14.0 Casing Repair
14.0 Casing Repair
14.0 Casing Repair
Overview
Casing repair is not exactly a fishing job, but if the casing collapses, splits, or parts you’re
fishing skills can help you repair the casing. Casing repair involves using a variety of tools
down hole.
Each casing failure must be evaluated based on the specific conditions of the failure before
a method of repair can be determined. This chapter will help you analyze the casing failure,
and it will provide instruction on repairing collapsed or split casing.
When you complete this chapter, you will be able to:
•identify the type and depth of failure
•determine the best method of repair depending on the nature of the failure
•use a casing roller to repair casing
•use a casing swage to repair casing
•use a string mill and casing alignment tool to repair casing
•use an external patch to repair casing
•use an internal patch to repair casing.
Topics
Casing Failure
Casing Roller
Casing Swage
Exercises
Causes of Failure:
Types of Failure:
•Casing Leaks
•Split or Burst casing
•Collapsed casing
•Parted casing
•Casing strings stuck off bottom on Sub Sea wellheads
Overview:
In order to repair the casing, you need to determine the depth of the failure, type of failure
and whether the casing is cemented at the failure.
Collapse:
If casing has collapsed, run a lead impression block to get the dimensions of the
collapse.
Split:
Retrievable packer :
Casing Logs:
DHV International supplies, fiber optic system and the hawk Eye system :
1. The fiber optic system provides continuous, full motion video. This system includes a
7/32" OD fiber optic cable that sends real time video images to the surface from as far
as 14,000' below the surface. The camera must be run using the fiber optic cable. It
will not work from regular electric wire line. The camera has a temperature limitation
of 250 degrees F.
2. The Hawk Eye system provides static images, like snapshots, that are stored on
videotape. The camera can be run on any electric wire line. For both down hole video
systems, a lens surfactant keeps most oil and mud off of the camera lens, but to get the
clearest images, you should still pump clear fluid (water) down hole before filming.
Split Casing
If the casing is… THEN repair the break using a(n)…
Description:
Casing Roller rolls the casing out to its original ID dimension. The tool consists of
interchangeable rollers and a tapered nosecone all mounted on an eccentric mandrel.
As the tool rotates, one roller hits one side of the casing while another roller hits the
opposite side of the casing.
Step Action
1 Rotate and lower the roller and the work string until you make
contact with the damaged area.
2 Upon contact, increase the rotary speed to 50–75 RPM and lower the
string slowly, with moderate weight. A high rotary speed with
insufficient weight will wear out the rollers
Use:
A casing swage will typically restore collapsed casing to its original ID. Swages are also
used to make gauge runs to ensure the casing ID is clear
Description:
Swages are made of 4140-grade heat-treated steel. The tool is shaped like an ice cream
cone. The long tapered nose forces the casing back to its original ID. Each time you run in
the hole, you will increase the swage size by 1/4", which will gradually restore the casing
ID to its original dimensions. The lead impression block will help you determine the
swage size to use at the beginning of the swaging operation. When you run the swage
assembly in the hole, you drop all of the work string weight onto the bumper jar, which
then slams into the swage, widening the casing ID.
Guidelines
Do not lower the jars below the damaged area. Circulate to prevent sand or debris from
accumulating. Increase the swage OD by 1/4" on each run so that on the last run, the
swage OD is equal to the drift ID of the casing.
External casing patches are used to repair damaged casing that is not cemented above the
damaged area. This allows the damaged casing to be removed from the well.
Tool Description
Bowen packer type casing patches are external catch tools, designed to catch a previously
prepared fish, pack it off, and become a permanent part of the repaired casing string. The
same method of engagement and release, which is used for Bowen overshots, is employed
in these casing patches. The patches feature positive engagement and positive seal off in
either direction and do not reduce the ID of the casing. Once the patch is set, it becomes a
permanent part of the string, and is usually cemented in place.
•lead seal casing patches
•packer type casing patches. (Standard and High pressure)
1 Use an inside cutter to cut the casing below the damaged area and remove that section
from the well.
2 Use a dressing mill to dress the top of the casing stub to a 45-degree bevel inside and
outside.
3 Make up the patch on a running string of new casing and RIH.
4 As you reach the casing in the hole, slowly rotate to the right while lowering the casing
patch over the stub.
5 Continue lowering until you bump up on the grapple carrier as indicated by loss of weight
on the weight indicator.
6 Take an upward strain, which causes the outer assembly to move upward while the
engaged grapple, carrier and control remain stationary. Compression between the carrier
and guide causes the lead seals to flow around the casing forming an effective seal.
The size of the patch will determine the load required
7 Prior to testing the patch, lower the over pull to 40% of the setting load.
© 2005 Weatherford. All rights reserved.
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Casing Repair_ External Packer Sealing Casing
Patch
1 Use an inside cutter to cut the casing below the damaged area and remove that section
from the well.
2 Use a dressing mill to dress the top of the casing stub to a 45-degree bevel inside and
outside. Dressing the cut casing will prevent the casing from snagging the rubber portion
of the casing patch.
3 Make up the patch on a running string of new casing and RIH.
4 As you reach the casing in the hole, slowly rotate to the right while lowering the casing
patch over the stub.
5 Continue lowering until casing stub contacts the Packer Protector Sleeve (PPS) and shear
pin. Continue down until PPS contacts and stops on the top sub.
6 Pick up on the running string and apply sufficient pull to remove any slack from the
string, and set the slips. No load is required to maintain engagement nor is any load
required to effect or maintain a seal.
7 Pressure test the patch to the manufacturer’s recommendations.
© 2005 Weatherford. All rights reserved.
18
Exercise
Exercise