| The presence of water in wellbore during the later nature gas extraction can lead to serious production reductions,in order to ensure regular gas production from a gas well,water must be removed from the gas.The downhole vortex tool is a drainage and gas extraction tool installed in the wellbore to reform flow pattern by inducing swirl flow to reduce the critical gas flow rate,which has advantages such as low cost,simple structure and easy installation.In order to guide the structural design and installation position of the vortex tool and improve the recovery rate of gas reservoirs with water,it is necessary to study the three-dimensional spatiotemporal swirl flow field structure and its attenuation characteristics after the gas-liquid two-phase flow through the vortex tool.When measuring the distribution of bubbles in a swirl flow field,traditional tomographic techniques such as resistance and capacitance have soft field measurement problem as the sensitive field distribution is affected by the bubble distribution.WMS is an invasive electrical measurement method with the characteristics of simple structure and image reconstruction algorithm,fast imaging speed and low development cost.This paper presents an experimental study of the phase distribution characteristics,flow parameter distribution and swirl decay characteristics of different air-water two-phase flows through vortex tool,based on the optimization of the WMS hardware structure and post-processing algorithms.Mainly includes the following contents:(1)Validation of the WMS measurement principle and optimization of geometrical parameters based on potential field simulation.The WMS measurement field is modelled,the potential field control equations and boundary conditions are determined,and the potential field simulations are carried out using COMSOL software to explain the measurement principle and feasibility of the technique at a theoretical level.The effect of different geometrical parameters on the measurement results is obtained through a large number of simulations and a better geometrical parameter is obtained.(2)The data post-processing algorithm is improved to obtain the complete data processing process and to validate the algorithm.The bubble extraction process was improved to propose a non-recursive bubble extraction algorithm that grows from a two-dimensional cross-section to a three-dimensional time direction.A complete data processing flow from WMS current signal to vacancy bubble share,to bubble distribution,phase interface structure and gas phase velocity is completed.Experiments are carried out to verify the measurement accuracy of the currently developed WMS with a measurement error of between 5%.(3)Using the developed WMS measurement system to measure the swirl formation and the swirl decay process,observed the swirl gas column flow,swirl bubble flow,and found that the fluctuation of average void fraction can reflect the bubble merging,crushing and column fracture,and obtained the distribution of local void fraction,bubble size distribution and gas phase velocity.The method of quantitative evaluation of spiral decay based on the mean and variance of the cross-sectional diameter of the air column yields a range of conditions that produce a stable air core in this experimental environment and the decay rate of the air core diameter.The research work in this paper develops a WMS that can be used for swirl flow research,enriches the understanding of swirl flow formation and decay,and provides theoretical support for the optimization and installation of vortex tools in petroleum engineering. |
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