Well Control When Drilling With a Partly-Evacuated Marine Drilling Riser

LRRS

CTOBørre Fossli (ORS)

Dual Gradient Workshop, Houston May 5, 2011

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Applicability of LRRS

New well control procedures needed when drilling Intermediate sections (Overburdon)

Mud Weight

LRRS +

LRRS ECD

FG

PPG

Depth

Conventional well Control

New Well Control Priciples

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Frac_DataPore_data

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Case 1 GoM: Conventional Drilling

LOSS

KICK

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Case 1 GoM: Drilling with LRRS

Mud Weight: 17.2 ppg

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Case 2 Macondo: Drilling with LRRS

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Case 2 Macondo: LRRS Improves Margins

11000

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12,1 12,2 12,3 12,4 1

Margin Improvements

Margin Improvements

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Case 2 Macondo: Riser Margins with LRRS

Casing/liner Conventional LRRS @ 1700 ftMud

Weight [ppg]

Riser Margin

Mud Weigh

t [ppg]

Riser Margin

22” Casing 9.6 Yes* 12.6 Yes18” Liner 10.1 No 12.8 Yes 16” Liner 11.1 No 14.0 Yes 13 5/8” Casing 12.3 No 14.5 Yes 11 7/8” Liner 13.3 No 15.7 Yes 9 7/8” Liner 14.0 No 16.2 Yes 7”x 9 7/8” casing 14.2 No 15.8 No*

* A riser margin possible in 8 ½” section if 9 5/8” had been set 2000’ deeper, as planned.

*Pump & dump procedure

0

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Conventional Barrier Diagram

Primary barrier elements: Mud

– Riser integrity

Secondary barrier elements: BOP

Common barrier elements Wellhead & seal assemblies Casing & cement

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Barrier Elements LRRS+

Primary barrier elements: Mud

– Level measurement

Secondary barrier elements: BOP

– Casing & Cement– Wellhead & seal assemblies

Common barrier elements Wellhead & seal assemblies*

* Well and water depth spesific

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Avoiding Common Barriers with LRRS

9 5/8″ and 13 3/8″ csg common barriers

Conventional:Intersects at 2000 mMD

Pressurized MPD:Intersects at 2300 mMD

LRRS:Independent barriers entire section

MW [sg]1.0 1.2 1.4 1.6 1.8 2.0 2.2

Refr. Gullfaks C-06

Dep

th [m

MD

]

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3800 PMPDLRRS

Frac

Pore

Conv

20″

13 3/8″

9 5/8″

NCS (200mWD)

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Improved Kick/Loss Control with LRRS

Improved kick/loss detection– Pumps as improved kick indicator– Flowmeter backup– Riser as trip tank

Primary barrier re-establish by changing level

Less danger w/gas above subsea BOP

New Procedures & Priciples

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Modified Drillers Method for LRRS +

1. Close subsea BOP– & open choke line

2. Circulate at constant DPP:– via subsea choke

3. Gas separated from liquid in riser– No gas or pressure in pump

system

Advantages:– Reduced choke-line friction

– No pressure on the rig or riser

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Conclusions

LRRS + used to drill overburden– Reservoir LRRSECD

… applicable for all drilling-related operations– Drilling – Casing operations & Cementing– Completion operations (sand control)– Workover

…results in improved well control– Bigger margins - Mud weight fits drilling window– Riser margin possible for most cases– Improved well integrity – Improved kick/loss detection– Well control equal to or better than conventional