Walrick van Zandvoord PDO 2003 Fall Gaslift workshop Kuala Lumpur - 21 & 22 October 2003 Petroleum...

Walrick van Zandvoord PDO2003 Fall Gaslift workshop Kuala Lumpur - 21 & 22 October 2003

Petroleum Development Oman

Gaslift Management in PDO

Gaslift Management in PDONorthern Directorate

By Walrick van Zandvoord




• Introduction• Designs, Improvements, Opportunities and challenges• Gaslift management and processes• Automatic Validation Tester (AVT) and Wireless gaslift

trial• Overview per area and examples• Conclusion

Gaslift Management in PDO Agenda




Location

• Country size similar to Kansas

• Population 2.5 million

• Accelerated development

• 75 % income depends on hydrocarbon




People




People




Beaches & Wadis




MUSCAT

Sur

Sohar

Salalah

ARABIAN SEA

GULF OF OMAN

100 km

• PDO (since ‘66) is a JV between60 % Government of Oman34 % Shell4 % TotalFina2 % 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




Initial Performance

Operating @ mandrel 2 (through

unloading valve)

Later Performance

Operating @ mandrel 4

Future Performance

after on-stream of Water Injector

Operating @ mandrel 3 (through

unloading valve)




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.




• 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





• 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




Gaslift Control

Gaslift Metering

ReservoirData

Well Data

ProductionData

Tubingpressure

Casingpressure

SCADA

WinGLUEGaslift optimisation

Software

SGAS-CAODirect monitoring

& Control of Individual Wells

DCSControls Gaslift rates to the wells

PDO Gaslift Management Set-up




• 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

Process Improvements




• 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

Decker’s Automatic Validation Tester (AVT )




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.




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.




Well was tested at 2000 bbl/d net oil, low BSW

through 3 1/2”

Tubing upsize was expected to double production

Flowing survey could only be matched with 800 bbl/d less and tubing upsize was canceled

Theoretical pressures

Actual pressures

well 110

200 bbl/d gain from switching on gaslift




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




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%)




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 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




Specific Overview per AreaArea Y - Well Examples

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

25-Apr 25-Apr 25-Apr 25-Apr 25-Apr 25-Apr 25-Apr

Tubing Pressure Casing Pressure




0

1000

2000

3000

4000

5000

6000

7000

22-Sep 22-Sep 22-Sep 22-Sep 22-Sep 22-Sep 22-Sep 22-Sep

Tubing Pressure Casing Pressure

Specific Overview per AreaArea 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.

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Walrick van Zandvoord PDO 2003 Fall Gaslift workshop Kuala Lumpur - 21 & 22 October 2003 Petroleum...

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