LiquidLoad.pdf

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5/11/2009

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Liquid LoadingDave Barry


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Liquid Loading

All gas wells, at some time during there producing life, willexperience liquid loading problems

Once Flowrate drops below a certain rate, the well will begin toload up

The amount of liquid produced does influence how quickly thesubsequent loading up process takes


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Critical Velocity

Gas velocity (Flowrate) in the tubing has drops below the minimum

required to move liquids up and out of the wellbore.

Liquids are settle in the bottom of the well tubing.

Gas flows in heads (slug flow) or bubble flow (gas bubbles through

liquids).

Loads up during natural flow.


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Typical Production Decline Curve

WellP

roduction

Typical Gas Well Production Decline

Time

NormalDecline

Onset Of Liquid Loading

Deviation

Plunger Installed

CumulativeProductionIncrease

Forecasted Decline with no Intervention


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Popular Remedies

Subsurface

Velocity Tubing Stings (Requires

Workover)

Pumping Unit (Expensive to Operate)

Electric Submersible Pumps (Expensiveto install, expensive to work on, expensive to operate)

Plunger Lift (Lowest Cost to Install, easy tooperate, low recurring costs)

Surface

Venting (Environmental Issues)

Intermitting (Good 1st Step, but limitedtime usage)

Soaping (Messy and Expensive)

Chemical Injection (Expensive)

Gas Lift (Works, but have to buy back gasto inject)

Compression (Maintenance &Expensive)


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Comparing Remedies

Criteria

Lowest flowing bottom hole pressure desired

Equals Lowest casing pressure

Mechanical limitations

Limit Choices

Cost Analysis

Choice has to make economic sense

Have to make more money, not just more oil/gas

Operator Capabil ities

Operators can do what they are trained to do Must learn required skills


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What is Plunger Lift

Technique used to optimize gas production.

Steel plunger is inserted into the production tubing.

Well shut-in causes plunger to fall allowing fluid to collect above

plunger.

Different techniques are used to decide how long to shut in and flowthe well.

Downhole pressure is used to lift the plunger and fluid to surface.

Goal is to increase gas production by keeping liquid off formation.

Generally speaking these wells dont have enough constant

downhole pressure to free flow into a gathering system.


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Candidate Selection: Is Plunger Lift Appropriate?

Does the Gas to Liquid Ratio meet the minimum

requirements? 400 scf per bbl per 1000' of lift depth

Does the shut in pressures meet minimum

requirements? Load Ratio


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GasGas

FlowFlow

MistMist SlugSlug BubbleBubbleAnnularAnnular

Gas Well Life Cycle: Plunger Lift

Decreasing Gas VelocityDecreasing Gas Velocity


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Typical Plunger Lift Wellhead Setup

Lubricator / Catcher

Collar Stop / Springs

Plunger

Controller

Tubing Xdcr

Casing Xdcr

Arrival Switch

A typical system consists of:

Collar Stop & Spring

Plunger

Lubricator / Catcher

Controller

Master Valve


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Typical Wellhead Hardware Detail

Tubing Transducer

Arrival Switch

Casing Transducer

Latching Solenoid


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Plunger Force Balance

101) Stored casing pressure freely acting on the

cross-section of the plunger2) Stored reservoir pressure acting on the cross-

section of the plunger, based on inf lowperformance

3) Weight of the liquid above the plunger4) Weight of the plunger5) Friction of the fluid with the tubing6) Friction of the plunger with the tubing7) Gas friction in the tubing8) Gas slippage upward past the plunger9) Liquid slippage downward past the plunger10) Surface pressure (line pressure and

restrictions) acting against the plunger travel4

3

7

5

8

6 1

9

2


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Plunger Products

Pa d P l u n g e r s h a v e

i n t e r l o c k i n g s t a i n l e s s s t e e l

p a d s t o c r e a t e a s u p e r i o r

s e a l . Th e s p r i n g - l o a d e d

p a d s a r e a lw a y s e x p a n d e d

y e t h a v e e n o u g h f l e x t o

a l l o w t h e p l u n g e r t o f a l l

t h r o u g h m i n o r t u b i n g

a n o m a l i e s .


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Plunger Products

Fi b e r p l u n g e r s Fi b e r p l u n g e r s ,, w i t h i t s w i t h i t s n y l o n s e a l i n g e l e m e n t , i s n y l o n s e a l i n g e l e m e n t , i s

u s ed i n w e a k e r w e l l s a n d u s ed i n w e ak e r w e l l s a n d s a n d p r o d u c i n g w e l l s . N o s a n d p r o d u c i n g w e l l s . N o

m o v i n g p a r t s m a k e s i t t h e m o v i n g p a r t s m a k e s i t t h e

i d e a l p l u n g e r w h e r e s a n d i s i d e a l p l u n g e r w h e r e s a n d i s

p r e s e n t .p r e s e n t .


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Down Hole Products

D o w n h o l e sp r i n g s D o w n h o l e sp r i n g s

a n d s t o p s a r e a n d s t o p s a r e

e n g i n e e r e d a n d e n g i n e e r e d a n d

m a n u f a c t u r e d in a m a n u f a c t u r e d i n a v a r i e t y o f v a r i e t y o f

c o n f i g u r a t i o n s c o n f i g u r a t i o n s ..


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Inflow Performance Analysis for Plunger Lift

Example of using inflow performance analysis to estimate plunger liftperformance. Chart shows production increase resulting fromreducing liquid hydrostatic pressure with a plunger lift system.


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Inflow Performance Relationship

Optimum Performance Cycle Frequency equals smallest liquid loads Smallest liquid load equals lowest BHP requirements Lowest operating BHP equals best inflow performace

Smallest

LiquidLoads

MostCycles

Lowest

BHPRequirements

Best Inflow

Performance$$$$$$


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Plunger Lift vs. Gas Production Theory

The producing tendency of plunger lift is directly opposed to that of the well.

Plunger lift requires an increase in casing pressure for increased production.

The well requires a decrease in casing pressure for increased production.

The compromise that always yields the greatest production is found whencycling the plunger at the maximum frequency possible without killing thewell.

J im Hacksma (Consultant)

1972, Users Guide to Plunger Lift Performance


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Plunger Lift States

Closing Valve

Closing Valve

Valve Closed

(Plunger on Bottom)

Valve Open

Flowing

Plunger Arrived

Arriving

Falling

Waiting

Falling

Valve Closed

Waiting

Valve Open

Plunger Arrived

Arriving

Flowing


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Valve Closed (State 2)

1) Timer

2) Tubing - LineCasing - Tubing / Casing - Line

3) Casing - LineCasing Tubing / Fluid Gradient

4) Casing - Line & Tubing - Line

5) Casing - Tubing

6) Casing Tubing & Tubing - Line

7) Load Ratio

8) Tubing Pressure

9) Casing Pressure

10) Static Pressure

11) Slug Size

12) Optional Input (2)

l i i ( )


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Plunger Arriving (State 3)

Arrival Times

Minimum

Maximum

Slow

Fast

Close A Valve or Open B Valve

Tune for faster next cycle

Dont tune(ascension velocity is correct)

Tune for slower next cycle

Dont tune(plunger may not have reached bottom)

Recommended Ascension Velocity:750 1,000 ft/min

Aft fl (St t 6)


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Afterflow (State 6)

1) Timer

2) Turner

3) Load Ratio

4) Differential Pressure

5) Flowrate

6) Tubing - Line

7) Casing - Tubing

8) Tubing Pressure

9) Casing Pressure

10) Static Pressure

11) Slug Size

12) Optional Input (2)


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Foaming

Reduces surface tension

Reduce the density of the liquid droplets

Therefore reduces the required Critical Velocity

Works best on wells with >= 50% Water

Advantages

1. Simple & inexpensive option for low ratewells. Proportional to liquid water rate.

2. No downhole equipment required.

Works best with a capillary tube.3. Gas velocities of 100 to 1,000 fpm.

Disadvantages

1. Foam carryover or liquid emulsion problems.

2. Effectiveness depends on type amount of wellfluids. Wells producing >50% condensate

may not foam.

Ch i l I j ti


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Chemical Injection

Gas Flow

Casing

Tubing

Pneumatic Valve

G4XRCPulse Meter

Chemical Injection Tank

Chemical Injection Pump

Ch i l I j ti


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Chemical Injection

Lowers the Critical Velocity needed to lift fluids to thesurface

Precise Injection of Chemical

Increased Revenues

Alarm Monitoring Controls either Motor Driven Pump or Piston Pump

S Sti k L h


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Soap Stick Launcher

S Sti k L h C t l


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Soap Stick Launcher Control

Control Launcher based on Flowrate or Critical Rate

Monitors Flow to determine if another Stick is necessary

Tracks Sticks remaining in Launcher, alarms when low

Set # of Sticks to drop before shut-in Reset on increase Flowrate

What is Automation?


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What is Automation?

What Does Automation Mean for YOU.

Spend less time doing tedious manual steps to accomplish simple tasks.

Become more efficient by learning to use the system or systems to work for

you, not you working the systems.

Let the systems help you become proactive to prevent issues, rather thanreactive when an issue happens.

Let the systems make your job easier.

Q ti


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Questions


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