【作者】 王琦；

【导师】 于清旭；

【作者基本信息】 大连理工大学 ， 光学工程， 2009， 博士

【摘要】 石油作为不可再生的战略性资源在当今世界尤为重要。而目前石油工业所面临采收率低的问题一直是困扰着石油工业最为核心的问题,此问题的解决是建立在对石油井下一系列物理参数高精度、长期可靠监测基础之上的。然而,石油井下高温、高压、强化学腐蚀、强电磁干扰等一系列极端恶劣环境对传感器的可靠性是一种极大地考验。此外,深井探测信号的传输以及能够实时地测量对石油测井的意义也十分重大。在这种情况下,传统的电子学传感器并不能够完全满足石油测井的需要。以光纤法布里-珀罗干涉型传感器和光纤布拉格光栅传感器为代表的波长调制型光纤传感器由于具有波长编码、抗干扰能力强、长期测量稳定可靠、测量精度高、耐高温高压、抗化学腐蚀等优点,近年来受到石油工业的普遍关注和高度重视。光纤传感测井系统主要包括三个部分:传感器探头、信号传输光纤、信号解调仪。本文对该系统及其在高温、高压油井下长期实时监测应用中所涉及的关键技术进行了系统的、深入的研究,主要包括以下几方面内容。掺铒光纤光源的理论和实验研究。在掺铒光纤放大系统理论模型基础上,对掺铒光纤中光放大的物理过程进行了详细分析,并且对掺铒超荧光光纤光源和可调谐环形腔掺铒光纤激光器进行了数值模拟和实验研究。本文实现了一个输出功率为9.2 mW,覆盖C+L波段的宽谱掺铒超荧光光纤光源,其平均波长为1565.253 nm,平坦区域(平坦度在2.5 dB以内)的谱宽达68 nm(1535～1603 nm)。实现了一种新颖的可调谐环形腔掺铒光纤激光器结构,实现了基于标准C波段掺铒光纤的超宽带可调谐环形腔掺铒光纤激光器,其波长调谐范围首次达到145 nm(1475～1620 nm),覆盖了整个S+C+L波段,输出功率4 mW,激光线宽小于0.03 nm,带宽内边模抑制比大于50 dB。设计并研制出一种基于宽带波长扫描环形腔掺铒光纤激光器的光纤传感查询仪。首先研究了宽带波长扫描环形腔掺铒光纤激光器的动态特性。在此基础上,成功的实现了基于宽带波长扫描环形腔掺铒光纤激光器的光纤传感查询仪。该查询仪采用具有极好的温度稳定性、全光谱范围的光纤F-P标准具对扫描光纤激光器进行实时的波长校准。采用五次非线性拟合方法对滤波器的驱动电压和透射波长进行实时标定,解决了光纤F-P可调谐滤波器调谐电压与透射峰值波长关系的非线性、重复性差和迟滞等问题。因此,该光纤传感查询仪实现了高波长测量精度和分辨率。本文采用HCN气体吸收池作为波长标准对该查询仪的波长测量准确度和分辨率进行了测量,其波长测量分辨率为0.9pm,准确度为±2 pm。利用该查询仪对光纤EFPI/FBG串联复用传感器进行了解调实验,光纤EFPI腔长解调分辨率达到0.025 nm,对应压强分辨率为0.32 kPa;FBG的波长解调分辨率为0.63 pm,对应温度分辨率为0.065℃。由于该系统采用的波长扫描环形腔掺铒光纤激光器具有毫瓦量级的输出功率,对于远距离传感应用具有极好的适应能力。由于该系统采用的波长扫描环形腔掺铒光纤激光器的波长扫描范围达到100 nm以上,使得该查询仪在解调光纤EFPI传感器时更为精确,对FBG传感器解调具有更大的波分复用能力。针对高温高压长期实时测井应用,对光纤压力/温度传感器系统的若干技术问题做了详细的分析并给出相应的解决方案。油气井下压力、温度是油井生产过程监控的重要参数指标。本文通过对光纤EFPI压力传感器的优化设计,并且建立合理的数学模型,利用FBG温度传感器对其进行温度补偿,消除了光纤EFPI压力传感器的温度交叉敏感性。在25℃～300℃温度变化范围内,在压力测量量程0～72 MPa范围内最大偏差小于满量程的±0.025%。在压力测量量程0～102 MPa范围内,其压力测量分辨率达到为1.1 kPa。该测井系统已成功应用于辽河油田高温稠油井的长期温度/压力实时监测,并且即将应用于中海油海上油井的温度/压力监测。更多还原

【Abstract】 Oil as a strategic non-renewable resource is particularly important in the world. Low reservoir recovery is the core problem that oil industry faced. This is largely due to the limited availability of information concerning reservoirs and well operation. Real-time, on-line measurement and monitoring of some key physical parameters as well as their temporal and spatial variations in reservoirs and wells is therefore vitally important. However, a series of extremely harsh environment, such as high temperature, high pressure, strong chemical corrosion and strong electromagnetic interference puts forward higher requirements for the sensor used downhole. In addition, the deep well exploration signal transmission and the ability to real-time measurement of oil well are also very important. In this case, the traditional electronics sensors are not able to fully meet the needs of the oil well logging. The optical fiber sensor based on wavelength demodulation such as fiber extrinsic Fabry-Perot interferometric (EFPI) sensor and fiber Bragg grating (FBG), with merits of wavelength coded, immunity to electromagnetic interference, low drift and high precision, has been attracting more and more attention.Optical fiber sensor system consists of three parts: sensor probe, signal transmission fiber and wavelength interrogator. In this dissertation, according to high temperature and high pressure well logging application, detailed, systematic and intensively study of some key technologies of fiber EFPI/FBG sensor system are presented. The main research works are outlined as followings:Theoretical and Experimental Study of Erbium-doped fiber source is carried out. Based on theoretical model of erbium-doped fiber amplification system, the physical process of amplification in erbium-doped fiber is numerically simulated. And experimental studies on Erbium-doped Superfluorescent Fiber Source (ESFS) and tunable Erbium-doped Fiber Ring Laser (EDFRL) are implemented. In the dissertation, a spectrum flat C+L-band Superfluorescent fiber source with 68 nm (from 1535 to 1603 nm) bandwidth and 9.2 mW output power is obtained. A standard C-band EDF based novel tunable EDFRL structure is realized, whose operating wavelength can be continuously tuned over 145 nm for the first time. The output power of the EDFRL is 4 mW, the 3 dB linewidth is 0.03 nm, and the optical signal to noise ratio is better than 50 dB. An optical fiber sensor interrogator based on wavelength-swept EDFRL (WS-EDFRL) is built up. Firstly, the dynamic characteristics of WS-EDFRL is studied, and then a fiber sensor interrogator based on the WS-EDFRL is successfully constructed. In the system, an etalon with high thermal stability has been used as wavelength reference for calibrating the whole spectrum of fiber laser. A nonlinear fitting algorithm between the applied scan voltage and the transmission wavelength of FFP-TF is adopted for real-time wavelength calibration to eliminate the FFP-TF’s shortcomings such as non-linearity, hysteresis and poor repeatability. A HCN gas absorption cell is used as wavelength references to check the wavelength accuracy and resolution. Experimental results show that the accuracy and resolution of the interrogator is±2 pm and 0.9 pm respectively. In addition, the fiber EFPI/FBG multiplexed sensor is demodulated by this system, fiber EFPI gap length resolution is 0.025 nm, corresponding to 0.32 kPa. FBG wavelength resolution is 0.63 pm, corresponding to 0.065℃. The output power of WS-EDFRL used in this interrogator is in milliwatt order of magnitude, so it shows an excellent ability for long distance sensing applications. It also has advantages for precisely demodulating fiber EFPI sensors and the wavelength multiplexing of FBG sensors.For the application of long term high temperature and high pressure oil well logging, several key technologies on the fiber temperature/pressure sensing system have been investigated. By optimizing the structure of fiber EFPI/FBG multiplexed pressure and temperature sensor the cross-sensitivity of the pressure/temperature sensor is eliminated, and the maximum pressure deviation of less than±0.025% is achieved in pressure gauge range of 0～72 MPa and in temperature variation range between 25℃and 300℃. The resolution of the fiber EFPI pressure sensor is 1.1 kPa in pressure gauge range of 0～102 MPa. The sensor system has been successfully applied to downhole pressure measurement in Liaohe oil field and is going to be installed in a high-temperature offshore oil well for permanent temperature and pressure monitoring.更多还原