Gaslift Management in PDO Northern Directorate By Walrick van Zandvoord

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

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

People

People

Beaches & Wadis

PDO (since ‘66) is a JV between 60 % Government of Oman 34 % Shell 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, 200,000 bbl/d 85% of gaslift production from North Majority of fields under water flood

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.

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

Operating @ mandrel 2 (through unloading valve) 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

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.

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

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

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

PDO Gaslift Management Set-up

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

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

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

Specific Overview per Area Area 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.

Specific Overview per Area Area 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.

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

Specific Overview per Area Area 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

Area F Wireless 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%)

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

Specific Overview per Area Area 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

Specific Overview per Area Area Y - Well Examples

Specific Overview per Area Area Y - Well Examples

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%.

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.