音叉密度测井仪的设计

发布时间：2018-05-23 15:48

本文选题：压电音叉 + 流体密度　；参考：《长江大学》2017年硕士论文

【摘要】：井下油、气、水三相混合流体密度是石油勘探开发过程中的重要的决策与评价参数,对于地层资源和产层特性评价提供及时准确的依据。音叉密度测井是国外近几年兴起的一种井下流体密度测量方法,它根据音叉传感器的谐振频率来反映流体密度的变化。其难点主要体现在以下方面:(1)确定音叉传感器的谐振频率,从而计算被测液体密度;(2)实现在线连续测量,实时监测井下流体动态。针对上述问题,论文简要介绍了单个叉体的悬臂梁等效模型,分析了引起音叉传感器振动频率变化的主要原因,研究了被测液体密度与音叉传感谐振频率的关系,从而阐明了音叉式流体密度检测的基本原理,在此基础上,(1)根据实时在线测量的需求,提出了基于音叉传感器闭环自激振荡的设计方案;(2)针对音叉传感器与电路板连接线的分布电容对检测结果的影响,采用了电荷放大器作为前置放大电路;(3)为了进一步提高传感器的抗干扰能力,在频率跟踪电路中加入了解锁模块;(4)为了减小测量误差,采用了等精度测频法,并在FPGA芯片中植入8051软核,实现复杂的数据运算。最后形成了音叉密度测井仪的总体方案,并开发了相应的电子线路。采用上述方案和措施,使音叉传感器分辨率高,电路抗干扰能力强,测量误差小。通过测试,结果表明系统的测量精度、分辨率以及测量范围达到了预定技术指标的要求。综上所述,本文的研究与工作解决了音叉密度测井仪的几个关键的技术难题,开发的系统在0-1.25g/cm3密度范围内有良好的分辨率和较小的测量误差。这对于打破国外垄断市场,研制拥有自主知识产权的音叉密度测井仪具有重要的意义。
[Abstract]:The density of downhole oil, gas and water three-phase mixed fluid is an important decision and evaluation parameter in the process of oil exploration and development, which provides a timely and accurate basis for the evaluation of formation resources and formation characteristics. Tuning fork density logging is a kind of downhole fluid density measurement method developed in recent years. It reflects the change of fluid density according to the resonant frequency of tuning fork sensor. The difficulty lies in the following aspects: 1) determining the resonant frequency of the tuning fork sensor, thus calculating the measured liquid density and realizing on-line continuous measurement and real-time monitoring of the downhole fluid dynamics. Aiming at the above problems, this paper briefly introduces the equivalent model of cantilever beam of a single fork, analyzes the main causes of the vibration frequency change of tuning fork sensor, and studies the relationship between the measured liquid density and the resonant frequency of tuning fork sensor. The basic principle of tuning fork type fluid density measurement is expounded, and on this basis, according to the requirement of real time on-line measurement, A design scheme of closed-loop self-excited oscillation based on tuning fork sensor is proposed. The influence of the distributed capacitance of tuning fork sensor and circuit board connection line on the detection results is discussed. In order to further improve the anti-jamming ability of the sensor, an unlocking module is added to the frequency tracking circuit. In order to reduce the measurement error, the equal precision frequency measurement method is adopted. 8051 soft core is implanted into FPGA chip to realize complex data operation. Finally, the overall scheme of tuning fork density logging tool is formed, and the corresponding electronic circuit is developed. By adopting the above scheme and measures, the tuning fork sensor has high resolution, strong circuit anti-interference ability and low measurement error. The test results show that the measurement accuracy, resolution and measurement range of the system meet the requirements of the predetermined technical indicators. To sum up, the research and work of this paper have solved several key technical problems of the tuning fork density logging tool. The developed system has good resolution and small measurement error in the range of 0-1.25g/cm3 density. This is of great significance for breaking the monopoly of foreign markets and developing a tuning fork density logging tool with independent intellectual property rights.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.83;TP212

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