Per Buset

Island Offshore

Plugging & abandonment of subsea completed wells – can this be done from a mono-hull vessel?

Agenda

• In-depth study of topic performed 2012, Scope of work

• Findings from study, and what has already been done

• Conclusions

Study - Scope of Work

• Island Offshore have over the past years looked into what is required for a full P&A of a subsea completed well from a Light Well Intervention vessel

• In-depth study performed 2012, including:

– A detailed step-by-step description of a proposed P&A well, illustrated with well equipment/well drawings also showing fluids and barriers according to NORSOK D-010

– Cost and time estimate

– Risk assessment of the entire operation

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ISLAND WELLSERVERLIGHT WELL INTERVENTION VESSEL

Type: UT 767 CDClass: DnV Ship Shaped Well

Intervention Unit (I), E0, DK+, HL(2,8),Dynpos AUTRO,Comf-V(3)

Deadweight: 9200 tonsLoa: 116,00 mBreadth: 25,00 mDeck: 1050 m2MHT: 100/300 t Main crane: 150 t AHCAccomodation: 95 personsDelivery: 2008

The wellPre P&A Post P&A

What has been done, (Norway)

• Semi-submersible drilling rigs are doing it today

• “Island Wellserver” did partial P&A on the TOGI-field in 2011

– 5 gas injector wells

– Bull-headed tubing with MEG/Sea-water

– Set deep-set plug

– Punched tubing above production-packer

– Displaced tubing and first annulus to MEG/Seawater

– Set plugs in annulus and production-bores in tubing-hanger

– Cut flow-line from VXT

– Pull VXT

• 5 wells, 70 days, including 2 shore-visits

Sub-sea Shutoff device with Mud Recovery System, and tubing-hanger jacking mechanism

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Sub-sea Shutoff device, SSD

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Mud Recovery system for volume control

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Subsea Volume Control Skid

Wellhead Interface with level sensor and camera

Surface fluid tank with level sensor & feed pump

Fluid Line from/to Vessel

System to Control Volume during vessel based P&A

Main Components

Tubular Handling Equipment

• Island Offshore vessels have been equipped with tubular handling equipment during trenching operations, fully compliant with PSA’srequirements

• The equipment typically include

– Tubing / Pipe rack

– Catwalk-machine

– Pipe and/or tubing gripper for deck crane

– False Rotary (non-rotatable) mounted on moon pool door

– Iron Roughneck

– BX elevator

– Etc.

The Cementing Adaptor Tool (CAT)

• Features and Benefits– P&A of Cat. 2 wells with full well control from a LWIV, in accordance

with NORSOK D-010 and PSA requirements– Allows intermediate cement plugs to be placed in casing and

annulus with the Well Control Package installed on the well

• CAT functionality– Allows selective perforation of production casing to establish lower

and upper annulus communication ports (wire-line run through LWI-stack and CAT)

– Provides selective seal between stinger OD and production casingID to isolate upper and lower perforations in production bore

– Provides a circulation route for annulus cleaning (forward and reverse with returns to the vessel), and displacement and spotting of competent cement (annulus and balanced)

– Allows for pressure testing of cement plugs– In combination with the Well Control Package, maintains well

barriers/control during the operations

Patent pending 2010 (SPA)

CAT-animation

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Capability/Technology gapsCapability Comment Estimated

lead time

Wireline and pumping operations from LWIV on live wells (incl SUT) �

Field proven in numerous operations. SUT on three Island Offshore vessels

N/A

Placing primary reservoir plug by bullheading reservoir �

Proven technique from Ekofisk and numerous fields globally

N/A

Circulate cement into casing annuli without annuli access in subsea wellhead

�CAT technology exists – needs manufacturing and qualification

12 months

Place permanent barrier across control/gauge lines �

Solved by pulling tubing N/A

Pull tubing from LWIV, incl.- Tower with pulling capabilities- Break tbg hanger (subsea jack)- Tubular handling- Subsea Shutoff Device- Mud return without a riser system

�

Existing and field proven (Island Offshore)Existing and field proven (Geoprober)Existing and field proven (Island Offshore)Existing and field proven (TBA)Existing and field proven (AGR/IKM)

N/A6 mthsN/A

12 monthsN/A

Cut & recover subsea wellhead with a monohull vessel �

Existing and field proven (NCA) N/A

Prerequisites for LWIV based P&A of subsea wells*)

Check point / show stopper Reason Comment

Reservoir injectivity Place primary cement plug in liner inside the cap rock by bullheading through tbg

Tubing/liner integrity (pressure and structural integrity)

Bullheading through tbg

Reservoir pressure to low Volumetric placing of cement in cap rock

Alternatively use lighter plugging materials (e.g. Wellcem’s Thermaset)

Qualified casing cement behind liner and 13 3/8” (if cement is present)

No rigless method of replacing csg cement

Original CBL records or multilayer logging tool (new technology)

Able to break circulation behind 9 5/8” (and 13 3/8” if required)

Circulate cmt into annulus at a minimum depth of the barrier

Contingency: coiled tubing based perf &wash and/or placement of cement

*) Based on the method proposed in the study

Time estimates, investments

• Time estimate: 36 days (incl mob/demob)

• Investments required, (base case LWI-vessel):

– Subsea shut-off device

– Casing Adapter Tool, (CAT)

– Subsea jacking mechanism

• Optimisation opportunities:

– Organise P&A in batched campaigns

– Leave control/gauge line as a part of barrier

Main conclusions

• It is feasible to do a full P&A from a LWI-vessel, without shore-visit, in majority of subsea-completed wells

• What is new for P&A application?

– Use of a SubSea shut-off device

– Use of a riserless mud recovery system for fluid monitoring

– Pulling tubing from a LWI-vessel

– Casing Adapter Tool, (CAT)

• One non-compliance identified per Norsok D-010:

– Qualification of 13 3/8” casing-cement, (cement behind 2 casing-strings)

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Solution to several casings “look-trough”?

Drilled through 3 casings

Core-sample

www.maxperf.ca

Questions?