OPEN FACE DERRICK

Abstract

An offshore oil derrick having a derrick tower, a derrick substructure, and a drilling floor. The derrick substructure is cantileverly supported by a hull, the derrick tower is supported by the derrick substructure, and the drilling floor is located on top of the derrick substructure below the derrick tower. The drilling floor comprises a v-door on the fore end; a well center approximately 40-50% of the floor length from the aft end; a plurality of setback areas; drawworks on the starboard side; a dynamic brake on the aft end of the drawworks; and a driller's station. The derrick may further include a spare line spool connected to the derrick substructure on the forward end of the derrick.

Description

FIELD OF THE INVENTION

This invention relates generally to oil and gas drilling platforms, and more particularly to open face derricks and drilling floor arrangements.

DESCRIPTION OF THE RELATED ART

Oil and gas drilling derricks are often supported by a hull via a cantilever. In such derricks, the design of the derrick tower and the layout of the drilling floor are vitally important to the balance of forces and the resulting load on the cantilever and the hull. One type of cantilever drilling derrick is utilized in offshore drilling wherein the drilling derrick is supported on cantilever beams. See for example, Branham et al., U.S. Pat. No. 3,477,235.

Welsh, U.S. Pat. No. 6,481,931, recognizes that modem drilling realities result in overload of the cantilever, and attempts to balance the loads in a way that reduces overload. Welsh, however, requires an asymmetrical derrick tower with a well center line located one third of the floor length from the aft end of the drilling floor. Welsh further requires an undesirable arrangement of elements on the drilling floor.

It is, therefore, desirable to provide a drilling derrick supported by a hull via a cantilever that is designed to balance the loads in a way that reduces overload while maintaining a symmetrical derrick.

It is further desirable to provide such a drilling derrick with a well center closer to the center of the drilling floor.

It is further desirable to provide such a drilling derrick with a more practical arrangement of elements on the drilling floor.

SUMMARY OF THE INVENTION

In general, in a first aspect, the present invention relates to an offshore oil and gas drilling derrick with a forward end, an aft end, a starboard side, and a port side, comprising a derrick tower, a derrick substructure, and a drilling floor. The derrick substructure is cantileverly supported by a hull, the derrick tower is supported by the derrick substructure, and the drilling floor is located on top of the derrick substructure below the derrick tower.

In one non-limiting embodiment, the drilling floor comprises a v-door on the fore end; a well center approximately 40-50% of the floor length from the aft end; a plurality of setback areas; drawworks on the starboard side; a dynamic brake on the aft end of the drawworks; and a driller's station. The derrick may further comprise a spare line spool connected to the derrick substructure on the forward end of the derrick. The spare line spool may be connected to the derrick substructure toward the port side of the forward end of the derrick.

The plurality of setback areas may be located on either side of the v-door on the forward end. The well center may be centered on the drilling floor, and the derrick tower may also be centered on the drilling floor and may be symmetrical and have a square base. The derrick may further comprise pipe handling equipment such that an operator may build derrick triple stands outside the setback area in an unencumbered space on the drilling floor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an open face derrick, including the derrick tower, derrick substructure, and drilling floor constructed in accordance with the present invention; and

FIG. 2 is a plan view of the drilling floor.

Other advantages and features will be apparent from the following description and from the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The devices and methods discussed herein are merely illustrative of specific manners in which to make and use this invention and are not to be interpreted as limiting in scope.

While the devices and methods have been described with a certain degree of particularity, it is to be noted that many modifications may be made in the details of the construction and the arrangement of the devices and components without departing from the spirit and scope of this disclosure. It is understood that the devices and methods are not limited to the embodiments set forth herein for purposes of exemplification.

Referring to the figures of the drawings, wherein like numerals of reference designate like elements throughout the several views, and initially to FIG. 1, an offshore oil derrick has a derrick tower 1, a derrick substructure 2, and a drilling floor 3. The derrick substructure 2 is cantileverly supported by a hull (not shown) via cantilever beams 16, and the derrick substructure 2 supports the derrick tower 1. The derrick tower 1 may have a square base and may be symmetrical. The drilling floor 3 is located above the derrick substructure 2 and below the derrick tower 1.

As seen in FIG. 2, the drilling floor 3 has a forward end 4, an aft end 5, a port side 6, and a starboard side 7. The drilling floor 3 has a v-door 8 on the forward end 4. The v-door 8 may be centered along the forward end 4. A well center 9 is located approximately 40-50% of the floor length from the aft end 5. The well center 9 may be centered between the port side 6 and starboard side 7. The well center 9 may additionally or alternately be centered between the forward end 4 and the aft end 5. The drilling floor 3 also has drawworks 10 on the starboard side 7, a dynamic brake 11 on the aft end 5 of the drawworks 10, and a driller's station 12. A spare line spool 13 may be connected to the derrick substructure 2 on the forward end 4. The spare line spool 13 may be located toward the port side 6 of the forward end 4.

The drilling floor 3 has a plurality of setback areas 14. The setback areas 14 may be positioned on either side of the v-door 8 on the forward end 4. If so, the v-door 8 may be a special v-door to accommodate the setback areas 14. However, the setback areas 14 may have variable positions with no restriction due to the geometry of the overall derrick structure.

The feet of the derrick tower may be located on the drilling floor at locations 15. A variety of other elements may also be found on the drilling floor 3, including but not limited to a choke manifold, a standpipe manifold, a deadline anchor, a degagger, and guide tracks.

The downhole tubulars come in a certain length or lengths. In some applications, a pair of tubular is joined together in a double stand so that each tubular does not have to be connected or disconnected. This increases the speed and efficiency of installation and removal.

Off line stand building is becoming a major priority on jack up rigs. The present process allows the operator to build derrick triple stands using special pipe handling equipment in the derrick. The open face derrick design allows this operation to be done outside the setback areas 14 in an unencumbered space. The constructed triples are then racked in a racking platform. Expansion of racking capacity is not limited by the existing space within the four sides of the derrick. The open face derrick allows for expanded racking capacity without major modification to the derrick. The only limitation is the structural strength of the derrick to withstand the eccentric load of the setback area under field tow or high wind conditions.

Whereas, the devices and methods have been described in relation to the drawings and claims, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.

Claims

1. An offshore oil derrick with a forward end, an aft end, a starboard side, and a port side, comprising:

a derrick tower;

a derrick substructure where said derrick substructure is cantileverly supported by a hull, wherein said derrick tower is supported by said derrick substructure; and

a drilling floor located on top of said derrick substructure below said derrick tower; where said drilling floor includes:

a v-door on the fore end;

a well center approximately 40-50% of the floor length from the aft end;

a plurality of setback areas;

drawworks on the starboard side;

a dynamic brake on the aft end of the drawworks; and

a driller's station.

2. The offshore oil derrick of claim 1 further comprising a spare line spool connected to the derrick substructure on the forward end of the derrick.

3. The offshore oil derrick of claim 2 where said spare line spool is connected to the derrick substructure toward the port side of the forward end of the derrick.

4. The offshore oil derrick of claim 1 where said plurality of setback areas are located on either side of said v-door on the forward end.

5. The offshore oil derrick of claim 1 where said well center is centered on said drilling floor.

6. The offshore oil derrick of claim 5 where the derrick tower is symmetrical.

7. The offshore oil derrick of claim 6 where the derrick tower has a square base.

8. The offshore oil derrick of claim 1 further comprising pipe handling equipment such that an operator may build derrick triple stands outside the setback area in an unencumbered space on the drilling floor.