lesson 2. key success factors
TRANSCRIPT
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Dual Gradient Drilling Basic Technology
Lesson 2Key Success Factors in DGD
Jerome J. SchubertHans C. Juvkam-Wold
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Introduction
Success Factors in EquipmentSuccess Factors in Drilling OperationsSuccess Factors in Well Control
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Success Factors in Equipment
Riser Return lineAchieving dual densityCuttings processing unitIsolation of mud from seawater Managing the u-tube
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Riser
No Riser Conventional Riser Other Phantom riser Super straw Cork/Snapper Holy riser Top drum/tulip
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Return line
Riser Free standingChoke & Kill lineBoost lineSeparate return line
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Achieving dual density
Gas liftGlass beadsWater-jet pumpCentrifugal pumpPositive displacement pump
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Positive displacement pumps
Progressive cavity pumpsReciprocating Piston or Plunger pumpsDiaphragm pumps
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Diaphragm pumps
Constant discharge rateHigh efficiencyLarge volume displacementGood HP ratingLow pressure surgesCan handle mud, gas, and solids
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Pump Design Criteria
Maximum output GPMMaximum output HPMaximum pressureMaximum mud density
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Pump Controls
Match subsea pump rate with surface pumprate
Automatic pump operation vs. manualcontrolsReaction time for start, stop, change in rate
Subsea seawater pressure sensor Subsea mud reservoir level sensor
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Pump Redundancy
What can be done if one or more of the pumpchambers fails?
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Pump power
Hydraulic power Electric motors to run hydraulic pumps
Hydraulic fluid pumped from the surface
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Solids processing unit
System must handle solids in some wayPump okHow about plugging choke/kill and returnlines?
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Isolation of mud from seawater
How do we separate mud in the annulus fromthe seawater either in the riser or open
ocean?SRDPressure rating
Active for tripping, running casing, logging,etc.
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Managing the u-tube
How will we handle the u-tube?Write all procedures compensate for theactive u-tube?Build a DSV to manage it?
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Success Factors inDrilling Operations
Lower riser loadsLower deck loadsLower deck space requirementsDrill to TD with fewer casing strings
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Success Factors inDrilling Operations
Balanced Cement PlugRunning Casing
CementingCheck for Underbalance
CirculationConnections
Dual to Single DensityConversion
Routine DrillingStart-Stop CirculationTripping
Unplanned ShutdownFishing
Logging
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What a Dual Gradient Drilling System MustBe Able To Do For Effective Well Control
AT M
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Outline
Understanding DGD Well Control - what isdifferent ?
How can we educate ourselves and
develop a detailed understanding?What must an effective DGD well control
system be able to accomplish?
What must an effective DGD system contain?
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Understanding WC in DGD
Accept that DGD Well Control is not a simpletask - it is different - and it is frequentlyneither intuitive nor obvious
for example U-tubing- how does it affect kick detection?- how can we ensure that a constant bottom-
hole pressure is being maintained?- what if power fails during WC operations?
More details later . . .
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PUMP
U-Tubing in DGD
~SEAWATERHYDROSTATIC
PRESSURE
BOP
STATICFLUID
LEVEL
FLOATER
Even with a DSV there isstill a potential U-tube
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Outline
How can we educate ourselves anddevelop a detailed understanding?
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How can we Educate Ourselves?
We have found that detailed hydraulicsmodeling is essential to understanding DGD
Study each aspect of the process in detail:- Four PhD and seven MS studies have been
completed or are in progress at Texas A&M!
Detailed procedures had to be developed to
cover all essential drilling and WC operationsProcedures are critically peer reviewed and
tested against the hydraulics model
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Outline
What must an effective DGD well controlsystem be able to accomplish?
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WC System must be able to:
Avoid kicks - as far as possibleDetect Kicks early - to minimize their size
Determine kick size and Intensity
Measure new formation pressure (SI -BHP)
Safely remove kick from hole
Maintain constant BHPDetect equipment failures during WC operations
Provide contingencies for all potential failures
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Avoiding Kicks
Recognize the signs of increasing porepressure? How?
Allow the recovery of cuttings of sufficientsize to evaluate their characteristicshape and other properties?
Allow you to maintain satisfactory BHPduring connections? While tripping?When cementing? When power fails?
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Detecting Kicks Early
Can you perform a conventional flow check?
How accurate is your pit gain indicator?
What other kick detection methods areavailable?
What is the smallest kick that can detect?
How quickly can you stop the influx? How?
How do you handle the U-tube to ensure thatits effects are not confused with kickindicators?
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PUMPBOP
Dual Gradient Drilling System
SEAFLOOR
~SEAWATERHYDROSTATIC
PRESSURE
FLOATER
KICK
Surface PumpSeafloor Pump
How are you
going to handlethis kick?
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Determining Kick Size
What is the initial size of the kick when itspresence is first confirmed?
What is the size of the kick when influx stops?
How can you measure kick volume andintensity?
How can you maintain constant BHP- while circulating the kick out of the hole?- if you cant circulate and kick is migrating?
What is the Expected Kick Fluid Behavior?
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Gas Kick Behavior
As the gas kick moves up the hole the pressuregenerally decreases so we would expect thegas volume to expand - but how fast?
At the seafloor pump there is an increase inpressure - how does the volume behave?
Can we continue to assume that PV = const?Or should we use PV = ZnRT?
We will take a closer look!
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Outline
What must an effective DGD systemcontain? - Essential Equipment?
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Which DGD System?
There are basically two different methods we can use to
Reduce annulus pressure at seafloor:
Install pump at seafloor Inject a low density fluid in the return line
Gas (e.g. air or nitrogen)
Low density particles (e.g. hollow spheres)
Can we maintain safe well controlwith all of these methods?
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Seafloor PumpBOP
Dual Gradient Drilling System
SEAFLOOR
~SEAWATERHYDROSTATIC
PRESSURE
FLOATER
KICK
Surface PumpTrip Tank(s)Mud Tanks, etc
Seafloor Pump- Power Transmission- Sensors- Controls
Seafloor Choke?- Backup?
Coordinationbetween the pumps?- Instrumentation
Or gas orbead
injector
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In Summary ...
What are the Key Factors that will
ensure safe and efficient DGD
Drilling and Well Control?
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Key Success Factorsfor Well Control in DGD?
Kick Detection
Kick Containment (stop flow into well)
Kick Removal (circulate kick out of hole?)
Determine New Pore Pressure (after kick)
Increase Mud Weight in hole (if necessary)
Perform Leak-off Test
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Key Success Factors - contd
Manage the U -tube
Detect and Manage Trapped Pressure
Use Drillers Method Perform Volumetric Well Control
Manage Kick Expansion (pump very slowly)
Manage Loss of Pumping Capability
Understand the Behavior of Gas Kicks
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Additional Success Factors
Tripping
Logging
Running Casing
Cementing Casing
Setting Cement Plugs, etc.
Handle Non- water Based Drilling Fluids
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The End
Jerome J. SchubertHans C. Juvkam-Wold
Key Success Factors in DGD