Prediction of Cuttings-Induced Annular-Pressure Loss in Extended-Reach Wells

Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary,percussion,or auger methods and brought to the surface in the drilling mud.When these cuttings enter the annulus,they have an effect on the drillingfluid rheology and density,which is,in general,quite difficult to evaluate.By introducing an empirical correlation for the rheological properties of cuttings-laden drillingfluids,this study proposes a pres-sure-loss prediction method for an extended-reach well(ERW).After verifying the accuracy of this method,a case study is considered and a sensitivity analysis is conducted assuming a yield-power lawfluid.The results show that an increased concentration of cuttings in the annulus contributes to an increased annular pressure loss.Com-pared to their effect on the drillingfluid density,cuttings have a greater impact on the drillingfluid rheology.A larger rate of penetration contributes to an increased annular pressure loss.For higher drillingfluidflow rates,the annular pressure lossfirst decreases and then it increases.In addition,the annular pressure loss becomes high-er as the cuttings’particle size decreases and the cuttings’concentration grows.

Study on Horizontal Well Layout Boundary Considering Wellbore Pressure Loss

Based on the Dikken analytical calculation method of wellbore pressure loss under single-phase fluid and turbulent flow conditions, the correlation model between horizontal well output and horizontal section length and horizontal section distributed pressure difference is constructed. The influence degree of wellbore pressure loss on daily oil production of horizontal well, horizontal section pressure and production effect of horizontal well under different horizontal well lengths is analyzed, which provides certain reference for the design of horizontal well length and well layout.

EFFECT OF DUMP GAP ON TOTAL PRESSURE LOSS IN DUMP DIFFUSER

The dump diffuser is an important component in advanced annular combustor, and its performance affects greatly the fluid field and pressure loss of the combustor. This paper presents the characteristics of the total pressure loss. Experiments and numerical simulations, keeping the inlet March number of prediffuser constant ( Ma =0 20), are carried out to obtain the regularity of the total pressure loss. It varies with the relative dump gap ( δ =1 2～3 0)by changing the position of prediffuser and combustor liner, respectively. Research shows that there exists the minimum total pressure loss ( σ *=1 6%～1 75%) when relative dump gap δ is about 1 8.

Experimental investigation of particle-induced pressure loss in solid–liquid lifting pipe

In order to investigate the characteristics of particle-induced pressure loss in the solid–liquid lifting pipe,a series of experiments were conducted in 200 mm diameter lifting pipe.Simulation manganese nodules with five different mean diameters of10 mm,20 mm,30 mm,40 mm and 50 mm were used,both in isolation and a combination in equal fraction by mass.The flow velocities in the lifting pipe ranged from 0.12 m/s to 1.61 m/s,and the mass of particles employed was 10 kg for each particle diameter.Three regimes,wavy bed,partly fluidization,and fully fluidization,were observed over the flow velocity.The solid–liquid pressure drop data were measured by differential pressure transmitter,and pressure drop caused by the solid particles was calculated and analyzed.The results show that the evolutions of the pressure loss due to solid particles are relevant to the solid–liquid flow regimes,and they are distinctly influenced by fluid velocity and particle size.

Modified Pressure Loss Model for T-junctions of Engine Exhaust Manifold

The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have focused on constant pressure models, constant static pressure models and pressure loss models. However, low model precision is a common disadvantage when simulating engine exhaust manifolds, particularly for turbocharged systems. To study the performance of junction flow, a cold wind tunnel experiment with high velocities at the junction of a diesel exhaust manifold is performed, and the variation in the pressure loss in the T-junction under different flow conditions is obtained. Despite the trend of the calculated total pressure loss coefficient, which is obtained by using the original pressure loss model and is the same as that obtained from the experimental results, large differences exist between the calculated and experimental values. Furthermore, the deviation becomes larger as the flow velocity increases. By improving the Vazsonyi formula considering the flow velocity and introducing the distribution function, a modified pressure loss model is established, which is suitable for a higher velocity range. Then, the new model is adopted to solve one-dimensional, unsteady flow in a D6114 turbocharged diesel engine. The calculated values are compared with the measured data, and the result shows that the simulation accuracy of the pressure wave before the turbine is improved by 4.3% with the modified pressure loss model because gas compressibility is considered when the flow velocities are high. The research results provide valuable information for further junction flow research, particularly the correction of the boundary condition in one-dimensional simulation models.

Influence of bluff body shape on wall pressure distribution in vortex flowmeter

To investigate the influence of bluff body shape on wall pressure distribution in a vortex flowmeter,experiments were conducted on a specially designed test section in a closed water rig at Reynolds numbers of 6.2×10 4-9.3×10 4.The cross sections of the bluff bodies were semicircular,square,and triangular shaped,and there were totally 21 pressure tappings along the conduit to acquire the wall pressures.It is found that the variation trends of wall pressures are basically identical regardless of the bluff body shapes.The wall pressures begin to diverge from 0.3D(D is the inner diameter of the vortex flowmeter) in front of the bluff body due to the diversity in shape,and all reach the minimum values at 0.3D behind the bluff body.A discrepancy between the triangular or square cylinder and the semicircular cylinder in wall pressure change is observed at 0-0.1D behind the bluff body.It is also found that the wall pressures and irrecoverable pressure loss coefficients increase with flow rates,and the triangular cylinder causes the smallest irrecoverable pressure loss at a fixed flow rate.

COMPUTATIONAL FLUID DYNAMICS RESEARCH ON PRESSURE LOSS OF CROSS-FLOW PERFORATED MUFFLER

The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.

Numerical simulation investigation on pressure loss of diffusion tank of axial main fan

Based on the engineering application, the angle range of rectifying airflow unit attaching diffusion tank is from 2.5° to 7.5°. In the range of average inlet velocity of 25.0 m/s to 55.0 m/s of diffusion tank, numerical simulations of diffusion tank were done. The results of numerical simulations of diffusion tank are shown as follows： ③ In cases of the inlet velocity range from 25.0 m/s to 55.0 m/s, and the angle range of rectifying airflow unit from 2.5° to 7.5°, the average value of pressure losses decreases to the minimum when the angle is 4.5°.② In cases of the inlet velocity of 35.0 m/s, the pressure loss of diffusion tank decreases to the minimum when the angle of rectifying airflow unit is 5.5°. ③ As far as there are different angles of rectifying airflow unit, pressure loss increases gradually along with the addition of inlet velocity.

Mudcake effects on wellbore stress and fracture initiation pressure and implications for wellbore strengthening

Although a large volume of mudcake filtration test data is available in the literature, effects of mudcake on wellbore strengthening cannot be quantified without incorporating the data into a stress-analysis model. Traditional models for determining fracture initiation pressure （FIP） either consider a wellbore with an impermeable mudcake or with no mudcake at all. An analytical model considering permeable mudcake is proposed in this paper. The model can predict pore pressure and stress profiles around the wellbore, and consequently the FIP, for different mudcake thickness, permeability, and strength. Numerical examples are provided to illustrate the effects of these mudcake parameters. The results show that a low-permeability mudcake enhances FIP, mainly through restricting fluid seepage and pore pressure increase in the near- wellbore region, rather than by mudcake strength. Fluid loss pressure （FLP） should be distinguished from FIP when a mudcake is present on the wellbore wall. Fracture may occur behind the mudcake at FIP without mudcake rupture. The small effect of mudcake strength on FIP does not mean its effect on FLP is small too. Mudcake strength may play an important role in maintaining integrity of the wellbore once a fracture has initiated behind the mudcake.

Experimental study of a simple pressure loss coefficient model for multi-hole orifice

A throttling experiment for the multi-hole orifice （MO） using water was conducted based on the conclusion of key parameters affecting the MO throttling performance. Testing MOs and standard orifice plates （ SO ） were designed for the throttling experiment to compare the throttling effect using the equivalent diameter ratio （RED） and diameter ratio （RD ） as key parameters, respectively. Meanwhile, effective metrical conditions were provided for experimental accuracy. The throttling model form was determined according to the theoretical throttling model of SO. Then the unknown parameters involved were identified by experimental data. A good concordance between the modeling computation and experimental results shows a validation of the MO throtting model.

Numerical Characterization of the Annular Flow Behavior and Pressure Loss in Deepwater Drilling Riser

In drilling a deepwater well,the mud density window is narrow,which needs a precise pressure control to drill the well to its designed depth.Therefore,an accurate characterization of annular flow between the drilling riser and drilling string is critical in well control and drilling safety.Many other factors influencing the change of drilling pressure that should be but have not been studied sufficiently.We used numerical method to simulate the process of drill string rotation and vibration in the riser to show that the rotation and transverse vibration of drill string can increase the axial velocity in the annulus,which results in the improvement of the flow field in the annulus,and the effect on pressure loss and its fluctuation amplitude.In addition,there are also multiple secondary flow vortices in the riser annulus under certain eccentricity conditions,which is different from the phenomenon in an ordinary wellbore.The findings of this research are critical in safely controlling well drilling operation in the deepwater environment.

Analysis of Gas Flow Rate and Pressure Loss of Medical Mask Differential Pressure Tester

The objective of this study is to find a suitable method to overcome the pressure loss problem in the gas pipe during the gas exchange detection of medical masks.Based on the European Standards EN 14683,the parameters of a medical mask differential pressure tester were selected,subsequently two schemes of gas pipe layouts were designed,including four kinds of pipe diameter which are 4,5,6.5,and 8mm respectively.Lastly,the models of each scheme were established and imported into Fluent,and the relevant parameters were set for simulation.After data analysis,the results showed that among the four different pipe diameters,the pressure loss of 8mm diameter of the pipe was lower in both the schemes,additionally the pressure loss of the second scheme(the gas pipe was short and smooth)was lower under the same pipe diameter.At the flow rate of v=8L/min,the pressure loss from the inlet to the measurement point is less than 200Pa,and the estimated measurement error is less than 1.5%.In conclusion,shortening the length of the pipe,and increasing the diameter of the pipe can reduce the gas pressure loss,subsequently improve the measurement accuracy of the medical mask differential pressure tester.

旋转条件下U形通道转弯段形状对流动和传热特性的影响

In this paper,the flow and heat transfer characteristics in U-shaped channel with three different turn shapes are studied.The rotation number ranges from 0~0.251,Reynolds number are 11500,23000,34500,respectively.The results show that the flow separation and reattachment in the turning section are the key factors affecting the local heat transfer and pressure loss of U-shaped channel.The square turn will generate corner vortices at the outside of the turning section,and the size of the inner separation vortex and reattachment vortex is larger than that of the other two turn shapes.The existence of vortex system will increase the mixing and enhance heat transfer,but increase the pressure loss,so its relative Nusselt number and pressure loss are the largest.There are corner vortices on the outside of the turning section of the channel with a inner circle turn and outer square turn,but the arc-shaped inner edge makes its separation delay and the separation vortex decrease,and the size of the reattachment vortex also decreases.The arc shaped outer edge of the channel with circle turn in both inner and outer further inhibits the generation of corner vortices,so its relative Nusselt number and pressure loss are the lowest.Rotation will cause the fluid to deflect under the influence of Coriolis force,strengthen the heat transfer on the trailing surface of radial outflow and the leading surface of radial internal flow,and generate secondary flow and separation vortex in the turning section,resulting in the change of vortex structure in the turning section.With the increase of rotation number,the Nusselt number of the three types of turning section structures increases.The thermal performance factor of the three channels increases with the increase of rotating speed,and the channel with a inner circle turn and outer square turn is the highest,which is 9.6%higher than the channel with circle turn in both inner and outer on average,and 17.8%higher than the channel with square turn in both inner and outer.

Tip Clearance Flows in Turbine Cascades

This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-hole probe at exit Mach numbers of 0.10, 0.14 and 0.19. At each exit Mach number, experiments are performed at the tip clearance heights of 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of the blade height. The effects of the non-uniform tip clearance height of each blade in the pitchwise direction are also studied. The results show that at a given tip clearance height, generally, total pressure loss rises with exit Mach numbers proportionally. At a fixed exit Mach number, the total pressure loss augments nearly proportionally as the tip clearance height increases. The increased tip clearance heights in the tip regions of two adjacent blades are to be blame for the larger clearance loss of the center blade. Compared to the effects of the tip clearance height, the effects of the exit Mach number and the pitchwise variation of the tip clearance height on the cascade total pressure loss are so less significant to be omitted.

The Effects of Fluid Rheology and Drillstring Eccentricity on Drilling Hydraulics

Accurate determination of hydraulic parameters such as pressure losses, equivalent circulation density (ECD), etc. plays profound roles in drilling, cementing and other well operations. Hydraulics characterization requires that all factors are considered as the neglect of any could become potential sources of errors that would be detrimental to the overall well operation. Drilling Hydraulics has been extensively treated in the literature. However, these works almost entirely rely on the assumption that the drill string lies perfectly at the center of the annulus—the so-called “concentric annulus”. In reality, concentricity is almost never achieved even when centralizers are used. This is because of high well inclination angles and different string geometries. Thus, eccentricity exists in practical oil and gas wells especially horizontal and extended reach wells (ERWs) and must be accounted for. The prevalence of drillstring (DS) eccentricity in the annulus calls for a re-evaluation of existing hydraulic models. This study evaluates the effect of drilling fluid rheology types and DS eccentricity on the entire drilling hydraulics. Three non-Newtonian fluid models were analyzed, viz: Herschel Bulkley, power law and Bingham plastic models. From the results, it was observed that while power law and Bingham plastic models gave the upper and lower hydraulic values, Herschel Bulkley fluid model gave annular pressure loss (APL) and ECD values that fall between the upper and lower values and provide a better fit to the hydraulic data than power law and Bingham plastic fluids. Furthermore, analysis of annular eccentricity reveals that APLs and ECD decrease with an increase in DS eccentricity. Pressure loss reduction of more than 50% was predicted for the fully eccentric case for Herschel Bulkley fluids. Thus, DS eccentricity must be fully considered during well planning and hydraulics designs.

Limitations in the Use of the Equivalent Diameter

This paper deals with the inaccuracy assessment of the friction pressure loss estimation based on Darcy formula combined with an equivalent hydraulic diameter and a friction factor valid for circular pipes when applied to a square rod bundle. The assessment has been done by comparing the analytical and semi-empirical predictions with two different CFD codes results: CFX and NEPTUNE_CFD. Two different analytical approaches have been considered: the whole-bundle and sub-channel approaches, both for laminar and turbulent flow conditions. Looking at results, it is reasonable to assume that an error in the range of 11% - 23% is likely when using equivalent diameter in the laminar regime. In the case of turbulent regime, the equivalent diameter works better and the error is in the range between a few percent and ~12%.

The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes,high performance gas mixer is deeply needed for the injection of NH3 or O3.In this study,a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics(CFD).The results obtained using Particle Image Velocimetry(PIV)correlated well with the results obtained from simulation.The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer.Optimal process conditions and design were investigated.When L/D equaled 4,coefficient of variation(COV)was<5%.The inlet velocity did not affect the distributions of turbulent kinetic energy.In terms of both COV and pressure loss,the inner connector is important in the design of the static mixer.The nozzle length should be set at 4 cm.Taking both COV and pressure loss into consideration,the optimal oblique degree is 450.The averaged kinetic energy changed according to process conditions and design.The new static mixer resulted in improved mixing performance in a more compact design.The new static mixer is more energy efficient compared with other SV static mixers.Therefore,the double swirl static mixer is promising in gas mixing.

Bionic Design and Finite Element Analysis of Elbow in Ice Transportation Cooling System

With the increase in mining depth, mine heat harm has appeared to be more prominent. The mine heat harm could be resolvedor reduced by ice refrigeration. Thus, ice transportation through pipeline becomes a critical problem; typically flowresistance occurs in the elbow. In the present study, according to the analysis of the surface morphology of fish scale, abiomimetic functional surface structure for the interior wall of elbow is designed. Based on the theory of liquid-solid two phaseflow, a CFD numerical simulation of ice-water mixture flowing through the elbow is carried out using finite element method.Conventional experiments of pressure drop and flow resistance for both bionic and common elbows are conducted to test theeffect of the bionic elbow on flow resistance reduction. It is found that with the increase in the ice mass fraction in the ice-watermixture, the effect of bionic elbow on resistance reduction becomes more obvious.

Optimization Design of Hydraulic Valve Block and Its Internal Flow Channel Based on Additive Manufacturing

Hydraulic valve block is an important part of the hydraulic system.The traditional hydraulic valve block is made by turning and milling,drilling and boring,which leads to many right-angle bending and closed cavity structure of process holes in its internal flow channel,seriously affecting the flow performance of oil.Based on the new design space provided by additive manufacturing technology,the internal hydraulic flow channel of valve block is optimized by using B-spline curve.Computational fluid dynamics analysis is carried out on the hydraulic flow channel to determine the optimal flow channel structure with the smallest pressure drop.The weight reduction of hydraulic valve block is carried out through topology optimization.According to the results of topology optimization,using the method of selective laser melting(SLM),the printing of the hydraulic valve block is completed.The optimized hydraulic channel reduces the pressure loss by 31.4%compared with the traditional hydraulic channel.Compared with the traditional valve block,the hydraulic valve block manufactured by SLM with topology optimization reduces the weight by 33.9%.Therefore,the proposed flow channel optimization and valve block lightweight method provide a new reference for the performance improvement of the internal flow channel of hydraulic valve block and the overall lightweight design of valve block.

Numerical Simulation of Turbulent Flow of Hydraulic Oil through 90° Circular-sectional Bend

Oil flow through pipe bends is found in many engineering applications. However, up to now, the studies of oil flow field in the pipe bend appear to be relatively sparse, although the oil flow field and the associated losses of pipe bend are very important in practice. In this paper, the relationships between the turbulent flow of hydraulic oil in a bend and the Reynolds number Re and the curvature ratio δare studied by using computational fluid dynamics （CFD）. A particular emphasis is put on hydraulic oil, which differs from air or water, flowing through 90° circular-sectional bend, with the purpose of determining the turbulent flow characteristics as well as losses. Three turbulence models, namely, RNG κ-ε model, realizable k-ε model, and Reynolds stress model （RSM）, are used respectively. The simulation results in the form of contour and vector plots for all the three turbulence models for pipe bends having curvature ratio of δ=0.5, and the detailed pressure fields and total pressure losses for different Re and δ for RSM are presented. The RSM can predict the stronger secondary flow in the bend better than other models. As Re increases, the pressure gradient changes rapidly, and the pressure magnitude increases at inner and outer wall of the bend. When δ decreases, two transition points or transition zones of pressure gradient arise at inner wall, meanwhile, the transition point moves towards the inlet at outer wall of the bend. Owing to secondary flow, the total pressure loss factor k increases as the bend tightens, on the contrary, as Re increases, factor k decreases due to higher velocity heads, and the rapid change of pressure gradient on the surface of the bend leads to increasing of friction and separation effects, and magnified swirl intensity of secondary flow. A new mathematical model is proposed for predicting pressure loss in terms of Re and δ in order to provide support to the one-dimensional simulation software. The proposed research provides reference for the analysis of oil flow with higher Re in the large bends.