AU2013203237B2

AU2013203237B2 - Marine drilling riser protection system

Info

Publication number: AU2013203237B2
Application number: AU2013203237A
Authority: AU
Inventors: Aaron Paul Begley; Peter Brendon Pezet
Original assignee: Matrix Composites and Engineering Ltd
Current assignee: Matrix Composites and Engineering Ltd
Priority date: 2012-09-25
Filing date: 2013-04-09
Publication date: 2016-06-30
Anticipated expiration: 2033-04-09
Also published as: AU2013203237A1

Abstract

A marine drilling riser protection system including a plurality of protection modules adapted for fitment at spaced intervals along the length of a riser, and a plurality of cover parts, wherein each cover part is adapted to be fitted at one end of the cover part to a first protection module, and at an opposite end of the cover part to a second protection module. 2b 12a Figure 3 Figure 4

Description

MARINE DRILLING RISER PROTECTION SYSTEM Field of the Invention

The invention relates to a marine drilling riser protection system and, more particularly, but not exclusively, to a marine drilling riser protection system having manually interchangeable compact buoyant protection modules.

Background of the Invention A marine drilling riser is a large-diameter pipe that connects a subsea blowout preventer (BOP) stack to a floating surface rig to take mud returns to the surface. Without the riser, the mud would simply spill from the top of the stack onto the seafloor. j

The riser has a significant weight which is supported by its own structure and the surface rig. T o reduce the weight of the riser acting on the rig, it is known to provide drill riser buoyancy modules along the length of the riser. However, the applicant has determined that in the storage, handling and deployment of drilling risers, there is often mechanical damage inflicted upon the buoyancy and, in cases where riser joints have no buoyancy, damage to the auxiliary lines or pipes of the riser itself. Furthermore, the applicant has detennined that existing riser joints may be damaged during stacking and/or may not stack well.

Examples of the invention seek to provide an improved marine drilling riser protection system which overcomes or at least alleviates disadvantages associated with existing systems.

Summary of the Invention

In accordance with one aspect of the present invention, there is provided amarine drilling riser protection system including a plurality of protection modules adapted for fitment at spaced intervals along the length of a riser, and a plurality of cover parts, wherein each cover part is adapted to be fitted at one end of the cover part to a first protection module, and at an opposite end of the cover part to a second protection module, wherein at least some of the protection modules are buoyant and the system is adapted to be tailored along its length to a desired buoyancy by attaching buoyant protection modules along the riser in greater density of relative location (concentration) to increase buoyancy, and by attaching buoyant protection modules along the riser in lower density of relative location (concentration) to decrease buoyancy, and wherein each of the protection modules is adapted to be axially fixable to the riser at any location along the length of the riser.

Preferably, each of the protection modules is buoyant. Where the protection modules are buoyant, they may each be formed to have a density less than the density of sea water (or less than approximately 1000 kg per cubic metre).

Alternatively, the protection modules may be non-buoyant. Where the protection modules are non-buoyant, they may each be formed to have a density greater than the density of sea water (or greater than approximately 1000 kg per cubic metre). This may be desirable for operators who prefer slick joints (which are generally located on the bottom of a riser string) to actually be ballasted. This can give greater control of the string when deploying or retrieving, especially in strong currents.

Even more preferably, each of the protection modules is adapted to be clamped to the riser so as to axially fix the protection module relative to the riser.

Preferably, any distances between two neighbouring protection modules above a threshold distance are spanned with one of said cover parts fitted between said two neighbouring modules. More preferably, any distances between two neighbouring modules below said threshold distance are left uncovered by a cover part.

Preferably, the threshold distance is selected such that a substantially flush finish is achieved along a length of the riser by having throughout the length of the riser protection modules either (i) mutually adjacent or (ii) mutually spaced with spaces between the protection modules covered with a cover part. More preferably, a substantially flush finish is achieved, with a generally circular cross-section such that riser joints can be stacked and deployment snags reduced.

Preferably, the protection modules are sized to allow drilling operators to manually remove or add protection modules as required during a drilling campaign without requiring a shore-based dressing operation.

In a preferred form, each of the protection modules has an axial length approximately the same as an outer diameter of the protection module. More preferably, the ratio of axial length of the protection module to the outer diameter of the protection module is between 0.5 and 1.5.

Preferably, each of the protection modules is non-free-flooding. More preferably, each of the protection modules is formed as a solid body, without an internal free-flooding cavity. In one particular form, each of the protection modules is formed from a solid material. The solid material may have a density of less than 1000kg per cubic metre for buoyancy or greater than 1000kg per cubic metre for non-buoyancy.

Preferably, each of the covers when mounted remains spaced from the riser. More preferably, each of the covers when mounted remains spaced from the riser by the protection modules to which the respective cover is mounted.

In accordance with another aspect of the present invention, there is provided a method of tailoring buoyancy of a marine drilling riser protection system including the steps of: attaching a plurality of buoyant protection modules along the length of a riser; increasing a density of relative location (concentration) of the buoyant protection modules along the length of the riser to increase the buoyancy of the system; and decreasing a density of relative location (concentration) of the buoyant protection modules along the length of the riser to decrease the buoyancy of the system.

Preferably, the method further includes the step of attaching cover parts to span any spaces between neighbouring protection modules, each cover part being fitted at one end of said cover part to a first neighbouring protection module, and being fitted at an opposite end of said cover part to a second neighbouring protection module.

Covers can also span over buoyant modules to provide a sacrificial cover to prevent/reduce running or storage damage to the buoyant modules.

Brief Description of the Drawings

The invention is described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Figure 1 is a side perspective view of a bare riser joint with riser clamps;

Figure 2 is a side perspective view of the riser joint shown with small protection modules fitted at each clamp location;

Figure 3 is a side perspective view of the riser joint shown fitted with protection modules and cover parts;

Figure 4 is a side perspective view of a cover part;

Figure 5 is an upper perspective view of part of a protection module;

Figure 6 is a lower perspective view of the protection module part;

Figure 7 is an end view of the protection module part;

Figure 8 is a bottom view of the protection module part;

Figure 9 is a top view of the protection module part;

Figure 10 is a perspective view of an existing drilling riser protection system;

Figure 11 is a cross-sectional view of the drilling riser protection system shown in Figure 10;

Figure 12 shows riser joints in a stacked storage; and

Figure 13 shows a protection module fixed in place with a strap.

Detailed Description

With reference to Figures 1 to 9, there is shown a marine drilling riser protection system 10 which protects a drilling riser, protects buoyancy of the drilling riser, may be adapted to efficiently change the degree of buoyancy of the drilling riser, and allows good stacking of drilling riser joints.

More specifically, the marine drilling riser protection system 10 in accordance with the example depicted in the drawings includes a plurality of protection modules 12 adapted for fitment at spaced intervals along the length of a drilling riser 14, and a plurality of cover parts 16. Each cover part 16 is adapted to be fitted at one end of the cover part 16 to a first protection module 12a, and at an opposite end of the cover part 16 to a second protection module 12b.

More specifically, Figure 1 shows a bare riser joint (grey) 14 with riser clamps (black) 18, and Figure 2 shows the riser joint 14 shown with small protection modules 12 fitted at each clamp location. Advantageously, the system comprises a number of small, discrete modules, with a similar profile to that of buoyancy modules, located along the length of the riser joint 14. Typically, the protection modules 12 may be located at every riser clamp location, however the protection modules 12 may also be located at other locations along the length of the riser joint 14.

Each of the protection modules 12 may be buoyant so as to reduce the weight of the drilling riser 14 carried by the surface rig. The system 10 is adapted to be tailored to a desired buoyancy by attaching protection modules 12 along the riser 14 in greater density of relative location (concentration) to increase buoyancy, and by attaching protection modules along the riser 14 in lower density of relative location (concentration) to decrease buoyancy. In other words, with reference to Figure 2, if greater buoyancy is desirable the protection modules 12 may be fitted to the riser 14 at additional locations to those shown, and if reduced buoyancy is required one or more of the protection modules 12 shown may be removed.

To facilitate the tailoring of the system 10, each of the protection modules 12 is adapted to be axially fixable to the riser 14 at any location along the length of the riser 14. This may be achieved by each of the protection modules 12 being adapted to be clamped to the riser 14 so as to axially fix the protection module 12 relative to the riser 14. Each of the protection modules 12 may comprise a pair of like protection module parts 20, a single one of which is shown in Figures 5 to 9. The protection module parts 20 may be fitted together around the riser 14 with bolts (or ties/straps 26 - see Figure 13) to hold together the parts 20. Where a strap 26 is used, the strap 26 may be provided with a tensioner. If bolts are used, they may be inserted through apertures 22 so that the parts 20 can be fastened together and clamped against axial displacement along the riser 14. As shown in Figure 4, each cover part 16 may also be provided with recessed apertures 24 to enable the cover parts 16 to be fastened to protection modules 12 at either end. The recessed apertures 24 may be configured so as to leave a gap between the cover parts 16 and the protection modules 12 to provide further protection to the protection modules 12 in the event that the cover parts 16 are dinted inwardly. When the cover parts 16 are fastened to the protection modules 12 at either end, the cover parts 16 overlap the protection modules 12 as shown in Figure 3. The cover parts 16 may be of different lengths, as shown in Figure 3.

Any distances between two neighbouring protection modules 12 above a threshold distance may be spanned with one of said cover parts 16 fitted between said two neighbouring modules 12a, 12b. In particular, any distances between two neighbouring modules 12a, 12b below said threshold distance may be left uncovered by a cover part 16. The threshold distance may be selected such that a substantially flush finish is achieved along a length of the riser (see Figure 3) by having throughout the length of the riser 14 protection modules either (i) mutually adjacent or (ii) mutually space with spaces between the protection modules 12 covered with a cover part 16. As shown in Figure 3, the substantially flush finish may be achieved with a generally circular cross-section such that riser joints 14 can be stacked in the manner shown in Figure 12, without causing damage to the riser joints 14 and without causing damage to the buoyancy of the riser joints 14. The generally circular cross-section of the marine drilling riser protection system 10 may provide better protection and better stacking ability than existing drilling riser protection systems, for example as shown in Figures 10 and 11.

The protection modules 12 may be sized to allow drilling operators to manually remove or add protection modules 12 as required during a drilling campaign without requiring a shore-based dressing operation. More specifically, each of the protection modules may have an axial length approximately the same as an outer diameter of the protection module. Even more specifically, the ratio of the axial length of the protection module 12 to the outer diameter of the protection module 12 may be between 0.5 and 1.5. For example, in the example shown in the drawings, the plan view of the protection module part 20 is generally square (see Figure 8) such that the axial length of the protection module 12 is in the same general order as the outer diameter of the protection module 12.

Each of the protection modules 12 may be formed as a solid body, without an internal free-flooding cavity. More specifically, in a non-limiting example, each of the protection modules 12 may be formed from a solid material having a density of between 300kg per cubic metre and 600kg per cubic metre. In this way, each of the protection modules 12 may provide buoyancy to the riser 14 as the density of sea water is typically around 1,025kg per cubic metre. The absence of internal free-flooding cavities may facilitate easy movement of the protection modules 12 through sea water with reduced resistance.

Advantageously, the small protection modules 12 provide the ability to stack non buoyed joints vertically on top of one another. These protection modules 12 could typically be made using the same process and materials that existing riser buoyancy modules are made from. The cover parts 16 linking the small protective modules 12 may be made from a tough, resilient, abrasive and impact resistance material such as the material known as Twintex, Aramid, polycarbonate, etc.

It is beneficial that the cover parts 16 mount to the small protection modules 12 and do not need to interface with the riser lines themselves, however there could be a facility to cable tie the cover parts 16 to the riser lines if this provided necessary or advantageous. The result is a flushed finish riser joint (see Figure 3) that may be stored/stacked to heights similar to joints with buoyancy and a joint that is resistant to the normal damage seen when running or handling their joints. In addition, the small protective modules may be made from the same material or process as existing buoyancy modules. Instead of spanning the gap between protective modules 12 with cover parts 16, the gap could be filled with more of the small buoyancy modules 12. Due to the smaller physical dimensions and weight of these modules 12, they can provide the ability for the drilling operators to remove or add buoyancy modules as required during a drilling campaign, rather than require specialist and bulky handling equipment that typically requires a shore-based dressing operation.

For example, a damaged buoyancy module 12 may be replaced "on the fly" during a drilling campaign resulting in the elimination of whole spare buoyant joints, replaced with a lower quantity of smaller, easily installed, buoyancy modules. An added benefit to the smaller modules 12 is that bending loads imparted by riser deflection into the buoyancy modules and running loads through rotary tables are of a lower magnitude than their normal length equivalents. This means less chance of damage to the equipment. Further, covers could also be fitted along the whole length of buoyant joints to provide an even greater level of protection and act as a sacrificial barrier to running damage. The cover parts 16 may easily be replaced.

Existing protection systems include units which are hollow and must be free-flooding to prevent collapse at depth due to hydrostatic pressures. The free-flooding cavities results in greater loads being imparted into the riser running equipment due to the amount of water that fills the cavities when deployed. The stacking height ability of the existing system shown in Figures 10 and 11 may be limited, and the radial fins may be subject to breakage.

Advantageously, the cover parts 16 can be placed over the top of "normal" (existing) buoyancy units to provide a sacrificial protection from running, handling and storage damage.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A marine drilling riser protection system including a plurality of protection modules adapted for fitment at spaced intervals along the length of a riser, and a plurality of cover parts, wherein each cover part is adapted to be fitted at one end of the cover part to a first protection module, and at an opposite end of the cover part to a second protection module, wherein at least some of the protection modules are buoyant and the system is adapted to be tailored along its length to a desired buoyancy by attaching buoyant protection modules along the riser in greater density of relative location (concentration) to increase buoyancy, and by attaching buoyant protection modules along the riser in lower density of relative location (concentration) to decrease buoyancy, and wherein each of the protection modules is adapted to be axially fixable to the riser at any location along the length of the riser.
2. A marine drilling riser protection system as claimed in claim 1, wherein each of the protection modules is buoyant.
3. A marine drilling riser protection system as claimed in claim 1, wherein each of the protection modules is adapted to be clamped to the riser so as to axially fix the protection module relative to the riser.
4. A marine drilling riser protection system as claimed in any one of claims 1 to 3, wherein any distances between two neighbouring protection modules above a threshold distance are spanned with one of said cover parts fitted between said two neighbouring modules.
5. A marine drilling riser protection system as claimed in claim 4, wherein any distances between two neighbouring modules below said threshold distance are left uncovered by a cover part.
6. A marine drilling riser protection system as claimed in claim 4 or claim 5, wherein the threshold distance is selected such that a substantially flush finish is achieved along a length of the riser by having throughout the length of the riser protection modules either (i) mutually adjacent or (ii) mutually spaced with spaces between the protection modules covered with a cover part.
7. A marine drilling riser protection system as claimed in claim 6, wherein a substantially flush finish is achieved, with a generally circular cross-section such that riser joints can be stacked.
8. A marine drilling riser protection system as claimed in any one of claims 1 to 7, wherein the protection modules are sized to allow drilling operators to manually remove or add protection modules as required during a drilling campaign without requiring a shore-based dressing operation.
9. A marine drilling riser protection system as claimed in any one of claims 1 to 8, wherein each of the protection modules has an axial length approximately the same as an outer diameter of the protection module.
10. A marine drilling riser protection system as claimed in claim 9, wherein the ratio of axial length of the protection module to the outer diameter of the protection module is between 0.5 and 1.5.
11. A marine drilling riser protection system as claimed in any one of claims 1 to 10, wherein each of the protection modules is non-free-flooding.
12. A marine drilling riser protection system as claimed in any one of claims 1 to 11, wherein each of the protection modules is formed as a solid body, without an internal free-flooding cavity.
13. A marine drilling riser protection system as claimed in any one of claims 1 to 12, wherein each of the protection modules is formed from a solid material which has a density of less than 1000kg per cubic metre.
14. A marine drilling riser protection system as claimed in any one of claims 1 to 13, wherein each of the covers when mounted remains spaced from the riser.
15. A marine drilling riser protection system as claimed in claim 14, wherein each of the covers when mounted remains spaced from the riser by the protection modules to which the respective cover is mounted.
16. A marine drilling riser protection system as claimed in claim 1, comprising non-buoyant protection modules.
17. A method of tailoring buoyancy of a marine drilling riser protection system including the steps of: Providing a marine drilling riser protection system according to claim 1; attaching a plurality of buoyant protection modules along the length of the riser; increasing a density of relative location (concentration) of the buoyant protection modules along the length of the riser to increase the buoyancy of the system; and decreasing a density of relative location (concentration) of the buoyant protection modules along the length of the riser to decrease the buoyancy of the system.
18. A method of tailoring buoyancy of a marine drilling riser protection system as claimed in claim 17, further including the step of attaching cover parts to span any spaces between neighbouring protection modules, each cover part being fitted at one end of said cover part to a first neighbouring protection module, and being fitted at an opposite end of said cover part to a second neighbouring protection module.
19. A marine drilling riser protection system substantially as hereinbefore described with reference to the accompanying drawings.
20. A method of tailoring buoyancy of a marine drilling riser protection system substantially as hereinbefore described with reference to the accompanying drawings