Optimization And Research On Structural Parameters Of S-CO₂ Downhole Sand Mixing Device

At present,the sand mixing equipment widely used in shale gas mining are all ground sand mixers,which need to be operated under high pressure and low temperature environment.The requirements for sand mixing equipment are high,and it takes some time before and after the sand concentration adjustment.This article addresses the shortcomings of existing sand mixing devices and comprehensively considers various factors that affect sand mixing performance.Based on the jet principle,an S-CO₂ downhole sand mixing device is designed to replace the existing surface sand mixing device.The device has strong adaptability and small footprint.Based on CFD analysis of the flow field in the cavity of the S-CO₂ downhole sand mixing device,numerical simulation experiments were conducted to study the mixing performance,and the structural parameters were optimized through orthogonal experimental method.The main content is as follows:1.Firstly,the basic properties of S-CO₂ and the structural design theory of the sand mixing device are analyzed.Using the methods of continuity equation,energy equation and Bernoulli equation,the dimensionless parameters with the incident flow pump,the characteristic equation of the structural design of the sand mixing device is deduced,and the preliminary design scheme of the sand mixing device is given.2.Then carry out the overall structural design of the S-CO₂ downhole sand mixing device.Design and calculate the structural dimensions of the main components of the S-CO₂ underground sand mixing device using the empirical calculation formula of the jet pump,and provide the working principle and connection method of the S-CO₂underground sand mixing device.Introduce the main technical parameters and analyze the strength of the main components and parts.3.Secondly,the CFD numerical simulation method is used to verify the grid independence of the fluid domain model of the S-CO₂ downhole sand mixing device to find the optimal grid size,reduce errors caused by grid size,and conduct a macroscopic analysis of the flow field in the cavity of the S-CO₂ downhole sand mixing device.4.Subsequently,the single factor method was used to analyze the factors that affect the mixing performance of the S-CO₂ downhole sand mixing device.The CFD method was used to analyze the changes in the main structural parameters,revealing the impact of the single structural parameter change on the mixing performance of the S-CO₂ downhole sand mixing device.This study has guiding significance for the optimization of the structural parameters of the S-CO₂ downhole sand mixing device.5.Finally,the orthogonal experimental method was used to optimize the structural parameters.The study on the structural parameters of the S-CO₂ underground sand mixing device showed that the nozzle diameter,throat distance,throat diameter The significant impact of throat length and diffuser angle on the sand mixing performance of the S-CO₂ downhole sand mixing device ranges from high to low.Statistical analysis software Minitab was used to analyze the relationship between the corresponding factors and the performance of the sand mixing device,as well as the relationship between each factor and the sand mixing performance.After verification,it was found that the flow field stability and sand mixing performance of the model were significantly improved after parameter optimization.This paper takes the S-CO₂ underground sand mixing device as the research object,and uses CFD numerical simulation and orthogonal experimental methods to provide a theoretical basis for the design and parameter optimization of the underground sand mixing device,laying a certain foundation for the development of large displacement and miniaturization of the sand mixing device.