Design Analysis And Feasibility Study Of Acoustic Telemetry System

In the process of oil and gas production,it is essential to know the downhole information in real time so the working way of the equipment can be controlled.A wide bandwidth,real-time,reliable underground data transmission mode is essential in the process of drilling,well completion,oil production,artificial lifting,fracturing,water injection,oil and gas well testing.In the current research of signal transmission technology,the sound wave transmission is widely concerned by the whole world for its low cost and high feasibility.The previous design of acoustic signal transmission system used the drill pipe wall as the channel,but the periodic structure of it makes the signal of some frequency attenuate completely,which limits the application scope of the system.With the development of technology,coiled tubing is used in most oil fields for production,which makes it possible to use continuous media for signal transmission.Therefore,in this paper,the coiled tubing is taken as the research object,the acoustic transmission characteristics of the tubing are studied,and the acoustic signal receiving device is designed,on this basis,a new type of acoustic signal transmission system can be developed to improve the signal transmission.The main research work includes:(1)Based on the Donnell equation,the characteristics of acoustic propagation in oil pipe wall are studied.In this part,the propagation mode of acoustic wave in the pipe wall is analyzed.With the vibration equation of the tube wall under the condition of solid-liquid coupling,the resonance frequency of the tube can be obtained.The acoustic attenuation characteristics are studied and the calculation formulas of the main attenuation modes are established.(2)Based on the theory of acoustic propagation in the first part,the acoustic propagation in the tubing wall is simulated by the finite element analysis software COMSOL.By setting reasonable boundary conditions,the sound transmission diagram of oil pipe under different sound source excitation is obtained.The effect of the welding seam on the acoustic wave transmission is examined by comparing the pressure contour of the pipe with weld and without weld.(3)Based on the data of finite element simulation results,the receiving device for sound wave is designed.In this part,the basic information of Helmholtz amplifier and optical fiber sensor is introduced,and the electro acoustic analogy method is used to calculate the influence of different size parameters on amplifier's resonance frequency,the amplifier size of some specific frequency is calculated so that we can use COMSOL to simulate and verify the theory.