SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V. (Carel van Bylandtlaan 30, The Hague, Hague, NL)
RUDGE, Daniel (6123 Sienna Arbor Lane, Houston, Texas, 77041, US)
| C L A I M S 1 . A floating offshore system in a body of water, comprising: a floating structure; a bearing attached about a circumference of the floating structure; at least one anchor connected to a bottom of the body of water; a line connected to the anchor and the floating structure; a floating vessel adjacent to the floating structure; and a yoke connecting the floating vessel and connected to the bearing; wherein the bearing provides for relative motion between the floating structure and the floating vessel, such that the floating vessel can rotate about a circumference of the floating structure and move vertically relative to the floating structure in response to varying operational and environmental loads. 2. The floating offshore system of claim 1 , wherein the floating structure comprises a cylindrical hull, the bearing attached about a circumference of the cylindrical hull. 3. The floating offshore system of one or more of claims 1 -2, wherein the floating structure comprises a spar. 4. The floating offshore system of one or more of claims 1 -3, wherein the floating structure comprises a drilling derrick. 5. The floating offshore system of one or more of claims 1 -4, wherein the floating structure comprises a drilling derrick adapted to rotate about a central axis of the floating structure, as the floating vessel rotates about the central axis of the floating structure. 6. The floating offshore system of one or more of claims 1 -5, wherein the floating structure comprises a drill floor. 7. The floating offshore system of one or more of claims 1 -6, wherein the yoke comprises a frame connected one or more wheels. 8. The floating offshore system of claim 7, wherein the bearing comprises one or more rails, the rails adapted to interact with the one or more wheels of the yoke. 9. The floating offshore system one or more of claims 7-8, wherein the one or more wheels comprise at least one vertical load wheel. 10. The floating offshore system one or more of claims 7-9, wherein the one or more wheels comprise at least one radial load wheel. 1 1 . The floating offshore system of claim 9, wherein the rails comprise at least one vertical load rail. 12. The floating offshore system of claim 10, wherein the rails comprise at least one radial load rail. 13. The floating offshore system of one or more of claims 1 -12, wherein the floating structure comprises a moonpool. 14. The floating offshore system of one or more of claims 1 -13, wherein the floating structure comprises a plurality of drillstrings extending from the floating structure to the bottom of the body of water. |
Field of the Invention
The present invention is directed to floating offshore drilling structures.
Background of the Invention
U.S. Patent Number 5,558,037 discloses a drilling tender having a pair of laterally spaced buoyant hulls with ballast chambers to permit the hulls to be moved between a submerged condition and a surface floating condition. Each hull supports a row of columns. The columns support a working platform including a main deck and a pipe rack deck above the main deck. A bow deck above a forward portion of the pipe rack deck has mounted on a corner portion thereof a main heavy duty crane. The support structure for the crane extends downwardly through the decks and down into one of the columns. Between the main and pipe rack decks, the support structure is formed by a plurality of bulkheads. These bulkheads have portions extending down into the column to transmit forces created by operation of the crane to the column. A personnel bridge is pivotably mounted on the bow deck to allow its free end to be pivoted onto a fixed-position work platform being serviced by the tender. An auxiliary crane is mounted on the pipe rack deck rearwardly of and laterally opposite the main crane. U.S. Patent Number 5,558,037 is herein incorporated by reference in its entirety.
U.S. Patent Number 4, 156,577 discloses a self-propelled drilling tender having mounted therewith a drilling rig and a jack-up platform adapted to be mounted on the drilling tender or ship for transportation from one drilling site to another site. Thereafter drilling operations occur with the drilling on the ship thus enabling the ship to operate as a drilling ship or the platform legs can be lowered to jack the platform off the ship to thereby enable the platform to operate independently as a drilling platform. Further, if desired, the rig can be disassembled or lifted from the drilling platform and moved to land operations adjacent or in the vicinity of the drilling platform and ship to thereby enable land drilling operations to occur. U.S. Patent Number 4,156,577 is herein incorporated by reference in its entirety.
U.S. Patent Number 4,156,577 discloses a mooring and tender system comprising: a deck; a shape that results in a combined environmental load of less than 1 000 kips in a 1 00-year extreme weather condition; a plurality of supports connected to the deck; a plurality of pontoons connecting to the supports, at least two hawsers for connecting the tender to a production platform, each having adequate elasticity to accommodate the wave frequency between the production platform and the tender, and adequate stiffness to synchronize the mean and low frequency movement between the production platform and the tender under an environmental load produced during a storm having a designation of up to a 10- year storm in the tendering position, connecting means securing each hawser; a hawser guidance system; an at least 8-point mooring system with each mooring lines consisting of: a first length of steel wire rope; a length of polymer rope secured to the first length of steel wire rope; a second length of steel wire rope secured to the polymer rope; and means for creating global equilibrium between the production platform's mooring means and the at least 8 point mooring system of the tender. U.S. Patent Number 4, 156,577 is herein incorporated by reference in its entirety.
U.S. Patent Number 5,423,632 discloses an improved method for conducting offshore well operations in which a compliant platform is installed adjacent a selected well site and an auxiliary vessel is temporarily docked to the compliant platform to provide for support for the well operations which will be produced through the compliant platform. In the practice of the improved method, the compliant platform is isolated from vertical loads upon the auxiliary vessel docked thereto during the performance of well operations conducted for the compliant platform by the offshore auxiliary vessel. Another aspect disclosed is an improved system for restraining an offshore drilling vessel temporarily to a compliant platform which uses a slide-connection for isolating the compliant platform from vertical loads upon the offshore drilling vessel during the well operations. U.S. Patent Number 5,423,632 is herein incorporated by reference in its entirety.
There is a need in the art for one or more of the following:
An improved system and method of connecting two floating structures in a body of water;
An improved system and method of connecting two floating structures that provides for rotation of one structure about the other;
An improved system and method of providing a rotational connection of a drilling tender about a spar; and
An improved bearing to provide for rotational engagement of two structures. Summary of the Invention
In one aspect of the invention, there is disclosed a floating offshore system in a body of water, comprising a floating structure; a bearing attached about a circumference of the floating structure; at least one anchor connected to a bottom of the body of water; a line connected to the anchor and the floating structure; a floating vessel adjacent to the floating structure; and a yoke connecting the floating vessel and movable connected to the bearing; wherein the bearing provides for relative motion between the yoke and the floating structure, such that the floating vessel can rotate about a circumference of the floating structure.
Advantages of the invention may include one or more of the following: An improved system and method of connecting two floating structures in a body of water; An improved system and method of connecting two floating structures that provides for rotation of one structure about the other;
An improved system and method of providing a rotational connection of a drilling tender about a spar; and
An improved bearing to provide for rotational engagement of two structures.
Brief Description of Drawings
Figures 1A and 1 B show cross-sectional views of a tender assisted drilling platform in accordance with embodiments of the present disclosure.
Figures 2A, 2B, and 2C show a circumferential bearing in accordance with embodiments of the present disclosure.
Figures 3A and 3B show a moonpool casing with multiple wells in accordance with embodiments of the present disclosure.
Detailed Description of the Drawings
In one aspect, embodiments of the present disclosure generally relate to a platform for offshore drilling operations, for example a spar platform. In particular, embodiments of the present disclosure relate to a spar platform including a tender assisted drilling platform. Typically, a selection of platforms are available for offshore drilling operations {e.g., fixed platform, tension leg platforms, etc.). Spar platforms are one type of platform that may be used, particularly, in ultra- deepwater environments. The spar platform includes a large cylinder that floats in the water and is tethered to the seafloor by a series of lines comprizing chains, cables, synthetic ropes or combinations thereof. Because the spar platform is a floating platform that is not attached to the seafloor, it is able to move in the water when affected by winds, waves and currents in the sea or even to absorb a hurricane. Spar platforms may be beneficial for fields that have a high well density (in other words a large number of wells in a given area). Also, a spar platform allows full drilling, completion, and sidetracking capabilities all to be performed from a single platform. The drilling spar of the present disclosure may be intended to be deployed across a range of water depths, extending at least from 1 ,000 to 10,000 feet (300 to 3000 m).
Embodiments of the present disclosure include a drilling tender platform that is attached to a drilling spar. A drilling tender platform is typically a support vessel that serves in support of a drilling rig. The drilling tender platform acts as a platform for supplies and is stationed alongside the drilling rig from which the rig will work off of to reduce the loads on the actual rig. Drilling tender platforms can be jack-up style (like a lift boat), semisubmersible, barge or ship-shaped . By using a drilling tender platform, a majority of drilling equipment, consumables and services may be carried onboard the drilling tender platform during drilling operations, which allows the drilling spar to be optimized according to its "permanent" functional requirements {e.g., operating as a wellhead platform, with or without production equipment, quarters etc.).
Figures 1 A & 1 B:
Referring to Figures 1 A and 1 B, a tender assisted drilling platform 50 is shown in accordance with embodiments of the present disclosure. The tender assisted drilling platform 50 includes a drilling spar 105 having a large hull 104 that may be cylindrical in overall form (common hull forms have been described in the industry as "classic", "truss" and "cell" spar) submersed below the water level 20 and having a drilling derrick 100 with drill floor 102 thereon) and a drilling tender platform 1 10 that is attached to the drilling spar 105 by a mooring yoke 1 15 and allowed to weathervane (rotate) freely around the drilling spar 105. The drilling tender platform 1 10 floats in the water and may be characterized as a semisubmersible, barge or ship-shaped unit or rig. While ordinarily operating in a passive mode (i.e., unpowered movement), the drilling tender platform 1 10 may include thrusters to improve the heading of the platform to reduce loads and/or bending moments if required.
Further, the tender assisted drilling platform 50 may include accommodation for all required personnel, a personnel transfer system (to allow personnel to transfer safely between the tender platform and drilling spar as required), a pipe handling system 1 12 and power, cement, and mud lines 1 14, which provide communication between the drilling spar 105 and the drilling tender platform 1 10. For example, the pipe handling system 1 12 allows drillpipe to be transferred from the drilling spar 105 to the drilling tender platform 1 10, or vice versa, as needed. Similarly, the power, cement, and mud lines provide electrical communication, cement for setting casing, and drilling mud, respectively to the drilling tender platform 1 10.
Additionally, the drilling spar 105 includes a circumferential bearing 120 that allows the drilling tender platform 1 10 to rotate or weathervane about the drilling spar 105. In certain embodiments, the circumferential bearing 120 may be arranged around the outside of the hull 104 of the drilling spar 105 as shown in Figure 1 A. In this configuration, the circumferential bearing 120 may be positioned around the drilling spar 105 at a level determined by the height at which the drilling tender platform 1 10 sits in the water. With the height of the circumferential bearing 120 thus fixed on the drilling spar, differential vertical motion between the drilling spar 150 and the drilling tender platform 1 10 is then accommodated by the articulated yoke 1 1 5.
Alternatively, the circumferential bearing 120 may be configured to slide vertically on the hull 104 of the drilling spar 105 to accommodate the drilling tender platform 1 10 as it bobs in the water. In other embodiments, the bearing 120 may be located directly beneath the drill floor 102 of the drilling derrick 100 as shown in Figure 1 B. In this configuration, the mooring yoke 1 15 extends downward between the drill floor 102 of the derrick 100 and the drilling tender platform 1 10 to connect the drilling tender platform 1 10 to the drilling spar 1 05. Figures 2A. 2B. and 2C:
Referring to Figures 2A, 2B, and 2C, multiple views of a circumferential bearing 120 employing a bogey and rail based system are shown in accordance with embodiments of the present disclosure. As shown, the bearing 120 is attached to the hull 104 of the drilling spar 105. The bearing 120 includes a frame 121 on which vertical load bearing wheels 122 and radial load bearing wheels 124 are mounted. The vertical load bearing wheels 122 contact vertical rails 123 and are configured to withstand vertical loads associated with vertical movement of the drilling tender platform in the water. The radial load bearing wheels 124 contact radial rail 125 and are configured to withstand radial load transfer as the drilling tender platform rotates around the drilling spar. The circumferential bearing 120 may have segment rails spaced evenly around the circumference of the hull (as opposed to one continuous rail) to facilitate periodic removal, inspection and maintenance of the bearing components. In alternate embodiments, the circumferential bearing 120 may be configured as a precision 3-race roller type bearing unit.
Figure 2B also shows the mooring yoke 1 15 attached to the circumferential bearing 120. The mooring yoke 1 15 may be articulated (hinged) at each end so as to minimize bending loads in the mooring yoke 1 15 itself. In addition to its own weight, the mooring yoke 1 15 may be designed to carry mooring loads primarily in tension and/or compression, i.e., loads caused by the drilling tender platform 1 10 (Figure 1 ) pulling away from the drilling spar 105 (tension) and/or moving toward the drilling spar 105 (compression). Additionally, the mooring yoke 1 15 may withstand smaller bending moments that may be present due to internal resistance in the articulated joints.
Further, as the drilling tender platform weathervanes around the drilling spar, the drilling derrick may also be required to rotate to facilitate continuous drilling operations, hook-up of drilling services, and/or transfer of materials between the drilling tender platform and the drilling derrick. As such, the drilling derrick may be mounted on a circular bearing or track. Because the drilling derrick may be positioned over a particular well that is being drilled, the axis of rotation of the drilling derrick may remain aligned with the vertical axis of the well 101 (Figure 1 ) being drilled.
In certain embodiments, the drilling derrick may be mounted on skid beams located beneath the circular bearing or track that allows the drilling derrick to rotate. The drilling derrick may skid on the skid beams in a horizontal plane to a particular location as determined by an operator. In further embodiments, the drilling derrick may be positioned (fixed) centrally over the moonpool so that the drilling derrick's axis of rotation and the axis of rotation of the drilling tender platform are the same, and thus become a global central vertical axis of the drilling spar. A well handling system may be provided to move the well to be worked on from a normal set-back position to the center of the moonpool so that the axis of rotation of the drilling derrick and the vertical axis of the well are aligned on the same central vertical axis as explained below.
Figures 3A & 3B:
Referring to Figures 3A and 3B, views of a moonpool 130 of the drilling derrick (not shown) are shown in accordance with embodiments of the present disclosure. As shown, multiple drillstrings 134 extending downward to wells may be located within the moonpool 130. Also, an overhead moonpool crane 132 may be configured to "pick up" and move the various drillstrings 134 "onto" a central axis 101 of the moonpool 130 for drilling. When not in use, the drillstrings 134 may be stored in a set back position Z as shown in Figure 3B. A well 134 being drilled is positioned at X coaxially with the central axis 101 . Those skilled in the art will understand bending moments created in the drillstrings 1 34 by moving them and the limits within which the drillstrings 134 may be moved within the moonpool 130. Advantageously, embodiments of the present disclosure provide a drilling tender platform that carries the majority of drilling equipment, consumables and services during drilling operations, allowing the drilling spar to be optimized according to more permanent functional requirements, such as production. This reduces development costs in comparison to a drilling spar designed to provide an integral drilling capability. Additionally, embodiments disclosed herein may reduce costs of newly built drilling tender platforms while also allowing existing shallow water drilling tender units to be economically modified to operate in deep water (e.g., by eliminating the need to upgrade the mooring system of the drilling tender) . Finally, embodiments disclosed herein may provide a drilling tender platform capable of being redeployed multiple times and being used across multiple well locations, which reduces day rates and lowers overall well costs.
Illustrative Embodiments:
In one embodiment, there is disclosed a floating offshore system in a body of water, comprising a floating structure; a bearing attached about a circumference of the floating structure; at least one anchor connected to a bottom of the body of water; a line connected to the anchor and the floating structure; a floating vessel adjacent to the floating structure; and an articulated yoke connecting the floating vessels at one end connected to the drilling tender and at the other connected to the circumferential bearing; wherein the bearing and yoke provide for relative motion between the floating structures, such that one floating vessel can rotate about the other. In some embodiments, the floating structure comprises a cylindrical hull, the bearing attached about a circumference of the cylindrical hull. In some embodiments, the floating structure comprises a spar. In some embodiments, the floating structure comprises a drilling derrick. In some embodiments, the floating structure comprises a drilling derrick adapted to rotate about a central axis of the floating structure, as the floating vessel rotates about the central axis of the floating structure. In some embodiments, the floating structure comprises a drill floor. In some embodiments, the yoke comprises a frame connected one or more wheels. In some embodiments, the bearing comprises one or more rails, the rails adapted to interact with the one or more wheels of the yoke. In some embodiments, the one or more wheels comprise at least one vertical load wheel. In some embodiments, the one or more wheels comprise at least one radial load wheel. In some embodiments, the rails comprise at least one vertical load rail. In some embodiments, the rails comprise at least one radial load rail. In some embodiments, the floating structure comprises a moonpool. In some embodiments, the floating structure comprises a plurality of drillstrings extending from the floating structure to the bottom of the body of water.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.