The propagation of sound waves in drill strings

Deep wells are commonly drilled while steering the drill bit. The steering process is completely controlled by the drilling‐rig operator. A key element of this procedure is the measurement and communication of navigation information from the bottom of the well to the operator. Pressure pulses modulated onto the flow of the drill fluid are now employed in some cases to communicate this information. However, data rates are only a few binary bits per second with this method. This drastically limits the quantity of data available to the operator. As an alternative method, elastic waves generated within the steel drill string can be used as a carrier signal to transmit data. The drill string is commonly assembled from 10‐m segments of threaded pipe and forms a periodic structure. The elastic wavelengths of interest are shorter than this periodic length. Consequently, these waves undergo significant dispersion. This paper presents new data for the propagation of elastic waves in a 2‐km drill string. The influen...