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Expandable steel Patches

Expandable Steel Patches

Introduction

As optimizing the recovery of hydrocarbon reserves has grown in importance, and effective reservoir management has become increasingly complex, the need for shutting-off unwanted perforations in both production and injection wells has been growing, and requirements to restore casing condition to lengthen well life have become common.

Restoring casing integrity, for both casing repair or perforation shut-off, means meeting the seemingly contradictory objectives of obtaining a high pressure resistant seal down hole, while at the same time not significantly reducing the casing diameter nor restricting access to the wellbore below. A wide number of very different solutions have been used, including cement squeezes, injection of gels, straddle packers, and various composite and steel patches, all with varying levels of success.

Saltel Industries has developed, tested and trialed the use of a stainless steel Patch which is expanded down hole to create a high pressure inner lining inside the casing. Initially designed for perforation shut-off the technology is also suitable for repairing short lengths of damaged or corroded casing.

Description

The Saltel Industries Expandable Steel Patch is expanded by using an Inflatable Packer. It is a permanent solution to repair a zone of damaged tubing or casing, to shut-off unwanted perforations, to seal a leaking sliding sleeve, or other remedial operations.

The setting procedures for Saltel Patches are very different from those used with other expandable systems. The steel is not pushed out to a pre-determined diameter by a cone, but is expanded using an Inflatable Packer which will ensure the Patch is pushed out to seal effectively against the inside of the existing casing, irrespective of the precise casing ID.

Patches are made from high quality 304L or 321 Stainless Steel Sheets, specially selected for this application. Steel Sheet are rolled, welded and Thermally Treated to compose up the Patch Tube core (1).

The Tube is then machined to constitute the Patch Extremities (2) and the Patch Central tube (3).
The Extremities are designed to receive the Sealing System made of the Elastomer Outer Skin (Standard Patch) or different machined profiles O-ring groves (HT Patch).
The Central tube is welded between the two extremities.

The tubes have different diameters (4.5in to 13.3/8in casing size) and thickness (2-6mm).

The maximum Patch length is given by the shipping and the rig-up limitations. The standards lengths are from 3.95m to 12m.

For Customized Patch, it is possible to run a longer Patch using the Expandable Connections developed by Saltel Industries. These connections can maintain the mechanical and hydraulical integrity of the Patch during and after expansion. Thanks to these Expandable connections, and depending on the Patch Diameter, it is possible to run and set up to 30m long Patches.

The tubes have different diameters (4.5in to 13.3/8in casing size) and thickness (2-6mm).

Operation Principles

On surface the DHET is placed inside the Patch, and the Inflatable Packer Element is then inflated enough to grip the inside of the Patch (not enough to start the expansion).

The Expandable Steel Patch is also held by the Patch Holder (PH) of the Down Hole Expansion Tool (DHET) which supports and protects the lower end of the Patch.

The assembly is run in to the setting zone on tubing, drill pipe or coiled tubing.

The Packer is inflated using pressure from surface to expand the top of the Patch anchoring it in place. The packer is then deflated, run in 3ft/1m and the next section is expanded. This is repeated as much as necessary until the full length is expanded. During the BHA going down the Setting Controller plays as a drift to control the Patch is correctly set in place.

Example of Setting a Patch to seal off unwanted perforations

Explanation in 12 Steps:

1) Example of using a Patch to seal off unwanted perforations
2) Run-in and position the assembly
3) Increase pressure through the tubing to expand and anchor the Patch
4) Deflate the packer, the Patch is now released from the running tools
5) The string is run in just below the first step
6) The packer is re-inflated to expand the second step
7) Surface pressure is bled-off to deflate the packer
8) The assembly is run in to the next step, the setting controller continually verifies the inside diameter.
9) Surface pressure is again applied to expand the next step
10) Pressure is bled off, the packer deflates. These steps are repeated as much as necessary until the Patch is fully expanded
11) The setting controller is run right through the Patch to check the inside diameter
12) The well can be put immediately back on line with the perforations well sealed and a large through bore diameter

Features and benefits

Setting

• A large clearance while running in hole
• A real time Setting Controller controls the ID of the set Patch during the operation. Any anomaly can be immediately detected and corrected

Patch Tubular manufacturing Process entirely controlled to guaranty an Expandable Steel Patch Quality Policy of high level

• From the Mill Sheet selection to Patch ready to go
• The Mill Sheet is selected to have the adapted and repetitive mechanical and geometry characteristics
• Five different Patch thickness: 2mm; 3mm; 4mm; 5mm; 6mm
• High expansion ratio
• Repetitive and predictable characteristics in term of service pressure
• Possible to be customized

Sealing capacity

• Two Sealing Systems
  • Outer skin in Hydrogenated Nitril (HNBR) for service temperature <120°c li="">
  • FFKM O-rings for high temperature applications up to 300°C
• Two Patch Designs
  • Extremities Sealing Patch (applicable for the majority of the cases)
  • Total Sealing Patch (when it is necessary to seal on the entire length of the Patch)

Characteristics

• Expansion ratio up to 25%
• External service pressure can be optimized with the choice of the Patch thickness
• Can be set in casing or open hole with irregular geometry or ovalisation up to 20%
• A second Patch can be run through a previous Patch set below