MAKING DECOMMISSIONING HAPPEN. · decommissioning services platform well abandonment – rigless, rig-based or combined ‘simops’ 08 09 platform well abandonment - rigless, rig-based

DUBAI

ClaxtonPO Box 262490Jebel Ali Free ZoneGate 5, South SideFZS1 AL05 Dubai

T: +971 4 8863540E: [email protected]

NORWAY

Claxtonc/o Finnestadgeilen 11, Building 18Dusavik Base, N - 4029StavangerNorway

T: +47 51 83 66 74E: [email protected]

SINGAPORE

Claxton 107 Tuas South Avenue 8Offshore Marine Center637036 Singapore

T: +65 6705 5825 E: [email protected]

Learn more at:www.claxtonengineering.com Tel: +44 (0)1493 744500

UK HEAD OFFICE

ClaxtonBureside HouseNorth River RoadGreat YarmouthNorfolk, NR30 1TEUK

T: +44 (0) 1493 744500E: [email protected]

ABERDEEN

ClaxtonTern Place House, Tern PlaceBridge of DonAberdeenScotlandAB23 8JX


MAKINGDECOMMISSIONINGHAPPEN.Proven experience combined with world-class designand project delivery mean you can trust Claxton tomake your offshore decommissioning happen.

www.claxtonengineering.com@ClaxtonNews Claxton Engineering

CONTENTS

DECOMMISSIONING SERVICES 04

Platform well abandonment 08

Subsea well abandonment 10

Casing recovery 12

PRODUCTS

SABRE™- Subsea Abrasive Cutting 14

SWAT™- Suspended WellAbandonment Tool 16

Drilling and Pinning 18

Casing and conductor saws 20

CASE STUDIES 22

Jack-up boat well decommissioning 23

SABRE™ Abrasive Jet CuttingSystem used to abandon Camelot 24

One-stop decommissioning solution 26

Rising to the challenge of RiglessSlot Recovery 28

The world’s first Rigless PlatformWell Abandonment 30

OUR FULL RANGE OF SERVICES 31

MAKEITHAPPEN.

“CLAXTON HAVECONTINUALLY INVESTEDIN OUR TEAM ANDPROPRIETARY TOOLINGWITH THE RESULT THATTODAY THE COMPANY HASCOMPLETED OVER 280CUTTING AND RECOVERYPROJECTS, OVER 85WELLS CUT AND OVER130 SUSPENDED WELLSABANDONED.”

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Decommissioning has become an integral part of theoffshore industry over the past few years as operatorsseek to reduce their asset stock and remain profitable atthe same time. To achieve this, it’s important that clientshave a reliable and expert supply chain to rely on forguidance and support.

Claxton has a long standing record working on decommissioning projectsaround the world and have invested in creating a portfolio of comprehensiveservices. Experienced in platform, subsea, rigless and vessel basedcampaigns, Claxton supports well decommissioning by providing risers,wellhead removal, conductor severance, well P&A and solutions to overcomeintegrity issues with platforms or ageing well infrastructure.

Our experience, coupled with extensive in-house tailored engineeringcapabilities and a proven record of managing successful projects, makesClaxton the confident choice for platform and subsea well abandonment.

The content of this guide shows how we have shaped a turnkeydecommissioning service that has already helped hundreds of operatorsand projects around the world achieve their desired outcomes.

Thank you for taking the time to read this brochure. We look forward tohelping with your decommissioning project very soon.

Robert LeggettDecommissioning Product Leader

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YOUR PROJECT NEEDS TO DELIVER.

WE’LL MAKE ITHAPPEN.

RIG AND RIGLESS DECOMMISSIONING SERVICES

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Operators are now under increasing pressure to reduce costsand the focus on decommissioning is that much greater. However, the scale of cost reduction required means lookingbeyond immediate short-term efficiencies and thinking morestrategically of ways to reduce costs in the long term.

Claxton’s growing catalogue of success across the life of field, includingbeing involved in many of the original drilling projects in the North Seahas enabled us to provide a decommissioning capability that oftenexceeds those of much larger competitors.

Our well abandonment experience stretches back over 20 years and weperformed the world’s first rigless platform well abandonment campaignon the Esmond, Forbes and Gordon field in 1995.

With Claxton’s extensive knowledge and experiences of welldecommissioning projects around the world, we define our uniqueoffering as one that considers best practice that can be applied atdifferent stages of the decommissioning process. We are also able todraw from interconnected disciplines from across the Acteon group ofcompanies and third party partnerships for specialist analysis work andmanufacturing/machining where required. This enables us to define afull service offering for projects on a case by case basis.

Claxton has grown significantly over the years in order to respond to ourclients operating needs. The company’s integration strategy means wecan offer comprehensive decommissioning packages to our clients forthe following applications:

• Platform Wells (Rigless, Rig-based or combined ‘SIMOPS’)• Subsea Wells• Casing Recovery (Drilling Support Operations).

As well as describing some of the decommissioning projects Claxtonhave been involved in, this guide will give you a summary of theprocesses and procedures we can offer to abandon your wells reliably,successfully and safely.

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DECOMMISSIONINGSERVICES

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“CLAXTON’S TOOLS ANDPROCESSES HAVE DEFINEDRIGLESS AND RIG-BASEDDECOMMISSIONING ANDHAVE A PROVEN RECORD.”

DECOMMISSIONING SERVICES

PLATFORM WELLABANDONMENT –RIGLESS, RIG-BASEDOR COMBINED‘SIMOPS’

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PLATFORM WELLABANDONMENT - RIGLESS, RIG-BASED ORCOMBINED ‘SIMOPS’For platform well abandonments, wecan deploy our innovative range ofequipment along with providing ourexpertise in abandonment planning,P&A of the well and full recovery inorder to support you throughout thewhole lifetime of your project.

Claxton have built an enviable reputationin providing a rapid response tocustomer’s needs - whilst alwaysseeking best practice solutions in themost cost effective and safe way.Our ability to combine our large rentalinventory with a fast-track design-analyse-build engineering service meanswe’re often uniquely placed to respondquickly and responsively.

Operators Phase Claxton offers

Project Planning • We provide a collaborative approach using our experience toidentify potential problems and offer ideas and solutions toovercome these

• Guide obstruction removal• Centralizer removal• Review of available/existing information • Review of well structural Integrity issues• Review of the platform structural integrity issues • Review the wellhead infrastructure• Review of available facility services• Surveys• Feasibility study of recovery options• Interface review and planning• Development of procedures• Design analysis and bespoke engineering• Project management• Plan critical path activities• Establish P&A Programme and execution methodology.

P&A of the Well • Wellhead preparation services and deconstruction• Flushing and stinging services• Integrity testing• On-site machining• Xmas Tree removal• Hot bolting• Supply of risers and the wellhead/B.O.P interfaces• Riser tensioning (tension rings and tension systems)• Platform SWAT™ to enable setting of well barriers• Tubing severance and removal• Camera system for well inspection• Supply of ‘Wellhead Jewellery’ for cementing services.

Recovery • Installation of the appropriate recovery system• Guide obstruction and centralizer removal• Downhole severance:SABRE™ AWJCS (abrasive water jet cutting system), diamondwire, hydraulic cutting tools, mechanical cutting

• Cut verification• Surface severance and conductor recovery (single or

multi-string):Drilling & pinning, lifting tools and bespoke lifting devices,bandsaws, conductor/riser handling, marine growth removal,cut joint preparation for safe backload operations

• Installation of deck hatch covers to make well slots safe.


Project Planning • We provide a collaborative approach using our experience to identify potential problems and offer ideas and solutions toovercome these

• Review of available information

• Vessel based surveys and tooling to enable informationgathering (TACRT - Temporary Abandonment Cap Retrieval Tool, camera systems)

• Review of well structural integrity issues

• Review of the wellhead infrastructure and over-trawlable structures

• Bespoke wellhead tooling

• Riser and structural analysis

• Riser design and selection

• Feasibility review of recovery options

• Interface review and planning

• Development of procedures

• Design analysis and bespoke engineering

• Project management

• Establish P&A programme and execution methodology.

P&A of the Well • Supply means of interfacing to the wellhead: Hydraulic connector for the wellhead and Xmas TreeConnector control systems and umbilical’s IWOCS(Intervention Workover Control Systems)

• Supply of riser systems:To suit 18.3⁄4" or 13.5⁄8" wellhead systems, 7" intervention riser,VIV (Vortex Induced Vibration) management

• Riser tensioning (tension rings and tension systems)

• TACRT - Temporary Abandonment Cap Retrieval Tool and LPP - Low Pressure Packer for mudline wells

• SWAT™ – Suspended Well Abandonment Tool

• Through riser cementing optimisation.

Recovery • Recovery of the wellhead using bespoke wellheadrecovery tool

• Wellhead and tree lift tools

• Subsea drilling & pinning

• Severance:SABRE™ AWJCS (abrasive water jet cutting system),diamond wire, mechanical cutting, and cut verification.


SUBSEA WELLABANDONMENT

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SUBSEA WELLABANDONMENTSubsea well intervention/abandonment offers many challengesand requires as much advanceplanning as possible. The cost of thishas also in the past inhibited projects.With Claxton’s subsea wellabandonment execution model andsupporting product set we can makeit much more viable.

We provide a wide range of subsea wellabandonment bespoke tooling solutionsand you will find innovation throughcontinued R&D of new products andfrom our core team’s passion to solveoperating challenges.

Claxton have delivered many successfulcampaigns across the world with a scopethat can include the riser system andwellhead interface through to the subseaseverance and abandonment. Ourequipment can be mobilised quickly andcost efficiently for all your bespokesubsea well abandonment requirements.


Project Planning • We provide a collaborative approach using our experience to identify potential problems and offer ideas and solutions toovercome these

• Review the wellhead infrastructure

• Surveys

• Feasibility study of recovery options

• Review of available services

• Interface review and planning

• Development of procedures

• Design analysis and bespoke engineering

• Project management

• Plan critical path activities.

Recovery • Severance:SABRE AWJCS (abrasive water jet cutting system),diamond wire, hydraulic cutting tools, mechanical cutting and cut verification

• Surface severance and conductor recovery(single or multi-string):Drilling & pinning, lifting tools and bespoke lifting devices,bandsaws, conductor/riser handling, marine growth removal,cut joint preparation for safe backload operations

• Installation of deck hatch covers to make well slots safe.


CASING RECOVERY(DRILLING SUPPORTOPERATIONS)

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CASING RECOVERY(DRILLING SUPPORTOPERATIONS)Claxton also uses its field proventooling and methodologies to supportdrilling activities. We recognise thatoperators now need to take a differentapproach to their future abandonmentliabilities during the initial upfrontexploration and appraisal welloperations.

The environment cementation to form thebarrier is now often undertaken at thedrilling phase which can lead to higherthan planned cementation at mudline andconsequently a requirement to undertakea recovery of the multiple casing strings.

Claxton can offer the full suite of toolingto perform the down-hole severance andrecovery of multiple strings.

PRODUCTS

SABRE™

SUBSEA ABRASIVECUTTING

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SABRE™ SUBSEAABRASIVE CUTTINGThe Claxton SABRE™ abrasive cuttingsystem is proven to simultaneouslysever all the casings in a well,regardless of casing loading,eccentricity, or annuli contents.

Proven technology

SABRE™ has proven to be an invaluabletool and has seen successful use on someof the most significant abandonmentcampaigns. SABRE's abrasive jet exits thetool at transonic speeds – making lightwork of even composite materials such ascemented casings.

Using a jet of naturally occurring cuttingcomponents (garnet, water and air),SABRE™ has a low environmental impact.The system can be deployed from avessel or platform, allowing simultaneousabrasive cutting of multiple well casingswithout impacting adjacent infrastructure.

Benefits of SABRE™:

• Casings can be cut and recovered simultaneously or individually

• Can enter wells down to 6.5⁄8" bore

• Internal or external cuttingapplications

• Modular system footprint can be adapted to a wide range ofapplications/deck layouts

• Cutting manipulators available to suit all standard casing sizes

• Packer system improves cuttingperformance through de-wateringof the wellbore

• Proprietary Claxton jet technology ensures cutting performance

• Extensive track record - proven onnumerous successful campaigns

• Fully NORSOK compliant to Z-015.

SABRE™ DECK SPREADDesigned with flexibility in mind, SABRE’s deck spread is fully modularand adapts to a wide variety of decklayouts and locations.

PRODUCTS

SWAT™

SUSPENDED WELLABANDONMENTTOOL

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SWAT™ SUSPENDED WELLABANDONMENT TOOLClaxton has successfully deployedour cutting, abandonment andrecovery tooling across the worldfor our customers. This includesmany category 2 wells of which allrequired a shallow cement barrierspanning through all of the casingannuli. This experience directlyinfluenced the development of ourmulti-award winning SuspendedWell Abandonment Tool – SWAT™. Delivered in conjunction with oursister company, OIS, SWAT™ opensthe opportunity for innovative, costsaving multi-operator campaigns.

SWAT™ is deployed through a moonpool,landed on the wellhead and then usedto carry out casing perforation andplacement of the required cement barriersin the well. The wellhead can then besevered using SABRE™ subsea abrasivecutting tool and recovered using theClaxton subsea wellhead recovery tool.

Suspended Well AbandonmentTool benefits:

• Deployed from a vessel, removing the need for a drilling rig

• A one-stop solution to place thefinal cement barrier across all annuli

• Single-pass cementing andpressure testing

• Deployed as part of a totalsuspended subsea wellabandonment package

• Proven across multiple successfuloffshore campaigns.

SWAT™ extension module

The Claxton extension module for SWAT™

enables us to set environmental barriers

and intermediate barriers, increasing thenumber of wells that can be abandonedusing rigless – vessel based tools anddelivers cost-saving opportunities.

The extension module utilises Claxton’sexisting SWAT™ tool to enable cementto be displaced to the required location inthe well. A wiper ball is positioned beforeand after the cement column, whichensures that the bore is cleaned ahead ofthe cement column, and that the cementis isolated from contamination. Thecement is then displaced to the requiredposition in the well by pumping seawaterto the required depth. In the most recentwell abandonment campaign, the topof the barrier was displaced to 2400 ftbelow mudline.

TACRT - Temporary AbandonmentCap Retrieval Tool

The Claxton TACRT provides a diverlesssolution for the removal of temporaryabandonment caps from mudline wells.The tool has been designed to bedeployed from a vessel and utilises abespoke joint connection to facilitateeasy make/break of extension joints.The tool is capable of retrieving caps inexcess of 100 ft below mudline.

Unique, joined up ActeonGroup capability

Claxton and its sister company OIScombine their onshore and offshoreengineering experience to deliver aunique well abandonment capabilityand open the door to vessel basedsubsea decommissioning campaigns.

OIS have extensive experience ofdelivering turnkey solutions for wellP&A of suspended wells and provideour Suspended Well AbandonmentTool – SWAT™ through an exclusivepartnership.

This union of Claxton’s tooling andOIS’ project delivery gives operators areliable and economical alternative toabandon Category 1 and Category 2wells. Using a light weight constructionvessel negates the need for a rig whichcan significantly reduce project costs.

PRODUCTS

DRILLING ANDPINNING

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DRILLING AND PINNINGThe Claxton drilling and pinningsystem provides an efficient methodfor securing multiple casing stringsfor safe recovery operations.

The system can be provided as part ofa package that includes rapid cutbandsaws and/or subsea abrasivecutting for severance and hydraulicjacking systems for recovery. Ourmethodology enables simultaneousretrieval of multiple casing strings, andis designed to work independently ofrig operations.

As a cold work technique our method isespecially suited to abandonmentoperations where adjacent wells maystill be in production.

Features of our drilling and pinningcapability include:

• Single drilling units available forapplications where space isrestricted

• Double drilling and pinning unitsavailable for simultaneous boringof both sides of the conductorand casings

• Modular design with multiplehandling points for ease of installation and operation

• All units certified for zone IIapplications

• Surface or subsea applications

• Conductor end caps provided to mitigate dropped object potential.

Crucially, when compared toconventional methods, using our systemto drill, pin and recover the conductormeans less deck space is required forthe recovered casings – thereforedisposal logistics are simplified andcosts reduced.

Additionally Claxton has significantexperience in drilling and pinning agedconductors (surface and subsea toolsavailable) to ensure safe recovery.

PRODUCTS

CASING ANDCONDUCTORSAWS

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CASING ANDCONDUCTOR SAWSClaxton’s rugged casing andconductor saws quickly cut throughsingle or multiple casing stringsand provide a versatile solution formany casing and conductorseverance applications.

Cemented annuli and casing stringeccentricity pose no issue to our sawsin the field.

In addition to cutting equipment we cansupply complete cutting and recoveryoperations. This includes theengineering of recovery procedures forspecific challenges – e.g. dealing withfatigued connectors.

Features of casing andconductor saws:

• Extensive selection of saw blades ensure maximum efficiency on alltubular types

• Rapid cut speed reduces rig time and associated costs

• Captivation system ensurescorrect orientation of the blade

• Small footprint and fullycontainerised control system lessens deck space required forrecovered casings

• Can accommodate tubulars up to 60" OD, facilitating diverseseverance opportunities

• Innovative wedging systemprevents saw blade jamming

• Blade severance feature minimises saw down-time

• Horizontal or vertical saworientation facilitates application adaptability

• The standard diamond wire saw can deliver fast effective subsea cuts in water depths of up to 600ft

• RAPIER™ saw’s cold work technique reduces safety hazardsallowing severance in most sites: it is certified for Zone II applications

• Hydraulically powered for robust power and compactness.

DECOMMISSIONINGCASE STUDIES

Claxton’s promise is that we’ll make your project happen – find out how we apply this focus to our clients’ decommissioningprojects in the following articles.

JACK-UP BOAT WELL DECOMMISSIONING 23Learn more about how Claxton’s SABRE™ subsea abrasivecutting system provided a safe and cost-effective way todecommission a well in the Irish Sea.

SABRE™ ABRASIVE JET CUTTING SYSTEMUSED TO ABANDON CAMELOT 24Proprietary, field-proved Claxton technology delivered reliablesubsea cutting - find out how.

ONE-STOP DECOMMISSIONING SOLUTION 26Comprehensive, bespoke and flexible services helped operatorplug and abandon wells in the southern North Sea.

RISING TO THE CHALLENGE OF RIGLESSSLOT RECOVERY 28Find out how Claxton delivered innovative rigless slot recoverysolutions offshore in Denmark.

THE WORLD’S FIRST RIGLESS PLATFORMWELL ABANDONMENT 30See how Claxton performed the world’s first rigless platformand well abandonment – developing a methodology that hassubsequently been used on multiple slot and conductorrecovery projects.

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CASE STUDY 1: DECOMMISSIONING

JACK-UP BOATWELLDECOMMISSIONING

Operator uses the Claxton SABRE™

subsea abrasive cutting system toreduce rig costs.

Responsible operators are activelyplugging and abandoning offshore wellsthat have reached the end of theiroperational lives. This decommissioningwork provides long-term protectionfor people and the environment, andhelps to protect a company’s reputationand secure its licence to operate.However, the economics of fulfilling wellabandonment obligations can bechallenging, particularly where a rigneeds to be mobilised to allow the workto be performed safely.

IS A RIG REQUIRED?The operator wanted a safe andcost-effective way to decommission awell in Morecambe Bay in the Irish Sea.Traditionally, this work scope, whichincluded cleaning and dredging the well,placing cement barriers in the bore andcutting and recovering the casing, would require the use of a rig. However,the client wanted a safe and efficientsolution that could be deployed from itsexisting jack-up workboat.

A COST-EFFECTIVESOLUTIONClaxton provided well abandonmentservices that were deployed using aflexible line from the back of a boat,without the need for an expensive rig.These services included the use of theSABRE™ subsea abrasive cuttingsystem, cement deployment equipmentand packers. Claxton also suppliedand managed third-party ROV andcementing services.

Critically, specialist tools and deploymentequipment enabled the use of therelatively small, jack-up workboat, whichwas already available to the operator.

The flexible SABRE™ system useshigh-pressure abrasive water jets attransonic speeds to cut through multiplecemented casings. Casings can becut and recovered simultaneously orindividually. The system has a lowenvironmental impact, using onlynaturally occurring garnet, water andair in the jet.

BENEFITS

Claxton’s decommissioning, designengineering and offshore teams workedclosely with its supply chain and theoperator to successfully abandon thewell. The ability to perform the work froma jack-up boat removed the need tomobilise a rig, saving rig mobilisation andrental costs.

Robert Leggett, DecommissioningProduct Leader, Claxton, said, “Workingwith the client to successfully abandonthe well was a pleasure. This projectwas particularly memorable, as webelieve that we achieved a first with theplacement of a cement barrier nearly300 m below the mudline using aflexible line from a jack-up boat. Ourexperience with SABRE™ and relatedplug and abandonment services werekey to to the project’s success. We havesince worked with the client onnumerous similar well abandonmentassignments, strengthening our excellentlong-term relationship.”

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SABRE™ ABRASIVEJET CUTTINGSYSTEM USED TOABANDON CAMELOT

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Proprietary, field-proven Claxtontechnology delivers reliablesubsea cutting.

THE PROBLEMThere are serious doubts about whetherKing Arthur’s Camelot ever really existed.In contrast, the UK North Sea gas fieldsand production platform of the samename certainly did, though the evidencehas disappeared.

The complete decommissioning of theNorth Sea Camelot fields and theremoval of Camelot Alpha platformbegan at the start of 2012 with theplugging and abandonment of the fields’six platform wells. The next stage wasseverance of the well casings some5 m below the seabed.

THE SOLUTIONThis was a task for which Claxton wasideally qualified, as the DecommissioningProduct Leader Robert Leggett explained: “We have established an enviable recordin the North Sea for this kind of workusing our SABRE™ internal abrasivecutting system, which enables us tosever all the casings within a wellsimultaneously, regardless of the loadingon the casings or any eccentricity. Thesystem uses a mixture of air, water andabrasive garnet at up to 1000 bar to cutthrough the multiple steel casings andany cement within the various annuli.We generally then drill and pin thecasings so they can be safely withdrawnin a single operation.

“Part of the process is to prove that wehave achieved complete severance

within the well; for this, we use a Claxton-designed jacking system to raise thecombined casings temporarily and thenease them back down for completeremoval later.”

This was the process Claxton followedwith the Camelot wells, which containedcasings ranging in diameter from 9-5⁄8"to 30". The cutting process presenteda few challenges for the team, ofwhich one was working out how toaccommodate the various componentsof the SABRE™ system in the limiteddeck space available on the small,normally unmanned Camelot platform.

Support beams were used to spreadthe load of the components required torun the SABRE™ system. The beamsalso provided a secure foundation forthe jacks used to confirm the cuts. The Claxton team also designed askidding package to shift the equipmentbetween the wells, thereby reducingreliance on the platform crane andshortening the overall time taken forthe job.

THE RESULT“There was much communication withthe client, and we jointly planned the jobvery carefully before we went offshore,”said Leggett. “Once the job started, wehad eight people, including supervisors,split into two teams that shuttled backand forth to the platform, thus ensuringvirtually 24-hour working.”

In addition to the severance work,Claxton designed and supplied abespoke lifting cap for the well casingsets. This enabled each set to be easilyand safely recovered using a heavy-liftbarge in a separate operation carried outafter the Claxton team had left the site.The SABRE™ system was introducedin 1997 and has now been used tosever about 85 wells in the North Seaand the Gulf of Mexico. This includes16 wells in a campaign that was partof the Shell/Esso Indefatigable fielddecommissioning project in 2011.SABRE™ is fast becoming the tool ofchoice for this kind of work because of its performance, flexibility and reliability.


ONE-STOPDECOMMISSIONINGSOLUTION

Comprehensive, bespoke andflexible services help an operatorplug and abandon their wells in thesouthern North Sea.

The field had been producing naturalgas for over 40 years. At its peak, itsupplied around 10% of the UK’s gasrequirements. In the 1990s, an infielddrilling programme and new productiontechnologies revitalised the field.Nevertheless, many older wells hadreached the end of their operationallives, prompting the beginning of amultiyear well abandonment campaign.

OBSOLETE INTERFACESAND HIGH DEMANDThe age of the wells is challenging.Many of the well interfaces are obsolete,which means that some well interventionequipment needed to be developedspecifically for the campaign.

The Claxton decommissioning teamworked closely with the operator tounderstand the project requirements.From the outset, it was clear thatClaxton’s SABRE™ subsea abrasivecutting system would be a vital part ofany campaign to cut and recover thewells. However, SABRE’s growingreputation meant that the units were inhigh demand, with healthy backlogs,and not immediately available.

RAPID REACTIONClaxton promptly manufactured a newSABRE™ unit with a reduced footprintdesigned specifically for the clientscampaign.This unit was deployed inDecember 2013 and has since been incontinuous service. The system isreliable, flexible and easily movedbetween platforms and vessels. It alsohas a low environment impact, using onlynaturally occurring garnet minerals, airand water in its transonic-speed abrasivejet, which is capable of severing wellswith multiple cemented casings. The well-dewatering packer was also upgraded.

The project scope also includes supplyof on-site machinery, surface risersystems, bespoke interfaces, bandsawsand drills to cut the recovered sections,and debris caps and slings for safe multi-string backload.

BENEFITSThe operator is using Claxton’sequipment and services to improve its

decommissioning efficiency and capacity,which helps to reduce costs and releaseresources for other projects.

The company was able to takeadvantage of Claxton’s extensive riserinventory to get what it needed quickly.Claxton’s on-site machinery and skilledengineers were also able to swiftlydeliver bespoke equipment.

Robert Leggett, DecommissioningProduct Leader, Claxton, said, “Wereally wanted to work with the operatoron its campaign. I am delighted thatwe were able to react quickly, includingmanufacturing a SABRE™ systemspecifically for the project. It is great tosee this and our casing-recoverysystem in two years’ continuousservice and with more work to do.The ability of our multi-skilled team tomove from one operation to anotherwithout the need for continuous crewchanges was particularly valued. Weare now collaborating with the client onnew systems and methods of work tofurther increase operational efficiency.”

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RISING TOTHE CHALLENGEOF RIGLESSSLOT RECOVERY

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Claxton delivers innovative solutionsin Denmark

When Maersk contacted Claxton in April2013 about a slot recovery job, it wasapparent that the task in the Tyra Eastfield in the Danish sector of the North Seawould be a little more complex than themechanical removal of casing followed bydrilling a sidetrack well. The original wellwas drilled in the 1980s and, during itsconstruction, a large piece of downholeequipment, the bottomhole assembly(BHA), had become stuck in it andprevented the well from being completedand contributing to gas production fromthe reservoir. Maersk’s decision torecover and reuse the slot would involveremoving the BHA.

Claxton had an established relationshipwith Maersk for the supply of whipstocksfor slot recovery and, during the initialconsultation, Claxton engineerssuggested a rigless approach, as one ofthe project engineers at Claxtonexplained. “A rigless operation would helpto minimise the cost and provide a moreflexible approach to project timing. Thiswas critical because the area for theoperation had logistical issues around rigmoves with the potential to greatlycomplicate the project.”

Claxton’s team visited the well in May2013 to assess the situation and developa recovery plan. The BHA stuck in theconductor pipe was about 15 m long andhad a diameter of 8-9". About 6-9 m of itwas protruding above the seabed.

After working with Maersk to fully assessthe nature of the challenge, Claxtonbrought in the multidisciplinary teamneeded to deliver the project. Thisinvolved close integration andcollaboration with specialist cutting

companies and a dive support vesselfrom Royal Boskalis Westminster NV.

The programme started by deploying aspecialist casing cutting system toremove a section of the conductor andleave the stuck BHA intact but exposed.This approach called for modification ofthe cutting equipment and the subseaapplication of a system that is normallyused on the surface.

“Once the conductor was cut andremoved, we prepared a bespoke liftingdevice using an air hoist on deckdeployed through an A-frame while diversclamped the lifting gear to the BHA.

The BHA was too heavy to recover inone piece which meant that it wouldhave to be cut subsea,” the projectengineer continued. “We used two sizesof diamond wire cutting machine, thesmaller to sever only the exposed BHAand a larger to cut through both theremaining conductor stump and theBHA simultaneously. A key considerationhere was making the cut so that it lefta smooth and flush surface on the endof the conductor. Once the cuttingmachine had sliced through theconductor and BHA, we were able torecover the top section.”

During planning, the orientation of theremaining BHA relative to the conductorstump was uncertain. This requiredClaxton to create a unique whipstockwith a slot beneath the landing plate thatwould enable it to capture securely theexposed part of the BHA in anyorientation. The top half of the whipstockwould rotate on this base and enable thenew well to be kicked off in any direction.Claxton’s experience and knowledge ofwhipstock design was the key toproviding an effective engineered solution.

“This was a fairly unusual slot recoveryproject,” the project engineer said, “andthat made it quite difficult to estimatehow long it would take to complete.Our initial plan called for a little over 20working days, but we managed tocomplete it in less than 16 days, a figurethat included more than three dayswaiting-on-weather. Naturally, we aredelighted to have successfully completedthe first rigless recovery of a stuck BHA inthe North Sea. The key to the success ofthis project was teamwork. Thesimultaneous operations were conductedsmoothly and with great efficiency.”

The integrated team led by Claxtondelivered the full work scope in onlythree months, including designing,manufacturing and testing the bespokeequipment. The cooperation betweenClaxton, Boskalis, and the Maerskstaff involved on Tyra East made itpossible to deliver what was needed ina very tight timeframe. The project wascompleted ahead of schedule, despitethe weather delay.

The senior drilling engineer from Maerskdrilling department, echoed thesignificance of the collaborative approach:“This was a very challenging piece of workrequiring integrated planning across manydepartments and companies, not tomention the extensive amount of design,manufacturing and testing of equipmentClaxton designed especially for the job indouble-quick time.”

Safety and deadlines were the mainconcerns for this operation and therigless approach saved substantial rigtime and reduced the associated costswhile increasing the flexibility of theproject timings.

OFFSHOREOPERATIONS

ONSHOREOPERATIONS

YOUR PROJECT NEEDS TO DELIVER.

WE’LL MAKE ITHAPPEN.

OUR FULL RANGE OF SERVICES

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THE WORLD’SFIRST RIGLESSPLATFORM WELLABANDONMENT

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Claxton performed the world’s firstrigless platform well abandonmentover a decade ago – developing amethodology that has subsequentlybeen used on multiple slot andconductor recovery projects.

THE PROBLEMDuring 2003, a 38-year-old well in theSouthern North Sea was identified ashaving suffered a corrosion fatigue failureof the 20" conductor approximately

6 m below sea level. Consequently, thewell was immediately shut in.

Claxton had already built an impressivetrack record of performing platform wellabandonment/slot recovery on theMaureen, Esmond, Gordon, Beryl andRijn platforms, and was an obviouschoice for this well abandonment project.

THE SOLUTIONClaxton provided a conductor recoverysystem to interface with the Lemanplatform comprising lifting supportbeams, boom cranes and a hydraulicjacking system. Much of this equipmentwas bespoke for the project andClaxton fast tracked this design andbuild activity to meet a tight weatherwindow, as the operator was concernedthe conductor would not survive theharsh North Sea winter.

THE RESULTClaxton, working with other Acteoncompanies, successfully completed atotally rigless well abandonment onthe normally unmanned platform. Thiswas achieved within the allottedtimeframe. All of the following activitieswere performed without using a rig:

• Downhole perforating andcementing operations

• Subsea tree removal and tubingseverance and recovery

• Severance of the casing strings below the mudline

• Recovery of the casing string.

The operator indicated that the overalloperation was achieved at less than50% of the cost of an equivalentrig-based solution.

DUBAI

ClaxtonPO Box 262490Jebel Ali Free ZoneGate 5, South SideFZS1 AL05 Dubai

T: +971 4 8863540E: [email protected]

NORWAY

Claxtonc/o Finnestadgeilen 11, Building 18Dusavik Base, N - 4029StavangerNorway

T: +47 51 83 66 74E: [email protected]

SINGAPORE

Claxton 107 Tuas South Avenue 8Offshore Marine Center637036 Singapore

T: +65 6705 5825 E: [email protected]

Learn more at:www.claxtonengineering.com Tel: +44 (0)1493 744500

UK HEAD OFFICE

ClaxtonBureside HouseNorth River RoadGreat YarmouthNorfolk, NR30 1TEUK


ABERDEEN

ClaxtonTern Place House, Tern PlaceBridge of DonAberdeenScotlandAB23 8JX


MAKINGDECOMMISSIONINGHAPPEN.Proven experience combined with world-class designand project delivery mean you can trust Claxton tomake your offshore decommissioning happen.

www.claxtonengineering.com@ClaxtonNews Claxton Engineering

Documents

MAKING DECOMMISSIONING HAPPEN. · decommissioning services platform well abandonment – rigless, rig-based or combined ‘simops’ 08 09 platform well abandonment - rigless, rig-based