Numerical Study of Bottom Water
Draw-Off of Stratified Oil-Water
Pipe Flow
Yousef Zurigat
Bssam Jubran
Lyes Khezzar
Salam Al-Far
Department of Mechanical and Industrial
Engineering
College of Engineering
Plan
Introduction & Objectives
Oil-water Transport & dehydration issues
Simulation Model
Results
Conclusions
Water issues in
Oil-Production
Well life extension results in increased
water Production (98%)
Need to separate water from oil
(dehydration facilities cost money)
Pre-separation may take place in transport
pipelines
Can we take advantage of it?
Concept of Bottom Water
Draw Off
Depending upon prevailing conditions a water
layer may form at the bottom of the pipe.
It can then be selectively removed.
Oil in Water
Emulsion
Interface
Bottom-Water
Draw-off pipe
Design Challenge of BWDO
Concept
What is the maximum water flow rate that can
be drawn off (With Acceptable quality)?
How can disturbance of the water/oil-in-waterdispersion interface be avoided?
If several draw-off points are used, how will the
interface and flow regimes in between draw
points be affected?
Objectives
 For a single draw-off pipe, investigate the
variation of oil concentration in the draw-off pipe
as a function of draw-off flow rate and interface
position.(Interface location not known a priori!!)
 Investigate the maximum possible water flow
rates with acceptable quality (oil concentration)
for two consecutive draw-off pipes.
Flow Regimes of Oil-Water
Mixtures
Depending upon the oil superficial velocity
several regimes are possible for horizontal water
dominated flows:
Stratified Flow
Stratified Flow with Mixing at the interface
Dispersion of oil in water and water
layer
Oil in water Emulsion
Geometry and Flow
Parameters
Main pipe Diameter = 0.68 m
Draw-Off Pipe Diameter = 0.240 m
Oil-flow rate = 8049 m3/day
Water flow rate = 43614 m3/day
Interface Location 25 cm from bottom of
main pipe.
Simulation conducted with one and two
draw-off pipes
Modelling challenges
Flow is complex and two-phase (dispersions
present)
Two Approaches:
1. Single-Phase Flow Modeling: If negligible
slip between the phases and hold-up take
place--In the present regime!! (watercut=85%, water superficial velocity=1.3
m/s)!
2. Two-Fluid Flow Modeling: Actual Flow
Mathematical Model
SINGLE-PHASE FLOW MODEL
Steady, Single-phase, incompressible and
turbulent flow.
Pressure drop approaches that of single phase
flow
Flow dynamics very similar to single phase
flow
Full three-D simulation
Quantitative analysis of draw-off water
quality-Single : Phase Flow Model
Initial oil concentrations in the pipe regions above and
below the interface are based on experimental data. The
concentration of oil in free water assumed equal to 600
ppm in accordance with field data.
The amounts of oil in the areas above- and below-theinterface streams which make up the draw-off flow are
calculated based on the flow rates and the
concentrations calculated in the first step above.
Second Tapping Draw-Off (m3/d)
Cut-off flow rates with water quality
<2000 ppm from two tappings
11000
o/w 20000ppm
o/w 40000ppm
9000
o/w uniform
7000
5000
3000
7000
9000
11000
First Tapping Draw-Off (m3/d)
Two-Fluid Modeling
In the PHOENICS, the concept of thermodynamic phase is used, i.e., the water and oil
are treated as two different phases in the
mixture. These two phases are in motion
relative to each other due to the buoyancy
effect, which leads to inter-phase momentum
transfer.
The Inter-Phase Slip Algorithm (IPSA) is
adopted to predict the phenomenon in this
work.
Phase equations
Each phase is regarded as having its own
distinct velocity components.
Phase velocities are linked by interphase
momentum transfer - droplet drag, film surface
friction etc.
Each phase may have its own temperature,
enthalpy, and mass fraction of chemical
species.
Phase concentrations are linked by interphase
mass transfer.
Phase equations (Cont.)

d ( Ri  ii )
  Ri  iVii  Ri  , i i  Ri S , i
dt

t
Ri
i
i
time
volume fraction of phase i
density of phase i
any conserved property of phase i

Vi
,i
S,i
velocity vector of phase i
exchange coefficient of the entity  in phase i
source rate of i

Results
Results (Cont.)
Results (Cont.)
Pipe 1
Pipe 2
Results (Cont.)
1.00E+00
9.00E-01
x=1.9, KEP
8.00E-01
x=1.9, Level Model
7.00E-01
x=1.9, Model KL
x=1.9, KECHEN
5.00E-01
4.00E-01
3.00E-01
2.00E-01
1.00E-01
0.00E+00
0
0.2
0.4
0.6
h/D
0.8
1

R2
6.00E-01
Results (Cont.)
9.00E-03
8.00E-03
7.00E-03
R2
6.00E-03
5.00E-03
Q2
4.00E-03
3.00E-03
2.00E-03
1.00E-03
0.00E+00
0
2000
4000
6000
8000
Flow Rate From The First Draw -off pipe (m ^3/day)
10000
12000
Results (Cont.)
1.000E+00
9.000E-01
8.000E-01
7.000E-01
x=1.9
R2
6.000E-01
x=4.5
5.000E-01
x=6.9
x=9
4.000E-01
3.000E-01
2.000E-01
15% oil
1.000E-01
0.000E+00
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
h/D
R2 distributions along the main pipe, KEP, BD1=7000, BD2=3000
0.8
0.9
1
Results (Cont.)
7.00E-01
6.00E-01
5.00E-01
R2
4.00E-01
3.00E-01
R2 @ 3000 m^3/day
R2 @4000
R2 @5000
R2 @6000
R2 @7000
R2 @8000
R2 @9000
R2 @10000
2.00E-01
1.00E-01
0.00E+00
0.00E+00 1.00E-01 2.00E-01 3.00E-01 4.00E-01 5.00E-01 6.00E-01 7.00E-01 8.00E-01 9.00E-01 1.00E+00
h/D
R2 at x=8.74 for 2nd BWDO pipe w ith 1st pipe colsed
Results (Cont.)
0.35
0.3
0.25
h/D
0.2
0.15
h/D at 1200ppm for 95% water cut
h/D at 1200ppm for 85% water cut
0.1
0.05
0
2000
3000
4000
5000
6000
7000
BWDO
8000
9000
10000
11000
Acknowledgements
PDO’s FUNDING OF
THIS WORK IS
GRATEFULLY
ACKNOWLEDGED