Deepwater MPD / PMCD
August 21, 2011
• Managed Pressure Drilling (MPD)
– Pressure held on top of riser while drilling.
– Drill in overbalance condition
• Pressurized Mud Cap Drilling (PMCD)
– Pressure of mud column in riser and wellbore plus surface maintained pressure should equal formation pressure at top of carbonates.
– Drill in at balance condition
MPD Objectives - GSF Explorer
• Prevent gas entering riser.• Improved riser degassing capabilities.• Early kick and loss detection and automated reaction to
these events.• Allows Pressurized Mud Cap Drilling (PMCD) to be
conducted safely.• Ability to quickly manipulate the pressures (up or down)
within the wellbore without the need for mud weight up and circulation.
• Plan to drill in MPD mode for kick detection for drilling hole section above carbonates.
– Drill overbalanced with RCD bearing installed and maintain surface applied pressure on the well.
– Pressure on welll maintained by circulating through secure manifold choke.
– Improved kick detection
MPD - PMCD Switch Application
MPD to be used in overbalance mode until the losses in the carbonates become excessive thereafter the system will be changed over to a PMCD (pressurized mud cap drilling) arrangement.
Will use PMCD while drilling carbonates while experiencing severe fluid losses
– Avoid floating mud cap drilling
– Accurate determination of formation pressures
– Maintain well fluid level at surface
GSF Explorer MPD Equipment Requirements
• Rotating Control Device (RCD)• 21 ¼” 2k Riser Annular BOP• Riser Flow Spool • Drilling Choke Manifold (Secure)• Buffer Manifold• Two Phase Separator• Coriolis flow meter• Drill String Floats - Plunger Type (connections –
stripping in/out)
Approx. 2000 meters of riser between flow
spool and BOP
General Arrangement MPD Configuration
Secure Manifold – Two Phase Separator
Inline Coriolis Flow Meter
Sequential Operations – MPD to PMCDStart MPD operations with overbalanced fluid
Drill ahead MPD mode encounter carbonates with acceptable losses
Annular
Kill line filled with base oilprior to drilling ahead
Close Annular BOP
Determine reservoir pressure = fracture pressure of carbonates using kill line
Lighten riser fluid till it is just < top fracture pressure
Take significant losses in carbonates
Continue drilling down drill string in PMCD mode with seawater
Kill Line Choke Line
Pump down annulus periodically to keep it gas free (bullhead to the top fracture)
RCD
Pressure mud column below BOP plus kill line hydrostatic
MPD Operations
GSF Explorer
Ability to stay within a narrow drilling windows (Pore vs. Frac.) .
Mitigate against losses:- early warning and ability to react quickly by decreasing back pressure.
Safe means to drill section :- Increased kick detection sensitivity and reaction.
Back pressure can be used to quicklysupplement drilling fluid density when required if an influx is detected
With MPD maintain CBHP
PMCD Operations
GSF Explorer
•Annulus mud weight/press < pore pressure.
•Annulus fluid level at surface – casing pressure.
•Pressure monitored at MPD manifold.
•SBM will minimize gas migration as it goes into solution.
•Pump down riser boost with original weight mud
•Pump down drill string with seawater.
Constant Bottom Hole Pressure - Example
Drilling Window
FRACTURE PRESSURE
12.4 ppg
PORE PRESSURE
11.5 ppg
Static Mud Weight
11.5 ppg
Pumps OnAnnular Friction
Loss0.25 ppg
RPM FrictionIncrease0.09 ppg
Surface Back Pressure0.41 ppg
Bottom hole Pressure Stays The
Same
12.25 ppg
Make a Connection riser Boost Pump ON
Stop RPM
Stop Pumps
MPD & PMCD Carbonate Section
• Drill below the 11-7/8” shoe prior to entering the carbonate section. To be drilled in MPD Mode.
• Carbonates are anticipated to be vugular and/or fractured and may lead to severe/total losses with no returns.
• Depending on the loss rate > 20% PMCD will commence.
• There may be further losses as the pore pressure decreases (in PMCD mode) as the carbonates are drilled deeper.
4300m brt
Shale
Silt/Sand
Carbonate
Sand / Shale /Coal
Choke Line
Riser Boost Line
Kill Line
MPD Drilling into Carbonates
losses> 20%Close in (annular BOP) open kill
line to base oil and record pressure
Kill line Pressure
Drilling in MPD mode
Kill line pre-filled with treated
base fluid
Kill line pressure to balance pore
pressure in carbonates
Carbonate section below 11 7/8”shoe
Potential for gas in Carbonate section in
the Fractures &
Vugs
4300m brt
Shale
Silt/Sand
Carbonate
Sand / Shale /Coal
Choke Line
Riser Boost Line
Kill Line
150100 200
50 250
300
150100 200
50 250
300
Calculate lighter mud in riser to give +/- 300 - 500 psi surface
annular back pressure displace into well
Light mud to Riser
annulus via boost.
Pump seawater down string establish stable injectivity at
drilling rate
4300m brt
Shale
Silt/Sand
Carbonate
Sand / Shale /Coal
Choke Line
Riser Boost Line
Kill Line
150100 200
50 250
300
150100 200
50 250
300
Annulus Pressure at MPD Choke
Kill Line Pressure
Drill ahead w/seawater down string, Bullhead +/- 20bbls original weight
mud down riser boost annulus every hour.
Seawater carries
cuttings into loss zone
Periodic pumping to
annulus maintains it hydrocarbon free – pump in at BOP
4300m brt
Shale
Silt/Sand
Carbonate
Sand / Shale /Coal
Choke Line
Riser Boost Line
Kill Line
150100 200
50 250
300
150100 200
50 250
300
Annulus Pressure at MPD Choke
Drill ahead w/ seawater, further loss zone encountered. Shut in and assess
pressures using kill line.
Possibility of X flow
between loss zones
Drop in surface annular
pressureLighter Riser mud stays in
the riser annulus
New loss zone at lower
pressure
Monitor Surface annular
pressure
PMCD
• During PMCD the pore pressure may start to decrease this will be noticed by a drop in surface annular pressure.
• Shut in well on upper BOP annular & open annulus again to base fluid in the kill line & recalculate new pore pressure.
• Evaluate whether to change out the riser to lighter mud or to pump more lighter mud below BOP.
Drill ahead PCWD Cuttings plugging off loss zone. Pressure increase in
annulus & DP
Indications an increase in Pump
pressure and annular pressure
Cuttings plugging off the loss zone/s
Control OptionsDepending on pressures involved:•Increase pressure to induce losses•Revert to MPD drilling
PMCD
• Should the pump pressure and the surface annular pressure rise together, this is indicative of the loss zone starting to heal over.
• Depending on the pressures seen.
– Induce further fractures and continue in PMCD mode
– Return to MPD mode.