Identification of flow patterns in long pipeline-riser system based on double-category labeling of samples near the transition boundaries

On-line identification of flow pattern provides an important guarantee for the flow assurance of long oil and gas pipeline. Two-phase flow patterns are experimentally investigated in a 1657 m pipeline-riser system with a wide range of air and water velocities. Samples near the transition boundaries are labeled as double-category flow patterns, and only the signals at the initial stage of severe slugging are applied to accurately identify the hazard before it occurs. The recognition rate of flow patterns with double-category labeling is significantly higher than that with single-category labeling, with the highest improvement of 8.6% for oscillating flow. The optimal signal combination is the signals DP₁ and DP₂ collected by the differential pressure sensor arranged above the water surface, with the highest overall recognition rate of 93.7%. The threshold range of double-category labeling and its corresponding minimum sample duration of 6.2 s are obtained under the premise of recognition rate higher than 90%.