dual gradient drilling
DESCRIPTION
.TRANSCRIPT
-
5/24/2018 Dual Gradient Drilling
1/481
Petroleum Engineering 411
Well Drilling
Lesson 27
Dual Gradient Drilling
-
5/24/2018 Dual Gradient Drilling
2/482
DESIGN PROJECT
Your PETE 411 Design Project will beassigned on Friday, November 16
The Project Report is Due in Dr. J-WsOffice by 5 p.m. on Monday, Dec. 3
-
5/24/2018 Dual Gradient Drilling
3/48
3
What is Dual Gradient Drilling?
(DGD)?
In dual-gradient drilling the pressureprofile in the annulus has twodistinct pressure gradients
An example would be a heavy mudbelow the mudline and a
seawater gradient above the mudline
-
5/24/2018 Dual Gradient Drilling
4/48
4AT
Conventional Riser Drilling - Wellbore Pressures
SEAFLOOR
SEA WATER
HYDROSTATIC
PRESSURE
DE
PTH
MUD HYDROSTATICBOP
FLOATER
DRILLING RISER
CHOKE LINE
-
5/24/2018 Dual Gradient Drilling
5/48
5
Static Wellbore Pressures
SEA WATER
HYDROSTATIC PRESSURE PRESSURE
MUDHYDROSTATIC
PRESSURE
SMD
MUD
HYDROSTATIC
PRESSURE
Conventional
BOP
FLOATER
RISER
CHOKE
LINE
DGD
-
5/24/2018 Dual Gradient Drilling
6/48
6
Dual Gradient Drilling Projects
Subsea Mudlift Drilling (SMD)
Hollow Glass Spheres
Deep Vision
Shell
-
5/24/2018 Dual Gradient Drilling
7/48
7
SubseaMudliftDrilling
( SMD )
Note Pump
and ReturnLine
-
5/24/2018 Dual Gradient Drilling
8/48
8
Subsea Mudlift Drilling
What is Subsea Mudlift Drilling?
How does it work?
Why do we need it? Pore pressures and fracture gradients
Mud weights and casing programs
What about connections and trips?
What about kicks?
-
5/24/2018 Dual Gradient Drilling
9/48
9
1.Riserless Drilling: Circumventing the Size/costCycle in Deepwater, by Allen D. Gault.
May 1996, Offshore, p.49
2.Subsea Mudlift Drilling JIP:Achieving dual-gradient technology,
by K.L. Smith et al., World Oil - DeepwaterTechnology, August 1999, pp 21-28.
HW #13 (due 11-2-01)
References
-
5/24/2018 Dual Gradient Drilling
10/48
10
Current SMD Concepts
A water-filled drilling riser
One or more separate small-diametermud return line(s) from seafloor tosurface (e.g., two 4.5-in ID lines)
A dual mud density system (DGD)
Seawater gradient from surface toseafloor
Heavier drilling mud inside the wellbore
-
5/24/2018 Dual Gradient Drilling
11/48
11
Current SMD Concepts - contd
A seafloor mud pump to lift mud to surface
Pressure inside wellbore at seafloor is~ the same as the pressure in the
ocean at seafloor
Theoretically the well is always deadImportant in case of drive-off
Retains a Riser Margin
-
5/24/2018 Dual Gradient Drilling
12/48
12
Current Problems
Deeper water results in longer and heavier drillingrisers
High pore pressures and low fracture pressures
lead to more casing stringsThis leads to larger wellheads, even larger andheavier risers, and finally to bigger and more
expensive rigs
Well control is more difficult - because of the porepressure / fracture pressure proximity, and long
choke lines with high friction pressure drops
-
5/24/2018 Dual Gradient Drilling
13/48
13
Effect of Increasing Water Depth
Weight of drilling riser increases
with depth. In 10,000 ft of water:
21-inch riser has an internal capacityof ~ 4,000 bbls! (value ~ $1 million)
Weight of riser ~ 2 million lbs.Weight of 16 lb/gal mud inside riser~ 2.7 million lbs
-
5/24/2018 Dual Gradient Drilling
14/48
14
What About Subsea Mudlift Drilling?
Two 4.5 ID return lines with~ 400 bbls capacity can do the job
Requires much less weight and volumefor storage!
A smaller vessel can do the job A smaller vessel can easier be upgraded
to do the job
-
5/24/2018 Dual Gradient Drilling
15/48
15ATM
SMD refers to drilling where mud returnsDO NOTgo through a conventional,large-diameter, drilling riser
Instead the returns move from the seafloorto the surface through two small -diameter pipes separate from the
drillpipe (outside the main riser pipe)
A Mudlift system is used in the Return Line
What is Subsea Mudlift Drilling?
-
5/24/2018 Dual Gradient Drilling
16/48
16
Fig. 7.21 ADE
Porepressure
gradient and
fracture
gradient datafor Jefferson
Parish, LA.
Fracture
Gradient
Pore
Pressure
Gradient
Equivalent Mud Density, ppg
0.5 ppg
0.5 ppg
-
5/24/2018 Dual Gradient Drilling
17/48
17
Pore Pressure
Frac Pressure
Max Mud Wt
Min Mud Wt
Equivalent Mud Wt, lb/gal
SEAFLOORConventional Casing Seat Selection
-
5/24/2018 Dual Gradient Drilling
18/48
18
TypicalOverburden
Pressuregrad.vs. Depth
Ref: Fracture gradient
prediction for the newgeneration, by B.A.
Eaton and T.L. Eaton.
World Oil, October1997.
17.3 ppg
11.5 ppg
-
5/24/2018 Dual Gradient Drilling
19/48
19ATM
Conventional Riser Drilling- Wellbore Pressures
SEAFLOOR
SEA WATER
HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
STATIC PRESSURE
CIRCULATING PRESSURE
PBIT
BOP
FLOATER
Drill String
-
5/24/2018 Dual Gradient Drilling
20/48
20ATM
Static Wellbore Pressures
SEAFLOOR
SEA WATERHYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD
HYDROSTATICPRESSURE
SMD
MUD
HYDROSTATICPRESSURE
Conventional
-
5/24/2018 Dual Gradient Drilling
21/48
21ATM
Example: Static Wellbore Pressures
At 30,000 ft, in 10,000 ft of water, the
pore pressure is 21,000 psig.
For conventional drilling, what is theminimum mud weight that can control thispressure?
For SMD, what is the minimum mud weightthat can control this pressure?
-
5/24/2018 Dual Gradient Drilling
22/48
22ATM
Static Wellbore Pressures
P = 0.052 * MW * Depth
For conventional drilling,Minimum mud wt.
MWmin = 21,000/(0.052 * 30,000) = 13.5 lb/gal
Seafloor pressure = 0.052*8.6*10,000 = 4,472 psig
For SMD,Minimum mud weight= (21,000 - 4,472)/(0.052 * 20,000) = 15.9 lb/gal
-
5/24/2018 Dual Gradient Drilling
23/48
23ATM
Solution: Static Wellbore Pressures
SEA WATER
HYDROSTATIC
PRESSURE
4,472 psi
DEPTH
15.1 lb/galSMD
13.9 lb/galConventional
21,000 psi
-
5/24/2018 Dual Gradient Drilling
24/48
24ATM
Wellbore Pressures
SEAFLOOR
FRACTURE
PRESSURE
PORE PRESSURE
SEA WATERHYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD
HYDROSTATICPRESSURE
Conventional
-
5/24/2018 Dual Gradient Drilling
25/48
25ATM
SEAFLOOR
FRACTURE
PRESSURE
PORE PRESSURE
MUD
HYDROSTATICPRESSURE
SMD
SEA WATERHYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD
HYDROSTATICPRESSURE
Conventional
Wellbore Pressures
-
5/24/2018 Dual Gradient Drilling
26/48
26ATM
Casing Requirements - Conventional
SEAFLOOR
FRACTURE
PRESSURE
PORE PRESSURE
SEA WATERHYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD
HYDROSTATICPRESSURE
Conventional
-
5/24/2018 Dual Gradient Drilling
27/48
27ATM
Casing Requirements - SMD
SEAFLOOR
FRACTURE
PRESSURE
PORE PRESSURE
MUD
HYDROSTATICPRESSURE
SMD
SEA WATER
HYDROSTATICPRESSURE
PRESSURE
DEPTH
-
5/24/2018 Dual Gradient Drilling
28/48
28ATM
Pressure Considerations
SEAFLOOR
FRACTURE
PRESSURE
PORE PRESSURE
MUD
HYDROSTATICPRESSURE
SMD
SEA WATER
HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD
HYDROSTATICPRESSURE
Conventional
SMD
-
5/24/2018 Dual Gradient Drilling
29/48
29ATM
Wellbore Pressures - Conventional
SEAFLOOR
SEA WATER
HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
STATIC PRESSURE
CIRCULATING PRESSURE
PBIT
BOP
FLOATER
-
5/24/2018 Dual Gradient Drilling
30/48
30ATM
Static Pressures - SMD
SEAFLOOR
SEA WATER
HYDROSTATICPRESSURE
PRESSURE
ANNULUS AND
RETURN LINE
BOP
FLOATER
-
5/24/2018 Dual Gradient Drilling
31/48
31ATM
Drillstring Circulating Pressures
SEAFLOOR
SEA WATER
HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
CONVENTIONALSMD
PBIT
-
5/24/2018 Dual Gradient Drilling
32/48
32ATM
Annulus Circulating Pressures
SEAFLOOR
SEA WATER
HYDROSTATICPRESSURE
PRESSURE
DEPTH
CONVENTIONAL (13.5 lb/gal)
SMD (15.9 lb/gal)
PPUMP
-
5/24/2018 Dual Gradient Drilling
33/48
33ATM
Circulating Pressures - SMD
SEAFLOOR
SEA WATER
HYDROSTATICPRESSURE
PRESSURE
DEPTH
ANNULUS AND RETURN LINEDRILLSTRING PRESSURE
PBIT
PPUMP
-
5/24/2018 Dual Gradient Drilling
34/48
34ATM
Circulating Pressures - Summary
DISTANCE FROM STANDPIPE
CONVENTIONAL
SMD
PBIT
PML_PUMP
-
5/24/2018 Dual Gradient Drilling
35/48
35ATM
Transient Behavior when Stopping Rig Pump
(U-tubing or Free-fall)
Why does the drillpipe fluid level fall?
How fast does the Fluid Level in thedrillpipe drop?
How far does the Fluid Level drop?
Transients
-
5/24/2018 Dual Gradient Drilling
36/48
36ATM
MUDLIFT
U-Tubing in SMD
~SEAWATER
HYDROSTATIC
PRESSURE
BOP
STATIC
FLUID
LEVEL
FLOATER
-
5/24/2018 Dual Gradient Drilling
37/48
37ATM
Static Pressures - SMD
SEAFLOOR
SEA WATER
HYDROSTATICPRESSURE
PRESSURE
DEPTH
ANNULUS AND RETURN LINEDRILLSTRING PRESSURE
-
5/24/2018 Dual Gradient Drilling
38/48
38ATM
U-Tub ing Rate vs. Time after Pump OFF
0
200
400
600
800
0 5 10 15 20 25 30
Elapsed Time, min
MudFlow
Rate,gpm 3-in ID
4.276-in ID
6-in ID
10,000 ft Water Depth
-
5/24/2018 Dual Gradient Drilling
39/48
39ATM
Fluid Level vs . Time after Pump OFF
0
1,000
2,000
3,000
4,000
5,000
0 5 10 15 20 25 30
Elapsed Time, min
FluidLevelinDrillpipe,
ft
3-in ID
4.276-in ID
6-in ID
10,000 ft Water Depth
-
5/24/2018 Dual Gradient Drilling
40/48
40
-
5/24/2018 Dual Gradient Drilling
41/48
41ATM
How do you shut a well in after taking a kick?
With a DSV this is almost routine
Better still, it is not necessary to shut the well in.The wellbore pressures can be increased bytemporarily slowing down the mudlift pump
Friction in the choke line is handled by theMudlift Pump and is not seen by theweak formations
Well Control Considerations
-
5/24/2018 Dual Gradient Drilling
42/48
42
-
5/24/2018 Dual Gradient Drilling
43/48
43
G l S
-
5/24/2018 Dual Gradient Drilling
44/48
44ATM
General Summary
Dual Gradient Drilling is a method that offerspotential for lowering drilling costs in very deepwaters:
Fewer casing stringsSmaller rigsLess time on location
The method utilizes one or more small-diameterreturn lines from the seafloor to the surface. Thedrillpipe is separate from the return lines
-
5/24/2018 Dual Gradient Drilling
45/48
45ATM
Summary - contd
A mudlift system (pump) is used to feed thereturn lines, thereby making a dual-densitymud system possible
Wellhead pressure is maintained at seawaterhydrostatic, so well is dead at all times
Well control is quite similar to that inconventional drilling with a riser, but offers anumber of significant advantages
-
5/24/2018 Dual Gradient Drilling
46/48
46ATM
THE END
-
5/24/2018 Dual Gradient Drilling
47/48
47
Gas Lift?
Glass Beads?
How to Handle
Connections?
Trips?
Pumps?
Gas Lift?
Glass Beads?
Rotating BOP
Dual Gradient
Alternatives
Advanced SMD System
-
5/24/2018 Dual Gradient Drilling
48/48
MUDLIFTBOP
Advanced SMD System
SEAFLOOR
~SEAWATER
HYDROSTATIC
PRESSURE
FLOATER
30,000
10,000
Circulation Rate 650 gpm
Drillpipe OD 6 5/8 in
Return Line ID 6 in
Hole Size 12 1/4 in