Patent Description:
Advances in the petroleum industry have allowed access to oil and gas drilling locations and reservoirs that were previously inaccessible due to technological limitations. For example, technological advances have allowed drilling of offshore wells at increasing water depths and in increasingly harsh environments, permitting oil and gas resource owners to successfully drill for otherwise inaccessible energy resources. Likewise, drilling advances have allowed for increased access to land based reservoirs.

However, offshore drilling and production facilities (e.g., offshore platforms) may encounter problems not typically found with land based drilling and production facilities. For example, when operating in water, lateral positioning techniques and systems (e.g., thrusters or similar devices) may be utilized to counteract lateral movement caused by currents, waves, and the like. Additionally, stability of the offshore platforms is to be maintained. One technique for maintaining the stability of an offshore platform is to design the platform to have a sufficient waterplane area (e.g., an enclosed area of the facility hull at the waterline) to allow for stability of the offshore platform. However, while increasing the waterplane area of an offshore platform may increase its stability (e.g., its ability to resist sway (lateral/side-to-side motion) and surge (longitudinal /front-and-back motion) imparted by maritime conditions), increasing the waterplane area of the offshore platform may also increase its susceptibility to heave (e.g., vertical/up-and-down motion). Solutions to address heave in the offshore platform and/or affecting components thereon are desirable.

When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements.

Systems and techniques for stabilizing an drill floor of an offshore platform, such as a semi-submersible platform, a drillship, a spar platform, a floating production system, or the like, are set forth below. The offshore platform may include a drill floor that is suspended above a deck of the offshore platform. The drill floor can be restrained from horizontal movements with respect to the deck of the offshore platform and the drill floor can move vertically towards and away from the deck of the offshore platform in a controlled manner to resists heave (e.g., vertical/up-and-down motion) relative to a seafloor. In some embodiments, an actuation system that can, for example, include one or more drawworks, may be utilized to affect control of the vertical movement of the drill floor with respect to the deck of the offshore platform.

With the foregoing in mind, <FIG> illustrates an offshore platform <NUM> as a drillship. Although the presently illustrated embodiment of an offshore platform <NUM> is a drillship (e.g., a ship equipped with a drilling system and engaged in offshore oil and gas exploration and/or well maintenance or completion work including, but not limited to, casing and tubing installation, subsea tree installations, and well capping), other offshore platforms <NUM> such as a semi-submersible platform, a jack up drilling platform, a spar platform, a floating production system, or the like may be substituted for the drillship. Indeed, while the techniques and systems described below are described in conjunction with a drillship, the techniques and systems are intended to cover at least the additional offshore platforms <NUM> described above. These techniques may also apply to at least vertical drilling or production operations (e.g., having a rig in a primarily vertical orientation drill or produce from a substantially vertical well) and/or directional drilling or production operations (e.g., having a rig in a primarily vertical orientation drill or produce from a substantially non-vertical or slanted well or having the rig oriented at an angle from a vertical alignment to drill or produce from a substantially non-vertical or slanted well).

As illustrated in <FIG>, the offshore platform <NUM> includes a riser string <NUM> extending therefrom. The riser string <NUM> may include a pipe or a series of pipes that connect the offshore platform <NUM> to the seafloor <NUM> via, for example, a BOP <NUM> that is coupled to a wellhead <NUM> on the seafloor <NUM>. In some embodiments, the riser string <NUM> may transport produced hydrocarbons and/or production materials between the offshore platform <NUM> and the wellhead <NUM>, while the BOP <NUM> may include at least one BOP stack having at least one valve with a sealing element to control wellbore fluid flows. In some embodiments, the riser string <NUM> may pass through an opening (e.g., a moonpool) in the offshore platform <NUM> and may be coupled to drilling equipment of the offshore platform <NUM>. As illustrated in <FIG>, it may be desirable to have the riser string <NUM> positioned in a vertical orientation between the wellhead <NUM> and the offshore platform <NUM> to allow a drill string made up of drill pipes <NUM> to pass from the offshore platform <NUM> through the BOP <NUM> and the wellhead <NUM> and into a wellbore below the wellhead <NUM>. Also illustrated in <FIG> is a drilling rig <NUM> (e.g., a drilling package or the like) that may be utilized in the drilling and/or servicing of a wellbore below the wellhead <NUM>.

<FIG> illustrates in greater detail components of the drilling rig <NUM> as well as additional components used in various operations, such as a tripping operation. As illustrated, a tripping apparatus <NUM> is positioned on the drilling floor <NUM> in the drilling rig <NUM> above a deck <NUM>. The drilling rig <NUM> may include one or more of, for example, the tripping apparatus <NUM>, floor slips <NUM> positioned in rotary table <NUM>, drawworks <NUM>, a crown block <NUM>, a travelling block <NUM>, a top drive <NUM>, an elevator <NUM>, and a tubular handling apparatus <NUM>. The tripping apparatus <NUM> may operate to couple and decouple tubular segments (e.g., drill pipe <NUM> to and from a drill string) while the floor slips <NUM> may operate to close upon and hold a drill pipe <NUM> and/or the drill string passing into the wellbore. The rotary table <NUM> may be a rotatable portion of the drilling floor <NUM> that may operate to impart rotation to the drill string either as a primary or a backup rotation system (e.g., a backup to the top drive <NUM>).

The drawworks <NUM> may be a large spool that is powered to retract and extend line <NUM> (e.g., wire cable or drill line) over a crown block <NUM> (e.g., a vertically stationary set of one or more pulleys or sheaves through which the line <NUM> is threaded) and a travelling block <NUM> (e.g., a vertically movable set of one or more pulleys or sheaves through which the line <NUM> is threaded) to operate as a block and tackle system for movement of the top drive <NUM>, the elevator <NUM>, and any tubular member (e.g., drill pipe <NUM>) coupled thereto. The top drive <NUM> may be a device that provides torque to (e.g., rotates) the drill string as an alternative to the rotary table <NUM> and the elevator <NUM> may be a mechanism that may be closed around a drill pipe <NUM> or other tubular members (or similar components) to grip and hold the drill pipe <NUM> or other tubular members while those members are moving vertically (e.g., while being lowered into or raised from the wellbore). The tubular handling apparatus <NUM> may operate to retrieve a tubular member from a storage location <NUM> (e.g., a pipe stand) and position the tubular member during tripping-in to assist in adding a tubular member to a tubular string. Likewise, the tubular handling apparatus <NUM> may operate to retrieve a tubular member from a tubular string and transfer the tubular member to a storage location <NUM> (e.g., a pipe stand) during tripping-out to remove the tubular member from the tubular string.

For example, during a tripping-in operation, the tubular handling apparatus <NUM> may position a first tubular segment <NUM> (e.g., a first drill pipe <NUM>) so that the tubular segment <NUM> may be grasped by the elevator <NUM>. The elevator <NUM> may be lowered, for example, via the block and tackle system towards the tripping apparatus <NUM> to be coupled to a second tubular segment <NUM> (e.g., a second drill pipe <NUM>) as part of a drill string. As illustrated in <FIG>, the tripping apparatus <NUM> may be or may include a roughneck that may operate to selectively make-up and break-out a threaded connection between tubular segments <NUM> and <NUM> in a tubular string. In some embodiments, the tripping apparatus <NUM> may include one or more of fixed jaws <NUM>, makeup/breakout jaws <NUM>, and a spinner <NUM>. In some embodiments, the fixed jaws <NUM> may be positioned to engage and hold the second (lower) tubular segment <NUM> below a threaded joint <NUM> thereof. In this manner, when the first (upper) tubular segment <NUM> is positioned coaxially with the second tubular segment <NUM> in the tripping apparatus <NUM>, the second tubular segment <NUM> may be held in a stationary position to allow for the connection of the first tubular segment <NUM> and the second tubular segment (e.g., through connection of the threaded joint <NUM> of the second tubular segment <NUM> and a threaded joint <NUM> of the first tubular segment <NUM>, illustrated in <FIG>).

To facilitate this connection, the spinner <NUM> and the makeup/breakout jaws <NUM> illustrated in <FIG> may provide rotational torque. For example, in making up the connection, the spinner <NUM> may engage the first tubular segment <NUM> and provide a relatively high-speed, low-torque rotation to the first tubular segment <NUM> to connect the first tubular segment <NUM> to the second tubular segment <NUM>. Likewise, the makeup/breakout jaws <NUM> may engage the first tubular segment <NUM> and may provide a relatively low-speed, high-torque rotation to the first tubular segment <NUM> to provide, for example, a rigid connection between the tubular segment <NUM> and <NUM>. Furthermore, in breaking-out the connection, the makeup/breakout jaws <NUM> may engage the first tubular segment <NUM> and impart a relatively low-speed, high-torque rotation on the first tubular segment <NUM> to break the rigid connection. Thereafter, the spinner <NUM> may provide a relatively high-speed, low-torque rotation to the first tubular segment <NUM> to disconnect the first tubular segment <NUM> from the second segment <NUM>.

In some embodiments, the tripping apparatus <NUM> may further include a mud bucket <NUM> that may operate to capture drilling fluid, which might otherwise be released during, for example, the break-out operation. In this manner, the mud bucket <NUM> may operate to prevent drilling fluid from spilling onto drill floor <NUM>. In some embodiments, the mud bucket <NUM> may include one or more seals that aid in fluidly sealing the mud bucket <NUM> as well as a drain line that operates to allow drilling fluid contained within mud bucket <NUM> to return to a drilling fluid reservoir.

Returning to <FIG>, one or more sensors <NUM> may be provided in conjunction with the drilling rig <NUM>. In some embodiments, the one or more sensors <NUM> may be utilized in conjunction with a make-up (e.g., a tripping-in) and a break-out (e.g., a tripping-out) operation. In one embodiment, the one or more sensors <NUM> may include, but are not limited to, cameras (e.g., high frame rate cameras), lasers (e.g., multi-dimensional lasers), transducers (e.g., ultrasound transducers), electrical and or magnetic characteristic sensors (e.g., sensors that can measure/infer capacitance, inductance, magnetism, or the like), chemical sensors, metallurgical detection sensors, or the like. In some embodiments, the one or more sensors <NUM> may also be proximity sensors or other sensors (e.g., a rotational sensor such as an optical encoder, magnetic speed sensor, a reflective sensor, a hall effect sensor, a load cell such as an inline load cell) to detect operational characteristics of the drawworks <NUM> (e.g., rotation of a drum, speed of a drum, tension on line <NUM>, or the like) that may include or be coupled to a transmitter. In some embodiments, the one or more sensors <NUM> may generate a signal indicative of operational characteristics of the drawworks <NUM> and may transmit, themselves or via a transmitter coupled thereto, a signal (wirelessly or via a physical connection) indicative of operational characteristic of the drawworks <NUM> to the computer system <NUM>. This signal may be used to determine the location of an object (e.g., a drill pipe <NUM>, the top drive <NUM>, the elevator <NUM>, the threaded joint <NUM> of a drill pipe <NUM>, or the threaded joint <NUM> of a drill pipe <NUM>) by the computer system <NUM>, as the location of an object may be directly related to the operation of the drawworks <NUM> (e.g., the tension of the line <NUM> or an amount of rotation of a drum causing line <NUM> to be extended from the drawworks <NUM>, which defines the location of the object suspended from the block and tackle system). The determined location of an object may be useful, for example, to determine and/or control where and when to move the tripping apparatus <NUM> into position (e.g., tool joint recognition) to perform a tripping operation. Likewise, the computer system <NUM> can monitor a tension value of the line <NUM> and cause the tension to be maintained at a particular value or within a range of values to aid maintain a desired tension of the line <NUM>.

In some embodiments, the computing system <NUM> may be communicatively coupled to a separate main control system, for example, a control system in a driller's cabin that may provide a centralized control system for drilling controls, automated pipe handling controls, and the like. In other embodiments, the computing system <NUM> may be a portion of the main control system (e.g., the control system present in the driller's cabin).

<FIG> illustrates the computing system <NUM>. It should be noted that the computing system <NUM> may be a standalone unit (e.g., a control monitor) that may operate to generate output control signals (e.g., to form a control system). Likewise, the computing system <NUM> may be configured to operate in conjunction with the tripping apparatus <NUM>, one or more of the drawworks <NUM>, the top drive <NUM>, and the elevator <NUM>, and/or the tubular handling apparatus <NUM>. The computing system <NUM> may be a general purpose or a special purpose computer that includes a processing device <NUM>, such as one or more application specific integrated circuits (ASICs), one or more processors, or another processing device that interacts with one or more tangible, non-transitory, machine-readable media (e.g., memory <NUM>) of the computing system <NUM>, which may operate to collectively store instructions executable by the processing device <NUM> to perform the methods and actions described herein. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by the processing device <NUM>. In some embodiment, the instructions executable by the processing device <NUM> are used to generate, for example, control signals to be transmitted to, for example, one or more of the tripping apparatus <NUM> (e.g., one or more of the fixed jaws <NUM>, the makeup/breakout jaws <NUM>, and the spinner <NUM>), the tubular handling apparatus <NUM>, one or more of the drawworks <NUM>, the top drive <NUM>, and the elevator <NUM> or a controller thereof, and/or a main control system (e.g., to be utilized in the control of the tripping apparatus <NUM>, the fixed jaws <NUM>, the makeup/breakout jaws <NUM>, the spinner <NUM>, the drawworks <NUM>, the top drive <NUM>, the elevator <NUM>, and/or the tubular handling apparatus <NUM>) to operate in a manner described herein.

The computing system <NUM> may operate in conjunction with software systems implemented as computer executable instructions stored in a non-transitory machine readable medium of computing system <NUM>, such as memory <NUM>, a hard disk drive, or other short term and/or long term storage. Particularly, the processing device <NUM> may operate in conjunction with software systems implemented as computer executable instructions (e.g., code) stored in a non-transitory machine readable medium of computing system <NUM>, such as memory <NUM>, that may be executed to receive information (e.g., signals or data) related to sensitivities of surge and/or swab pressures characteristics as well as well pressure characteristics. This information can be used by the computing system <NUM> (e.g., by the processing device <NUM> executing computer executable instructions stored in memory <NUM>) to generate or otherwise calculate a tripping schedule that may be utilized to limiting tripping operation speeds to predetermined levels at predetermined times and/or well depths. Additionally, this determined tripping schedule can be used to initiate or control movement and/or operation of the tripping apparatus <NUM> and/or the associated tripping elements (e.g., the drawworks <NUM>, the top drive <NUM>, the elevator <NUM>, and/or the tubular handling apparatus <NUM>) to facilitate a make-up or break-out (e.g., tripping) operation by the computing system <NUM>, the main control system, or by local controller(s) of the tripping apparatus <NUM> and/or the associated tripping elements (e.g., the drawworks <NUM>, the top drive <NUM>, the elevator <NUM>, and/or the tubular handling apparatus <NUM>).

In some embodiments, the computing system <NUM> may also include one or more input structures <NUM> (e.g., one or more of a keypad, mouse, touchpad, touchscreen, one or more switches, buttons, or the like) to allow a user to interact with the computing system <NUM>, for example, to start, control, or operate a graphical user interface (GUI) or applications running on the computing system <NUM> and/or to start, control, or operate the tripping apparatus <NUM> (e.g., one or more of the fixed jaws <NUM>, the makeup/breakout jaws <NUM>, and the spinner <NUM>), the tubular handling apparatus <NUM>, and/or additional systems of the drilling rig <NUM>. Additionally, the computing system <NUM> may include a display <NUM> that may be a liquid crystal display (LCD) or another type of display that allows users to view images generated by the computing system <NUM>. The display <NUM> may include a touch screen, which may allow users to interact with the GUI of the computing system <NUM>. Likewise, the computing system <NUM> may additionally and/or alternatively transmit images to a display of a main control system, which itself may also include a processing device <NUM>, a non-transitory machine readable medium, such as memory <NUM>, one or more input structures <NUM>, a display <NUM>, and/or a network interface <NUM>.

Returning to the computing system <NUM>, as may be appreciated, the GUI may be a type of user interface that allows a user to interact with the computer system <NUM> and/or the computer system <NUM> and one or more sensors that transmit data to the computing system through, for example, graphical icons, visual indicators, and the like. Additionally, the computer system <NUM> may include network interface <NUM> to allow the computer system <NUM> to interface with various other devices (e.g., electronic devices). The network interface <NUM> may include one or more of a Bluetooth interface, a local area network (LAN) or wireless local area network (WLAN) interface, an Ethernet or Ethernet based interface (e.g., a Modbus TCP, EtherCAT, and/or ProfiNET interface), a field bus communication interface (e.g., Profibus), a/or other industrial protocol interfaces that may be coupled to a wireless network, a wired network, or a combination thereof that may use, for example, a multi-drop and/or a star topology with each network spur being multi-dropped to a reduced number of nodes.

In some embodiments, one or more of the tripping apparatus <NUM> (and/or a controller or control system associated therewith), the tubular handling apparatus <NUM> (and/or a controller or control system associated therewith), associated tripping elements (e.g., the drawworks <NUM>, the top drive <NUM>, the elevator <NUM>, and/or the tubular handling apparatus <NUM>), and/or a main control system may each be a device that can be coupled to the network interface <NUM>. In some embodiments, the network formed via the interconnection of one or more of the aforementioned devices should operate to provide sufficient bandwidth as well as low enough latency to exchange all required data within time periods consistent with any dynamic response requirements of all control sequences and closed-loop control functions of the network and/or associated devices therein. It may also be advantageous for the network to allow for sequence response times and closed-loop performances to be ascertained, the network components should allow for use in oilfield/drillship environments (e.g., should allow for rugged physical and electrical characteristics consistent with their respective environment of operation inclusive of but not limited to withstanding electrostatic discharge (ESD) events and other threats as well as meeting any electromagnetic compatibility (EMC) requirements for the respective environment in which the network components are disposed). The network utilized may also provide adequate data protection and/or data redundancy to ensure operation of the network is not compromised, for example, by data corruption (e.g., through the use of error detection and correction or error control techniques to obviate or reduce errors in transmitted network signals and/or data).

The computing system <NUM> may operate in conjunction with additional embodiments of drilling rigs. For example, <FIG> illustrates another embodiment of a drilling rig <NUM> that may be utilized in an operation, such as a tripping operation consistent with embodiments of the present disclosure and that may operate in conjunction with the computing system <NUM> of <FIG>. As illustrated in <FIG>, the tripping apparatus <NUM> is positioned above drill floor <NUM> in the drilling rig <NUM>. However, as will be discussed in greater detail below, the tripping apparatus <NUM> may be moved towards and away from the drill floor <NUM> during a tripping operation. As illustrated, the drilling rig <NUM> may include one or more of, for example, the tripping apparatus <NUM>, a movable platform <NUM> (that may include floor slips <NUM> positioned in rotary table <NUM>, as illustrated in <FIG>), drawworks <NUM>, a crown block <NUM>, a travelling block <NUM>, a top drive <NUM>, an elevator <NUM>, and a tubular handling apparatus <NUM>. The tripping apparatus <NUM> may operate to couple and decouple tubular segments (e.g., couple and decouple drill pipe <NUM> to and from a drill string) while the floor slips <NUM> may operate to close upon and hold a drill pipe <NUM> and/or the drill string passing into the wellbore. The rotary table <NUM> may be a rotatable portion that can be locked into positon co-planar with the drill floor <NUM> and/or above the drill floor <NUM>. The rotary table <NUM> can, for example, operate to impart rotation to the drill string either as a primary or a backup rotation system (e.g., a backup to the top drive <NUM>) as well as utilize its floor slips <NUM> to support tubular segments, for example, during a tripping operation or may be a false rotary table that does not impart rotation to the drill string while still allowing for support of tubular segments utilizing its floor slips <NUM>.

The drawworks <NUM> may be a large spool that is powered to retract and extend line <NUM> (e.g., wire cable or drill line) over a crown block <NUM> (e.g., a vertically stationary set of one or more pulleys or sheaves through which the line <NUM> is threaded) and a travelling block (e.g., a vertically movable set of one or more pulleys or sheaves through which the line <NUM> is threaded) to operate as a block and tackle system for movement of the top drive <NUM>, the elevator <NUM>, and any tubular segment (e.g., drill pipe <NUM>) coupled thereto. In some embodiments, the top drive <NUM> and/or the elevator <NUM> may be referred to as a tubular support system or the tubular support system may also additionally include the block and tackle system described above.

The top drive <NUM> may be a device that provides torque to (e.g., rotates) the drill string as an alternative to the rotary table <NUM> and the elevator <NUM> may be a mechanism that may be closed around a drill pipe <NUM> or other tubular segments (or similar components) to grip and hold the drill pipe <NUM> or other tubular segments while those segments are moving vertically (e.g., while being lowered into or raised from a wellbore) or directionally (e.g., during slant drilling). The tubular handling apparatus <NUM> may operate to retrieve a tubular segment from a storage location <NUM> (e.g., a pipe stand) and position the tubular segment during tripping-in to assist in adding a tubular segment to a tubular string. Likewise, the tubular handling apparatus <NUM> may operate to retrieve a tubular segment from a tubular string and transfer the tubular segment to a storage location (e.g., a pipe stand) during tripping-out to remove the tubular segment from the tubular string.

During a tripping-in operation, the tubular handling apparatus <NUM> may position a tubular segment <NUM> (e.g., a drill pipe <NUM>) so that the segment <NUM> may be grasped by the elevator <NUM>. Elevator <NUM> may be lowered, for example, via the block and tackle system towards the tripping apparatus <NUM> to be coupled to tubular segment <NUM> (e.g., a drill pipe <NUM>) as part of a drill string. In some embodiments, the tripping apparatus <NUM> may operate as discussed in conjunction with <FIG> above during a tripping operation. However, while tripping operations involving singular tubular segments <NUM> and <NUM> (e.g., drill pipe <NUM>) has been discussed with respect to <FIG>, it is envisioned that a stand of tubular segments <NUM>, <NUM> (e.g., two, three, or more tubular segments <NUM>, <NUM> coupled together) may be the tubular segments being tripped-in or tripped-out. Additionally, continuous tripping operations (tripping tubular segments without halting the movement of the tubular string at a fixed position) may be facilitated and/or accelerated through the inclusion of the movable platform <NUM>.

The movable platform <NUM> may be raised and lowered with a cable and sheave arrangement (e.g., similar to the block and tackle system for movement of the top drive <NUM>) that may include a winch or other drawworks element positioned on the drill floor <NUM> or elsewhere on the offshore platform <NUM> or the drilling rig <NUM>. The winch or other drawworks element may be a spool that is powered to retract and extend a line (e.g., a wire cable) over a crown block (e.g., a stationary set of one or more pulleys or sheaves through which the line <NUM> is threaded) and a travelling block (e.g., a movable set of one or more pulleys or sheaves through which the line <NUM> is threaded) to operate as a block and tackle system for movement of the movable platform <NUM> and, thus, the rotary table <NUM> therein and the tripping apparatus <NUM> thereon. Additionally and/or alternatively, one or more direct acting cylinders, a suspended winch and cable system, or other internal or external actuation systems may be used to move the movable platform <NUM> along one or more supports <NUM>.

In some embodiments, the one or more supports <NUM> may be one or more guide mechanisms (e.g., guide tracks, such as top drive dolly tracks) that provide support (e.g., lateral support) to the movable platform <NUM> while allowing for movement towards and away from the drill floor <NUM>. One or more lateral supports of the movable platform <NUM> may be used to couple the movable platform <NUM> to the one or more supports <NUM>. For example, one more lateral supports of the movable platform <NUM> may be, for example, pads that may be made of Teflon-graphite material or another low-friction material (e.g., a composite material) that allows for motion of the movable platform <NUM> relative to drill floor <NUM> and/or the tubular segment support system with reduced friction characteristics. In addition to, or in place of the aforementioned pads, other lateral supports of the movable platform <NUM> including bearing or roller type supports (e.g., steel or other metallic or composite rollers and/or roller bearings) may be utilized. The lateral supports of the movable platform <NUM> may allow the movable platform <NUM> to interface with a guide (e.g., guide tracks, such as top drive dolly tracks) so that the movable platform <NUM> is movably coupled to the one or more supports <NUM>. Accordingly, the movable platform <NUM> may be movably coupled to one or more supports <NUM> to allow for movement of the movable platform <NUM> (e.g., towards and away from the drill floor <NUM> and/or the tubular segment support system while maintaining contact with the guide tracks or other guides) during a tripping operation (e.g., a continuous tripping operation).

<FIG> illustrates an embodiment in which a drilling rig <NUM> similar to those described above can be utilized. For example, the drilling rig <NUM> may be substantially similar to the drilling rig <NUM> or the drilling rig <NUM> as described above. However, the drilling rig <NUM> may include an active heave compensation system <NUM>, as described herein. The active heave compensation system <NUM> includes, for example, one or more active heave drawworks <NUM> and a fixed frame <NUM>, which circumscribes at least one of the drill floor <NUM> and a derrick <NUM>. In some embodiments, the one or more active heave drawworks <NUM> can be defined as an actuation system and/or the actuation system can employ other lifting components in place of or in addition to the one or more active heave drawworks <NUM>. The one or more active heave drawworks <NUM> may be a large spool that is powered to retract and extend a line <NUM> (e.g., wire cable or drill line) over a set of one or more pulleys or sheaves through which the line <NUM> is threaded. The set of one or more pulleys or sheaves may be a cable and sheave arrangement similar to the block and tackle system described above and the line <NUM> may be a single cable routed in the manner described below from a first active heave drawworks <NUM> to a second active heave drawworks <NUM> via the cable and sheave arrangement. Likewise, the line <NUM> may be a single cable routed in the manner described below via the cable and sheave arrangement from a first active heave drawworks <NUM> to a connector (e.g., an anchor blot, eye bolt, screw eye, padeye, or another connector) coupled to, on, or in deck <NUM>, which operates as an anchor point. In other embodiments, the active heave and compensation system <NUM> can include an actuation system that includes elements that operate in parallel, for example, a first line <NUM> as a single cable routed in the manner described below from a first active heave drawworks <NUM> to a second active heave drawworks <NUM> via the cable and sheave arrangement and a second line <NUM> as a second single cable routed in the manner described below from a third active heave drawworks <NUM> to a fourth active heave drawworks <NUM> via the cable and sheave arrangement (or a second cable and sheave arrangement). Likewise, a line <NUM> may be a single cable routed in the manner described below via the cable and sheave arrangement from a first active heave drawworks <NUM> to a connector (e.g., an anchor blot, eye bolt, screw eye, padeye, or another connector) coupled to, on, or in deck <NUM>, which operates as an anchor point and a second line <NUM> may be a second single cable routed in the manner described below via the cable and sheave arrangement (or a second cable and sheave arrangement) from a second active heave drawworks <NUM> to a second connector (or the first connector) coupled to, on, or in deck <NUM>, which operates as an anchor point. In this manner, parallel operations can be undertaken using the actuation system. Additionally, the active heave compensation system <NUM> may include the cable and sheave arrangement (e.g., the set of one or more pulleys or sheaves).

In some embodiments, the cable and sheave arrangement (e.g., the set of one or more pulleys or sheaves) coupled to the one or more active heave drawworks <NUM> may include, for example, one or more upper sheaves <NUM> disposed on an upper or topmost portion of the fixed frame <NUM>. In one embodiment, a first upper sheave <NUM> is disposed on a topmost beam of the fixed frame <NUM> at a first corner of an upper portion of the fixed frame <NUM> and a second upper sheave <NUM> is disposed on the topmost beam of the fixed frame <NUM> at a second corner of an upper portion of the fixed frame <NUM>. In some embodiments, there is an upper sheave <NUM> that corresponds to each active heave drawworks <NUM>. Each of the one or more upper sheaves <NUM> may be disposed at a respective corner of the upper or topmost portion of the fixed frame <NUM> (e.g., a first upper sheave <NUM> disposed at a first upper corner of the fixed frame <NUM> and a second upper sheave <NUM> disposed at a second upper corner of the fixed frame <NUM>), whereby the first and the second upper corners of the fixed frame <NUM> on which the upper sheaves <NUM> are disposed are adjacent to the active heave drawworks <NUM> (or physical connection or anchor point). The one or more upper sheaves <NUM> may receive the line <NUM> directly from its respective active heave drawworks <NUM> (or from a physical connection or anchor point).

Additionally, the cable and sheave arrangement (e.g., the set of one or more pulleys or sheaves) may further include one or more lower sheaves <NUM> and one or more lower sheaves <NUM>. The one or more lower sheaves <NUM> may be coupled to an underside of the upper or topmost portion of the fixed frame <NUM>. In this manner, the one or more lower sheaves <NUM> may be disposed generally below (towards the deck <NUM>) the one or more upper sheaves <NUM>. For example, the one or more lower sheaves <NUM> can be disposed under (on a bottom side towards the deck <NUM>) a beam or other support on which the one or more upper sheaves <NUM> is disposed. In some embodiments, one or more than one (e.g., two, three, or more) sheaves as the one or more lower sheaves <NUM> may be disposed below each of the one or more upper sheaves <NUM>. For example, one or more lower sheaves <NUM> may be disposed at a respective corner of the upper or topmost portion of the fixed frame <NUM> (e.g., a first one or more lower sheaves <NUM> can be disposed at a first upper corner of the fixed frame <NUM> under a beam or other support on which a first upper sheave <NUM> is disposed, i.e., below the first upper sheave <NUM>, and a second one or more lower sheaves <NUM> can be disposed at a second upper corner of the fixed frame <NUM> under a beam or other support on which a second upper sheave <NUM> is disposed, i.e., below the second upper sheave <NUM>), whereby the first and the second upper corners of the fixed frame <NUM> on which the lower sheaves <NUM> are disposed are adjacent to the active heave drawworks <NUM> (or physical connection or anchor point).

Similarly, the one or more lower sheaves <NUM> may be coupled to the underside of the upper or topmost portion of the fixed frame <NUM>. In some embodiments, one or more than one (e.g., two, three, or more) sheaves as the one or more lower sheaves <NUM> may be disposed along the underside of the upper or topmost portion of the fixed frame <NUM>. The one or more lower sheaves <NUM> may also be disposed generally below (towards the deck <NUM>) the one or more upper sheaves <NUM>. For example, the one or more lower sheaves <NUM> can be disposed under (on a bottom side towards the deck <NUM>) a beam or other support on which the one or more upper sheaves <NUM> is disposed. However, the one or more lower sheaves <NUM> may also be separated from the one or more upper sheaves <NUM> by the length of the fixed frame <NUM>.

For example, one or more lower sheaves <NUM> may be disposed at a respective corner of the upper or topmost portion of the fixed frame <NUM> (e.g., a first one or more lower sheaves <NUM> can be disposed at a third upper corner of the fixed frame <NUM> under a beam or other support on which a first upper sheave <NUM> is disposed, i.e., below the first upper sheave <NUM> and at a distance of the length of the fixed frame <NUM> from the first upper sheave <NUM>). Likewise, for example, a second one or more lower sheaves <NUM> can be disposed at a separate respective corner of the of the upper or topmost portion of the fixed frame <NUM> (e.g., a second one or more lower sheaves <NUM> can be disposed at a fourth upper corner of the fixed frame <NUM> under a beam or other support on which a first upper sheave <NUM> is disposed, i.e., below a second upper sheave <NUM> and at a distance of the length of the fixed frame <NUM> from the second upper sheave <NUM>). Thus, a first one or more lower sheaves <NUM> and a first one or more of the lower sheaves <NUM> may be disposed on or coupled to the underside of the upper or topmost portion of the fixed frame <NUM> at a distance of the length of the fixed frame <NUM> so that each of the first one or more lower sheaves <NUM> and the first one or more of the lower sheaves <NUM> are disposed in respective upper corners of the fixed frame <NUM>. Likewise, a second one or more lower sheaves <NUM> and a second one or more of the lower sheaves <NUM> may be disposed on or coupled to the underside of the upper or topmost portion of the fixed frame <NUM> at a distance of the length of the fixed frame <NUM> so that each of the first one or more lower sheaves <NUM> and the first one or more of the lower sheaves <NUM> are disposed in respective upper corners of the fixed frame <NUM>. Thus, in one embodiment, each upper corner of the fixed frame <NUM> may have a set of one or more lower sheaves <NUM> or one or more lower sheaves <NUM> disposed thereat.

The active heave compensation system <NUM> further includes, for example, a heave compensation frame <NUM>. The heave compensation frame <NUM> may be a structure that includes the drill floor <NUM> as a bottom portion, one or more structural beams <NUM> disposed, for example, along edges and/or at corners of the drill floor <NUM> and extending vertically (e.g., perpendicular to) away from the drill floor <NUM>, and one or more upper beams <NUM> that extend horizontally (e.g., perpendicular to the one or more structural beams <NUM>) and are coupled to the structural beams <NUM>. The heave compression frame <NUM> can be coupled a tubular string extending to the seafloor <NUM> and/or into a wellbore below the seafloor <NUM>. For example, a drill string made up of drill pipes <NUM> may be held by the floor slips <NUM> of the drill floor <NUM>, whereby the drill string extends to the seafloor <NUM> and/or into a wellbore below the seafloor <NUM>. In some embodiments, the derrick <NUM> is disposed on the one or more upper beams <NUM>. The heave compensation frame <NUM> is sized to fit within the fixed frame <NUM>. The heave compensation frame <NUM> may be slidingly coupled to the fixed frame <NUM> such that the heave compensation frame <NUM> can move towards and away from the deck <NUM> while the fixed frame <NUM> remains stationary with respect to the deck <NUM>. The fixed frame <NUM> may also restrict lateral movement (e.g., movement in a horizontal direction along the deck <NUM>) of the heave compensation frame <NUM>. In this manner, the heave compensation frame <NUM> is slidingly coupled to the fixed frame <NUM> (e.g., the heave compensation frame <NUM> is able to move in one plane with respect to the fixed frame <NUM> while being restricted from movement in a second plane with respect to the fixed frame).

In some embodiments, one or more guides (e.g., tracks or the like) may be used to couple the heave compensation frame <NUM> to the fixed frame <NUM>. For example, an upper guide <NUM> may be disposed along each vertical support column of the fixed frame <NUM> and a lower guide <NUM> may be disposed along each vertical support column of the fixed frame <NUM> at a location below (e.g., towards the deck <NUM>) the upper guide <NUM>. In some embodiments, there may be one or more guides (e.g., an upper guide <NUM> and a lower guide <NUM>) that correspond to each structural beam <NUM> of the heave compensation frame <NUM>. In some embodiments, one or more lateral supports may be coupled to one or more of the drill floor <NUM>, the one or more structural beams <NUM>, and/or the one or more upper beams <NUM> to couple the heave compensation frame <NUM> to the fixed frame. In some embodiments, the one or more guides and the one or more lateral supports can be male and female connectors or other types of connectors. For example, the one or more lateral supports may be, for example, pads that may be made of Teflon-graphite material or another low-friction material (e.g., a composite material) that allows for motion of the heave compensation frame <NUM> relative to drill floor <NUM> with reduced friction characteristics. In addition to, or in place of the aforementioned pads, other lateral supports including bearing or roller type supports (e.g., steel or other metallic or composite rollers and/or roller bearings) may be utilized to allow for horizontal load transfer between the heave compensation frame <NUM> and the fixed frame <NUM> with minimal resistance to vertical motion. The one or more lateral supports may allow the heave compensation frame <NUM> to interface with a the one or more guides so that the heave compensation frame <NUM> is movably coupled to the fixed frame <NUM>. In this manner, the heave compensation frame <NUM> may be movably coupled to the fixed frame <NUM> to allow for movement of the heave compensation frame <NUM> (e.g., towards and away from the drill floor <NUM> while maintaining contact with the guide tracks or other support element of the fixed frame).

In some embodiments, the heave compensation frame <NUM> may be raised and lowered with the cable and sheave arrangement via one or more of the active heave drawworks <NUM>. One technique for connecting the cable and sheave arrangement is described below; however it should be appreciated that alternate configurations are contemplated. In one embodiment, the line <NUM> may be routed directly from a first active heave drawworks <NUM> of the one or more active heave drawworks <NUM> to a first one of the one or more upper sheaves <NUM> and passed to a connector (e.g., an anchor blot, eye bolt, screw eye, padeye, a pulley, or another connector) coupled to the heave compensation frame <NUM> (e.g., coupled to one of the one or more upper beams <NUM> at a first upper beam location) or passed to a sheave coupled to a connector coupled to the heave compensation frame <NUM>. The line <NUM> may then be routed to a first one of the one or more lower sheaves <NUM> at a first location (e.g., a first upper corner) of the fixed frame <NUM> and passed back to the connector (or the sheave coupled to the connector) of the heave compensation frame <NUM> if another of the one or more lower sheaves <NUM> is present at the first location. The line <NUM> can then be routed to a second one of the one or more lower sheaves <NUM> at the first location (e.g., the first upper corner) of the fixed frame <NUM> when a second one of the one or more lower sheaves <NUM> is present at the first location (e.g., the first upper corner) of the fixed frame <NUM>. The line <NUM> may be routed from the second one of the one or more lower sheaves <NUM> to a first one of the one or more lower sheaves <NUM> at a second location (e.g., a second upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is present at the first location (e.g., the first upper corner) of the fixed frame <NUM>. Alternatively, the line <NUM> may be routed from the first one of the one or more lower sheaves <NUM> to the first one of the one or more lower sheaves <NUM> at the second location (e.g., the second upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is not present at the first location (e.g., the first upper corner) of the fixed frame <NUM>.

The line <NUM> may be routed from the first one of the one or more lower sheaves <NUM> at the second location (e.g., a second upper corner) of the fixed frame <NUM> to a second connector (e.g., an anchor blot, eye bolt, screw eye, padeye, a pulley, or another connector) coupled to the heave compensation frame <NUM> (e.g., coupled to one of the one or more upper beams <NUM> at a second upper beam location) or passed to a sheave coupled to the second connector. The line <NUM> may then be routed from the second connector (or sheave coupled to the second connector) to a second one of the one or more lower sheaves <NUM> at the second location (e.g., the second upper corner) of the fixed frame <NUM> if another of the one or more lower sheaves <NUM> is present at the second location (e.g., the second upper corner) of the fixed frame <NUM>. The line <NUM> may be routed from the second one of the one or more lower sheaves <NUM> to a first one of the one or more lower sheaves <NUM> at a third location (e.g., a third upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is present at the second location (e.g., the second upper corner) of the fixed frame <NUM>. Alternatively, the line <NUM> may be routed from the second connector back to the first one of the one or more lower sheaves <NUM> at the second location (e.g., the second upper corner) and then to a first one of the one or more lower sheaves <NUM> at the third location (e.g., the third upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is not present at the second location (e.g., the second upper corner) of the fixed frame <NUM>.

The line <NUM> may be routed from the first one of the one or more lower sheaves <NUM> at the third location (e.g., the third upper corner) of the fixed frame <NUM> to a third connector (e.g., an anchor blot, eye bolt, screw eye, padeye, a pulley, or another connector) coupled to the heave compensation frame <NUM> (e.g., coupled to one of the one or more upper beams <NUM> at a third upper beam location) or passed to a sheave coupled to the third connector. The line <NUM> may then be routed from the third connector (or sheave coupled to the third connector) to a second one of the one or more lower sheaves <NUM> at the third location (e.g., the third upper corner) of the fixed frame <NUM> if another of the one or more lower sheaves <NUM> is present at the third location (e.g., the third upper corner) of the fixed frame <NUM>. The line <NUM> may be routed from the second one of the one or more lower sheaves <NUM> to a first one of the one or more lower sheaves <NUM> at a fourth location (e.g., a fourth upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is present at the third location (e.g., the third upper corner) of the fixed frame <NUM>. Alternatively, the line <NUM> may be routed from the third connector back to the first one of the one or more lower sheaves <NUM> at the third location (e.g., the third upper corner) and then to a first one of the one or more lower sheaves <NUM> at a fourth location (e.g., a fourth upper corner) of the fixed frame <NUM> when the second one of the one or more lower sheaves <NUM> is not present at the third location (e.g., the third upper corner) of the fixed frame <NUM>.

The line <NUM> may be routed from the first one of the one or more lower sheaves <NUM> at the fourth location (e.g., the fourth upper corner) of the fixed frame <NUM> to a fourth connector (e.g., an anchor blot, eye bolt, screw eye, padeye, a pulley, or another connector) coupled to the heave compensation frame <NUM> (e.g., coupled to one of the one or more upper beams <NUM> at a fourth upper beam location) or passed to a sheave coupled to the fourth connector. The line <NUM> may then be routed from the fourth connector (or sheave coupled to the fourth connector) to a second one of the one or more lower sheaves <NUM> at the fourth location (e.g., the fourth upper corner) of the fixed frame <NUM> if another of the one or more lower sheaves <NUM> is present at the fourth location (e.g., the fourth upper corner) of the fixed frame <NUM>. The line <NUM> may be routed from the second one of the one or more lower sheaves <NUM> to the fourth connector (or sheave coupled to the fourth connector) and thereafter to a second one of the one or more upper sheaves <NUM> disposed at a second location on the fixed frame <NUM> at a distance approximately equal to the width of the fixed frame from the location of the first one of the one or more upper sheaves <NUM>. Alternatively, the line <NUM> may be routed from the second one of the one or more lower sheaves <NUM> to the second of the one or more upper sheaves <NUM> disposed at the second location on the fixed frame <NUM>. Furthermore, when no second one of the one or more lower sheaves <NUM> is present the at the fourth location (e.g., the fourth upper corner) of the fixed frame <NUM>, the line <NUM> can be routed to the second of the one or more upper sheaves <NUM> disposed at the second location on the fixed frame <NUM> subsequent to being routed to the fourth connector by the first one of the one or more lower sheaves <NUM> at the fourth location (e.g., the fourth upper corner) of the fixed frame <NUM>. The line <NUM> can then be routed to the second active heave drawworks <NUM> of the one or more active heave drawworks <NUM> (if present) or to a connector (e.g., an anchor blot, eye bolt, screw eye, padeye, or another connector) coupled to, on, or in deck <NUM>, which operates as an anchor point (if the second active heave drawworks <NUM> of the one or more active heave drawworks <NUM> is not present or is not being utilized).

<FIG> illustrates a side view of the drilling rig <NUM> described inclusive of the active heave compensation system <NUM>. As illustrated, the second active heave drawworks <NUM> of the one or more active heave drawworks <NUM> may operate as an anchor (e.g., locking the line <NUM> to restrict its movement) while the first active heave drawworks <NUM> of the one or more active heave drawworks <NUM> extends and retracts the line <NUM> to compensate for heave, as will be described in more detail below with respect to <FIG>. Additionally and/or alternatively, the second active heave drawworks <NUM> of the one or more active heave drawworks <NUM> may operate in conjunction with the first active heave drawworks <NUM> of the one or more active heave drawworks <NUM> to extend and retract the line <NUM> to compensate for heave, for example, to increase the speed at which the line <NUM> can be extended and retracted. Furthermore, the second active heave drawworks <NUM> of the one or more active heave drawworks <NUM> may be removed and a connector (e.g., an anchor blot, eye bolt, screw eye, padeye, or another connector) coupled to, on, or in deck <NUM> may be added to operate as an anchor point for the line <NUM>. Likewise, additionally and/or alternatively, one or more direct acting cylinders or other internal or external actuation device may be used to move the heave compensation frame <NUM> along the one or more guides (e.g., the upper guide <NUM> and the lower guide <NUM>) in place of or in addition to the one or more active heave drawworks <NUM> as the actuation system.

<FIG> further illustrates the computing system <NUM> previously described above. In some embodiments, the computing system <NUM> may operate to configure (i.e., set-up) control of one or more of the active heave drawworks <NUM>, for example, to initialize a motor control of the active heave drawworks <NUM>. Alternatively, the computing system <NUM> runs a program stored therein to control operation of the one or more active heave drawworks <NUM>. The operation of the active heave compensation system <NUM> is discussed below with respect to <FIG> and <NUM>.

<FIG> illustrates a flow chart <NUM> details the operation of an actuation system, for example, including the one or more active heave drawworks <NUM>, in accordance with an embodiment. In step <NUM>, operational values, such as one or more tension values and/or load values that correspond to allowable tensions and/or loads on the line <NUM> are transmitted to the one or more active heave drawworks <NUM>. These operational values may correspond to, for example, a predetermined value for the allowable tensions and/or loads on the line <NUM>. Additionally or alternatively, the operational values may correspond to predetermined ranges of values about a predetermined value for allowable tensions and/or loads on the line <NUM>. The operational values may be initially provided to, for example, a motor control or other controller of the one or more active heave drawworks <NUM>, for example, by the computing system <NUM> or via an input on the active heave drawworks <NUM>.

In step <NUM>, operational characteristics of one or more components of the one or more active heave drawworks <NUM> are monitored. For example, one or more sensors in the one or more active heave drawworks <NUM> may determine tension on the line <NUM> and/or may monitor load on the line <NUM>. The sensed operational characteristics may change during operation of the one or more active heave drawworks <NUM>. For example, the offshore platform <NUM> can move vertically away from the seafloor <NUM> due to waves, winds, or other factors. This causes the deck <NUM> on which the one or more active heave drawworks <NUM> is disposed to move vertically away from the seafloor <NUM>, thus resulting in an increase in tension and/or load on the line <NUM>, which is monitored as an operational characteristic in step <NUM>. Likewise, the offshore platform <NUM> can move vertically towards the seafloor <NUM> due to conditions or factors, causing the deck <NUM> on which the one or more active heave drawworks <NUM> is disposed to move vertically towards the seafloor <NUM>, resulting in a decrease in tension and/or load on the line <NUM>, which is monitored as an operational characteristic in step <NUM>. In step <NUM>, the operational characteristics that are monitored in step <NUM> are transmitted in step <NUM>. This transmission may be from the one or more sensors in the one or more active heave drawworks <NUM> or from a transmitter that receives the operational characteristics from the one or more sensors.

The indication (e.g., via transmitted signal) of the operational characteristics are received by a controller of the active heave drawworks <NUM> or, in other embodiments, by the processing device <NUM> of the computing system <NUM>. The controller of the active heave drawworks <NUM> or the processing device <NUM> of the computing system <NUM> determines, in step <NUM>, whether the indication of the sensed value (e.g., the operational characteristics) represents an increase, a fall, or no change in the tension and/or load on the line <NUM>. If the indication is, for example, determined to be the same as a predetermined value, approximately the same as a predetermined value (e.g., within a predetermined tolerance of the predetermined value), or is within a predetermined range of a predetermined value (e.g., within a percentage of the predetermined value), the operational characteristics are deemed acceptable in step <NUM> and the process returns to step <NUM>. It should be noted that indications may be transmitted in step <NUM> and determinations in step <NUM> may be made continuously (i.e., as a stream of uninterrupted data inputs and decisions), near continuously (i.e., as a stream of data inputs and decisions slowed only by factors such as data sensing time, transmission time, calculation time, and other operational limiting characteristics), or on a schedule (e.g., at approximately every five minutes, approximately every two minutes, approximately every minute, approximately two times a minute, approximately ten times a minute, approximately twenty times a minute, approximately thirty times a minute, approximately sixty times a minute, approximately a predetermined fraction of a second, or another time period).

Returning to step <NUM>, if the controller of the active heave drawworks <NUM> or the processing device <NUM> of the computing system <NUM> determines, in step <NUM>, that, for example, the indication is not the same as a predetermined value, not approximately the same as a predetermined value (e.g., not within a predetermined tolerance of the predetermined value), or is not within a predetermined range of a predetermined value (e.g., not within a percentage of the predetermined value), the operational characteristics are deemed unacceptable in step <NUM> and the process moves to step <NUM>.

In step <NUM>, the controller of the active heave drawworks <NUM> or the processing device <NUM> of the computing system <NUM> determines an amount of adjustment by the one or more active heave drawworks <NUM> to return the tension and/or load of the line <NUM> to the predetermined value. This amount of adjustment can be, for example, the amount of rotation of a drum of the one or more active heave drawworks <NUM> to extend or retract the line <NUM> as necessary so as to keep the tension and/or the load on the line <NUM> at a predetermined value or within a predetermined range of values about a predetermined value. The amount of adjustment is transmitted as a control signal to, for example, a motor control of the active heave drawworks <NUM> by the controller of the active heave drawworks <NUM> or the computing system <NUM>.

In step <NUM>, a motor controller, for example, of the one or more active heave drawworks <NUM> rotates the drum of the one or more active heave drawworks <NUM> based on the control signal received from the controller of the active heave drawworks <NUM> or the computing system <NUM>. The control signal causes the amount and direction of the rotation to be imparted to the drum by the motor controller. This has the effect of keeping the tension and/or load on the line <NUM> relatively constant (i.e., at a predetermined value or within a predetermined range about a predetermined value) and causes the heave compensation frame <NUM> (as well as the derrick <NUM> and inclusive of the drill floor <NUM>) to move along the one or more guides (e.g., the upper guide <NUM> and the lower guide <NUM>) towards the deck <NUM> as the deck <NUM> is moving vertically away from the seafloor <NUM> when the line <NUM> is extended from the one or more active heave drawworks <NUM> by rotation of the drum therein. Similarly, the control signal can cause the heave compensation frame <NUM> (as well as the derrick <NUM> and inclusive of the drill floor <NUM>) to move along the one or more guides (e.g., the upper guide <NUM> and the lower guide <NUM>) away from the deck <NUM> as the deck <NUM> is moving vertically towards from the seafloor <NUM> when the line <NUM> is retracted to the one or more active heave drawworks <NUM> by rotation of the drum therein. These respective operations that are undertaken, for example, as a result of vertical movement of the offshore platform <NUM> with respect to the seafloor <NUM> keeps the heave compensation frame <NUM> (as well as the derrick <NUM> and inclusive of the drill floor <NUM>) at a constant or nearly constant distance from the seafloor <NUM>.

The operation of the active heave compensation system <NUM> allows for movement of the drill floor <NUM> by, for example, approximately <NUM> feet (e.g., plus or minus <NUM> feet relative to the hull of the offshore platform <NUM>) to compensate for vertical movements of the offshore platform <NUM> with respect to the seafloor <NUM>. The use of two active heave drawworks <NUM> can provide redundancy (for example, if only one active heave drawworks <NUM> is used in operation to adjust the line <NUM> tension with the other operating as an anchor point) as well to as implement more rapid adjustments (for example, if two one active heave drawworks <NUM> are used in conjunction to adjust the line <NUM> tension). Additionally, use of the active heave compensation system <NUM> can eliminate the use of a coil tubing lifting frame as well as passive heave compensation systems for a drill string, such as, a crown or top mounted compensator. Furthermore, by utilizing the fixed frame <NUM> and the heave compensation frame <NUM> as described herein, effects on stability and wind loading can be minimized.

Claim 1:
A system (<NUM>), comprising:
a first structure (<NUM>) configured to be coupled to a tubular string (<NUM>, <NUM>) extending to a seafloor (<NUM>), wherein the first structure (<NUM>) comprises:
a drill floor (<NUM>) as a bottom portion of the first structure, wherein the drill floor (<NUM>) comprises floor slips (<NUM>) configured to support a tubular segment;
one or more beams (<NUM>) coupled to and disposed about the drill floor (<NUM>) and extending vertically away from the drill floor (<NUM>);
one or more upper beams (<NUM>) coupled to the one or more beams (<NUM>) and extending perpendicular to the one or more beams (<NUM>); and
a derrick of an offshore vessel (<NUM>) disposed on the one or more upper beams (<NUM>); and
a second structure (<NUM>) circumscribing at least one of the drill floor (<NUM>) and the derrick (<NUM>) of the offshore vessel (<NUM>) and slidingly coupled to the first structure (<NUM>) via at least one guide (<NUM>, <NUM>) and configured to restrict lateral movement of the first structure (<NUM>) while allowing for vertical movement between the first structure (<NUM>) as well as the derrick (<NUM>) and inclusive of the drill floor (<NUM>) and the second structure (<NUM>) relative to the seafloor (<NUM>).