Research On Surface Detector For Acoustic Telemetry System

The downhole information’s acquisition and processing has very important significance for accurate formation evaluation, reservoir description and development and so on. The dynamic monitoring of production well is an important means of obtaining downhole information. But people discovered that traditional cable transmission of acquiring downhole information was very difficult to satisfy the modern dynamic monitoring requirements because of its complex operation, significant cost and so on; Relative to the cable transmission, the wireless transmission, particularly the acoustic transmission method obtained many domestic and foreign researchers’ attention by its advantages of low cost, simple operation and so on.This article has minutely analyzed acoustic transmission characteristic along the tubing string, namely it has pass band and stop band alternate comb filter structure frequency characteristic in the acoustic transmission process, and the acoustic amplitude approximately obeyes exponential decay law characteristic in pass band. And it has been verified through field experiment. On the basis of theoretical analysis of acoustic transmission along the tubing string, we have designed the ground detector of acoustic telemetry system, it divides into hardware and software two parts:In the hardware aspect, we mainly chose suitable sensor, signal conditioning circuit and data acquisition card for downhole weak acoustic signal’s acquisition through analyzing detection signal’s type, characteristic and so on. Especially minutely analyzed ADXL103and LC0156T two kind of integrated acceleration sensor, and measured and compared their sensitivity and signal-to-noise ratio. Finally, chose the LC0156T to complete weak acoustic signal’s acquisition and processing.The software part is realized based on the virtual instrument’s design idea, using computer and sound card, and combining LabVIEW software. On the basis of commonly used method of weak signal detection, we have proposed time-frequency Joint weak signal detection method based on LabVIEW, and have designed the acoustic telemetry ground detection system using this method. Then, this system has realized downhole acoustic signal’s real-time acquisition and processing.Finally, we have completed the test of the acoustic telemetry ground detection system by the ground simulation experiment and the actual downhole signal detection experiment, and have proven this system’s availability. It can satisfy downhole acoustic signal’s acquisition and processing.