Dunlin Field - Recovery of Stranded Oil From the Block 10 Area

DEVEX 2011

Tony Peters

Lead Petroleum Engineer , Fairfield Energy Aberdeen

Dunlin Field – Block 10

• Blk 10 Description

• 2010 Redevelopment

• Results

• Conclusions

• Forward Plans

Dunlin

Blk 10

Dunlin Main

•211/23 211/24

•160 Km NE of Shetland

•NW/SE Elongated Tilted Elongated Horst Block

•Middle Jurassic Brent Group Sandstone

•9300 - 8800 ft.tvdss

•Pi ~ 6100 psi, OWC 9125 – 9215 ft.tvdss

•36 API, 220 scf/bbl, µo ~ 1 , Psat 962 psi

•P50 STOIIP ~ 750 MMbbls

•First Oil August 1978

•Water Injection BBl in = BBl out

Block 10

•Downthrown Block to SE of Dunlin Main

•Discovered in 1983

•OWC’s 400-500 ft. deeper than main field

•35 API, 214 scf/bbl, µo ~ 1.3 cp, Psat ~ 850 psi

•P50 STOIIP ~ 70 MMbbls

•First Oil Sept 1983

•No dedicated water injection

Acquired by Fairfield Energy &

Mitsubishi Oil & Gas in Jan 2008.

Dunlin

Main

10

Dunlin Blk 10 Neighbourhood – BCU TWT

Dunlin Blk 10

Blk 10 Stratigraphy

Etive

Rannoch

Broom

Tarbert

Ness

Heather

Blk 10 Oil Recovery

Blk 10 Gross Rate

~ 50 billion bbl “Aquifer”

Watercut – Blk 10 vs. Main Field

Block 10

Da14S2

Da38

Da35

Da40S1

Block 10 Pressure vs. Brent Field*

*http://ior.senergyltd.com/issue10/articles/shell/index.htm

@ 8700 ft. tvdss

Blk 10 Remaining Reserves

Blk 10 2010 Redevelopment - Objectives

– Reappraise

• Reservoir Performance

• Well Performance

– Gather data to optimize subsequent development activities.

– Compromise where necessary to ensure successful appraise.

Blk 10 Phase 1 Redevelopment

Install ESPs in two 10 wells

–Da14S2

• Structurally elevated

• Established decline , in 1997 producing 1900 bopd & 85% Watercut

• PI 40 – 60 B/D/PSI

• 7 – 20 mblpd pump (3x 562 Series, H15500R, 46 stages CT, 3 x Motor

F130 390 HP)

–Da33S1

• Drilled post Brent depressurisation

• Intermittent producer, 400 bopd, 20% watercut

• PI 1 - 3 B/D/PSI

• 1 – 4 mblpd pump + gas handler (2x 538 Series, S6000R, 66 stages CT, 1

x Motor F152 450, 2600 V, 104A, UT per POD)

• Dual pumps POD Installation

–Topsides Module

• Space for 6 X VSD

•Compromises

–Well architecture required pumps to be set ~ 1300 ft.tvd above reservoir

–Work over operations to pump setting depths – did not perform any reservoir

cleanout.

–No down hole sand control

DA14S1 & S2 CPI

Da14S2 Performance - Rates

Da14S2 Performance - Watercut

Da14S2 Performance - Pressure

~ 1 billion bbl “Aquifer”

Produced Fluids Forecast

Blk 10 Pressure Strategy

Pressure Response to Zero PSI Water Injection

Low Pressure Water Injection Options

• Subsea Injection Well, allow North Sea Dumpflood • Low Cost Water

� Very High Injection Uptime

⁻ Hi Cost Zonal Management & Surveillance (DSV visits)

• Platform Well, Low Pressure Water Injection� Spare LP Water Injection Ullage

� Low Cost Zonal Management & Surveillance

� No Impact on HP injection Capacity

� Future Flexibility

• Blk10 2010 Development Confirmed

– Resaturation as an active reservoir mechanism.

– Producibility of the stranded Blk 10 oil with artificial lift.

– Negligible deterioration in historic well productivity due to depressurisation

– Aquifer currently not strong enough to enable recovery of full Blk 10 potential

– Low pressure water injection as suitable method for effective pressure support.

– Value potential confirmed.

Conclusions

Future plans

• Integrate new data into revised subsurface models

– Historic performance

– Depressurisation

– 2010 production

• Resaturation

• Fractional flow

• Pressure Depletion

• Well Interference

• Long Term Redevelopment Plan

– Injection Well Location & Zonal Management

– Workover / Sidetrack Da14S2

• Optimum ESP & Completion Design, incorporating any learnings from the pulled pump

– Topside modifications for long term low pressure water Injection

– Robust & Flexible

• Surveillance

– Cased Hole saturation logs (DA35, Da40S1)

• Gas lift Option

– 2011 Gas Import

Acknowledgements

2010 Dunlin Team

Matt Brettle, Doug Smith, Andrew McKenzie, Tomohiro Kakiuchi (Mitsubishi Oil &

Gas), Adam Harper, Drew McGinn, Calum Trail, Bahman Emtiazian, Manuel

Maldonaldo, Andrew O’Donovan, Sandy Fettes, Dave Bruce, Hugh Bennett, Alan

Scott…..

Questions …..

Da14S2 Flowline BSW

Block 10 Drift results – Q3 2008

Da33S1 ESP performance

Water Injection Process

Dunlin/Dunlin SW Main Field

bblin = bblout

Da14S2 Flow Restriction

• After six months, 620 MMbbls unable to lift fluids to

surface

• Moving Blockage in well

• Subsequent Camera & Sampling

– No sand

– Minor evidence of scale in tubing

– Acetic Acid, BaSO4 dissolver bullheads unable to reinstate

production

Pressure Response to Water Injection

– Material Balance

Da14S2 Performance – Aquifer Support

Brent Field Liquid rate

Blk 10 Fluid Properties

WOR Validation