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Well Control When Drilling With a Partly-Evacuated Marine Drilling Riser
LRRS
CTOBørre Fossli (ORS)
Dual Gradient Workshop, Houston May 5, 2011
- 2 -
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
- 3 -
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20000
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Gradient (ppg)
Dep
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t TVD
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Frac_DataPore_data
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Pressure (psi)
Dep
th (f
t TVD
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Frac_DataPore_data
Case 1 GoM: Conventional Drilling
LOSS
KICK
- 4 -
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Case 1 GoM: Drilling with LRRS
Mud Weight: 17.2 ppg
- 5 -
0
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Dep
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0 5000 10000 15000Pressure (psi)
Dep
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Pore_dataFrac_dataLRRS
Case 2 Macondo: Drilling with LRRS
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8 10 12 14 16Gradient (ppg)
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0 5000 10000 15000Pressure (psi)
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Case 2 Macondo: LRRS Improves Margins
11000
12000
13000
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12,1 12,2 12,3 12,4 1
Margin Improvements
Margin Improvements
- 7 -
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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8 10 12 14 16Gradient (ppg)
- 8 -
Conventional Barrier Diagram
Primary barrier elements: Mud
– Riser integrity
Secondary barrier elements: BOP
Common barrier elements Wellhead & seal assemblies Casing & cement
- 9 -
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
- 10 -
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
]
4000
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800 PMPDLRRS
Frac
Pore
Conv
20″
13 3/8″
9 5/8″
NCS (200mWD)
- 11 -
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
- 12 -
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
- 13 -
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