Digitally transmitting well logging information - using sync. word generator located in logging tool and cable drive for transmission uphole to phase decoder

摘要

A data transmission system for a well logging system having a logging tool logging a borehole traversing an earth formation comprises a sync word generator located in the tool. The generator periodically provides a predetermined digital signal corresponding to =1 sync word. A phase encoder in the tool receives serial digital information related to the earth formation and the sync words and provides a signal corresponding to the data and the sync word. A network provides the phase encoder signal to a cable for transmission uphole and receipt by a phase decoder at the surface for decoding. An output circuit converts the serial digital signal to parallel digital signals corresponding to the data information and sync words. The use of a parallel to serial converter permits encoding of parallel signals received downhole. The serial data signal is encoded so that the changing of the amplitude conveys the information rather than the amplitude. The digital signals are then decoded at the surface to provide a parallel digital output.