Post on 13-Feb-2018
Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 1
Leak Metering Gas Lifted Wells
• Morten Kvernvold, MD
• ScanWell AS
36th Gas-Lift Workshop Stavanger, Norway February 4 – 8, 2013
Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 2
Challenges
Well Integrity Failures
• According to PSA a conventional
well, which is converted to gas lift,
will experience well integrity failures
within two years of production.
Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 3
Challenges
Optimizing Production
• Gas lift hides
innefficiencies
• Without regular
surveillance, gas lift
wells are far less likely
to produce at optimal
levels.
Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 4
Risk Assessment
2007 – PSA & Sintef finds well integrity issues
on 25% of the well on the NCS.
PSA & OGN Guideline 117 (2007) - Evaluation
– 4.2.1 Source, mechanism and location of leaks
– 4.2.2 Leak rate
– 4.2.3 Annulus pressure
– 4.2.4 Hydrocarbon gas volume and mass
– 4.2.5 Escalation potential
New guidelines and redesigned audits have reduced
the number of red/orange wells to 8.6% in 2012.
Identifying & Understanding SCP
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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Requires custom designed equipment & competency
• Dependancy between pressure (communication)
• Fluid analysis to establish source of pressure increase
• Fluid analysis to monitor corrosive and hazardous components
• Gas volume and hydrocarbon mass evaluation
• Direct measurements of gas and liquid leak rates
• Quantify liquid influx into gas filled volumes
• Identify location of leaks and leak paths
• Potential annulus pressures vs. MAASP
• Escalation potential
6
Leak Metering System (LMS)
LMS Dim:100x65x85cm
Weight: 150 kg
Rating: 35 MPa / 200 °C
Applied for:
- Direct leak metering
- Leak properties
- Leak composition
- Toxic and corrosive
- Volume & mass
- Wireless pressure
ATEX zone 1
approved
No intervention is
required.
7
Acoustic Metering System (AMS)
• ATEX Zone 1 approved
• Battery operated
• Less than 100 kilos
Connection to well
Pressure rating: 15000 psi
Mounting: Tubing or annuli
Maximum depth: 6000 m (?)
Applied for:
- Determination of gas volumes in annulus
- Determine liqiuid influx during inflow test
- Determine anomalies in tubing or casing
- Determination of reservoir pressure
8
Trace Metering System (TMS)
WellTracer® Equipment Rating: Class I
Division 2 Groups A, B, C, D with a Type Z
purge also suitable for use in Class I Zone 2
AEx pZ IIC; Ex pZ IIC; T6 for use in
hazardous areas
Applied for:
- Determine depth of leaks in tubing or casing
- Gas lift surveillance & troubleshooting
- Determine relative size of leaks
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A A
B B
TBG
Rigup for leak test and gas lift surveillance
Activity Time required
1. Rig up on well 1 hrs
2. Measure initial gas volume 0.5 hrs
3. Gas compositional analysis 1 hrs
4. Shoot liquid level 0.5 hrs
5a. Bleed down 0.1-1 hrs
5b. Inject CO2 tracer 0.1 hrs.
6. Measure gas leak rate 0.1-1 hrs
7. Shoot liquid level 0.5 hrs
8. Pressure buildup test 1-6 hrs
9. Shoot liquid level 0.5 hrs
10. Calculate liquid leak rate 1 hrs
Sum – Time of activities 6-12 hrs
Gas-lift
CO2 inj.
10
Leak metering Gas Lift Valve (GLV)
Leak rate is measured while bleeding down.
Only a partial bleed down is required
Maximum leak rate is recorded at sonic flow
Liquid influx is detected by acoustics
Communication is spotted by wireless.
Online gas chromatography to determine
gas composition & properties.
Pressure buildup analysis.
• Reduced time
• Less stress on casing/cement
• Improved data quality
• Third party verification
• Reduced workload for onsite personnel
A A
B B
TBG
1) Initial conditions Initial pressure, depth of gas-liquid interface, gas volume, fluid density, gas composition
2) Bleed down test Plot showing pressure, temperature, flow rate and density measured during bleed down
Plot showing pressure response in tubing and all annuli used to determine communication
Total volume (mass) taken out during test
Gas volume calculation based on pressure drop and volume taken out
3) Leak rate test Plot showing pressure, density, temperature and flow rate
Measured leak rate of gas and liquid, pressure, density, temperature
4) Pressure buildup test Plot showing pressure in tubing and annuli during test
Pstart - Pfinal, Gas volume (start/final), Calculated leak rate
5) Diagnostic test Acoustic determination of leak points
Pressure and liquid level manipulation to determine depth of leaks (u-tube calculations)
TMS (WellTracer) survey to determine depth of leaks in tubing and casing
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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Sequence of measurements
Determination of liquid level and gas volume
Monitoring liquid influx
Acoustic measurements of the
gas-liquid contact is performed
during the bleed down period.
Movements in the liquid level is
used to determine liquid leak
rate.
Determination of gas leak rate
Monitoring gas influx
The LMS system monitors
the maximum gas leak rate.
Fluid properties and
composition is also
monitored by the LMS.
Determination of leak depth
Using TMS / WellTracer ®
• The depth of leaks in tubing is
determined by injecting a tracer
component into the lift gas while the
well is producing normally
• The exact depth of the leaks is
determined using downhole
reference points.
• Injection through the failed gas lift
valve in the top mandrel is wasting
37% of the lift gas resulting in a 21
bbls/day lost of oil production.
Gas lift surveillance
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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WellTracer for Surveillance and Production optimization
• Detect inefficiencies
• Monitor injection points
• Monitor lift gas rates
• Optimize well performance
• Verify gas lift design
Detecting problems at an early stage
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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Life-cycle approach
• PERSON/PATIENT
– Genes
– Brain / impulses
– Health check
– Diagnosis
– Medication
– Surgery
– Dead
• WELL
– Well construction
– Intrumentation
– PM program
– Diagnostic measurements
– Chemicals/Cleaning
– Intervention/Workover
– P & A
Detecting problems at an early stage
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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Life-cycle approach
• PERSON/PATIENT
– Genes
– Brain / impulses
– Health check
– Diagnosis
– Medication
– Surgery
– Dead
• WELL
– Well construction
– Intrumentation
– PM program
– Diagnostic measurements
– Chemicals/Cleaning
– Intervention/Workover
– P & A
LMS/AMS/TMS
Detecting problems at an early stage
Feb. 4 – 8. 2013 2013 Gas-Lift Workshop
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Importance of Preventive Maintenance routines (PM)
• PERSON/PATIENT
– Genes
– Brain / impulses
– Health check
– Diagnosis
– Medication
– Surgery
– Dead
• WELL
– Well construction
– Intrumentation
– PM program
– Diagnostic measurements
– Chemicals/Cleaning
– Intervention/Workover
– P & A Sudden death
Serious incident
Experience from GLV testing on the NCS
560 GLV’s tested in 2012.
73 GLV’s leaking outside API
criteria.
63 GLV’s successfully cleaned
(86%).
Lifetime of GLV on average
extended by almost two years,
compared to changing valve
on first leak test failure.
Production Reducing Activities (PRA)
Start PRA/PM01
Permit & SJA
Pressure test equipment Inflow test AWV
Shut in well at surface
Inflow leak test Xmas tree valves
Inflow leak test DHSV
With zero pressure above DHSV, start wellhead maintenance
Flow line inspection
Equalize pressure and reopen DHSV
Pressure up tubing
Measure liquid level in tubing
Shut down gas lift
Inflow leak test ASV valve
Inflow leak test ESD valve
Reopen ASV valve
Measure fluid level and calculate gas volume
Leak test ASCV og HASCV.
Bleed down for inflow test of GLV
Measure leak rate in GLV
Restart well.
Optimizing PRA’s
• Wellhead maintenance
• Flowline inspections
• Well integrity surveys
By synchronizing such activities
the number of planned shutdowns
can be significantly reduced,
leading to increased yearly
production
Summary
• Well Integrity & Gas lift
performance can be tested
with one simple survey.
• No intervention is required
for a standard test.
• No production shutdown is
required when performing
gas lift surveillance.
• Only a partial bleed down is
required for leak testing.
THANK YOU!
Questions?
Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 23
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Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 24
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