Signal attenuation simulation of acoustic telemetry in directional drilling
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Acoustic telemetry is preferred to conventional mud pulse telemetry because of its faster data transmission rate. However, acoustic telemetry requires a repeater for signal amplification because of the large signal attenuation that depends on the depth of drilling, which makes the system complicated and expensive. To improve communication performance by overcoming signal attenuation, developing a simulator capable of simulating the signal is necessary. However, the existing research models are limited to certain types of wave equation models that do not reflect the signal attenuation. In this study, the viscous dissipation term is added to the existing model, assuming that viscous friction caused by the relative movement between the mud and the drill string vibrating by acoustic waves is the main factor causing acoustic energy dissipation. A transient numerical model has been developed and tuned to simulate the attenuation rate reported in Drumheller's experiment on depth-dependent signal attenuation. The model shows that mud viscous flow is a major contribution to acoustic energy dissipation. The model developed in this study can be applied as a virtual simulator to develop various communication algorithms, as it can simulate signal attenuations at various drilling sites.
KeywordsAcoustic telemetry Directional drilling Mud pulse telemetry Wave equation
Speed of sound, m/s
Young’s modulus, N/m2
Mass coordinate, kg
Mass of segment, kg
Axial length segment, m
Coordinate normal to pipe surface, m
Acoustic impedance, kg/s
Dynamic viscosity, cP
Kinematic viscosity, m2/s
Normal stress, N/m2
Shear stress, N/m2
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This work was supported by a grant from the Korea Agency for Infrastructure Technology Advancement funded by the Ministry of Land, Infrastructure, and Transport (17IFIPB133624-01, “Study on direction control of hybrid directional mud motor and its performance in simulation”).
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