| Progressive cavity pumping has been widely used at home and abroard,however,its limited temperature resistant capacity which is generally below 160 degrees centigrade makes it unsuitable for heavy oil thermal recovery wells.In recent years,some foreign countries have developed a metal progressive cavity pump,whose stator and rotor are both made of metallic materials capable of resisting a temperature of as high as 400 degrees centigrade.It has been tested in such heavy oil themal production wells as SAGD.According to test applications,this pump is mainly of large displacement and high revolutions.At present,domestic and foreign research on metal progressive cavity pump is at a preliminary stage,focusing on relevant indoor performance tests.This doctoral dissertation optimized the profile fit for metal progressive cavity pump,its stator/rotor fit clearance,and investigated the features and kinematic law of the metal PCP,thereby forming an optimal design method,leaking mechanism and computaional model for the metal PCP,which will play a sinificant role in advancing technologies and applications of metal PCP.Considering the stator/rotor clearance fit featue of metal PCP and in order to avoid the appearance of incorrect profiles,the optimal combination of radius variation ratio and equidistant coefficient of isometric profiles for 2:3 and 3:4 curtate hypocycloid is optimized,and a comprehensive coefficient method is used to optimally form profiles of the 2:3 curtate hypocycloid and the 1:2 normal hypocycloid.The thermal analysis and the Fluent fuid simulation methods of the Static Structural module of Workbench FEM are adopted to conduct studies of effect of thermal expansion on the stator/rotor fitting clearance and influence of clearance on leakage and contact pressure,and simulate effect of rotational speed and fluid viscosity on the pump efficieny,and establish the stator/rotor fitting clearance of the metal PCP,which is 0.15-0.4 millimeters.The clearance leakage theory is utilized to establish a stator/rotorleakage calculation model for the metal PCP on the basis of clearance fit and a computation model of pump fillage degree,which takes into account the influence of gas and viscosity.Compared with actual field production data,the relative error is 5.8% and thus of a higher accuracy.Based on the the optimization results,a GLB160-30/AM metal PCP was prototype manufactured and its characteristics was tested on a newly built physical simulation experimental platform,which functions as real-time acquisition,record and analysis of flow,pressure,rotational RPM and torque.The physical simulation experimental results show that fluid viscosity and rotation speed have a main effect on pump efficiency of the metal PCP,and that its pump efficiency reaches above 70% in the case of an oil with a viscosity of 32 m Pa.s and revolutions of 100~200 RPM while in the case of water,its pump efficiency varies in inverse proportion to pressure and rotational speed,and the pump outlet pressure can reaches 11 MPa.Up to now,the developed metal progressive cavity pump has found successful applications in 8 wells with an average pump efficiency rise from 35.8% to 52% and an average power consumption decrese from 4.6kw.h to 2.2kw.h when every ton of well fluid is lifted up 100 meters.Among the 8 wells,the first test pump has run as long as 542 days and still operates well till now.compared with foreign technologies,the developed metal PCP in this dissertation is of such a small displacement and low rotational speed as less than 30m3/d and 150 RPM,and is characterized by high pump efficiency and long life.Its field test performance verifies feasibility and correctness of the optimum design method and theoretical modeling for the metal PCP proposed in this dissertation,providing a theoretical support for further studies on the metal PCP. |
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