导向钻井下传信号解算中的取整问题

The rounding problems in rotary steerable drilling system downward signal solving

钻井液负脉冲间隔方式的导向钻井信号下传系统中,需要井下接收装置正确及时地识别以脉宽表示的数位十进制整数码构成下传指令字。在实际钻井工程应用中,井下近钻头的工作环境和实际应用中的信号变形、噪音干扰和计时误差等具体问题给指令的正确解算带来了难度.采用常规的基于以微处理器中定时器为核心的指令求解的方法,需要根据导向钻井液脉宽指令的特点,在取整时需要考虑到信号幅值阈值和脉宽裕量等因素进行处理。适合井下微处理器应用的基于应用信号相似性原理的信号处理和下传指令解算方法,则以不断更新的排量采样数据为标准,逐段比较各固定时间段的排量信号,以确定各位命令码并将其构成指令字。该方法更加适合钻井工程的实际和导向钻井系统的软硬件需求,解决了解算算法中的取整问题,提高了信号识别的可靠性和抗干扰能力。以5位指令字为例的钻井液下传信号传输的现场实验结果证明了该方法的有效性和可行性.

In rotary steerable drilling downward signal system using drilling fluid negative pulse intervals transmission mode, the command word which made composed by several decimal integer codes and expressed by corresponding pulse widths should be recognized accurately and timely by the downhole receiver. It is difficulty to fulfill the task in drilling engineering application, because of the near-bit working environment and the practical problems as signal distortion; noise interference and timing error etc. When conventional method of calculation and rounding is used, the particular treatments should be taken based on features of the steerable drilling downward negative pulse intervals signal, which considering the amplitude thresholds and pulse widths allowance of the signal. A downward signal resolving method and signal processing algorithm suitable for rotary steerable drilling downward signal based on signal similarity is proposed. By comparing rate of flow signals of the fixed time segment by segment using a flow sampling signal updated constantly as the standard, the every code can be affirmed and the command word formed. The method is suitable to well downhole process and has improved the reliability and ability of disturbance rejection for the signal recognition. Field testing results with the command of 5 codes as a example have proved the validity and feasibility of the method.