利用水声通信原理解决随钻数据传输问题

Solving the problem of data transmission while drilling based on underwater acoustic communication principle

在现有随钻数据传输技术的基础上,首次提出利用水声通信原理解决随钻数据传输难题的设想。首先选择钻杆内的钻井液作为水声通讯信道,并将其简化为一维、有限长、均匀、等截面波导。根据理想流体的小振幅波方程,讨论随钻水声信道的截止频率与黏滞力、非线性特性等因素的影响,确定通讯系统的频率、功率与传输距离等基本参数。然后提出建立随钻信道的分段、时变、分布式模型思路,适应信道结构分段变化、钻井深度随时间增加、信道参数时变分布等特点,仿真分析随钻水声信道的传输特性。最后通过定量计算水基钻井液、油基钻井液对水声信号的衰减,提出通过相控阵技术增强信源功率,提高信源质量与信宿检测能力。结果表明:利用水声通信原理解决随钻数据的高速传输问题是可行的,有望使随钻数据传输技术取得突破性进展,彻底解决随钻数据传输问题;结合钻井工程参数,可以选用的水声信号频率大于2 kHz,有效地避开了钻井过程噪声,有利于随钻信号提取;现有水声换能器、传感器可以满足3 000 m以内的随钻通信需求。

After a brief introduction of measurement-while-drilling(MWD) and available wireless MWD technology, a new proposal was put forward to solve the problems of high-speed data transmission while drilling based on underwater acoustic communication principles. Firstly, drilling fluid in the pipe was selected as the communication channel, which was simplified to a one-dimensional, finite length, uniform, equal section waveguide. Based on the basic equation for small amplitude waves of ideal fluid, several properties of the channel were discussed, including the cut-off frequency of mud channel, the effect of viscous force and nonlinear factors.This lays a foundation for the parameters determination of MWD system, such as acoustic carrier frequency, required power and attainable distance. A proposal of creating a piecewise, time-varying, distributed model for real-time channel was then presented to simulate the channel properties of data transmission, which adapts to variations of drilling fluid channel, such as the increase of drilling depth, the variation and displacement of fluid density and viscosity with increasing borehole temperature and pressure.. Thirdly the attenuation results of acoustic signal in mud channel with water-based and oil-based drilling fluid were calculated,and the methods of enhancing acoustic source power and improving sink detection sensitivity based on phased array were explained. All of the results show that this proposal is feasible, and a breakthrough of MWD technology is expected to be made which solves the problem of MWD thoroughly. The optional low frequency limit is greater than 2 kHz based on the existing drilling engineering parameters, far beyond the range of process noise and therefore favorable for useful signal extraction. This makes the minimum communication requirement and makes it possible for drilling longer than 3000 meters based on existing acoustic transducers and sensors.