【作者】 景春国；

【导师】 邢广忠； 刘彬；

【作者基本信息】 燕山大学 ， 检测技术与自动化装置， 2008， 博士

【摘要】 石油的生产、加工、输运等过程都与多相流有关,准确测量油水气多相流对监测油井生产状况、预测油田储量、优化油田开采方法、管理原油生产过程等有着重要意义。由于油水气多相流在管道流动时存在多种流型以及原油成分、水矿化度、介质温度等不断变化,油水气多相流测量一直是难于解决的问题。本文采用低能(<100keV)射线研究油水气多相流相含率测量问题,应用双能射线透射法和单能射线透射散射法测量油水气相含率。采用双能射线测量低含水原油的水相含率。通过散射射线能谱识别垂直管道气液两相流的流型,修正流型对双能射线法气相含率测量的影响。论文在分析射线法油水相含率测量模型的基础上,应用Monte Carlo仿真方法模拟γ光子与油水气介质的相互作用过程,对系统进行优化设计。通过仿真研究射线能量与灵敏度、统计误差的关系,发现低能γ射线对油水变化的灵敏度高,确定双能射线源采用238Pu和241Am同位素,单能射线源采用241Am同位素;研究散射探测器位置与散射射线能量分布的关系,确定散射探测器在90°散射角位置时能够反映管道流体的流态;分析了温度、压力和油成分变化对低含水原油水相含率的影响,建立了温度和油成分变化的补偿算法。应用散射射线能谱分布识别气液两相流型,补偿双能射线透射法气相含率的测量误差。仿真获得了均匀混合流、环状流和弹状流三种流型产生的散射射线能量概率分布数据,应用RBF网络对三种流型进行识别,均匀混合流和环状流的识别率为100%,应用流型识别结果修正环状流对双能射线气相含率测量的影响。采用RBF神经网络预测γ射线透射散射法的水相含率和气相含率,与双能射线模型近似求解相比,提高了相含率测量的精度。建立了油水气相含率测量实验系统。根据射线源和探测器的规格设计了测量装置的机械结构,进行了探测器输出信号放大成形电路和计数卡电路设计,开发了基于Windows驱动模型的计算机精确定时模块,减小了定时误差对射线强度计数值的影响,通过计算机进行数据采集与处理,用于油水气相含率测量实验。在循环测量装置上进行了双能射线油水气相含率测量、单能射线透射散射法油水气相含率测量和低含水原油水相含率测量试验,实验表明,双能射线法含水率和气相含率的最大绝对误差均小于0.01;单能射线透射散射法预测含水率最大绝对误差为0.04,预测气相含率最大绝对误差为0.02;双能射线法低含水原油水相含率测量精度高,温度、油成分变化对水相含率测量的影响通过算法进行补偿,补偿后的水相含率最大绝对误差小于0.002。更多还原

【Abstract】 Multiphase flows are common in the petroleum industry, and it is related to oil extraction, transportation and refining processes. It is important to measure oil water and gas volume fractons for monitoring oil well, predicating oil reserves, optimizing oil extraction methods and managing oil production. The fact is that there are many different flow regimes in the pipe flow and the mixtures’s temperature and salinity are contantly change at the same time, so it’s always a difficult problem to measure oil water and gas volume frations.This paper studies on the oil, water and gas volume fraction measurement based on low energy radiation which less than 100keV. The phase fraction of crude oil measured by dual energies radiation transmission methods and single energy radiation transmission and scattering methods. The flow pattern recognition of gas-liquid two-phase flow in vertical pipe was studied by measuring gamma-ray scattering spectrum. The result of the flow recognition was used to compensate the effects of the flow pattern on the gas phase volume fraction measurement of dual energies radiation method.The paper introduces the models of oil, water and gas volume phase fraction using radiation method. In order to optimize system design, the particle transport process for oil, water and gas volume phase fraction measurement were simulated by using Monte Carlo method. The sensitivity and statistical errors with radiation energies were researched by the simulation software, and it found that low energy gamma-ray has high sensitivity for oil and water medium. So the dual energies radiation source is compose of 238Pu and 241Am isotope and single energy radiation source choices 241Am isotope by taking into the source’s half-life. In order to determine scattering detector position, the energies distribution of scattering ray with the scattering detector location were studied. The results show that the scattering detector can reflect the fluid state of pipeline when it located on source-transmission detector vertical position. The effects of temperature, pressure and oil contents change on water volume fraction measurement of dehydrated oil were analysed. The compensation algorithms for temperature and oil content change were found. The errors of gas volume fraction caused by the flow pattern were correctted by the scattering ray energy spectrum for the dual energies radiation. The scattering ray energy probability distribution of the homogeneous mixed flow, annular flow and slug flow in vertical pipeline were obtained by simulation method. The flow patterns were identified by RBF neural network using simulation data. The results show that the homogeneous mixing flow and annular flow can be completely seperated. The effects of annular flow on gas volume fraction can be corrected by the compensation algorithm. The phase fraction of gamma-ray tansmission and scattering method were predicted by RBF neural network. The precision of phase fraction were increased comparison with dual energies algorithm.The oil, water and gas measurement system were setup. The measuring device mechanical structure was designed according to the radiation source and detector’s specifications. The pusle shaping amplifier circuit for detector output and the computer counting cards were designed. The precise timing codes were developed by using windows driver model. The efftect of timing error on phase volume fration measurement can be reduced. The computer was used for the data acquiring and processing.The experiments for the dual energies ray method, single energy gamma ray transmission and scattering method and low water content crude oil measurement were implemented in the measuring device. The experimental results show that the maxinum absolute error of water cut is less than 0.01 and the maxinum absolute error of gas volume fraction is less than 0.01 by using dual energies ray method; The maxinum absolute error of water cut is 0.04 and the maxinum absolute error of gas volume fraction is 0.02 by using the single energy gamma-ray transmission and scattering method; The precision of of water volume fraction for low water content crude oil has been improved when using dual energies ray. The effects of temperature and oil composition changing on low water content crude oil can be compensated by some algorithms and the maxinum absolute error of water volume fraction is less than 0.002.更多还原