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Abstract The effect of orbital motion of drill pipe on the transport of non-Newtonian fluid and cuttings is simulated by means of the two-fluid model in combination with the kinetic theory of granular flow in the horizontal wellbore annulus. The drill pipe self-rotates around its own axis while pursuing a circular orbit around the axis of the wellbore annulus, in which the orbital radius is the eccentric distance of the drill pipe from the axis of the wellbore. The embedded sliding mesh method is adopted to achieve the effect of the orbital movement of the drill pipe wall on the liquid-solid mixture. The cuttings transport ratio (CTR) which is defined as the ratio of the concentration of injected cuttings to the concentration of cuttings retained in the annulus is chosen as the measurement to evaluate hole cleaning. Cuttings transport behaviors in the annuli with the four motion states of drill pipe are investigated respectively. Simulations indicate that if the drill pipe is not concentric, there must be the fluid force that causes the lateral movement of drill pipe when it rotates. The orbital motion of drill pipe improves cuttings transport ratio in the annulus due to the periodical stirring and entrainment effect on cutting particles. The tangential flow within the annulus is dominated by the orbital motion of drill pipe rather than the self-rotation. The secondary flow appears especially when the self-rotation and orbital motion of drill pipe are in the opposite direction. With the increase of the orbital radius, the cuttings transport ratio is improved and the pressure drop is reduced because of the agitation of the drill string against the flow field. Increasing the rotating speed of the drill pipe contributes to a better wellbore cleaning, while an excessive rotating speed causes a higher pressure drop. Although the orbital motion of the drill pipe improves the hole cleaning, it also greatly increases the resistance and resultant moment exerted by the liquid-solid mixture, especially at high rotation speeds and eccentricity ratios. Graphical abstract Image 1 Highlights • Cuttings transport in annuli with four motion states of drill pipe were studied. • The orbital motion of drill pipe improves cuttings transport in drilling annulus. • Effects of rotation speeds and eccentricity ratios of orbiting pipe were studied. • Orbital motion of drill pipe plays the dominant role in tangential flow in annulus. • Orbital motion significantly increases the resultant moment on the drill pipe. [ABSTRACT FROM AUTHOR]

Abstract In order to investigate hydrodynamic characteristics of Bingham porous-flow mechanics in a heavy oil reservoir, this paper originally proposes a physical model of Bingham fluid flow for a horizontal well in a heavy oil reservoir. A corresponding mathematical model is established and solved. A series of typical pressure and pressure derivative curves are drawn by the use of the semi-analytical solution of the mathematical model. Hydrodynamic flow characteristics of Bingham fluid are thoroughly analyzed. Through the recognition of flow regimes from the typical curves, it is found that the flow process of Bingham fluid mainly includes the early radial flow regime, linear flow regime and late pseudo-radial flow regime. The curves controlled by different boundary conditions are especially studied, and it is found that the late curve shape, especially the shape of pressure derivative curve, differs completely for the various property of boundary. The curve sensitivity to different model parameters, such as dimensionless threshold pressure gradient and horizontal wellbore length, is deeply discussed. The findings are as follow: except the pure wellbore storage regime, the threshold pressure gradient influences the hydrodynamic flow behavior in all the regimes; the curve of Bingham fluid governed by the threshold pressure gradient upward deviates from that of Newtonian fluid; and the deviation of the curves increases with the increase of the threshold pressure gradient and the elapsed time. The research results of this paper sufficiently demonstrate the essential property of non-Newtonian porous-flow mechanics. Highlights • A new porous flow model of Bingham fluid for horizontal well production was originally investigated. • The viscous, plastic and slightly elastic properties of Bingham fluid in a heavy oil reservoir were considered in the model. • The hydrodynamic behavior of Bingham fluid was modeled and the typical flow characteristics were thoroughly analyzed. • A series of pressure dynamic curves controlled by model parameters were created and studied. • The influence of the threshold pressure gradient on the Bingham flow traits was deeply discussed. [ABSTRACT FROM AUTHOR]

Aqueous foams are used in many oil field applications including drilling, fracturing, and enhanced oil recovery operations. The success of all these operations strongly depends on viscosity and stability of foam. Rheology of foams is a function of foam quality (i.e. gas volume fraction), liquid phase viscosity, pressure, and temperature. Besides, foam generation method and stability are factors that influence its rheology. This article presents results of an experimental study performed to investigate the effects of foam quality, pressure, and wall slip on aqueous-foam rheology. Extensive tests were conducted using a foam recirculating flow loop consisting of three pipe viscometers. Experiments were performed at ambient temperature, and varying pressure (6.89–20.68 MPa), foam quality (40–80%), and pipe diameter (3.06, 6.22 and 12.67 mm). The foam was generated by passing a mixture of water containing 2% surfactant solution and gas phase (nitrogen) through a needle valve. To minimize degradation while testing, the foam was regenerated by circulating at the maximum flow rate (0.55 L/min) before each flow measurement was made. Results indicate strong non-Newtonian behavior of foam, which closely fits the power law model. For foams with more than 55% quality, measured viscosities were higher than the ones reported in the literature. Noticeable wall slip was not observed. Foam viscosity change because of pressure variation at a constant foam quality was negligible. Foams with quality higher than 70% exhibited yield pseudoplastic behavior. Their rheological behavior can be described better by Herschel–Bulkley model than power law model when the shear rate is below 20 1/s. [ABSTRACT FROM AUTHOR]

The cuttings transport during well drilling was numerically simulated based on kinetic theory of granular flow in combination with sliding mesh for drill pipe rotation. The power-law model was implemented to describe the rheological behavior of drilling fluid. Numerical results were compared with available experimental data in the literature to validate the algorithm, and good agreement was found. Three distinguishable regions of cuttings flow pattern and swaying phenomenon of cuttings distribution were observed along the direction of drill pipe rotation. Increasing the fluid velocity results in a reduction in the height of cuttings bed and weakening of the swaying phenomenon. Higher apparent viscosity of drilling fluid contributes to a good performance of cuttings transport at a low annular velocity, but rising in pressure loss. There is critical inclination angle of the well θ ctr for cuttings transport ratio and θ dp for pressure drop through the annulus. The most difficult of cuttings transport occurs in the well inclinations around 35°–65°. There is no additional contribution of drill pipe rotation to cuttings transport after reaching a critical rotation speed. Increasing the cutting size leads to a reduction in the cuttings transport ratio and an increase in pressure drop. [ABSTRACT FROM AUTHOR]

Non-Newtonian fluids are widely applied in Enhanced Oil Recovery (EOR) techniques, and the good performances have been ascribed to the shear-thinning or shear-thickening characteristics of them. In this paper, we aim at discovering the roles of these rheological properties in non-Newtonian fluid displacement from the pore scale. A recently developed lattice Boltzmann model (LBM) for multiphase viscoplastic fluid flow [Xie et al. J Non-Newton Fluid, 2016. 234 : 118–128] is used. Displacements in both homogeneous and heterogeneous porous media are considered. For homogeneous cases, the performances of shear-thinning and shear-thickening fluids are almost the same when compared in favorable displacement regime; while the performance of shear-thinning fluid is poorer than that of shear-thickening fluid in unfavorable displacement regime. For heterogeneous cases, we demonstrate that the shear-thinning property does not contribute too much to the diversion effect, which clarifies the debate of understandings. Our pore-scale modeling results also indicate the significance of low viscosity ratio for diversion and EOR, which can stabilize the displacing front despite of the increased viscous resistance. [ABSTRACT FROM AUTHOR]

Wax deposition in production pipelines causes flow assurance issue due to reduction in flow rate. Gelling of waxy crude oil after subsequent cooling restricts the flow and causes blockage in pipelines, and thus requiring large and costly pumps to restart and regain the steady flow. Nevertheless, the formation of intra-gel voids in the gel was recently reported to ease restart pumping. Further, it is believed that injecting non-reacting gas into the production lines prior to or during shut down could alleviate the restart flow problem and save costs. An experimental work was conducted in order to manipulate the effectiveness of such approach. A flow loop rig was used to simulate the conditions of waxy crude oil in pipelines on seabed and a gas injection system was used to inject nitrogen into the system after crude oil stopped flowing, prior to gelation process. Restart pressure was applied in two modes: instantaneous and gradual pumping. It was observed that maximum restart pressure reductions of 11.48% and 17.44% were achieved when pressure was applied instantaneously and gradually, respectively. It was found that the restart pressure decreased as the gas to oil volume ratio increased due to high slippage effect. In addition, restart pressure under gradual restart approach was observed to be higher than that for instantaneous restart approach. [ABSTRACT FROM AUTHOR]

Due to many biological and technical applications, including microelectronics, heat exchangers, cancer therapy, process industries, solar collectors and power production, researchers have been more interested in the mechanism of heat transfer involving nanomaterials. A contemporary method to increase the thermal conductivity of various cooling fluids is the use of nanomaterials. Many researches suggest that the thermal conductivity of nanoliquids; solid nanoparticles combined with a base fluid, is expressively greater than that of conventional fluids. This work presents the theoretical investigation of magnetohydrodynamic stagnation point flow of non-Newtonian nanofluid flow past flat plate. The applications of solar radiation towards water-based copper nanoparticles are highlighted in this study. The system of PDEs is transmuted into the system of ODEs by mean of suitable similarity variable. Analytical solution of the present analysis has been performed with the help of HAM technique. The impacts of physical factors on the flow profiles, skin friction coefficient, heat, and mass transfer rates are calculated. It is significant to note that the default concentration is weighted by 4% throughout this analysis. Also in this analysis, we examined the temperature and heat transfer rate for the presence and absence of solar radiation. It is found that the greater nanoparticles volume fraction of the water-based copper nanoparticles has accelerated the flow profiles for the absence of magnetic field. However, for the presence of strong magnetic field, the velocity, and temperature of the water-based copper nanoparticles have significantly reduced. Due to the incidence of Lorentz force, the velocity of the water-based copper nanoparticles has deteriorated, while the temperature profile has augmented. It is found that the solar radiation has always dominant impression on temperature of the water based copper nanoparticles. • This work presents the theoretical investigation of magnetohydrodynamic stagnation point flow of non-Newtonian nanofluid flow past a flat plate. • The applications of solar radiation towards water-based copper nanoparticles are highlighted in this study. • We examined the temperature and heat transfer rate for the presence and absence of solar radiation. • It is found that the greater nanoparticles volume fraction of the water-based copper nanoparticles have accelerated the flow profiles in the absence of a magnetic field. [ABSTRACT FROM AUTHOR]

In this paper, hydrodynamic of drilling mud and cuttings in a vertical well has been studied numerically. For solid–liquid two-phase flow simulation, the mixture model including continuity and momentum equations was used. To describe the rheological behavior of drilling mud, Herschel Bulky model was implemented. Then, a numerical code was developed to calculate flow field parameters (i.e. liquid phase velocity components, solid phase volume fraction, and solid phase velocity components in the annulus) and pressure drop. The results have been compared with available data in the literature and good agreement was found. Moving mud at entrance of the annulus and developed flow length were studied and pressure drop was calculated. Annular flow velocities in this study varied from 0.4 to 1.4 m/s. Then the effects of velocity, fluid type, pipe rotation, drilling cuttings and eccentricity on pressure drop were investigated. The pressure drop in the annulus increased while eccentricity and rotation of drill pipe increased. Rotation of the drill pipe shifts maximum fluid velocity location toward cornel space of the concentric annulus. After ensuring the accuracy of the simulation, the effects of drilling mud type, mud axial velocity, drilling rotation, fluid density and cuttings size on cuttings transport were studied. Finally, mud capacity for keeping cuttings was calculated in stasis. Then, with considering shape factor for cuttings, the velocity profile of cuttings, the mud capacity of the drilling flow and slip velocity were calculated. Slip velocity profile of cuttings in the annulus increased as cutting size increased. This indicates that cutting transport in the annulus enhances as velocity, mud density, viscosity and rotation of drill pipe increase. Eccentricity and cutting size have a negative effect on cutting transport. [ABSTRACT FROM AUTHOR]

In directional drilling, the annulus is often eccentric and the eccentricity may vary along the well, due to the column weight and drilling conditions oscillations. Furthermore, by the gravitational effect, there will be a strong tendency for accumulation of solids at the lower part of the annulus, forming a settled cuttings bed that partially obstructs the flow, which may hinder or even stop the drilling process. It is important to study the flow patterns for these conditions, which have not been greatly discussed in the literature. The aim of this work is to evaluate experimentally and through numerical simulations, the laminar and isothermal helical flow of non-Newtonian fluids into horizontal annular sections with partial obstruction, and to analyze the effect of the orbital motion of the inner tube for the eccentric annulus. A pilot unit at the laboratory scale was used for the acquisition of data regarding hydrodynamic losses at atmospheric conditions (pressure and temperature) considering the system geometry (eccentricity), mass flow rate, fluid rheology (Xanthan Gum concentration) and rotation of the inner cylinder. Techniques of computational fluid dynamics (CFD) were also applied to obtain detailed information about the flow field, simulated in fully developed flow conditions. [ABSTRACT FROM AUTHOR]

Vertical vibrations in drilling (chatter) can be reduced by the viscous damping associated with the mud rheology. In previous studies, the effect of damping was modelled assuming that the drilling fluid is Newtonian. However, non-Newtonian shear-thinning muds are beneficial for the drilling process. In this study, we investigate the influence of the non-Newtonian mud rheology on the vertical drill bit vibrations using two different non-Newtonian rheology models: Herschel-Bulkley and Casson. In modelling the vibrations, we assume that the stiffness of the rock is much greater than the stiffness of the drill string, which corresponds to deep boreholes. This allows the use of the concept of impact oscillator, whereby the rock stiffness is assumed infinite, such that the vertical oscillations are associated with the drill bit detachment. The driving force for the oscillations is the periodic drill bit bouncing caused by impact of the roughness of the borehole floor. Parameters of the rheology models required for the efficient reduction of chatter have been determined. It has been established that with the muds used currently in the industry, a significant reduction of chatter cannot be achieved. Furthermore, the desirability of the shear-thinning behaviour in muds might limit the scope for a vibration-damping mud design. [ABSTRACT FROM AUTHOR]

Rock formation is subjected to acid stimulation to increase oil reservoirs productivity. Acidizing of sandstone rocks is a common method to remove damage and recover the oil flow to the wellbore. A matrix acid stimulation will always require additives depending on mud acid (HF/HCl) components, which cause non-Newtonian fluid behavior. In this study, the 3-D mathematical model of sandstone matrix acidizing in radial flow has been presented by a modified two-parameter model to consider non-Newtonian fluids and temperature effects. To this end, the Carreau-Yasuda equation has been employed to predict dissolution patterns created by non-Newtonian reactive fluids in sandstone formations. Meanwhile, the energy equation has been solved in the porous media to estimate the temperature in each time step, which affects the dissolution patterns in matrix acidizing. Three main phenomena are involved in dissolution patterns: surface reaction, diffusion and convection. Acidizing simulation indicates the acid-rock reaction constant in the formation network is temperature sensitive, and increases exponentially by increasing the reservoir temperature. In this work, the effects of various heterogeneity magnitude and porosity in the porous media, injection rate, reaction rate constant, power-law index (n) and temperature are considered by the various presented dissolution patterns of sandstone acidizing. The results show that, to reach a certain penetration length, the pore volume (P V) of injected acid decreases sharply with reservoir temperature, but after the critical temperature, it decreases slowly. The model discretized the Darcy, mass and energy balance equations by finite difference method and pore evaluation by Karman-Cozney correlations, and then employed the Tri-Diagonal matrix algorithm (TDMA) method to achieve the solution of the model and analysis of dissolution patterns in various acidizing regimes and rheological properties. All mathematical estimations including Darcy correlations, mass and energy balance and pore evaluation have been solved in FORTRAN program by parallel processing to accelerate 3-D calculations. • Simultaneous numerical solution of Darcy, energy, mass and pore equations in 3-dimension. • 3-D modelling of sandstone matrix acidizing by non-Newtonian fluid and temperature effects. • Pore volume, permeability and effluent concentration calculations in various conditions. • Consideration of power-law index (n) and flow rheological effects in dissolution patterns. • Consideration of temperature gradient effect in penetration length. [ABSTRACT FROM AUTHOR]

Matrix acidizing is a common technique to increase oil recovery in sandstone oil reservoirs. In the matrix acidizing process, reactive fluids are injected into the reservoir with the scope of dissolving and dispersing the rocks near the wellbore.In this study, the matrix acidizing of sandstone wells by a hydrochloric acid/hydrofluoric acid/additives mixture is described through mathematical modeling using the two-scale continuum model.The model developed in this study indicates the reactions and transport phenomena at pore and Darcy scales in 3-D radial flow. Due to using several additives during the acid injection process, the fluid phase has non-Newtonian behavior (shear-thinning). The effect of non-Newtonian fluid in porous media was investigated using a modified continuum model due to importance calculations in field scale. The Carreau-Yasuda constitutive equation has been used to modify the continuum model to consider the non-Newtonian fluid effects. In the proposed model, partial differential equations of reaction and diffusion at pore-scale, and simultaneously convection and dispersion phenomena at Darcy scale are solved using numerical methods. The finite volume and tri-diagonal matrix algorithm (TDMA) techniques were employed to gain a precise solution for the model and observe the dissolution pattern in different acidizing regimes and rheological properties. The effect of acid injection rate, dissolution rate constant and different reservoir properties, including permeability, porosity and heterogeneity on dissolution patterns, was investigated by considering non-Newtonian fluid effects, and concluded that acid having high shear-thinning behaviour (i. e., acid having low power-law index) seemed more promising for field operations because of deep penetration. The reservoir heterogeneity was defined by selecting a random local porosity distribution.It should be noted that the presented model can reproduce different types of acid/rock system (carbonate or sandstone reservoirs). Finally, the skin factor would be calculated to study the acidizing performance in the damaged zone. To solve the porosity evolution equation, couple pore and Darcy scales, and update the pore-scale parameters at each time step, the program was developed in FORTRAN by Parallel Processing and consisting of functions and routines. • Simultaneous numerical solution of Darcy, mass and pore equations in 3-dimension. • 3-D modeling of sandstone matrix acidizing by non-Newtonian fluid. • Pore volume to breakthrough and injection rate calculations in various conditions. • Consideration of power-law index (n) and viscosity effects in dissolution patterns. • Consideration of skin factor variation during the matrix acidizing. [ABSTRACT FROM AUTHOR]

Abstract: A study on thermal effects of the suction/injection Reynolds number, in conjunction with other flow parameters, on an unsteady reactive temperature dependent viscosity third grade fluid in a porous channel filled with saturated porous medium is presented. It is assumed that the channel walls are subjected to asymmetric convective heat exchange with the surrounding medium and that exothermic chemical reactions take place within the flow system. The heat exchange with the ambient at the surfaces is assumed to obey Newton's law of cooling. The equations governing the flow system are expressed in non-dimensional form and a semi-implicit finite difference scheme is utilised to obtain the velocity and temperature profiles. The effects of the flow parameters on the temperature and velocity fields, the skin friction and the wall heat transfer rate are simulated and discussed. The suction/injection Reynolds number is observed to retard the velocity field. It is also observed that the suction/injection Reynolds number, the porous medium parameter, the Prandtl number and the Biot number have a retarding effect on the temperature field. The variable viscosity parameter and the suction injection Reynolds number increases the skin friction while the porous medium parameter and the Prandtl number diminish it. It is also revealed that the suction injection Reynolds number, the porous medium parameter and the Prandtl number have a diminishing effect on the rate of heat transfer at the channel walls. [Copyright &y& Elsevier]

Global energy demand is rapidly increasing at a rate of 8% between 2004 and 2019, and conventional energy sources are unable to meet this requirement. Therefore, the oil and gas energy industry is working continuously to produce unconventional energy sources such as deepwater oil and gas reservoirs, gas hydrates, and geothermal energy using drilling operations. In the drilled borehole, the stability and integrity issues are encountered that are related to pressure differential generated by the Couette-Poiseuille (CP) fluid flow phenomenon occurred during pipe tripping operation. There is a lack of experimental data to comprehend the impact of CP flow on pressure differential using non-Newtonian fluid in concentric and eccentric annuli, especially in petroleum exploration. Hence, an experimental investigation is performed to replicate the tripping operations during oil and gas well drilling. The investigation provides an extensive understanding of the physical and mechanical characteristics of non-Newtonian fluids under CP flow at varying inner pipe tripping speeds (0.030481–0.21336 m/s), rheological properties, and geometrical dimensions. The results indicate that surge/swab pressure gradient tends to decrease with increasing eccentricity (ε) and increase with increasing diameter ratio (δ) and pipe tripping speed (V p). Furthermore, the pressure differential rate is considerably high at low tripping speed but reduces at high pipe tripping speed due to the shear-thinning behavior of YPL fluid. The study also reveals that gel strength increases the surge/swab pressure gradient by approximately 18%. A multi-variable correlation is developed to predict surge/swab pressure gradient, exhibiting an excellent agreement with experimental data and existing theoretical models. • Experimental investigation of surge/swab pressure effect on petroleum energy exploration. • Effect of CP flow on surge pressure gradient under varying geometrical and rheological parameters. • New correlation is developed to predict surge pressure gradient. [ABSTRACT FROM AUTHOR]

Many fluids used in petroleum and chemical industries are generally described as complex systems that exhibit time-independent non-Newtonian behavior. To adequately represent the rheological behavior of an oil-tolerant and salt-resistant aqueous foam system, a Carreau-Extended (Carreau-E) rheological model, which includes a yield stress, a shear-thinning parameter and a time constant, has been established based on Carreau and Herschel-Bulkley models. In the present study, generalized Reynolds number definitions are proposed for laminar and fully developed pipe flow of non-Newtonian fluids (Carreau-E, Carreau, Herschel-Bulkley and Bingham fluids). Perturbation solutions for pipe flow of a Carreau-E fluid are obtained and their ranges of validity in the problem parameter space are identified. The quantitative effects of rheological parameters (e.g., yield stress, time constant, shear-thinning parameter) and flow parameters, (e.g., pressure gradient, pipe radius) on the velocity profile and flow rate in pipe flow of a Carreau-E fluid are explored. The results obtained for the flow characteristics can be applied or extended for other types of non-Newtonian fluid flow encountered in practical applications. • Perturbation solution for laminar pipe flow of a Carreau-Extended fluid is derived. • Generalized Reynolds number definitions for four types of non-Newtonian fluids are proposed. • Asymptotic analytical solutions show a good agreement with the numerical solutions. • Quantitative effects of rheological parameters on flow characteristics of a Carreau-E fluid are explored. [ABSTRACT FROM AUTHOR]

Abstract: Network modeling is used to study the flow in porous media of Ellis and Herschel–Bulkley fluids, which model a large group of time-independent non-Newtonian fluids. Previous work is extended to include yield-stress and shear-thickening phenomena. We use two topologically-disordered networks representing a sand pack and Berea sandstone. Analytical expressions for the volumetric flow rate in a single tube are derived and implemented in each pore and throat to simulate single-phase flow in the pore space. An iterative technique is used to compute the relationship between flow rate and pressure gradient across the whole network. The single tube behavior is compared to that of the network. Experimental data in the literature are compared to the network simulation results to validate the model and investigate its predictive capabilities. Good agreement is obtained in many cases. The flow of yield-stress fluids in porous media is analyzed. Two algorithms to predict the network threshold yield pressure are implemented and compared to the numerically computed threshold yield pressure of the network. [Copyright &y& Elsevier]

In this work we present an experimental study of non-Newtonian solid–liquid suspension flow in the annular space of a concentric-pipe system that simulates the geometry of wells during drilling for petroleum exploration and production, excluding effects of drill rotation. The liquids used were solutions of biodegradable guar gum at various concentrations and the solid phase was siliceous sand. We studied how the mean annular velocity, polymer concentration and degree of polymer cross-linking affect axial solids distribution. The results show that the solids suspension capacity of the solutions is enhanced by the presence of polymer: the addition of guar gum decreases the minimum annular velocity needed to achieve a homogeneous axial solids distribution in the annular region. However, the amount of solids that is carried by the solutions is not always increased in the presence of polymer. The chemical cross-linking of guar gum with borax promotes a substantial increase of transported solids in the annular space. Overall, the results presented show that relatively high viscosities, high polymer relaxation times under shear flow and non-zero residual shear stresses are desired rheological characteristics for a drilling fluid to obtain a uniform solids distribution in the annulus, as well as high solids carrying capacity. [Copyright &y& Elsevier]

Predicting the minimum velocity of non-Newtonian fluids required to erode a solids bed is an important task for guaranteeing efficient solids transport process. This paper describes a combined theoretical and experimental investigation of the threshold condition of non-Newtonian fluids, including water, water-based mud (WBM) and oil-based mud (OBM), to initiate erosion of a solids bed. Drilling fluids with different base fluids have different threshold velocities, depending on the adhesion effect generated by the presence of stagnant fluids in a solids bed. Therefore, a new semi-mechanistic model of erosion criterion is proposed. In the model, a resistive force is introduced to handle the adhesion effect produced from different fluids, and it is quantified through an empirical correlation developed from the results of drain tests. A torque balance for driving and opposing forces is then constructed and solve numerically at the contact point of a superimposed particle for the determination of the threshold velocity. Model's predictions agree with experimental data obtained from bed erosion experiments with the use of WBM and OBM having similar rheological properties. • The influence of different drilling fluids, OBM and WBM, having similar rheological properties on critical resuspension velocity is investigated. • A semi-mechanistic model is developed to identify the minimum velocities required for bed erosion of the drilling fluids. • Model's predictions are validated against experimental results obtained from bed erosion experiments. [ABSTRACT FROM AUTHOR]

The performance of two electric submersible pumps (ESP), when pumping non-Newtonian polymer fluids, was tested at a pump test facility of the university. The results are compared with existing models, and the de-rating coefficients are evaluated for the operating range of the pumps that allow a proper design of ESP field installations. Two different electric submersible pump types (82 stages and 7 stages) were tested at the newly-built pump testing facility. The initial tests were performed with water at several frequencies to check the pump's performances, and the results were compared with the manufacturer's catalog curves. The performance measurements included pressure, flow rate, torque, rotational speed, and temperature. Besides, an intake pressure sensitivity analysis was performed. The actual polymer tests were conducted for three HPAM polymer concentrations (400-ppm, 800-ppm, 1600-ppm), three rotational speeds, and several discharge pressures. Additionally, fluid samples were taken during all tests and were subsequently analyzed. The polymer test results showed that the performance reduction factors for both pump types and all frequencies are much higher than expected. However, the provided polymer concentrations have low viscosity. Most likely, non-newtonian fluid behavior, specifically its viscoelasticity, is responsible for this substantial performance loss. Head and rate reduction close to 50 percent was measured at the best efficiency point of the pumps. A comparison to existing models indicates a significant underestimation of the performance loss when pumping a polymer solution. Moreover, the mechanical shearing of the molecular polymer chains was minor. Known models for pump performance do not apply in this instance. Because of the complexity of the polymer-laden fluid, we cannot offer one that works, and so we recommend that anyone in this situation must perform an experimental performance test. The novelty of those experiments was the testing of two powerful electric submersible pumps, using a non-newtonian polymer fluid, to investigate the pump performance, performance correction coefficients, and compares appropriate correction models to apply the gained knowledge more quickly in the field. • Although a low viscous shear-thinning fluid was tested, the observed ESP performance decrease was substantial • The flow rate and pump head drop, resulting in an efficiency decrease of up to 50%, compared to pumping freshwater. • Curve Correction Pairs approach and Hydraulic Institute Model. • Fake Viscosity approach seem to be realistic models. • No extraordinary high shear degradation of the fluid was observed in the first stages of the ESP. [ABSTRACT FROM AUTHOR]

A cuttings bed formed on the lower side of the wellbore is the most common drilling problem confronted when horizontal or highly deviated wells are drilled. The phenomenon is undesirable and has a detrimental effect on wellbore hydraulics and drilling performance. To achieve an efficient drilling operation, hydraulics optimization should be implemented by precisely predicting annular pressure loss and other hydraulic parameters. The accumulation of cuttings at the lower side of horizontal or highly inclined wellbores, combined with wellbore eccentricity and fluid rheological properties, create a complex behavior of pressure loss. In this study, a numerical approach is used to investigate the influence of the aforementioned factors. A numerical solution is performed for laminar flow of non-Newtonian fluids. A non-orthogonal, boundary-fitted curvilinear coordinate is developed, which is based on elliptic partial differential equations (PDE) to accommodate annular flow geometry with arbitrary cross-sections. Finite difference numerical schemes adapted to the coordinates is then used to analyze the problem. The numerical model determines the effect of hydraulic parameters of fluid flow thorough an irregularly shaped annulus and considers the following factors: flow rate, fluid rheological parameters, annular geometry and bed appearance. Numerical predictions from the model are verified against existing models and experimental data in literature; and good agreements are obtained. The developed numerical model can be combined with a 1-D solids transport model for designing oil and gas well drilling operations. • Investigate the effect of fluid rheology and flow geometry on hydraulic parameters of fluid flow thorough an irregularly shaped annulus. • A numerical model is developed using Finite Different Method (FDM). • Numerical predictions are validated against existing models and published experimental data. [ABSTRACT FROM AUTHOR]

A thorough understanding and accurate prediction of non-Newtonian fluid flow dynamics in rotating annular media are of paramount importance to numerous engineering applications. This is in particular relevant to oil and gas industry where this type of flow could occur during, e.g., drilling, well completion, and enhanced oil recovery scenarios. Here, mathematically we report on physical-based (numerical) and data-driven (intelligent) modeling of three-dimensional laminar flow of non-Newtonian fluids driven by axial pressure gradient in annular media that consist of a coaxially rotating inner cylinder. We focus on the dynamics of pressure loss ratio (PLR)—the ratio of total pressure loss in presence of rotation to that in stationary condition. We develop a novel and computationally efficient machine-learning based predictive model based on a Least Square Support Vector Machine (LSSVM) optimized with a Coupled Simulated Annealing (CSA) algorithm, which is trained and tested by 730 experimental data collected for this study. We then perform numerous CFD simulations governed by Navier-Stokes set of equations, which correspond to each of the experimental cases. Comparing the results with those obtained from a widely used empirical correlation for PLR, we find that the both of our numerical and machine-learning based models are more accurate and present a larger applicability domain. The predictive LSSVM model enjoys a supervised learning paradigm and leads to the highest accuracy, while the physically originated CFD approach captures more consistently the nonlinear behavior of PLR versus key system features. Following the validation of our models, we study the less understood effects of fluid viscosity, axial velocity and rotational velocity on PLR dynamics. We employ a dimensionless parameter analogous to Strouhal number and identify specific regimes where PLR shows a distinct behavior. Our study elucidates the role of shear-thinning effect and its interplay with inertial forces on the dynamical behavior of pressure loss (ratio) in rotating yield-power-law fluids. • A modeling study on dynamics of three-dimensional non-Newtonian flows driven by axial pressure gradient through annular media is conducted. • Effect of coaxial rotation of inner cylinder on overall pressure loss is investigated. • CFD simulations of flow as well as a LSSVM-CSA (machine learning) framework are developed. • The nonlinear behavior of pressure loss ratio (PLR) as a function of viscosity, axial and angular velocity is investigated. [ABSTRACT FROM AUTHOR]