Case History Platform Based Well

Abandonment with HWO Unit

SPE Aberdeen 4th European Well Abandonment Seminar

K10-B Platform Wintershall Noordzee bv

K10-Bravo Platform History

• Two wells drilled prior to platform installation (1981)

• K10-B2 produced 35,000 bbls from Main Bunter sandstone during production test (1982)

• Six additional wells drilled prior to production kick-off (1983)

• To maintain production rate two infill wells were drilled (1987/1989)

• Eleventh well drilled (1996)

• Production shut down due to depletion of Rotliegendes gas reservoir (2001)

• Gas processing facilities removed from platform (2003)

Location K-10 Bravo field

Four Phase P&A Process Approach

• Phase I: Evaluation of surface facilities, down hole equipment and well integrity. Plug wells in preparation for well abandonment.

• Phase II: Retrieve completion and un-cemented casing elements. Set plugs compliant to regulatory requirements.

• Phase III: Preparatory measures for cutting and lifting cemented casing/conductor elements. Lifting pad eyes installed and MPI tested.

• Phase IV: Wellhead removal, casing/conductor cutting 6 m below seabed. Cut elements are lifted 1 m to confirm cut and set back for removal by heavy lift vessel in combination with platform removal.

Target to perform operations with Zero accidents, incidents and

near misses in a cost efficient manner.

Top View Platform

10 mT crane

Production platform

Decommissioned 10 mT crane

Wellhead platform

Re-commissioned and downgraded to 10 mT SWL

Skidding System

• For rig up, the unit’s base was skidded to within range of the crane.

• BOP assembly was relocated by platform crane after skidding the HWO.

• Skidding system provided with outriggers for anchoring.

HWO rigged up on skidding system

HWO unit

Accommodation Limits

• K10-B Platform living quarters limited to 24 beds

Obvious choice; accommodation barge or P&A execution by jack up rig with it’s own accommodation.

• Multidisciplinary, competent HWO crew of five personell per shift. Able to perform both HWO duties in combination with all required pumping, cementing as well as assist in Wireline operations.

• Sufficient bed space for core rig crew, additional service companies and company representatives.

HWO Unit

• HWO consists of a jack and slipbowl assembly performing a sequence for handling pipe.

• Precise control.

• Small footprint in relation to pulling force.

• Slower workstring handling compared to a derrick system when running stands.

• Not a hands off operation.

Due to a slot in the drilling sequence a jack up rig was moved to the K10-B platform.

During this rig intervention:

• Two wells were abandoned as far as the completion and un-cemented casing sections.

• Later comparison proved the HWO unit to be more time efficient.

Tubular Handling

• In the context of P&A a creative approach can reduce the number of trips with workstring.

• In some cases completion string can be used as a cement string.

• Do not cut Conductor and top casing in small sections to handle by platform crane.

Stuck Pipe Situation

HWO units are capable of absorbing shock loads through the cylinders and hydraulics.

Possibility to apply downward movement on the tubular. Push capability.

Hydraulics provide precise control.

Execution Phase II

The provides a general outline for on site execution. Details may vary between wells. Phase II was done with BPC’s Space Saver II unit with a pull capacity of 385 klbs. / 175 Ton

• Release/cut completion and retrieve.

• Pull completion above future TOC.

• X over to drill pipe RIH to cement plug setting depth.

• Set two cement plugs at specified depths and record TOC’s.

• Wire line punch at 13 3/8 “ casing shoe.

• Circulate to confirm communication with annulus.

• Set third cement plug and record TOC.

• Pressure test.

• Nipple down BOP stack and tubing head spool.

• Cut and retrieve 7 5/8” and 9 5/8” cemented casings.

• Pump viscous pill and set final cement plug.

Execution Phase III

Preparatory measures for cutting and lifting cemented casing and conductor elements. Lifting pad eyes installed and MPI tested.

Prepare platform

• Weld lift points on wellhead

• Remove redundant equipment

• Install deck skidding beams

• Install temporary sea water pump

• Other preparation prior to arrival of the HWO unit.

Execution Phase IV

The following provides a general outline for on site execution. Details may vary between wells. Phase IV was done with BPC’s Pipe-puller unit, with a pull capacity of 250 mT.

• Install Tension cylinders on wellhead for pre tension.

• Space out 6 m below seabed and cut a window in the 13 3/8” casing.

• RIH with spear and retrieve casing.

• Space out 6 m below seabed and cut a window in the 20” casing.

• Change cutting knives to cut 30” and do same.

• Pick up 1 m on 20” and 30” to confirm cut.

• Release Tension cylinders and move to the next well.

Execution Phase IV

For the final stage of the P&A the decision was made not to pull conductor/casing sections in pieces to be handled by the platform crane. Instead, as a heavy lift vessel will perform the platform removal, this vessel is also used to lift casing sections with wellhead in one piece. One transport to scrap yard.

Tensioning System

Cutting the 30” conductor and 20” casing mechanically, poses a risk to the cutter used; the weight of the components may crush the blades of the down-hole cutting tool.

The BPC pre-tensioning system relieves the cutting blades from casing/conductor weight.

The retraction of cylinders indicates a successful cut.

With the same cylinder assembly the casing/conductor is then lifted 1 m to validate the cut.

Max pull on cylinders: 200 ton

Pretensioning cylinder assembly

Tensioning System

Pretensioning cylinder assembly

Cut casing section

Conclusion

Jack Up is generally the first choice for P&A on platforms.

As there’s no question of financial gain on abandonment campaigns and original budgets are often tight, operators increasingly consider more cost effective alternatives.

In comparison to other abandonment techniques HWO has both financial and technical benefits.

Crew numbers are low and can be tailored to suit the bed space available.

Platform must be suitable to accomadate people and equipment.

Conclusion

P&A is highly unlikely to remain within the original allocated budget, due to increased regulations.

K10B proved HWO Units are capable of performing P&A within the the original allocated budget;

2 wells partly abandoned by drilling rig (only phase 1). Cost; 29.7 % of original P&A budget

Remaining 9 nine wells and phase IV on the partly rig abandoned wells was still within the budget. 55.6 % of original P&A budget

55,6 29,7

14,7

HWU 9 wells

Jack up 2 wells

Remaining budget

Conclusion

Phase II conducted in 74 days excluding rig up/down time. 83 days including rig up/rig down.

Phase IV conducted in 32 days, excluding rig up/down time. 40 days including rig up/down.

1% 1%

4%

94%

Abandonment efficiency

NPT BPC NPT due to third party Wait on weather Operational

Conclusion

All nine wells were successfully abandoned by the HWO unit both within the allocated timescale and budget.

Creative approach and out of box thinking, added value.

Cost and time reductions were also established as a result of the phased abandonment approach and the efficient co-operation between the work-over, cementing, fishing, wireline and all other supporting services.

Wintershall quote:

“The support and interaction between the different disciplines shall for Wintershall act as an example for future projects.”

Thank you.

Any questions?