Numerical analysis and experimental study of fluid return pressure for mud-pulse telemetry

The deep-sea drilling vessel "CHIKYU" is a riser-equipped, dynamically positioned scientific drill ship owned and operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and built for the purpose of scientific research and exploratory expeditions. Advanced measurement-while-drilling (MWD) technology transmits realtime data from the downhole to the upper surface of the vessel using a pressure wave, i.e., a mud pulse, generated with a pressure modulator through the drill string. In this study, a numerical one-dimensional fluid model has been designed and analysis carried out under the assumption of a pressure modulator located within the drill pipe to monitor mud pulse simulations. Also, testing equipment for return pressure wave propagation has also been developed and performance tests carried out to generate return pressure waves from a pressure modulator in order to monitor mud pulse data transmission as compared to simulation results.