lesson 1. intro to dgd

Confidential to Subsea Mudlift Drilling JIP11/6/00 DGD Template 1 of 64

Dual Gradient Drilling Basic Technology

Dual Gradient Drilling Basic Technology

Lesson 1

Introduction to DGD

Jerome J. Schubert


IntroductionIntroduction

Current deepwater drilling problems


Introduction, con’tIntroduction, con’t

Brief history of DGD– Phase I– Phase II– Phase III


Introduction, con’tIntroduction, con’t

Describe the DGD SystemHow can DGD can solve the existing drilling

problems?Equipment overview


Current Deepwater Drilling Problems

Current Deepwater Drilling Problems

Deeper water results in longer and heavier drilling risers

High pore pressures and low fracture gradients leads to more casing strings


Land Well

2 strings of casing

after 20”


Riserless Drilling -AWater Depth = 500 feet

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500’ Water Depth



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1000’ Water Depth

2 strings of casing

after 20”



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5000’ Water Depth3 strings of casing

after 20”



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4 strings of casing

after 20”

with no kick or trip margins


0.5 ppg Standoff0.5 ppg Standoff0

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30" 26" 20" 16" 13 3/8" 113/4" 9 5/8" 7 5/8"

5 1/2" to TD

6 strings of casing

after 20”


Current Deepwater Drilling ProblemsCurrent Deepwater Drilling Problems

Too many shallow casing points– May not reach TD– No contingency casing available

This leads to larger wellheads, even larger and heavier risers, and finally to bigger and more expensive rigs



Well Control is more difficult - because of the pore pressure/fracture proximity, and long choke lines with high friction pressure drops


Kick w/ 750 psi SIP

Pore Pressure

Fracture Pressure

Mud HSP (13.1 ppg)

Mud HSP + 750 psi

Formation has fractured



Very high riser loads (current and weight)Weight of the drilling riser increases with

depth.



In 10,000’ of water– 21-inch riser has an internal capacity of ~4000

bbls! (~$1 million)– Weight of the riser itself is ~ 2million lbs– Weight of 16 ppg mud inside the riser ~ 2.7

million lbs



Water depths beyond rig fleet– New builds and major upgrades



Small wellbore at TD precludes large production tubing - limiting production rates

Began 2nd quarter of 2000


Drilling’s Major Benefits of DGD

Reduces drilling cost by $5-15 MM per well in young depositional basins (4 casing strings)

Provides contingency casing for SWF’s, sub-salt




Allows room for high rate completions

Expands capacity of existing rig fleet

Mitigates effects of high currents

Improves Well Control margin


Describe the DGD SystemDescribe the DGD System

“DGD” Drilling, in the present context, refers to drilling where mud returns DO NOT go through a conventional, large-diameter, drilling riser.

Instead the returns move from the seafloor to the surface through one or more small - diameter pipe(s) separate from the drillpipe.

A Mudlift system is used in the Return Line

A Dual Gradient mud system is achieved.


12.4 ppg mud

13.5 ppg mud

Single vs. Dual Gradient ConceptSingle vs. Dual Gradient Concept

Single Gradient Wells– Wellbore contains a

single density fluid– Single pressure

gradient Dual Gradient Well

– Wellbore feels seawater gradient to the seafloor, and mud gradient to bottom

Pressure, psi

Depth

ft

Seafloor @ 10,000’

Seawater HSP

23,880 psi

@ 37,500’


Dual Gradient Achieved by:Dual Gradient Achieved by:

Placing SRD on top of the BOP stack and diverting the mud flow from the annulus to the MLP

The MLP then pumps mud back to the rig via the return lines

Suction pressure to the MLP is maintained at Seawater HSP + ~20 to 50 psi


Dual Gradient

Heavier Mud w/ Seawater Above

Mudline

Same Bottom Hole

Pressure

SingleMud

Weight

Conventional

Single vs. Dual-Gradient Mud Systems

From the perspective of the well, there is no mud above the mudline in a dual-gradient system!

Figure 3


How can DGD can solve the existing drilling problems?How can DGD can solve the existing drilling problems?

By placing the MLP on the seafloor we can reduce the pressure exerted on the shallow weak formations and still maintain the required pressure at the bottom of the hole to control formation pressure

Riser margin is back - emergency disconnect and drive-off will not result in an automatic kick.


Pore and Fracture GradientsPore and Fracture Gradients0

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Dual Density: Pore Gradient Fracture Gradient

Conventional: Pore Gradient Fracture Gradient


Graphical Casing Seat Selection - Dual Density

Graphical Casing Seat Selection - Dual Density

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0.5 ppg trip and kick margin1.0 ppg trip and kick margin

11 3/4"

13 3/8"

16"

20"


Dynamic Casing Seat SelectionDynamic Casing Seat Selection

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Pressure, psi

1.0 ppg kick

0 bbl influx volume

Frac. Press.

Pore Press.


Dynamic Casing Seat SelectionDynamic Casing Seat Selection

1.0 ppg kick

50 bbl influx volume

Frac. Press.

Pore Press.


1.0 ppg kick, 50 bbl influx

Kick Tolerance is Back

20” @ 12,500’

16” @ 14,000’

13 3/8” @ 17,000’

11 3/4” @ 22,800’

9 5/8” @ TD

DGDConventional

20” @ 12,500’

16” @ 13,000’

13 3/8” @ 14,000’

11 3/4” @ 15,000’

9 5/8” @ 17,500’

7 5/8” @20,000’

5 1/2 “ @ TD

0.5 ppg standoff

no influx


Equipment overviewEquipment overview

Marine RiserSRD - SubSea Rotating DiverterDSV - Drillstring ValveMLP - MudLift PumpReturn LinesManifoldingDual Trip Tanks


Wellhead and BOP

Return Line

Drillpipe

Rotating Diverter

BHADrill String Valve

Mud Return and Pump

Seawater-Driven MudLift Pump

Seawater Filled Marine Riser

SubSea MudLift ConfigurationSubSea MudLift Configuration

Seawater Power Line,Control Umbilicals

Seawater Pumps(Existing Mud Pumps)


Marine RiserMarine Riser

Essentially a conventional riser filled with seawater


Wellbore ComponentsWellbore Components

Subsea RotatingDiverter (SRD)

Return Outlets

RiserAdapter


Drill String Valve (DSV)Drill String Valve (DSV)

Flow Nozzle

Closing Spring

Seawater Driven MudLift PumpMud Enters the

Diaphragm Pumps

Mud Inlet

Seawater Pumped from the

Rig

Displacing the Mud Back to the

Rig

Mud Outlet

While Seawater Discharged to

Sea


Stroke Indicator Sensor (Fixed)

Hydraulic Fluid In/Out

Mud In/Out

Diaphragm

Stroke Indicator Magnet Assembly

Stroke Indicator Tube (Moving)

Connection to Diaphragm

Diaphragm PumpDiaphragm Pump


Seawater Driven MudLift SystemSeawater Driven MudLift System

14’ x 17’ x 11’h175,000 lbs

plusSeawater Conduit

MudROV-Style

Cables

B

C K

HSeawater


Return LinesManifolding

Seawater Trip TankMud Trip Tank

Return LinesManifolding

Seawater Trip TankMud Trip Tank


The EndThe EndThe EndThe End

Jerome J. Schubert

Introduction to DGD

lesson 1. intro to dgd

Documents

dgd system dgd drilling

drilling cost

water depthriserless

existing drilling problems

dgd jerome

land wellriserless drilling

mudlift system

schubert11600 confidential