Measurement Method Of Ultrasonic Sensors For Flow Parameters In Horizontal Gas-liquid Intermittent Flows

Production profile testing is an important supporting technology for shale gas production,which has important academic value and practical significance for understanding the fluid distribution in the gas well,optimizing well trajectory and fracturing parameters,guiding the production management process,and ultimately improving shale gas recovery.In this paper,the ultrasonic sensing technology for measuring gas holdup and velocity distribution of horizontal gas-liquid two-phase flow was investigated.Based on the pulsed ultrasonic echo technology,a gas holdup measurement system and a Doppler measurement system were designed,and a horizontal gas-liquid flow experiment in a 20 mm inner diameter pipe was carried out.According to the responses of the pulsed ultrasonic gas holdup measurement system,the gas holdup measurement models of gas-liquid flows under different flow patterns were established.Based on the response of the pulsed ultrasonic Doppler measurement system,the velocity distributions of the gas-liquid flows were measured and the evolution law of dispersed bubble velocity distribution in intermittent flow was investigated.The innovative research achievements of this paper are as follows:1.Based on the pulsed ultrasonic technology,a pulsed ultrasonic gas holdup measurement system was designed,including ultrasonic sensor,ultrasonic excitation module,signal condition module,FPGA module,etc.Based on the hardware of the measurement system,a pulsed Doppler measurement system was developed,using a new ultrasonic excitation module consisting of a signal generator and a power amplifier.The state machine of the FPGA module was optimized to improve the system working frequency and data throughput,and joined the signal processing in it,including orthogonal mediation and low-pass filtering.The signal-to-noise ratio of the pulsed ultrasonic Doppler measurement system was improved effectively,and the measurement depth and measurement range of dispersed phase velocity were expanded.2.Based on the time-of-flight algorithm,the liquid film thickness of the stratified flow and the intermittent flow was measured,and the gas holdup measurement model of the stratified flow and the film region in the intermittent flow were established.A physical model for measuring gas holdup of the slug region in the intermittent flow was established based on ultrasonic attenuation characteristics.The measurement model of the intermittent flow was obtained by weighting the relative lengths of the film region and the slug region.Compared with the measurement results of a wire-mesh sensor,it shows that the pulsed ultrasonic gas holdup measurement system designed in this paper has higher measurement accuracy for gas-liquid stratified flow and intermittent flow,and the error sources are clear and easy to correct,which has the potential to further improve the measurement accuracy.3.Based on the response of the pulsed ultrasonic Doppler measurement system,the temporal and spatial distributions of instantaneous velocity in stratified flow and intermittent flow were obtained by the phase difference method.By effectively identifying the film region and the slug region of the intermittent flow,the average velocity profile,the velocity location probability density distribution,and the velocity values probability density distribution in intermittent flow were extracted,and the evolution characteristics of the velocity distributions under different gas and water phase superficial velocities were investigated.The results reveal the local fluid characteristics of horizontal gas-liquid intermittent flow,which can provide a theoretical basis for developing the production profile testing technology in shale gas wells.