GB2458314A

GB2458314A - Method and apparatus for racking drill pipe stands on a drill floor

Info

Publication number: GB2458314A
Application number: GB0804738A
Authority: GB
Inventors: Katherine Louise Mantle
Original assignee: KT DRILLING CONSULTANTS Ltd
Current assignee: KT DRILLING CONSULTANTS Ltd
Priority date: 2008-03-14
Filing date: 2008-03-14
Publication date: 2009-09-16
Also published as: NO343154B1; NO20101396L; GB0804738D0; WO2009112842A1

Abstract

A method of vertically racking drill pipe stands on a drill floor comprises arranging a row of drill pipe stands in a line on the drill floor, arranging a second row of drill pipe stands adjacent the first row, the ends of the second row being elevated 38 from the drill floor. Thereafter subsequent alternate rows of drill pipe stands are set on the drill floor and elevated from the drill floor. The elevated drill pipe stands may be supported on benches, the upper surfaces of which may be covered in reinforced nylon. Also disclosed is a racking system for pipe stands in which the alternate rows of pipe stands can be raised manually by means of a lever.

Description

Title: Method and apparatus for racking drill pipe stands on a drill floor The present invention relates to a method and apparatus for racking drill pipe stands on a drill floor and particularly but not exclusively to a method of racking drill pipe stands on a drill floor for use in Extended Reach Drilling (ERD) of oil wells.

Backgound to the Invention Prior to drilling an oil well, for example, on an offshore platform or oil rig, stands of drill pipe are vertically racked in the derrick and rest on the drill floor. Each drill pipe stand typically comprises three lengths of drill pipe connected together at joints, known as box and pin connections or tool joints. Each joint has a larger diameter than the drill pipe between joints, for example, a drill pipe of 6.625" diameter (approximately 168mm) typically has a tool joint diameter of 8.25" diameter (approximately 210mm).

At present the drill pipe stands are arranged on the drill floor in a roughly square array, for example, 10 drill pipe stands wide by 10 drill pipe stands across and the number of drill pipe stands is limited by the size of the drill floor. The drill pipe stands are each typically 90 feet (approximately 27.69m) high, and therefore a rig having two 10 x 10 arrays provides for the potential to continuously drill 18,000 feet (approximately 5538m).

Until recently, this length of drill pipe has often been sufficient, but there is now a need to drill Extended Reach wells, which may involve drilling up to over 9000m.

Most platforms were built in the 1980's and do not have drill floors capable of storing sufficient drill pipe in the conventional manner. This means that drill pipe has to be transferred to the drill floor during drilling. At sea, transferral of drill pipe is extremely costly and dangerous. For safety reasons, the unloading of pipe by crane and the moving of drill pipe around a rig is prohibited when the weather conditions are such that the prevailing wind is, for example, greater than 40 knots and/or the sea state has a heave of more than 3m. In the North sea these conditions are relatively common and time delays during drilling are often encountered.

Well bore stability is often time dependent and time delays can often result in the loss of a section of well being drilled. Instability and collapse of a well bore results in extremely costly and time consuming remedial action including re-drilling and cementing of the bore. Furthermore, differential sticking, in which the drill string cannot be moved, can occur and can result in losing the section of well being drilled and the bottom hole assembly often including a radioactive source being lost downhole. Fishing operations to retrieve lost tools are extremely expensive and time consuming, and are not guaranteed to succeed. If an advanced stage of an extended reach well is lost, the loss can easily run into several million US dollars, not including losses.due to lost production time from the well.

Statement of Invention

According to a first aspect of the present invention there is provided a method of vertically racking drill pipe stands on a drill floor, comprising arranging a row of drill pipe stands in a line on the drill floor, arranging a second row of drill pipe stands adjacent the first row, the ends of the second row being elevated from the drill floor, and thereafter arranging subsequent alternate rows of drill pipe stands on the drill floor and elevated from the drill floor.

It is an advantage of the invention that by elevating alternate rows of drill pipe stands, that the increased diameter joints of the drill pipe stands can be vertically offset in adjacent rows. This means that an increased number of drill pipe stands can be accommodated on a limited size of drill floor. The magnitude of the offset is at least the length of each drill pipe stand joint. In other words, the invention allows significantly more stands of drill pipe to be stored on a given area of drill floor than is currently possible.

Central axes of adjacent rows of drill pipe stands may be arranged in a substantially rectangular array.

Preferably central axes of adjacent rows of drill pipe stands are arranged in a substantially diagonal array.

By offsetting the drill pipe stands in adjacent rows, a further increased number of dnll pipe stands can be racked in a limited space of a drill floor.

Preferably the drill pipe stands are rested on their lower ends.

Preferably the elevated drill pipe stands are rested on a supporting structure comprising parallel rows of support members.

Preferably the support members comprise steel benches, the upper surface of each bench being covered with a reinforced nylon cover.

Preferably each reinforced nylon cover is profiled to seat the pm end of a plurality of drill pipe stand ends.

Preferably the profiling includes a plurality of upwardly extending spigots, each adapted to be received in a drill pipe stand end.

Preferably each spigot is movable between a raised position and a lowered position.

Each spigot may be moved by a manual lever or other drive means.

An advantage of the manual lever is that its position gives a visual indication of the position of the respective spigot, which may be obscured by the end of a drill pipe stand.

Preferably the support members are removably fastened to the drill floor.

Preferably the upper ends of the drill pipe stands are located in a support member disposed vertically above the drill floor.

Alternatively the drill pipe stands are suspended from a gantry.

According to a second aspect of the present invention there is provided apparatus for vertically racking drill pipe stands on a drill floor comprising a supporting structure, the supporting structure including parallel rows of support members.

S Preferably each reinforced nylon cover is profiled to seat the pin end of a plurality of drill pipe stand ends.

A manually operated lever may be provided for moving each spigot between the raised and lowered positions.

Preferably the support members are adapted to be removably fastened to a drill floor.

According to a third aspect of the present invention there is provided an array of drill pipe stands arranged vertically, alternate rows of drill pipe stands being vertically offset.

The central axes of adjacent rows of drill pipe stands may be arranged in a substantially rectangular array.

Preferably central axes of adjacent rows of drill pipe stands are arranged in a substantially diagonal array. This allows even closer packing of the drill pipe.

Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic plan view of part of an array of drill pipe stands arranged in a known arrangement; Figure 2 shows schematic plan view of part of an array of drill pipe stands arranged in a first arrangement of the invention; Figure 3 shows schematic plan view of part of an array of drill pipe stands arranged in a second arrangement of the invention; Figure 4 shows a schematic side view of four drill pipe stands forming part of an array of drill pipe stands in accordance with the invention; Figure 5 shows a schematic end view of a bench for supporting drill pipe stands; Figure 6 shows a schematic side view of part of the bench of Figure 5.

Description of Preferred Embodiment(s)

Referring firstly to Figure 1 a prior art array of racked drill pipe stands 12 in a derrick 14 of a drill floor is indicated generally at 10. The drill pipe stands 12 are arranged in rows of ten stands 12, and there are ten rows, of which two complete rows are shown. The drill pipe stands 12 rest onto the floor of the derrick 14, which is usually covered with a timber covering to protect the ends of the drill pipe stands 12.

Referring also to Figure 4, each drill pipe stand 12 includes three sections of drill pipe, a lower section 16, a middle section 18 and an upper section 20. The sections 16,18, 20 are joined together at respective tool joints 22,24. The joints 22,24 each comprise a box tool and a pin tool provided on respective ends of the drill pipes to be connected together. Typically the tool joints have a larger outside diameter than the drill pipe between joints, for example, a drill pipe of 6.625" outside diameter (approximately 168mm) typically has a tool joint outside diameter of 8.25" diameter (approximately 210mm). Each joint is approximately 21" long (approximately 0.533m). The drill pipe stands are typically 90 feet (approximately 27.69m) long.

In the prior art arrangement shown in Figure 1, it will be understood that the minimum size of the array is approximately 82.50" square, which is determined by the outside diameter of the joints 22,24, assuming that the drill pipe stands are tightly packed and the joints of adjacent drill pipe stands 12 touch one-another.

Referring now to Figure 2, a first array of the invention is indicated generally at 26.

The array 26 is provided in the same available space as the prior art array 10, but there are six rows 28 of ten drill pipe stands (two of which are shown) and five alternate rows 30 of ten drill pipe stands (one of which is shown). In other words, in the same available space there are 110 drill pipe stands 12, rather than 100. The tighter packing is achieved by lifting the alternate rows 30 of drill pipe stands by at least the length of the joints 22,24, ie a distance of greater than 21" (approximately 0.533m). The drill pipe stands are arranged in a substantially rectangular array, ie the central axes of four adjacent drill pipe stands form the vertices of a square.

Referring to Figure 3, a second array of the invention is indicated generally at 32. In this array there are seven rows 34 of ten drill pipe stands (two of which are shown) and six rows 36 of nine drill pipe stands (one of which is shown). Therefore, in this arrangement, in the same available space there are 124 drill stands. The tighter packing in this arrangement is achieved by lifting the alternate rows 36 of drill pipe stands by at least the length of the joints 22,24, and by offsetting adjacent rows by a distance equivalent to the radius of the joints. In other words the drill pipe stands of adjacent rows are offset vertically and horizontally. Therefore, the drill pipe stands are arranged in a substantially diagonal array, ie the central axes of four adjacent drill pipe stands form the vertices of a parallelogram. This arrangement can also be seen in Figure, in which the vertical offset is indicated at 38.

Referring also to Figures 5 to 7, in the arrays 26,32 of Figures 2 and 3, the rows 30,36 of elevated drill pipe stands 12 are supported on metal benches 40, which can be bolted in position on the derrick, as desired. The benches 40 are preferably fabricated from steel, which may be galvanised. Each bench comprises a plurality of spaced vertical supports 42 welded to the underside of an inverted U-section beam 44. The base of each support 42 is welded to a base plate 46, which can be bolted to the derrick by bolts 48. Reinforcing webs 50 are provided between each base plate 46 and support 42.

A longitudinal plate 52 is welded to the upper facing surface of the beam 44, Onto which is mounted a reinforced nylon cover layer 54, in order to protect the ends of the drill pipe stands 12. The layer 54 and steel plate 52 can be externally profiled, as indicated in Figure 7, ie with enlarged areas for receiving the ends of the drill pipe stands 12. The nylon layer 54 can also be dished and provided with vertically extending spigots (not shown) for locating the ends of the drill pipe stands. The spigots ensure that the ends of the drill pipe stands are securely held against lateral movement. The spigots are optionally movable between a raised position, in which the spigots extend above the substantially upper planar surface of the layer 54 and a lowered position in which the spigots are lowered into the substantially upper planar surface of the layer 54. The spigots can be raised and lowered by a hand operated lever, or other means, as desired, and can be locked in either position. The position of a handle may provide a visual indication of the position of a respective spigot.

The upper ends of the drill pipe stands 12 are laterally supported in conventional manner in a finger board (not shown).

It is also envisaged that in another embodiment of the invention, not shown, the drill pipe stands 12 could be supported from a gantry. However, this is not particularly desirable, because of the problems of manufacturing the gantry, the weigju of the gantry and the difficulties of getting the drill pipe stands 12 into the gantry.

In some circumstances, it is possible, due to a specific rig floor design, to add an extra row to the or each edge of an array of drill pipe stands. The length of the drill pipe stands may also vary, for example, each drill pipe stand may comprise two 15m drill pipes connected together at a box and pin connection or tool joint.

In use, the arrays 26, 32 provide a method of racking drill pipe stands on a denick and achieve an increased storage capacity of between around 24% to 39%, depending on the particular derrick and drill pipe diameter. This means that deeper wells can be drilled, before the derrick needs to be replenished with drill pipe. The method is particularly advantageous for off-shore applications, where space is limited, but also finds application in jungle areas and on platforms in tidal areas, where space is also limited. There are significant cost advantages in using the method, particularly in drilling ERD wells, because it may be that the increased capacity of drill pipe results in continuous drilling to depth, without drilling delays for replenishment, thus potentially avoiding differential sticking and br instability and collapse in the well bore.

There are also considerable health and safety benefits in using the racking method, resulting from not needing to replenish drill pipe during drilling. Moving drill pipe on a rig requires simultaneous hazardous operations, time consuming HAZOP assessments and Risk Assessments to be performed. If all of the drill pipe is on a rig prior to drilling, there is little risk of weather or health and safety affecting the drilling

timetable.

Claims

CLAIMSI. A method of vertically racking drill pipe stands on a drill floor, comprising arranging a row of drill pipe stands in a line on the drill floor, arranging a second row of drill pipe stands adjacent the first row, the ends of the second row being elevated from the drill floor, and thereafter arranging subsequent alternate rows of drill pipe stands on the drill floor and elevated from the drill floor.
2. A method as claimed in claim 1, in which central axes of adjacent rows of drill pipe stands are arranged in a substantially rectangular array.
3. A method as claimed in claim 1, in which central axes of adjacent rows of drill pipe stands are arranged in a substantially diagonal array.
4. A method as claimed in any one of claims I to 3, in which the drill pipe stands are rested on their lower ends.
5. A method as claimed in any one of claims I to 4, in which the elevated drill pipe stands are rested on a supporting structure comprising parallel rows of support members.
6. A method as claimed in claimS, in which the support members comprise steel benches, the upper surface of each bench being covered with a reinforced nylon cover.
7. A method as claimed in claim 6, in which each reinforced nylon cover is profiled to seat the pin end of a plurality of drill pipe stand ends.
8. A method as claimed in claim 7, in which the profiling includes a plurality of upwardly extending spigots, each adapted to be received in a drill pipe stand end.
9. A method as claimed in claim 8, in which each spigot is movable between a raised position and a lowered position.
10. A method as claimed in claim 9, in which each spigot is movable using a manually operated lever.
11. A method as claimed in any one of claims 5 to 10, in which the support members are removably fastened to the drill floor.
12. A method as claimed in any preceding claim, in which the upper ends of the drill pipe stands are located in a support member disposed vertically above the drill floor.
13. A method as claimed in any one of claims 1 to 3, in which the drill pipe stands are suspended from a gantry.
14. Apparatus for vertically racking drill pipe stands on a drill floor comprising a supporting structure, the supporting structure including parallel rows of support members.
15. Apparatus as claimed in claim 14, in which the support members comprise steel benches, the upper surface of each bench being covered with a reinforced nylon cover.
16. Apparatus as claimed in claim 15, in which each reinforced nylon cover is profiled to seat the pin end of a plurality of drill pipe stand ends.
17. Apparatus as claimed in claim 16, in which the profiling includes a plurality of upwardly extending spigots, each adapted to be received in a drill pipe stand end.
18. Apparatus as claimed in claim 17, in which each spigot is movable between a raised position and a lowered position.
19. Apparatus as claimed in claim 18, in which a manually operated lever is provided for moving each spigot.
20. Apparatus as claimed in any one of claims 14 to 19, in which the support members are adapted to be removably fastened to a drill floor.
21. An array of drill pipe stands arranged vertically, alternate rows of drill pipe stands being vertically offset.
22. An array of drill pipe stands as claimed in claim 21, in which central axes of adjacent rows of drill pipe stands are arranged in a substantially rectangular array.
23. An array of drill pipe stands as claimed in claim 21, in which central axes of adjacent rows of drill pipe stands are arranged in a substantially diagonal array.
24. A method of vertically racking drill pipe stands on a drill floor substantially as described herein with reference to and as illustrated in Figures 2 to 7 of the accompanying drawings.
25. Apparatus for vertically racking drill pipe stands on a drill floor substantially as described herein with reference to and as illustrated in Figures 2 to 7 of the accompanying drawings.
26. An array of drill pipe stands substantially as described herein with reference to and as illustrated in Figures 2 to 7 of the accompanying drawings.