Slug Catcher Sizing

Figure1: Severe Slugging in Platform Riser [10]

Figure2: Severe Slugging in Platform Riser [10] There are basically two types of slug catchers, the vessel and multiple-pipe types; multiple-pipe separators have been widely applied in facilities processing a gas condensate stream. For crude-oil stream, where foaming sometimes emerges as a ma jor problem, a vessel type slug catcher is normally used. Such a slug-catching separator must be designed to process the incoming liquid slugs produced by normal pipeline slug flow and to perform an adequate initial separation of the gas and liquid phases. The geometry of the vessel type slug catcher could range from a simple “knock out drum” to a more sophisticated layout. Since the overall length of vessel type slug catchers is relatively short for a given volume this type is preferred in the case of limited plot sizes (e.g. offshore platforms). For larger liquid volumes accommodation (More than 100 m3) multiple-pipe slug catcher should be used [5]:

Figure4: General Configuration of Multiple-Pipe Slug Catcher

Figure5: Different Two Phase Pattern in Horizontal Pipe [10] Stratification is the flow pattern in which separation will happen. It generally occurs when velocity is reduced. This flow regime is encouraged to form when flowing over a declination. To create such conditions, the flow is often split into parallel passages of large diameter pipes. The passages are inclined downward whenever possible [5]. Settling of droplets can occur by gravitation in a primary bottle when flowing at low velocities, typically at less than 2 m / s, towards the gas riser, provided sufficient residence time is allowed for it to happen.

Figure9: Slug Catcher Designed with ANAYS CFX The peak liquid levels were predicted for the original pipeline gas / liquid flow rate and for a flow rate increased by 45 percent. It was found that the maximum height of the liquid in the separation fingers increased significantly when the flow rate was increased but no catastrophic overflow of liquid into the gas outlet was found. As a result, it was concluded that the existing slug catcher will be able to cope with the increased pipeline capacity (blue represents gas and red represents liquid):

Figure10: Transient adaptive meshing to resolve the gas – liquid interface, REFERENCES [1] Bendiksen, K.H., “The Dynamic Two-Fluid Model OLGA: theory and Application, SPE Production Engineering, May 1992, Pages: 171-180 [2] Norris, H.L, “Simulation of Reveals Conditions for Onshore Arctic Gas-Condensate Pipeline”, Oil and Gas Journal, Nov. 17, 2003, Pages: 68-73 [3] Huntley, A.R., Hydrodynamic Analysis Aids Slug Catcher Design”, Oil and Gas Journal, September 19, 1983, Pages: 95-100 [4] Daniels, L., “Dealing with Two-Phase Flows”, Chemical Engineering Journal, June 1995, Pages: 70-78 [5] Bos, A., “Simulation of Gas/Liquid Flow in Slug Catchers”, SPE Production Engineering, August 1987, Pages: 178-132

[6] Saba, N., and Lahey, R.T., “The analysis of Phase Separation Phenomena in Branch Conduits”, International journal of Multiphase Flow, 1984, Volume 10, Pages: 1-10 [7] Azzopardi, B.J., “The Effect of Flow Patterns on Two Phase Flow in T-Junction”, International  journal of Multiphase Flow, 1982, Volume 8, Pages 491-502 [8] Bernicot, M.F., A Slug-Length Distribution Law for Multiphase Transportation Systems, SPE Production Engineering, May 1991, Pages: 166-170 [9] Henry, J.R., “Header Flow Maldistribution in Two-Phase Flow”, HTFS Handbook, National Engineering Laboratory, July 1993 [10] Crowley, Ch.J, “State of the Art Report on Multiphase Methods for Gas and Oil Pipelines, AGA Project, December, 1986 [11] Aspen HYSYS 2004 User Manual