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PETE 411 Well Drilling

Lesson 5

Hole Problems

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Lesson 5 - Hole Problems

Lost Circulation Stuck Pipe

• Keyseat- Crooked Hole• Differential Sticking• Mechanical Sticking

Junk in Hole Kicks and Blowouts Crooked Hole

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Read:

* Applied Drilling Engineering, Ch. 1* Definitions

HW #2 ADE 1.12, 1.13, 1.14due Friday, Sept. 13. 2002

Homework

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Hole Problems - Lost Circulation

Flow out < Flow in (e.g 400 < 500)

Drop in Mud Pit Volume

Blowout

Indication:

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Hole Problems- Lost Circulation

Poor Drilling Fluid Characteristics

Induced Fracturing of Formation From Rapid Pipe Movement

Causes:

High Formation Permeability (e.g. fractures)

Low Formation Pore Pressure

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Hole Problems- Lost Circulation

Costly Mud Makeup

Loss of Production

Fire

Loss of Permit to Drill

Results:

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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

Use Lost Circulation Material as Mud Additive (fibrous or granular)

Drill Through Troublesome Interval and Case Off

Decrease Mud Weight

Decrease Circulation Rate

Remedial Measures:

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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

Differential Pressure Sticking

Filter Cake

Deposited AFTER Circulation Stops

- While Still on Bottom

Causes, cont’d:

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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

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

Preventive Measures:

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Hole Problems - Stuck Pipe

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

Remedial Measures:

If Circulation Can Be Established:

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Hole Problems - Stuck Pipe

If Circulation Cannot Be Established:

Cut Pipe or Unscrew Joint - and Fish

Remedial Measures:

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KEYSEAT

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P1

P2

P1 >> P2

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Thick Filter Cake

Thin Filter Cake

F = N

N = P A

F = P A

How is filter cake formed?

Pipe Stuck in Wall Cake

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Hole Problems - Junk in Hole

Bit Parts Missing

Items from Surface Dropped into Hole

Erratic Torque

Indication:

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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

Crew Education

Preventive Measure:

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)

Returns to Surface after Circulation is Stopped (KICK!)

Well Out of Control - Big Problem!

Lost Circulation . . .

Indication:

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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

Crew Education

Be Alert

Blowout Control Equipment on RIG including Pit Volume Indicators

Preventive Measures:

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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

Periodic Directional Surveys

Stuck Drill String

Casing Problems

Indication:

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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

Avoid Buckling of Drill Pipe by using sufficient number of

drill collars Use “Oversize” Drill Collars Use Reamers and Stabilizers Start the Hole Vertically

Preventive Action:

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Hole Problems - Crooked Hole

Plug Back and Sidetrack

Use Whipstock

Use Reamers in 3 Locations

Remedial Action:

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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

12,500 ft

BHP = 13,963 psig

Mud - 17.0 lb/gal

16,000 ft

BHP = ?

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Example - Solution

Determine: The effective hydrostatic head and mud weight in lb/gal.

Solution:

waterof ft 400ft/bbl05.0

bbl20

Water gradient = 0.052 * 8.33 = 0.433 psi/ftMud 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

lb/gal 78.16.052)(16,000)(0

13,963 weightmud Effective

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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

lb/gal 72.16.052)(12,500)(0

10,869 weightmud Effective

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Before Water After Water

Water - 20 bbls

400 ft

12,500 ftEMW = 16.72 lb/gal

BHP = 13,963 psig

Mud - 17.0 lb/gal

16,000 ftEMW = 16.78 lb/gal

10,869 psig

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END

of

Lesson 5

Hole Problems