多层筒式电容注汽井干度测试新方法研究

Accurate measurement of steam quality on-line and real-time is always being an intractable project throughout the world. Based on the remarkable sensitivity to the slight change of medium permittivity, a novel method of steam quality on-line measurement for viscous crude extraction of injection steam wells is put forward based on multilayered cylindrical capacitance sensor in this project. The optimal structure and size of the sensor is studied by means of theoretical analysis and experimental tests method, and then a novel the sensor is prepared. The laws of steam quality changing with permittivity are investigated, and the mathematical model of steam quality measurement is built, so that stability and repeatability of the system are improved. Thus, the inner link between steam quality and capacitance value is revealed. In addition, according to the obtained thermodynamic parameters of steam fluid under determined temperature and pressure condition, a model inversion of steam quality is built up. It provides powerful guarantee for real-time known the reservoir location, reservoir distribution and absorption situation and increase oil extraction. Therefore, this novel method is provided to accurately evaluate response of steam quality during the downhole viscous crude extraction.

注汽井蒸汽干度实时在线准确测量始终为一国际难题。本项目基于电容传感器对介质介电常数微小变化极其敏感的特点，提出一种新型多层筒式结构电容传感器进行注汽井蒸汽干度实时在线测量的新思路。采用理论分析与试验相结合的方法，优化设计传感器结构和尺寸，研制一种新型多层筒式电容传感器；考查蒸汽干度随介电常数的变化规律，构建最优注汽井干度数学测量模型，提高测试系统稳定性和重复性，研究蒸汽干度与电容值之间的内在联系；基于一定工作温度、压力条件下蒸汽的热力学参数，建立注汽井蒸汽干度反演模型，为实时掌握油层位置、油层分布状况及油层对蒸汽干度吸收情况、提高采油率提供有力保障，为注汽井蒸汽干度响应规律准确评价提供新方法。

我国石油资源丰富，粘度重质石油（稠油）占主导地位。因稠油粘度高，密度大给开采带来极大的困难。目前主要开采方法是稠油热采法，即向注汽井注入高温高压蒸汽。由于蒸汽中含有较高的热量，可使油层温度升高，降低稠油粘度，减少流层阻力，使稠油易于流动，然后再采用常规的方法加以开采。为了实时掌握油层的分布情况及油层对蒸汽的吸收情况，必须对注汽井蒸汽热效特性的关键参数——蒸汽干度，进行实时准确的测量。实时准确测定注汽井井下蒸汽干度，对油层状况进行分析，合理开采，提高采油率及节约能源都有重要的意义。. 本文基于电容传感器对介质的介电常数微小变化极其敏感的特点，提出了一种基于圆筒式电容传感器测量注汽井井下蒸汽干度的新方法，进而对蒸汽干度的研究开拓了新思路。通过设计和优化筒式电容传感器结构，进行多次注汽井测试试验，系统研究蒸汽介电常数与电容值之间的内在联系，揭示蒸汽介电常数随温度和压力的响应规律。随着注汽井中油层深度的增加蒸汽干度的变化，对实验测得数据进行反演，得到蒸汽干度值。熟知井下蒸汽干度值的变化规律为充分了解井下蒸汽吸收状况和热效特性、优化开采方案、提高稠油开采率提供了理论指导，为使用新型电容传感器的应用奠定了理论基础。蒸汽干度测量系统采用C8051处理器为核心，采用温度传感器、压力传感器、电容传感器对井下的信号进行采集。将采集的参数代入建立的蒸汽干度测量模型—— ，对蒸汽干度测量模型进行反演，将测量的结果绘制成版图形式，反映出干度值随着测试点的变化趋势。从室内试验和测井试验结果来看，设计的注汽井干度测量系统实现了注汽井干度实时在线的测量。测量结果显示蒸汽干度在井口时为84%，随着注汽井深度的增加，到达井深为1400米时蒸汽干度降低到52%左右。测量电容精确度可达0.005pF。在测量过程中，测量系统运行稳定可靠，精度较高，满足了注汽井井下蒸汽干度测量的需求。