倾斜光纤Bragg光栅表面等离子体共振井下蒸汽干度测试新方法研究

Based on the characteristics of Surface Plasmon Resonance(SPR) technology which is remarkably sensitive to the slight change of medium permittivity, a novel method of steam quality measurement for downhole saturated steam in viscous crude extraction is put forward based on tilted fiber Bragg grating (TFBG) SPR in this project. Structures of the sensing devices are studied by means of theoretical simulation and experimental tests, and then the design standard for the sensors is obtained. The sensing metal thin film for TFBG-SPR is deposited onto the cladding of TFBG by means of r.f.magnetron sputtering technology. The influences of grating fundamental structural parameters, metal materials, film thickness, morphology and microstructure on the SPR spectra are investigated, and then the micro-mechanism is revealed.The coupled internal mechanisim of core modes and cladding radiation modes is clarified, and the key parameters and conditions for SPR phenomena occuring as well as resonance wavelength positions are determined. The internal relationships between resonance wavelength and the permittivity of the steam as well as the steam quality are revealed, and then the explanation model of steam quality data for downhole measurement is built. Therefore, this novel method is provided to accurately evaluate steam quality during the downhole viscous crude extraction.

基于表面等离子体共振(Surfac Plasmon Resonance,SPR)技术对介质介电常数微小变化极其敏感的特点，提出一种新型倾斜光纤布拉格光栅(Tilted Fiber Bragg Grating,TFBG)SPR井下稠油热采饱和蒸汽干度测量新方法；采用理论仿真与试验相结合的方法，系统研究TFBG-SPR传感元件的结构设计准则；采用磁控溅射技术在TFBG包层表面沉积金属敏感膜制成SPR传感元件，研究TFBG-SPR的透射光谱特性，考察光栅结构参数、金属敏感膜材料、薄膜厚度、表面形貌以及微观结构对蒸汽介质透射光谱的影响，揭示其微观机制；查明纤芯导模与包层辐射模之间的耦合特性，确定SPR现象产生的关键因素、条件及共振波长位置，揭示SPR共振波长与蒸汽介电常数以及干度之间的内在联系,建立测井资料解释模型，为稠油井下热采蒸汽干度的准确评价提供新方法。

稠油生产过程中向井下注入高温高压蒸汽的方法是实现稠油开采的主要方式之一。为实时掌握井下注汽状况和井管中蒸汽在线特性，必须对表征蒸汽热效特性的关键参量--干度，进行准确测定，传统人工取样方法存在测量周期过长等问题，为此开展新型传感测试方法以实现井下蒸汽干度的实时在线监测新方法及新工艺研究，不但有利于优化开采方案，科学合理安排生产，而且可为降低蒸汽热能损耗、节约成本及提高原油采收率提供理论指导，具有重要的现实意义。本项目基于表面等离子体共振(Surface Plasmon Resonance,SPR)技术对介质介电常数微小变化极其敏感的特点，提出了将金属薄膜沉积于倾斜光纤布拉格光栅表面制作成表面等离子体共振传感器用井下稠油热采饱和蒸汽折射率测量，并结合油田测井资料实现井下蒸汽干度实在在线监测的新思路和新方法。本项目从表面等离子共振传感技术的原理和基本理论出发，深入分析了表面等离子体共振产生的条件和传感机制，深入研究了棱镜型角度调制和波长调制型SPR传感结构的光谱特性，考察了光入射介质折射率、金属薄膜材质(Au、Ag、Al等)及其厚度、待测介质折射率等参数对SPR共振谱的影响，为设计SPR传感器提供了理论指导；采用数值计算的方法，深入研究了倾斜光纤Bragg光栅(Tilted Fiber Bragg Grating, TFBG)的透射光谱特性，查明了共振波长的影响因素及其变化规律，建立了TFBG-SPR传感元件的结构设计准则；采用小型溅射镀膜机在TFBG包层表面沉积金属敏感膜制成SPR传感元件，通过控制溅射时间、电压和电流控制薄膜厚度，分析测试了TFBG-SPR传感器的透射光谱特性，实测了NaCl溶液的折射率，建立了共振波长与折射率和浓度之间的关系，研究了共振波长与介质折射率以及干度之间的内在联系,建立了资料解释模型，为稠油井下热采蒸汽干度的准确评价提供新方法。项目执行期间共发表论文29篇，其中SCI收录15篇，授权实用新型专利2项，培养博士后1名，博士研究生1名，硕士研究生5名。