confidential to subsea mudlift drilling jip11/06/00dgd template 1 of 42 dual gradient drilling basic...

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

Dual Gradient Drilling Basic Technology

Dual Gradient Drilling Basic Technology

Lesson 2

Key Success Factors in DGD

Jerome J. Schubert

Hans C. Juvkam-Wold


IntroductionIntroduction

Success Factors in EquipmentSuccess Factors in Drilling OperationsSuccess Factors in Well Control


Success Factors in EquipmentSuccess Factors in Equipment

RiserReturn lineAchieving dual densityCuttings processing unit Isolation of mud from seawaterManaging the u-tube


RiserRiser

No RiserConventional RiserOther

– Phantom riser– Super straw– Cork/Snapper– Holy riser– Top drum/tulip


Return lineReturn line

RiserFree standingChoke & Kill lineBoost lineSeparate return line


Achieving dual densityAchieving dual density

Gas liftGlass beadsWater-jet pumpCentrifugal pumpPositive displacement pump


Positive displacement pumpsPositive displacement pumps

Progressive cavity pumpsReciprocating Piston or Plunger pumpsDiaphragm pumps


Diaphragm pumpsDiaphragm pumps

Constant discharge rateHigh efficiencyLarge volume displacementGood HP ratingLow pressure surgesCan handle mud, gas, and solids


Pump Design CriteriaPump Design Criteria

Maximum output GPMMaximum output HPMaximum pressureMaximum mud density


Pump ControlsPump Controls

Match subsea pump rate with surface pump rate

Automatic pump operation vs. manual controls

Reaction time for start, stop, change in rateSubsea seawater pressure sensorSubsea mud reservoir level sensor


Pump RedundancyPump Redundancy

What can be done if one or more of the pump chambers fails?


Pump powerPump power

Hydraulic power– Electric motors to run hydraulic pumps– Hydraulic fluid pumped from the surface


Solids processing unitSolids processing unit

System must handle solids in some wayPump okHow about plugging choke/kill and return

lines?


Isolation of mud from seawaterIsolation of mud from seawater

How do we separate mud in the annulus from the seawater either in the riser or open ocean?

SRDPressure ratingActive for tripping, running casing, logging,

etc.


Managing the u-tubeManaging the u-tube

How will we handle the u-tube?Write all procedures compensate for the

active u-tube?Build a DSV to manage it?


DSV design factorsDSV design factors

How is it going to open and close?Will it have an adjustable opening pressure?Will it pass MWD signals and LCM?What will it do to circulating pressures?Are the opening and circulating pressure

repeatable?Where will it be located in the drillstring?


Success Factors in Drilling OperationsSuccess Factors in Drilling Operations

Lower riser loadsLower deck loadsLower deck space requirementsDrill to TD with fewer casing strings


Success Factors in Drilling OperationsSuccess Factors in Drilling Operations

Balanced Cement Plug Running Casing Cementing Check for

Underbalance Circulation Connections

Dual to Single Density Conversion

Routine Drilling Start-Stop Circulation Tripping Unplanned Shutdown Fishing Logging


What a Dual Gradient Drilling System Must Be Able To Do For Effective Well Control

ATM


OutlineOutline

Understanding DGD Well Control - what is different ?

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?


Understanding WC in DGDUnderstanding WC in DGD

Accept that DGD Well Control is not a simple task - it is different - and it is frequently neither 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 . . .

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

PUMP

U-Tubing in DGD

~SEAWATER HYDROSTATIC

PRESSURE

BOP

STATIC FLUID LEVEL

FLOATER

Even with a DSV there isstill a potential U-tube


OutlineOutline

How can we educate ourselves and develop a detailed understanding?


How can we Educate Ourselves?How can we Educate Ourselves?

We have found that detailed hydraulics modeling 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 operations

Procedures are critically peer reviewed and tested against the hydraulics model


OutlineOutline

What must an effective DGD well control system be able to accomplish?


WC System must be able to:WC System must be able to:

Avoid kicks - as far as possible

Detect Kicks early - to minimize their size

Determine kick size and Intensity

Measure new formation pressure (“SI-BHP”)

Safely remove kick from hole

Maintain constant BHP

Detect equipment failures during WC operations

Provide contingencies for all potential failures


Avoiding KicksAvoiding Kicks

Recognize the signs of increasing pore pressure? How?

Allow the recovery of cuttings of sufficient size to evaluate their characteristic shape and other properties?

Allow you to maintain satisfactory BHP during connections? While tripping?When cementing? When power fails?


Detecting Kicks EarlyDetecting Kicks Early

Can you perform a conventional flow check?

How accurate is your pit gain indicator?

What other kick detection methods are available?

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 that its effects are not confused with kick indicators?


PUMPBOP

Dual Gradient Drilling System

SEAFLOOR


PRESSURE

FLOATER

KICK

Surface PumpSeafloor Pump

How are yougoing to handle

this kick?


Determining Kick SizeDetermining Kick Size

What is the initial size of the kick when its presence is first confirmed?

What is the size of the kick when influx stops?

How can you measure kick volume and intensity?

How can you maintain constant BHP- while circulating the kick out of the hole?- if you can’t circulate and kick is migrating?

What is the Expected Kick Fluid Behavior?


Gas Kick BehaviorGas Kick Behavior

As the gas kick moves up the hole the pressure generally decreases so we would expect the gas volume to expand - but how fast?

At the seafloor pump there is an increase in pressure - 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!


OutlineOutline

What must an effective DGD system contain? - Essential Equipment?


Which DGD System?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?


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?

Coordination between the pumps?- Instrumentation

Or gas or bead

injector


In Summary ...In Summary ...

What are the Key Factors that will

ensure safe and efficient DGD

Drilling and Well Control?


Key Success Factors for Well Control in DGD?

Key Success Factors for 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


Key Success Factors - cont’dKey Success Factors - cont’d

Manage the “U-tube”

Detect and Manage Trapped Pressure

Use Driller’s Method

Perform Volumetric Well Control

Manage Kick Expansion (pump very slowly)

Manage Loss of Pumping Capability

Understand the Behavior of Gas Kicks


Additional Success Factors Additional Success Factors

Tripping

Logging

Running Casing

Cementing Casing

Setting Cement Plugs, etc.

Handle Non-water Based Drilling Fluids…


The EndThe EndThe EndThe End

Jerome J. Schubert

Hans C. Juvkam-Wold

Key Success Factors in DGD

confidential to subsea mudlift drilling jip11/06/00dgd template 1 of 42 dual gradient drilling basic...

Documents