Finite Element Analysis Of Acoustic Transmission Model Of Drill Pipe

The steering drilling tools is the core of rotary steering drilling system,in which borehole information from the near-bit sensors is transmitted to the surface monitoring platform via the LWD(Logging While Drilling).There are the relative rotation and the collision between the servo platform and the borehole wall,so that LWD system can not connect the electronic warehouse directly.And the acoustic data transmission via the drill pipe is proposed here to provide a wireless communication method with simple structure,low cost,high adaptability.Aiming at the basic model,the acoustic transmission behavior in the drill pipe is researched via three steps: theoretical formula,simulation calculation and experiment.At first,the theory formula of the acoustic oscillatory is deduced,and its transmission behaviors in solid material are studied.And then the steady-state reponse of the test platform,the structural damping of drill pipe,and the acoustic transmission behavior in the short drill pipe are analyzed according to the parameter of the test platform.The acoustic transmission model is built according to the actual parameter of the short drill pipe in the experimental equipment,and simulated with a multi-physics coupling finite-element simulation software,and the acoustic transmission behavior is analyzed via the results of simulation.The proof experiment aims to compare the simulation with the measurement.The test platform consists of a short drill pipe and other instruments,such as a power supply,an acceleration meter,a signal generator,a oscilloscope,and so on.The results show that the envelope of acoustic signal at the receiving point shows an exponential attenuation curve and stabilizes at a new equilibrium point gradually when the load acts on the short drill pipe.And then the wave will attenuate to the initial state.This phenomenon is in accordance with the theoretical calculation.It is effective for acoustic data transmission by avoiding the frequency near to the characteristic frequency of the drill pipe.