brent abandonment campaign
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Brent Abandonment Campaign P&A Technology - Section Milling Experience In Conjunction with Schlumberger
PAF Seminar - Stavanger 19th October 2016, 14:20-14:40
Martin Dow Wells Engineer - Brent Abandonment Design
1 October 2016
Brent Charlie and Cormorant Alpha – Stavanger 1978
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Agenda
Introduction to Brent Field P&A Scope and Field Isolation Strategy
Overview of Field Isolation Strategy and Section Milling Requirements
Section Milling Performance to Date
Key Performance Focuses
Section Milling – What’s Next/Alternatives
Close-Out Summary
Q&A
October 2016 2
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Brent P&A Overview – Project Scale Field Abandonment Philosophy
Introduction
1 October 2016 3
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Brent P&A Campaign Scale and Challenges
October 2016 4
154 well slots -141 wells to abandon with 240 sidetracks to consider
4 Platforms (Brent Delta awaiting topside removal)
Currently executing operations on Brent Bravo - Alpha P&A start-up Q3 2016 and Charlie Q1 2017
Completed P&A on 73 wells
Variation of well architecture, well design, current integrity and usage
Previous abandonments of sidetracks and motherbore
Condition of 40yr old wellbore components
Historical data quality
No one fits all solution, each well requires tailored approach
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Revised Brent P&A Philosophy - Section Milling Requirements
October 2016 5
Recent revised Field isolation strategy post OGUK guideline revision
Challenge made possible through in-depth monitoring study of
annuli pressures and zones with flow potential
Saving ~6,000ft total of shallow section milled windows
Potential for 2 milled windows per well
Up to 200ft window required depending on existing annular
isolation
Routinely mill 100ft windows with up to 150ft milled in a single trip
10 wells with dual section milling/dual casing isolations required
Currently executing first PWC operation/trial to reduce exposure
over dual isolation wells
Continual drive to improve milling performance through equipment
optimisations, personnel competency, swarf handling, procedures etc.
FormationTop
D C B A A B C D
Sea
Bottom
Utsira Shale 4Utsira Sst 3
Utsira Shale 3Utsira Sst 2
Utsira Shale 1
As-is
Top Reservoir
Kimmeridge Clay
Shetland
Maureen Fmn
Lista Fmn
Utsira Shale 2
Utsira Sst 4
Shetland Plug 800ft
Horda Plug 800ft
Utsira Plug 800ft
Balder Fmn
Horda Fmn(Shale)
Horda FmnFrigg Sst
Lark Fmn Skade Sst
Utsira Sst 1
FormationTop
D C C D
Sea
Bottom
Utsira Shale 4Utsira Sst 3
Utsira Shale 3Utsira Sst 2
Utsira Shale 1
Balder Abandonment / Final Status
ISW
Utsira Sst 4
Utsira Shale 2
Utsira Sst 1
Lark Fmn Skade Sst
Horda FmnFrigg Sst
Horda Fmn(Shale) Horda Plug 800ft
Balder Fmn
ISW / Milling FluidLista Fmn
Maureen Fmn
Shetland
Shetland Plug 800ft
Top Reservoir
Kimmeridge Clay
ISW
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Beginning of Campaign vs Now Where Have we Made Improvements
Section Milling to Date
2 October 2016 6
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Bridge Plug on Mill 1.5days
Enhanced Knife Design
0.5days
Operator Competence
and Procedures
0.5days
Improved Swarf
Handling 0.5day
Optimised Fluid
Strategy 1day
Combined Mill and
Underreamer 1.5days
Combined Cement Plugs
2days
Section Milling Performance / Barrier Execution to Date
October 2016 7
Time to mill window and set abandonment cement plugs dramatically reduced from beginning of Brent P&A
campaign
From casing cut to tag of cement plugs 12days 2011 to <4.5days 2016
How Were These Improvements Realised?
*Based on deep milled window (reservoir isolation barriers)
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Evolution & Optimisation of Remediation BHA Knife Technology – Insert Shape, Material, Cutting Characteristics Fluids & Swarf Handling Operator Competence & Consistency
Performance Improvements
3 October 2016 8
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Separate Section Mill and
Underreamer
1 Trip Saved
Combined Section Mill/Underreamer
1 Trip Saved
Bridge Plug Run on SM/UR Assembly
Evolution & Optimisation of Remediation BHA
October 2016 9
Trip saving technology cut 3 round trips to a single trip remediation system
Have driven continuous performance with Schlumberger throughout campaign,
successfully introducing world first technologies into the P&A environment
Optimised BHA design for best milling parameters
Using collars in place of HWDP to increase stability and string inertia
Slick as possible BHA to mitigate swarf pack-offs
Inherent risk to milling performance where poor or no annulus seal exists
Mill life severely degraded, poor swarf characteristics, hole cleaning etc.
No solution to excessive casing movement – SM not prime option
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Knife Technology – Insert Shape, Material, Cutting Characteristics
October 2016 10
Improved consistency in manufacturing and brazing process
Optimised fluid properties for enhanced swarf recovery
Titanium coating applied to knives
Completed trials of new knives with revised cutting structure
Achieved ROP of 4.5ft/hr vs existing target of 3ft/hr
Knives only 20-35% worn over 150ft window – Original window was planned to be 200ft with confidence this
could be achieved in a single trip
Improved consistency of swarf characteristics throughout window – Small Chips vs Long Coils
22ft Milled – Delaminated Cutting Structure 36ft Milled – Deviated Wear Profile 96ft Milled – Even Wear Profile 150ft Milled – 20-35% Worn
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Fluids & Swarf Handling
October 2016 11
Basic generic milling fluids system – viscous/weighted sea water based milling fluid
Optimised for easy bulk building, maintenance, environmental impact and cost
No inhibitor added to mitigate formation/shale collapse
Field specific offset data and learnings important to fluid design
For swarf recovery alone viscous water enough - trade off with formation stability
High performance fluid system considered, but cost vs reward not advantageous
Milling performance/ROP restricted by surface swarf handling capacity
Also important to consider deck space footprint, deck loading, flowline position,
campaign length, additional POB, compatibility with existing drilling package/fluid
systems and position of secondary recovery magnets.
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Operator Competence & Consistency
October 2016 12
Fishing & Remedial crew consistency has been critical to maintaining
milling performance throughout campaign
Drill crew personnel stability also key to sustaining performance and
driving continual improvements
Swarf Unit operator in constant communication with drill floor relaying
trends in swarf return and signs of pack-offs, fluid spillages, mill
performance etc.
Further Optimisation Opportunities:
Crew multiskilling to reduce exposure to high service company
demand and POB restraints
Surface pack-off monitoring system
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What’s Next for Section Milling & Alternative Methods Summary Q&A
Section Milling Alternatives and Close-Out
4 October 2016 13
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What’s Next for Section Milling and Alternatives
October 2016 14
Further trials planned using alternative knife design/insert material
Additional trials with DSM assemblies in collaboration with various service companies
Alternative Methods
Focus now on improving and verifying alternative, more efficient and cost effective isolation
methods to lessen reliance on section milling:
Through tubing cementing
Perf & test/verify – How much is enough? Challenging need for remediation.
Perf & wash cement – How to ensure right first time approach…
Dual string logging
Thermite plugs
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Close - Out Summary
October 2016 15
Trip saving technology dramatically reduced barrier execution time,
target times increasingly more aggressive
Refreshed, performance focused approach to Brent P&A campaign
Personnel competency drives bottom-line performance. Standard
operation carried out multiple times every month keeps focus and enables
continuous improvement
New contractual incentives designed to drive technology improvements
Enhanced focus on alternative techniques and verification of isolation
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Questions and Answers
October 2016 16
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