钻柱系统传输特性分析

Analyzing characteristics of signal transmission in drill string system

钻头振动信号的准确提取与恢复是随钻地震勘探的关键问题.传统的提取方法是利用钻柱顶部的参考传感器记录在钻柱中传播的钻头振动信号.因此钻头振动信号在整个钻柱系统中的传输机制是亟需解决.本文基于传递矩阵算法,分析了钻头震源信号在周期性性钻杆中的传输过程,并进一步推导了非周期性钻杆(底部钻具组合,Bottom Hole Assembly,简称BHA)的传输方程,引入了能量比例因子,解决了BHA传输能量高于输入能量的难题,进而构建了整个钻柱系统中钻头震源信号的传输机制,实现了整个钻柱系统中钻头震源信号传输特性的分析.根据实际的钻柱系统模型,通过正演模拟分析了它的综合传输特性.结果显示,钻柱系统的频率滤波效应对钻柱轴向波的传输影响较小,并且其能量损失不会超过20%.本文构建的钻柱系统传输机制能够为钻头震源信号的精准提取提供有力的支撑.

It is a key problem to retrieve the drill-bit signal for Seismic While Drilling(SWD).The conventional approach is to extract the drill-bit signal from the pilot sensors deployed on the top of the drill string.Therefore,it is essential to obtain the propagating mechanism of drill-bit signal in the drill string.Based on the algorithm of transfer matrix,this paper analyzed the propagating rules of drill-bit signals in periodic drill pipe and derived the transmission equation for the drill-bit signal in Bottom Hole Assembly(BHA).To overcome the disadvantage that output energy is bigger than input energy,this equation is modified with an important scale factor.According to this method,the signal propagating in the drill string system was modeling with the real parameters for the drilling.The results show that the frequency filtering of the drill string system has a little impact on the drill-bit signal and its energy become 80%of the raw energy.