Wellbores for the production of hydrocarbon fluid are typically provided with steel casings and/or liners to provide stability to the wellbore wall and to prevent undesired flow of fluid between the wellbore and the surrounding earth formation. A casing typically extends from surface into the wellbore, whereas a liner may extend only in a lower portion of the wellbore. However in the present description the terms “casing” and “liner” are used interchangeably and without such intended difference.
In a conventional wellbore, the wellbore is drilled in sections whereby each section is drilled using a drill string that has to be lowered into the wellbore through a previously installed casing section. In view thereof the wellbore and the subsequent casing sections decrease in diameter with depth. The production zone of the wellbore therefore has a relatively small diameter in comparison to the upper portion of the wellbore. In view thereof it has been proposed to drill a “mono diameter” wellbore whereby the casing or liner to be installed is radially expanded in the wellbore after lowering to the required depth. Subsequent wellbore sections therefore may be drilled at a diameter larger than in the conventional wellbore. If subsequent casing sections are expanded to the same diameter as the previous section, the wellbore diameter may remain substantially constant with depth for several sections.
A tubular member such as a section of casing or liner can be expanded by forcing an expansion member, such as an expansion cone or expansion mandrel through the passage of the tubular member, by mechanical and/or hydraulic pulling and/or pushing forces.
The expansion member engages at least part of the inner surface of the tubular member, and the sliding action against the pipe produces a friction force at the interface between the engaging surface area of the cone and the contact part of the inner surface of the tubular member. Lubrication of the interface is required, and various lubrication methods have been proposed.
U.S. Pat. No. 9,422,794 discloses a system for lining a wellbore. In this known method a well tubular is expanded by moving an expansion cone therethrough. The expansion cone is connected to a drill string that is pulled up, whilst the upper end of the tubular is maintained in a fixed position within an previously installed well tubular by a radially expanded top anchor assembly. The well tubular was internally lubricated with Malleus STC1 lubricant prior to expansion.
U.S. Pat. No. 6,557,640 discloses a method of lubricating an interface between a tubular member and an expansion cone, wherein a lubricating fluid is injected through at least a portion of the expansion cone into the trailing edge portion of the interface between the expansion mandrel and a tubular member during the radial expansion of the tubular member.
U.S. Pat. No. 6,695,012 discloses various lubrication systems and methods for expandable tubulars. In some embodiments, a layer of lubricant is coupled to the interior surface of a tubular member. In another embodiment, the interior surface is coupled with a first part of a lubricant, and a second part of the lubricant is circulated as part of a fluidic material during the expansion of the tubular member. Moreover, a number of suitable coatings for tubulars and coating components are disclosed, incorporated herein by reference.
Other known lubricating coatings are disclosed in US patent applications US2011/0285124 and US 2016/145532.
Experience with commercially available lubricating coatings has indicated that they have shortcomings that may result in poor or lack of lubrication, which may lead to field failure with catastrophic consequences such as: stick slick phenomena, galling, overpull or expansion pressure increase, pipe rupture and eventually stuck expansion cones and/or other well equipment. These conditions can lead to sidetracking and, in the worst case scenario, losing the well.
There is a need for an improved method and apparatus that provides more reliable lubrication during expansion of an expandable tubular.