耦合钻井液钻柱声波传播特性研究

钻井过程中非常规钻井液的应用,使得随钻数据无法通过传统的钻井液脉冲方式传输,迫切需要更高数据传输速率和受工作环境影响更小的井下随钻无线传输技术。基于钻柱信道的井下信息声波传输技术是较为理想的随钻数据无线传输方式,为给声波传输系统的设计提供理论依据,针对钻柱信道中的声波传播特性进行了研究。研究结果表明:钻柱信道具有通带和阻带相间的梳状滤波器特征,频带分布具有一定的周期性和对称性特征。钻柱结构决定了其信道通阻带的分布情况,随着钻杆根数的增加通带内小谱峰的个数增加,信道传输能力下降,结构尺寸不一致会使通带变窄,声波传输性能下降。

Research on Acoustic Transmitting Characteristics of Drill String Channel Coupled with Drilling Fluids

Traditional wireless MWD telemetry systems such as drilling fluid pulse are limited due to unconventional drilling fluid. Using acoustic waves to transmit downhole information through the drill string is a promising approach to meet the modern drilling technology requirements for low pressure and lost circulation formation. In order to provide theoretica1 basis for the design of acoustic transmission system. The frequency spectrum characteristic of acoustic wave transmission channel of drill string is analyzed by using the finite difference method. A distinctive feature of the drill string character is the presence of passbands and stopbands in the channel. In other words, the drill string acts like a linear comb filter. The distribution of frequency spectrum exhibits periodic and symmetrical property. The results show that frequency band mainly depends on the length of the drill pipe or area of the joints. With the increase of complexity of the structure, the frequency spectrum characteristics deteriorate.