Study On Erosion And Fluid-Structure Interaction Vibration Characteristics Of Ground High-Pressure Manifold System

Ground high-pressure manifold system is the key equipment of oilfield fracturing operation,when the fracturing fluid containing solid particles is injected at high velocity,its inner wall will be destroyed by erosion.At the same time,it may also have serious vibration problems due to high working pressure and fluid-structure interaction,which challenges its work safety.In this paper,based on numerical simulation,the erosion wear and vibration characteristics of ground high-pressure manifold system when conveying fracturing fluid containing solid particles at high pressure are studied,and the weak links of the manifold system that may fail are found and the operating life of the manifold system is predicted.The main research contents and achievements are as follows.(1)Three kinds of high-pressure manifold systems with the same pipe diameter and wall thickness and different number of elbows are simulated by using the discrete phase model in Fluent software,and erosion numerical simulation is carried out at the same particle phase concentration.The inlet velocity conditions are constant and consistent with the actual flow rate at the outlet of the fracturing pump changing periodically with time.The results show that the serious erosion areas of each manifold system are concentrated on the outer wall surface of each elbow,and the erosion rate of the manifold increases with the increase of the number of elbows.Under the same displacement,the erosion and wear of the manifold system under the condition of periodic inlet velocity are more serious than those under the condition of constant inlet velocity.(2)The one-way fluid-structure interaction calculation is carried out for the above three high-pressure manifold systems under the condition of constant inlet velocity using ANSYS Workbench software.The results show that the natural frequencies of the three manifold systems all increase with the increase of the order.With the increase of the number of elbows,the natural frequency of each order of the three manifold systems decreases.The fatigue life of the high-pressure manifold system with four elbows is analyzed,and the number of times of alternating stress that the manifold can bear due to fatigue until failure is 9.4052×10~5 times.Two-way fluid-structure interaction calculation is carried out for the vibration of a high-pressure manifold system with four elbows under the condition of periodic inlet velocity.The results show that,compared with the calculation of one-way fluid-structure interaction,the main excitation frequency is changed from 44.73 Hz to 30.75 Hz,and the maximum amplitude is changed from 4.06mm to 6.30 mm.(3)To prevent resonance between high pressure manifold and tee during fracturing,taking the pulsating flow of the triplex fracturing pump in actual operation as the inlet condition,the ground high-pressure manifold system is calculated,and it is found that the vibration frequency of the tee is 30 Hz when the system is connected with the fracturing pump,elbow and tee,which is closed to the above 30.75 Hz.Therefore,it should be noted that the manifold should be supported and restrained to avoid the vicinity of 30.75 Hz.