Research On The Excitation And Propagation Characteristics Of Elastic Waves Under The Impact Of Sand On The Wellhead Pipe Wall

Sand production in oil and gas wells is one of the problems that need to be faced in the process of oil and gas resource exploitation.Sand production monitoring technology is a key technology to help the oil and gas producers formulate production plans and coordinate production schedules.It can provide production staff with real-time,qualitative and even quantitative information reflecting the sand production of production wells to ensure the optimality of production plans.Aiming at the problem of sand production monitoring outside the wellhead pipe,the model of sand impacting on the wellhead pipe wall and the excitation and propagation characteristics of elastic waves in the near field of pipe wall medium,the adaptive sand production calculation model based on the principle of near-field beam focusing,and the corresponding multi-channel data acquisition solution are researched in this paper.The basic principle of ultrasonic monitoring of sand production from gas wells was presented firstly,and the excitation and propagation characteristics of elastic waves under concentrated forces were analyzed by analytical methods to guide the establishment of numerical analysis model.A gas-solid-gas stratified cylindrical medium model was established in the COMSOL software.A qualitative and quantitative research on the propagation characteristics of the elastic waves in the pipe wall medium was carried out where sand impact is emulated by concentrated force and corresponding detection points were set in the pipe wall medium according to the problem to be researched.An adaptive sand output calculation model based on the principle of beam focusing concluded from above research was established.Then,the data buffering and transmission architecture of the multi-channel data acquisition system required for the model experiment verification was optimized by solving problems of the adaptive signal amplitude triggering and the continuous data stream buffering.The data throughput rate of optimized multi-channel signal acquisition board is 640 Mbps.Finally,a gas-well sand-production emulation experiment was carried out,the multi-channel signal acquisition board was used to collect the elastic wave signal of the pipe wall under impact of gas-sand two-phase flow,and the performance of the adaptive sand production calculation model was analyzed aiming at the linearity between the actual sand output and the monitored sand output.Theoretical analysis and numerical simulation results show that the spectral characteristics of the elastic wave signal excited by the impact of sand on the pipe wall is related to the radius of sand and the impact velocity.In the near field of the impact point,the impact direction of the sand affects the amplitude of signal received at the detection point,the distance of the impact point to each detection point affects the time delay between the received waveforms at the detection point.The emulated experiment results show that the adaptive sand production calculation model can effectively improve the linearity between the monitored value and actual value of sand production in comparison with the single-element sand production calculation model.Combined with the pre-calibration and data regression analysis late,adaptive sand production calculation model can effectively improve the accuracy of sand production inversion.