CASING REPAIR
Courtesy
Drilling Manual
Casing Repair
• Casing repair is not exactly a drilling fishing job, but casing collapses, splits, or parts.
• Casing repair involves using a variety of tools downhole.
• Each casing failure must be evaluated based on the specific conditions of the failure before a method of repair
can be determined.
Casing Failure & Repair
• Casing failure
o earth shift or subsidence
o corrosion or erosion
o excess pressure: internal or external
o drill pipe wear
o rod wear while producing the well
o improper makeup when casing running
o backed off shoe joint
o fishing operations inside the casing
Types of Failure
• Casing leaks failure.
o The causes are
o improper makeup,
o drill pipe wear,
o running abrasive drilling stabilizers in the casing,
o Corrosion,
o erosion,
o mechanical wear while fishing or producing the well.
o Split or burst casing occurs from many causes including
Ø bumping the cement plug too hard while cementing,
Ø applying excess internal pressure, or
Ø high tensile loading.
• The same forces that are applied to leaks cause collapsed casing and will require repair.
• Anything that reduces the wall thickness (e.g., wear or corrosion) increases susceptibility to collapse.
• Parted casing is caused by
o improper casing design,
o poor operating procedures or a
o mechanical failure, and usually parts at a connection.
The First Step: Identifying The Problem
In order to repair the casing, determine the:
•Depth of the failure
•Type of failure.
•Whether the casing is cemented at the failure or can be retrieved
Collapse
1.Measure the point at which the drilling bit stops or the string drags .
2.Run a lead impression block to get the dimensions of the collapse.
• The lead impression block is pliable and will make a mold of the failure spot.
Split
1.Run an RTTS tool to determine the depth of the casing split that need repair.
2.Run a casing inspection log to determine the thickness of the casing wall at the split.
3.Run a downhole video camera to get pictures of the split.
RTTS tool
The RTTS tool will tell you the depth at which the split occurs.
1.Set the tool.
2.Pressure up in the annulus.
Casing Inspection Log
• Mechanical calipers examine the inner pipe surface and can detect holes, splits, a swelled or collapsed section, or
perforations.
• Electromagnetic tools examine and discriminate the inner and outer pipe surface.
• Acoustic devices identify the pipe ID and wall thickness.
• All these tools require a prior bit and scraper run to clean the ID of the pipe then proceed with casing repair
operations.
Downhole video camera
• DHV International supplies two types of downhole video camera systems:
o The fiber optic system
o The hawk Eye system.
• The fiber optic system provides continuous, full-motion video.
• This system includes a 7/32ʺ OD fiber optic cable that sends real-time video images to the surface from as far as
14,000ʹ below the surface.
• The camera must be run using the fiber optic cable.
• It will not work from a regular electric wireline.
• The camera has a temperature limitation of 250 degrees F.
• The Hawk Eye system provides static images, like snapshots, that are stored on videotape.
• The camera can be run on any electric wireline.
• For both downhole 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) downhole before filming
Determining The Type of Casing Repair
Collapsed Casing Repair
Split Casing Repair
Casing Repair Equipment
• Casing Roller
• Casing Swage Tool
• Casing Alignment Tool
• Casing Patch
• The Bowen Casing Roller rolls the casing out to its original ID dimension.
• The tool consists of a series of rollers and a tapered nosecone that are 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, knocking the casing back into its original shape.
• The individual rolling elements are interchangeable.
Casing Roller Operating Guidelines
• Make up the BOWEN TUBING and CASING ROLLER to either the drill collars or to the drill pipe; experience has shown that it is
preferable to connect directly to the drill pipe.
• The drill pipe and the roller are rotated at low speed and lowered slowly through the casing until the damaged area is tagged.
• Upon contact with the collapsed casing, increase the rotary speed to 40-75 RPM, start the mud pump and lower gradually.
• The reduced portion of the tapered Nose Cone readily enters between the walls of the collapsed casing.
• As the Mandrel is rotated and lowered, the eccentrics force the Nose Cone and Rollers outwardly against the casing walls
with great lateral pressure restoring the casing to its normal 1.0. and roundness.
• Moderate to heavyweight should be used during operation.
• The use of too little weight, with high rotational speeds, is not recommended.
• Lightweight with high speeds tends to wear the rollers without performing a repair to the pipe.
• If insufficient weight is available in the running string, drill collars should be added.
• The best guide to the amount of weight and rotational speed is to use his experience; as long as steady downward progress is
made by the Casing Roller, the weight-speed ratio is giving the proper results.
• A severely collapsed casing will require more amount of weight for the Roller to enter into and straighten the casing pipes.
• The rugged construction of the BOWEN TUBING and CASING ROLLER allows the operator to apply the maximum amount of
weight and torque without damage to the tool.
Maintain circulation throughout its operation.
Casing swage tool
• A will typically repair the casing & restore collapsed casing to its original ID. Swages are also used to make
gauge runs to ensure the casing size (ID) is clear.
Suggested Bottom Hole Assembly For Casing Swage Tool
• Run a bumper jar above it. You can run a bumper jar that
has 5 feet of free travel, which provides a good amount
of momentum for the strike against the swage.
• Run an oil jar above the bumper jar in case gets stuck
(pipe sticking) and you need to jar it loose.
• Run one drill collar between the bumper jar and the
swage tool to prevent the jars from hanging up on the
casing shoulder.
Tool 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 tool size by 1/4ʺ, 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 run its assembly in the hole, drop all of the work string weight onto the bumper jar, which then slams into
the swage.
Operating Guidelines
• Do not lower the jars below the bad spot in the casing. Circulate to prevent sand or debris from accumulating.
• Increase the swage tool OD by 1/4ʺ on each run so that on the last run, it becomes equal to the drift ID of the
casing.
Casing Alignment Tool
• Need to mill out collapsed casing and repair the casing using a casing
• Use a string mill and casing alignment tool to repair split casing.
Bottom Hole Assembly
• The bottom hole assembly should contain, from bottom to top (connecting
to drill collars):
o
lace /kick joint
o
drill collar for added weight and stability
o
full-gauge string mill dressed to drilling bit size.
Creating a Lace (Kick) Joint For Casing Alignment Tool
• If the casing is completely split in two, then you will need to gain access to the bottom portion of
the casing before you can begin your milling operation.
• Make a kick joint by:
• cutting the pin end of a drill pipe joint off at a 45-degree angle
• welding a plate on the bottom to create a mule shoe
• drilling a 3/4ʺ hole 180 degrees from the long end of the mule shoe face.
• Connecting Split Casing
• When you pump fluid through the kick joint, the pressure from the fluid will force the point of the mule shoe
into the casing stub.
• Attempt to re-enter the split casing by working the shoe into it.
• Important: Once you have re-entered the split casing with the kick joint, leave the joint in the bottom portion of
the casing until you have aligned the casing with the string mill (casing alignment tool) and are ready to pipe
trip out of the hole.
Using The String Mill
• the string mill back and forth through the section of
casing that is split or collapsed.
• Continue to work the mill until it is free to move through
the area without drag (check also torque and drag in
drilling).
Using The Casing Alignment Tool
Casing Patch
• There are several methods for patching damaged casing while maintaining pressure ratings and without
restricting internal bore diameters.
• The casing repair is made by removing the damaged section of the casing and then preparing the casing stub
with a Dress-Off Mill.
• The external patch is run in the hole on the bottom of the new casing string and externally engages the casing
stub.
• The internal patch is a steel liner corrugated longitudinally to provide clearance for running inside the casing.
Covered with a certain material to provide the required seal and the casing diameter may be reduced from 1/8in. to 0.48 in. (12.20 mm).
• Casing patches will pack off and become a permanent part of the casing string type.
• The patch forms a link between the existing casing below and the new casing above.
• Patches are available in Lead or Rubber Seal, Standard or Underwater Design, and Cementing Lead Seal styles.
External Casing Patches
• 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
Lead Seal External Casing Patch
• It is designed to patch damaged casing as simply, effectively, and
permanently as possible.
• The Lead Seal Casing Patch will provide a higher temperature rating
than a Packer Seal Casing Patch.
NOV Lead Seal Type
Baker Tools – Lead Seal Type
Operating procedure
Maintaining the seal
• Lead seal patches are used in wells that contain fluids and gases, which are harmful to synthetic rubber packers.
The seals used are compression type, and multiple lead rings.
• Once the seals are set, a minimum amount of pull will keep them in the proper sealing position.
• The tensile load required to set the slips will be more than adequate.
Packer Type External Casing Patch
Bowen Packer Type
• This type is designed to repair damaged casing efficiently and
economically.
• The Rubber Seal Casing Patch will provide a higher pressure rating
than a Lead Seal Casing Patch.
• Different seal systems can be utilized for certain corrosive and
higher temperature applications.
Baker Tools -Rubber Seal Type
Operating procedure
Underwater Lead Seal Type
• Many companies offer a dependable Underwater Lead Seal Casing Patch which basically
follows the same field-proven design as the Standard Lead Seal type for onshore use with
the addition of a certain length (+/-10 ft (3.0 m)) top extension.
• The extension allows the patch to be set from offshore floating rigs using underwater
wellheads and Blowout Preventers.
Operating procedure
Underwater Rubber Seal Type
• The Underwater Rubber Seal Casing Patch is identical to the Standard Rubber Seal Type with the
exception of a top extension.
• The use of a +/- 10 ft (3.0 m) extension between the body and top sub allows the patch to be set from
offshore floating rigs using underwater wellheads and BOP’s.
• Operating procedure
• Dress off the top of the cut with a dressing mill.
• Run the casing patch on the preselected joints of casing and casing hanger.
• Approach the top of the casing stub with caution; if using a motion compensator, set it to a fine
sensitivity.
• Slack off over the stub and seat the hanger in the wellhead.
• Retrieve the hanger running tool.
• Next, go in the hole with a Type B Casing Spear, engage the cut casing and pull it up into the casing
patch extension with the desired tensile pull.
• Release the spear and retrieve.
• Pressure test the patch.
Operating procedure
Lead Seal Cementing
• The Lead Seal Cementing Casing Patch is a casing repair tool designed to
permanently seal and allows cementing of the casing in a single trip.
Operating procedure
Internal Casing Patch
• The Internal Casing Patch is designed to regain the integrity of the wellbore permanently by sealing off many types of leaks.
• It provides a seal against perforations and leaks, and it can also be used to reinforce areas that have been weakened by
corrosion or internal wear.
Tool description
• The casing patch is an internal steel casing liner that is corrugated longitudinally to provide clearance for placement inside the
casing.
• The standard WFD patch is 20ʹ long and fairly pliable before it is set.
• It is made of low-carbon 1010 annealed steel.
• The OD is wrapped in fiberglass and coated with epoxy resin.
• The tool has a temperature rating of 325 degrees F.
• The internal pressure rating for a one-inch hole or less is 9,850 lbs. The external pressure rating is 1,100 lbs.
Selecting the Patch
1- Type and Length:
o Determine the type and length of casing patch to be run using the following criteria:
o An accurate leak description
o Customer pressure requirements
o Future well operations (planned by customer)
o Well conditions
o To ensure a positive seal and to allow for any setting misplacement, the patch should overlap the leak by 6
to 8 feet on each end.
o Split or corroded casing requires the patch to cover the entire joint plus 8 feet overlap on each end.
2- Restricted ID:
o The standard patch has a wall thickness of 0.120ʺ and reduces the casing’s ID by 0.30ʺ
Rig Equipment Considerations
Type and Length
• The size, height, pulling, and pumping capacity of the rig are important in the planning process.
• The length of the patch that can be run in one piece is determined by the rig height.
• Pulling the setting tool through the casing patch could require pulling 60,000 pounds of overpull.
• The pressure required to set the patch could be as high as 5,000 PSI.
• A pump truck capable of high-pressure, low-volume pumping is recommended.
• The work string must be able to handle the pressure and pulling requirements to set the patch.
Operating Checklist
Picking up the Casing Patch
Tool Assembly and Procedure
• The tools generally used, starting at the top, are the following:
o Slide valve
o Bumper jar
o Hydraulic hold down
o Dual cylinder assembly with polished rod
o Extensions as required
o Safety joint
o Cone and collet assembly
Sealing
• The casing patch forms a sheet of metal inside the casing and makes the seal.
• It is not likely to crack or crumble. The epoxy resin extrudes into leaks and cavities in the casing wall, acting as
a gasket and a secondary sealing agent.
• The epoxy resin is fully cured within 24 hours.
THANK YOU