短距离钻杆中声波传输仿真与实验

Simulation and experiment of acoustic wave transmission in short distance drill pipe

摘要:

井下短距离声波通信技术是将近钻头传感器测量的井眼信息传输到随钻测量仪(MWD)的关键。为了探究声波载波信号在短距离钻杆中的传输特性，采用有限元法建立1.28 m长的钻杆模型，对钻杆施加频率为20 Hz，占空比为50%的激振载荷，模拟计算钻杆径向接收点响应和钻杆结构的特征频率，并分析声波在短距离钻杆中的传输特性。结果表明，当钻杆在初始条件下受到激振载荷作用时，钻杆接收点的声波信号整体具有一条呈指数形式衰减的包络曲线，其内部为幅值逐渐衰减的余弦周期信号，并最终稳定在新的平衡位置；当钻杆继续受载荷作用后，声波信号会在之前稳态的基础上继续衰减，最终逐渐衰减并稳定在初始状态，仿真结果及理论分析与实验结果吻合良好，为声波在多钻杆中传输的仿真提供基础模型。

Abstract:

Short distance acoustic communication technology under the oil well is the key to transmitting the borehole information measured by the near-bit sensor to the Measurement While Drilling(MWD). In order to explore the transmission characteristics of the sonic carrier signal in the short-distance drill pipe, the finite element method is adopted to establish a 1.28 m long drill pipe model, and an excitation load with a frequency of 20 Hz and a duty ratio of 50% is applied to the drill pipe to simulate the calculation of the radial receiving point response of the rod and the characteristic frequency of the drill rod structure. The transmission characteristics of the acoustic wave in the short distance drill rod are analyzed as well. The results show that when the drill pipe is subjected to an excitation load under the initial conditions, the acoustic signal at the receiving point of the drill pipe has an enveloping curve that decays exponentially, and its interior is a cosine periodic signal with gradually decreasing amplitude, and finally stable at a new equilibrium position; when the drill pipe continues to be loaded, the acoustic signal will continue to decay on the basis of the previous steady state, and eventually decays and stabilizes in the initial state. The simulation results are in good agreement with theoretical analysis and experimental results. This work can provide basic model for the simulation of sound wave transmission in multiple drill pipes.