Lesson 2. Key Success Factors

7/31/2019 Lesson 2. Key Success Factors

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Confidential to Subsea Mudlift Drilling JIP11/06/00 DGD Template 1 of 42

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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Confidential to Subsea Mudlift Drilling JIP11/06/00 DGD Template 22 of 42AT M

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


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


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

Lesson 2. Key Success Factors

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