1. State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China 2. CNOOC Research Institute, Beijing 100027, China
Experiments on flow patterns during air-oil two-phase flow in a long pipeline-riser system with an S-shaped riser are carried out. The test loop with 50.8 mm internal diameter consists of a horizontal pipeline with 119 m in length, followed by a 14 m downward inclined section, and ended at an S-shaped flexible riser with 24 m in length, 15.3 m in height. The inclination angle of the downward section is -2° from the horizontal pipeline. Based on the analysis of the pressure at the riser base and liquid holdup at the riser top, the flow regimes observed are classified into three categories: severe slugging of type 2 (SS2), transition flow (TRS), stable flow (including bubble flow, slug flow and annular flow). In contrast with air-water two-phase flow, there is no sign of severe slugging of type 1 in the present study. As for SS2, the probability density function (PDF) of liquid holdup presents a bimodal distribution with two peaks at HL = 0 and HL = 1, respectively. As for TRS, the PDF curve produced by liquid holdup data presents a unimodal distribution with a single narrow peak at HL = 0. As for stable flow, the PDF of liquid holdup presents a bimodal distribution between HL = 0.3 and HL = 0.8.
Yocum B T.Offshore riser slug flow avoidance: mathematical models for design and optimization[C]. SPE, 1973: 4312.
[2]
Schmidt Z, Brill J P, Beggs H D.Experimental study of severe slugging in a two-phase-flow pipeline: riser pipe system[J]. Society of Petroleum Engineers Journal, 1980, 20(5): 407.
[3]
Pots B F M, Bromilow I G, Konijn M J W F. Severe slug flow in offshore flowline/riser systems[J]. SPE Production Engineering, 1987, 2(4): 319.
[4]
Fabre J, Peresson L L, Corteville J, et al.Severe slugging in pipeline/riser systems[J]. SPE Production Engineering, 1990, 5(3): 299.
[5]
Tengesdal J Ã, Sarica C, Thompson L. Severe slugging attenuation for deepwater multiphase pipeline and riser systems[J]. SPE Production & Facilities, 2003, 18(4): 269.
Tin V, Sarshar S.An investigation of severe slugging characteristics in flexible risers[C]. Proc. 6th Int. Conference on Multiphase Production, 1993: 205.
[8]
Montgomery J A, Yeung H C.The stability of fluid production from a flexible riser[J]. J Energy Resources Technology, 2002, 124(2): 83.
[9]
Mokhatab S, Towler B F.Severe slugging in flexible risers: review of experimental investigations and OLGA predictions[J]. Petroleum Science and Technology, 2007, 25(7): 867.
Jones O C, Zuber N.The interrelation between void fraction fluctuations and flow patterns in two-phase flow[J]. International J Multiphase Flow, 1975, 2(3): 273.