井下钻井液往复控制连续波信号的产生特性研究

Practice proves that the downhole data transmission rate by continuous wave of drilling fluid is higher than which by pulse wave. However, the traditional continuous wave signal generator produced by rotary valve driven by motor has some main problems, such as poor detection accuracy of valve opening position, large demand for electricity, difficult to speed control, which is greatly restricted the improvement of data transmission rate. Therefore, the purpose of this project is to study the generation methods and properties of continuous wave signal generated by reciprocating motion of drilling fluid, and to provide supports for developing new technology of downhole high-speed data transmission. The key research points include:1) Taken multiphase fluid mechanics as the theoretical guidance, figure out the characteristic curve between valve inlet pressure and flow rate in drilling fluid medium and the mechanical motion characteristic curve of driver element driven by drilling fluid with experimental method, and establish their mathematical expressions ; 2) On this basis, determine downhole data transmission objectives, taken generation of sine continuous wave as the goal, establish and improve the nonlinear state control equation of drilling fluid pressure wave signal generator; 3) Research the calculation method of nonlinear state control equation established, design calculation software, and take simulation analysis on the quality of drilling fluid continuous wave signal and the main influence factors; 4) According to the analysis results, determine the main structural parameters and overall scheme of continuous wave signal generator, process and manufacture experimental prototype, carry out simulation experimental to study the signal characteristics, and establish a method for comprehensive performance evaluation of this kind of signal generator at last.

实践证明，钻井液压力连续波井下数据传输率比脉冲波高。但研究表明，传统的电机驱动转阀式连续波信号发生器阀口位置检测准确度差、供电量大、调速困难，极大地限制了数据传输率的提高。因此，本课题拟研究钻井液流体往复运动连续波信号的产生特性，为开发井下数据高速上传技术提供基础。研究要点包括：1）以多相流流体力学为指导，实验研究钻井液介质阀口压力流量特性曲线，实验研究钻井液驱动元件的机械运动特性曲线，建立数学表达式；2）在此基础上，确定井下数据传输指标，以正弦连续波的产生为目标，从状态控制理论出发，建立并完善钻井液压力波信号发生器的非线性状态方程；3）研究信号发生器非线性状态方程计算方法，设计计算软件，仿真分析钻井液连续波信号的品质影响因素及规律；4）根据分析研究结果，确定连续波信号发生器的主要参数、总体方案,设计加工原理样机，模拟实验研究其信号特性，并在此基础上，建立该类信号发生器综合性能评价方法。

针对传统电机驱动转阀式连续波信号发生器存在的阀口位置检测准确度差、供电量大、调速困难等限制数据高效传输的问题，项目提出采用往复运动式的钻井液流体连续波信号发生器结构，并对其信号产生特性展开了研究。以流体力学为指导，并结合往复式信号发生器结构特点，采用理论分析、数值模拟及模拟实验相结合的研究方法，揭示了钻井液信号发生器阀口压力流量特性关系，并建立了钻井液驱动元件的机械运动特性方程；从状态控制理论出发，对连续波信号发生器控制方法进行了理论研究；采用数值模拟软件，对液压往复运动控制机构的受力进行了仿真，揭示了影响钻井液连续波信号的因素及规律；在此基础上设计了信号发生器综合性能地面模拟实验，实验研究了往复阀口的流量压力特性关系，综合验证了信号发生器的性能，实验装置为往复式连续波信号发生器的设计及综合性能评价提供一个研究平台，实验结果对研究井下连续波信号产生特性具有重要的指导意义。