Simulation Study On Characteristic Of A Soft Sealing Direct Micro Flow Pressure Relief Valve Under Deep-Well Circumstance

The ambient temperature and pressure will change with the change of depth of investigation.The highest temperature can reach 180? and the highest pressure can reach 140 MPa when the well depth is 7km.In order to balance the increased ambient pressure when the logging instrument is in the process,a pressure balancing mechanism need to be installed in the logging instrument.The bidirectional pressure relief valve is needed to protect the instrument from damage for the high differential pressure between the inner hydraulic oil and the outside slurry because the balancing mechanism has certain response time when the instrument is working.Limited by the size of the wellhead,the measuring equipment is generally small,and the hydraulic oil in the balancing mechanism is about 2-3 liters,so The flow of the valve is small too;the valve should be well sealed to avoid the corrosion damage of various components by the slurry or blocking of the balancing piston because of slurry particles when the valve is not open.This article studies the characteristic of the soft sealing direct micro flow pressure relief valve under ultrahigh ambient pressure and temperature by simulation,It lays a technical foundation for the design of bidirectional pressure relief valve for the logging instrument.Soft sealing pressure relief valve mathematical model is established based on the direct poppet pressure relief valve.The differential pressure under different ambient pressure?ambient temperature and well depth is obtained by simulation.By applying the differential pressure obtained by the previous simulation to the structural dynamics finite element model,the open time?deformation of the o-rings,displacement and velocity of the spool,radius of the valve port under different ambient pressure and temperature?well depth can be obtained.After meshing the geometry of the valve obtained from the previous finite element simulation by ICEM software,the mesh file is imported into FLUENT software to calculate the characteristics of the flow field with different valve opening.Through the analysis of the flow coefficient and flow force under different environment,the relationship between the flow coefficient?coefficient of the revised flow force and viscosity?valve opening is obtained.The characteristic of pressure relief valve under different ambient pressure?temperature,and well depth is obtained by changing the parameters in SIMULINK software according to different situations.Results show that the stability of soft sealing direct micro flow pressure relief valve becomes worse at the same flow with the change of well depth,and the steady differential pressure and valve opening decrease with the change of well depth too.The steady flow increases with the increase of well depth under same differential pressure.In order to make the well depth have little influence on the relationship between the steady differential pressure and flow of the soft sealing straight micro flow relief valve,the viscosity of the hydraulic oil should be small and should hardly be influenced by the temperature and pressure so that the valve has large flow coefficient and small valve opening,which improves the performance of the pressure relief valve and prevents the balancing piston from being blocked because of slurry particles.