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 sev...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.展开更多
Noise and mismatch are important error sources in pipeline ADCs,so careful calculation and system simulation are carried out using Matlab software. To reduce power consumption while not lose performance, the amplifier...Noise and mismatch are important error sources in pipeline ADCs,so careful calculation and system simulation are carried out using Matlab software. To reduce power consumption while not lose performance, the amplifiers with the same structure are biased with one bias circuit, and a cascode compensation is adopted. A 10bit 50MS/s pipeline ADC, which can be used in CMOS image sensor systems with large pixel array,is designed and tested by using 0.35tzm 4M-2P CMOS process. According to test results, power consumption is only 42mW and SINAD is 45.69dB when sampling frequency is 50MHz. A balance between performance and power consumption is achieved.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51527805,11572220 and 41174109)
文摘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.
文摘Noise and mismatch are important error sources in pipeline ADCs,so careful calculation and system simulation are carried out using Matlab software. To reduce power consumption while not lose performance, the amplifiers with the same structure are biased with one bias circuit, and a cascode compensation is adopted. A 10bit 50MS/s pipeline ADC, which can be used in CMOS image sensor systems with large pixel array,is designed and tested by using 0.35tzm 4M-2P CMOS process. According to test results, power consumption is only 42mW and SINAD is 45.69dB when sampling frequency is 50MHz. A balance between performance and power consumption is achieved.
