PETE 411
Well Drilling
Lesson 5
Hole Problems
1
Lesson 5 - Hole Problems
 Lost Circulation
 Stuck Pipe
• Keyseat- Crooked Hole
• Differential Sticking
• Mechanical Sticking
 Junk in Hole
 Kicks and Blowouts
 Crooked Hole
2
Homework
Read:
* Applied Drilling Engineering, Ch. 1
* Definitions
HW #2 ADE 1.12, 1.13, 1.14
due Friday, Sept. 13. 2002
3
Hole Problems - Lost Circulation
Indication:
 Flow out < Flow in
(e.g 400 < 500)
 Drop in Mud Pit Volume
 Blowout
4
Hole Problems- Lost Circulation
Causes:
 High Formation Permeability (e.g. fractures)
 Low Formation Pore Pressure
 Poor Drilling Fluid Characteristics
 Induced Fracturing of Formation
From Rapid Pipe Movement
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Hole Problems- Lost Circulation
Results:
 Costly Mud Makeup
 Loss of Production
 Fire
 Loss of Permit to Drill
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Hole Problems- Lost Circulation
Preventive Measures:
 Crew Education
 Good Mud Program
 Study Wells in Area
…to be prepared
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Hole Problems- Lost Circulation
Remedial Measures:
 Use Lost Circulation Material
as Mud Additive (fibrous or granular)
 Drill Through Troublesome
Interval and Case Off
 Decrease Mud Weight
 Decrease Circulation Rate
8
Hole Problems - Stuck Pipe
(drill pipe, drill collars, casing)
Indication:
 Cannot Pick Up Pipe
(Venezuela case)
Causes:
 Cave - ins
 Keyseat - Crooked Hole
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Hole Problems - Stuck Pipe
Causes, cont’d:
 Differential Pressure Sticking
 Filter Cake
 Deposited AFTER Circulation Stops
- While Still on Bottom
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Hole Problems - Stuck Pipe
Results:
 Fishing Operations
Back off, POH, RIG w/fishing string
 Loss of Hole
or at least part of the hole
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Hole Problems - Stuck Pipe
Preventive Measures:
 Use Minimum Mud Weight Required
to Control Formation Pressures.
 Use Special Drill Collars
(spiral)
 Use Centralizers on Casing
 Periodically Establish Circulation
while Running Casing or Drillpipe
in Deep Hole
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Hole Problems - Stuck Pipe
Remedial Measures:
If Circulation Can Be Established:
 Erode Mud Filter Cake - at High Fluid
Velocity (speed up pumps)
 Spot Special Fluid; Oil, Acid
 Reduce Mud Weight as Far as Possible
 Rotate Pipe - Keep Moving Pipe
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Hole Problems - Stuck Pipe
Remedial Measures:
If Circulation Cannot Be
Established:
 Cut Pipe or Unscrew Joint
- and Fish
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KEY
SEAT
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P1 >> P2
P1
P2
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F = mN
Thick Filter Cake
N = DP A
Thin Filter Cake
F = m DP A
How is filter cake formed?
Pipe Stuck in Wall Cake
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Hole Problems - Junk in Hole
Indication:
 Bit Parts Missing
 Items from Surface Dropped
into Hole
 Erratic Torque
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Hole Problems - Junk in Hole
Cause:
 Negligence of Crew
Result:
 Fishing Operation
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Hole Problems - Junk in Hole
Preventive Measure:
Crew Education
Remedial Measures:
 Run Junk Basket
 Run Basket with Collapsible Teeth
(“Poor Boy” Basket)
 Run Magnet
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Hole Problems - Blowout
(oil, gas or water)
Indication:
 Returns to Surface after Circulation is
Stopped (KICK!)
 Well Out of Control - Big Problem!
 Lost Circulation . . .
21
Hole Problems - Blowout
(oil, gas or water)
[surface or underground]
Causes:
 Loss of Hydrostatic Head
due to Lost Circulation
 Poor drilling Fluid
 Swabbing Effect while Pulling Drillpipe
 Insufficient Mud Weight
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Hole Problems - Blowout
Results:
 Possible Loss of Life and Property
 Legal and Financial Problems
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Hole Problems - Blowout
Preventive Measures:
 Crew Education
 Be Alert
 Blowout Control Equipment on RIG
including Pit Volume Indicators
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Hole Problems - Blowout
Remedial Action:
If on Bottom:
 Use proper Mud Weight
 Add Lost Circulation Materials
In Extreme Case of Blowout:
 May Have to Directionally
Drill a Relief Well
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Hole Problems - Crooked Hole
Indication:
 Periodic Directional Surveys
 Stuck Drill String
 Casing Problems
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Hole Problems - Crooked Hole
Causes:
 Too much Weight on Bit
 Dipping Formation
 Anisotropic Formation
 Too Small Drill Collars
 No Stabilizers
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Hole Problems - Crooked Hole
Results:
 Uneven Spacing (on bottom)
 Legal Problems
 Production Problems
 Cementing Problems
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Hole Problems - Crooked Hole
Preventive Action:
 Avoid Buckling of Drill Pipe by
using sufficient number of drill
collars
 Use “Oversize” Drill Collars
 Use Reamers and Stabilizers
 Start the Hole Vertically
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Hole Problems - Crooked Hole
Remedial Action:
 Plug Back and Sidetrack
 Use Whipstock
 Use Reamers in 3 Locations
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Lost Circulation Example
This Example shows how to determine the mud weight
that can be supported by the formation and also the mud
weight that will control the subsurface pressure.
 Well depth = 16,000 ft
 Protective casing seat = 12,500 ft
 Mud Weight = 17.0 lb/gal
 Drillpipe size = 4.5 in.
 Hole size, casing I.D. = 8.5 in.
 Annulus volume = 0.05 bbl/ft
 Water required to fill hole = 20 bbl
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Before Water
After Water
Water - 20 bbls
400 ft
Mud - 17.0 lb/gal
12,500 ft
16,000 ft
BHP = ?
BHP = 13,963 psig
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Example - Solution
Determine: The effective hydrostatic head
and mud weight in lb/gal.
Solution:
20 bbl
 400 ft of water
0.05 bbl / ft
Water gradient = 0.052 * 8.33 = 0.433 psi/ft
Mud gradient = 0.052 * 17 = 0.884 psi/ft
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Example 3.1
Pressure imposed at total depth:
400 ft of water x 0.433 psi/ft
= 173 psi
15,600 ft of mud x 0.884 psi/ft
= 13,790 psi
Total pressure at 16,000 ft
= 13,963 psi
13,963
Effective mud weight 
 16.78 lb/gal
(16,000)(0 .052)
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Example 3.1
Pressure imposed at the casing seat:
400 ft of water x 0.433 psi/ft
=
173 psi
12,100 ft of mud x 0.884 psi/ft = 10,696 psi
Total pressure at 12,500 ft
= 10,869 psi
10,869
Effective mud weight 
 16.72 lb/gal
(12,500)(0 .052)
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After Water
Before Water
Water - 20 bbls
400 ft
Mud - 17.0 lb/gal
10,869 psig
BHP = 13,963 psig
12,500 ft
EMW = 16.72 lb/gal
16,000 ft
EMW = 16.78 lb/gal
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END
of
Lesson 5
Hole Problems
37