Redundant drawworks

Implements or apparatus for applying pushing or pulling force – Apparatus for hauling or hoisting load – including driven... – Device includes rotatably driven – cable contacting drum

Reexamination Certificate

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Details

C254S342000, C254S378000

Reexamination Certificate

active

06182945

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to oil field equipment, and more particularly to an improved drawworks.
2. Description of the Related Art
A drawworks, sometimes referred to as a hoist, is a large piece of oil field equipment which can broadly be described as a very large winch. The drawworks is mounted on an oil or gas well drilling rig, its sole function being to raise and lower drill pipe and casing into and out of the bore hole. Typically, a drawworks is provided with: a hollow drum which is coaxially mounted on a drum shaft; a source of power to cause the drum shaft and drum to rotate; some means of transmitting power from the power source to the drum shaft; and, some means of braking the drum. The drawworks is mounted on the drilling rig such that the longitudinal center axis of the drum and drum shaft is coplanar with the drilling rig platform, or horizontal. Examples of the power source are AC motors, DC motors, and diesel or other types of engines. The power is generally transmitted from the power source to the drum shaft either by (1) a chain transmission mechanism or (2) a gear transmission mechanism. The drum can be braked in a number of ways, examples of which are by disc brakes, band brakes, water-cooled brakes, electric brakes, or by the power source. The drum is wrapped with a length of wireline, normally not provided with the drawworks. The wireline is fed upwardly from the drawworks to the top of the oil derrick and then downwardly such that it can be attached to the drill pipe or casing. Between the top and bottom of the derrick, the wireline is passed through a series of sheaves (or pulleys), which are housed within a crown block and traveling block. The lowermost end of the wireline is attached to a hook and swivel arrangement, to which the drill pipe and casing may be releasably attached, and thereby raised and lowered.
Problems can arise with conventional drawworks of the type described above. One very serious problem, which the present invention is believed to solve, arises in the event that one of the components of the drawworks fails. The most common failures are mechanical in nature, and occur either in the power source (motor or engine) or in the gear or chain mechanism. In the event that such a mechanical failure occurs, the drawworks will become completely disabled, and thus unable to perform its function. If the failure can be quickly remedied, and the drawworks quickly restored to operation, then no problems should arise. However, in the event that the failure is of such a serious nature that it cannot be quickly remedied, such that the entire drilling operation must be halted for a period of time, then it is almost inevitable that the drill pipe will become “stuck” in the bore hole. The drill pipe becomes “stuck” because, after sitting in the same position for an extended period of time, rock, dirt and other debris tends to cave in around the pipe and on top of the drilling bit, which is attached to the lowermost end of the drill pipe. Those skilled in the oil well drilling industry know that a “stuck” drill pipe can be disastrous and extremely expensive to remedy, and could potentially lead to the bore hole being completely abandoned. The drawworks of the present invention was developed to reduce the risk of the drill pipe becoming “stuck.” As will be more fully described below, the drawworks of the present invention is provided with complete redundancy, which means that if a mechanical failure occurs, the drawworks will still have the ability to raise the drill pipe out of the well hole, or at least up into the casing, before the drill pipe becomes “stuck.”
SUMMARY OF THE INVENTION
The present invention is directed generally to an improved drawworks. A specific embodiment of the drawworks of the present invention comprises: a mounting base (or skid); a drum; a drum shaft; a left gear box; a right gear box; a left brake; a right brake; a lower left motor; an upper left motor; a lower right motor; and an upper right motor. The drum is mounted to the drum shaft in a conventional manner within the drum housing. The drawworks may also be provided with a drum housing which may be provided with an opening through which the wireline passes. The drum shaft runs the full length of the drawworks, and passes through and is rotatably mounted (with bearings at appropriate locations) within each of the respective shaft bores provided within the left brake, the left gear box, the drum housing, the drum, the right gear box, and the right brake. The upper left motor is positioned above the lower left motor and nearer to the drum. Likewise, the upper right motor is positioned above the lower right motor and nearer to the drum. The left motors are coupled to the input shafts of the left gear box by mechanical couplers. Likewise, the right motors are coupled to the input shafts of the right gear box by mechanical couplers. The left and right brakes provide the drawworks with sufficient braking capability to control the rotation of the drum as the wireline is being fed out to lower the drill pipe or casing.
In another aspect, the redundant drawworks of the present invention includes: a mounting base; a left gear box secured to the mounting base; a right gear box secured to the mounting base; a drum rotatably coupled to the left and right gear boxes; at least one left motor secured to the mounting base and coupled to the left gear box; and at least one right motor secured to the mounting base and coupled to the right gear box, whereby the drum is powered by the at least one left and right motors through their respective gear boxes, the at least one left motor and the at least one right motor being able to power the drum through their respective gear boxes independently of each other. Another feature of this aspect of the present invention is that the drawworks may further include a drum shaft, wherein the drum is mounted to the drum shaft, and the drum shaft is rotatably coupled to the left and right gear boxes. Another feature of this aspect of the present invention is that the drawworks may further include a drum housing between the left and right gear boxes, wherein the drum is rotatably mounted within the drum housing and coupled to the left and right gear boxes. Another feature of this aspect of the present invention is that the drawworks may further include a drum shaft, wherein the drum is mounted to the drum shaft, and the drum shaft is rotatably mounted within shaft bores on the drum housing, the left gear box, and the right gear box. Another feature of this aspect of the present invention is that the drawworks may further include a left brake coupled to the drum shaft and a right brake coupled to the drum shaft. Another feature of this aspect of the present invention is that the left and right brakes may be disc brakes. Another feature of this aspect of the present invention is that the left and right brakes may be band brakes. Another feature of this aspect of the present invention is that the left and right brakes may be water-cooled brakes. Another feature of this aspect of the present invention is that the left and right brakes may be electric brakes. Another feature of this aspect of the present invention is that each gear box may be a gear reduction collector drive with an integral three-speed mechanical gear transmission. Another feature of this aspect of the present invention is that each gear box may be a single-speed mechanical gear transmission. Another feature of this aspect of the present invention is that each gear box may be a multiple-speed mechanical gear transmission. Another feature of this aspect of the present invention is that each gear box may include a collector gear drive and at least one multiple-speed gear transmission, the collector gear drive being coupled to the at least one multiple-speed gear transmission and to the drum, and the at least one multiple-speed gear transmission being coupled to the respective at least one motor. Another feature of this aspect of the presen

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