Page 213 - Handbook Of Multiphase Flow Assurance

212 8. Flow assurance stability issues

Fs = slug frequency per hour; D = pipe diameter, m; Vm = mixture velocity, m/s; V SG =
superficial gas velocity, m/s; Hle = equilibrium stratified liquid holdup; V SL = superficial
liquid velocity, m/s.

Prediction methods

Flow regime map
Flow regime map is plotted in coordinates of superficial liquid velocity vs. superficial gas
velocity, on a log-log scale.
A flow regime map would be expected to have the following form (Fig. 8.1).
Stability limits
Multiple additional works on severe slugging are available in the literature such as
Montgomery (2002). The author indicates that severe slugging causes a 20% drop in pro-
duction, and results in separator trips/shutdowns. The stability criterion proposed by the
author:
G ) (
S∗
U GL S ≤ U GB (1 − gε LP L sinθ L (ρ −ρ / P + ρ L g h ))
P
R
S
S
U GL = inlet gas velocity.
S
U GB = gas velocity entering the riser base, m/s.
2
g = gravity acceleration, m/s .
ε LP = pipeline liquid holdup, calculated using Taitel (1986) method.
L P = downhill pipe length upstream of the lowest point.
θ = inclination from horizontal at riser base downstream of the riser lowest point.
P S = separator pressure.
ρ L = liquid density.
ρ G = gas density.
h R = riser height.

FIG. 8.1. Typical multiphase flow regime map.