Patent Application
20150361736
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource.
Floating drilling platforms are sometimes used for offshore drilling operations and include a hoisting system for raising and lowering equipment, such as a drill string, to a subsea wellsite. Because these platforms float at the surface of the water and are not anchored to the seabed with legs, the platforms can vertically rise and fall (i.e., heave) with waves in the water. Heave compensation can be used to counteract the vertical heaving motion and reduce movement of the drill string or other hoisted load with respect to the seabed.
Various types of heave compensators have been used in an effort to maintain a constant weight on bit for a hoisted drill string and reduce deviation of the drill string with respect to the seabed as the drilling platform rises and falls with the waves. Simple heave compensators acting as shock absorbers have been provided between traveling blocks and drill strings hoisted with a drawworks system. Active heave compensation has also been used, in which heaving motion of the drilling platform is measured and used to actively control the position of the drill string.
As operators have moved to deeper waters and deeper wells, the weight of the equipment to be hoisted by offshore rigs (e.g., drill strings, casing strings, and wellhead equipment) has increased. Multi-part block-and-tackle arrangements have been used with drawworks for hoisting on drilling rigs, in which hoisting lines are reeved through sheaves of crown and traveling blocks to provide a mechanical advantage. One approach to increasing the hoisting capabilities of such arrangements is to add more lines and sheaves and increase the size of the hoisting lines. Drilling platforms have also been provided as hydraulically driven “cylinder rigs,” which use large hydraulic cylinders instead of drawworks. The hydraulic cylinders in such rigs can provide both the main hoisting function and a heave compensating function.
Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
Embodiments of the present disclosure generally relate to hoisting systems having heave compensation functions. In certain embodiments, hoisting systems include both active heave compensation at drawworks (or winches) of the systems and passive heave compensation. And in at least some embodiments, active heave compensation and passive heave compensation are provided at a winch that includes a planetary gear system, which allows both active and passive heave compensation to be applied to a rotating drum of the winch.
Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.
These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Specific embodiments of the present disclosure are described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
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. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.
Turning now to the present figures, a system 10 is illustrated in
The vessel 12 includes a hoisting system for raising and lowering equipment with respect to a drill floor of the vessel, which facilitates well drilling and completion operations. The depicted hoisting system includes a derrick 14 constructed on the drill floor of the vessel 12. Various equipment and other loads can be supported by one or more hoisting lines 20 of the hoisting system. In
The hoisting system includes a drawworks 22, which can be provided on the drill floor with the derrick 14, as shown in
In at least some embodiments, the hoisting system includes both active heave compensation and passive heave compensation to compensate for heaving motion of the floating vessel 12 from wave action at the surface of the water. One such embodiment is generally depicted in
As the load 30 is suspended from the crown block 24 with the hoisting lines 20, heave of the vessel 12 causes the load 30 to move up and down with respect to the underlying seabed. During drilling operations, such movement can cause a drill bit at the end of the drill string 18 to be pulled off the bottom of the well (with upward heave) or to be pushed with greater force against the bottom if the well (with downward heave).
To compensate for the heaving motion and reduce deviation of the hoisted load 30 with respect to the seabed, the hoisting system in
The passive heave compensation system 36 can also be used to counter heaving motion of the vessel 12. In contrast to the active heave compensation system 34, the passive heave compensation system 36 can counter heave without requiring external power. For example, the passive heave compensation system 36 can include one or more hydraulic devices (e.g., hydraulic cylinders or hydraulic motors) that passively store and release energy from the heaving motion of the vessel 12 to move the load 30 with respect to the drill floor to reduce the deviation of the load 30 from its position with respect to the seabed. In some instances, the passive heave compensation system 36 could also include an active component (e.g., a hydraulic cylinder that passively compensates for heave and that can also be actively driven for further heave compensation).
Various examples of hoisting systems having both active and passive heave compensation are described in U.S. patent application Ser. No. 14/304,728, which was filed on June 13, 2014, and at the time of filing was entitled “Hoisting Systems with Heave Compensation,” named Erling Tambs et al. as inventors, and was marked with an attorney docket number of DRL-032158 US; that application is hereby incorporated by reference in its entirety. In some instances of the present technique, such as those described below with respect to
In
Motors 78 can be operated to drive rotation of the drum 74 to reel in or reel out the hoisting lines 20 to raise and lower an attached load 30. Any suitable motors 78 could be used. The motors 78 can include electric motors, for example. The motors 78 can also provide active heave control via the drum 74, in which case the motors are actively controlled to compensate for heave as generally described above.
Passive heave compensation can be applied to the winch 72 by hydraulic cylinders 82. These cylinders 82 are depicted with cylinder housings 84 with extendable rods 86 connected to sheaves 92. In at least some instances, other sheaves are coupled below the cylinders 82. In one embodiment, the hydraulic cylinders 82 are provided in a jigger winch assembly with tension lines 96 to rotate a ring gear 98 of a planetary gear system of the winch 72, although other arrangements could instead be used.
As generally shown in
In this embodiment, the passive heave compensation system (here including the cylinders 82) is connected to the ring gear 98. This allows a combination of active and passive adjustment of the rotational position of the drum 74 through a differential regulation principle. In the embodiment depicted in
Various active and passive components can be used to drive rotation of different elements of the planetary gear system. As shown in
Moreover, the active devices 122, the passive devices 124, and the drum 128 could be connected to the ring gear, sun gear, and the set of planetary gears in any combination. It is noted that there are six permutations of coupling each of the active devices 122, the passive devices 124, and the drum 128 with one of the ring gear, the sun gear, and the planetary gears of the gear set 126. For instance, the connections of the active drive devices 122 and the passive heave compensation devices 124 could be switched from the arrangement of system 70, with the active devices 122 coupled to the ring gear and the passive devices 124 coupled to the sun gear. In other embodiments, the drum 128 could be connected to the sun gear or the ring gear instead of the planetary gears, which could be driven by the active devices 122 or the passive devices 124. Although these embodiments use a differential system on a planetary gear arrangement principle, a regular differential may also be used (e.g., in the case of passive and active drive inputs each being provided by motors).
The differential system with a planetary gear arrangement can be used to hoist a load by rotating the drum 128. The system can be considered to have two types of mechanical input (active drive and passive drive) and one mechanical output (to rotate the drum). The differential can be controlled in such way that drum motion is from active input alone, from passive input alone, or from the simultaneous combination of both inputs. Drum movement is then controlled by the sum of any moving inputs. It is noted that the drum can have either one or more wire ropes or chains, and might have one or more layers. Drum output speed varies dependent on direct acting hoisting or via block-and-tackle systems.
A passive drive input can be characterized as one that does not require an external power source to be able to perform the desired motion compensation. If the compensation is taken care of by the passive side, rig power consumption is at a minimum. A semi-active system is typically used when passive compensation is performed by hydraulic motors; in such cases power consumption can be used just to control displacement of motors. The passive side can also be used as a regenerative device for hoisting, in which motors are used for braking when lowering and charging accumulators and the stored energy is then used for hoisting the traveling load. The passive system can also have a parallel active system attached. This system can be used either as a performance booster while in a constant tension mode (maintaining a tension level on the hoisting line) or as an energy saver when in active heave compensation mode.
The passive drive inputs can include any suitable devices and arrangements. For example, in some embodiments, the passive drive inputs are provided as hydraulic cylinders with wire or chain connections. In at least some instances, these wire or chain connections are passed over eccentric sheaves before entering the system to compensate for the differential in passive compensation component properties. The passive drive inputs can instead include hydraulic motors with or without a semi-active part. One example of a differential heave compensation system 120 using hydraulic motors with semi-active parts as the passive drive inputs is depicted in
The active side (i.e., the active drive inputs) can be characterized as the part of the system used for hoisting, and also for active heave compensation. The active part is dependent on an external power source to drive rotation of the drum. The active drive inputs can be provided in any suitable form, such as an electric motor, a hydraulic motor, or a hydraulic cylinder. The electric and hydraulic motors provided as active drive inputs could be used with or without gearboxes and with or without brakes in various embodiments.
In some embodiments, multiple input drive devices (whether active or passive) may be used, which can provide redundancy and increased performance. By way of example, when four passive cylinders are present in a hoisting system, only two can be used if compensating lower loads to increase performance (from an accumulator bank for the four cylinders being made available to only half of the cylinders).
A further example of a differential heave compensation system 120 is depicted in
A hydraulic accumulator 144 is connected to the hydraulic motors 138 and to gas storage bottles 146. In the system 70 described above, similar gas storage bottles attached to the hydraulic cylinders 82 provide the volume allowing the extension and retraction of the cylinder rods 86 for passive heave compensation. The compensating load value is regulated by increasing or decreasing the charge pressure (e.g., of nitrogen) in these storage volumes. In the embodiment shown here in
The compensation system 120 in
As generally noted above, in at least one embodiment passive heave compensation can be provided by one or more hydraulic cylinders via a crankshaft coupled to the planetary gear system. In
Though all-hydraulic cylinder rigs can be used for hoisting functions, they can have certain drawbacks, such as the complexity of the hydraulics, the size and expense of a hydraulic power unit sufficient for the rig, and the piping and cylinders required to provide both the main hoisting function (which may require about 180 feet of vertical travel) and the heave compensating system. In contrast, certain embodiments disclosed herein include an electrically driven winch or drawworks for normal hoisting functions and active heave compensation combined with a hydraulic passive heave compensating system with much less complexity than the all-hydraulic designs. This reduction in complexity enables lighter hoisting systems to be used and facilitates installation and servicing. The present systems may also have reduced power consumption compared to certain previous designs. Further, moving the passive heave compensation system to the drill floor from high in the derrick provides a lower center of gravity. And in the use of single-part lines in some embodiments enables a faster hoisting speed while maintaining a reasonable rotation speed of the drum of the winch.
While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
