【作者】 张晨；

【导师】 孔力；

【作者基本信息】 华中科技大学 ， 检测技术与自动化装置， 2011， 硕士

【摘要】 二维核磁共振测井是在保留传统一维核磁共振测井原有应用的基础上,发展起来的一种先进测井技术。与一维核磁共振测井相比,二维核磁共振测井将孔隙流体中氢核数分布从单一T2驰豫变量拓展到二维核磁共振的两个变量,充分利用了核磁共振观测的信息,提高了仪器辨识流体的准确性和直观程度,打破了一维核磁共振测井的局限性。其中主控系统作为整支仪器的核心,该部分设计的好坏决定了二维核磁共振测井仪的工作性能。本文从二维核磁共振测井原理入手,分析了主控系统在整支测井仪器中的作用,进而根据功能需求对主控系统硬件和软件两方面进行了详细的论述和设计。系统硬件设计部分,以数字信号处理器(DSP)和现场可编程门阵列(FPGA)为控制电路核心,共分为CAN通讯模块、射频信号产生模块、数据采集模块、时序控制模块四大部分。CAN通讯模块负责完成与遥传短节的CAN通讯任务;射频信号产生模块,采用直接数字频率合成(DDS)芯片,实现两路频率和相位精确可调的正弦信号的发射;数据采集模块实现了对模拟回波信号向数字量的转换;时序控制模块,用于产生抗噪能力强的差分时序控制信号。系统软件设计部分,分析了主控系统程序的工作流程,通过FPGA生成了灵活可调的控制时序,并详细论证了同步采集时钟的产生方案。除此之外,在DSP中实现了基于累加平均的数字相敏检波算法(DPSD),该算法具有计算量小、误差低等优点。针对仪器数据交互的需求,论文制定了核磁共振测井仪专用的CAN通讯协议,保证数据能够准确、高速、可靠的传输,满足大数据量传输的需求。最后通过测井、扫频、主刻度三种工作模式的电路实验数据和结果,验证了本文所设计的主控系统已基本满足核磁共振测井仪的工作需求。目前,装有本文所设计主控系统的核磁共振测井仪已经成功在标准实验井测井成功。更多还原

【Abstract】 Two-dimensional nuclear magnetic resonance (2D NMR) logging is an advanced technique in formation evaluation without loss the merits of one-dimensional NMR logging. 2D NMR logging will perform superior to 1D NMR logging in accuracy because it gets more information than T2 distribution. And the performance of the 2D NMR logging instrument depends on the design of the main control system for it is the core part of the whole too.The hardware and software design of the main control system is discussed in detail in this paper based on the analysis of the 2D NMR logging principle and the main board’s function in the apparatus. The system is implemented mainly by Digital Signal Processor (DSP) and Field Programmable Gate Array (FPGA) and could be divided into 4 parts: CAN communication, RF signal generator, data capture and sequence control. The CAN communication module translates data between the main board and the computer. A Direct Digital Synthesis (DDS) chip is adopted in the RF signal generator module to create two orthogonal sine signals whose phases are programmable. Signal capture module converts the signal form analog to digital form. And the sequence control module generates signals to control the whole device. The software is implemented by FPGA and DSP. Nearly all control signals are generated by FPGA and the signal process algorithm-Digital Phase Signal Detection (DPSD) is programmed in DSP. Moreover, the communication protocol is made for the message could be transmitted fast, reliable, correctly.Finally, through the logging, frequency sweep and calibration experiments, the performances of the main control system have been proven to satisfy the requirement of the NMR logging. And the main board designed in this paper been successfully applied in the logging experiment of the standard oil well.更多还原