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Well Test Data Preprocessing
Quality Assurance
and
Quality Control
Data Preprocessing
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QA/QC
SERVICESERVICE
COMPANYCOMPANY
MAXIMUM INFORMATION
TO BE EXTRACTED
DATA
ACQUISITION
ECONOMICAL
CONCERN
COMMERCIAL
CONCERN
COMPETITIVE AND
SATISFACTORY PRODUCT
TECHNICAL
CONCERN
QUALITY ASSURANCEQUALITY ASSURANCE
REQUIREDREQUIRED
OPERATINGOPERATING
COMPANYCOMPANY
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QA/QC What ?
RESERVOIR
BEHAVIORWELLBORE
PHENOMENA
ACQUISITION
PROBLEMS
OBSERVED PRESSURE
BEHAVIORS
QA/QC
DIAGNOSIS AND SELECTION
CONTAMINATED PRESSURE
INFORMATION
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Data acquisition path
W.T. data plots
Measured pressure data
Reservoir pressure
and production
Reservoir behavior
Pressure and rate data
Diagnostic plotsHydrostatic Delta P
and friction
Reporting
There are sources of
errors all along the
acquisition path.
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QA/QC Why ?
HIGH ACCURACY
MEASUREMENTS
UNSEEN UNTIL NOW PHENOMENA ARE TODAY
REVEALED
DIAGNOSIS BECOMES MORE DIFFICULT
SOLUTIONS ARE MULTIPLE
NEED FOR ADDITIONAL INFORMATION
SENSITIVE ANALYSIS
METHODS
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QA/QC Why ?
Conventional method Modern approach
Mechanical
gauge
High acurracy
gauge
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QA/QC How ?
Lower gauge
Upper gauge
The only difference is a fluid column change
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QA/QC : Identify problems
UNDESIRED WELLBORE
PHENOMENA
PHASE SEGREGATION
FLUID INTERFACE
MOVEMENTS
TEMPERATURE ANOMALIES
ACQUISITION AND GAUGE
PROBLEMS
GAUGE DRIFT
PRESSURE GAUGE
OUT OF SPECIFICATIONS
ELECTRONIC FAILURE
OPERATIONAL PROBLEMS
REPORTING ERROR
COMPLETION LEAK
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QA/QC : Test Design
If wellbore problems are likely to happen then
an adequate test design can avoid some or all
of the acquisit ion problems:
Downhole shut-in
Placement of pressure gauges
Procedures adapted to well and completion
The test design must
Reach the test objectives
Avoid the undesired wellbore effects
Select the best acquisition conditions
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The QA/QC procedure
Review of the data
Time synchronization
Gauge Comparison
Differential Pressure Analysis, diagnosis
Check Gauge Accuracy within specifications
Validity of Transient Analysis
Selection of the most representative data channel
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Differential Pressure Analysis
The dif ferential pressure between gauges is a direct
measure of the hydrostatic head between sensors
The pressure gradient must correspond to the
expected fluid.
Any pressure di fference must be diagnosed andexplained.
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QA/QC : Fluid level
Differentialpressure(Pbot-P
top)
A CHANGING LIQUID LEVEL IN A WELL CAN BE SEEN ON THE DIFFERENTIAL PRESSURE
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Field Example
Test Information
Well is shut in by a mechanical downhole shut-in valve set in a
completion nipple 30 m above sandface.
High accuracy quartz memory recorders are suspended in tandem
under the shut-in valve. Tool string run in on slickline.
At the end of the planned build-up, pressure equalization was made
using slickline.
During the test the well had produced sand, which had to be bailedbefore gauge recovery.
Flowing pressure was unstable due to slugging caused by long
flowlines to the gathering station.
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Field Example
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Field Example
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QA/QC : Phase segregation
Flowing
dynamic gradient
PHASE SEGREGATION DURING THE BUILD UP
Upper gauge
Lower gauge
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QA/QC : Phase segregation
Static gradient
PHASE SEGREGATION DURING THE BUILD UP
Upper gauge
Lower gauge
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QA/QC : Phase segregation
PHASE SEGREGATION DURING THE BUILD UP
Upper gauge
Lower gauge
Start of phase
segregation
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QA/QC : Phase segregation
PHASE SEGREGATION DURING THE BUILD UP
Upper gauge
Lower gauge
Segregation
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QA/QC : Phase segregation
PHASE SEGREGATION DURING THE BUILD UP
Upper gauge
Lower gauge
Static gradient stable
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Field Example: Temperature
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QA/QC Conclusion
- Identification can be made of:
- Gauge drift
- Phase segregation
- Anomalies not reported
- Gauges reported up-side-down
- Fluid phases for pressure correction
- Check of gauge manufacturers claims to accuracy and resolution
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QA/QC Conclusion
- Determined which part of the measured pressure data is due
to pure reservoir response
- Discounted the pressure behavior due to wellbore effects
- Identified the validity of Pressure Transient Analysis
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Production Optimization Using Saphir
Offtake rate relatively constant
then
Differential pressure analysis (BHP THP) indicates:
Changes in water cut
Changes in GOR
Changes in flow restrictions and skin
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