Subsea P&A: A step change in rig site hazard exposure ... · up subsea test tree Days removed ~ 2...
Transcript of Subsea P&A: A step change in rig site hazard exposure ... · up subsea test tree Days removed ~ 2...
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Subsea P&A:
A step change in rig site hazard exposure through risk-
based design and execution
Lynda Nwike
Wells Subsea Design EngineerShell UK
1October 2017
Shell
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Definitions and Cautionary Note
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Agenda
• Overview of A&C wells
• The Risk Based Approach to Design
• Scope removal & Optimisation from 2016 Base Case
• A&C Planning and Execution Improvements
• 2016 Plan vs 2017 Execution
• Total HSE exposure reduction & Execution times
• The bigger picture. What next?
• Q&A
October 2017 3Copyright of Shell UK Limited
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Atlantic and Cromarty Field Overview
▪ 3x suspended subsea production gas wells in the
Central North Sea.
▪ Project in partnership with Hess.
▪ Cameron STM -15 wellheads and horizontal trees.
▪ Horizontal trees – all operations conducted with tree
in place.
▪ Water depth ~380ft
October 2017 5Copyright of Shell UK Limited
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Atlantic and Cromarty project timeline
6October 2017
2005-06• Wells drilled with Global Santa Fe 140
2010• Cessation of production for the A&C wells
2014
• Well Enhancer LWIV used to plug and lubricate all wells.
• Well content bullheaded into reservoir
• 2 x bridge plugs installed in well
• 2 x crown plugs set in SXT
2017
• Rig move survey March
• Atlantic and Cromarty PDHG Pressure check on Goldeneye April to confirm P&L plugs still holding.
• Well abandonment completed July-Aug with Ocean Patriot rig
• Subsea tree and wellhead severance planned for October
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Subsurface overview
• All wells have sidetracks in the Chalk which is predominantly
without flow potential.
• All side-tracks deemed as fully abandoned.
7
Reservoir: One NPNT hydrocarbon reservoir: Captain
Sandstone. Sub hydrostatic reservoir. Max recharge pressure
would be to a hydrostatic gradient.
Reservoir seals: Rodby and Carrack formations are the original
reservoir seal. Signs of instability when the well was drilled.
Formations would provide an additional annular seal to lateral
isolations in chalk.
Tertiary group: Water bearing sands right above the Chalk
group. No indications of abnormal pressures.
Chalks: The chalk group forms the external element for the
reservoir lateral isolation.
Shell October 2017 8
Well Status BeforeWell P&L’d with LWIV
2x plugs set:1x in liner
1x in tailpipe
Tubing cut
Hold open sleeve set
2x crown plugs set:1x in internal tree cap
1x in tubing hanger
Well Status
AfterWell P&A’d with Rig
1x barrier set:• 1x combined PWC
plug to isolate
captain reservoir set
across the Chalks
1x environmental plug:• 1x plug to cap OBM
using Perforate
Circulate Cement
technique
630pptf
OB
M
510pptf
WB
M
HSXT (no guideposts) HSXT (no guideposts)
510pptf
WB
M
Environmental plug
Combined
abandonment
barrier
Top Chalk Gp
Herring
Black Band Bed
Hidra
Rodby
Carrack
🔴 Captain
Sea
Undifferentiated
Tertiary
Lower Mackerel
Upper Mackerel
Top Chalk Gp
Herring
Black Band Bed
Hidra
Rodby
Carrack
🔴 Captain
Sea
Undifferentiated
Tertiary
Lower Mackerel
Upper Mackerel
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Shell October 2017 10
Brent/ Subsea Experience
Competitive Scoping
Strong collaboration
between Wells and subsurface teams
Experience & lessons learnt from
other Operators
Holistic Ways of Thinking
Risk Based
Approach Cost Reduction
Lower HSE Exposure
Removal of unnecessary
scope
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Shell October 2017 12
84 total
46 total
38
11
21 days WOW/NPT
11 days WOW/NPT 4 days WOW/NPT
0
10
20
30
40
50
60
70
80
90
2016 Plan Planning Optimisations 2017 Plan Execution Optimisations 2017 Delivered
Da
ys
Time
A&C Planning & Execution Improvements
35 total
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Shell October 2017 13
• Subsea Tree tied back to Goldeneye platform.
• Pressure gauge deep in well allowed pressure monitoring capability.
• Allowed well pressure to be measured and confirm deep set barrier integrity.
• Removed risk of having to rig up pressure containing intervention equipment
(Subsea Test Tree etc.)
• Pulled completion with crown plugs and barriers in place.
• Removed requirement to rig up e-line to pull crown plugs and install isolation
sleeve.
Removed requirement to pull crown plugs from wellhead and rig
up subsea test tree
Days removed ~ 2 days
Risks removed :
❖ Multiple lifts
❖ Working at height
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Isolating the Captain Reservoir
October 2017 14
• PWC performed on all 3x wells.
• First deployment of PWC method on a subsea well for Shell UK.
• Hydrawell provided PWC service.
• Use single trip method on A1Y and A2Z wells.
• 2 trip solution required for C6Z due to lack of gun sump space to leave
guns below cement base.
• Did not displace excess cement from 800ft above base of
cement, final cement plug length ~1400ft. Reduced slops handling at
surface
Days removed ~ 5 days
Risks removed :
❖ Multiple lifts
❖ Swarf handling
❖ Swarf damage to equipment
❖ Swarf disposal
0
1
2
3
4
5
6
A1Y PWC
(actual)
A2Z PWC
(actual)
C6Z PWC
(actual)
Actual
Section mill
+ cement
Annulus remediation
timings (days)
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Hydrawell’s Hydrahemera tool
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Environmental Barrier
October 2017 15
• Previous subsea wells used perforating guns, sized to perforate only one or
two casing strings with mixed success.
• A&C did not need to remediate 13-3/8” annulus.
• No requirement to cap water based mud in C-annulus.
• This will be exposed to sea during wellhead recovery operations this year.
• Utilised Gator tool from Lee Energy systems.
• GATOR tool enabled large flow areas.
• No explosives were required shallow in the well.
0
1
2
3
Cut & Pull PCC with
Perf guns
A2z PCC
with Gator
Environmental Plug Clean
Times
Days
510pptf
WB
M
HSXT (no guideposts)
510pptf
WB
M
HSXT (no guideposts)
Days removed ~2 days
Risks removed :
❖ Multiple heavy lifts on deck
❖ Casing handling and transportation
❖ Rigging up & down of casing handling
equipment
PCC Strategy Cut and pull strategy
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Wellhead and Subsea Tree Recovery
October 2017 16
• Wellhead severance and recovery: Rig based Vessel based.
• Subsea Xmas tree recovery: Rig based Vessel based.
• Unlocked Xmas tree from wellhead and locked dogs prior to
setting on wellhead for recovery later in year.
• Removes risk of handling tree/wellhead on rig – deck
constraints, rig ergonomics.
Days removed ~ 4.5 days
Risks removed :
❖ No handling of trees or wellheads
in moonpool area.
❖ Heavy Lift to supply vessel from rig
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Plan vs Execution
2016 Base Plan
• Recover ~7000ft of completion
• Perform USIT/CBL log (A1 only)
• Set CH cement plug (Section mill & set OH plug on A2z
& C6)
• If unsuccessful, section mill 150ft window and set
plug
• Cut & pull production casing from ~2000ft
• Cut and pull intermediate casing from ~2000ft
• Set 500ft cement plug
• Cut and retrieve 20” and 30” string with MOST tool
• Pull and retrieve Wellhead
• Conduct seabed clearance scan
Total Days = 84.0days
October 2017 17
2017 Execution
• Recover ~7000ft of completion
• Perform USIT/CBL log (A1 only)
• Perforate 250ft of 9 ⅝” casing
• Wash perforated interval to remove solids and set
combined barrier cement plug across perforated
interval and in wellbore
• Perforate, circulate and cement B-annulus to isolate
OBM
• Wellhead and tree recovery to be performed on
separate campaign (~1.5days/well)
Total Rig days = 34.6days
Total Days (inc. vessel) = 39.1days
Days removed ~45days
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A&C Comparative Time Review
18October 2017
0
2
4
6
8
10
12
14
16
18
20
Atlantic A1Y Atlantic A2Z Cromarty C6Z
Da
ys
Well
WOW
NPT
Clean time
Benefits of scope reduction:
• 45 days ahead of 2016 plan equates to >57,000hrs of
HSE exposure eliminated (106 POB average).
• PWC method eliminated handling of swarf in surface
circulation system and reduced deck congestion.
• Perf, circulate and cement method eliminated
handling of 48 joints of 9 ⅝” casing at surface,
shipment back onshore and disposal.
• Blending cement and expanding additive onshore
eliminated requirement for cement batch tank rig up
on the rig.
• SXT and wellheads to be recovered with vessel, no
heavy lifts from rig to supply vessel required.
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Shell October 2017 21
LESS…
Wo
rkin
g a
t he
igh
t
CO2 emissions
Ca
sing
ha
nd
ling
Exposure Things
Exp
osu
re t
o w
ea
the
r
Logistics
Slops handling
Heavy Lifts
Manual
Handling
Slips Trips
Falls
Sw
arf
Ha
zard
s
to go wrong
NPTWOW
……
……
……
……
……
…
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FOUR HIGH EXPOSURE AREAS FOR THE FUTURE
October 2017 22
• Anchor handling
• Heavy Drilling BOPs
• Elimination of divers
• Wellhead Severance
• Necessity to understand stakeholders interests.
• Need to challenge industry norms and review the benefits vs the risks.
• Understand our wells.
• High costs vs minimal risk reduction.
• What role does new technology play?
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