Gas Well Deliquification WorkshopSheraton Hotel, Denver, Colorado
February 23 - 26, 2009
Measured Plunger Rise Velocity Compared to Foss and Gaul Calculations
O. Lynn Rowlan, Echometer CompanyJames F. Lea, PLTech LLC
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Modified Foss and Gaul Rise Velocity Spread Sheet
• Accounts for added lift from formation gas production and for loss due to gas leakage on plunger rise
• If production & leakage set to zero, then calculations are original Foss & Gaul
• Industry recommends about 750 ft/min, usually 500- 1000 ft/min considered OK.
• Rising too fast wastes energy and causes wear and damage
• If plunger On BottomOn Bottom, then Spread Sheet Calculates Casing Pressure for a Specific Rise Velocity
Foss, D. L. and Gaul, R. B.: “ Plunger Lift Performance Criteria with Operating Experience-Ventura Field, “Drilling & Production Practice, API (1965),124-140.
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Concept of F&G Model: OriginalConcept of F&G Model: Original
P1 V1 = P2 V2
Pc, max when well ready to
openCasing
Volume OnlyPc,min, slug and plunger
surface
Casing & Tubing volume
P1 = Pc,max (Pressure Valve Opens) Pc,max = V2 /V1 P2
Pc,max = (Acsg+Atbg)/(Acsg) x P2
Pc,max = CPR x Pc,min
P2 = Pc,min (Pressure Plunger Arrives)
P2 V2P1 V1
Valve Opens, Valve Opens, Unloading Unloading BeginsBegins
Plunger Plunger Arrives, Arrives, AfterAfter--flow flow beginsbegins
Foss and Gaul based on Ideal Gas LawFoss and Gaul based on Ideal Gas Law
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Equations Used in Derivation Equations Used in Derivation
Lea, J F, Rowlan, O. L., and McCoy, J. N., “Plunger Lift Rise Velocity Prediction Model Plunger Lift “Open” Criteria”, SWPSC 2008, Lubbock, TX
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Pc,maxPc,max -- Initial Casing Pressure Initial Casing Pressure Just Before Well Opens To UnloadJust Before Well Opens To Unload
Four Methods Used to Calculate Pc,Max are:
1. Using a calculated friction factor and no production or leakage during plunger rise
2. NEW - Using a calculated friction factor and production and leakage during plunger rise.
3. ORIG F&G Using the original values of Pc and K with no leakage or production during rise from Foss and Gaul.
4. ORIG F&G NEW - using the original values of Pc and K with leakage and well production used during the rise of the plunger.
Pc,maxPc,max Calculated at Input Plunger Rise VelocityCalculated at Input Plunger Rise Velocity
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Plunger TargetTarget Velocity
Too Slow Target 750 ft/min
Gas Slips By PlungerMay Never Reach Surface
See SPE 14344, Defining the Characteristics and Performance of Gas-Lift PlungersBy L.N. Mower and J.F. Lea, Amoco Production Co., and E. Beauregard and P.L. Ferguson, Ferguson Beauregard Inc., 1985
Specific Rise Velocities (FPM) Pad w/Seal Ring 400 – 600Brush 400 – 600Pad 650 – 800Barstock 850 - 1000
Too Fast
Wastes Well psiDamages Equipment
Conventional Plunger Cycle[A] Valve Closes, [A] Valve Closes, ShutShut--in Begins in Begins and Pressure and Pressure Starts IncreasingStarts Increasing
[2] Shut[2] Shut--in in Valve Closed, Valve Closed, w/ Pressure w/ Pressure IncreasingIncreasing
[B] Valve [B] Valve Opens, Opens, Unloading Unloading BeginsBegins
[C] Valve [C] Valve Closes, Cycle Closes, Cycle Repeats Repeats
[4] Plunger Arrives, [4] Plunger Arrives, Tubing Pressure Tubing Pressure Spike Maximum, Spike Maximum, AfterAfter--flow beginsflow begins
PredictPredictRiseRise
VelocityVelocity
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Pressures During Cycle for Pressures During Cycle for Plunger Lift Well Plunger Lift Well ““SV AfterSV After””
Tubing Tubing PressurePressure
Acoustic Acoustic SignalSignal
Casing Casing PressurePressure
Time Time -- MinutesMinutes
PsigPsig
Load Factor = 0.50Load Factor = 0.50
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Load Factor <50% for Plunger to SurfaceLoad Factor <50% for Plunger to Surface
Load Factor: (Pcas Load Factor: (Pcas –– Ptub) / (Pcas Ptub) / (Pcas –– Pline) Pline) < 50%< 50%
(117.3(117.3--107)/(117.3107)/(117.3--64) 64) = 19%= 19%
Casing Casing PressurePressure can can NOT be less than NOT be less than Tubing Tubing PressurePressure, OR , OR Plunger Stops Coming Plunger Stops Coming to the Surfaceto the Surface
Pcas = 117.3Pcas = 117.3
Ptub = 107.0Ptub = 107.0
PlinePline = 64.0= 64.0
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Used Data Collected on 10 Conventional Plunger Wells to Test Calculations
Primarily Tested Conventional Dual Pad Plungers
Most wells were Vertical ~ 1 Horizontal well
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Inputs to Foss & Gaul Rise Inputs to Foss & Gaul Rise Velocity XLS (After SV)Velocity XLS (After SV)
0 = Original Foss and Gaul | 0 = Original Foss and Gaul | 2 = Foss and Gaul Modified. 2 = Foss and Gaul Modified. Tubing IDTubing ID = enter 1, 2, or 3 to pick ID= enter 1, 2, or 3 to pick IDPwhPwh = Line pressure when valve opened= Line pressure when valve openedPpPp = pressure to support plunger weight= pressure to support plunger weightDepthDepth = depth to bumper spring= depth to bumper springSlug,bblSlug,bbl = amount of liquid to be lifted= amount of liquid to be lifted
AvgAvg TempTemp = average well temperature, F= average well temperature, FSG, LiquidSG, Liquid = specific gravity of liquid= specific gravity of liquid% Liquid% Liquid = S Curve using Gas Rate= S Curve using Gas RateSG, gasSG, gas = specific gravity of gas= specific gravity of gasRise Velocity, ft/minRise Velocity, ft/min = Desired or Measured= Desired or Measured
As Plunger Rises Correct for Extra Gas:As Plunger Rises Correct for Extra Gas:Mscf/D ProducedMscf/D Produced = from formation during rise= from formation during riseMscf/D LeakingMscf/D Leaking = past plunger= past plungerCasing ID, InchesCasing ID, Inches = Used in Annular Area= Used in Annular Area
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Friction, f, gas & Liquid = friction factor Friction, f, gas & Liquid = friction factor
PweightPweight = accounts for weight of liquid slug = accounts for weight of liquid slug PfrictionPfriction = accounts for friction of liquid slug= accounts for friction of liquid slugPcPc = = PweightPweight + + PfrictionPfrictionKK = related to gas friction up the tubing= related to gas friction up the tubingPcminPcmin = casing surface pressure after slug and = casing surface pressure after slug and plunger arrive at surfaceplunger arrive at surfacePcmaxPcmax = casing pressure max without = casing pressure max without considering production and plunger leakage considering production and plunger leakage during riseduring risePcmaxPcmax, NEW, NEW = casing pressure build up = casing pressure build up considering production and plunger gas considering production and plunger gas leakage on plunger rise (must be more than leakage on plunger rise (must be more than PcminPcmin or correct inputs)or correct inputs)
Outputs From to Foss & Gaul Rise Outputs From to Foss & Gaul Rise Velocity XLS (After SV)Velocity XLS (After SV)
PcmaxPcmax of 130 of 130 PsiaPsia Predicted for 636 Ft/MinPredicted for 636 Ft/Min Average Rise VelocityAverage Rise Velocity
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Example Plunger Well Example Plunger Well ““After SVAfter SV”” is Installedis Installed
Expanding gas in Expanding gas in Casing Lifts Plunger Casing Lifts Plunger and Liquid to Surfaceand Liquid to Surface
636636Ft/MinFt/Min
If Casing If Casing PressurePressure Stops Stops Decreasing, Formation Decreasing, Formation Must Lift Plunger Fluid to Must Lift Plunger Fluid to SurfaceSurface
1000 Ft/Min1000 Ft/Min
500 Ft/Min500 Ft/Min
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Pc,max NEW Calculated 129.6 Psia for Measured Rise Velocity of 636 Ft/Min
Measured Casing Measured Casing Pressure 132 PsiaPressure 132 Psia
Rise Velocity Rise Velocity 636 Ft/Min636 Ft/Min
For Rise Velocity of For Rise Velocity of 750 Ft/Min ~ Shut750 Ft/Min ~ Shut--in in Casing Pressure Casing Pressure would be 135.3 Psiawould be 135.3 Psia
For Plunger Lift Well “After SV” Installed
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Pc,max NEW Calculated 129.6 Psia for Measured Rise Velocity of 636 Ft/Min
Rise Velocity Rise Velocity 230 Ft/Min230 Ft/Min
For Rise Velocity of For Rise Velocity of 750 Ft/Min ~ Load 750 Ft/Min ~ Load Factor would be 0.372Factor would be 0.372
For Plunger Lift Well “After SV” Installed
Load Load Factor 0.5Factor 0.5
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Standing Valve (Before & After)Standing Valve (Before & After)Pressure Shows Pressure Shows Liquid Pushed Liquid Pushed Out of TubingOut of Tubing
NO Standing ValveNO Standing Valve330 Ft/Min Fall330 Ft/Min Fall
With Standing ValveWith Standing Valve347 Ft/Min Fall347 Ft/Min Fall
Casing Pressure Casing Pressure Builds Holding Builds Holding Liquid in TubingLiquid in Tubing
10 Psi Lower FBHP10 Psi Lower FBHP
Difference in the travel times Difference in the travel times Chart looks like it is lifting fluidChart looks like it is lifting fluid
Rise Velocity:Rise Velocity:
636 with SV 636 with SV 792 w/o SV792 w/o SV
Flow rate Qin, SCF/D
P (bottom)
Cas & Tub, psia
Pt, Pc psia
Flow rate Qout, SCF/D
T u b i n g
D e p t h
Motor Valve
Flow Line
Gas Formation & Slips by PlungerGas Formation & Slips by Plunger
Formation
Well Model Allocates Gas between:Well Model Allocates Gas between: Casing Annulus, Tubing, Out of Formation, Casing Annulus, Tubing, Out of Formation, and Down Flow Line and Down Flow Line
1.1. Gas Volumes During Cycle based on Gas Volumes During Cycle based on Casing & Tubing Pressure & LiquidCasing & Tubing Pressure & Liquid
2.2. During ShutDuring Shut--in Gas flowing from in Gas flowing from Formation is Captured in the Formation is Captured in the Tubing/Casing AnnulusTubing/Casing Annulus
3.3. Use WellUse Well’’s IPR Determined From Shuts IPR Determined From Shut--in in Period To Calculate Flow Rate From Period To Calculate Flow Rate From Formation for Any Flowing BHPFormation for Any Flowing BHP
4.4. During Unloading Gas Volume Slipping During Unloading Gas Volume Slipping by the Plunger equals: by the Plunger equals: Gas volume leaving Casing + Gas volume Gas volume leaving Casing + Gas volume flowing from formation flowing from formation –– Gas Volume Gas Volume Remaining in Tubing when plunger Remaining in Tubing when plunger arrives at surface.arrives at surface.
Vol Tubing
Vol Casing
Where’s the Plunger
Liquid Height
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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1357 Scf Gas Slips Past Plunger while Unloading 1357 Scf Gas Slips Past Plunger while Unloading Liquid And Plunger to Surface (11min 26sec)Liquid And Plunger to Surface (11min 26sec)
[B][B]
Flow Rate from Formation Flow Rate from Formation from 102 to 126 MscfDfrom 102 to 126 MscfD
[C][C][3][3]
Valve OpenValve Open
UnloadingUnloading
Normal WellNormal Well
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Calculated ShutCalculated Shut--in Casing Pressure in Casing Pressure @ Measured Rise Velocity@ Measured Rise Velocity
1.1. Calculated Flow From Formation During Unloading using Well Calculated Flow From Formation During Unloading using Well Model to Allocate Gas between: Casing Annulus, Tubing, Out of Model to Allocate Gas between: Casing Annulus, Tubing, Out of Formation, and Down Flow LineFormation, and Down Flow Line
2.2. PcMaxPcMax, NEW ORIG using the original values of Pc and K with , NEW ORIG using the original values of Pc and K with leakage and well production used during the rise of the plunger leakage and well production used during the rise of the plunger [BEST] if Calculated Flow Rate From Formation Used [BEST] if Calculated Flow Rate From Formation Used
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Calculated ShutCalculated Shut--in Casing Pressure in Casing Pressure @ Measured Rise Velocity@ Measured Rise Velocity
1. Average Daily Gas Flow Rate is used for Flow from Formation During Unloading portion of Cycle
2. PcMax, Using a calculated friction factor and no production or leakage during rise [BESTBEST] if Average Daily Gas Flow Rate is used for Flow From Formation
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Comments/ConclusionsComments/Conclusions1.1. Modified Foss and Gaul model presented. Modified Foss and Gaul model presented. 2.2. Data from ten wells compared favorably to the model (NOT Data from ten wells compared favorably to the model (NOT
enough data to statistically decide on best model options)enough data to statistically decide on best model options)3.3. Prediction accounts for liquid load, frictional effects, Prediction accounts for liquid load, frictional effects,
tubular sizes and lengths, surface line pressure and fluid tubular sizes and lengths, surface line pressure and fluid properties.properties.
4.4. Predicted Pc,Max compares to within an average 1% error Predicted Pc,Max compares to within an average 1% error if Average Daily Gas Flow Rate is used for Flow From if Average Daily Gas Flow Rate is used for Flow From Formation and New Friction Factors Formation and New Friction Factors
5.5. PcMaxPcMax, NEW ORIG 2.5% error using the original values of , NEW ORIG 2.5% error using the original values of Pc and K with leakage and Formation Gas well production Pc and K with leakage and Formation Gas well production from New Well Modelfrom New Well Model
Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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Feb. 23 - 26, 2009 2009 Gas Well Deliquification Workshop Denver, Colorado
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