flow control in oil/gas wells and pipelines trial lecture ph.d dissertation even solbraa 14.february...
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Flow Control in Oil/Gas Wells and
Pipelines
Flow Control in Oil/Gas Wells and Pipelines
Trial Lecture
Ph.D Dissertation Even Solbraa14.February 2003
Flow Control in Oil/Gas Wells and
Pipelines
1. Introduction to flow control 2. Multi-phase flow with emphasis on slug flow3. Stabilization of flow in Oil/Gas wells and pipelines4. Examples of flow control for selected oil and gas
fields5. Conclusions
Outline
Flow Control in Oil/Gas Wells and
Pipelines
(illustrations: Statoil picture library)
Norwegian Oil and Gas Production
• Platforms
• Floating production units
• Pipelines directly to shore
• Oil to refineries
• Gas exported to Europe
Flow Control in Oil/Gas Wells and
Pipelines
Trends and Facts in Oil and Gas Production• Few new ‘giant’ oil and gas fields are likely to be discovered
• More than a quarter of the world’s oil and more than 15% of its natural gas lies offshore
• Most of the new discoveries are expected to occur offshore
• New large fields are probable in deep waters
• Develop new and cost effective solutions for small fields
• Multiphase transport directly to shore
• Tie-in of well stream from sub sea installation to platform
(Oliemans, 1994, Sarica and Tengesdal, 2000)
Flow Control in Oil/Gas Wells and
Pipelines
Multiphase Transport Solutions
The Snøhvit solution:Transport directly to shore
The Åsgard field:Floating production system
(www.statoil.com)
Flow Control in Oil/Gas Wells and
Pipelines
Multi-Phase Fluid Flow (Oil/Water/Gas)
Flow Control in Oil/Gas Wells and
Pipelines
What is the sea depth of future fields ?
• Norwegian Sea 1500 meter
• Gulf of Mexico 2500 meter
• West Africa 1500 meter
• Brazil 300 meter
• Caspian Sea 600 meter
• Venezuela 300 meter
Common: Deep water nature of the provinces
Flow Control in Oil/Gas Wells and
Pipelines
Callenges for Deep Water Developments
(Hassanein and Fairhurst, BP 1997)
Flow Control in Oil/Gas Wells and
Pipelines
Flow Control
The ability to actively or passively manipulate a flow field in order to effect a beneficial change.
(Gad-el-Hak, 1989)
Flow Control in Oil/Gas Wells and
Pipelines
Flow assurance
The ability to produce hydrocarbon fluids economically from the reservoir to export over the life of a field in any environment. (Forsdyke 1997)
Challenges: Hydrates Wax/paraffin deposition Fluid control Scale Emulsions Slugging Flow control Sand
Flow Control in Oil/Gas Wells and
Pipelines
Flow control: emulsion viscosity
Use of emulsion breaker to lower viscosity
Oil-water mixtures:Increase in viscosity closeto inversion point
0 20 40 60 80 100
Water cut (%)
0
50
100
150
200
250
300
350V
isco
sity
(m
Pa*
s) 2 m/s without emulsion breaker2 m/s with emulsion breaker
Emulsion viscosity as a function of water cut
Flow Control in Oil/Gas Wells and
Pipelines
Sand Control
• Sand will follow the oil and gas from the reservoir
• Sand can deposit in the pipeline and process equipment
• Oscillating pressure and well production will increase sand production
Flow Control in Oil/Gas Wells and
Pipelines
1. Introduction to flow control 2. Multi-phase flow with emphasis on slug flow3. Stabilization of flow in Oil/Gas wells and pipelines4. Examples of flow control for selected oil and gas
fields5. Conclusions
Outline
Flow Control in Oil/Gas Wells and
Pipelines
Multiphase Transport
• Flow with one or several components in more than one phase– Gas-liquid flows
– Gas-solid flows
– Liquid-solid flows
– Three-phase flows (e.g. gas-oil-water)
• Simulation tools– Industry standard: OLGA (two fluid model)
– PETRA objectoriented implementation in C++
Flow Control in Oil/Gas Wells and
Pipelines
Horizontal Two-Phase Flow
• Segregated flow– Stratified
– Annular
– Wavy
• Intermittent– Slug flow
– Plug flow
• Distributive flow– Bubble/mist flow
– Froth flow
Flow Control in Oil/Gas Wells and
Pipelines
Example – horizontal slug flow
From Multiphase Flow Laboratory, TrondheimMovie provided by John-Morten Godhavn, Statoil
Flow Control in Oil/Gas Wells and
Pipelines
Inclined flow
• Waves!
Flow Control in Oil/Gas Wells and
Pipelines
Horizontal Flow Map
• Flow pattern map for horizontal flow
• Often specified in terms of superficial velocity of the phases
Annular
Slug
Stratified WavyStratified
Bubble
-1°
+1°
Flow Control in Oil/Gas Wells and
Pipelines
Vertical flow
• Bubble flow– Continuous liquid phase with
dispersed bubbles of gas
• Slug flow– Large gas bubbles
– Slugs of liquid (with small bubbles) inbetween
• Churn flow– Bubbles start to coalesce
– Up and down motion of liquid
• Annular flow– Gas becomes the continuous
phase
– Droplets in the gas phase
Flow Control in Oil/Gas Wells and
Pipelines
Example - vertical flow
From Multiphase Flow Laboratory, TrondheimMovies provided by John-Morten Godhavn, Statoil
Slug flow Bubble flow
Flow Control in Oil/Gas Wells and
Pipelines
Vertical Flow Map
• Partly dependent on upstream geometry
Flow Control in Oil/Gas Wells and
Pipelines
Slug Flow -
A fascinating but unwanted and damaging flow pattern
Flow Control in Oil/Gas Wells and
Pipelines
Consequences of Slugging
• Variations in flowrate to 1.stage separator– Shutdowns, bad separation, level variations– Pressure pulses, vibrations and tearing on
equipment– Flow rate measurement problems
• Variations in gasflow– Pressure variations– Liquid entrainment in gas outlet– Flaring– Flow rate measurement problems
Flow Control in Oil/Gas Wells and
Pipelines
• ”Normal” steady slugs – Hydrodynamic slugging– Unaffected by compressibility– Incompressible gas (high pressure) or high liquid rate– Normally not an operational problem– Short period
• Slugs generated by compressibility effects– Severe slugging in a riser system (riser induced)– Hilly terrain slugs (terrain induced)– Other transient compressible effects– Long period
• Transient slugs– Generated while changing inlet rate
• Reservoir induced slug flow
Slug Flow Classification
Flow Control in Oil/Gas Wells and
Pipelines
Slug flow generation
(Oliemans 1994)
• Wave growth due to Kelvin Helmholtz instabilities
• Slug growth criteria (the slug has to grow to be stable)
Hydrodynamic slug growth Two criteria:
Flow Control in Oil/Gas Wells and
Pipelines
Hydrodynamic slugging
• Formed when waves reach the upper pipe wall; the liquid blocks the pipe, and waves grows to slugs
• Short slugs with high frequency
• Gas rate, liquid rate and topography influences degree of slugging
• Triggers riser slugging
Eksempel fra flerfaseanlegget på Tiller.
Flow Control in Oil/Gas Wells and
Pipelines
Slugs from Gas Lift
Annulus
• Gas lift is a technology to produce oil and gas from wells with low reservoir pressure
• Gas lifts can result in highly oscillating well flow
• Casing-heading instabilities
Flow Control in Oil/Gas Wells and
Pipelines
Slug formation in pipeline/riser
1. Initiation and Slug formation• Gas velocity too low to sustain liquid film
in riser
• Liquid blocking
• Gas pressure increases in pipe
• No/low production
2. Slug production• Gas pressure equals liquid head
• Liquid accelerates when gas enters riser
• Large peak in liquid flow rate
3. Gas blow down• Pressure drops as gas enters riser
• Gas bubbles become continuous, liquid film at wall
• Gas velocity too low...
4. Liquid fallback• Liquid film flows down the riser
Flow Control in Oil/Gas Wells and
Pipelines
Conditions for severe slugging
• Flow maps for pipe/riser
• Conditions from literature– Bøe ’81, Taitel et al ’90, Schmidt
et al ’85, Fuchs ‘87
– Pressure limits
– Depend on pipe geometry
• Based on steady state analysis– Inaccessible variables
• Dynamic simulation
• When does slugging occur?– Pipelines with dips and humps
– Low gas-oil ratio
– Decreasing pressure
– Long pipelines
– Deep water production
Flow Control in Oil/Gas Wells and
Pipelines
Important Severe Slugging Parameters
• Gas and oil flowrate
• Pipeline pressure
• Upstream geometry
Graph from Fuchs (1997)
Flow Control in Oil/Gas Wells and
Pipelines
Important Severe Slugging Parameters
• Gas and oil flowrate
• Pipeline pressure
• Upstream geometry
Pressure:30 bar
Pressure:50 bar
Figures from Fuchs (1997)
Flow Control in Oil/Gas Wells and
Pipelines
Important Severe Slugging Parameters
• Gas and oil flowrate
• Pipeline pressure
• Upstream geometry
Strigh
t pip
e up
streamP
ipe b
uck
ling u
pstream
Flow Control in Oil/Gas Wells and
Pipelines
1. Introduction to multi-phase flow
2. Slug flow
3. Stabilization of flow in Oil/Gas wells and pipelines
4. Examples of flow control on some oil and gas fields
5. Conclusions
Outline
Flow Control in Oil/Gas Wells and
Pipelines
Slug reduction/elimination techniques• Design changes
– Slug catchers and separators– Rate/GOR change or pressure change– Pipe diameter regulation (use of many smal pipes) (Yocum, 1975)– Gas injection at riser base (Hill, 1990)
– Pipe insertion (self induced gaslift) (Sarica & Tengesdal, 2000)
– Venturi tubes– Dynamic simulation (Xu et al, 1997)
• Operational changes– Choking (Schmidt et al., 1979, Taitel, 1986, Jansen et al., 1996)
– Feed-forward control of separator level– Dynamic simulation (Xu et al., 1997)
– Pigging operations– Use of flow-improver– Foaming (Hassanein et.al., 1998)– Artificial gas lifts– Optimise well production– Increase gas injection in well
• Feedback control– Miniseparators– Active choking– Model based regulation
Flow Control in Oil/Gas Wells and
Pipelines
Robust design -
Gas injection at riser base(Hill, 1990)
+ •Reduced static head (weight of liquid)
• Prevent severe slugging
• Smoothen start-up transients
Qgas
-
• Large amounts of injection gas needed
• Extra injection pipe needed
Flow Control in Oil/Gas Wells and
Pipelines
Robust design -
Self gas lifting(Sarcia & Tengesdal, 2000)
+ • Reduced static head (weight of liquid)
• Prevent severe slugging
• Smoothen start-up transients
• No extra injection gas needed
-
• Extra injection pipe needed – will be expensive
Flow Control in Oil/Gas Wells and
Pipelines
Robust operation –
Choking(Schmidt et al., 1979, Taitel, 1986, Jansen et al., 1996 )
+ • Higher pressure and smaller severe slug flow regime
• Easy and cheap technique
-
• Manual work
• Lower capacity of pipe
Flow Control in Oil/Gas Wells and
Pipelines
Feedback control –
Active Choking(Statoil, 2003)
+ • Reduces the slug length by opening the hock valve when the slugs starts to develop – sucks the slug up.
• Easy and cheap technique
-
• Lower capacity of pipe
• Can be a problem for deep waters 1.stage separator
PICSP
D
PT
MV
PT
Used as regulation valve
Flow Control in Oil/Gas Wells and
Pipelines
Robust operation –
Optimize Well Production(ABB)
OptimizeIT Active Well Control
- - stabilizes the oil production stabilizes the oil production from the well by active from the well by active control of the production control of the production and/or injection chokeand/or injection choke
Flow Control in Oil/Gas Wells and
Pipelines
Robust operation –
Increased/controled gas injection rate in gas lifts
+ • Increased gas flow rate and GOR (less chance for severe slugging)
• Less static head
-
• Increased frictional losses
• Joule-Thomson Cooling
• Need injection gasAnnulus
Flow Control in Oil/Gas Wells and
Pipelines
Feedback control -
Miniseparators(Hollenberg, 1995, S3TM)
• Principle is to keep the mixture flow rate constant through the operation with a control vale.
• Difficulty in measuring flowrates is solved by using minisparators
-
• Lower capacity of pipe
Flow Control in Oil/Gas Wells and
Pipelines
Slug reduction/elimination techniques• Design changes
– Slug catchers and separators– Rate/GOR change or pressure change– Pipe diameter regulation (use of many smal pipes) (Yocum, 1975)– Gas injection at riser base (Hill, 1990)
– Pipe insertion (self induced gaslift) (Sarica & Tengesdal, 2000)
– Venturi tubes– Dynamic simulation (Xu et al, 1997)
• Operational changes– Choking (Schmidt et al., 1979, Taitel, 1986, Jansen et al., 1996)
– Feed-forward control of separator level– Dynamic simulation (Xu et al., 1997)
– Pigging operations– Use of flow-improver– Foaming (Hassanein et.al., 1998)– Artificial gas lifts– Optimise well production– Increase gas injection in well
• Feedback control– Miniseparators– Active choking– Model based regulation
Flow Control in Oil/Gas Wells and
Pipelines
1. Introduction to flow control and multi-phase flow2. Slug flow3. Stabilization of flow in Oil/Gas wells and pipelines4. Examples of flow control on some oil and gas fields5. Conclusions
Outline
Flow Control in Oil/Gas Wells and
Pipelines
4700m
Slugg Control at Heidrun NordflankenUse of active slug control
Simulation before startup indicated slugging Field measurements after startup proved slugging Continuous slug regulation since startup Also in use under startup of new wells
D
Elevation -355m
Flow Control in Oil/Gas Wells and
Pipelines
Slugging in riser Heidrun D-line
Trykk toppside oppstrøms choke
•Large pressure variations•Periods ca. 17 minutes.•Disapears when chocking upstream
Tetthet toppside
Flow Control in Oil/Gas Wells and
Pipelines
Active Well Control at Brage A-21
Flow Control in Oil/Gas Wells and
Pipelines
2 2.5 3 3.5 4
76
78
80
82
84
86
88
Days
Brage WellCon data (Day 0 = 24-Aug-2001 07:59:00)
PT -13-217
Pres. [bar]Downhole pressure
OptimizeIT Active Well Control on Brage A-21
Starting Active Control
Flow Control in Oil/Gas Wells and
Pipelines
Conclusions
• Introduction to flow control• Unstable multiphase flow – what, why• Severe slugging in gas/oil pipelines• Methods for control of severe slugging• Still an unresolved problem for deep waters• Successful practical examples
Flow Control in Oil/Gas Wells and
Pipelines
Thanks
• Institute for Energy and Process Technology, NTNU
• Statoil
• Norwegian Research Council
• People who have helped my with this trial lecture Lars Imsland, Elling Sletfjerding, John Morten Godhavn
Flow Control in Oil/Gas Wells and
Pipelines
Flow control in petroleum production
• Noise suppression
• Drag reduction
• Water-oil flow
• Flow assurance
• Slug control
• Multiphase flow simulation
Flow Control in Oil/Gas Wells and
Pipelines
Drag reduction
• Internal flows (pipes, ducts)– ~100% skin friction
– Increased throughput
– Reduced pumping power
– Reduced pipe/duct size
• Wall modifications– Smoothing (paintings, coatings, pigging)
– Riblets (shark-skin)
– Compliant walls, flexible skin
– MEMS (Micro-electromechanical systems)
• Additives– Particles, dust, fibres
– Polymers, surfactants (Drag reducing agents)
– Micro-bubbles, fluid films