Acoustic telemetry system for oil wells utilizing self generated noise

Abstract

An acoustic communication method and system are disclosed for transmitting information through a well-bore drill string by using the acoustic noise inherently generated in the drill string by drilling operations as a 'carrier' propagated therealong to be modulated by the information to be transmitted. In the drilling of wells, the action of the drill tool on the bottom of the bore hole creates acoustic noise within the drill string. Other suitable sources of 'noise' are often present during 'drilling operations', as broadly defined, even while bore drilling, as such, is suspended. This noise usually consists both of wide-band continuous acoustic energy and of narrow spectral lines of acoustic energy and is usually present in a variety of acoustic modes such as longitudinal and torsional acoustic waves. The detailed characteristic of this acoustic noise depends on the type of drill tool used, the drilling speed and the type of formation being drilled. When this inherently generated noise is modulated by an information containing signal at a signal-transmitting station, acoustic communication of information is possible while drilling is in progress, or, in some cases, while drilling as such is suspended. The communication occurs between the transmitting station and a signal-receiving station spaced along the drill string, using the intervening length of drill string between the signal-transmitting and signal-receiving stations as an acoustic transmission channel.