Patent Application
20210131193
This invention applies to the technical field of oil and gas exploration, being represented by a direct connection system between risers made of composite material and horizontal lines installed on the seabed (flowlines), referred to as LRTA (Lower Riser Termination Assembly). The developed system is applicable to hybrid riser and its construction method allows, among other things, the reduction of costs and the optimization of the system assembly/installation time. The disclosed LRTA connection system shows as one of its main advantages being applicable to both rigid and flexible flowlines with no need for any intermediate connection section/equipment between these and the risers.
In marine production systems, the oil produced in the wells located at the bottom of the ocean is transported to a stationary production unit (UEP) by means of pipelines. This set of pipelines is formed by injection and collection lines and conventionally called production system lines.
This set of pipelines comprising the production lines, is basically split into two distinct portions:
Specifically, on vertical pipelines called Risers, this patent applies to the Hybrid Riser Tower for deep and ultra-deep water, as described, for example, in U.S. Pat. No. 6,082,391 (Stolt/Doris). Hybrid Riser Towers are comprised by a rigid riser grouping (steel) provided with floats anchored to the bottom of the sea and tensioned by means of a flotation tank. The system is connected to the UEP through flexible jumpers and connected to rigid pipelines installed on the seabed. Such systems were built and installed, for example, in Girassol, Greater Plutonio and CLOV fields in West Africa.
From the field experience, the high manufacturing cost of this system has been demonstrated due, among other factors, to the large number of components required, building site size, transport cost and structure lifting.
Given this scenario, it was concluded that conventional steel pipes for transportation of fluids make the hybrid riser very heavy, making buoyancy a great challenge. Thus, the concept of Hybrid Riser made of composite material has emerged, as described in U.S. Pat. No. 6,612,370 (Composite Hybrid Riser). The use of composite material for the construction of Hybrid Riser Towers has added, among other things, weight reduction to the structure, since the components made from composite materials weigh only a fraction of the steel components. As a result of the weight saving, the buoyancy and basic work requirements have been reduced.
With the matter of optimized weight from the use of composite materials in Hybrid Riser Towers, the demand has fallen on the need for structural simplifications of the risers×flowlines connection system, very complex in the structures hitherto known and installed.
Proposals for simplifications in the connection system between risers and flowlines are described in the documents U.S. Pat. No. 6,837,311 (B1)—Hybrid Riser Configuration; U.S. Pat. No. 7,025,535 (B2)—Seafloor/surface connecting installation for a submarine pipeline which is connected to a riser by means of at least one elbow pipe element that is supported by a base; U.S. Pat. No. 6,869,253 (B2)—Hybrid Riser or pipe for fluid transfer; U.S. Pat. No. 8,267,179 (B2)—Connection tool with indexing system; US20150047852 (A1)—Installation comprising seabed-to-surface connections of the multi-riser hybrid tower type, including positive-buoyancy flexible pipes; US 2017/0074426—Method for connecting a bottom pipe and riser pipe.
The U.S. Pat. No. 6,837,311 (B1) and U.S. Pat. No. 7,025,535 (B2) show a Hybrid Riser having a base structure connected to its bottom housing the intermediate risers/flowlines and their respective connectors. Such patents reveal advances in the connection system between risers and flowlines, eliminating efforts due to the of the hybrid riser tower movement, but they do not remove the need for risers and flowlines.
The U.S. Pat. No. 6,869,253 (B2) shows another connection proposal between risers and flowlines, seeking to simplify and decrease the number of system components. In that proposal the lower end of the rigid riser or of the rigid riser set is anchored to a drive line named “tendon”. The connection to the rigid flowline is made by a flexible intermediate section and two connectors. In this patent application, the shown LRTA connection system eliminates the need for an intermediate section and additional connectors, simplifying the Hybrid Riser structure.
The U.S. Pat. No. 8,267,179 (B2) shows the connector used for the connection between riser and flexible jumper as a recoverable tool after the connection. The main technical advance driven by the LRTA connection system is that, besides the direct connection, the system features riser guides made of composite material and a bending limiting structure of the risers, which guarantees the direct connection operation with no need for any intermediate section/equipment.
The document US20150047852 (A1) shows a Hybrid Riser system similar to that presented in U.S. Pat. No. 6,082,391 (Stolt/Doris) by modifying the risers connection with flowlines and proposing that such a connection be made with a flexible jumper. Again, there is a need for intermediate connection sections between risers and flowlines, which, in the system proposed in this patent application becomes unnecessary.
The document US2017/0074426 (A1) reveals a riser to flowline connecting method that includes a direct connection connector and devices to limit the flexible pipeline bending. This connection method shows a simplification with regard to the state of the art, as it allows a direct connection between risers and flowlines for cases where the flowline is flexible. However, for rigid flowlines such a direct connection is not possible, and the presence of an intermediate connection section is required. For this reason, the relevant technical advance of the LRTA connection system in this patent application is that the direct connection is made independently of the flowline material. Thus, the connection between risers and flowlines is made directly for both rigid and flexible flowlines, and no intermediate part/equipment is required.
Another aspect addressed in this patent application concerns the innovative construction method developed for the proposed system. The state-of-the-art construction methods must overcome some disadvantages, such as, for example, the need for significantly large construction sites to accommodate the structures during and after assembly. In short, the main disadvantages presented by the state-of-the-art methods and which are overcome by the construction method proposed here are:
Thus, and in order to overcome the problems/limitations of the known state of the art, an innovative connection system was developed between risers made of composite material and flowlines, applicable to the hybrid riser, which in addition to presenting advantages in terms of cost reduction, in the components number and the structure weight, its construction method also shows a great advance against the known methods. The novelty and technical effect of such system also lies in its simplicity in relation to the state of the art.
As explained above, the state-of-the-art connection systems must overcome limitations (existing technical problems) such as, for example: the dependence of equipment/intermediate connection parts between flowlines and risers, increasing the costs and assembly time, limitations as to the flowlines' (rigid or flexible) material, a large area is required for the system to be assembled, overall system weight, among other things. Thus, the developed system has as main goals and advantages:
The present LRTA Risers and Flowlines Connection System is basically comprised of
Generally speaking, the rigid pipeline core is a structural component of the Hybrid Riser, providing support for all of its components. The risers made of composite material, along with a rigid pipeline core form a set of risers, known technically as a “bundle.” The riser guides, made of polymeric material, are connected to the rigid pipeline core by means of clamps incorporated in the guide structure, the function of which is to guarantee the risers position in relation to the rigid pipeline core. In addition to transferring the lateral forces of the risers (due to current drag force and possible vibrations) to the core, the guides also have the purpose of ensuring the axial displacement of the risers, thus avoiding that buckling occurs. The bending limiting Structure of the risers is a metallic structure having compartments that guide risers in the flowlines' direction avoiding the interferences between risers and keeping their curvature within the bending limits informed by the riser pipe supplier, being connected to the rigid pipeline core. Finally, the direct connection connectors are devices that allow the connection of composite material risers to the flowlines, which, in the concerned system, can be both rigid and flexible.
The direct connection between composite material risers and flowlines is one of the major technological advances provided by the system shown here, since in the current state of the art, the connections between risers and flowlines are made using intermediate transfer equipment, such as spools or jumpers.
In the presented system, the direct connection is possible mainly by the association of three factors: the risers are made of composite material, allowing the structure to bend; the use of the riser bending limiter; and the proper sizing of the limiter position and the direct connection connector position with respect to the seabed. The bending limiters are sized according to the bending limit provided by the riser manufacturers.
Another important feature of the disclosed system is the fact that its construction allows free vertical expansion of the risers along the entire structure, even in the bending limiter area, since it works as a guide, and there are therefore no risers×limiter fastening/restriction points.
In addition to the advantages and technological advances achieved with that connection system, its construction method is also innovative compared to those known in the state of the art. While, in the state of the art, the conventional methods require a large assembly and construction area, with a minimum extension, in a straight line to the coast, of 2 km, in the construction method developed for the present system, the required area is significantly reduced, by approximately 6000 m2, with extension, in a straight line to the coast, of 200 m, that is, 10 times less than the length required for the known construction methods.
For the construction of this system, the building site is comprised of: bundle production line with welding and inspection stations of the welds that are carried out on the rigid pipeline core; welding joint lining station; tensioner; riser guide assembly stations; coils of risers made of composite material; offshore launch ramp; and component storage area. In short, the construction is carried out as follows:
1. Welding, inspection and eventual repair of the first section of the rigid pipeline core. The rigid pipeline core is formed by the welding of 12 m pipes;
2. Welding joint lining;
3. Once the first section of the rigid pipeline core is welded, with the lining being applied to the joint, that section passes through the tensioner and is pulled towards the offshore launch ramp (with the aid of a tug boat) allowing the next pipe integrating the rigid pipeline core to enter the welding and lining area, gradually forming the structure of this core. This is done until the entire pipeline core is assembled;
4. The installation station of the riser guides is located after the tensioner. Thus, every time a section of the rigid pipe core under construction goes by the tensioner, it receives in its structure the internal parts of the riser guides, mounted in the riser guide assembly station;
5. When the rigid pipeline core length reaches the offshore launch ramp, the core construction is interrupted for assembly of the riser connection system and flowlines—LRTA. Such a system is prefabricated, consisting of part of the rigid pipeline core, internal parts of the riser guides and part of the riser bending limiting structure, which, at this moment, still has no tubular closing members. The outer parts of the guides and the tubular closing members will only be installed after the composite risers' assembly.
6. Once the LRTA connection system is assembled, the construction of the rigid pipeline core is restarted;
7. As the rigid pipeline core is assembled and the internal parts of the riser guides are installed, the risers made of composite material are positioned and the external part of the riser guides as well as the tubular closing members of the bending limiting structure, are installed;
8. This in-line assembly process continues, repeating the steps until the complete assembly of the system.
It is worth mentioning that the smaller assembly area is possible due to the joint action of the tug boat with the production line, allowing the system to be progressively pulled towards the offshore launching ramp as it is assembled. Such a procedure avoids the need for a large amount of ground storage space for the structure during its assembly and thereafter.
For a better understanding of the advantages of this invention in relation to the state of the art, a comparison between the components necessary for the state-of-the-art systems is presented below (
From table 1 we can clearly see the advantages of the proposed system, especially with regard to the significant decrease in the number of components required to operate the system.
The bundle (3) is composed by: a rigid pipeline core (8)—structural component, manufactured with steel pipe with 18-30 inch nominal diameter, which transfers the sustaining force produced by the float (4) to the anchor (14); by composite risers (9) with 3-14 inch nominal diameter; and guides (10) for the risers (9). Due to the submerged weight of composite risers (9), the bundle (3) has no need for additional floats.
The LRTA Connection System (15) between composite risers (9) and flowlines (13), object of this invention is located at the lower end of the bundle (3). Such a system (15) is comprised of: guides (10B) that direct the composite risers (9) to the final connection position with the flowlines (13); bending limiting structure (11) for the risers (9); and direct connection connectors (12) between risers (9) and flowlines (13). The direct connection connectors (12) have an alignment system between the connector part located on the composite riser (9) and the connector part located on the flowline (13). This system allows an alignment at any position of the connecting axis, that is, it is an alignment system working independently of the position of the parts to be connected. Such a system can be incorporated into the connector parts (12) or into a recoverable tool, or also into both.
The Hybrid Riser design (1) should establish: the assembly position of the bending limiting structure (11) in relation to the seabed; its length; and the direct connection connector position (12) between the composite risers (9) and the flowline (13). Such parameters depend on the flowline resistance (13) and the extreme positions (16) and (16A) the Hybrid Riser (1) considering movement of the UEP (2) and the current, as represented in
The Hybrid Riser (1) construction, provided with the LRTA connection system (15) shown herein, is initiated by the assembly of the rigid pipeline core (8), which is comprised by the welding of 12 m long standard pipes. Thus, after welding (station 27), inspection (station 28), possible repair (station 29) and weld joint lining (station 30) of the first rigid pipeline core (8) section, the section is contained by the tensioner (31) and its end is connected to the tug boat (41). The first rigid pipeline core (8) section is then pulled by the tug boat (41) towards the offshore launch ramp (38), making room for a next pipe to be welded to the core (8). The tug boat (41) pull is compensated by the tensioner (31) and thus, the rigid pipeline core (8) stands still, allowing the system to be built at the stations. At this moment, the section of the rigid pipe core (8) under construction just ahead of the tensioner (31) receives, in its structure, the internal parts of the riser guides (22), mounted in the riser guide assembly station (33). Then, the assembly of the rigid pipeline core continues (8) to the limit where its end reaches the offshore launch ramp (38). Then, the construction of the rigid pipeline core (8) is interrupted for the connection of the LRTA riser and flowline connection system (15). This system (15) is prefabricated, containing the guides (10B) internal parts (22) and the bending limiting structure (11), without the tubular closing members (20A), already assembled. The system (15) is positioned on the offshore launch ramp (38) by a crane (40) to then be connected to the rigid pipeline core (8).
Once the connection system between risers and flowlines (15) is connected to the rigid pipeline core (8), the composite risers (9), stored in coils (35), are connected to the structure (in the internal parts of the guides (33) passing through the compartments (21) and by the guides (10B) of the connection system (15), so that they are properly positioned for connection with the flowlines (13). Then, the tubular closing members (20A) of the bending limiting structure (11) and external parts (23) of the guides (10B) can be fastened using compression tapes (24). Once the connection is completed, the construction of the rigid pipeline core (8) is restarted.
Once the bundle construction is completed (3), it is transported along the offshore launching ramp (38) until it reaches full buoyancy.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/BR2018/050081 | 3/26/2018 | WO | 00 |
