US20150197993A1

US20150197993A1 - Derrick lift system of offshore structure

Info

Publication number: US20150197993A1
Application number: US14/597,976
Authority: US
Inventors: Jong Yeol LEE; Dong Hwan Hwang; Jae Il BAE
Original assignee: EUNKWANG INDUSTRIAL CO LTD
Current assignee: EUNKWANG INDUSTRIAL Co Ltd
Priority date: 2014-01-15
Filing date: 2015-01-15
Publication date: 2015-07-16

Abstract

Disclosed herein is a derrick lift system of an offshore structure. The derrick system can improve drilling workability by enabling safe and easy height adjustment of a derrick using an adjustment unit, and can improve structural stability by lowering the center of gravity of the derrick through the height adjustment of the derrick, as occasion demands.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application Nos. 10-2014-0004950 and 10-2014-0004951, filed on Jan. 15, 2014 in the Korean Intellectual Property Office, the entirety of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention
The present invention relates to a derrick lift system of an offshore structure, and more particularly to a derrick lift system of an offshore structure, which enables stable movement of a derrick in a vertical direction in drilling operation while allowing easy adjustment of the height or level of the derrick.
2. Description of the Related Art
With rapid industrialization and industrial development, usage of resources such as petroleum has gradually increased and thus stable production and supply of oil are important issues at a national level. For this reason, there has recently been developed a drill ship with drilling equipment economically proper to develop a minor limited oil field or a deep sea oil field that has been untapped due to economic infeasibility, as well as land drilling.
In conventional offshore drilling, there has been generally used a rig ship designed for offshore drilling or a stationary platform that must be transported by tugboats, and perform drilling in a state of being anchored at a predetermined location at sea by a mooring device. In recent years, however, a so-called drill ship manufactured like a general ship is developed to have state-of-the-art drilling equipment and navigate under its own power, and is used in offshore drilling.
In the central region of the rig ship or drill ship provided with a variety of drilling equipment for drilling for oil, gas, and the like under the sea bed, a moon pool is formed such that a drill string, that is, a riser or a drill pipe for drilling for oil, gas, etc. under the sea bed can be moved up and down.
FIG. 1 is a side view showing drilling operation of a typical drill ship.
Referring to FIG. 1, a riser 3 and a drill pipe 4 are moved downwards through a moon pool 2 formed at the center of the drill ship, and then drill for seabed resources in an oil well 12 placed in a reservoir 11 under the seabed 5.
The riser 3 is moved down to the sea bed 5 before moving the drill pipe 4 to the oil well 12 and provides a passage through which mud returns.
With the riser 3 placed outside the drill pipe 4, the drill pipe 4 is moved down to the oil well 12 through a sub-bottom stratum 10 along the riser 3.
Here, before the riser 3 is moved down to the seabed 5 or the drill pipe 4 is moved down to the oil well 12, short risers or short drill pipes are sequentially connected to each other to form the riser 3 or the drill pipe 4, which in turn is moved downwards.
On the seabed 5, a blowout preventer (BOP) 6 is placed to prevent transfer of abnormally high pressure along the drill pipe 4.
In the sub-bottom stratum 10, a casing 7 is secured and a drill pipe 4 provided with a drill bit 9 is inserted into the casing 7 and drills for the seabed resources.
To prevent the drill bit 9 from overheating by heat generated when the drill bit 9 drills the ground and to facilitate drilling through lubrication, mud 8 is inserted into the drill pipe 4. The mud escapes through the drill bit 9 and returns through the casing 7 and the riser 3.
When the drilling operation is completed, the drill pipe 4 is moved to a drill floor through the moon pool 2, separated, and then carried to a loading place.
FIG. 2 is a view of a typical derrick structure in the related art.
Referring to FIG. 2, a typical drill ship includes an upper deck 13 and a drill floor 14 placed on the upper deck 13. A derrick 1 is placed on the drill floor 14. Drill pipes 4 transversely loaded in a pipe loading area are raised and clamped by a top drive 15 and a rotary table 16.
Two or more drill pipes 4 coupled to each other are temporarily loaded in a setback area in a vertical direction, and moved downwards toward the moon pool in drilling operation.
The derrick 1 serves to move drilling equipment such as the drill pipe 4 and the like up or down to a desired location in a vertical direction by winding or releasing a wire rope connected to the drilling equipment through operation of a winch.
Generally, although the height of the derrick varies depending upon design, the derrick 1 refers to a truss type steel tower having a height of about 100 m. In the related art, derricks tend to be increasing in size to suit drilling operation at increasing depths.
Since a typical derrick has a fixed height, the typical derrick has a high center of gravity, causing very low structural stability of the hull.
To resolve such problems in the related art, Korean Patent Publication No. 2012-0032128 discloses a derrick elevator capable of adjusting the height of the derrick. However, this derrick system has a problem of low workability due to difficulty in height adjustment of the derrick.

BRIEF SUMMARY

The present invention has been conceived to solve such problems in the related art, and an aspect of the present invention is to provide a derrick lift system of an offshore structure which can safely and rapidly move a derrick in a vertical direction in drilling operation, and can improve structural stability by lowering the center of gravity of the derrick through the height adjustment of the derrick, as occasion demands.
In accordance with one aspect of the present invention, a derrick lift system of an offshore structure includes: a base plate secured to a drill floor and having a locking groove formed on one side thereof; a gearbox placed at one inner side of the base plate and coupled to a drive motor; a relay gear rotably mounted on the base plate to engage with the gearbox; a pinion rotably mounted on the base plate to engage with the relay gear; a post supporting a lower end of the derrick to lift or lower the derrick and provided to the other inner side of the base plate to be perpendicularly movable, and having a rack formed on one surface thereof to engage with the pinion and a locking groove formed on one surface thereof; a stopper mounted on the base plate and selectively inserted into the locking grooves to secure the post at a lifted or lowered location; and a derrick height adjustment unit placed at one side of the base plate to align the locking grooves through height adjustment of the derrick.
The derrick height adjustment unit may include a mounting bracket secured to the base plate; and a hydraulic cylinder provided to the mounting bracket and adjusting the height of the derrick.
The base plate may be provided with a sensor detecting alignment of the locking grooves.
The pinion may include a securing pin engaging with the rack, and the base plate may be provided with a safety cylinder coupled to the stopper to selectively lock the stopper.
The base plate may be provided with a ratchet cylinder, and the ratchet cylinder may include a rod and a pivot latch rotably installed at the rod. The pivot latch stops a latch jaw of the pinion selectively and latches the pinion.
The base plate and the post may be arranged to support four lower corners of the derrick.
According to a modification of the invention, the stopper may include a guide plate secured to a side surface of the base plate and having a guide rail formed on an upper surface thereof; a rod horizontally secured above the guide plate; a cylinder body disposed to receive the rod therein and to be locked into the locking grooves while moving along the rod by hydraulic force and having safety grooves formed on upper surfaces of both ends thereof; and a safety cylinder secured to a side surface of the base plate and coupled into the safety grooves to prevent separation of the cylinder body from the locking grooves when the cylinder body is inserted into the locking grooves.
The cylinder body may be formed with fluid inlet and outlet ports and a hydraulic chamber, and may have safety grooves formed on upper surfaces of both ends thereof.
According to the present invention, the derrick lift system of an offshore structure can improve drilling workability by enabling safe and easy height adjustment of a derrick using an adjustment unit, and can improve structural stability by lowering the center of gravity of the derrick through the height adjustment of the derrick, as occasion demands.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a side view showing drilling operation of a typical drill ship;

FIG. 2 is a view of a typical derrick structure in the related art;

FIG. 3 is a side view of a derrick lift system of an offshore structure according to one embodiment of the present invention, viewed from port side;

FIG. 4 is a side view of the derrick lift system of an offshore structure according to the embodiment of the present invention, viewed from starboard side;

FIG. 5 is a side view of the derrick lift system of an offshore structure according to the embodiment of the present invention, viewed from aft side;

FIG. 6 is a side view of the derrick lift system of an offshore structure according to the embodiment of the present invention, viewed from a forward side;

FIG. 7 is an enlarged view of a main part of the derrick lift system of FIG. 3;

FIG. 8 is a plan view of the derrick lift system of FIG. 7;

FIG. 9 is an enlarged view of a main part of the derrick lift system of FIG. 7;

FIG. 10 is a sectional view of the derrick lift system taken along line I-I of FIG. 3;

FIG. 11 is a view showing an interior structure of a stopper according to a modification of the present invention;

FIG. 12 is a view of an interior reinforcing structure of the stopper according to the modification of the present invention;

FIG. 13 is a longitudinal sectional view of the stopper in a locked state, according to the modification of the present invention; and

FIG. 14 is a longitudinal sectional view of the stopper in an unlocked state, according to the modification of the present invention.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Referring to the accompanying drawings, the present invention is an apparatus for vertical movement and height adjustment of a derrick designed to support a drilling pipe during drilling operation. However, it should be understood that the present invention can also be applied to any structure including a mast as well as the derrick so long as the structure is capable of supporting the drilling pipe during not only overland but also offshore drilling operation.
Referring to FIG. 3 to FIG. 10, a derrick lift system of an offshore structure according to one embodiment of the present invention is placed on a drill floor 14 and includes base plates 110 each having a locking groove 110 a on one side thereof
Each of the base plates 110 is provided at one inner side thereof with a gearbox 120, which is coupled to a hydraulic drive motor 121. The gearbox 120 refers to a unit of gears for power transmission and is well known in the art. Thus, a detailed description of the gearbox is omitted herein.
A relay gear 130 is rotatably mounted on the base plate 110 to engage with the gearbox 120.
A pinion 140 is rotably mounted on the base plate 110 to engage with the relay gear 130.
A post 150 is provided to the other inner side of each of the base plates 110 to be perpendicularly movable and supports a lower end of the derrick 100 to move the derrick 100 up or down.
The post 150 has a rack 151 formed on one surface thereof to engage with the pinion 140 and a locking groove 150 a formed on one side thereof
A stopper 160 is mounted on the base plate 110 to secure the post 150 at a predetermined location.
A derrick height adjustment unit 190 is placed at one side of the base plate 110 to align the locking grooves 110 a, 150 a through height adjustment of the derrick 100.
The derrick height adjustment unit 190 includes a mounting bracket 191 secured to the base plate 110, and a hydraulic cylinder 192 provided to the mounting bracket 191 and adjusting the height of the derrick 100.
The hydraulic cylinder 192 may be composed of a hydraulic cylinder body 192 a secured to the mounting bracket 191 and a rod 192 b moved in a vertical direction by hydraulic pressure to adjust the height of the derrick 100.
The base plate 110 may be provided with a sensor 193 (see FIG. 3) that detects alignment of the locking grooves 110 a, 150 a. The pinion 140 includes a securing pin 142 that engages with the rack 151.
The base plate is provided with a ratchet cylinder 170, and the ratchet cylinder 170 includes a rod 170 a and a pivot latch 171 rotably installed at the rod.
The pivot latch 171 stops a latch jaw 143 of the pinion 140 selectively and latches the pinion 140 not to be rotated.
In other words, when the pinion 140 is rotated in a direction in which the post 150 is raised, the pivot latch 171 does not obstruct rotation of the pinion 140. Conversely, when the pinion 140 is rotated in the opposite direction, the pivot latch 171 regulates rotation of the pinion 140. That is, the pivot latch 171 is configured to restrict rotation of the pinion 140 in order to prevent an accident due to damage to a hydraulic line in a state that the derrick 100 is raised to a predetermined height.
The base plate 110 is provided with a safety cylinder 180 coupled to the stopper 160 to selectively lock the stopper 160. The safety cylinder 180 serves to lock the stopper 160.
The base plates 110 and the posts 150 may be arranged to support four lower corners of the derrick 100.
The derrick lift system according to this embodiment may lift the derrick 100 through engagement between the rack 151 and the pinion 140 after receiving power from the drive motor 121, and may adjust the height of the derrick 100 through the derrick height adjustment unit 190.
The base plates 110 are secured to the drill floor 14. The post 150 is placed at the other inner side of each of the base plates 110 to be perpendicularly movable and to support the lower end of the derrick 100 so as to lift or lower the derrick 100.
The sensor 193 detects alignment between the locking groove 110 a of the base plate 110 and the locking groove 150 a of the post 150, and automatically activates the stopper 160 to secure the location of the derrick 100.
Next, operation of the derrick lift system of an offshore structure with the aforementioned configuration will be described.
The derrick 100 is lowered to lower the center of gravity of the derrick when a drill ship is moved to a drilling point or rerouted to avoid accident due to a typhoon and the like, whereas the derrick 100 is lifted upon drilling operation.
In operation of lifting the derrick 100, the drive motor 121 engaging with the gearbox 120 is driven to rotate the relay gear 130 engaging with gearbox 120, thereby rotating the pinion 140 engaging with the relay gear 130.
Since the rack 150 engages with the securing pin 142 of the pinion 140, the rack 150 is raised through rotation of the pinion 140. Here, the post 110 integrally formed with the rack 150 is also raised, whereby the derrick 100 provided to the post 110 is raised.
Then, since the stopper 160 is inserted into the locking grooves 110 a, 150 a in order to secure the post 150 in a lifted or lowered state, it is necessary to adjust the height of the derrick 100. However, since the derrick 100 is very heavy, it is difficult to achieve accurate height adjustment of the derrick 100. Moreover, even in the case where the height of the derrick 100 is accurately adjusted, the derrick 100 is likely to sag due to heavy weight thereof over time.
As such, non-accurate height adjustment of the derrick 100 causes misalignment of the locking grooves 110 a, 150 a, whereby the stopper 160 cannot be inserted into and locked to the locking grooves 110 a, 150 a. Accordingly, work is very difficult in an actual work site since leveling operation (height adjustment) of the derrick 100 is repeated several times. However, according to the present invention, the height of the derrick 100 can be easily adjusted using the derrick height adjustment unit 190. That is, according to the present invention, the derrick height adjustment unit 190 is driven to lift and gradually lower the derrick 100 such that the height of the derrick can be set to a desired location to align the locking grooves 110 a, 150 a, whereby the stopper 160 can be easily and conveniently inserted into the locking grooves 110 a, 150 a and locked thereby.
On the other hand, although alignment of the locking grooves 110 a, 150 a can be confirmed by an operator with the naked eye, the sensor 193 may be used to confirm alignment of the locking grooves 110 a, 150 a. When the sensor 193 is used to confirm alignment of the locking grooves, it is possible to improve operation safety and accuracy.
In addition, after detecting alignment between the locking grooves 110 a, 150 a, the sensor 193 sends a detection signal to a controller (not shown), which in turn automatically operates the stopper 160 to lock the location of the derrick 100. In this way, a series of procedures of lifting, leveling and locking the derrick 100 can be realized in an automatic manner.
Next, a stopper according to a modification of the present invention will be described with reference to FIG. 11 to FIG. 14.
The derrick 100 is disposed to be lifted or lowered, and a stopper 260 is provided to lock the derrick 100 at a lifted or lowered location. Here, the stopper 260 may include a stationary rod 262 and a cylinder body 263 moved along the rod 262. In this modification, the stopper 260 is configured to allow the cylinder body 263 to be moved into and locked by the locking grooves 110 a, 150 a, unlike the stopper 160 described above. As such, when the cylinder body 263 is moved into and locked by the locking grooves 110 a, 150 a, the stopper can exhibit high endurance to high load of the derrick without deformation.
Now, the configuration of the stopper 260 will be described in more detail. The stopper 260 includes a guide plate 261 secured to a side surface of the base plate 110 and having a guide rail 261 b formed on an upper surface thereof; the rod 262 horizontally secured above the guide plate 261; a cylinder body 263 disposed to receive the rod 262 therein and to be locked into the locking grooves 110 a, 150 a while moving along the rod 262 by hydraulic force and having safety grooves 263 f formed on upper surfaces of both ends thereof; and a safety cylinder 264 secured to a side surface of the base plate 110 and coupled into the safety grooves 263 f to prevent separation of the cylinder body 263 from the locking grooves 110 a, 150 a when the cylinder body 263 is inserted into the locking grooves 110 a, 150 a.
After alignment of the locking grooves 110 a, 150 a, the stopper 260 is inserted into (locked to) the locking grooves 110 a, 150 a in the following manner. When alignment between the locking grooves 110 a, 150 a is confirmed, hydraulic pressure is supplied into the cylinder body 263 and forces the cylinder body 263 to be inserted into the locking grooves 110 a, 150 a while moving along the rod 262. Here, the guide rail 261 b enables smooth movement of the cylinder body 263. Then, the safety cylinder 264 is coupled (locked) into the safety grooves 263 f, whereby locking of the stopper 260 can be safely and rigidly maintained.
As described above, since the derrick 100 is composed of a heavy structure having a high load, the load of the derrick 100 is transferred to the cylinder body 263. At this time, as compared with a typical hydraulic cylinder, the cylinder body 263 can sufficiently endure the load of the derrick 100 through a thick outer plate 263 d and a reinforcing lattice 263 e of the cylinder body 263, thereby providing significantly improved locking performance
As described above, the derrick lift system of an offshore structure according to the embodiments of the present invention can improve drilling workability by enabling safe and easy height adjustment of the derrick using the adjustment unit, and can improve structural stability by lowering the center of gravity of the derrick through the height adjustment of the derrick, as occasion demands.
Although some embodiments have been described above, it will be apparent to those skilled in the art that these embodiments are given by way of illustration only, and that various modifications, changes, alterations, and equivalent embodiments can be made without departing from the spirit and scope of the invention. The scope of the invention should be limited only by the accompanying claims.

Claims

What is claimed is:

1. A derrick lift system of an offshore structure, comprising:

a base plate secured to a drill floor and having a locking groove formed on one side thereof;

a gearbox placed at one inner side of the base plate and coupled to a drive motor;

a relay gear rotably mounted on the base plate to engage with the gearbox;

a pinion rotably mounted on the base plate to engage with the relay gear;

a post supporting a lower end of the derrick to lift or lower the derrick and provided to the other inner side of the base plate to be perpendicularly movable, the post having a rack formed on one surface thereof to engage with the pinion and a locking groove formed on one side thereof;

a stopper mounted on the base plate and selectively inserted into the locking grooves to secure the post at a lifted or lowered location; and

a derrick height adjustment unit placed at one side of the base plate to align the locking grooves through height adjustment of the derrick.

2. The derrick lift system of an offshore structure according to claim 1, wherein the derrick height adjustment unit comprises:

a mounting bracket secured to the base plate; and

a hydraulic cylinder provided to the mounting bracket and adjusting the height of the derrick.

3. The derrick lift system of an offshore structure according to claim 1, wherein the base plate is provided with a sensor detecting alignment of the locking grooves.

4. The derrick lift system of an offshore structure according to claim 1, wherein the pinion comprises a securing pin engaging with the rack, and the base plate is provided with a safety cylinder coupled to the stopper to selectively lock the stopper.

5. The derrick lift system of an offshore structure according to claim 4, wherein the base plate is provided with a ratchet cylinder, the ratchet cylinder comprising a rod and a pivot latch latched to a latch jaw of the pinion through the rod of the ratchet cylinder.

6. The derrick lift system of an offshore structure according to claim 1, wherein the base plate and the post are arranged to support four lower corners of the derrick.

7. The derrick lift system of an offshore structure according to claim 1, wherein the stopper comprises:

a guide plate secured to a side surface of the base plate and having a guide rail formed on an upper surface thereof;

a rod horizontally secured above the guide plate;

a cylinder body disposed to receive the rod therein and to be locked into the locking grooves while moving along the rod by hydraulic force, and having safety grooves formed on upper surfaces of both ends thereof; and

a safety cylinder secured to a side surface of the base plate and coupled into the safety grooves to prevent separation of the cylinder body from the locking grooves when the cylinder body is inserted into the locking grooves.

8. The derrick lift system of an offshore structure according to claim 7, wherein the cylinder body is formed with fluid inlet and outlet ports and a hydraulic chamber, and has safety grooves formed on upper surfaces of both ends thereof