Zonal Isolation: Well Barriers and Assurance on BP’s North ... Borresen BP.pdf · Magnus F4z...
Transcript of Zonal Isolation: Well Barriers and Assurance on BP’s North ... Borresen BP.pdf · Magnus F4z...
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Zonal Isolation: Well Barriers and Assurance on
BP’s North Sea Region Well Abandonments
Alexander Borresen and Tom Gillibrand April 2013
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Contents
• Overview
• Magnus F4z History
• Well Overview
• Well Suspension
• Verification prior to Subsea Xmas Tree (SSXT) removal
BP Confidential
• Verification prior to Subsea Xmas Tree (SSXT) removal
• Permanent Abandonment and Assurance of Well Barriers
• Delivering Safe and Reliable Abandonments
• Questions
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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
BP Confidential
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
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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
BP Confidential
workscope
• The outcome was to obtain estimated closed-in
tubing hanger pressures for production &
annulus bores, well access and integrity
information
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Well Overview
• Completed in 1997
BP Confidential 5
• Dual water injector
• Max inclination ~55deg
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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
BP Confidential
abandonment
• Mill internally to verify
• Positive pressure test tubing and
annulus independently and Inflow test
with MEG/SW
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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
BP Confidential 7
and volume control critical
• Circulate at TOC – good cement returns and defined base
for next plug
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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
BP Confidential 8
− Weight Test
• Pressure test – surface pressure using worst case fluid
throughout well – i.e. mix water gradient through cement
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Permanent Abandonment Zone 3
BP Confidential 9
• 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
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Permanent Abandonment Zone 4
BP Confidential
• 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
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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
BP Confidential
• New technology – e.g. Modified BOP test tool
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Questions
BP Confidential