Patent Grant
7533721
The field of this invention is tubular plugs and more particularly plugs to temporarily obstruct a tubular in a bore while a lateral is drilled and removable at a later time preferably without reduction of drift dimension of the tubular.
Plugs have been used in tubulars downhole to temporarily close off a wellbore until another procedure such as drilling a lateral was completed. Plugs have been placed below whipstocks and even integrated into whipstocks as shown in U.S. Pat. Nos. 6,135,206 and 5,992,524. Other designs such as those offered by Total Catcher Offshore AS of Norway have incorporated a pup joint into which a sealed plug is installed. The pup joint is placed in the tubular string when it is made up. It features a firing system for an explosive charge that is hydraulically actuated or timer set to break the plug. An emergency release of the plug is stated to occur with a wireline emergency shoot down tool. This plug is referred to as a disappearing plug made of glass that as a result of setting off the explosive charge disintegrates into sand like particles. While such is the advertised performance of such a plug actual attempts to remove the plug when no longer required have resulted in the plug not completely disintegrating so as to partially obstruct the bore and reduce production from the previously isolated tubular. Another issue was large chunks forming that could not be removed from the wellbore or that would fall further into the well and interfere with later production.
Accordingly, the present invention relates to a plug that is configured to be drilled or milled in a manner that will present small cuttings that can be captured on an adjacent magnetic sub or circulated to the surface. The plug is secured in a manner to prevent rotation during the mill out process and to leave a drift dimension in the tubular at least as large as the drill or mill that was run in to remove the plug in the first place. Those and other features of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the drawing as well as the claims, which are illustrative of the full scope of the invention.
A tubing plug is preinstalled in a premium connection that allows support for the plug outside the drift dimension of the tubulars above and below. The plug is supported in a rotationally locked manner to avoid turning when being milled out. The plug shape internally comprises gentle sloping walls rather than surfaces in alignment with the longitudinal axis of the tubular to allow smaller cuttings to be produced that can be caught on a magnetic sub or circulated to the surface. Because the plug is supported in a zone outside the drift dimension of the adjacent tubulars, milling out the plug does not reduce the drift of the tubular assembly in which the plug was initially mounted. Seals can be provided for bubble tight sealing around the plug.
The plug 28 is preferably made from materials that are compatible with well temperatures and fluids and is relatively easy to mill through as well. The plug 28 is preferably made of at least one of a metallic, a non-metallic, plastic, ceramic and a composite material. Referring to
On the exterior of the plug 28 is a surface 40 that accepts a seal assembly 42 that is shown in
One way to secure the plug 28 is to provide a left hand thread 50 on it to thread into mating thread 52 on box 12. Items 50 and 52 in
The sub that holds the plug 28 supports it in a recess to allow drilling or milling to present a drift dimension at least as large as 54 or 56. The plug 28 is rotationally locked for mill out or drill out. The plug is preferably hollow and made of a material that expedites mill out or drill out. The wall on the plug underside features angled orientation to the longitudinal axis with an arcuate crown 36. These features are designed to create smaller cuttings that can be more easily captured with a magnetic sub or circulated to the surface rather than falling down the tubular or remaining in place and hampering future production. The design eliminates the uncertainties of the prior designs that used glass and an explosive to make the plug hopefully disappear. This design is way cheaper to produce and can reliably remain in place for long periods of time. It can be effectively removed with assurance that the drift dimension will be clear after the removal.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
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