introduction objectives simulation & experiment
TRANSCRIPT
www.cranfield.ac.uk
Team members:
Sandy Kosalim, Fergus Crawley, Kwame Kumah, Kevin Lontin, Jemine Odugba
1. To understand when/how
severe slugging occurs in a
multiphase pipeline-riser
system.
2. To develop numerical models
to simulate and predict severe
slugging
3. To validate the numerical
results with experiment data.
4. To evaluate the economic
impact of severe slugging on
production output.
OBJECTIVES
CFD modelling provides a fundamental tool to support
engineering design and research in multiphase systems
Fluent is ran using High Performance Computing (HPC)
at Cranfield.
COMPUTATIONAL FLUID
DYNAMICS (CFD) SIMULATION OLGA SIMULATION
OLGA, a transient multiphase 1- dimensional
simulation software which is developed and
commercialised by Schlumberger is used to investigate
severe slugging in the pipeline-riser system.
Experiments were carried out in the Process System
Engineering (PSE) Lab at Cranfield University using a
three-phase flow rig which can circulate air, water and
oil at pressures up to 7 barg.
LAB EXPERIMENT
Water
Mass Flow
Rate
Superficial
Velocity
kg/s m/s
1 0.109
2 0.218
5 0.546
SIMULATION & EXPERIMENT
FLOW PROPERTIES
*The experiment also used a choke valve to
demonstrate what the effects of increased back
pressure had on the system in terms of slug size and
cycle period.
INTRODUCTION
CONCLUSIONS
LAB RESULTS
Over time, oil and gas exploration
and production has advanced into
deeper waters in West Africa, the
Gulf of Mexico and South America
and continues to go deeper. The
configuration of the pipeline-riser
systems, which is used to transport
the extracted hydrocarbon, often
has the pipeline section inclined
downwards. This configuration can
potentially lead to flow instability
known as severe slugging in the
pipeline-riser system.
1. The severe slugging phenomenon is caused
by a combination of factors in a pipeline-
riser system. The main factors include the
pressure of the system, low fluid flow rates,
inclination of the pipeline section. Increased
fluid flowrate is directly proportional to
increased slugging.
2. Numerical models have shown that they can
simulate severe slugging in multiphase-flow
to a useful degree of accuracy at a fraction
of the cost of building a test rig system.
They also have the added benefit of being
able to create multiple models of any shape
or size. However, CFD models require a
relatively long computational time.
3. Severe slugging has a significant impact on
a project’s capital expenditure (CAPEX),
operating expenditure (OPEX) and revenue.
1
1.2
1.4
1.6
1.8
2
2.2
0 20 40 60 80 100 120 140 160 180 200Pre
ssu
re a
t R
ise
r B
ase
(b
arg)
Time (s) 1 kg/s Pressure vs Time
I II III IV
RESULTS
1
1.5
2
2.5
0 50 100 150 200
Pre
ssu
re a
t R
ise
r B
ase
(b
arg)
Time (s)
Pressure at Riser Base vs Time
0.218 m/s 0.109 m/s 0.546 m/s
SIMULATION RESULTS
The variation of pressure with time in the pipeline-riser allows to better differentiate and classify severe slugging.
One cycle of severe slugging can be classified into 4 stages: slug formation, slug production, blowout, and liquid fall-
back (I, II, III, IV). Slugging increases with increasing superficial velocity, (cycle time-period decreases).
Both the CFD & OLGA simulations gave out very different results regarding the 3 different liquid superficial velocity settings.
The overall trend of slugging is seen throughout all the simulations, there are cycles of high pressure build up, leading to a
blowout (sudden drop in pressure). The CFD model creates a clear pressure-time graph of the slugging effect over time.
Supervisors:
Dr. Patrick Verdin ([email protected])
Dr. Liyun Lao ([email protected])
Air
Volumetric
Flow Rate
Superficial
Velocity
Sm3/h m/s
20 0.217
1
1.2
1.4
1.6
1.8
2
2.2
2.4
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Pre
ssu
re(b
arg)
Time(s)
OLGA Result for USL = 0.546m/s
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0 20 40 60 80 100 120 140
Pre
ssu
re (
bar
g)
Time (seconds)
Numerical Models vs Experiment USL = 0.546 m/s
Experiments
CFD
OLGA