Patent Application
20130092386
Offshore oil and gas operations often utilize a wellhead housing supported on the ocean floor and a blowout preventer stack secured to the wellhead housing's upper end. A blowout preventer stack is an assemblage of blowout preventers and valves used to control well bore pressure. The upper end of the blowout preventer stack has an end connection or riser adapter (often referred to as a lower marine riser package or LMRP) that allows the blowout preventer stack to be connected to a series of pipes, known as riser, riser string, or riser pipe. Each segment of the riser string is connected in end-to-end relationship, allowing the riser string to extend upwardly to the drilling rig or drilling platform positioned over the wellhead housing.
The riser string is supported at the ocean surface by the drilling rig and extends to the subsea equipment through a moon pool in the drilling rig. A rotary table and associated equipment typically support the riser string during installation. Below the rotary table may also be a diverter, a riser gimbal, and other sensitive equipment.
During installation of the riser string, it may be necessary to temporarily move the entire drilling rig, such as for example when a strong storm is approaching. Before moving the rig, it is necessary to pull up the entire riser. If the riser were left in place, movement of the rig would cause the riser string to damage the rotary table, diverter, gimbal, and other sensitive equipment. Pulling up each section of riser string takes a long time, adding cost to the overall drilling operations. Additionally, there may not be enough time to pull the entire riser string before the rig needs to be moved.
For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:
The following discussion is directed to various embodiments of the invention. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.
Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis.
Drilling rig 126 further includes a moon pool 128 having a telescoping joint 130 disposed therein. The telescoping joint 130 includes a inner barrel 132 which telescopes inside an outer barrel 134 to allow relative motion between the drilling rig 126 and the wellhead housing 110. A dual packer 135 is disposed at the upper end of the outer barrel 134 and seals against the exterior of inner barrel 132. A landing tool adapter joint 136 is connected between the upper end of the riser string 122 and the outer barrel 134 of the telescoping joint 130. A tension ring 138 is secured on the exterior of the outer barrel 134 and connected by tension lines 140 to a hydraulic tensioning system as known to those skilled in the art. This arrangement allows tension to be applied by the hydraulic tensioning system to the tension ring 138 and the telescoping joint 130. The tension is transmitted through the landing tool adapter joint 136 to the riser string 122 to support the riser string 122. The upper end of the inner barrel 132 is terminated by a flex joint 142 and a diverter 144 connecting to a gimbal 146 and a rotary table spider 148.
Before, and even after installation of the riser string 122 to the subsea equipment, it may become necessary to detach the riser string 122 from the diverter 144, the gimbal 146, rotary table 148, and any other sensitive equipment. For example, the drilling rig 126 may need to be moved from one location to another and movement of the drilling rig 126 relative to the riser would damage the equipment. In such cases, instead of pulling up and dismantling the entire riser string 122, the drilling rig 126 may include a hang-off assembly 200 as shown in
As shown in
The assembly 200 also includes a gate member 260 movable relative to the housing 210 from an open position shown in
The assembly 200 also includes a motor 240 that moves the gate member 260 between the open and closed positions. In some embodiments, the motor 240 is a hydraulic drive motor. In some embodiments, the motor 240 is an electric drive motor. As shown, the motor 240 includes a gear that engages an exterior gear profile 262 on the gate member 260. The motor 240 turns the motor gear to apply force to the exterior gear profile. This force moves the gate member 260 and the alignment member 230 between the closed and open positions. Alternatively, the motor 240 may engage a gear profile on the alignment member 230. Also alternatively, the alignment member 230 need not move with the gate member 260.
Shown in
The housing further includes one or more locking mechanisms 218 that engage the adapter 250 to secure the adapter 250 to the housing once landed. In some embodiments, the locking mechanisms 218 are hydraulically operated. In other embodiments, the locking mechanisms 218 are mechanically operated. The locking mechanisms 218 may be either hydraulically or mechanically operated in some embodiments. Shown in the figures are examples of hydraulically operated locking mechanisms 218 that include a slide actuated between locked and unlocked positions with a hydraulic piston. Lock state indicators 219 identify the locking mechanism 218 as locked or not locked. For example, extended indicators 219 indicate a locked state, and retracted indicators indicate an unlocked state. Additional back-up or secondary locking mechanisms may also be included.
With the gate member 260 located in the open position, the riser string running tool 300 moves the adapter 250 and the riser string 122 into the passage 220 through the open section 212 in the side of the housing 210. Once in the passage 220, the adapter 250 is landed such that the adapter profile 252 is supported on the gate member 260 as shown in
Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.
