27 dual gradient drilling
TRANSCRIPT
![Page 1: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/1.jpg)
1
Petroleum Engineering 411Well Drilling
Lesson 27Dual Gradient Drilling
![Page 2: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/2.jpg)
2
DESIGN PROJECTDESIGN PROJECT
Your PETE 411 Design Project will be assigned on Friday, November 15
The Project Report is Due in Dr. J-W’s Office by 5 p.m. on Monday, Dec. 9
![Page 3: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/3.jpg)
3
What is Dual Gradient Drilling?What is Dual Gradient Drilling?(DGD)?(DGD)?
� In dual-gradient drilling the pressure profile in the annulus appears to have two distinct pressure gradients
� An example would be a heavy mud below the mudline and a seawater gradient above the mud line
![Page 4: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/4.jpg)
4AT
Conventional Riser Drilling- Wellbore Pressures
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
DEP
TH
MUD HYDROSTATIC BOP
FLOATER
DRILLING RISER
CHOKE LINE
![Page 5: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/5.jpg)
5
Static Wellbore Pressures
SEA WATER HYDROSTATIC
PRESSUREPRESSURE
DEP
TH
MUD HYDROSTATIC
PRESSURE DGD
MUD HYDROSTATIC
PRESSURE Conventional
BOP
FLOATER
RISER
CHOKE LINE
DGD
![Page 6: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/6.jpg)
6
Dual Gradient Drilling ProjectsDual Gradient Drilling Projects
� Subsea Mudlift Drilling (SMD)
� Hollow Glass Spheres
� Deep Vision
� Shell
� Gas Lift
� H.P. Riser
![Page 7: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/7.jpg)
7
Subsea MudliftDrilling
( SMD )
Note Pump and Return
Line
![Page 8: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/8.jpg)
8
Subsea Mudlift Drilling
■ What is Subsea Mudlift Drilling?■ How does it work?■ Why do we need it?■ Pore pressures and fracture pressures■ Mud weights and casing programs■ What about connections and trips?■ What about kicks?
![Page 9: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/9.jpg)
9
1. “Riserless Drilling: Circumventing the Size/cost Cycle 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 - Deepwater Technology, August 1999, pp 21-28.
HW #15 (due 11-15-01)
References
![Page 10: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/10.jpg)
10
Current SMD Concepts
■ A water-filled drilling riser■ One or more separate small-diameter
mud return line(s) from seafloor to surface (e.g., two 4.5-in ID lines)
■ A “dual mud density” system (DGD)■ Seawater gradient from surface to
seafloor■ Heavier drilling mud inside the wellbore
![Page 11: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/11.jpg)
11
Current SMD Concepts - cont’d
■ 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 dead
� Important in case of drive-off
� Retains a Riser Margin
![Page 12: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/12.jpg)
12
Current ProblemsDeeper water results in longer, larger diameter and
heavier drilling risers
High pore pressures and low fracture pressures lead to more casing strings
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 pressure proximity, and long
choke lines with high friction pressure drops
![Page 13: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/13.jpg)
13
Effect of Increasing Water Depth
Weight of drilling riser increaseswith depth. In 10,000 ft of water:
– 21-inch riser has an internal capacity of ~ 4,000 bbls! (value ~ $1 million)
– Weight of riser ~ 2 million lbs. Weight of 16 lb/gal mud inside riser ~ 2.7 million lbs
![Page 14: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/14.jpg)
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 volume for storage!
■ A smaller vessel can do the job■ A smaller vessel can easier be upgraded
to do the job
![Page 15: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/15.jpg)
15ATM
g SMD refers to drilling where mud returns DO NOT go through a conventional, large-diameter, drilling riser
g Instead the returns move from the seafloor to the surface through two small -diameter pipes separate from the drillpipe (outside the main riser pipe)
g A Mudlift system is used in the Return Line
What is Subsea Mudlift Drilling?
![Page 16: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/16.jpg)
16
Fig. 7.21 ADE
Pore pressure
gradient and fracture
gradient data for Jefferson Parish, LA.
Fracture Gradient
Pore Pressure Gradient
Equivalent Mud Density, ppg
0.5 ppg
0.5 ppg
![Page 17: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/17.jpg)
17
Pore Pressure
Frac Pressure
Max Mud Wt
Min Mud Wt
Equivalent Mud Wt, lb/gal
SEAFLOORConventional Casing Seat Selection
![Page 18: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/18.jpg)
18
Typical Overburden
Pressure grad.vs. Depth
Ref: “Fracture gradient prediction for the new generation,” by B.A. Eaton and T.L. Eaton. World Oil, October 1997.
17.3 ppg
11.5 ppg
![Page 19: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/19.jpg)
19ATM
Conventional Riser Drilling- Wellbore Pressures
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEP
THSTATIC PRESSURE
CIRCULATING PRESSURE
∆∆∆∆PBIT
BOP
FLOATER
Drill String
![Page 20: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/20.jpg)
20ATM
Static Wellbore Pressures
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD HYDROSTATIC
PRESSURE SMD
MUD HYDROSTATIC
PRESSURE Conventional
![Page 21: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/21.jpg)
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 the minimum mud weight that can control this pressure?
For SMD, what is the minimum mud weight that can control this pressure?
![Page 22: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/22.jpg)
22ATM
Static Wellbore Pressures
P = 0.052 * MW * DepthFor 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
![Page 23: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/23.jpg)
23ATM
Solution: Static Wellbore Pressures
SEA WATER HYDROSTATIC
PRESSURE
8.6 lb/gal
4,472 psi
DEPTH
15.9 lb/gal SMD
13.5 lb/gal Conventional
21,000 psi
![Page 24: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/24.jpg)
24ATM
Wellbore Pressures
SEAFLOOR
FRACTURE PRESSURE
PORE PRESSURE
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD HYDROSTATIC
PRESSURE Conventional
![Page 25: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/25.jpg)
25ATM
SEAFLOOR
FRACTURE PRESSURE
PORE PRESSURE
MUD HYDROSTATIC
PRESSURE
SMD
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD HYDROSTATIC
PRESSURE Conventional
Wellbore Pressures
![Page 26: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/26.jpg)
26ATM
Casing Requirements - Conventional
SEAFLOOR
FRACTURE PRESSURE
PORE PRESSURE
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD HYDROSTATIC
PRESSURE Conventional
![Page 27: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/27.jpg)
27ATM
Casing Requirements - SMD
SEAFLOOR
FRACTURE PRESSURE
PORE PRESSURE
MUD HYDROSTATIC
PRESSURE SMD
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
![Page 28: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/28.jpg)
28ATM
Pressure Considerations
SEAFLOOR
FRACTURE PRESSURE
PORE PRESSURE
MUD HYDROSTATIC
PRESSURE SMD
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
MUD HYDROSTATIC
PRESSURE Conventional
SMD
![Page 29: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/29.jpg)
29ATM
Wellbore Pressures - Conventional
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEP
TH
STATIC PRESSURE
CIRCULATING PRESSURE
∆∆∆∆PBIT
BOP
FLOATER
![Page 30: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/30.jpg)
30ATM
Static Pressures - SMD
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEP
TH
ANNULUS AND RETURN LINE
BOP
FLOATER
![Page 31: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/31.jpg)
31ATM
Drillstring Circulating Pressures
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
CONVENTIONALSMD
∆∆∆∆PBIT
![Page 32: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/32.jpg)
32ATM
Annulus Circulating Pressures
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
CONVENTIONAL (13.5 lb/gal)
SMD (15.9 lb/gal)
∆∆∆∆PPUMP
![Page 33: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/33.jpg)
33ATM
Circulating Pressures - SMD
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
ANNULUS AND RETURN LINE
DRILLSTRING PRESSURE
∆∆∆∆PBIT
∆∆∆∆PPUMP
![Page 34: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/34.jpg)
34ATM
Circulating Pressures - SummaryPR
ESSU
RE
DISTANCE FROM STANDPIPE
CONVENTIONAL
SMD
∆∆∆∆PBIT
∆∆∆∆PML_PUMP
![Page 35: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/35.jpg)
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 the
drillpipe drop?● How far does the Fluid Level drop?
Transients
![Page 36: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/36.jpg)
36ATM
MUDLIFT
U-Tubing in SMD
~SEAWATER HYDROSTATIC
PRESSURE
BOP
STATIC FLUID LEVEL
FLOATER
Dril
lstr
ing
Ann
ulus
![Page 37: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/37.jpg)
37ATM
Static Pressures - SMD
SEAFLOOR
SEA WATER HYDROSTATIC
PRESSURE
PRESSURE
DEPTH
ANNULUS AND RETURN LINE DRILLSTRING PRESSURE
Static Fluid Level in DP
![Page 38: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/38.jpg)
38ATM
U-Tubing Rate vs. Time after Pump OFF
0
200
400
600
800
0 5 10 15 20 25 30
Elapsed Time, min
Mud
Flo
w R
ate,
gpm
3-in ID 4.276-in ID6-in ID
10,000 ft Water Depth
![Page 39: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/39.jpg)
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
Flui
d Le
vel i
n Dr
illpi
pe,
ft
3-in ID 4.276-in ID6-in ID
10,000 ft Water Depth
![Page 40: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/40.jpg)
40
![Page 41: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/41.jpg)
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 by temporarily slowing down the mudlift pump
◆ Friction in the choke line is handled by the Mudlift Pump and is not seen by the weak formations
Well Control Considerations
![Page 42: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/42.jpg)
42
![Page 43: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/43.jpg)
43
![Page 44: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/44.jpg)
44ATM
General Summary
Dual Gradient Drilling is a method that offers potential for lowering drilling costs in very deep waters:
• Fewer casing strings• Smaller rigs• Less time on location
The method utilizes one or more small-diameter return lines from the seafloor to the surface. The drillpipe is separate from the return lines
![Page 45: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/45.jpg)
45ATM
Summary - cont’d
A mudlift system (pump) is used to feed the return lines, thereby making a “dual-density” mud system possible
Wellhead pressure is maintained at seawater hydrostatic, so well is “dead” at all times
Well control is quite similar to that in conventional drilling with a riser, but offers a number of significant advantages
![Page 46: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/46.jpg)
46ATM
![Page 47: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/47.jpg)
47
Gas Lift?Glass Beads?
How to HandleConnections?Trips?
Pumps?Gas Lift?Glass Beads?
Rotating BOP
Dual Gradient Alternatives
![Page 48: 27 Dual Gradient Drilling](https://reader031.vdocument.in/reader031/viewer/2022013106/577ccd351a28ab9e788bc908/html5/thumbnails/48.jpg)
48ATM
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