Experimental investigation on long hydrodynamic slugs in offshore pipeline

Abstract

In the process of liquid-dominated offshore oil and gas transportation, long hydrodynamic slugs are likely to occur in subsea pipelines at high liquid holdup. A large number of long hydrodynamic slug data at high liquid velocity and low gas velocity were obtained by using visual images in a 46 mm ID, 1657 m long pipeline. The flow pattern map close to the industrial parameters is plotted, and slug flow can take place at a lower superficial gas velocity (VSG = 0.045 m/s) in the long pipeline. The maximum slug length is 2.5 times the average slug length, and the longest liquid slug is 969 D near the transition boundary of slug flow. When VSG < 1.00 m/s, slug length increases rapidly and slug frequency decreases significantly with the decrease of superficial gas velocity at the same superficial liquid velocity. The prediction correlations of slug velocity, length, and frequency are developed for long-distance offshore pipelines at high liquid velocity and low gas velocity, and the maximum error is less than 25%.