核磁共振测井脉冲序列研究及实现

发布时间：2019-03-07 10:30

【摘要】：在核磁共振(NMR)测井中,外部磁场和脉冲激励是产生核磁共振现象、激发地层孔隙流体回波信号的重要条件。脉冲序列的类型直接决定了测量的参数类型和参数的维度,在一定程度上还限定了测井观测模式以及测井的速度。脉冲序列在时序、相位上的严格性关系到回波信号的质量与反演的质量。随着核磁共振测井技术的进步,目前已经出现了多种基于核磁共振技术的测井仪器。然而由于缺乏统一标准和通用性,序列发生器的重复设计给新型仪器的研发带来额外的时间成本和技术成本。需要设计一种标准化的、可灵活配置的通用型序列发生器来满足不同需求。本文分析了脉冲激励在核磁共振技术中作用,列举了多种适用于核磁共振测井的传统的脉冲序列以及一些特殊类型脉冲序列的设计原理。在总结了多种脉冲序列共性特征的基础上,提出基于“三窗口”划分方法来实现脉冲序列,提出了一种通用型脉冲序列发生器的总体逻辑设计方案。关键逻辑模块及其工作方式给出了详细说明。给出了逻辑综合的约束说明和脉冲序列的仿真结果。在可编程逻辑器件上对该方案进行了验证和实现。最后在实验室条件下,测试了该脉冲序列发生器在一维核磁共振测井仪器和二维核磁共振测井仪器上的应用效果。仿真结果初步验证了该序列发生器可通过简单配置生成不同类型脉冲序列的能力。实验室的测试结果验证了该序列发生器在不同类型核磁仪器中的良好工作状态,同时也验证了该序列发生器生成不同序列的能力。所有这些实验的结果也验证了该序列发生器良好的配置能力和功能通用性。
[Abstract]:In nuclear magnetic resonance (NMR) logging, external magnetic field and pulse excitation are important conditions for generating nuclear magnetic resonance and exciting formation pore fluid echo signals. The type of the pulse sequence directly determines the measured parameter type and the dimension of the parameter, and the logging observation mode and the speed of the logging are also limited to a certain extent. The pulse sequence is closely related to the quality of the echo signal and the quality of the inversion at the timing and phase. With the progress of nuclear magnetic resonance logging technology, a variety of well logging instruments based on nuclear magnetic resonance (NMR) technology have been developed. However, due to the lack of the unified standard and the universality, the repeated design of the sequence generator brings additional time cost and technical cost to the R & D of the novel instrument. There is a need to design a standardized, flexible, general-purpose sequence generator to meet different needs. In this paper, the role of pulse excitation in nuclear magnetic resonance (NMR) technology is analyzed, and a variety of traditional pulse sequences for nuclear magnetic resonance logging and the design principle of some special types of pulse sequences are listed. On the basis of summarizing the common features of a variety of pulse sequences, a general logic design scheme of a general-purpose pulse sequence generator is proposed based on the "three-window"-division method to realize the pulse sequence. The key logic modules and their working methods are described in detail. The simulation results of the logic synthesis and the simulation results of the pulse sequence are given. The scheme is verified and implemented on the programmable logic device. Finally, under the laboratory conditions, the effect of the pulse sequence generator on one-dimensional nuclear magnetic resonance logging instrument and two-dimensional nuclear magnetic resonance logging instrument is tested. The simulation results preliminarily verify that the sequence generator can generate different types of pulse sequences by simple configuration. The test results of the laboratory verify the good working state of the sequence generator in different types of nuclear magnetic instruments, and also verify the ability of the sequence generator to generate different sequences. The results of all these experiments also verify the good configuration and functional versatility of the sequence generator.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.81

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