中文摘要：

国内陆上处于中晚期开采的低孔低渗油藏已进入高含水生产状态,其井筒内油水两相流分散相（油滴）局部流速及浓度呈严重的非均匀流动剖面特性,致使油井持水率检测难度很大。本文采用脉冲透射式的超声传感器对低流速高含水油水两相流持水率进行测量。首先,使用多物理场耦合有限元法计算超声场灵敏度分布,对超声传感器激励频率进行了优化。通过计算不同持油率下声压级衰减率,对超声传感器直径的适用性进行了考察。在此基础上,研究了油滴直径及分布对超声传感器声场分布特性的影响。为验证优化后的超声传感器测量特性,搭建了低流速高含水垂直上升油水两相流流动环试验装置,并获取了超声传感器持水率输出响应特性。结果发现超声传感器对水包油段塞流（DOS/W）的测量分辨率较差,但对水包油泡状流（DO/W）和水包油细小泡状流（VFD O/W）具有较好的分辨率。研究表明脉冲透射式超声法对低流速高含水油水两相流持水率测量存在潜在的应用价值。

英文摘要：

Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.