Downhole electromagnetic and mud pulse telemetry apparatus

A method of transmitting downhole measurement data to surface comprising:

• (a) reading downhole measurement data;
• (b) selecting an available telemetry transmission mode from a group consisting of:
• mud pulse (MP)-only telemetry mode, electromagnetic (EM)-only telemetry mode, MP and EM concurrent shared telemetry mode, and MP and EM concurrent confirmation telemetry mode;
• (c) when the MP-only telemetry mode is selected, encoding the measurement data into a first MP telemetry signal and transmitting the first MP telemetry signal to surface,
• (d) when the EM-only mode is selected, encoding the measurement data into a first EM telemetry signal and transmitting the first EM telemetry signal to surface;
• (e) when the concurrent shared telemetry mode is selected, encoding a first selection of the measurement data into a second MP telemetry signal and a second selection of the measurement data into a second EM telemetry signal, and transmitting the second MP and EM telemetry signals to surface;
• and
• (f) when the concurrent confirmation telemetry mode is selected, encoding the same measurement data into a third MP telemetry signal and into a third EM telemetry signal;
• and transmitting the third MP and EM telemetry signals to surface ;
• and
• wherein the measurement data comprises gamma, shock, vibration and toolface data and when the concurrent shared telemetry mode is selected, the method further comprises encoding the gamma, shock and vibration data into the second EM telemetry signal and encoding the toolface data into the second MP telemetry signal;
• or, encoding the gamma and toolface data on the second EM telemetry signal and encoding the shock and vibration data on the second MP teletry signal;
• or, encoding the gamma data on the second EM telemetry signal, and encoding the shock, vibration and toolface data on the second MP telemetry signal.