HOUSTON -- Logan's new 15K psi high-pressure casing patches are designed to repair damaged casing in high-pressure environments. Rated for 15,000-psi (103 MPa) working pressure, the Logan 15K psi High Pressure Casing Patch can seal internal and external pressure without restricting the bore's internal diameter, according to the company. Once installed, the patch restores integrity to the casing and becomes a permanent part of the string, the company says.
Major load bearing components are manufactured of alloy steel. A top sub, bowl, and cut-lipped guide, and optional extensions make up the outer components of the assembly. Internal components include a basket grapple control, basket grapple, four Type L high-pressure packer sets, and a packer protector with shear pins.
A longer-than-standard basket grapple engages more of the casing to provide additional pull load. High-pressure packers are made of a blend of synthetic rubber and Kevlar material that is compatible for service with most drilling and completion fluids, and is resistant to gas invasion and abrasion. For maximum top-to-bottom patch integrity, two inverted packers provide sealing in both directions. The packers are fully covered by a packer protector to guard them against damage when engaging the casing into the patch. The packer protector is secured by shear pins, which break when subjected to the excess stress caused when the casing comes into contact with the packer protector.
Typically, the seal assembly is a two-piece device consisting of a seal and a non-extrusion ring. The new Logan design features a three-piece seal assembly comprised of an elastomeric seal, a seal protector/seal backup, and a non-extrusion ring.
Proper preparation of the casing to be patched is important to the success of the 15K psi Logan High Pressure Casing Patch. First, the damaged casing and the casing above the damaged section must be removed. The top of the casing stub is then dressed with a milling tool and the casing is washed over to remove scale and burrs. After the pipe is sized for a uniform sealing surface, the properly assembled Casing Patch is slowly lowered with slow rotation to the top of the fish.
Once the fish has entered the Casing Patch, the string is slacked off with slow rotation until the packer protector bottoms out against the shoulder in the top sub. When the casing is fully engaged in the patch, a tensile load is applied to the Casing Patch to set the basket grapple. Slips are then set on the running string. Finally, the patch is tested. The mud pumps are engaged slowly so as not to slug the packers and the pressure is brought to the test level.
The Logan 15K psi High Pressure Casing Patch adapts to standard casing diameters and can handle the full tolerances of various API casing manufacturers. Depending on operation requirements, the Logan 15K psi High Pressure Casing Patch can be run with or without 5-ft (1.5-m), alloy steel, extension subs. Logan 15K psi High Pressure Casing Patches for H2S (sour service) are also available.