Oil Rheology Research Articles

Research Status and Prospect of Rheology of Waxy Crude Oil

Research Status and Prospect of Rheology of Waxy Crude Oil

Rheology and electrorheological effects of waxy oils with different carbon number distribution

High-voltage electric treatment is an emerging technology for enhancing the cold flowability of crude oil. The primary mechanism involves the accumulation of charged particles (resins and asphaltenes) onto wax particles under the electric field. This electrorheological effect varies with different oil compositions. We have investigated the impact of resins and asphaltenes on the electrorheological behaviors of waxy oils. However, the impact of the carbon number distribution of wax on this effect remains unexplored. Therefore, the objective of this work is to investigate the interaction between waxes with various carbon numbers and charged particles and its impact on the electrorheological behaviors of waxy oils. Model waxy oils containing distinct wax fractions (paraffin and microcrystalline waxes) and varying charged particle concentrations were prepared and studied. The results unveiled that microcrystalline wax model oils exhibited substantial reductions in viscosity and yield stress after electric treatment, up to 80% and 60%, respectively, surpassing the improvements observed in paraffin wax model oils which were less than 50%. This disparity is attributed to the better capacity of resins and asphaltenes to be eutectic with paraffin wax, improving the original flowability of paraffin wax model oil, thus involving fewer charged particles in the interaction with wax under electric treatment, resulting in a weakened electrorheological effect. Resins and asphaltenes struggle to form eutectic mixtures with microcrystalline wax, resulting in minimal flowability improvement of microcrystalline wax model oils by charged particles. Consequently, under the electric field, a substantial proportion of free resins and asphaltenes can interact with microcrystalline wax particles, leading to superior electrorheological effects in microcrystalline wax model oils.

Adsorption Kinetics and Interfacial Dilatational Rheology of Oil–Water Interfacial Films Loaded with Homogalacturonan and Rhamnogalacturonan-I

Adsorption Kinetics and Interfacial Dilatational Rheology of Oil–Water Interfacial Films Loaded with Homogalacturonan and Rhamnogalacturonan-I

Effect of R/A Mass Ratio on the Rheology of Model Waxy Oils Undoped/Doped with EVA Pour Point Depressant

Effect of R/A Mass Ratio on the Rheology of Model Waxy Oils Undoped/Doped with EVA Pour Point Depressant

Light crude oil rheology under chemical solvents treatment

Abstract This work attempts to study the rheological behavior of Algerian light crude oil from Hassi-Messaoud field with and without chemical solvents in order to improve the flow characteristics. Using the rheometer AR2000, an experimental investigation was conducted to measure the rheological properties via flow test and dynamic mode (oscillation) at various temperatures. Several factors such as temperature (20, 30, and 45 °C), shear rate (between 0.01 and 700 s−1), and solvent concentration (between 2 and 6% of toluene, naphtha, and kerosene) on the rheological parameters have all been studied for this purpose. The statistical parameter standard error (SE) provided justification for the experimental validation of the Herschel-Bulkley model. The results of the flow test showed that these solvents had a significant impact on the flow characteristics of light crude oil at various temperatures, with toluene being the most effective. The viscoelastic properties of crude oil were shown to be considerably influenced by temperature and solvent type, as demonstrated by the dynamic mode study that identified the complex modulus (G*), elastic modulus (G′), and viscous modulus (G″).

Preparation and Performance Evaluation of a New Type of Polyethylene-vinyl Acetate/Polystyrene Microsphere Composite Pour Point Depressant for Waxy Crude Oil.

Polymer/inorganic nanocomposite pour point depressant (PPD) is a research hotspot in the field of waxy crude oil pipelining. However, the inorganic nanoparticles need to be organically modified to improve their organic compatibility, and the inorganic nanoparticles are harmful to crude oil refining. In this work, organic PSMS with an average size of 1.4 μm was first synthesized by dispersion polymerization. Then, a new type of EVA/PSMS composite PPD was prepared by melt blending. The effects of the PSMS, EVA PPD, and composite PPD on the pour point, rheological properties, and wax precipitating properties of a specific waxy crude oil were investigated. It was found that adding 50-200 ppm of PSMS alone slightly improves the crude oil rheology through a spatial hindrance effect, while adding 20 ppm of EVA PPD greatly improves the crude oil rheology by modifying the wax crystal morphology. Compared with EVA PPD, adding 20 ppm composite PPD improves the crude oil rheology further, and the rheological improving ability first enhances and then weakens with increasing the PSMS content in the composite PPD (0-10 wt %). At the PSMS content in the composite PPD 5 wt %, the EVA/PSMS 5% composite PPD makes the wax crystal aggregates more compact, thus showing the strongest rheological improving ability. The EVA molecules could adsorb on the PSMS and form the composite particles, which further regulate the wax crystal morphology and then improve the crude oil rheology further.

Synthesis and application of polyer additive system for reducing the pour point depressant of crude oil in exploitation, transportation

Problems encountered when exploiting and transporting crude oil containing solid paraffins is that it easily crystallizes under normal temperature, causing many challenges such as paraffin wax deposition, reduced flow rate, gel formation, loss of pipe pressure... When the crude oil temperature is below the wax appearance temperature (WAT), paraffin will precipitate and separate from the oil. Many solutions that have been and are being used such as insulation, mechanical, thermal, chemical methods, using wax inhibitors - pour point depressants (PPD) and dispersants... The method of using additives to increase solidification temperature or inhibit wax, improve the rheology of crude oil and reduce paraffin deposition is considered one of the most effective method. In this study, polymers made from a combination of three monomers, behenyl acrylate, stearyl methacrylate and vinyl acetate, were studied to find the most optimal combination for the purpose of manufacturing pour point lowering additives for oils.

Insights into the effect of water content on asphaltene aggregation behavior and crude oil rheology: A molecular dynamics simulation study

In the production and transportation of crude oils, the interaction between asphaltene components and water is inevitable, significantly impacting asphaltene aggregation, deposition behaviors, emulsion stability, and rheological properties of crude oils. However, the comprehension of the oil-water interaction mechanisms and corresponding viscosity responses remains unclear. Hence, we performed molecular dynamics (MD) simulations to investigate the effect of varying water content on distinct asphaltene aggregation states and the rheological behavior of crude oils. The microscopic mechanisms underlying the aggregation and rheological properties were elucidated. Our MD results show that with the continuous introduction of water, the original bulk phase aggregation of asphaltenes undergoes a transition towards interfacial adsorption behavior, culminating in the formation of water-in-crude oil emulsions. The strength and driving forces of this interfacial adsorption are influenced by different polar functional groups of asphaltene. Besides, by elucidating the contributions of external molecular friction and internal structural deformation to the viscosity, two viscosity-influencing mechanisms are revealed. Furthermore, we delineate a physical viscosity scheme. These intriguing discoveries hold promise for advancing the comprehension of rheological behavior in crude oils with distinct aggregation states, providing theoretical guidance for efficient development of crude oils.

Numerical and experimental investigation on ball motion with oil rheology and thermal effect in high speed ball bearings

Dynamic behavior of rolling elements determines the performance including the extent of skidding and wear in ball bearings, which are influenced by many factors. A comprehensive investigation of dynamic behaviors of high speed ball bearings has been conducted both numerically and experimentally. The dynamic model of high speed ball bearings applicable to a wide range of shaft speeds has been developed, taking into account rheological behavior of lubricating oil, curvature effect, collision between balls and cage and thermal effect. Analyses of ball speeds and interaction forces, as well as sliding speed within ball-raceway contact ellipse have been carried out. The ball-to-race ratio (BRR) of speed has been studied specifically under various operating conditions to reflect the cage speed with high precision. A set of experiments have accordingly been performed on a test rig where optic fiber transducer was employed to obtain the orbital speed of ball. The increase of orbital speed of ball with shaft speed was observed in experiments under different axial load. Numerical results from dynamic simulations also agree with the experimental results based on the investigated ball bearing. The present model is versatile over a wide range of operating conditions.

Experimental study on the influence of asphaltenes with small dosage on the rheological and gelation behavior of waxy mixtures

Asphaltene, the heaviest and most polar non-hydrocarbon component in crude oil, may interact with waxes and affect the flow and gelation behavior of waxy oils. To further study the effect of asphaltene on the flow and gelation behavior of waxy oils, five wax-containing simulated oils with small dosage asphaltene content were prepared. Through pour point and rheometer test, it is found that asphaltenes can improve the low-temperature rheology of waxy oil. There is no critical turning point above which the low-temperature flowability improved. With an increase in asphaltene content from 0 wt% to 0.1 wt%, notable changes were observed in the properties of the waxy oil. The pour point, which measures the temperature at which the oil becomes too viscous to flow freely, exhibited a decrease from 25 ℃ to 13 ℃. Similarly, the gelation temperature, indicating the temperature at which the oil starts forming a gel-like consistency, also decreased from 29.0 ℃ to 27.1 ℃. These modifications can be attributed to the presence of asphaltene in the oil sample. This outcome can be attributed to the interference caused by the presence of asphaltenes, which disrupts the gel network structure of the waxy oil and consequently hinders its gelation process. Simultaneously, within the low asphaltene content range, an increase in asphaltene content resulted in a considerable decrease in the viscosity of the waxy oil at 10 °C, reducing it from 531.5 mPa s to 14 mPa s.

The Contrasting Behavior of Strongly and Weakly Interfacially Active Asphaltenes on the Rheology of Model Waxy Oils

The Contrasting Behavior of Strongly and Weakly Interfacially Active Asphaltenes on the Rheology of Model Waxy Oils

A mechanistic study of the synergistic and counter effects of ultrasonic and solvent treatment on the rheology and asphaltene structure of heavy crude oil

Production from heavy oil reservoirs faces challenges, such as accumulating heavy hydrocarbon materials like asphaltenes near the wellbore, resulting in low recovery rates. To enhance recovery and prevent formation damage, methods often focus on reducing oil viscosity. Solvents and ultrasonic waves have proven effective in this regard, though challenges related to asphaltene aggregation and structural changes persist. This study explores the impact of simultaneously applying ultrasonic radiation and solvents on crude oil's viscosity and asphaltene structure. Toluene and n-heptane, representing aromatic and paraffinic solvents, were employed. Viscosity measurements and Fourier transform infrared spectroscopy tests were conducted on sonicated crude oil diluted with solvents and solvent-diluted crude oil subjected to sonication. Results were compared to untreated and separately treated crude oil samples. The study found that the most effective viscosity reduction method involved blending sonicated oil with toluene under optimal radiation time and concentration conditions. Two primary mechanisms for viscosity reduction were identified. Firstly, there was the dissolution and aggregation of asphaltene clusters. Secondly, chemical changes in asphaltene molecular structure were observed, altering the ratio of aromatic rings to aliphatic chains. This research offers potential insights into how ultrasonication and solvation interact to modify crude oil structure.

Study on the influence mechanism of asphaltenes on the gelation and flow behavior of wax-containing simulated oils

The precipitation of wax crystals will lead to the formation of gelation structures in waxy crude oils, and the presence of asphaltenes will affect the gelation and flow process of waxy crude oils. In this work, five waxy oils with different asphaltene contents were formulated, and the effect of asphaltene on the gelation and flow behavior of wax-containing simulated oils was investigated. The results show that asphaltenes can improve the low-temperature rheology of wax-containing simulated oils to a certain extent. When the asphaltene contents in wax-containing simulated oils increased from 0 wt% to 0.5 wt%, the pour points decreased from 25 °C to below 0 °C, while the gelation temperatures and storage modulus were also decreased from the initial 29.01 °C to 25.64 °C and 33262 Pa to 5.9 Pa, respectively. The results were due to the fact that the increase of asphaltene contents weakened the gelation network structure strength of wax-containing simulated oils and inhibited gelation process. Meanwhile, in the range of low asphaltene contents, the apparent viscosity of wax-containing simulated oils at 10 °C decreased from 531.5 mPa·s to 7.6 mPa·s with the increase of asphaltene contents.

Influence of Various Nanomaterials on the Rheology and Hydration Kinetics of Oil Well Cement.

Nanomaterials have great potential to influence the properties of cement-based materials due to their small particle size and large specific surface area. The influences of Nano-SiO2 (NS), gamma-nano-Al2O3 (GNA), alpha-nano-Al2O3 (ANA), and nano-TiO2 (NT) on the rheology and hydration kinetics of class G cement at 30 °C were investigated in this study. The nanomaterials were added in dry powder form at dosages of 1, 2, 3, 5, and 7% by weight of cement (bwoc), and their dispersion was accomplished using polycarboxylate superplasticizer (PCE) at a dosage of 1.6% bwoc. PCE provides a uniform dispersion of nanoparticles in the cement matrix, enhancing the efficiency of nanomaterials. The w/c ratio varied between 0.718 and 0.78 to form a constant-density slurry of 1.65 g/cm3. Our test results showed that NS and GNA caused significant increases in the rheology of the cement slurry, with this effect increasing with dosage, while ANA and NT tended to reduce the rheology of the slurry. Compared to a well-suspended and well-dispersed cement slurry generated by the use of PCE and diutan gum, all nanomaterials can accelerate early hydration by reducing the induction time, with GNA having the strongest influence, while NS was the only nanomaterial that further increased the long-term hydration heat release at 7 days. The stronger effect of NS and GNA on the cement slurry properties can be attributed to their higher chemical reactivity. The dosage effect on total hydration extent was relatively strong for ANA, NT, and NS from 3% to 5% but weak for GNA in the range from 3% to 7%.

Wax appearance temperature under shear in methane-saturated mineral oil + paraffin wax mixtures: Effects of concentration and pressure

Increasing oil production from cold environments, such as offshore deep-water, has resulted in flow assurance issues due to wax deposition and hydrate formation. Understanding of the high-pressure flow properties of waxy oils is important to minimize blockages and related issues. However, the effect of pressure on wax appearance temperature (WAT) and viscosity of waxy oils is not widely studied due to the challenges of high-pressure rheology experiments. Here, a model waxy oil system was investigated using a high-pressure rheology from 0 to 1400 psig at 100 s−1. The focus was on paraffin wax in heavy mineral oil, and we examined wax concentrations of 5, 10, 15, and 20 wt%. First, waxy oils were saturated in methane, and then, temperature was decreased until wax appearance occurred. The findings revealed that wax concentration has a larger effect on WAT than pressure. At a constant pressure of 0 psig, WAT increases up to 13 °C when wax concentration increases from 5 to 20 wt%. Increasing pressure from 0 to 1400 psig results in up to 6 °C depression in wax appearance temperature for 20 wt% wax. The findings of the current study contribute to addressing flow assurance challenges in cold environments by enhancing the understanding of waxy oil rheology under methane-saturated, high-pressure conditions.

Numerical Study: Comparison of Paraffin Deposition In The Laminar And Turbulent Regime

The problem of paraffin deposits in oil wells and pipelines monopolizes substantial human and economic resources. Its prediction is, therefore, essential to optimize its management. The formation of the deposit arises from a delicate interplay of hydrodynamic, thermal, and thermodynamic factors, alongside paraffin diffusion and the rheology of the crude oil. This research has resulted in a better understanding and calculation of the rates at which wax is removed. Furthermore, the study has suggested the presence of two distinct flowing regions in turbulent and laminar flow, which results in the formation of thin solid sediments attached to the pipe wall.By conducting this numerical study using FORTRAN, we can gain insights and optimize the design and operation of pipelines and maintain efficient production. The study also involved a rough comparison between the results obtained from two different types of flow. This approach, which considers the viscoelastic behavior of paraffinic crude, allows for a more accurate prediction of deposit formation. With this enhanced understanding, we can develop improved strategies for managing paraffin build-up, minimizing resource allocation and costs associated with its removal. Ultimately, optimizing the design and operation of pipelines will contribute to the maintenance of efficient production in the oil industry.

A review of nanoparticles and their composites as pour point depressant for waxy crude oil

Adding pour point depressant is an important method to solve the poor low temperature rheology of waxy crude oil. Although the traditional polymer pour point depressant has good improvement effect, it has some problems, such as poor resistance to repeated heating and shear. Therefore, nanoparticles are widely used to improve the rheology of crude oil. Although nanoparticles have a certain influence on the improvement of low-temperature rheology, and nanocomposite particles have better improvement effect than single polymer pour point depressant, no one has combed and summarized the influence mechanism of nanoparticles and their composites. This paper introduces three kinds of nanoparticles and their composite materials, briefly describes the performance of the influence of various nanoparticles and their composite particles on the rheology of waxy crude oil, and analyzes the mechanism of their influence on the rheology of waxy crude oil. The analysis of this paper shows that the influence and mechanism of individual nanoparticles on the rheology of crude oil are different due to their different properties. All nanocomposite particles meet the heterogeneous nucleation mechanism, and the polar group of nanocomposite particles is an important factor affecting the effect of nanocomposite particles. Carbon based nanoparticles, especially graphene oxide, promise important research prospect.

Effect of a novel type of water-in-oil nanocomposite viscosity improver on rheological properties of crude oil

The waxy crude oil was routinely transported by means of adding pour point depressants (PPD), which can significantly improve the flow behavior of waxy crude oil. In this study, the physical properties of crude oil were first characterized. Subsequently, a novel variety of W/O nanoemulsion was prepared based on water in an EVA/toluene solution at a 3:1 proportion, and evaluated as a viscosity improver. It was found by virtue of the laser particle size analyzer that the EVA emulsion reaches the nano-scale. EVA nanoemulsion can present a behavior similar to nanocomposite PPD, and form a denser and regular structure with wax crystals via heterogeneous nucleation. Compared with conventional EVA, EVA nanoemulsion further reduces the oil viscosity, gel point and yield value by 52.8%, 0.05 °C and 29.6%. In addition, the impact of particle size of EVA nanoemulsion on the rheology of crude oil was discussed. In combination with DSC curve and POM, the action mechanism of EVA nanoemulsion on crude oil was analyzed.

Application of Bio-Derived Alternatives for the Assured Flow of Waxy Crude Oil: A Review

High molecular weight paraffin/wax precipitates in the solution of crude oil when the surrounding temperature falls below the wax appearance temperature, which causes the problem of wax deposition in pipelines. To enhance the rheology of the crude oil and lessen wax deposition, pour point depressants (PPDs) and flow enhancers were utilized. These substances change the wax crystals’ morphology, reducing crystal interlocking and preventing wax agglomeration from facilitating wax dispersion. However, recent research prompted a further investigation to improve the performance of conventional polymeric PPD and to address wax accumulation in a safe and environmentally responsible way. This is because of their poor performance at high shearing, expensive preparations, limited biodegradability, and toxicity. The primary objective of this study is to provide a thorough summary of current studies on the use of seed oil extracts rich in unsaturated fatty acids as an alternative for polymeric PPD. Important studies on the use of nanoparticles to improve the performance of conventional PPD, as well as strategies put into place to overcome issues with nanoparticle application, are also highlighted. Finally, an outlook of potential research ideas to develop pour point depressants is provided.

A synergistic effect of zinc oxide nanoparticles and polyethylene butene improving the rheology of waxy crude oil

This research examined the use of 75 nm zinc oxide nanoparticles (nano ZnO) and polyethylene butene (PEB) to decrease the viscosity of Nigerian waxy crude oil. The rheology of the crude oil was assessed by measuring the viscosity and shear stress of samples containing PEB at 500, 1000, 2000, 3000, 4000 or 5000 ppm and nano ZnO at 1, 2, 3 or 4 wt% between 10 and 35 °C at shear rates from 1.7 to 1020 s−1. Rheological modeling indicated that a power law pseudoplastic model was the best fit for the experimental data, giving a regression coefficient of 0.99. The addition of these inhibitors induced Newtonian fluid behavior in the crude samples such that the shear stress-shear rate relationship plots were linear at all temperatures. The optimum concentrations of the inhibitors in this study were 2000 ppm PEB (providing a 33% viscosity reduction) and 1 wt% nano ZnO (providing a 26% viscosity reduction). A combination of these additives at these concentrations provided a synergistic effect and gave a greater viscosity reduction of 41%. This work demonstrates that a blend of ZnO nanoparticles and PEB can improve the flowability of waxy crude.