旋转阀式钻井液压力信号发生器的基础研究

Currently, the low downhole data transmission rate of domestic measurement while drilling (MWD) system couldn't satisfy the demand of high data flow rate in the increasing development of the steerable drilling technology. Increasing the transmission rate of downhole data has practical significance in realizing high efficiency drilling and exploitation of thin reservoir. The foreign practical application shows that the downhole information telemetry system based on the drilling fluid continuous pressure wave technology can increase the downhole data transmission rate greatly. However, the related technologies haven't been grasped in China. The key of the drilling fluid continuous pressure wave downhole information telemetry system is drilling fluid pressure signal generator using rotary valve and the key problems in its development are orifice structure design and rotating speed control of rotary valve. An applied basic research will be carried out in the research project aiming at solving the above key scientific problems in the engineering research of drilling fluid pressure signal generator of rotary valve. Through the research, a design theory of the rotary valve orifice structure will be built on the basis of mathematic modeling of the drilling fluid pressure wave and related analysis and a special rotating speed control strategy of rotary valve will be proposed by theoretical analysis of the rotary valve resistive torque. The research result will offer some theoretical solutions to the key problems and provide theoretical guidance to the engineering research, thereby, can accelerate the development of drilling fluid continuous pressure wave downhole information telemetry system in China and satisfy the urgent demand of high downhole data transmission rate in modern drilling.

目前国内随钻测量系统的数据传输速率较低，无法满足导向钻井技术的日益发展对高数据流量的需求；提高井下数据传输速率，对于实现高效钻井及薄油层的开采有着较大的实际意义。国外的实际应用表明，采用钻井液连续压力波技术的井下信息遥测系统，可以大幅提高井下数据的传输速率，但相关技术国内还未掌握。钻井液连续压力波井下信息遥测系统的核心是采用旋转阀的钻井液压力信号发生器，其研制过程中需要解决的关键问题是旋转阀阀口的结构设计及旋转阀的转速控制。本项目针对旋转阀式钻井液压力信号发生器工程研究中遇到的上述关键问题，开展应用基础研究，通过钻井液压力波的数学建模与分析，建立旋转阀阀口结构的设计理论；通过旋转阀阻力矩的理论分析，建立旋转阀转速的特殊控制策略，从理论上提供解决这些关键问题的方法，起到对工程研究的理论指导作用，以加快国内钻井液连续压力波井下信息遥测系统的研制，满足现代钻井技术对井下数据高传输速率的迫切需求。

钻井液连续压力波技术是一种通过钻井液信道上传井下信息的高速数据传输技术，基于钻井液连续压力波技术的井下信息遥测系统的核心是采用旋转阀的钻井液压力信号发生器，其研制过程中需要解决的关键问题是旋转阀阀口的结构设计及旋转阀的转速控制。本项目针对旋转阀式钻井液压力信号发生器研发中遇到的上述关键问题，开展了相应的基础研究。通过进行钻井液压力波的机理研究及数学建模；旋转阀定、转子孔口形状的计算模型及设计准则的建立；阀口处压力变化的仿真分析；旋转阀的信号特性分析及旋转阀式压力信号发生器的性能评价研究；旋转阀转子负载力矩的数学建模；旋转阀负载力矩的非线性补偿方法研究；旋转阀转速的闭环控制模型建立及响应的理论分析；干扰影响下旋转阀转速的理论与仿真分析等涉及旋转阀式钻井液压力信号发生器有关机理及方法的系统研究，得到一些重要研究结果。（1）研究表明，钻井液压力信号为钻井液通过旋转阀可变阀孔时的非稳定流动产生的流体惯性压力，这一研究结果的科学意义在于不但可以合理地解释钻井液压力波的产生机理及传播特性并据此建立钻井液压力信号的数学模型，而且可以将流体惯性压力概念用于井控时防喷器产生的瞬态压力影响研究；（2）根据理论计算和数学分析建立了旋转阀阀口结构设计准则；（3）揭示了旋转阀调制钻井液压力过程中信号幅度的变化规律，表明了钻井液压力相移键控信号为变幅度的载波相移信号，对于钻井液连续压力波信号的分析与处理具有重大意义；（4）揭示了旋转阀负载力矩在钻井液流量和密度影响下随旋转角的非线性变化规律；（5）基于前馈补偿理论对负载力矩的严重非线性进行线性化校正，基于转速暂态分量的衰减控制进行转速闭环控制参数的优选，可以在较大的干扰影响下实现旋转阀转速的快速跟踪控制；（6）基于井下信息传输的误码率分析建立了旋转阀式压力信号发生器的性能评价方法。项目的研究结果可以为旋转阀式钻井液压力信号发生器的工程研究提供理论指导。