Research On Displacement Current Phase Tomography Method And System Of Gas-water Two-phase Flow

Gas-water two-phase flow is a common flow pattern in the process of natural gas extraction and transportation.Affected by geological conditions,shale gas reservoirs are characterized by high salinity.When faced with the gas-water two-phase flow containing high salinity water,the nonlinearity of the traditional electrical tomography(ET)problem would be aggravated.In order to solve this limitation,this article studies the visual measurement system based on Displacement Current Phase Tomography(DCPT),DCPT belongs to the category of ET,like ECT(Electrical Capacitance Tomography,ECT),DCPT is a non-contact and non-destructive measurement technology,which has a new sensitivity theory-The sensitivity theory of dielectric loss factor can be applied to the visual measurement of gas-water two-phase flow containing high salinity water.According to theoretical analysis,simulation modeling,and experimental research methods,this paper proposes a gas-water two-phase flow DCPT visualization measurement system based on a new Image reconstruction strategy.The main research work and periodic results of this article are as follows:Firstly,combining the research background of this subject and the similarity of ET technology,the ET technology is introduced,and the current research status of ET technology is reviewed and analyzed from three aspects: sensor structure,measurement and acquisition circuit,and image reconstruction algorithm.The non-linear problem of traditional ET technology is solved.Then,starting from the principle of the DCPT system,the mathematical and physical model of DCPT and the sensitivity theory are studied,and the calculation formula of the sensitivity coefficient is given.According to the pipe and electrode structure parameters used in the experiment,a DCPT sensor model was established in the COMSOL multiphysics simulation software.Secondly,based on the simulation model constructed above,the simulation analysis of eccentric flow,laminar flow and other common flow patterns with different holdup rates in a water environment with a conductivity of 0.1S/m has been carried out.The simulation results show that DCPT is more effective than ECT.A wider range of linearization assumptions,the position and contour of the reconstructed image are closer to the real medium distribution.By using the LBP and Landweber algorithm to compare the reconstructed images of the gas-water two-phase flow with different flow patterns,it is found that when the flow pattern is stratified flow(when the interface is continuous),the image reconstruction effect of the LBP algorithm is better,while the image of the Landweber algorithm is blurred and the flow pattern cannot be identified.However,the reconstruction effect of the Landweber algorithm is better than that of the LBP for the non-layered flow.Therefore,the split-type imaging strategy is proposed and passed Simulation experiments verify the effectiveness of this strategy and improve the quality of image reconstruction.Thirdly,in terms of system hardware,the admittance angle measurement circuit,multi-electrode array switch control circuit and analog-to-digital conversion circuit with good stability and low noise are designed.In terms of software,a gas-water two-phase flow DCPT based on QT and MATLAB mixed programming is designed.The host computer software of the visual measurement system.Finally,through experiments,the stability of the repeat measurement of the admittance angle measurement circuit is evaluated,and the effectiveness of the DCPT visualization measurement system of the split-type imaging strategy is verified by simulating the gas-water two-phase flow of different flow patterns.From the experimental results,it can be concluded that the DCPT visual measurement system for gas-water two-phase flow in this paper can accurately reflect the distribution of the cross-sectional medium.