A Study On Dynamic Behavior And 3-D Numeric Simulation For Progressing Cavity Pump

As a new artificial lift technology with high efficiency and environmental advantages,progressing cavity pump(PCP) is regarded as one of the most INNOVATIVE techniques in the history of petroleum industry.In the past twenty years,the application of PCP increased remarkably in worldwide.However,due to the limitation in high complexity of its configuration,the elastomer's high nonlinearity in mechanic behavior and sensibility to applied operating conditions, how to precisely describe PCP's operating mechanism has been a bottleneck issue bothering production engineers for years.With the development of computer technique and numeric simulation technique, it is possible to describe PCP's performance quantitatively by means of finite element method(FEM).In the past ten years,the correlative studies mainly focused on two-dimension static-mechanic models which differed from real objective considerably.Studies indicated that,two-dimension static-mechanic models couldn't describe the complex dimensional shape of PCP correctly.Moreover,it might lead to the misunderstanding on PCP's mechanics behavior.In addition,the thermal destruction of elastomer was a severe issue in PCP application.And a proper thermal model is required to describe the status of temperature field.The present study attempts to develop an approach for dealing with the above issues.Chapter 2 begins from the introduction of 3-d geometric model of rotor and stator,including the equations of pump's mold line and line of action.The PCP's kinematics model is discussed consisting of rotor's kinematics principle,rotor's surface and line of action kinematics principle.Based on the describing the mechanic relationship among rotor,stator and operating fluid,the forces and torques produced in the process of PCP operation are classified and discussed in details.In the first section of chapter 3,elastomer's hyperelastic model is analyzed in order to get its marco-mechanic characteristics.Referring to the studies on tire mechanics,Yeoh model is adopted as the constitutive model of PCP elastomer.The coefficients in the constitutive equation were determined by experimental data.And the process in ABAQUS is introduced on optimizing the constitutive equation of elastomer.The creation of stator-rotor's contact model is another key question for PCP 3-D dynamic simulation model.In contact issue,despite of creating the general control formulations,the kinetic and dynamic conditions on contact surface must be considered as well.And the prime one is "unpenetration" condition.In the second section of chapter3,the form and boundary conditions of contact model are discussed in details.Chapter 4 presents the whole process of creating PCP 3-D dynamic model with FEM software in form of several typical cases.The effect of contact friction between rotor and stator are discussed in details.Simulation results indicate that,the increase of interference will result in the increase of friction considerably and the change of eccentricity will influence the friction as well.Simulation results also proved that elastomer's stiffness and imcompressable characteristics could influence the friction and stress distribution of the pump.PCP 2-D temperature field model is achieved by means of uncoupling method in chapter 5.Apart from environmental temperature influence,heat produced from elastomer is another important reason of thermal destruction.Due to the viscous-elastic characteristics,elastomer will have viscous loss under periodic load. And the viscous loss energy will mainly be transferred into heat.Simulation indicates that the non-uniform distributed temperature field resulted from heat loss effect has more negative effect on stator's mold line.Two case studies are presented in chapter 6,introducing the experiences in PCP optimal design with 3-D dynamic simulation model and temperature field analysis method in ASP flooding and deep wells.