三维声波测井仪近探头高精度测量电路设计

发布时间：2018-10-09 17:06

【摘要】：随着测井技术的发展,三维声波测井已经成为一种重要的测井方法,其测量原理是利用声波在不同介质中传播,它的幅度和频率等物理特性会产生不同变化的特点来研究钻井的地质剖面,判断固井质量。在实际的测井过程中,井下高温环境非常复杂,噪声干扰严重,待测量的声波信号很微弱而难以被检测解析,因此研发出高精度的井下测量电路十分必要,这样才能适应未来测井对精度要求越来越高的发展趋势。三维声波测井仪能够同时测量井周多个方位的声波信号,从而提供地层径向、轴向及周向三维立体地质构造信息。本文首先介绍了三维声波测井仪的总体结构、测井原理及测井过程;然后根据测井的需求设计了高精度测量电路,主要包含前置调理电路和模数转换电路。三维声波测井仪高精度测量电路是以“ADC+FPGA”为硬件架构,低噪声的前置调理电路实现对地层反射回来的微弱声波信号的放大、滤波等预处理功能,主要涉及的内容有电荷放大电路设计、程控增益设计、高通滤波电路设计;sigma-delta型高精度模数转换器利用高采样速率换取高采样精度的原理,把输入的模拟信号转换为易于存储和传输的数字信号;串行数据的高速传输技术实现测井数据的实时传输,其采用的低电压差分传输技术能有效地减小数据传输过程中共模噪声的干扰。本电路使用基于Verilog的硬件描述语言来实现FPGA的基本功能,包括ADC采样流程的控制、测井数据的存储和传输。最后,本文通过一系列的实验验证了高精度测量电路设计的正确性和测井仪工作的稳定性,其中水槽实验验证了三维声波测井仪功能的正确性,高温实验验证了系统的高温稳定性。此外,通过导出模数转换器输出的大量样本数据,对其进行处理计算,得到模数转换器的有效位数,从而验证了所设计的高精度测量电路达到预期的精度目标。
[Abstract]:With the development of logging technology, 3D acoustic logging has become an important logging method. Its physical characteristics such as amplitude and frequency will produce different characteristics to study the geological profile of drilling and to judge the cementing quality. In the actual logging process, the underground high temperature environment is very complex, the noise interference is serious, the acoustic signal to be measured is very weak and difficult to be detected and analyzed, so it is necessary to develop a high precision downhole measurement circuit. Only in this way can we adapt to the developing trend of higher and higher precision of logging in the future. The 3D acoustic logging tool can simultaneously measure the acoustic signals in several directions around the well, thus providing the three-dimensional geological structure information of radial, axial and circumferential directions. This paper first introduces the overall structure, logging principle and logging process of 3D acoustic logging tool, and then designs a high-precision measuring circuit according to the requirements of logging, which mainly includes preconditioning circuit and analog-to-digital conversion circuit. The high precision measuring circuit of 3D acoustic logging tool is based on "ADC FPGA" as hardware structure. The preconditioning circuit with low noise realizes the preprocessing functions such as amplifying and filtering weak acoustic signals reflected from formation, etc. The main contents involved include the design of charge amplifier circuit, the design of program-controlled gain, the design of high-pass filter circuit and the principle of using high sampling rate to exchange high sampling precision for high precision ADC. The input analog signal is converted into a digital signal which is easy to store and transmit, and the high-speed transmission technology of serial data realizes the real-time transmission of logging data. The low voltage differential transmission technique can effectively reduce the common-mode noise interference during data transmission. This circuit uses the hardware description language based on Verilog to realize the basic functions of FPGA, including the control of ADC sampling flow, the storage and transmission of logging data. Finally, a series of experiments are carried out to verify the correctness of the design of the high-precision measuring circuit and the stability of the logging tool, and the validity of the function of the three-dimensional acoustic logging tool is verified by the flume experiment. The high temperature stability of the system is verified by high temperature experiment. In addition, a large number of sample data are derived from the analog-to-digital converter and processed and calculated, and the effective bits of the ADC are obtained, which verifies that the designed high-precision measuring circuit achieves the desired accuracy target.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.83

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