Laboratory investigations of a hybrid mud pulse telemetry (HMPT) - A new approach for speeding up the transmitting of MWD/LWD data in deep boreholes

For continuous monitoring and controlling of the well path during the drilling process, the bottom hole assembly is equipped with sophisticated sensors, which collect geological and directional data. The driller at the surface requires the information for decision making, and therefore, the acquired data must be processed and transmitted to the surface in real time. The most common method for transmitting the data in deep boreholes is the so called mud pulse telemetry. The mud pulse telemetry uses the flowing drilling mud inside the drill string as a transmitting channel, whereby the information is transmitted either in baseband or in passband as coded pressure pulses or waves. The main disadvantage of the mud pulse telemetry is its low transmission data rate. The achieved data rate, in practice usually about 10 bits per second, is very low compared to the amount of raw data measured downhole. At the Institute of Drilling Engineering and Fluid Mining of the Technical University Bergakademie Freiberg, Germany, a special focus has been given to develop new ways and novel approaches for speeding up the mud pulse telemetry systems. One of the most recent developed approaches is the hybrid mud pulse telemetry system. According to the new approach, the data will be transmitted simultaneously in base- and passband. Each downhole generated pressure signal transmits two different information words simultaneously, and therefore, the receiver end at the surface must be modified correspondingly. At the receiver end, a special signal processing method is developed and applied to extract the baseband-information and the passband-information from the main received pressure signal. The paper describes the developed concept for a hybrid mud pulse telemetry system and presents the investigation results. Also, a special data management method for the data transmission using the hybrid mud pulse telemetry system is developed and presented in this paper.