1. Gaslift Management in PDO Northern Directorate
By Adi Al Naamani
Harith Al Naabi 1

2. Gaslift Management in PDO Agenda
Introduction
Designs, Improvements, Opportunities and challenges
Gaslift management and processes
Automatic Validation Tester (AVT) and Wireless gaslift trial
Overview per area and examples
Conclusion 2

3. Location IRAQ IRAN Turkey Libya Saudi Arabia Sudan 3
Country size 312,000 km2
Population 2.3 million
Accelerated development
75 % income depends on hydrocarbon
Turkey
Libya
Saudi
Arabia
Eygpt
Sudan 3

4. People 4

5. People 5

6. Beaches & Wadis 6

7. Petroleum Development Oman
MUSCAT
Sur
Sohar
Salalah
ARABIAN SEA
GULF OF OMAN
100 km
PDO (since ‘66) is a JV between
60 % Government of Oman
34 % Shell
4 % TotalFina
2 % Partex
Shell is technical advisor
Production 700 kb/d (90% of Oman’s
Oil production)
66 producing stations
117 oil producing fields
Over 3000 active wells
620 gaslift strings. 28% of production, ,000 bbl/d
85% of gaslift production from North
Majority of fields under water flood N S 7

8. Gaslift wells in the Northern Directorate
The North of PDO has primarily carbonate reservoirs with depths varying from as shallow as 800m to 2700m deep.
Now there are approximately 500 Gaslift wells constituting 50% of the oil producers.
In the North, Gaslift wells produce 45% of the oil and 42% of the gross. 8

9. Design
Design in most wells has 2 to 5 mandrels, depending on well depth and expected deepest operating point
IPO valves are run in >95% of the wells
Mostly unloading valve sizes are the same as the orifice valve size.
Redesigns are done where well behaviour becomes too unstable, parameters change 9

10. Operating @ mandrel 2 (through unloading valve)
Initial Performance
mandrel 2 (through unloading valve)
Future Performance after on-stream of Water Injector
mandrel 3 (through unloading valve)
Later Performance
mandrel 4 10

11. Optimisation and Challenges
Well by Well
Unstable wells
Leaking valves or tubing
Well integrity (e.g. leaking casing)
Possibility to lift deeper
Scale clean outs
Group optimisation
Surface controlled gaslift rates through SCADA / DCS
Set-points based on optimal distribution of liftgas using WinGLUE
Deferment reduction through re-distribution of liftgas 11

12. Optimisation and Challenges
Challenges w.r.t. optimal distribution of liftgas
Measurements (especially gas) are of insufficient quality. Flowing surveys are therefore essential
Well integrity problems has Impact on well models
Continuous changes in the reservoir pressure, PI, water cut etc.
The dynamics of reservoir not captured in well models.
Young & bright, but in-experienced production engineers.
Solutions
Dedicated production engineers on well integrity
Surveillance engineers responsible for only wells in total
Intensive training and bringing in coaches 12

13. Process Dedicated gaslift process
Monitor and trouble shoot using SCADA and test data
Understand the problem and correct
Further investigation
Analyse results of investigation
Determine improvement potential, costs and justify activity.
Design new gaslift string and schedule activity
Set valves, test valves before running & test retrieved valves with AVT tester and feedback
Kick off the well and evaluate the results
Review and file report 13

14. PDO Gaslift Management Set-up
Control
Metering
Reservoir Data
Well Data
Production Data
Tubing pressure
Casing pressure
SCADA
SGAS-CAO
Direct monitoring
& Control of
Individual Wells
DCS
Controls
Gaslift rates
to the wells
WinGLUE
Gaslift optimisation
Software 14

15. Process Improvements WinGLUE gaslift QC database set up
Automated links
Central storage of gaslift analyses
Most wells available in the SCADA system (RTAP / SOFS or the latest PC based FIELDWARE).
AVT tester is used for QC valves before running and recently pulled valves 15

16. Decker’s Automatic Validation Tester (AVT )
Implemented in the well services workshop
TROP, stem travel, R ratio etc.
Rejected at agreed tolerances, e.g. TROP difference < 15 PSI
>25% of the valves were rejected on TROP.
Visible improvements
Testing of pulled valves just started. >60% fail on leaking bellows.
Keep track of a “problem log” to increase understanding
Network connection is essential
Staff in the well services more conscious 16

17. Specific Overview per Area Area A
Constrained due to flaring restriction (no compressor ullage)
Workshop was organised
Deliverables of the workshop:
Coaching / training
Saving of 3.6 million scf/d of liftgas
Well integrity problems found and repaired
Detailed gaslift surveillance was carried out and many wells were stabilised
Many gaslift measurements wrong and corrected
For 2003 the estimated impact on production is approximately around 1200 bbl/d.
17 L

18. Specific Overview per Area Area B
In Area B, test data quality is an issue
Some wells were found quit
Some wells found with scale obstruction. Cleaned out and restored.
Total increase in the Area B was 600 bbl/d or 10% of the total gaslift production. 3% 2002 & 2003 year average impact.
18 Q

19. Example of importance of F/S
Well was tested bbl/d net oil, low BSW through 3 1/2”
200 bbl/d gain from switching on gaslift
Theoretical pressures
Tubing upsize was expected to double production
Flowing survey could only be matched with 1200 bbl/d and tubing upsize was canceled
Actual pressures 19

20. Specific Overview per Area Area C
Area C consists of two large fields
Field N has mostly natural producers.
Flow limited by Gas Oil Gravity Drainage (GOGD)
N compressors are full. Cutting back liftgas investigated.
Field C is partly water-flood and partly GOGD
Workshop held. Opportunities found:
Reduce liftgas consumption to free up compressor space (cutting back lift-gas, running velocity strings, 3 1/2” to 2 7/8” tubing)
Some wells without RTU’s
20 F

21. Wireless Gaslift Valves Trial Area C
Wireless gaslift valves (2) were installed in a well in Field C in 2002.
Communication through a modem with PC in CCR and Main Office
Down-hole pressures and temperatures displayed
Full control from the desktop was achieved
Live optimisation
Modem on bottom valve broke down, but still operating.
Confirmed bad batch of modems (50%)
21 F

22. Wireless Gaslift Valves Trial Area C
Business case for large scale implementation being made, but
times higher costs than conventional gaslift
Even with one third of costs, large scale implementation means 16,000 bbl/d extra production is required or 8% of production.
Most promising to replace PPO valves & IPO running it as part of new well or existing well work-overs.
22 F

23. Specific Overview per Area Area D
Advanced automation; surface control valves linked to the DCS & SCADA. Full control and optimisation.
Main challenge is well integrity and continuously changing well performance.
Additional people have been put on the job in Area D (surveillance engineers). They complement the work of the other production engineers.
Coaches brought in
23 Y

24. Specific Overview per Area Area D - Well Examples
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
25-Apr
Tubing Pressure
Casing Pressure
Surging pressure
before Optimisation
100
200
300
400
500
600
700
Mar-03
Apr-03
May-03
Gross m3/d
Net m3/d
Gas Lift x 100 m3/d
1000
2000
3000
4000
5000
6000
28-May
Tubing Pressure
Casing Pressure
Maintain Production
with 50% less Liftgas
Stable operation
after Optimisation
24Y

25. Specific Overview per Area Area D - Well Examples
Surging pressure
1000
2000
3000
4000
5000
6000
7000
22-Sep
Tubing Pressure
Casing Pressure
before Optimisation 50
100
150
200
250
300
350
400
450
500
Jan-03
Feb-03
Mar-03
Apr-03
Gross m3/d
Net m3/d
Gas Lift x 100 m3/d
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
28-May
Tubing Pressure
Casing Pressure
Production increase
of 350%.
Stable operation
after Optimisation
25 Y

26. Conclusion Reduction in Liftgas usage (~36 mln scf/d)
Cost savings on Gaslift compressor requirements.
Enabled production of high GOR wells
Create compressor capacity to handle new oil producers.
Stabilising wells, Reduce flaring
In some cases lifting deeper
Sum of the measurable initial production increases after activities in 2003 is around 4500 bbl/d (2% of total North) Year average value is 0.7%. 26

27. What is happening next …..?
Further enhance staff competence and skills
Complete implementation of the AVT tester
Trial new technology such as Bubble breaker, Bubble gaslift and surface controlled gaslift valves
Bringing in a dedicated production engineer for gaslift
Continue with the efforts, because it pays back. 27