Mousehole apparatus

#The invention concerns a mousehole apparatus for holding a drill pipe or similar elongate element and a method of operating one or more mousehole apparatuses.

#In well drilling operations, joints of drill pipe are generally connected one after the other to the upper end of the drill string. Drill pipe joints are typically stored near the rig platform, from where they are retrieved, one by one, and placed in a vertical holding tube known as a “mousehole.” The mousehole holds the joint in a vertical orientation, in preparation for connection for the drill string. The mousehole is typically positioned underneath the drill floor and has an opening in the drill floor, near region of the drill floor where drill pipe connection takes place. It is also well known to use a so-called “powered mousehole”, which in fact is a mousehole with an elevating bottom, allowing for adjustment of the mousehole length (depth).

#The state of the art includes U.S. Pat. No. 5,468,121, which discloses a mousehole installed underneath rig floor. The mousehole comprises a longitudinally oriented sleeve depending from the rig floor. The sleeve includes an open top end more or less flush with the rig floor, a closed bottom end, and a wall. Arranged at the bottom end of the mousehole is an expandable (inflatable) bladder which may be used for elevating the pipe joint in the mousehole. The mousehole disclosed in U.S. Pat. No. 5,468,121 also comprises a carriage disposed adjacent to the bottom end of the mousehole and which is operatively engaged by a hoist. The hoist includes a cable guided in a groove of a sheave mounted in the carriage. The cable is secured at one end to an outer surface of the sleeve by means such as a pad eye and looped through parallel slits formed longitudinally on opposite sides in the sleeve for engagement with the sheave. The other end of the cable is then attached to a reel of the hoist in the rig floor. When it is desired to elevate the pipe joint for raising its upper end above the rig floor, the hoist is activated to draw in or shorten the cable and, in turn, elevate the carriage within the mousehole.

#These and other characteristics of the invention will be clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein:

#FIG. 1 is an elevation view and partly cut-away drawing of the retractable mousehole according to the invention, in an unlocked state and suspended from a drill floor;

#FIG. 2 is an elevation view and partly cut-away drawing of a lower portion of the retractable mousehole according to the invention, in an unlocked state;

#FIG. 1 shows an embodiment of the invented mousehole apparatus installed in deck structure having a drill floor 2. A deck frame 8 is arranged on skid beams 34 (which in turn are attached to the deck structure), below the drill floor 2. Suspended by the deck frame is a mousehole tube 14. The mousehole tube extends through an upper guide 6a and a lower guide 6b in the deck frame, and is suspended via a support flange or collar 5 on the tube's upper end which bears against a region 9 of the deck frame's upper surface. The mousehole tube is thus slidably arranged in the deck frame. FIG. 1 shows the mousehole apparatus in a working position, i.e. hanging down from the deck frame 8 and extending into the space 38 between the drill floor and the cellar deck 26.

#Inside the mousehole tube is an elevating bottom 18 (sometimes referred to as a “rabbit” and per se commonly known in the art), arranged and furnished with wheels or a synthetic material 39 so that it may move up and down within the tube. The elevating bottom 18 comprises a support face 20 for the drill pipe, and may conveniently also comprise a shock absorber 40.

#A cable sheave 22 is rotatably connected to the elevating bottom (here: the lower portion) via a pin 23. A cable 16 extends from a winch 10 in the deck frame, down around the cable sheave 22 and back up to the deck frame where it is connected to a second winch 12. This second winch 12 is optional, inasmuch as the cable instead may be connected to a fixture (not shown) in the deck frame 8. The movement of the elevating bottom 18 inside the mousehole tube is thus controlled by the operation of the winch 10 and (optionally) the second winch 12. This is an arrangement for lifting and lowering the elevating bottom which per se is well known in the art. The upper end of the mousehole tube is furnished with a centralizer 4, and the drill floor comprises an opening 3a with a removable cover plate 3b. The centralizer 4 is designed to keep any size tubular within the specified range, at the centre of the mousehole tube.