Gaslift Management in PDO Northern Directorate

1. Gaslift Management in PDONorthern Directorate By Walrick van Zandvoord

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

3. Location • Country size similar to Kansas • Population 2.5 million • Accelerated development • 75 % income depends on hydrocarbon

4. People

5. People

6. Beaches & Wadis

7. GULF OF OMAN Sohar MUSCAT Sur ARABIAN SEA 100 km Salalah • 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, 200,000 bbl/d • 85% of gaslift production from North • Majority of fields under water flood

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.

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 operating valve size to allow the operating point to be the orifice or unloading valve. • Redesigns are done where well behaviour becomes too unstable

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

11. Optimisation and Challenges • Well by Well • Unstable wells • Leaking valves or tubing • Well integrity (e.g. liftgas injected in shallow aquifers) • 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 • Tables are created for different compressor availabilities for optimal distribution.

12. Optimisation and Challenges • Group optimisation - Continued • Optimally distribute • Minimise deferment when compressors are down • Challenges • Gas measurements are of insufficient quality. Flowing surveys are therefore essential • Well integrity problems are experienced in some areas, e.g. tubing leaks, mandrel leaks, casing leaks

13. Optimisation and Challenges • Challenges - Continued • Long integrity repair jobs • 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 50 - 70 wells in total • Intensive training and bringing in coaches

14. 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, check valves with AVT tester, test old valves and feedback • Kick off the well and evaluate the results • Review and file report

15. PDO Gaslift Management Set-up

16. 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 also pulled valves

17. 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

18. Decker’s Automatic Validation Tester (AVT ) • 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

19. Specific Overview per AreaArea L • 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.

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

21. well 110 Well was tested at 2000 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 800 bbl/d less and tubing upsize was canceled Actual pressures

22. Specific Overview per AreaArea F • Area F 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 looked at. • Field F 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) • Many wells without RTU’s

23. Area FWireless Gaslift Valves Trial • Wireless gaslift valves (2) were installed in a well in Field F 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%)

24. Area F Wireless Gaslift Valves Trial • Business case for large scale implementation being made, but • 15 - 20 times higher costs than conventional gaslift • Even with one third of costs, large scale implementation means 12,000,000 bbl or 16,000 bbl/d extra production is required or 8% of production. • Most promising to replace PPO valves

25. Specific Overview per AreaArea Y • Advanced automation; Gaslift 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 Y (surveillance engineers). They complement the work of the other production engineers. • Coaches brought in

26. Specific Overview per AreaArea Y - Well Examples

27. Specific Overview per AreaArea Y - Well Examples

28. Benefits • Reduction in Liftgas usage (~2.5 mln m3/d) • Cost savings on Gaslift compressor requirements. • Enabled production of high GOR wells • Create compressor capacity to handle new oil producers. • Stabilising wells • 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) with. Year average value is 0.7%.

29. 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.