measured plunger rise velocity compared to foss and gaul ... · gas well deliquification workshop...

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.


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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measured plunger rise velocity compared to foss and gaul ... · gas well deliquification workshop...

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