weight fractionation via stepwise precipitation or chain scission is performed on four pour point depressant polymers to study the pour point reduction mechanism. An homologous series of model oils is prepared by dissolving 5 wt % of a single-component paraffin wax (n-C24, n-C28, n-C32, or n-C36) in n-C12. The polymers are dosed at 500 ppm in the model oils and moderately reduce crystallization temperatures by elevating the nucleation barrier. Polymers containing carboxylate or acrylate moieties also modestly enhance equilibrium wax solubility. Reduction in crystallization temperature is largely independent of polymer molecular weight, except for carboxylate polymers where low molecular weight fractions are largely ineffective. In general, model fluids containing shorter wax chains show a larger reduction in crystallization temperature than model fluids containing longer wax chains. However, yield stress reduction often shows a distinct dependence on polymer molar mass. Low molecular weight fractions of carboxylate and acrylate polymers provide smaller reductions in yield stress than the overall parent fraction. Cross-polarized microscopy reveals that polymers reduce the crystal size, alter the crystal morphology from platelet to needle-like, and induce branching. Crystal branching and formation of dendrite-like structures result from strong polymer binding at the wax crystal interfaces. Hence, single-component wax crystal branching occurs phenomenologically along with yield stress reduction.

Vapor–liquid equilibria data of three poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)/water liquid crystals (LCs) with CO2 has been obtained up to 6 bar. The investigated LCs consist of 60% (EO)3(PO)50(EO)3 (Pluronic L81), 70% (EO)8(PO)47(EO)8 (Pluronic L92), and 70% L92-NH2. The maximum CO2 loading of the LCs was 5–13 g CO2/kg sample. Pure L81 and L92 displayed higher absorption of CO2 than the LCs. Rheology measurements revealed that the increasing viscosity of the samples decreases the CO2 loading. Water diffusion in the LCs was qualitatively investigated by nuclear magnetic resonance, confirming that free water and tightly bound water are present in the LCs. 2020 The Author(s). Published with license by Taylor and Francis Group, LLC This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

Plastics in marine environments undergo molecular degradation via biocatalytic and photocatalytic mechanisms. Abandoned, lost, or discarded fishing gear (ALDFG) damages marine and coastal environments as well as plant and animal species. This article reviews ghost fishing, ecological damage from marine plastics, recommended recycling practices and alternative usages of derelict fishing gear. Material mixing techniques are proposed to counteract the effect of biocatalytic and photocatalytic biodegradation within the context of plastic fish net recycling. There is a need for a new and rapid “multidimensional molecular characterization” technology to quantify, at a batch level, the extent of photocatalytic or biocatalytic degradation experienced on each recovered fishing net, comprising molecular weight alteration, chemical functional group polydispersity and contaminant presence. Rapid multidimensional molecular characterization enables optimized conventional material mixing of recovered fishing nets. In this way, economically attractive social return schemes can be introduced for used fishing nets, providing an economic incentive for fishers to return conventional fishing nets for recycling.

Yield stress fluid flows occur in a great many operations and unit processes within the oil and gas industry. This paper reviews this usage within reservoir flows of heavy oil, drilling fluids and operations, wellbore cementing, hydraulic fracturing and some open-hole completions, sealing/remedial operations, e.g., squeeze cementing, lost circulation, and waxy crude oils and flow assurance, both wax deposition and restart issues. We outline both rheological aspects and relevant fluid mechanics issues, focusing primarily on yield stress fluids and related phenomena. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/)

Reservoir production is frequently supported by using flooding fluids, often seawater. The efficiency is affected by various factors, such as the wettability of the reservoir rock and the mobility ratio between reservoir oil and injected fluid phase. These factors again influence sweep efficiency, which is the fraction of the total reservoir oil volume in contact with injected fluid during oil recovery. Addition of nanoparticles can affect the sweep efficiency on a macroscopic level by increasing the volume of petroleum in contact with the flooding fluid. Presented here are core-flooding studies performed using cellulose nanocrystals (CNC) of different concentrations in low-saline water. The studies were performed to investigate the injectivity of CNC into a high-permeable sandstone core, and to observe the effects addition of electrolytes had on the rheological properties of a low concentration dispersion of CNC. Zeta- potential and shear viscosity of dilute dispersions containing CNC was investigated under increasing electrolyte concentration. The flooding experiments show that the CNC has good injectivity in sandstone for all concentrations used, and the viscosity measurements performed on the effluent prove that the particles are able to travel through the core. Being sufficiently small for injection into sandstone and showing good colloidal stability at low salinities, CNC particles have the premises necessary to function properly as a flooding additive for enhanced oil recovery (EOR) in sandstone reservoirs.

Nanoparticles coated with poly(octadecyl acrylate) (POA) pour-point depressants are investigated, and the effect of the amount of coating material is investigated and compared with the effect of the coating material without nanomaterial. Pour point depressing performance is demonstrated using a model waxy oil system in order to isolate material performance. The present study focus on the effect of how the amount of coverage of the nanoparticles affects the performance of the nanoparticles. In order to access this information, the adsorption of the poly(octadecyl acrylate) (POA) on silica (the material of the nanoparticles) was determined using a quartz crystal microbalance with dissipation monitoring (QCM-D). Adsorption was performed from two different solvents, toluene and dodecane, because the nanoparticles were been prepared from toluene while the model system used is dodecane-based. Using the QCM-D data, it was possible to prepare nanoparticles with different amounts of poly(octadecyl acrylate), as de...

A new continuous nonlinear rheological model is established to quantify, correlate, and predict the thixotropic viscoelastic and visco-plastic properties of waxy crude oil gels. A complete rheological description of the gel is afforded by quantification of the maximum stress point (so called static yield stress) in conjunction with viscosity of the pristine gel and final slurry. Extraneous parameters are derived from the maximum stress condition. In order to develop an understanding of flow restart processes within gelled pipelines, direct numerical simulation of pressure propagation in weakly compressible thixotropic elasto-viscoplastic gel (Oldroyd-B fluid model) is performed using the rheological correlations. Deficiencies associated with conventional Bingham yield stress and conventional shear thinning methodologies are concomitantly revealed by the present elasto-viscoplastic model. Depending on parametric values, pressure may propagate and flow may commence for pipeline lengths larger than the critical length, L c = Δ p R / 2 τ y , (where Lc is the flow restart length for a yielding gel without microstructure breakage, Δp is the applied pressure, R is the pipe radius, and τy is the yield stress). Prior to attaining the critical length, the nature of the pressure wave is shown to be either inertial or viscous, depending on the initial gel viscosity. Upon approaching the critical length, the nature of the pressure wave is governed by gel degradation, except at extreme compressibility values. At high compressibility, the nature of the pressure wave is controlled by gel degradation, even prior to reaching Lc, facilitating flow commencement in long pipes via a sequential breakage process. At very low compressibility, the pressure wave propagates until the force exerted by the fluid on the wall evenly balances the applied pressure. Hence, the pressure wave may propagate beyond the critical length but sustained flow does not commence. At intermediate compressibility values, if propagation of pressure to the critical length causes mean near-wall gel deformation on a similar magnitude as the static yield strain value ( γ ≡ χ Θ Δ p 2 / 2 τ y ∼ γ s , where χ Θ is the isothermal compressibility) then the pressure wave does not propagate substantially beyond Lc and flow does not restart in the pipeline. For intermediate compressibility when γ > >γs, then flow restarts via the high compressibility mechanism (e.g. low gel strength cases) and when γ

Introduction of nanomaterials constitutes a novel and efficient means to enhance the performance of polymeric pour point depressants (PPDs). Based on the specific layered structure and favorable cationic exchange characteristics of nano-clay particles in the presence of charged organic compounds, an original hydrophilic nano-clay is first modified by octadecyl trimethyl ammonium chloride (OTAC) and then by polyoctadecylacrylate (POA). The modified nano-clay serves as an effective nanocomposite PPD. Compared to an identical content of POA, addition of POA/clay nanocomposite PPD to Changqing waxy crude oil improves the rheological properties while elevating the wax appearance temperature of the oil. Polarized microscope observation shows that POA/clay nanocomposites provide wax nucleation sites upon which wax molecules assemble and precipitate. Addition of POA/clay nanocomposite PPD results in larger and more compact crystal morphology, thus inhibiting the formation of a network structure, and further improving rheological properties of waxy crude oil.

Xanthan gum and scleroglucan are assessed as environmentally friendly enhanced oil recovery (EOR) agents. Viscometric and interfacial tension measurements show that the polysaccharides exhibit favorable viscosifying performance, robust shear tolerance, electrolyte tolerance, and moderate interactions with surfactants. Non-ionic surfactants and anionic surfactants bind to xanthan gum and transform the backbone conformation from a strong helix to a more flexible structure, reducing the viscosifying efficacy of xanthan. In contrast, non-ionic surfactants and anionic surfactants bind to scleroglucan and increase the viscosifying efficacy by non-electrostatic interactions or imparted electrostatic effects. The two polysaccharides are technically viable as viscosifying agents in typical EOR injection fluid formulations.

A new class of hybrid pour point depressants (PPDs) are developed on the basis of poly(octadecyl acrylate) (POA) functionality and POA/nanosilica hybrid particles. Activity performance is demonstra...

Wax crystallization processes are investigated using differential scanning calorimetry, near-infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The performance of a chemical additive is assessed using calorimetry and NMR. Heat flows of model waxy oils are obtained using differential scanning calorimetry, providing the wax appearance temperature and crystallization profiles. The effect of cooling rate, wax content, asphaltene, and chemical additive on the wax appearance temperature is investigated. The wax appearance temperature increases with increasing wax contents. The wax appearance temperature decreases in the presence of chemical additive, effectively increasing the instantaneous supersaturation. Furthermore, near-infrared spectroscopy and nuclear magnetic resonance spectroscopy are utilized to determine wax appearance temperature. The NMR experiments quantify liquid and solid fractions at thermal equilibrium conditions, effectively circumventing the need for dynamic thermal techniques.

Waxy crude oil rheology measurements are essential to the accurate simulation of pipeline shut-in and restart processes. Flow start-up simulators have recently emerged with powerful capabilities to exploit pressure wave propagation and ensure flow commencement, while minimizing usage of environmentally adverse chemicals. In comparison to conventional force balance methodologies, the currently presented analytical and simulation technique constitutes a step change improvement in flow assurance capabilities by integrating accurate deformation-dependent gel degradation rheology with an Eulerian numerical scheme, affording predictive assessment of restart delay times. The new methodology is applied to the case of a real 1.84 km field pipeline transporting high waxy crude oil.

A conservative analytical method is presented to provide reliable predictions for waxy oil pipeline shut-in and restart. A comprehensive bench-top characterization regimen establishes in situ gel properties, utilizing thermodynamic modeling, differential scanning calorimetry, and rheometry to forecast the wax-gel mechanical response. For flow commencement modeling, pressure wave propagation simulators have recently emerged with correct predictions for the acoustic, viscous, and gel degradation regimes. Scaling analysis shows that the viscous wave is determinative for achieving timely restart in long pipelines. The informed rheology serves as a useful input to simulate restart flows. For gelation and shut-in flow predictions, a heuristic approach is currently recommended.

Paraffin precipitation during pipeline transport of waxy crude oils gives rise to several challenges, including wax deposition, flow reduction, and gel formation, which adversely impacts pipeline performance. Small dosages of polymeric wax inhibitors or pour point depressants comprise an effective preventative measure. In this article, the structural character, functionality, and mechanisms of the polymeric additives targeting paraffin wax are reviewed, and factors influencing product efficacy are summarized. Most polymeric additives contain a nonpolar moiety as well as a polar moiety, with the exception of crystalline-amorphous copolymers. Via nucleation, adsorption, co-crystallization and solubilization interactions, polymeric additives alter the morphology and interface of precipitated wax crystals, inhibiting wax deposition, improving flow, and impeding gel formation. The presence of asphaltenes significantly impacts wax crystal morphology and interfaces, thus influencing the mechanism of polymeric ad...

A novel filtration technique is used to investigate the physical nature of interactions between pour point depressant polymers and paraffin wax crystals, with the aim of furthering development of new PPD polymer architectures. Polymer–paraffin interactions are isolated using model waxy fluids containing commercial paraffin wax dissolved in an organic solvent. Initial physical property characterization comprising pour point, wax appearance temperature and carbon number distribution serves to identify a Fischer–Tropsch wax as suitable for the investigation, with properties similar to waxes naturally occurring in paraffinic crude oils. Five pour point depressant polymers with various active chemistries are selected for the investigation. The filtration technique reveals concomitant trends in quantitative phase partitioning and liquid depletion, showing two separate and distinct activity modes: (1) thermodynamic and (2) interfacial. Quantitative phase partitioning analysis shows that thermodynamically-active architectures induce a drastic reduction in mid-range paraffin solubility, and steady state fluorescence emission analysis reveals that thermodynamically-active polymers are depleted during paraffin precipitation, confirming co-crystallization of paraffin wax molecules together with PPD polymers. Gibbs free energy thermodynamic equilibria computations performed for untreated systems confirm deviatoric precipitation induced by thermodynamically-active PPD architectures. Interfacially-active polymer architectures, on the other hand, show a distinctly dissimilar activity mode. Interfacially-active polymer architectures are not heavily depleted during paraffin precipitation and do not induce an extraordinary reduction in mid-range paraffin solubility, but are instead preferentially active at the interface. Both polymer types may impart steric repulsion, entropic repulsion, and/or morphological modulation to afford overall fluid flowability and inhibit gel formation. Finally, concrete evidence is presented of paraffin solubilization comprising an important activity mode for certain PPD architecture types, based on DSC data, cross polarized microscopy, steady state fluorescence, as well as high temperature gas chromatography. In aggregate, the filtration technique establishes a useful R&D tool for assessment of PPD activity mechanisms, elegantly illustrating architecture-modulated activity modes on a compositional basis.

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min−1. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min−1. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines.

An experimental rheometric investigation is performed to assess the utility of various gelation point determination methodologies. Controlled shear stress and controlled shear rate methods are developed to investigate gelation processes in waxy oils. The nonoscillatory rheological method exhibits high reproducibility for model wax oils as well as for real crude oils. In addition, the nonoscillatory methods are in good agreement with standard oscillatory gel point determination methods. The effect of imposed shear stress, imposed shear rate, and cooling rate on gelation point is investigated with two types of model oils: 5 wt % macrocrystalline wax in Primol 352 and 5 wt % macrocrystalline wax in dodecane. In addition, the effect of wax content on gel temperature of macrocrystalline wax in dodecane is investigated. Moreover, the effect of additives (A3 and A4) on gelation point of a real crude oil UL-YS1 is investigated. Finally, the gelation temperatures of 5 wt % macrocrystalline wax in Primol 352, crude...

An experimental investigation of waxy oil gelation behavior is performed using the methods of rheometry, optical analysis, tensiometry, and microscopy. Thermal history, shear history, asphaltene content, and chemical additives influence the gelation process. Consequently, the final gel state is strongly correlated to the gelation conditions. Various model wax–oil systems are prepared, including 5 wt % microcrystalline wax or 5 wt % macrocrystalline wax in dodecane, as well as 5 wt % macrocrystalline wax in Primol 352. Real waxy crude oils UL-YS1 and Se-7-E06 are also investigated. A new yield stress model is developed on the basis of experimental results and a modified Eyring theory to provide gel strength predictions for petroleum transport pipelines. In the absence of shear during gelation, the yield stress can be correlated with the thermal history. However, for non-quiescent gelation conditions, the gel strength is also dependent upon the imposed shear history during the gelation process. The imposed ...

Gelation and breakage of model wax–oil systems is investigated using microscopy, densitometry, rheometry, and XRD. Various model waxy oils are prepared, including 1 to 20 wt % (w/w) macrocrystalline wax in dodecane, 1 to 20 wt % microcrystalline wax in dodecane, and 5 wt % macrocrystalline wax in Primol 352. The influence of shear history, thermal history, and fluid composition is ascertained. A novel gel breakage model is introduced which spans the entire mechanical response of wax gels from initial Hookean behavior at low strains to equilibrium slurry flow at the infinite strain limit. The local rheology model will benefit shut-in and restart processes of waxy crude pipelines via application of standard fluid mechanics relationships.

Fluid characterization is a key technology for success in process design for crude oil mixtures in the future offshore. In the present article modern methods have been developed and optimized for crude oil applications. The focus is on destabilization processes in w/o emulsions, such as creaming/sedimentation and flocculation/coalescence. In our work, the separation technology was based on improvement of current devices to promote coalescence of the emulsified systems. Stabilizing properties based on particles was given special attention. A variety of particles like silica nanoparticles (AEROSIL®), asphalthenes, wax (paraffin) were used. The behavior of these particles and corresponding emulsion systems was determined by use of modern analytical equipment, such as SARA fractionation, NIR, electro-coalescers (determine critical electric field), Langmuir technique, pedant drop technique, TG-QCM, AFM.

The nature of layers formed by cellulose nanofibrils that had been surface modified (hydrophobized) at the oil/water (o/w) interface was investigated. The aim of the study was to clarify the mechanism underlying the excellent ability of these nanoparticles to stabilize emulsions. Layers of hydrophobized nanofibrillated cellulose spread at the o/w interface were deposited on glass slides by the Langmuir-Blodgett deposition technique. Overall evaluation of layer structures was performed by image analysis based on a Quadtree decomposition of images obtained from a flatbed scanner. A more detailed characterization of the layer structures was performed by Atomic Force Microscopy (AFM), and Field-Emission Scanning Electron Microscopy (FE-SEM). The results show that nanofibrils that were able to stabilize emulsions occur as single, dispersed fibrils or form large, network-like aggregates at the o/w interface. Fibrils that were insufficiently hydrophobized and therefore did not stabilize emulsions were only partially deposited and formed small, compact aggregates. We conclude that it is likely that the network formation is the main mechanism by which the fibrils prevent coalescence of emulsion droplets.

Adsorption isotherms of single and double chain cationic surfactants with different chain length (cetyltrimethyl-, didodecyl- and dihexadecyl ammonium bromide) onto cellulose nanofibrils were determined. Nanofibrillated cellulose, also known as microfibrillated cellulose (MFC), with varying contents of carboxyl groups (different surface charge) was prepared by TEMPO-mediated oxidation followed by mechanical fibrillation. The fibril charge was characterized by potentiometric and conductometric titration. Surfactant adsorption was verified by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). Wetting and adhesion of water onto fibril films was determined by contact angle measurements. Small aggregates (admicelles) of surfactant were shown to form on the nanofibril surfaces, well below critical micelle concentrations. The results demonstrate the possibility of using cationic surfactants to systematically control the degree of water wettability of cellulose nanofibrils.

A near-infrared (NIR) scattering technique is used to measure the wax appearance temperature of several petroleum fluids under nonquiescent conditions. Within the Rayleigh scattering limit, NIR attenuation measurements at a wavelength of 1100 nm can theoretically detect wax crystallites

Paraffin wax deposition is a ubiquitous phenomenon in the petroleum production industry. Many types of internal pipe coating materials have previously been tested for preventing wax deposition, but none have demonstrated successful performance. It has become increasingly evident that an improved knowledge of the chemistry and physics of wax deposition will be required in order to develop new wax-repellent materials. In particular, it is important to understand the mechanisms used to inhibit similar deposition problems in outside industries. In order to achieve these objectives, a state-of-the-art literature survey was performed to identify the role and function of nonstick and anti-adhesive surfaces in the food, paint, marine, automotive, biomedical, tribological, optical, and petroleum industries. Information was derived from academic, industrial, and intellectual property sources. This review presents a comprehensive compilation of materials and surface modification techniques that show potential for in...

Paraffin gel formation in sub-sea petroleum transportation pipelines is a common problem encountered during operational and emergency production shut-down periods. Restart of a gelled oil pipeline usually requires the application of a large pressure drop across the pipeline length. In severe cases, permanent wax plugs have formed, resulting in the loss of production capacity. In this investigation, the structural breakdown of a quiescently-formed model wax-oil gel is measured at shear rates ranging from approximately 10−5 sec−1 to 1 sec−1. It is demonstrated that gel breakdown can be mathematically modeled using a time-dependent Bingham equation in which the yield stress follows third order degradation kinetics. The Bingham plastic viscosity term becomes significant at shear rates above ∼10−1 sec−1 and follows a similar third order decay profile with time. When the imposed shear rate is altered in a step-wise manner during the course of the gel breakage, transient non-linear viscoelastic effects are also ...

Alkylsiloxane and perfluoroalkylsiloxane monolayers are prepared on siliceous surfaces using the techniques of Langmuir-Blodgett deposition and solid-liquid chemical adsorption. Acid-catalyzed hydrolysis and polycondensation reactions provide two-dimensional siloxane networks at the liquid-vapor interface, which can be compressed to mean molecular areas of approximately 22 and approximately 32 A(2) for pendent hydrocarbon and fluorocarbon chains, respectively. Subsequent Langmuir-Blodgett transfer onto glass substrates at moderate surface pressures leads to compact monolayers for single-component precursors, while mixed alkyl- and perfluoroalkylsilanes produce nonhomogeneous films characterized by transfer ratios greater than unity. As an alternate monolayer preparation technique, silane polymerization was performed directly on siliceous surfaces via a chemical adsorption mechanism. XPS analysis of a chemically adsorbed 1H,1H,2H,2H-perfluorodecylsiloxane film confirms a single adsorbed monolayer thickness in which the pendent fluoroalkyl chains align nonperpendicularly with respect to the surface. The surface free energy was determined to be 11.4 dyn cm(-1) based on static contact angle measurements. AFM imaging shows the presence of surface defects due to oligomer deposition during the drying process. The use of solubilized trichloro-based silane coupling agents under anhydrous conditions is shown to produce surfaces with a minimal number of surface defects. The presence of undissolved silane material in the bulk solution significantly increases the number of surface defects.

Incipient wax−oil gel deposits form in crude oil transport pipelines when long-chain n-paraffins precipitate at the cold interior surface of the pipe wall. The kinetics of paraffin gel formation was studied using model fluids consisting of monodisperse and polydisperse n-paraffin components dissolved in petroleum mineral oil. Classical homogeneous nucleation theory was applied to investigate the supersaturation conditions necessary for crystal formation. Differential scanning calorimetry was used to monitor paraffin crystallization rates and to provide solid-phase fraction measurements. Gelation occurs when growing n-paraffin crystals interlock and form a volume-spanning crystal network which entrains the remaining liquid oil among the crystals. Paraffin wax−oil gels exhibit a mechanical response to an imposed oscillatory stress, which is characterized by the elastic storage modulus G‘ being greater in magnitude than the viscous loss modulus, G‘ ‘. Low-temperature rheological gels can form from model flui...

Chemical fixation can convert self-assembled amphiphilic aggregates into covalently bonded giant macromolecules that can have properties that are fundamentally different from the unreacted precursors. Following up our previous report, we here extend the comparison between pristine and cross-linked wormlike micelles prepared from a cross-linkable poly(ethylene oxide-b-butadiene) diblock copolymer. Despite retention of the overall morphology, the cross-linked wormlike micelles exhibit unusual linear and nonlinear flow properties that presumably reflect the micelle stiffening upon cross-linking. Chemical fixation also influences their responses to changes in thermodynamic conditions. To explore this point, we added nonadsorbing homo-poly(ethylene oxide) (PEO) into the otherwise stable micelle solutions as a means for creating depletion effects (that is, attractive interactions between the micelles). Experimental studies of the phase behavior and attendant macroscopic properties of the mixtures of the wormlik...

Paraffin wax-oil gels are unique rheological fluids which undergo shear degradation starting at a deformation (shear strain level) of approximately 1%. Flow commencement in pipelines filled with wax-oil gels is a complex hydrodynamic process involving propagation of acoustic, diffusive, and rheological degradation pressure wave fronts. Dynamic simulation informed by qualified rheological relations provides useful insight into the physical nature of these flow processes. Eulerian simulations are presented which emulate known physical phenomena and essential characteristics of wax-gel flow dynamics. A constitutive rheological equation set accounts for deformation-driven reduction in yield stress and viscosity terms. No explicit time-dependent rheological parameters are utilized in the equations. Rheological yielding alters the nature of the dominant pressure wave from inherently diffusive towards self-sharpening. Axial stress localization effectively sequentializes the gel breakage process, quantified by reduced length of the pressure wave-front zone. Ultimately, axial stress localization allows flow in longer pipe segments, albeit with a concomitant time delay. Viscous behavior and yielding degradation behavior are shown to account for upward and downward concavity in transient axial pressure profiles, respectively. Overall, a unique synergy between gel compressibility and gel degradation is revealed. Deformation-coupled interaction between compressibility and degradation allows pressure propagation and subsequent sustained flow through a gel material which is otherwise immobile in the incompressible case.

«Petroleum is a complex mixture of hydrocarbons which is located in the Earth's crust in liquid, gaseous, and solid forms. Natural gas, heavy viscous oil and bitumens are forms of petroleum». This definition provided by а British encyclopedia is somewhat limited. Current scientific knowledge affords a more correct description of petroleum as a system containing numerous hydrocarbon components with different chemical natures. Such a correct definition allows a variety of physical properties and states related to internal structuring.