Research on the mechanism of high-efficiency milling cement plugs with low weight on bit and high rotational speed

Experimental investigation of pressure loss and heat transfer in a rotor–stator cavity with two outlets

Downhole motors are widely used to drill vertical, directional and horizontal wells in conjunction with PDC bits. When a bent housing Positive Displacement Motor (PDM) is oriented for slide drilling to manipulate a wells trajectory, the drill string is not rotating. Consequently, the rate of penetration (ROP) typically decreases. It is therefore important to optimize Bottom Hole Assembly (BHA) performance in conjunction with PDC drill bits. This paper demonstrates how Motor performance data coupled with an ROP model can predict the optimal weight on bit (WOB) required to achieve maximum possible ROP for a given section of hole to be drilled. This approach solves the ROP model to determine ideal WOB in respect of any restrictions that PDM performance equations apply on it. Bit wear is included in the ROP model and an analysis is performed to optimize a given interval of well bore. The optimization approach is illustrated with two examples for different formation types and one field case comparing the performance of two Motors with PDC bits. The optimum WOB, maximum average ROP and differential pressure values are the outputs from the analysis. This analytical approach can be used to determine the optimum PDM / PDC Bit combination to achieve maximum ROP through a wide range of operational conditions. Introduction Positive Displacement Motors (PDMs) have gained widespread use in vertical, directional and horizontal drilling applications. In directional and horizontal mode, bent housing PDM's are used to manipulate well trajectory, (inclination and azimuth), to intersect bottomhole targets. Slide drilling occurs when the bend in the PDM is orienting in a certain direction. During slide drilling the drill string is not rotating. In slide drilling mode, Bit rotation results entirely from the Motor from drilling fluid being pumped through the drill string. Drilling in slide mode can significantly reduce ROP and increase well costs. Therefore the overall performance of Bit and Motor combination can have an extremely significant impact on drilling costs. In a Positive Displacement Motor the power section converts hydraulic energy of mud flow into mechanical rotary power, the reverse action of Moineau pump principle[1]. Each positive displacement motor has a helical rotor assembled inside a helical stator. Also, the rotor has one less spiral or lobe than the stator that results in continuous seal line between the rotor and the stator. The length of helical pitch for the stator is bigger than the rotor which forms cavity spaces between them. These cavities move along the power section from the inlet to outlet by rotating the rotor. Mud flow fills the cavity connected to inlet and extends it by the pressure applied on the rotor body until the next cavity connects to the inlet. This process forces the rotor to rotate eccentrically inside the stator. The performance of the motor is controlled by the combination of the rotor/stator lobe configuration and the motor stage number. Increasing the number of rotor lobes gives higher output torque of the motor and lower rotational speed.

In this paper numerical investigations are presented of how the axial position of the multiple reference frame (MRF) stator-rotor interface between the inlet guide vanes (IGVs) and the impeller would influence the predicted flow field for a turbocharger centrifugal compressor when simulated by the steady RANS method. In the first step, a total of three different axial positions of the MRF IGV-impeller interface were considered and compared with the results of an unsteady simulation to evaluate their accuracy. The results showed that the choice of the MRF interface location significantly influenced the predicted overall performance. At the lower rotational speed, the peak efficiency varied by 1.3% and the corresponding total pressure ratio varied by 0.022. At the high rotational speed, the different axial locations of the MRF interface varied the predicted choke point by 0.012 normalized mass flow rate. The mass flow rate of the near surge (NS) point was over estimated at both the high and low rotational speed by at least 0.038 normalized mass flow rate. Consideration of the flow field suggested that the MRF interface between the IGV and the impeller should be placed towards the upstream side of the available region to avoid being unphysically influenced by its interaction with the non-uniform pressure in the downstream subsonic flow field and to enable a more accurate prediction of the extent of the inducer shock in transonic operating situations. Based on this understanding, a further improvement was made for the setting of the MRF interface by employing a polyline interface. This achieved a more accurate numerical result for the NS operating point at low rotational speeds. The position of the MRF interface for modelling IGVs in a turbocharger compressor should be suitably chosen according to the objectives of the numerical study.

High rotational speed friction stir welding (FSW) was successfully employed to weld 6061-T6 aluminum alloy thin plates. The effect of high rotational speed and fast transverse speed on temperature distribution, microstructure evolution, and tensile properties of friction stir welded 6061-T6 joints was investigated in detail. The high rotational speed with fast transverse speed had a significant influence on the peak temperature in the nugget zone (NZ). Increasing the rotational speed and decreasing the transverse speed could obviously improve the peak temperature in the NZ, but exhibit little effect on the heat-affected zone under high rotational speed FSW. The NZ was characterized as a significant refinement of the equiaxed grain. The number of precipitates, subgrains, and low angle grain boundaries in the NZ of high rotational speed FSW joint increased significantly due to moderate heat input and strain rate. The weld zone was seriously softened at low rotational speed, whereas it was alleviated at high rotational speed and was affected slightly by rotational speed and transverse speed. The excellent mechanical properties of the friction stir welded 6061-T6 joints were obtained at a combination of high rotational speed and fast transverse speed. The maximum tensile strength reached 301.8 MPa, 85.8% of the base material.

An experimental study has been carried out in order to analyze the cavitation of a centrifugal pump and its effect on transient hydrodynamic performance during transient operation. The transient characteristics of the centrifugal pump were tested under various suction pressure and starting conditions. In transient operation of continuous starting and stopping process, instantaneous rotational speed, head, flow rate and suction pressure of the pump were measured. The effect of cavitation on transient performance of the centrifugal pump during transient operation was analyzed, and then the effects of starting acceleration rate and suction pressure of pump on cavitation were presented. Results showed that the cavitation would be delayed during rapid starting period. However, in the condition of low suction pressure and high rotational speed, pump cavitation is inescapable even if the starting period is less than a second. After the serious transient cavitation occurred, the transient performance of centrifugal pump would decline obviously, and the instantaneous head of pump would fluctuate.

Grain refinement and nanostructure formation in pure copper during cryogenic friction stir processing

Reversible hydrogen storage in the Mg–Si–H system has been studied through mechanochemistry using 2Mg + Si powders as reactants under a hydrogen pressure of 9 MPa. Depending on the milling energy, the equilibrium state of this system can be tuned: either Mg2Si or 2MgH2 + Si is formed as a stable phase at high and low rotation speeds, respectively. This result is reasonably explained by the change of local temperature at the collision impact with milling speed. Therefore, we here demonstrate that reversibility in the Mg–Si–H system is feasible following the reaction Mg2Si + 2H2 ↔ 2MgH2 + Si. Indeed, the direct reaction could be fully attained by milling Mg2Si at a low rotation speed. The reverse reaction could also be triggered by milling at a high rotation speed but only when some amount of Mg2Si is used to catalyze the reaction between magnesium hydride and silicon.

Using various tools to obtain downhole data to reach a precise pore pressure model is an important means to predict overpressure. Most downhole tools are connected to the lower end of drill string and move with it. It is necessary to understand the motion state and dynamic characteristics of drill string, which will affect the use of downhole tools. In this paper, a drilling process considering rock-breaking process in vertical wells is simulated using finite element method. In the simulation, gravity is applied to the whole drill string. The contact force between PDC bit and formation is the weight on bit (WOB). And a rotation speed is applied to the upper end of drill string. Analysis of the results shows that the vibration amplitude of bottom hole WOB (contact force between PDC bit and formation, which is the real WOB in drilling process) is bigger than the amplitude of wellhead WOB (acquired through conversion using Hook load, which is on behalf of the WOB obtained on drilling site). Both wellhead WOB and bottom hole WOB decline with a fluctuation in drilling process. In small initial WOB and low rotation speed conditions, the fluctuation of wellhead WOB focuses on low frequency, the fluctuation of bottom hole WOB focus on high frequency, and the phase of them are not identical. In large initial WOB and high rotation speed conditions, the fluctuation of wellhead WOB and bottom hole WOB both become more irregular. As for wellhead torque and bottom hole torque, the fluctuation of them mainly focuses on low frequency. And in high rotation speed conditions, wellhead torque may become negative. The research results are beneficial to the usage of downhole tools.

A research centrifugal compressor stage designed and built by Safran Helicopter Engines is tested at three inlet guide vanes (IGV) stagger angles. The compressor stage includes four blade rows: axial inlet guide vanes, a backswept splittered impeller, a splittered vaned radial diffuser (RD), and axial outlet guide vanes (OGVs). The methodology for calculating the performance is detailed, including the consideration of humidity in order to minimize errors related in particular to operating atmospheric conditions. The shift of the surge line toward lower mass flow rate as the IGV stagger angle increases highly depends on the rotation speed. The surge line shift is very small at low rotation speeds, whereas it significantly increases at high rotation speeds. A first-order stability analysis of the impeller and diffuser sub-components shows that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle. At low rotation speeds below a given mass flow rate, rotating instabilities (RI) at the impeller inlet are detected at zero IGV stagger angle. Their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet flow angle. Therefore, the onset of the rotating instabilities is delayed toward lower mass flow rates. At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases. As a result, the flow is highly alternate over two adjacent channels of the radial diffuser beyond the surge line at IGV stagger angle of 0 deg.

A research centrifugal compressor stage designed and built by Safran Helicopter Engines is tested at 3 IGV (Inlet Guide Vanes) stagger angles. The compressor stage includes 4 blade rows: axial inlet guide vanes, a backswept splittered impeller, a splittered vaned radial diffuser and axial outlet guide vanes. The methodology for calculating the performance is detailed, including the consideration of humidity in order to minimize errors related in particular to operating atmospheric conditions. The shift of the surge line towards lower mass flow rate as the IGV stagger angle increases highly depends on the rotation speed. The surge line shift is very small at low rotation speeds whereas it significantly increases at high rotation speeds. A firstorder stability analysis of the impeller and diffuser subcomponents shows that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle. At low rotation speeds below a given mass flow rate, rotating instabilities at the impeller inlet are detected at zero IGV stagger angle. Their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet flow angle. Therefore, the onset of the rotating instabilities is delayed towards lower mass flow rates. At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases. As a result, the flow is highly alternate over two adjacent channels of the radial diffuser beyond the surge line at IGV stagger angle of 0°.

Abundant drilling activities had confirmed that the fully rotary drilling can improve the rate of penetration effectively. However, the fully rotary drilling has brought some challenges for the trajectory control ability of the bottom hole assembly (BHA). One of the reasons is the effect of drill-string rotation was ignored in the existing methods, where the bent-housing positive displacement motor (PDM) was regarded as the prebending beam. According to the D’Alembert principle, the dynamical centrifugal force, generated by drill-string rotation, was equivalent to a quasi-static problem. The mechanical model of BHA with bent-housing PDM was established based on the Timoshenko beam theory. The calculated formula of bit side force (BSF) and resultant steering force (RSF) was deduced. The influences of inclination, rotational speed of drill-string, bend angle, eccentricity, stabilizer, weight on bit (WOB) and elbow position on the average BSF and RSF were investigated. The results show that the rotational speed of drill-string has a significant influence on the steering ability. The average BSF increases with the rotational speed of drill-string, while the RSF increases firstly and decreases subsequently. The controlling factor is the transverse component of drill-string gravity in a low rotational speed, while it is the centrifugal force in a high rotational speed. The BSF climbs up and then declines with WOB and rotational speed of drill-string. When the rotational speed of drill-string exceeds 100 RPM or WOB is higher than 80 kN, the BSF will decrease, resulting in a decline in angle buildup. The present method can be utilized to optimize the drilling parameters, BHA configuration and structure of bent-housing PDM.

Models incorporating liquid-gas mass-transfer and biofilm mass-transfer resistances were developed for trickling filters (TF) and rotating biological contractors (RBC). Biodegradation and volatilization coefficients were estimated from the previously described pilot-scale studies. The volatilization coefficients of a given compound in the TF and RBC were generally constant across the experimental conditions investigated. While biodegradation-rate coefficients were constant in the TF across experimental conditions, in the RBC the biodegradation-rate coefficients appeared to be greatest under conditions of low loading and high disc rotation speed and lowest under conditions of high loading and low disk rotational speed. The biofilm was completely penetrated by most of the contaminants and diffusional resistance did not limit the rate of biodegradation of any of the compounds. In the RBC, diffusion in the biofilm appeared to be limiting the biodegradation of toluene, o-xylene, and 1,3,5-trimethylbenzene. The ratio of gasand liquid-phase mass-transfer coefficients ranged from 91.4 for the TF to 5.6 for the RBC. Due to the relatively wide confidence intervals associated with these estimates, the values could not be statistically differentiated, however, the results suggest a significant contribution of gas-phase resistance to mass transfer in some cases.

Electroless plating, unlike electroplating, enables the application of metallic coatings without the need of providing electronic pathway to the plated region. As such, electroless plating is used to metalize non-conductive substrates and electrically isolated features. In semiconductor device metallization, electroless copper deposition is particularly advantageous for metalizing extremely small (nm scale) features because the process does not require a conductive seed layer. However, void-free metallization of vias and trenches typically requires bottom-up plating of the patterned feature, corresponding to high plating rate at the feature bottom and inhibited plating on the feature sidewalls, rim, and the top flat substrate. This is enabled in electrolytic plating by a special additives mixture that is not effective in the electroless system. In the absence of molecular level mechanistic understanding of the interaction between the additives and the plating process, the search for more effective additives is typically conducted empirically. However, the conventional injection technique,1,2 that provides rapid screening of electroplating additives by measuring the voltage transient following additives injection, is not applicable to the electroless system. Consequently, testing of additives for bottom-up fill in electroless systems entails actual plating of features and their microscopic examination, requiring significant effort and time. Further complication arises due to the fact that the additives containing electroless system is significantly more sensitive to transport and agitation than its electrolytic counterpart. Presented here is a novel approach providing simple and rapid screening of additives applicable to electroless systems. The technique is based on electroless plating of a flat (featureless) rotating disk electrode. Two electroless plating experiments are conducted in the same tested electrolyte: one, with the disk rotating at a high speed, and the second, at a low rotation rate, measuring in both experiments the electroless plating rate from the deposit amount. As illustrated schematically in Fig. 1, we look for an additives mixture that provides a low plating rate at the high rotation speed (which corresponds to the high transport rates and thin boundary layer prevailing on the flat substrate and feature rim), and a high plating rate at the low rotation speed (simulating the thick boundary layer at the bottom of the feature). The high rotation speed, ω1, which relates to the mass transport boundary layer thickness, δ1 through the Levich equation3 [Eq 1], is selected such that it corresponds to the relatively high transport rates prevailing over the flat substrate. In equation 1, D and ν are the additive’s diffusivity and the electrolyte kinematic viscosity, respectively. The low rotation rate, ω2, is selected to simulate the hindered transport of the additive to the feature bottom, corresponding the significantly larger mass transport boundary layer, δ2. The equality on the left-hand side of equation 2, can be derived following the analysis of Adolf and Landau4, where L and R are the feature’s depth and width, respectively, Γ is the additive surface saturation concentration, and Cb is its bulk concentration. ω2is selected from the equality on the right-most side of equation 2. As shown in Figure 2, in the absence of additives, the electroless plating rate increases with rotation rate, as copper transport is enhanced. This system is not expected to provide bottom-up fill, since the deposition rate will be higher on the via rim and the flat top substrate. However, utilizing 1.5 ppm mercaptopropanesulfonic acid (MPS) as an inhibiting additive, leads to the desired significantly lower plating rates at higher rotation speeds, as compared to those at lower rotation speeds. This is most likely due to the enhanced transport towards the substrate of the low concentration inhibitor at the higher rotation rates. Consequently, MPS is a promising additive for promoting bottom-up electroless plating of recessed features. Unfortunately, MPS by itself yields a dark and nonuniform deposit, so polypropylene glycol and dipyridyl were added to generate a bright and uniform deposit. Additional analysis and further experimental details are provided in the presentation. Acknowledgements Atotech GMBH is acknowledged for funding this study and for providing helpful input. References R. Akolkar and U. Landau, J. Electrochem. Soc., 151, C702 (2004).Lindsay Boehme and Uziel Landau, J. Appl. Electrochem., 46(1), 39-46 (2016).V. G. Levich, “Physicochemical Hydrodynamics”, Prentice-Hall, 1962.James Adolf and Uziel Landau, J. Electrochem. Soc., 158 (8) 1-8 (2011). Figure 1

Heat transfer from rotating annular fins

The lift force on an isolated rotating sphere in a uniform flow was investigated by means of a three-dimensional numerical simulation for low Reynolds numbers (based on the sphere diameter) (Re<68.4) and high dimensionless rotational speeds (Г<5). The Navier-Stokes equations in Cartesian coordinate system were solved using a finite volume formulation based on SIMPLE procedure. The accuracy of the numerical simulation was tested through a comparison with available theoretical, numerical and experimental results at low Reynolds numbers, and it was found that they were in close agreement under the above mentioned ranges of the Reynolds number and rotational speed. From a detailed computation of the flow field around a rotational sphere in extended ranges of the Reynolds number and rotational speed, the results show that, with increasing the rotational speed or decreasing the Reynolds number, the lift coefficient increases. An empirical equation more accurate than those obtained by previous studies was obtained to describe both effects of the rotational speed and Reynolds number on the lift force on a sphere. It was found in calculations that the drag coefficient is not significantly affected by the rotation of the sphere. The ratio of the lift force to the drag force, both of which act on a sphere in a uniform flow at the same time, was investigated. For a small spherical particle such as one of about 100 μm in diameter, even if the rotational speed reaches about 106 revolutions per minute, the lift force can be neglected as compared with the drag force.