Abstract: A torsional acoustic wave generator for use in an acoustic drill-string telemetry system, the generator having a reaction mass rotatably mounted near the lower end of a drill string, and a fluid coupling for generating a torque between the reaction mass and the drill string and thereby applying a sudden torsional pulse to the drill string. In the disclosed embodiment of the invention, the fluid coupling comprises a number of chambers rigidly connected to the reaction mass, an equal number of vanes rigidly connected to the drill string and disposed in the cylinders, and a mud control valve for selectively directing drilling mud into the chambers to generate a torque between the chambers and the vanes, and thereby apply to the drill string a torsional pulse that is independent of such factors as drill-string angular velocity.

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.