Design And Numerical Simulation Of Equal Diameter Electric Control Sliding Sleeve For Multistage Fracturing Of Oil And Gas Well

Horizontal well multi-stage fracturing technology is currently the main technology for the exploitation of shale gas and other low-permeability oil and gas reservoirs.According to the operation mode,it can be divided into bridge plug multi-stage fracturing,sliding sleeve multi-stage fracturing and coiled tubing drag hydraulic sandblasting multi-stage fracturing technology.Pitching sliding sleeve is the core tool of the large-scale sliding sleeve multi-stage fracturing technology.According to the opening mode,it can be divided into pitching holding pressure switch sliding sleeve,the differential pressure switch sliding sleeve,the coiled tubing switch sliding sleeve,and the intelligent fracturing sliding sleeve control system.Because the intelligent sliding sleeve can avoid the diameter difference of the pitching sliding sleeve,the number of fracturing stages is limited;in addition,it can also reduce the process of coiled tubing operation.Therefore,domestic and foreign experts and scholars had done a lot of work on the research and development of the intelligent fracturing sliding sleeve.Due to factors such as the underground working environment,the reliability of the intelligent fracturing sliding sleeve is poor and the industrial application is limited.For this reason,this article is based on the pitching fracturing sliding sleeve technology,combined with automatic control technology.Aiming at the 3(1/2)" tubing fracturing pipe string fracturing in old wells,this paper adopts the electronic control switch and the identification subsection to realize the counting and control functions.The electronic control sliding sleeve composed of the downhole equal diameter sliding sleeve and the electronic control switch delivered from the wellhead enriches the products of the intelligent fracturing sliding sleeve control system.According to the working environment requirements of the electronic control switch,a control circuit with Hall sensor and MSP430 series single-chip microcomputer as the core is selected.Based on the working principle of the electronic control switch,using Altium Designer software,the circuit schematic design and PCB board drawing of the main control board and the Hall sensor are completed,and the control program is written and burned through the IAR For MSP430 software.Using the modeling function of AutoCAD and Solid Works software,the core components such as the inner sliding sleeve,the reducing ball seat,and the identification subsection in the electronic control sliding sleeve are designed in three dimensions.Through the Workbench software,the finite element analysis of the forming process of the reducing ball seat is carried out,and the optimal structure and process parameters of the reducing ball seat are optimized: the arc surface center angle is 40°,the inner cone angle of the inner sliding sleeve is 6.65°,and the axial force required for ball seat reduction forming is132.80 k N.It provides a theoretical basis for downhole reduction forming.The numerical analysis model of the ball seat,the inner sliding sleeve and the electronic control switch is established,and the average contact pressure distribution of all contact surfaces under different pressure differences is obtained,and the sealing performance is evaluated.According to the actual working conditions of the fracturing pipe string construction,theoretical analysis and numerical simulation methods are used to optimize the structural parameters,stress analysis and strength evaluation of the core components such as inner sliding sleeve.This ensures the rationality and safety of the designed tool structure.Using the sub-domain solution method of immersion boundary,the numerical simulation of the coupling dynamics of the electronic control switch and the fluid in the pipe string is carried out.The results show that the fluid resistance of the electronic control switch increases with the increase of pumping pressure and fluid viscosity.The stable speed of the electronic control switch increases with the increase of pumping pressure,and decreases with the increase of fluid viscosity.The initial speed change has little effect on the stable speed and fluid resistance.After the simulation results are fitted,the stable speed calculation formula of the electronic control switch is obtained;considering the execution time when the claws of the switch are fully extended,the minimum distance between the sliding sleeves is calculated,which provides a theoretical basis for the determination of electronic control sliding sleeve fracturing process parameters.