Research On Cableless Signal Transmission Method Of Oil Production And Water Injection Well Based On Acoustic Wave

In the process of oil and gas production,the realization of two-way information transmission between the downhole and the ground is of great significance for accurate and timely acquisition of downhole operating condition information,accurate control of downhole tools in oil and water wells,and refined oil and gas production.The purpose of this article is to explore the use of oil and water well downhole tubing strings as signal transmission channels and sound waves as carrier waves to achieve two-way data transmission between downhole and the ground.In this paper,two theoretical methods for calculating the acoustic transmission characteristics of tubing string structures are studied respectively,the finite difference method and the transfer matrix method,and the actual calculation results of the two methods are compared and confirmed.The calculation results show that in the ideal tubing string model,the acoustic signal presents the characteristics of a comb filter with alternating passbands and stopbands.Among the commonly used oil pipes of different sizes,the frequency band distribution near the low frequency band has a small difference,and the passband bandwidth is about 250 Hz,and one frequency band can be used in practical applications.The transfer matrix method is used to calculate the tubing string structure with downhole tools.As a result,the sound wave transmission effect is reduced,the passband bandwidth is narrowed,and a passband is divided into several smaller passbands.The greater the number of installations,the greater the impact on sound wave transmission.Through calculation,it is believed that the frequency points that can obtain better transmission effects for commonly used tubing strings are:130 Hz,400 Hz,660 Hz,920 Hz,1190 Hz.The structure of the half-wavelength sandwich piezoelectric ceramic transducer matched with the tubing string is designed,and it is divided into two parts:the quarter-wavelength concentrator before the node and the quarter-wavelength transducer vibrator behind the node.According to the vibration equation on any variable cross-section body,the frequency equation of two parts is derived for structural size design,and at the same time,the front and rear vibration velocity ratios of different structures are derived to judge the design result of the transducer.Aiming at the fixed resonance frequency of 1200 Hz,according to the downhole space size characteristics of oil and water wells,specific structural size calculations have been made for the transducers of the two structures.The results show that the smaller the length of the piezoelectric ceramic stack and the larger the length of the small end of the concentrator,the better the working efficiency of the transducer.Through comparison,it is found that the conical concentrator has better usability.The structure and performance of the two different types of transducers were analyzed by finite element analysis using ANSYS.The analysis results show that at the resonance frequency,the transducer has a good vibration shape,only vibrating along the axial direction,and the radial vibration is basically negligible,which satisfies the use of the tubing string structure in oil and water wells,and verifies the feasibility of the theoretical design method.The comparison of the results shows that the conical concentrator is a better structural design.A sound wave signal transmission experiment system was established,and experiments were designed to study the propagation characteristics of sound wave signals in the tubing string.The experimental results of the shock signal show the characteristics of the comb filter in the periodic tubing string structure.The continuous sinusoidal signal experiment obtained the results of the acoustic wave transmission characteristics in accordance with the theoretical calculation,and the acoustic wave frequency with higher transmission efficiency was selected.In the information transmission experiment,two frequency points in the passband were selected as the carrier for the experiment,and the normal transmission of the signal was realized.It is calculated that the signal transmission rate is at least 10 bit·s^-1,which verifies the feasibility of the frequency in the passband in practical applications.