Gas Well Deliquification WorkshopSheraton Hotel, Denver, Colorado
February 22 - 24, 2010
New Perspectives on Gas WellLiquid Loading & UnloadingStefan Belfroid, TNO Science and Industry, Delft
Kees Veeken, Shell E&P Europe, Assen
Outline of Presentation
• Compare droplet size postulated by Turner againstdroplet size observed in nature and flow loop testing
• Recognise role of film reversal observed in flow loopexperiments and transient multiphase flow modelling
• Explore consequences for gas well deliquification
– Reduce droplet size
– Generate swirl
– Create foam
– Modify tubing wall
• Summary
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet Size in Turner – Big Rain
• Turner criterion equates liquid loading to dropletreversal i.e. gas rate where friction drag force ondroplet becomes less than gravity force on droplet
• Friction drag force depends on droplet size andshape
• Turner assumes a droplet size based on a largecritical Weber number We=30
• Turner droplet size and We is much larger thantypically observed in nature e.g. rain has We=8
Shear force Vs surface tension: We = gvg2/
Drag force coefficient: Cd = f(Re,shape)
Force balance: Dp3g/6 = Cdgvg
2Dp2 /8
Dp vg
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet Size in Flow Loop Tests
• Droplet size distribution has been measured in air-waterflow loop testing using PDA (Particle Dopler Anemometry)
• 50% of watermass flow carriedin droplet phase issmaller than 4mm
• Maximum dropletsize 10x P50droplet size
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Empirical Droplet Size
• Entrainment relation derived from lab data supportssmaller critical We i.e. smaller droplets
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet Reversal?
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
FDrag = FGravity (Downhole )
FDrag = FGravity (We llhead)
Turne rs c riterium (Downhole)Turne rs c riterium (Wellhea d)
Drop Diameter (m)
Gas
Vel
ocity
(m/s
)
Turner assumes unrealistic droplet size
Realistic droplets require lower velocity
• At Turner gas velocity realistic size droplets are notexpected to cause liquid loading
• Dropletreversal shouldonly occur at ½of Turner gasrate
• What is thencausing liquidloading?
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet Reversal?
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
FDrag = FGravity (Downhole )
FDrag = FGravity (We llhead)
Turne rs c riterium (Downhole)Turne rs c riterium (Wellhea d)
Drop Diameter (m)
Gas
Vel
ocity
(m/s
)
Turner assumes unrealistic droplet size
Realistic droplets require lower velocity
• At Turner gas velocity realistic size droplets are notexpected to cause liquid loading
• Dropletreversal shouldonly occur at ½of Turner gasrate
• What is thencausing liquidloading?
Droplet and Film Movement
• Flow loop tests show that liquid is transported both bydroplets up core and annular film up tubing wall
• Same air-water flow loop tests show that liquid loading iscaused by film reversal
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Film Reversal
• Film reversal model developed by Jos Van ‘t Westende(PhD Thesis TU Delft, 2008)
Experimental 13 m/s
Turner 15 m/s
Film model 18 m/s
OLGA 17 m/s
Air-water experimental*
http://repository.tudelft.nl/assets/uuid:3d8367ef-c426-4536-8bde-2c3498227acb/westende_20080114.pdf
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Use of Turner Criterion
• Turner criterion remains extremely useful engineering tool:film and droplet reversal depend on the same well andfluid parameters in a similar manner
QTurner ~ FTHP0.5.ID2
Turner Ratio, TR = Qmin / QTurner• SPE 123657introducesModified Turnercriterion, basedon field data andin line withmultiphase flowmodelling results
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Film Reversal in OLGA
• Movement of and exchange between droplet and filmincluded in OLGA multiphase flow modelling software
• OLGA specifies liquid transport in film and droplet phase
0 degrees deviation(75 bara, 0.1 m ID)
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Qmin=130e3 m3/d@ Pres=67.25 bar
Qgas=gas rate (e6m3/d)
FTHT=flowing tubing head temperature (degC)
Qwater=water rate (m3/d)
FBHP=flowing bottomhole pressure (bara)
Pres: 70 65 bar in 100 days
Vertical Well - 0.1 m ID - 50 bar FTHP
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Annular flow: droplet flow and filmflow both important
Holdup=0.007
Water film=1.7 m3/d
Total water=3.2 m3/d
Gas=0.184e6 m3/d
Flow regime=Annular
Pres=69.80 bar
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Liquid loading starts when film flow“flips” i.e. changes from upward todownward, generally starts atwellhead
Flip
Holdup=0.015
Water film=0.0 m3/d
Total water=2.4 m3/d
Gas=0.129e6 m3/d
Flow regime=Annular
Pres=67.40 bar
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Downward film flow increases holdupand shifts holdup downward,increase of droplet flow upwardpartly compensates for film flowdownward
Holdup=0.013
Water film=-0.2 m3/d
Total water=1.5 m3/d
Gas=0.117e6 m3/d
Flow regime=Annular
Pres=67.25 bar
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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At some point totalwater flow becomesdownward
Holdup=0.019
Water film=0.0 m3/d
Total water=0.7 m3/d
Gas=0.104e6 m3/d
Flow regime=Annular
Pres=67.25 bar
Reduce Droplet Size – Into Thin Air
• At small enough droplet size relaxation length will equalwell depth
• Small enoughdroplets could begenerated by largeshear forces i.e. veryhigh gas velocities
• Necessary choke sizewould result inexcessive pressureloss defeating thepurpose
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet and Film Exchange
• Flow loop tests highlight the continuous exchange ofliquid between film phase and droplet phase throughdeposition and entrainment
• Droplet relaxation length is typically short for larger sizedroplets
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Droplet Relaxation Length
• Relaxation length Vs droplet diameter for ID = 0.1 m
relLxen
xn /
0
)(
1 km
2 m
100 m
3 m3 m
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Reduce Droplet Size – Into Thin Air
• At small enough droplet size relaxation length will equalwell depth
• Small enoughdroplets could begenerated by largeshear forces i.e. veryhigh gas velocities
• Necessary choke sizewould result inexcessive pressureloss defeating thepurpose
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Generate Swirl – Lets Twist
–
• Spiral Flow = Helical Flow = VortexFlow– Norm Hein (2007 GWD Workshop, Denver)
• Vortices have “memory” i.e. persistover extended time and distance (100-1000 D)– Benefit observed both in lab testing and
field applications
– Improves film flow rather than droplet flow
– Promising as temporary measure e.g. whilewaiting for compression
– May require multiple tools to cover tubinglength depending on relaxation length
http://www.numaga.com/index.php/hd/cool/5400-vortex-cannon
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Generate Swirl – Lets Twist
–
• Spiral Flow = Helical Flow = VortexFlow– Norm Hein (2007 GWD Workshop, Denver)
• Vortices have “memory” i.e. persistover extended time and distance (100-1000 D)– Benefit observed both in lab testing and
field applications
– Improves film flow rather than dropletflow ! ?
– Promising as temporary measure e.g.while waiting for compression
– May require multiple tools to cover tubinglength depending on relaxation length
http://www.numaga.com/index.php/hd/cool/5400-vortex-cannon
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Create Foam – Tall Tale• Stable foam requires liquid
content between 10% and 40%,foam breaks up and turns intomist @ liquid fraction less than4% (SPE 86927)
• Liquid fraction in wellborerarely exceeds 1%, hencestable foam columns do notexist in wells
• Lower surface tension (2x-3x)reduces droplet size, increasesentrainment and increasesvelocity of film roll waves
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Create Foam – Tall Tale• Stable foam requires liquid
content between 10% and 40%,foam breaks up and turns intomist @ liquid fraction less than4% (SPE 86927)
• Liquid fraction in wellborerarely exceeds 1%, hencestable foam columns do notexist in wells
• Lower surface tension (2x-3x)reduces droplet size, increasesentrainment and increasesvelocity of film roll waves
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Modify Tubing – Die Zauberflöte
• Apply hydrophilic of hydrophobic coating
– Small scale lab tests show promising effects
T. Takamasa et al./International Journal of Heat and Fluid Flow 29 (2008) 1593–1602
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Modify Tubing – Die Zauberflöte
• Apply ID profile
– Small scale lab tests show promising effects
T. Takamasa et al./International Journal of Heat and Fluid Flow 29 (2008) 1593–1602
Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Modify Tubing – Die Zauberflöte
• Modify tubing wall to delayfilm reversal
• Apply hydrophilic ofhydrophobic coating
– Small scale lab tests showpromising effects
• Apply ID profile (smallscale – large scale)
– Smal scale lab tests showpromising effects
T. Takamasa et al./International Journal of Heat and Fluid Flow 29 (2008) 1593–1602
Summary
• Droplet size assumed by Turner is much larger than observed inflow loop tests
• Flow loop tests and multiphase modelling indicate that liquidloading is caused by flow reversal rather than droplet reversal
• Therefore deliquification must delay film reversal rather thandroplet reversal
• Droplet size reduction could help, but is impractical due toassociated pressure loss
• Swirl generation could help, may require installation at multipledepths
• Surfactant injection helps, but mechanism may be different thanassumed
• Tubing wall modification could help, under investigation
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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Feb. 22 - 24, 2010 2010 Gas Well Deliquification WorkshopDenver, Colorado
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