Experimental investigation on mitigation of severe slugging in pipeline-riser system by quasi-plane helical pipe device

Efficient mitigation of severe slugging in pipeline-riser system can promote a higher level of flow assurance in offshore petroleum exploitation. However, for passive methods, challenges lie in developing a simple and efficient device which is convenient for both underwater installation and pigging operation. In this work, a quasi-plane helical pipe device without hampering both underwater installation and pigging operation was proposed for mitigating severe slugging in pipeline-riser system. The effect of the quasi-plane helical pipe device on severe slugging was illustrated through detailed comparisons between the conditions with and without the quasi-plane helical device on aspects of flow pattern, differential pressure, and liquid production. The experimental results proved the feasibility of the quasi-plane helical pipe device. The velocity ranges of typical severe slugging and of unstable flow on the flow pattern map have been shrunken dramatically with the device, i.e. smaller maximum liquid and gas velocities for the occurrence of severe slugging and unstable flow; and the occurrence of large-amplitude pressure fluctuation in the pipeline and the intermittency of liquid outflow has also been reduced.