8/10/2019 04-Preprocessing

1/13

1987-2005 - 050118

1

Well Test Data Preprocessing

Quality Assurance

and

Quality Control

Data Preprocessing

1987-2005 - 050118

2

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

8/10/2019 04-Preprocessing

2/13

1987-2005 - 050118

3

QA/QC What ?

RESERVOIR

BEHAVIORWELLBORE

PHENOMENA

ACQUISITION

PROBLEMS

OBSERVED PRESSURE

BEHAVIORS

QA/QC

DIAGNOSIS AND SELECTION

CONTAMINATED PRESSURE

INFORMATION

1987-2005 - 050118

4

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.

8/10/2019 04-Preprocessing

3/13

1987-2005 - 050118

5

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

1987-2005 - 050118

6

QA/QC Why ?

Conventional method Modern approach

Mechanical

gauge

High acurracy

gauge

8/10/2019 04-Preprocessing

4/13

1987-2005 - 050118

7

QA/QC How ?

Lower gauge

Upper gauge

The only difference is a fluid column change

1987-2005 - 050118

8

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

8/10/2019 04-Preprocessing

5/13

1987-2005 - 050118

9

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

1987-2005 - 050118

10

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

8/10/2019 04-Preprocessing

6/13

1987-2005 - 050118

11

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.

1987-2005 - 050118

12

QA/QC : Fluid level

Differentialpressure(Pbot-P

top)

A CHANGING LIQUID LEVEL IN A WELL CAN BE SEEN ON THE DIFFERENTIAL PRESSURE

8/10/2019 04-Preprocessing

7/13

1987-2005 - 050118

13

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.

1987-2005 - 050118

14

Field Example

8/10/2019 04-Preprocessing

8/13

8/10/2019 04-Preprocessing

9/13

1987-2005 - 050118

17

Field Example

1987-2005 - 050118

18

QA/QC : Phase segregation

Flowing

dynamic gradient

PHASE SEGREGATION DURING THE BUILD UP

Upper gauge

Lower gauge

8/10/2019 04-Preprocessing

10/13

1987-2005 - 050118

19

QA/QC : Phase segregation

Static gradient

PHASE SEGREGATION DURING THE BUILD UP

Upper gauge

Lower gauge

1987-2005 - 050118

20

QA/QC : Phase segregation

PHASE SEGREGATION DURING THE BUILD UP

Upper gauge

Lower gauge

Start of phase

segregation

8/10/2019 04-Preprocessing

11/13

1987-2005 - 050118

21

QA/QC : Phase segregation

PHASE SEGREGATION DURING THE BUILD UP

Upper gauge

Lower gauge

Segregation

1987-2005 - 050118

22

QA/QC : Phase segregation

PHASE SEGREGATION DURING THE BUILD UP

Upper gauge

Lower gauge

Static gradient stable

8/10/2019 04-Preprocessing

12/13

1987-2005 - 050118

23

Field Example: Temperature

1987-2005 - 050118

24

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

8/10/2019 04-Preprocessing

13/13

1987-2005 - 050118

25

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

1987-2005 - 050118

26

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