Research On Detection Technology Of Downhole Acoustic Transmission Signal

It’s significant for evaluating formation accurately, reservoir description and development to the acquisition and processing of down-hole information. But people discovered that traditional cable transmission of acquiring downhole information was very difficult to satisfy the modem 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. So the new signal detection method for dynamic monitoring technology optimizing the production Wells has the very vital significanceThis 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 obeys exponential decay law characteristic in pass band. And to determine the optimal frequency of sound wave transmission, Also analyzed the causes of acoustic noise in the process of transmission and features. And it has been verified through field experiment.On the basis of theoretical analysis of acoustic transmission along the tubing string,we have designed Underground weak acoustic signal detection method, the method of the research mainly divided into two parts:hardware and softwareIn the hardware aspect,we mainly chose suitable And to determine the optimal frequency of sound wave transmission sensor, signal conditioning circuit and data acquisition card for downhole weak acoustic signal acquisition through analyzing detection signal type, characteristic and so on. Especially minutely analyzed LC0130T and LC0156T two kind of integrated acceleration sensor, and measured and compared their sensitivity and signal to noise ratio. Finally, choosing the LC0130T and24signal sampling card MPS-080102complete weak acoustic signal acquisition and processing.The software part is realized based on the virtual instrument design idea, using computer and sound card, and combining Lab VIEW software. On the basis of commonly used method of weak signal detection, we have proposed time—frequency Joint weak signal detection method based on Lab VIEW and have designed the acoustic telemetry ground detection system using this method．Then，this method has realized downhole acoustic signal real-timeacquisition and processing.