Zonal Isolation: Well Barriers and Assurance on

BP’s North Sea Region Well Abandonments

Alexander Borresen and Tom Gillibrand April 2013

Contents

• Overview

• Magnus F4z History

• Well Overview

• Well Suspension

• Verification prior to Subsea Xmas Tree (SSXT) removal

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• Verification prior to Subsea Xmas Tree (SSXT) removal

• Permanent Abandonment and Assurance of Well Barriers

• Delivering Safe and Reliable Abandonments

• Questions

Overview

• Focus on reduction of wellstock

− Dedicated cross-functional Decommissioning team

− Three consecutive subsea abandonments performed

– Magnus F4z the final one of these

− Programme of abandonment work planned every

year for next five years

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year for next five years

• Working to OGUK guidelines and internal standards

− Use of well barrier concept

− Additional assurance around Pore Pressure

Fracture Gradient (PPFG) and Permeable Zones

3

Magnus F4z History

• Average injection was approximately 4,000bpd

into the Lower Kimmeridge and approximately

12,000bpd into the Magnus Sands

• Well had been shut in due to trawler damage

• Light Well Intervention Vessel mobilised prior to

rig arrival to confirm access and de-risk rig

workscope

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workscope

• The outcome was to obtain estimated closed-in

tubing hanger pressures for production &

annulus bores, well access and integrity

information

Well Overview

• Completed in 1997

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• Dual water injector

• Max inclination ~55deg

Well Suspension

• Stable fluid column – Fibrous LCM and

overbalanced fluid

• Cement plug set on coil – Critical slurry

design and tubing punch

• Cement length impact on remainder of

abandonment

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abandonment

• Mill internally to verify

• Positive pressure test tubing and

annulus independently and Inflow test

with MEG/SW

6

Permanent Abandonment Zones 1 & 2

• Isolation Scanner (USIS/CBL) – Confirming sufficient good

cement for well barrier elements (WBEs)

• Bridge plug ran on cement stinger – Efficiently minimise

slumping

• 2 7/8” stinger XO to 3 ½” pipe – Optimise cement job

• Three consecutive 400m cement plugs set in brine – Density

and volume control critical

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and volume control critical

• Circulate at TOC – good cement returns and defined base

for next plug

Assurance – Ensuring Success

• Cement in excess of that required

• Assurance of job parameters

• RIH with tagging assembly and drill off hard cement

− Experience shows tag not always reliable

− Minimum 5m with ~10 klbs WOB

− Weight Test

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− Weight Test

• Pressure test – surface pressure using worst case fluid

throughout well – i.e. mix water gradient through cement

Permanent Abandonment Zone 3

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• Pulled ~1300m 9 5/8” casing to confirm good cement

• Difficulty pulling casing – 15 sections due to gelled mud and solids

• USIT/CBL – Verify annular cement

• Bridge plug ran on cement stinger – Base verified with tag and pressure test

• Verified cement by drilling and weight test

Permanent Abandonment Zone 4

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• Cement to surface on primary job

• Drilled off cement, positively pressure tested and inflow tested at wellhead

• Wellhead remains in-situ – Optimise recovery with campaign

Delivering Safe and Reliable Abandonments

• Technical limit performance gains from “Abandonment rig”

• Summer only philosophy

• Clear internal requirements for cementing

• Novel approaches – i.e. Consecutive cement plugs

• New technology – e.g. Modified BOP test tool

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• New technology – e.g. Modified BOP test tool

Questions

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