05 Hole Problems.pdf

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PETE 411Well Drill ing

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, 1.14

due 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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Costly Mud Makeup

Loss of Production

Fire

Loss of Permit to Drill

Results:



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Preventive Measures:

Crew Education

Good Mud Program

Study Wells in Area

…to be prepared



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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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Differential Pressure Sticking

Filter Cake

Deposited AFTER Circulation Stops

- While Still on Bottom

Causes, cont’d:



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Results:

Fishing Operations

Back off, POH, RIG w/fishing string

Loss of Hole

or at least part of the hole



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Use Minimum Mud Weight Requiredto Control Formation Pressures.

Use Special Drill Collars (spiral)

Use Centralizers on Casing

Periodically Establish Circulationwhile Running Casing or Drillpipe

in Deep Hole




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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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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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Hole Problems - Junk in Hole

Bit Parts Missing

Items from Surface Droppedinto Hole

Erratic Torque

Indication:



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Cause:

Negligence of Crew

Result:

Fishing Operation



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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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(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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Results:

Possible Loss of Life and Property

Legal and Financial Problems



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Crew Education

Be Alert

Blowout Control Equipment on RIG

including Pit Volume Indicators




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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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Causes:

Too much Weight on Bit

Dipping Formation

Anisotropic Formation

Too Small Drill Collars

No Stabilizers



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Results:

Uneven Spacing (on bottom)

Legal Problems Production Problems

Cementing Problems



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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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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:

water of ft400ft/bbl05.0

bbl20 =

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 psiTotal pressure at 16,000 ft = 13,963 psi

lb/gal78.16.052)(16,000)(0

13,963 weightmudEffective ==



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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 psiTotal pressure at 12,500 ft = 10,869 psi

lb/gal72.16.052)(12,500)(0

10,869 weightmudEffective ==



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Before Water After Water

Water - 20 bbls

400 ft

12,500 ft

EMW = 16.72 lb/gal

BHP = 13,963 psig

Mud - 17.0 lb/gal

16,000 ft

EMW = 16.78 lb/gal

10,869 psig



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END

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Lesson 5

Hole Problems

05 Hole Problems.pdf

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