Running Subsea Trees from a Jack-up MODU Chris Wilson ...€¦ · Running Subsea Trees from a...

Chris Wilson – September 2008

Running Subsea Trees from a Jack-up MODU

Chris Wilson – Coogee Resources


Montara Development – Drilling Program

• Drill, Complete & Clean-up 2 new Subsea Development wells (Water Depth 82m)

• Re-enter 2 existing subsea wells, run a tree, complete and clean-up each well (Water Depth 77 to 82m)

• Drill and complete 3 platform wells (Water Depth 80m)

• Jack-up MODU with 400’ legs required


Subsea Trees

Tree• Vetco 13 5/8” 5000psi• Separate flow base• 4.3m(l) x 3.9m(w) x 2.6m(h)Flowbase• 3.9m(l) x 3.8m(w) x 5.1m (h)

– with guideposts installed


Two New Subsea Wells

• Wells needed to be close enough not to move the rig

• Not too close to inhibit ROV Access

• Performed 3D modelling with TMT to determine spacing

• 5m Centre to Centre• 1m Difference in

Elevation


Existing Subsea Wells

• Needed to have positioning tolerance capabilities

• Positioning on a “postage stamp” is time consuming & difficult with a jack- up


Montara Development Drilling Project Requirements

• 400’ Leg Jack-up New Generation Jack-up• Ability to drill two subsea wells at 5m centres Modified

conductor deck• Run subsea trees (preferably not picking-up off the

back of a boat) Make room under the cantilever• Be able to support the weight of the high pressure

riser and BOP’s outside of the existing conductor tensioner location Modified conductor deck

• Have positioning tolerance capability Modified conductor deck


MODU – Seadrill’s West Atlas•

K-Fels Mod V Class B

•

Leg Length –

157m (517’) capable of drilling in 114m of water

•

Derrick Capacity –

1500 kips

•

BOP Pressure Rating – 15kpsi

•

Proven Rig design (Ensco 104, 106, 107, 108, Wilcraft & Atwood Beacon)


Rig Modifications to Handle Subsea Trees

•

Relocation of the Cement Unit to allow Subsea Trees & Flow Bases to be skidded aft


Tree Skidding System

•

Train Track Style•

Easy to Install

•

No welding required•

Tree Trolleys to have capability to test trees


Conductor Deck Modification Requirements

• Space to drill 2 subsea wells at 5m centre• Ability to hold weight of the high pressure riser,

BOP’s plus a safety factor (~200MT)• Provide positioning tolerance• Handle environmental loads• Able to run trees through (if required)


Concepts


Final Design


Installation of Conductor Deck Extension


Final Product – Conductor Deck Extension


Final Product - Spreader Beam Assembly


Tree / Flowbase Running Sequence

• Recover box beam assembly to under rig floor



• Recover box beam assembly to under rig floor• Place tree onto skid trolley and skid it aft



• Recover box beam assembly to under rig floor• Place tree onto skid trolley and skid it aft• Skid in cantilever – when gap between cantilever & rig

floor is over the tree – use a crane to lift tree off the skid trolley and onto beams on the rig centre line





• Skid in cantilever – make-up tree running tool to tree





• Skid in cantilever – make-up tree running tool to tree• Lift tree off main deck and skid aft





• Skid in cantilever – make-up tree running tool to tree• Lift tree off main deck and skid aft• Run tree through the conductor deck extension


Tree / Flowbase Running Sequence• Recover box beam assembly to under rig floor• Place tree onto skid trolley and skid it aft• Skid in cantilever – when gap between cantilever & rig


• Skid in cantilever – make-up tree running tool to tree• Lift tree off main deck and skid aft• Run tree through the conductor deck extension• Lower the box beam assembly into the conductor deck

extension• Land tree and nipple-up Surface wellhead & BOP’s


Conductor Deck Extension – Lessons

• Deck was time consuming to recover and store between wells

• Support slings time consuming to move when skidding cantilever

• Box beam assembly was cumbersome• Despite the lessons – the extension deck

satisfied a wide variety of expectations


Tree Skidding System - Lessons

•

End of the track interfered with cantilever beam

•

Tree Was not on centreline (handling Issues)

•

Tolerance was tight


Subsea Trees on Jack-ups - Conclusions

• Early access to rig during construction allowed for subsea tree running to be part of the rig design

• Conductor Deck Extension ~ 8 Months from concept to delivery & cost ~$750,000

• Drilling Contractors should recognize the ability of these new build jack-ups to run subsea trees especially with the increased water depth capability


Subsea Trees from Jack-ups

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