Study on eliminating severe slugging by manual and automatic choking in long pipeline-riser system

Abstract

Severe slugging produces huge fluctuations of pressure and flow rate, which is often eliminated by choking because of its easy operation and good performance. However, most published studies on choking are conducted in short-distance pipelines at atmospheric pressure, which is far from the oilfield conditions. In this paper, study on the influence of choking on severe slugging characteristics and control effect is carried out on the high-pressure long-distance pipeline-riser system. When using manual choking, the pressure fluctuation frequency increases and the system pressure exceeds its steady-state value under certain conditions. There is an optimal valve opening range when using automatic choking, which minimizes the fluctuation amplitude of differential pressure. The pressure required to eliminate severe slugging increases with the increase of pipeline length. In order to eliminate severe slugging automatically, a correlation for predicting the stable pressure at the riser bottom is proposed, with an average relative error of 10.9 %.