Multi-Use Offshore Structure

In oilfield exploration and production operations, floating vessels, such as semi-submersibles (“semis”), are commonly used for various offshore tasks utilizing heavy equipment and structures, including, but not limited to, drilling rigs, safety platforms, and heavy lift cranes. For example, in an offshore environment with water depth greater than 120 meters, semi-submersibles are used because a fixed structure is not practical to build, maintain, or support in such great water depths. Furthermore, semi-submersibles are advantageous over other floating vessels, such as drill ships, because drill ships are unstable in rough offshore conditions that have large waves and strong tidal forces. As understood by one skilled in the art, offshore semi-submersibles are not limited to the aforementioned water depths described in the above example.

Referring to, a side view illustration of a semi-submersiblein a typical marine environment is shown. A decksits above the surface of the water. The deckis typically used for drilling, production, or other operations and, therefore, operating equipment, personnel, and operation gear may be disposed thereon. The deckmay be supported by one or more support columns. As shown in this example, the deckis disposed on support columnsandand is, therefore, kept away from any large waves at the surface of the water. Support columnsandare used to support the deck, but may also serve as storage. In addition, the support columnsandmay be ballasted. A pontoon basehas the support columnsanddisposed thereon. The pontoon basemay be substantially rectangular in shape from a side view perspective, a plan view perspective, or both. The pontoon and support columns are typically designed to handle an intended load capacity (e.g., weight, volume) in order to properly support heavy equipment and/or structures intended for use on the deck.

The semi-submersibleobtains buoyancy from ballasted pontoons or ballasted columns. As such, the ballasted structure(s) (ballasted pontoons, ballasted columns, or both) may be filled with water or any other ballasting material (ballasting) or may release water or any other ballasting material (deballasting) to stabilize the semi-submersible. As shown, the semi-submersibleis anchored to the seabedby anchor linesand. The anchor linesandmay be wires, chains, or any other anchoring device known in the art that would function to keep the semi-submersiblein a proper position with respect to the seabed. Furthermore, anchor lines may not be limited to only two lines as shown in this example. The semi-submersiblemay be anchored by any number of anchor lines.

Alternatively, for use in marine environments with a shallower water depth, the semi-submersiblemay be adapted to be disposed on the seabedwithout the use of anchor linesand. In this case, the pontoon basemay be disposed on the seabedand may be affixed to the seabedusing an affixing unit (not shown) to affix the pontoon baseand, ultimately, the semi-submersibleto the seabed.

Requiring additional capacity on permanent semi-submersibles is a recurring problem as it is very difficult to increase the capacity with the semi-submersible in place, such as an increase to topside weight and/or a deck area increase. Thus, a continuing need exists for the ability to easily increase capacity of a pre-existing semi-submersible structure when the need arises.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In one aspect, embodiments disclosed herein relate to multi-use offshore structures having a first configuration and a second configuration. The first configuration may include a pontoon base disposed at a lower end of the multi-use offshore structure. A deck may be disposed at an upper end of the multi-use offshore structure. A plurality of hull column structures extends between the pontoon base and the deck. The second configuration may include the pontoon base, the deck, the plurality of hull column structures of the first configuration, and a set of sponsons. Each sponson is formed to be installed on one of the hull column structures. Each of the hull column structures is designed to receive a sponson, and a deck expansion unit is connectable with the deck.

In another aspect, the first configuration has a first deck capacity and the second configuration has a second deck capacity, wherein the second deck capacity is greater than the first deck capacity.

In another aspect, one or more sponson connections are attached with a hull column structure, and each sponson includes at least one connection element for attaching with a sponson connection.

In another aspect, at least one sponson is formed to be ballasted.

In another aspect, each sponson may be installed on a hull column structure such that a bottom end of each sponson is substantially aligned with the bottom surface of the pontoon base.

In another aspect, each sponson may be installed on a hull column structure such that a top end of each sponson is substantially aligned with the top end of the hull column structure.

In another aspect, each sponson is configured to be removably installed on a hull column structure.

In another aspect, the deck expansion unit is configured to be detachably attached with the deck in the second configuration.

In another aspect, at least one module is formed to be installed on the deck expansion unit in the second configuration.

In another aspect, embodiments disclosed herein relate to methods for forming a multi-use offshore structure. The multi-use offshore structure may be designed to be expandable from a first configuration to a second configuration. The first configuration may include a pontoon base disposed at a lower end of the multi-use offshore structure. A deck is disposed at an upper end of the multi-use offshore structure, and a plurality of hull column structures extend between the pontoon base and the deck. The second configuration may include the pontoon base, the deck, the plurality of hull column structures of the first configuration, and a set of sponsons. Methods may include installing the set of sponsons on the multi-use offshore structure while in the first configuration. Each sponson may be installed on one hull column structure of the plurality of hull column structures, and a deck expansion unit may be connected to the deck, forming the second configuration.

In another aspect, the methods include determining a target increase in deck capacity for the second configuration, and based on a plurality of calculated parameters, the set of sponsons and deck expansion unit is formed to meet the target increase in deck capacity. The plurality of calculated parameters may include one or more of weight, length, width, mooring size, airgap, heave, roll, pitch, and riser porch vertical velocity.

In another aspect, the first configuration has a first deck capacity and the second configuration has a second deck capacity, wherein the second deck capacity is greater than the first deck capacity.

In another aspect, the methods include attaching each sponson to a hull column structure via a sponson connection.

In another aspect, at least one sponson is ballasted.

In another aspect, connecting the deck expansion unit to the deck may include lifting the deck expansion unit to the deck utilizing one or more cranes installed on the multi-use offshore structure.

In another aspect, each sponson may be installed on one of the hull column structures of the plurality of hull column structures such that a bottom end of each sponson is substantially aligned with the bottom surface of the pontoon base.

In another aspect, each sponson is installed on one of the hull column structures of the plurality of hull column structures such that a top end of each sponson is substantially aligned with the top end of the hull column structure.

Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

In the following detailed description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as an adjective for an element (i.e., any noun in the application). The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms “before”, “after”, “single”, and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element may encompass more than one element and succeed (or precede) the second element in an ordering of elements.

In the following description of, any component described with regard to a figure, in various embodiments disclosed herein, may be equivalent to one or more like-named components described with regard to any other figure. For brevity, descriptions of these components will not be repeated with regard to each figure. Thus, each and every embodiment of the components of each figure is incorporated by reference and assumed to be optionally present within every other figure having one or more like-named components. Additionally, in accordance with various embodiments disclosed herein, any description of the components of a figure is to be interpreted as an optional embodiment which may be implemented in addition to, in conjunction with, or in place of the embodiments described with regard to a corresponding like-named component in any other figure.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a passive soil gas sample system” includes reference to one or more of such systems.

Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

It is to be understood that one or more of the steps described herein may be omitted, repeated, and/or performed in a different order. Accordingly, the scope disclosed herein should not be considered limited to the specific arrangement of steps described herein.

In one aspect, embodiments disclosed herein generally relate to an offshore structure. More specifically, embodiments disclosed herein relate to a multi-use offshore structure. The multi-use offshore structure may be in any marine environment without departing from the scope of the present disclosure. In one aspect, embodiments disclosed herein relate to a multi-use offshore structure having a first configuration designed to be able to be converted, or expandable, to a second configuration having an increased load capacity in the future. As used herein, an increased load capacity may refer to an increase in the load capacity of the multiuse offshore structure's deck, including an increase in the amount of weight the deck may hold (topside weight increase) and/or an increase in the amount of deck area. An increased load capacity of a deck may be provided by effectively increasing the volume of hull column structures according to embodiments of the present disclosure.

In order to carry maximum cargo during an initial transit to an offshore site, some semi-submersible structures require additional stability capacity. As used herein, stability capacity may refer to hull column volume, where an increase in hull column volume may provide increased stability. For instance, in addition to an increase in topside weight and deck area, hull column volume, and therefore buoyancy of the structure, may also be increased in the second configuration. According to one or more embodiments of the present disclosure, the increased stability capacity may be obtained through the implementation of temporary sponsons, which enable a larger deck weight to be carried during transit and transition to a final operating configuration. Temporary sponsons may be used to maintain stability of the multi-use offshore structure with sufficient metacentric height during transit and transition phases of installation. Support structures for securing temporary sponsons may be attached with the hull of the multi-use offshore structure. The support structures may be used to secure temporary sponsons, which enable initial transit and transition, or permanent sponsons, which increase the operating capacity of the multi-use offshore structure. After transitioning to a sufficiently deep draft in open water, the temporary sponsons may be removed or replaced with permanent sponsons. Each of these aspects will be described in detail below.

Referring to, a multi-use offshore structurein accordance with one or more embodiments of the present disclosure is shown. Similar to the typical offshore structure depicted in, the multi-use offshore structurecomprises a deckdisposed at an upper end of the multi-use offshore structureand a plurality of hull column structures-, which act as support columns to support the deck. Each hull column structure (e.g.,) has a top end, a bottom end, and any number of sides or faces. As a non-limiting example, each hull column structure (e.g.,) is generally cylindrical with a circular cross-section. Alternatively, each hull column structure may have more than one side with a two-dimensional cross-section that is semi-circular, triangular, quadrangular, or any other suitable shape. To provide structural integrity, hull column structures may have outer wall(s) made of high-strength materials designed to withstand harsh marine conditions, hydrostatic pressure, and/or dynamic loads, such as steel, and in some embodiments may be reinforced. To provide buoyancy, the hull column structures may be hollow or contain compartments within the outer wall(s), which may store fluid ballast material (e.g., seawater), fuel, and/or other fluids. In one or more embodiments, the amount of fluid stored in hull column structures may be adjusted, e.g., using one or more fluidly connected valve(s) and pump(s) to direct fluid into/out of the column to adjust the buoyancy of the columns.

A pontoon base, having a top surface and a bottom surface, may be disposed at a lower end of the multi-use offshore structureto support the hull column structures-, such that the hull column structures-extend between the pontoon baseand the deck. The pontoon basemay include one or more connected pontoons. For example, in a polygonal-shaped pontoon base, each side of the polygon may be formed of a pontoon having an elongated hollow body, where the axial ends of each pontoon are connected to form the corners of the polygonal pontoon base. Each pontoon may be filled with ballast material (e.g., seawater, drilling fluid, sand, or a heavier solid ballast material to help lower the center of gravity, such as concrete). In addition, a portion, or all, of the pontoon basemay be underwater, as depicted in.

The pontoon basemay be generally rectangular, triangular, and/or polygonal in shape and the hull column structures-may be disposed near the corners of or at any position along the pontoon base. One of ordinary skill in the art would appreciate that the positions of the hull column structures-are not limited to the corners of the pontoon base, as the hull column structures-may be arranged in any other configuration with respect to the pontoon base. In addition, one of ordinary skill in the art would know and appreciate that the number of hull column structures is not limited to four hull column structures-, as shown, as there may be any number of hull column structures. As shown in, a portion of one or more of the hull column structures-may also be underwater.

In one or more embodiments, the multi-use offshore structurecomprises a deck expansion unitwhich is connectable with the deck, or another portion of the multi-use offshore structurein any suitable manner, to increase the deck's load capacity, thereby producing a second configuration. In one or more embodiments, a deck expansion unitmay include a plurality of support members, which may be connected to each other and connected to the existing deckto provide an increased surface area of the deck. In some embodiments, support members of a deck expansion unit may have the same configuration (e.g., elongated beams or tubular members) and/or may be formed of the same material as support members forming the existing deck. The deck expansion unitmay be lifted to the deckvia one or more cranesinstalled on the multi-use offshore structure. The deck expansion unitmay be used to support a portion and/or an expansion of the deckor may support any other equipment known in the art. For example, should it be determined that additional support is necessary for rig expansion or otherwise, the deck expansion unitmay be attached to increase the load capacity of the deckand, ultimately, allow for additional modules, such as equipment or structures (represented by), to be added or installed to the multi-use offshore structure. For example, for a production platform, a chemical injection module or a seawater injection module may be added to accommodate for changes in production operations. A deck's load capacity may be quantified, for example, by the total weight that can be supported by the deck without failure of the deck. In one or more embodiments, the deck's load capacity is quantified by the payload the deck can carry (e.g., measured in weight tonnage) without failure.

According to one or more embodiments of the present disclosure, the additional load capacity for the multi-use offshore structuremay be obtained by introducing temporary sponsons (or pencil columns), enabling a larger deck weight to be carried during transit and transition to the final operating draft. Sponsons may be used to maintain the stability of the multi-use offshore structure. The sponsons may be considered as either temporary, to enable initial transit and transition, or permanent (such as shown in), to increase the load capacity of the multi-use offshore structure, which may allow for more equipment to be carried on the deck, and which may therefore, allow for increased operations (increased operating capacity). After transitioning to a sufficiently deep draft, temporary sponsons (not shown) may be removed. Therefore, the hull column structures-may be designed to support temporary sponsons, which may then be later replaced with permanent sponsons-that provide additional stability and load capacities for the multi-use offshore structurewhen upgrades become necessary to maintain or increase production levels. Temporary sponsons may be used for a short period of time during transport, modification/repair, and/or during certain operating scenarios.

One or more, temporary or permanent, sponsons (e.g.,) may be installed on a given hull column structure (e.g.,). For example, as described in more detail below, a sponson may be mounted to a hull column structure via a frame structure and/or sponson connections. Permanent sponsons-may be designed to have larger volume capacities (e.g., longer and/or larger) than temporary sponsons. For example, in one or more embodiments, permanent sponsons-may have the same diameter as temporary sponsons, but longer lengths than temporary sponsons. The permanent sponsons may be positioned along respective hull column structures-such that the length of the permanent sponsons-may extend parallel with the length of the hull column structures to the top of the hull column structures. The diameter of a temporary sponson may be between 10 feet and 20 feet, such as 14 feet. In general, the permanent sponsons may be longer and larger in diameter than the temporary sponsons. As a non-limiting example, a permanent sponson (e.g.,) may weigh a total of about 1040 tons with a length of about 135 feet. The weight of a frame structure supporting a sponson (described below) may be about 208 tons, and the additional load capacity attained by the permanent sponson(s) may be about 1000 tons at approximately 225 feet above baseline (ABL). The increase in additional deck load capacity with the use of permanent sponsons compared to temporary sponsons may be approximately 1000 tons of payload increase. In one or more embodiments, temporary sponsons may be replaced with permanent sponsons on a multi-use offshore structure to increase its deck load capacity by between 900 to 1100 tons (compared to the deck's load capacity with only temporary sponsons).

show perspective and side views, respectively, of two exemplary sponson connections for temporary sponson, an upper sponson connectionand lower sponson connection, which are designed to connect the sponsonto a hull column structure (partially shown by). Sponson connections may be integrally formed with a hull column structure or attached to a hull column structure, e.g., by welding. In one or more embodiments, the sponson connectionsandmay be provided at selected axial locations along one side of a hull column structure, such that a sponson may be connected along the side of the hull column structure in a longitudinal orientation substantially parallel with the hull column structure. The sponsonmay be connected with the sponson connectionsandvia frame structures,. The frame structures,may be integrally formed with or connected (e.g., welded) to the sponson.show examples of sponsonsand connected frame structures,prior to engagement with the sponson connections.

show the upper sponson connectionand lower sponson connection, respectively, in more detail. In one or more embodiments, the upper sponson connectionand the lower sponson connectioneach include a compartmentand, respectively. The compartments,may be fluidly connected with a compartment in the main body of the hull column structure. Compartments in hull column structures (e.g., compartments,, and/or compartments in the main body of a hull column structure) and compartments provided in sponsons may be watertight, buoyant compartments, enabling floating self-transportation of the sponsons in a stable, vertical condition. Compartment(s) in sponsons may be defined by the sponson wall and/or internal housings made of the same materials as the hull column structures. Connecting endsmay be provided at opposite ends of each sponson connection,for connecting the sponson connections,to the frame structures,shown in.

In one or more embodiments, connecting endsof sponson connections may be formed by a plate of high-strength material such as steel having a cut-out, or receiving portion, which may be shaped to receive and bear a tubular componentof a frame structure,. For example, in, the upper sponson connectionmay have connecting endseach with a cut-outopening to a sideof the connecting end opposite from the first compartment, where the cut-outmay have a size and shape that corresponds with and/or fits around a connecting component (e.g., tubular component) of the frame structure. The upper sponson connectionmay extend horizontally along a hull column structure and receive a corresponding horizontally oriented component (e.g., tubular component) of a frame structure. With such configuration, the frame structuremay be mounted horizontally to the upper sponson connection. As shown in, the lower sponson connectionmay have connecting endseach with a cut-outopening to a bottom sideof the connecting end, where the cut-outmay have a size and shape that corresponds with and/or fits around a connecting component (e.g., tubular component) of the frame structure. The lower sponson connectionmay extend horizontally along a hull column structure and receive a corresponding horizontally oriented component (e.g., tubular component) of a frame structure. With such configuration, the frame structuremay be mounted vertically to the lower sponson connection

depict perspective and top view illustrations of examples of frame structuresand. As shown, the frame structuresandmay include a tubular componenthaving a desired diameter and length to connect with a given sponson connection. After installing a frame structure (e.g.,) on the sponson(or integrally forming a frame structure with a sponson), the sponsonmay be attached with the hull column structure via the frame structures (e.g.,) and sponson connections (e.g.,) provided along the hull column structure. For example, as shown in, receiving portions of sponson connections (e.g., the cut-outsformed in the sponson connection connecting ends) may be fitted around the tubular componentsof the frame structures,to connect the sponsons to the hull column structures.

In the examples shown in, frame structures may include one or more horizontal frame members extending along a plane perpendicular to the longitudinal axis of the sponson and one or more angled frame members extending along a plane acutely angled with the perpendicular plane and with the longitudinal axis, such that the horizontal frame member(s) and the angled frame member(s) join together via the tubular component. In the example shown in, both upper and lower frame structures,are in the same orientation and configuration, where the horizontal frame member(s) form the base of the frame structure. In the example shown in, the upper frame structureorientation and configuration may be mirrored with the lower frame structureconfiguration, such that the upper frame structure's angled member(s) form the base of the frame structure, while the lower frame structure's horizontal member(s) form the base of the frame structure.

As would be appreciated by one skilled in the art, the multi-use offshore structure is not limited to two sponson connections per hull column structure; more or less than two sponson connections may be utilized. While illustrated as such, the first compartmentconfiguration is not intended to be limited to the upper frame structureposition, and the second compartmentconfiguration is not intended to be limited to the lower frame structureposition. Further, while examples shown in the figures show sponsons connected to hull column structures in a 1:1 ratio, other embodiments may include other sponson to hull column structure ratios, e.g., two sponsons connected to one hull column structure.

According to one or more embodiments of this disclosure, different types of attachment mechanisms may be used to connect a sponson frame structure to a hull column structure sponson connection, as depicted in. In one or more embodiments, attachment mechanisms may be connected to and/or formed integrally with a frame structure. In one or more embodiments, attachment mechanisms may be connected to and/or formed integrally with a sponson connection. In one or more embodiments, attachment mechanisms may be provided separately from but connected to both the frame structure and the sponson connection.

As shown in, clampsmay be pivotably connected to a sponson connectionof a hull column structure, and may be locked in a closed configuration to cover a front opening of a receiving portion of the sponson connectionusing a vertical pin. When a connection to a temporary sponson via the clampsneeds to be removed, the vertical pinmay be removed to release the clamp. Thereafter, a tugboat may be used to gently pull the temporary sponson so that the frame structure's tubular componentslides out. With connections having a downwardly oriented receiving portion (e.g.,in), gravity may provide a net force downward to automatically slide a frame structure's tubular member out of the sponson connectionto complete the sponson removal. The sponsons may be installed pre-ballasted or empty. If empty, a sponson may be flooded from its bottom to facilitate the removal process at the offshore site.

depicts another embodiment for connecting a sponson's frame structure to a sponson connection via a latch mechanism. In this embodiment, a latchis connected with the sponson connectionvia a hinge. The hinged latchmay open to allow insertion or release of the tubular componentof the frame structure attached with a sponson. Closing the hinged latchsecures the tubular componentto the sponson connection, and thus the hull column structure. Alternatively, a sponson's frame structure may be connected to a sponson connection via a pin attachment mechanism, as shown in. In this embodiment, a plurality of pins(e.g., two pins) extend through a top and bottom side of the sponson connection. Following insertion of the tubular componentwithin the receiving portion of the sponson connection, the pinsmay be inserted through aligned openings (or holes) within the sponson connection. The pinssecure the tubular componentinto its proper position within the sponson connection, thereby securing the sponson to the hull column structure.

Embodiments of this disclosure may further include determining a target increase in deck capacity for the second configuration. For instance, based on a plurality of calculated parameters related to components of the multi-use offshore structure, one or more of the temporary sponsons, permanent sponsons, deck, deck expansion unit, frame structures, and any connecting elements may be designed to meet the target increase, such as 1000 megatonnes (MT), in deck capacity. Non-limiting examples of parameters that may be calculated and adjusted include weight, length, width, mooring size, airgap, heave, roll, pitch, and riser porch vertical velocity.

Requiring additional deck capacity at an offshore structure is a recurring problem. The multi-use offshore structure according to embodiments of this disclosure is designed to be converted from a first configuration having an initial deck load capacity to a second configuration with a deck load capacity greater than the initial deck load capacity. Designing and installing support structures that accommodate both temporary sponsons as well as larger, permanent sponsons provides a cost-effective and time-efficient method for increasing the operating capacity of the multi-use offshore structure.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. Further, although multiple dependent claims are not introduced, it would be apparent to one of ordinary skill that the subject matter of the dependent claims of one or more embodiments may be combined with other dependent claims.