1. Field of the Invention
The present invention generally relates to seals for an expandable tubular. More particularly, the present invention describes a method of applying seals for an expandable tubular in downhole applications.
2. Background of the Invention
In recent years, the use of expandable tubulars has become more common in the drilling, repair, and completion phases of well bore construction. In these phases, it is necessary to protect tubulars (e.g., casing, tubing, and/or seal bores) from scarring; and/or to protect sealing and anchoring devices; and/or to prevent the tubulars from being scarred while being run down hole.
In some cases, due to the limits of expansion of the expandable tubulars (e.g., casings and tubings), the outside/outer diameter (OD) of the tubular is as close as possible to the inside/inner diameter (ID) of the wellbore or casing. Rubber rings and other devices are either molded or attached to the expandable tubular to act as centralizers and seals after the tubular is expanded. The rubber rings may also serve to keep anchoring devices (anchors) attached to the tubular from scarring the casing and/or seal bores. During the expansion process, the anchoring devices (anchors) are pressed into the casing and hold the tubular in place; and the rubber rings or other devices would function as seals.
Because the OD of the tubing and seals and anchors is very close to the casing ID, if the tubing or seals touch the casing, the seals will compress below the tolerance of the anchors and damage the casing and/or seal bores. The anchors can also be dislodged causing more damage. In addition, the tubing and casing can be scarred causing it to split.
It is difficult to attach a centralizer to the tubing due to the clearance. Rubber or compressible material is applied that is slightly larger than the attachments. This rubber acts as centralizers and also protects the attachments. Since they are rubber, they will compress when the tubing rubs the casing, and the attachments will hit the casing wall. This will cause damage to the casing and tubing. If the tubing is scarred, it can split when expanded and the attachments can be damaged. After expanding, the rubbers become seals.
Seals are used with expandable tubing to seal the area between the expanded tubing and casing to restrict the well pressure from escaping between the two pipes. Having the rubber seals manufactured on the tubing requires a large amount of time. The seals are molded on and require machining to size. In some cases, there is damage to the tubing during the handling and chucking process. At times, it takes several weeks to complete the molded seals.
Accordingly, there is continuing need and interest to develop seals for expandable tubulars/assemblies.