Monitoring Slug Flow Using Distributed Acoustic Sensing Technology with Different Sensing Cable Configurations

Summary Monitoring slug flow in real time over long distances is essential for facility design, operation, and flow assurance management. In this study, we investigated the use of distributed acoustic sensing (DAS) technology for slug flow monitoring, exploring various cable designs and deployment methods. The experimentation encompassed the use of five distinctive fiber-optic cable deployment methods: three internal cables of varying designs (thin, flat, and thick), supplemented by two external cables—one placed straight atop the pipeline while the other was helically wrapped around it. All cables were connected consecutively and successfully captured the dynamic variation of the slugging phenomenon along the pipe. We introduce different data processing algorithms for slug flow characterization, including standard deviation (SD) downsampling, slug frequency determination, and semblance for velocity extraction. The experimental results indicate a higher slug frequency but smaller slug sizes near the inlet of upward inclined pipe, where most slug structures originate. The structure velocity shows a positive correlation with DAS amplitude or the maximum strain rate, which could be related to the slug size. The flat cable exhibited a heightened amplitude response to slugs, while the internal thin and the external straight cables provided the most distinct delineation of slug patterns. The internal thick cable provided the least sensitivity among all due to its design. Although the linear deployment of fiber-optic cables is more practical compared to helically wrapped ones, their resolution limits detailed analysis of more intricate slug characteristics for short pipelines, such as precise velocity measurements of slugs. Data from the helically wrapped cable can address these limitations, providing more comprehensive insights.