【作者】 王红梅；

【导师】 金宁德； 翟路生；

【作者基本信息】 天津大学 ， 控制科学与工程， 2018， 硕士

【摘要】 水平油水两相流广泛存在于石油开采过程中,其持水率动态监测对优化油田开采方案、提高原油采收率有重要意义。然而,水平油水两相流流动结构复杂多变,其持水率测量存在极大困难。本文设计了一种基于四电极对壁电容传感器的新型循环激励相移检测系统,用于测量水平油水两相流的持水率。首先,基于油水的层状分布建立电容传感器等效阻抗网络模型,模拟了不同持水率条件下相移检测系统的输出响应特性,研究了水相电导率对相移检测系统输出响应的影响,从而实现电容传感器的几何结构、测量系统电路参数的优化设计。开展了水平油水两相流动态实验,获得不同流型下相移检测系统的输出响应。结果表明,在ST、ST&W、ST&MI流型下,上下电极的归一化输出相移量对持水率的变化分辨率较高,在一定程度上受到流体流动结构的影响;在D W/O&D O/W和D O/W&W下,上下电极的归一化输出相移量对持水率的变化分辨率较低,这是因为两种流型中管道上层出现水膜,增强了漏电流效应,导致传感器失去分辨率;左右电极的归一化输出相移量仅在低持水率有较高的分辨率,当左右电极间出现导电水相,漏电流及阻抗网络阻性锐减导致传感器相移量不再随持水率变化;左上电极的相移测量特性与上下电极类似;左下电极受水相电导特性影响显著,其相移响应也表现出较低的测量分辨率低。最后,利用基于庞加莱截面的多尺度分布熵分析了相移检测系统的响应信号,提取了不同流型下的高时间尺度分布熵值,发现高时间尺度分布熵可有效表征水平油水两相流流体结构演化过程。更多还原

【Abstract】 The oil-water two-phase flow widely exists in the petroleum exploration of horizontal wells.The dynamic monitoring of water holdup is of great significance in optimizing the oil exploration scheme and enhancing the oil recovery.However,flow structure of the horizontal two-phase flow is complex and changeable,which brings great challenges to the water holdup measurement.In the paper,we design a new fluid phase-shift detection system based on a four-electrode concave capacitance sensor to measure the water holdup of the horizontal oil-water two-phase flow.First,for stratified oil-water two-phase flow,we set up an equivalent impedance network model of the capacitance sensor,aiming at predicting the measurement characteristics of the capacitance phaseshift sensor under different water holdup.The influence of the water conductivity on the measurement is analyzed based on the model.Besides,we use the model to optimize the structure of the capacitance sensor and the parameters of the measuring circuit.Then,we carry out a horizontal oil-water two-phase flow loop test and obtain the measurement responses of the phase-shift dectection system under different flow patterns.The result shows that when the exciting and the receiving electrodes are respectively the upper and lower ones,the normalized capacitance phase-shift signal is sensitive to water holdup variation of ST,ST&W,ST&MI flow pattern,and the signal is,to some extent,influenced by the flow pattern.In contrast,under the D W/O&D O/W and D O/W&W flow pattern,the normalized phase-shift response is less sensitive to the water holdup in this kind of exciting-receiving mode.It’s because that the water film exists in the upper side of the inner pipe wall,which aggravates the leakage of current.In addition,the nomalized phase-shift response is only sensitive to the low water holdup while the exciting and receiving electrodes are respectively the left and right ones.This result arises from that once there is water existing between the left and right electrode,the current leakage and sharp reduction of the impedance will result in no response of the sensor to the water holdup.Notably,the phase-shift response from the left and upper electrodes is similar to that from the upper and lower ones.Moreover,the phase-shift response is seriously influenced by the water impedance while the exciting and receiving electrodes are respectively the left and lower ones,which is less sensitive to the water holdup variation.Finally,we adopt the multi-scale distribution entropy of Poincaré plot to analyze the capacitance phaseshift sensor signals.It reveals that the distribution entropy at high time scale can effectively characterize the evolution characteristics of the horizontal oil-water two-phase flow structrues.更多还原