Positive Displacement Research Articles

An improved 3.5\xb0 single-bend positive displacement mud motor and its parameter optimization for deep short-radius open-hole sidetracking

In order to improve the sidetracking efficiency for the recovery of old wells in the middle and later stage of oilfield, an improved 3.5° single-bend positive displacement mud motor (PDM) is designed. This novel single-bend PDM first uses the structure of 3.5° large angle PDM + cushion block, which can meet the sidetracking requirements of high build-up rate and short directional section in large curvature short-radius sidetracking wells and can significantly improve the build-up ability. Furthermore, based on the mechanical analysis and finite element numerical simulation, its parameter optimization is carried out. The optimal main parameters are determined as follows: the structural bending angle is 3.5°, the outer diameter is 95 mm, the height of the cushion block is 14 mm, the distance between the cushion block and the bending point is 120 mm, the minimum curvature radius is 35.50 m, and the weight-on-bit (WOB) should be less than 30kN. The initial section build-up rate of directional sidetracking can be increased up to 52.67°/30 m ~ 53.29°/30 m. The research results have been applied in Tahe oilfield. It proves that 3.5° single-bend PDM can sidetrack successfully at one time and increase deviation, and the overall angle change rate of bottom hole can reach 45.00°/30 m, which can meet the requirements of short-radius sidetracking with curvature radius of 40 m. The successful application of open-hole sidetracking technology with 3.5° single-bend PDM is of great significance to the production increase and efficiency improvement of old oilfields.

Research on the hydroformed metal stator bushing based on full restraint at both ends

The rubber bushing of the positive displacement motor is easy to age, and the metal bushing stator is proposed. We designed and carried out an experiment of hydroforming of metal stator bushing with equal wall thickness. After the experiment, we found that the metal stator bushing was wrinkled. We applied the finite element method to study the cause of wrinkles in the metal stator bushing. The research results show that the main reason why the metal stator bushing is wrinkled is that the inner diameter of the tube blank is larger. Therefore, We use the finite element method to study the influence of the inner diameter of the tube blank on the quality of the metal stator bushing. From the research results, we found that the suitable inner diameter of the tube blank is 86.5 mm. The surface of the metal stator bushing is smooth, the inner surface of the metal stator bushing is close to the mold, and the maximum gap is 0.15 mm. The metal stator bushing formed by tube blank III has a larger minimum wall thickness, a smaller maximum wall thickness, and the smallest wall thickness variance, which is 2.6 mm, 3.22 mm, and 0.028, respectively. The smallest plastic strain, the largest plastic strain, and the largest displacement of the metal stator bushing formed from the tube blank III are 0.2, 0.7, and 14 mm, respectively. When L2/L1 = 0.9577, the quality of the metal stator bushing is better.

Constrained sintering of alumina micro-ring films on stiff and compliant substrates: Constriction or dilation?

The sintering behavior of ring-shaped alumina films on different types of substrates (polished sapphire and platinum coated sapphire) has been investigated. Variation of substrate material, layer thickness and heating schedule led to different interface properties which were quantified using the interfacial friction parameter as a measure of the slip distance of the free edge. This interfacial friction implies the compliance of the film-substrate interface, thus allowing the quantification of the ability of the free edges to slide along the substrate. Ring structures were made with outer radii of 100 –500 µm and the ratios of inner to outer radii were 0.1 (broad ring segment with small inner hole) and 0.4 (narrow ring segment with big inner hole). During sintering, the outer film edge was found to recede in all systems, whereas the behavior of the free edge located at the inner hole was strongly dependent on the interfacial friction. When sintering of alumina micro-rings were carried out on sapphire substrate, a high interfacial friction resulted in the positive displacement of the inner edge, causing the inner hole to open. Sapphire substrates coated with platinum offered a lower interfacial friction resulting in the opening of the hole in a more distinct manner as compared to the uncoated sapphire substrates. As the thickness of the film also affects the interfacial friction, a thicker film (27 µm) on platinum coated substrate had very low friction. This resulted in a negative displacement of the inner ring leading to closing of the hole. These effects are in qualitative agreement with the predicted analytical model for constrained sintering of annular ceramic films. A combination of film thickness, substrate material and aspect ratio of the ring either leading to constriction or dilation of the annular alumina film were carefully investigated.

Analysis of the influence of geometric parameters on working processes in a two!stage hybrid power machine of positive displacement without a gas cap with a profiled working chamber of the second stage

A principal scheme is considered and a mathematical model of work processes is developed in a two-stage hybrid power machine of positive displacement without a gas cap with a profiled working chamber of the second stage. The mathematical model is based on the basic laws of conservation of energy, volume and mass for a dropping liquid and a compressible gas in the second stage. The diameter of the supply pipeline and the initial radius of the profiled working chamber in the second stage are selected as the main geometric parameters that have the greatest influence on the work processes. The response functions are found that determine the dynamics of the fluid flow in the machine under study and its main integral characteristics. Keywords: work process, cooling, reciprocating compressor, hybrid power machine of positive displacement, profiled working chamber Scherba_V_E@list.ru

Hybrid Approach for Health Monitoring of Mud Motor Fleet

A mud motor is a kind of positive displacement motor (PDM) that is used to transform the hydraulic energy of drilling fluids (mud) into mechanical energy. This mechanical energy enables the drill bit to cut the rock and drill a well. It is one of the key parts of downhole assembly that is placed in the drillstring to provide additional power to the bit while drilling as its power downhole output is still unmatched. Mud motor failure is a common and costly issue in drilling operations. A proper prediction of the failure as well as an estimation of the remaining useful life (RUL) are essential for timely downhole mud motor maintenance and drilling optimization.
 Until now, the oil and gas industry has lacked reliable procedures to monitor and maintain the health of mud motors, resulting in unnecessary maintenance costs as well as unpredictable and costly drilling failures. Recently, Schlumberger has addressed this problem with an industry-first prognostics and health management (PHM) solution, which not only estimates the health of the mud motor and tracks RUL, but also creates a new service for clients and provides a competitive advantage. Timely mud motor retirement and maintenance will ultimately reduce failures and NPT.
 The proposed PHM solution is suitable for real-time implementation and combines two different sterling algorithms for reliable prediction of possible problems with the mud motors. It enables the estimation of the mud motor health both on the system level with the entire mud motor (system level PHM model) and on the subcomponent level (power section PHM model) – the most critical component of the mud motor.
 The system-level algorithm model leverages both surface and downhole drilling data as well as mud motor characteristic curves to compute the severity of mud motor degradation. A special mud motor degradation indicator is defined. The indicator is calculated to evaluate the degree of power section decay at each time recorded from thousands of field jobs. The trends of the degradation with respect to drilling time and drilling distance are extracted for each motor job. Based on the study of large datasets, good correlation was observed between the mud motor degradation indicator and mud motor failures.
 The power section PHM model uses downhole measurements to estimate the RUL of the elastomer – the life-limiting component inside the power section. It is based on a high-fidelity model and uses a hybrid approach by combining a high-fidelity physics-based model of a power section and data-driven approaches with machine learning techniques. Machine learning methods were applied to derive a reduced order surrogate model (ROM) of power sections from the original physics-based models for real-time applications. This ROM outputs the estimation of performance and fatigue characteristics of the considered power section depending on the considered drilling conditions such as differential pressure, downhole temperature, flow rate, and mud compatibility. As the result, the model analyzes accumulative risk of fatigue failure and produces real-time health information for the power section as a percentage of the remaining lifespan.
 The new solution for mud motor PHM was successfully verified and tested in the field. Comparison of the predicted mud motor fatigue life with the actual observed postjob conditions and job failures demonstrated good results of the developed models. The PHM enables optimization of mud motor selection, drilling configuration, and maintenance operations by minimizing RUL uncertainties while facilitating rerun decisions and avoiding overmaintenance and premature retirements. The whole solution is currently being integrated into a drilling platform including the maintenance system, the well construction planning, and the execution. It maximizes the equipment usage with increased drilling performance without sacrificing reliability and enables optimal fleet management of a drilling process for revenue maximization.

Analysis of Bitcoin's Impact on the Efficiency of a Diversified Portfolio for Brazilian Investors

Purpose – This paper aims to investigate if the inclusion of Bitcoin among the assets available to retail investors in the Brazilian market has an impact on the efficient frontier and, therefore, on the optimal choices of investors. Design/methodology/approach – This study calculates the efficient frontier with and without the inclusion of Bitcoin and estimates optimal portfolios for different criteria and time intervals. The sample period runs from 07/01/2013 to 06/30/2018 and the daily closing values of the selected assets/indices were used. Findings – This study finds evidence that the inclusion of Bitcoin among the investment alternatives would cause a statistically significant positive displacement and an expansion of the efficient frontier of the Brazilian retail market. This would result in a significant increase in the return on the tangency portfolio. In addition to improving the indicators of optimization of the risk-return binomial, the cryptoasset would be included in many optimal portfolios in the 2013Q3-2018Q2 period. Originality/value – The results obtained show that, as reported for more developed markets, Bitcoin has caused an expansion of the efficient frontier of the Brazilian retail market.

Analytical grid generation and numerical assessment of tip leakage flows in sliding vane rotary machines

The research presents a new analytical grid generation methodology for computational fluid dynamics studies in positive displacement sliding vane rotary machines based on the user defined nodal displacement approach. This method is more inclusive than state of the art ones since it enables the investigation of a broader range of design configurations, such as single, double and multiple-acting vane machines with non-circular housing, slanted blade and asymmetric blade tip profiles. Node number and radial divisions of blade tip are the parameters that affect most the mesh quality. The method was validated against indicated pressure measurements on a rotary vane expander resulting in a confidence interval within 4.31%. The benchmark analysis showed that the proposed method is as accurate as the manual ANSYS ICEM one but more than 1500 times faster (111s instead of 48h to generate 360 grids). The paper further proposes a novel method to track the leakage flows at the blade tip gaps of vane machines through a post-processing routine in ANSYS CFD-Post based on rotating monitoring planes. The leakage assessment on the vane expander case study showed that a 10 μm gap between blade tip and the 76 mm stator led to a 0.06 unit increase of the expander filling factor.

Ingersoll Rand to pay €431.5mn for Seepex

Ingersoll Rand Inc has entered into an agreement to purchase the German positive displacement (PD) pump company Seepex GmbH in a €431.5 million cash deal.

Two-Zone Simulation of an Axial Vane Rotary Engine Cycle

An axial vane rotary engine (AVRE) is a novel type of rotary engines. The engine is a positive displacement mechanism that permits the four “stroke” action to occur in one revolution of the shaft with a minimum number of moving components in comparison to reciprocating engines. In this paper, a two-zone combustion model is developed for a spark ignition AVRE. The combustion chamber is divided into burned and unburned zones and differential equations are developed for the change in pressure and change in temperature in each zone. The modelling is based on equations for energy and mass conservation, equation of state, and burned mass fraction. The assumption is made that both zones are at the same pressure <i>P</i>, and the ignition temperature is the adiabatic flame temperature based on the mixture enthalpy at the onset of combustion. The developed code for engine simulation in MATLAB is applied to another engine and there is a good agreement between results of this code and results related to the engine chosen for validation, so the modelling is independent of configuration.

Optimization of the Configuration of the Power Sections of Special Small-Sized Positive Displacement Motors for Deep-Penetrating Perforation Using the Technical System “Perfobore”

Innovative technologies for the secondary drilling of productive reservoirs, based on the multihole drilling deeply remoted from the wellbore and with controlled trajectories, to overcome the contamination of the pay zone, and with the ability to carry out various geological and technological wellworks many times over, can significantly increase the efficiency of the development of old and marginal wells. To implement such tasks, it is necessary to use special technological drilling equipment, one such technical system (TS) is the Perfobore system, which uses a modular construction. The methodology allows to choose an optimal variant for the power sections with a high-torque, small-sized positive displacement motor PDM, previously developed by specialists at the Perfobore company. This made it possible to design universal sectional motors with diameters of 43 to 54 mm with improved characteristics compared to serial PDMs. The production of prototypes of multi-section PDMs and their successful bench and then field tests (FT), from 2018 to 2020, in the Uralopovolzhskaya and West Siberian oil and gas provinces, as part of the TS Perfobore, proved the correctness of the chosen technical strategy.

Needleless connector nursing care - Current practices, knowledge, and attitudes: An Australian perspective.

Inappropriate needleless connector (NC) care is associated with device failure from catheter occlusion and patient blood stream infections (BSIs). This can be attributed to a lack of knowledge of connector designs and flushing, clamping, and syringe disconnection techniques. This study aimed to assess nurses' practice, knowledge, attitudes, and key influencers on appropriate care of NCs in an Australian facility and compare these with studies undertaken in the United States in 2011. A cross-sectional online survey was sent via email with a SurveyMonkey® link to all nurses working in clinical areas (total population sampling approach; approximately 1500 nurses), at an Australian hospital, in 2018. The survey was anonymous and open for 6 weeks. Analysis was with R software. Response rate was approximately 19% (n=283). Most (89%) of nurses stated that they clean NCs before each access. Only 25% correctly recognised the negative pressure NC, and 79% correctly identified the correct clamping and disconnection sequence. Positive pressure displacement devices were correctly identified by 44% of respondents, with 34% identifying the correct clamping and disconnecting technique. Nurses reported their behaviour was most influenced by local senior nurses. There remains a significant gap in nurses' knowledge of NC device types, as well as the correct clamping and syringe disconnection for both negative and positive displacement NCs. This survey reaffirms that senior nurses are the key influencers of nurses' adherence to best practice guidelines.

Physical Performance Testing of a Prototype Gerotor Pump Operating in Liquid and Gas/Liquid Conditions

Summary Gerotors are positive displacement pumps and potential artificial lift options in the oil and gas industry. This study presents the performance characteristics from physical testing of a unique one-stage, equal-walled gerotor pump design operating in oil and oil/air mixtures. The pump was tested at various rotational speeds in a flow loop. The performance results were obtained to ascertain potential design optimizations of the pump before embarking on manufacturing and testing of the field prototype pump. A physical prototype of a one-stage 400 series gerotor pump, suitable for application in a 5.5-in. casing, was designed, manufactured, assembled, and tested. Mineral oil and air were used as the operating media. For given pump outlet valve settings, the pump rotational speeds were set to 200, 250, 300, and 350 rev/min. Gas volume fractions (GVFs) at the pump inlet were varied from 0% to the maximum the current pump design could handle. For each test point, the corresponding pump parameters were measured. Dimensionless performance plots were established for obtaining pump performance at other flow conditions. The results showed that pump flow rate decreased with increasing differential pressure, typical of positive displacement pumps. At 200 and 350 rev/min, maximum pump delivery is approximately 190 and 330 B/D of oil, respectively, at zero differential pressure. The pump can supply flow against a differential pressure of up to approximately 5.5 psi at 200 rev/min and 15 psi at 350 rev/min. For the 200 to 350 rev/min speed range, volumetric efficiencies varied from 30 to 73%, whereas the electric power input varied from 145 to 191 W. When pumping oil/air mixtures, the current gerotor pump design can handle 15% GVF maximum, at 250, 300, and 350 rev/min. For certain pump outlet pressures, the total fluid flow rates decreased as the GVF increased to 15%. The volumetric efficiencies at 15% GVF varied from 32 to 53% for the 300 to 350 rev/min speed range, whereas the motor electric power input decreased with increasing GVF up to 15%. In conclusion, increasing the pump rotational speed improves the volumetric efficiency and gas-handling capability of the gerotor pump. These observations will aid in the required design optimization to enhance the performance of the future field prototype gerotor pump. This study presents the capabilities of gerotors as potential artificial lift alternatives to handle liquid and gas/liquid mixtures for boosting applications in oilfield operations. The technology with additional design optimization can be readily integrated into oilfield equipment architecture. The mechanical simplicity of gerotors and their compactness provides a promising artificial lift substitute that may be implemented for downhole or surface production of liquid or gas/liquid mixtures in the oil and gas industry.

Fatigue of crystallizable rubber: Generation of a Haigh diagram over a wide range of positive load ratios

A Haigh diagram is built for a carbon black filled rubber blend that exhibits Strain Induced Crystallization (SIC) for a wide range of positive displacement ratios. A strategy for the initiation detection, which becomes difficult for high displacement ratios, is proposed and validated thanks to regular visual follow-up. Some experimental cautions are taken to avoid any temperature and strain rate effects on the results, more specifically on the strain induced crystallization phenomenon. It is found that a reinforcement related to strain induced crystallization is present for load ratios (up to displacement load ratio of 0.35). For higher load ratios, the reinforcement effect reduces leading to a Haigh diagram that looks like a bell, as already shown by Cadwell et al. (S. Cadwell, R. Merrill, C. Sloman, F. Yost, Dynamic fatigue life of rubber, Industrial and Engineering Chemistry 12 (1940) 19–23).

Research on the Nonlinear Characteristic of Flow in the Electro-Hydraulic Servo Pump Control System

In an electro-hydraulic servo system, the system flow is used as an intermediate variable to control the output displacement/force/speed of the actuator, and it plays the role of a medium for energy transmission and conversion. Therefore, the control of the system flow is the essence of state control for the system actuator. The purpose of this paper is to study the non-linear characteristics of pump control system flow and pave the way for high-performance control of the system. Based on the flow partition idea, the system output flow is divided into the dead zone, load zone, and saturation zone. We establish a mathematical model of the hydraulic system to analyze and study the effect of the nonlinear characteristics of the servo motor and the positive displacement pump on the system flow partition characteristics. We focus on the effects of the positive displacement pump shear flow internal leakage, pressure difference flow internal leakage, oil compression, servo motor rotation friction, and servo motor torque reserve rate on the system flow output, and analyze the partition characteristics of the system flow under different working conditions. We provide a theoretical basis for a high-precision control strategy for a hydraulic system.

Geometric Design of the Limaçon-to-Circular Fluid Processing Machine

Abstract A limaçon machine is a rotary positive displacement device, in which the housing and rotor are constructed of limaçon of Pascal curves. Previous works have been published to investigate the working of these machines in two applications: gas expanders and compressors. This article presents a theoretical investigation into the potential of modifying the rotor profile of the limaçon machines to simplify the machine’s manufacturing process and to reduce production cost. The proposed modification will produce new characteristics for the housing–rotor interaction. An outcome that motivates the need to obtain new mathematical models to investigate the housing–rotor interference and describe the volumetric relationship of the new machine. This article also employs an optimization approach to design the best machine for a given set of operating conditions, i.e., expander, compressor, and pump. The outcome of this study confirms the validity of the proposed modification and its potential to produce a limaçon machine with favorable characteristics.

A study on mechanical properties of equal wall thickness rubber bushing of positive displacement motor based on hydrogenated nitrile butadiene rubber aging test

Shale gas production has become the main driver of global gas production growth. Deep shale gas is difficult to extract, which puts forward higher requirements for drilling speed increase. The downhole power drilling tools are mainly screw drilling tools. Conventional screw drill tool stator bushing has poor heat dissipation, which is prone to thermal hysteresis failure, shortening drilling tool life, and is not suitable for high temperature and high pressure environment of deep shale gas wells. Equal wall thickness screw drilling tools and hydrogenated nitrile rubber have better high temperature resistance. Therefore, based on the thermal aging experiment and constitutive model of the rubber changes the displacement of the inner cavity of the stator bushing and the difference between the front and the back is up to 21.6%. The increase of the interference and eccentricity between rotor and motor leads to the increase of the maximum von Mises stress of the stator bushing and the thermal hysteresis temperature. The influence of the interference is greater than the influence of the eccentricity so that the interference should be given priority in the design. This paper provides a theoretical reference for the design and optimization of equal wall thickness bushing of positive displacement motor.

Challenges in 3D CFD Modelling of Rotary Positive Displacement Machines

The use of Computational Fluid Dynamics (CFD) and Computational Continuum Mechanics (CCM) for analysis of rotary positive displacement machines is exponentially increasing which was mostly allowed by the development of methods for generating numerical grids of complex domains within the machines. However there are several challenges with the commercial CFD/CCM codes which are preventing generic use of CFD. These are conservativeness of spatial discretisation caused by the inappropriate grid generation, numerical instabilities and dissipations caused by misalignments and application of inappropriate discretisation of equations and the speed and accuracy of multiphase models used in CFD of positive displacement machines.In this paper the authors will review methods used for modelling of rotary positive displacement machines and challenges which developers and users of these methods face. The paper will also offer some solutions and directions for resolving these issues.

Discussion of Numerical Methods used in Positive Displacement Comprehensive Mechanistic Models: Case Study using the Z-Compressor

Comprehensive mechanistic models have been widely used for simulating positive displacement (PD) compressors or expanders. Such models are based on a thermodynamic analysis of generic control volumes that describe the working chambers. The thermodynamic analysis results in a set of non-linear ordinary differential equations (ODEs) that describe conservation of mass and energy. The derived ODEs are used to predict the evolution of the thermodynamic properties of the working fluid with respect to crank angle or time. The solution scheme of a mechanistic model involves different layers of solvers that handle the step-by-step integration, the cycle-to-cycle continuity as well as the overall energy balance. Since most of the PD machines feature multiple control volumes that merge or split (e.g. scroll-type) or wrap-around a rotor (e.g. screw-type) the integration scheme faces challenges due to the stiffness of the equations or discontinuities in the control volume definition.In this paper, a discussion of different integration schemes and numerical considerations are proposed that are applied to a novel compressor called the z-compressor which presents a high-degree of intrinsic stiffness. A simplified comprehensive model is developed which is validated against experimental mass flow rate data for a prototype compressor with an average model-predicted error of less than 2%. This model is used to explore the differences in two ODE solvers from the ODE suite in MATLAB, (ODE15s, and ODE113). These results are further compared against an existing, simplified, Z-compressor model developed in PDSim which uses an explicit, lower order, solver the Adaptive Runge-Kutta (RKF). The results suggest that the semi-implicit solver (ODE15s) provides an efficient means for stepping through the compression process ODEs compared to the explicit solvers.

Research of synthetic corundum in plunger pairs of power hydraulics

The development of hydraulic technologies requires the use of new structural materials. The study used the main provisions of the theory of positive displacement hydraulic machines and hydraulic drives and methods for their solution using multiphysics software. The article presents the results of a comparative analysis of the performance of plunger pairs made of synthetic corundum in hydraulic machines of power drives. The effect of using synthetic corundum in hydraulic power drives is determined. Analysis of the obtained results makes it possible to conclude that when using synthetic sapphire as a plunger material, taking into account the preservation of structural geometry, maximum stresses are reduced by 4.7%, contact stresses by 4.7%, and deformation by 44%, with a decrease in weight by 49%.

Design of model reference adaptive–PID controller for automated portable duodopa pump in Parkinson’s disease patients

This paper focuses on the design of an automated portable Duodopa pump (PDP) for Parkinson’s disease (PD) patients, with the aim of achieving robust performance on intra-day, intra-patient and inter-patient variability under various disturbances, parameter variations and uncertainties. For achieving this objective a suitably modified Hacisalihzade’s pharmacokinetics-pharmacodynamics (PK-PD) model of Levodopa has been chosen. By using Bernoulli’s equation for pressure balance and Hagen-Poiseuille law for flow rate, a positive displacement piston type drug dispensing syringe connected to PEG-J (percutaneous endoscopic gastrostomy- Jejunal) tube is modeled under the assumption of Newtonian, incompressible and laminar flow properties. A PDP is proposed employing model reference adaptive-PID (MRA-PID) as the control strategy and the closed-loop responses are compared with a PID controller tuned by particle swam optimization (PSO-PID). In MRA-PID controller an impeccable tracking of reference model is accomplished by a parameter adaptation mechanism such as a gradient decent method named MIT rule. The overall performances of both the controllers are evaluated under two different perturbation protocols as well as sensor noise and the robust stability is analyzed theoretically for structured uncertainties in system gain and time constant by using a cohort of eight in- silico subjects with large inter-patient variability. Even though the responses from both the controllers are stable with zero steady state error and zero undershoots, the dynamic performances of proposed controller is superior and safe under unannounced meal disturbances, intra and inter patient variability.