6 Gas Lift Troubleshooting (4)

Gas Lift Troubleshooting

Gas Lift Troubleshooting

GAS LIFT TROUBLESHOOTING

IS A PROCESS !!

NOT A PROJECT !!

GAS LIFT TROUBLESHOOTING

CONSISTS OF

1. DATA GATHERING

2. ANALYSIS

3. IMPLEMENTATION

© Weatherford. All rights reserved.

ARTIFICIAL LIFT SYSTEMS

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PREVENTATIVE MAINTENANCE

UNLOADING THE GAS LIFTINSTALLATION

IS THE MOST CRITICAL TIME IN THE LIFE OF AN ISTALLATION

CAN DESTROY THE SEATS PREVENTING UPPER VALVE CLOSURE

GL Well Unloading Sequence

G. L. Well Unloading Sequence Part 2



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Gas Lift Diagnostics

HIGH FEED-IN WELLS

Are the most difficult to prevent valve damage

High feed-in wells also take on fluids at high rates

Most of the fluids will go into formation during unloading

High rates of fluid flow going through the valves

Can cut out valves quickly

1 2 3 4 5 6 7 8 9 10 11 12 13

S1S2

0

200

400

600

800

1000

1200

Inje

ctio

n G

as V

olu

me,

MC

F/D

Time, 100 Minutes

Gas Lift Unloading Schedule

API C Value

Inj Gas Volume

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

S1

0

100

200

300

400

500

600

700

800

900

1000

Series1Series2

GAS LIFT WELL UNLOADING SEQUENCE

ELAPSED TIME, 100 MINUTES

INJECTION GAS VOL

API "C" VALUE = 900



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SURFACE CHOKES

A WELL SHOULD NOT BE UNLOADED AGAINST A SURFACE CHOKE UNLESS THE WELL IS EXPECTED TO COME IN FLOWING

IN CASE OF SAND PRODUCTION, CONTROL THE PRODUCTION RATE WITH INPUT GAS NOT A CHOKE

CHOKES REDUCES PRODUCTION RATE

CHOKES CAUSE EXCESSIVE GAS USAGE



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DIAGNOSTICS

Optimizing Production

• Increase injection 50 to 100 mcf per day• Give well time to stabilize 24 hrs is

recommended.• If production rate increases continue

increasing until rate drops.• Low injection rate back to last rate.



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•GAS LIFT PROBLEMS ARE INDICATED BY:

•HEADING

•TAKING INSUFFICIENT INJECTION VOLUMES•TAKING EXCESSIVE INJECTION VOLUMES

•LOSS OF PRODUCTION RATE



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Areas where problems can exist:

INLET

OUTLET

SUB-SURFACE



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GAS LIFT WELL’S ARE SUBJECT TO BUT NOTLIMITED TO THE FOLLOWING OPERATINGPROBLEMS:INLET:

EXCESSIVE INJECTION GAS VOLUMES

Injection choke sized too large - Injection pressure at or above max

operating pressure - Causes re-opening of upper valves - Reduction in production rate

Gas Lift Performance Curve



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Most gaslift design programs are static.They assume the annulus pressure changes as eachlower valve is uncovered. This will happen only ifthe injection rate is matched to the flow rate throughthe valve. In most cases, the annulus pressurechanges continuously during the unloading phase.



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LOW INJECTION GAS VOLUMES

INJECTION GAS CHOKE SIZED TOO SMALL

- Heading

- Reduction in production rate

- Can prevent well from unloading

Freezing or plugged injection choke



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HIGH INJECTION PRESSURE WITH LOW INJECTION VOLUME:

-OPERATING VALVE MAY BE PARTIALLY PLUGGED

-HIGH TUBING PRESSURE REDUCING THE DIFFERENTIAL

AT THE OPERATING VALVE

-INDICATION OF TEMPERATURE EFFECT

-CAN KEEP WELL FROM WORKING TO DEEPER GLV’S



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LOW INJECTION PRESSURE

- VALVE PRESSURES SET TOO LOW

- PLUGGED SURFACE VALVES

- FREEZING

- GAS DISTRIBUTION LINES MAY BE TOO SMALL

ACCURACY OF GAUGES AND SURFACE MEASURINGEQUIPMENT



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OUTLET PROBLEMS

HIGH BACK PRESSURE

- CHOKES OR CHOKE BODIES

- LONG OR UNDERSIZED FLOW LINES

- BUILDUP OF SALT, PARAFFIN, SCALE

- HILLY TERRAIN

- HIGH SEPARATOR PRESSURE

CAN CAUSE: OPERATION FROM UPPER VALVES

EXCESSIVE GAS USAGE

REDUCED PRODUCTION



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DOWNHOLE PROBLEMS

WELL HEADING

- GAS LIFT VALVE PORTS SIZED TOO LARGE

- ORIFICE VALVE NOT SIZED PROPERLY

- LOW INJECTION GAS RATE

- TEMPERATURE INTERFERENCE

- TUBING SIZED TOO LARGE

- LIMITED FEED-IN FROM THE FORMATION



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WELL NOT TAKING INJECTION GAS

- FREEZING OR PLUGGED INJECTION VALVE

- TEMPERATURE PROBLEMS

- GAS LIFT VALVE SET PRESSURES TOO HIGH



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INSTALLATION STYMIED AND WILL NOT UNLOAD

- HEAVIER FLUID GRADIENT THAN ANTICIPATED

- VALVE PRESSURES SET TOO HIGH

- VALVE SPACING IS TOO WIDE

- TEMPERATURES ARE INCORRECT



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WELL CIRCULATING DRY GAS

- OPENING UPPER GLV’S

- HOLE IN THE TUBING

- ORIFICE VALVE WITH NO FEED-IN

- HANGER OR PACKER LEAK



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VALVE HUNG OPEN

- INJECTION PRESSURE BLEEDS DOWN BELOW THE

CLOSING PRESSURE OF THE GLV’S

- COULD BE TRASH OR SALT BUILDUP

- CUT OUT SEAT FROM IMPROPER UNLOADING

- BELLOWS FAILURE



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HOLE IN THE TUBING

- LOW INJECTION PRESSURE

- EXCESSIVE GAS USAGE

- REDUCED PRODUCTION RATE

- HEADING



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TroubleshootingDiagnostic Tools

Wireline-tagging fluid/check perfs for fillEchometerWell Tests-performed properlyInjection Gas Measurement- in and outTwo or Three Pen Charts- every wellPressure/Temperature Surveys- performed properly



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PRIORTIZE CANDIDATES

FLOWING SURVEYS ARE MOST ACCURATE

FLOWING SURVEYS ARE ALSO MOST COSTLY

PRIORTIZE CANDIDATES BY THE LEAST EXPENSIVE METHODS FIRST



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TAGGING FLUID - WIRELINE UNIT

PROBLEMS THAT CAN BE INDENTIFIED:

PLUGGED OR OBSTRUCTRED TUBING

PARAFFIN, SCALE OR OTHER DEPOSITS

FILL-IN OVER THE PERFORATIONS

ABNORMALLY LOW FLUID LEVELS

ABNORMALLY HIGH FLUID LEVELS



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TAGGING FLUID - WIRELINE UNIT

LIMITATIONSCAN GIVE INCORRECT ESTIMATION OF OPERATING VALVE

-FEED-IN WILL OFTEN RAISE FLUID LEVEL

-FLUID FALLBACK WILL ALWAYS OCCUR-BOTH WILL GIVE WRONG ESTIMATION OF OPERATING VALVE

INPUT GAS SHOULD BE CLOSED PRIOR TO CLOSING THE WING VALVE (WILL DRIVE THE FLUID LEVEL DOWN)



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TUBING - CASING COMMUNICATION-ONE OF THE MOST COMMON GAS LIFT PROBLEMS

-OFTEN GOES UNDETECTED

-DIFFICULT TO PROVE

TO PROVE COMMUNICATION EXISTS-SHUT IN WELL WITH WING VALVE

-LEAVE INJECTION GAS ON UNTIL WELL EQUALIZES

-BLEED CASING DOWN AS FAST AS POSSIBLE



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TUBING -CASING COMMUNICATION

IF TUBING PRESSURE FALLS AT ALL, THERE ISCOMMUNICATION

IF THE TUBING PRESSURE DOES NOT FALL,COMMUNICATION WAS NOT PROVEN BUTSTILL MIGHT EXIST



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TUBING -CASING COMMUNICATION

OTHER PROCEDURES:

EQUALIZE-

BLEED CASING DOWN-

SHOOT ECHOMETER.

If casing fluid level rises, there is communication



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TUBING-CASING COMMUNICATION

OTHER PROCEDURES:

SET TUBING PLUG

FILL TUBING WITH WATER AND PRESSURE UP

IF COMMUNICATION THEN THE CASING PRESSURE WILL RISE



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MEASUREMENT OF GAS VOULMES - IN AND OUT

l DETERMINE EFFICIENCY OF INJECTION GAS

l DETECT ADDITONAL GAS CONSUMPTION RIGHT AWAY

l OUTPUT HELPS DETERMINE FGOR

l HELPS DETECT HOLES IN THE CASING

l SET UP SO EACH WELL CAN BE TESTED



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WELL TESTS

l DETECT CHANGES IN PRODUCTION EARLY

l DETECT WATER CUT INCREASES

l SHOULD BE OF LENGTH OF TIME TO BEMEANINGFUL

l OFTEN ENOUGH TO CATCH PROBLEMS EARLY



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WELL TEST PREPARATIONSTABILIZATIONTO ENSURE THAT THE DATA IS REPRESENTATIVE OF

ACTUAL WELL PERFORMANCE:

INDICATIONS

l CONSTANT WELLHEAD PRESSURE

l CONSTANT GAS-PRODUCTION RATE

l CONSTANT FLUID PRODUCTION RATE



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WELL TEST PREPARATION

EQUIPMENT CHECKNEED PROPERLY MAINTAINED EQUIPMENT TO RESULT IN

ACCURATE WELL TESTS………CHECK

l FOR LEAKAGE

l OPERATION OF ALL CONTROL VALVES

l TO BE SURE WELL FLUID IS PROPERLY ISOLATED

l CALIBRATION OF FLUID AND GAS METERS

l ALL PRESSURE GAUGES

l THAT ORIFICE PLATE IS CLEAN, FLAT AND FREE OF NICKS



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Gas Lift Well Flowing Survey

TROUBLESHOOTING

Documents

6 Gas Lift Troubleshooting (4)