Lateral clamping module for rigid risers

Abstract

The Lateral Locking Module (LTM) is a device designed to support the bending and shear loads of the rigid riser termination, preventing fatigue, wear, and internal shock to the support pipe. The LTM is activated remotely from the production unit during the final pull in stage, without the need for diving, or directly from a ROV. The LTM also allows for lateral unlocking of the riser without diving.

Description

FIELD OF THE INVENTION

[0001] The present invention falls within the field of petroleum engineering. More specifically, the present invention relates to auxiliary elements for locking rigid risers.BACKGROUND OF THE INVENTION

[0002] Risers are suspended intermediate sections of subsea oil production lines, located between the wet Christmas trees or manifolds and the platforms. They can be used to conduct fluids from the surface to the seabed, such as injection and export risers, or in the opposite direction.

[0003] Rigid risers are generally tubular and inflexible risers, typically used in deepwater because they allow for large diameters and operate with a wider range of internal pressures. During a pull in operation, the prior art employs divers to operate the riser locking modules. This solution is costly and time-consuming, in addition to being risky for the divers.STATE OF THE ART

[0004] The article "Rigid Risers for Floating Production Systems in Deepwater Field Developments," by McShane et al., March 1999, discloses a large-diameter deepwater rigid riser design that allows floating production systems (FPSs) to export sales-quality product through a pipeline, even during extreme storms. The design concept incorporates a helical base (formed from steel tube), a vertical riser, and a flexible joint connection to the FPS. Its strengths are its transport capacity, export capacity, and ability to accommodate large vessel movements and environmental loads. The article reviews the design, considers how key parameters influence the riser configuration, and summarizes its range of applications. Implementing this design would allow FPSs to export large amounts of processed product through a pipeline without having to use shuttle tankers or leave the station, thus maximizing efficient field production. With field depletion, there is potential to continue using the riser as an offloading system. With the potential increase in FPSs being used in the Gulf of Mexico for deepwater developments, this combination of technologies (FPS, rigid riser, and pipelines) could potentially provide a cost-effective field development solution.SUMMARY OF THE INVENTION

[0005] The present invention proposes the use of a lateral locking module (LTM) to lock rigid risers during a pull in operation. The LTM is a device that supports the bending and shear loads of the rigid riser termination, avoiding fatigue and wear problems resulting from movement and shock within the support pipe. The LTM is remotely activated from the production unit during the final pull in stage without the need for diving. Alternatively, the LTM can be activated by a ROV (Remotely Operated Vehicle). The LTM can also be unlocked from the riser remotely or by ROV.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present invention will be described below with reference to its typical embodiments and also with reference to the accompanying drawings. Figure 1A is a side view of the lateral locking module (LTM) in a closed configuration according to the present invention. Figure 1B is a rear view of the lateral locking module (LTM) in a closed configuration according to the present invention. Figure 1C is a cross-sectional view of the lateral locking module (LTM) in a closed configuration according to the present invention. Figure 1D shows detail A of Figure 1C. Figure 1E shows detail B of Figure 1C. Figure 2A is a simplified representation of the isometric view of the lateral locking module (LTM) according to the present invention in an early stage before locking. Figure 2B is a simplified representation of the side section of the lateral locking module (LTM) according to the present invention in an initial stage before locking. Figure 3A is a simplified representation of the isometric view of the lateral locking module (LTM) according to the present invention in a first locking stage. Figure 3B is a simplified representation of the simplified side section of the lateral locking module (LTM) according to the present invention in a first locking stage. Figure 4A is a simplified representation of the view of the lateral locking module (LTM) according to the present invention in a final locking stage. Figure 4B is a simplified representation of the simplified side section of the lateral locking module (LTM) according to the present invention in a final locking stage. Figure 5 is a representation of the Diverless Unified Support Tube (TSUDL) assembly including a set of multiple LTMs according to the present invention in its lower section. Figure 6 is an additional cross-sectional representation of the Diverless Unified Support Tube (TSUDL) with the Hang Off Adaptor (HOA) inside it locked in the lower section by the set of multiple LTMs according to the present invention. Figure 7 is a representation of the external fixed locking subassembly of the LTM according to the present invention. Figure 8 is a representation of the internal mobile actuation subassembly in the hydraulic actuation mode of the LTM according to the present invention. Figure 9 is a representation of the internal mobile actuation subassembly in the ROV actuation mode of the LTM according to the present invention. Figure 10 is a representation of the fixed hydraulic cylinder subassembly of the LTM according to the present invention. Figure 11 is an isometric representation of the grooved profile between the inner liner and the sliding sleeve of the LTM according to the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0007] Specific embodiments of the present disclosure are described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any actual implementation, as in any engineering or design project, several implementation-specific decisions must be made to achieve the specific objectives of the developers, such as compliance with system-related and business constraints, which may vary from one implementation to another. Furthermore, it should be appreciated that such a development effort may be complex and time-consuming, but would nevertheless be a routine design and manufacturing undertaking for those of ordinary skill having the benefit of this disclosure.

[0008] Figures 1A to 1E show an exemplary configuration of the Lateral Locking Module 100 (LTM) for rigid risers in its closed configuration according to the present invention. Figure 1A shows the side view, Figure 1B shows the rear view, Figure 1C shows the cross-sectional view, and Figures 1D and 1E show details A and B, respectively, marked in Figure 1C. The LTM 100 has three main subassemblies: the external fixed locking subassembly, the internal mobile drive subassembly, and the fixed hydraulic cylinder subassembly. In Figure 7, it can be seen the complete LTM in cross-section with identification of the components of the external fixed locking subassembly. Other components outside the external fixed locking subassembly are colored gray in this figure for easier viewing.

[0009] This subassembly, consisting of the locking ring 29, mounting plate 31, fixing screws 8, load ring sleeve 28, has the function of fixing the LTM 100 through the external surface in the Diverless Unified Support Tube (TSUDL) as illustrated in Figure 7. The TSUDL is a support for rigid and flexible risers described in patent application number BR 102021017344-0. The external fixed locking subassembly also provides a locking means for the segments illustrated in figures 2A to 4B identified as component number 4. Also seen in Figure 1A is the set of hydraulic connections 14a and 14b, which has the function of supplying the hydraulic fluid for the hydraulic actuation of the LTM 100 remotely. The hydraulic connection assembly 14a and 14b interfaces with the outer cylinder 32 through a check valve 12. An anti-rotation plate 10 is secured to the rear of the LTM 100 by fasteners, e.g., studs 5, and locking elements, e.g., nuts 18, as illustrated in Figures 1A and 1B. If it is necessary to actuate the LTM 100 mechanically, a ROV (Remotely Operated Vehicle) can remove the anti-rotation plate 10 and attach a torque wrench and turn the actuation screw 51 to lock or unlock the LTM 100.

[0010] Figures 1D and 1E show the locking elements, for example, screws 1, 2, which fix plate 3 to cage 11 and keep segments 4 radially retracted prior to the locking operation. Plate 3 is flexible and allows, however, segments 4 to be displaced radially outward during the locking operation due to the contact force with mandrel 20 when the latter is displaced longitudinally.

[0011] A subsea limit switch 27 indicates that the LTM is in the retracted position, which allows the riser pull in operation to occur safely.

[0012] The internal movable drive subassembly, illustrated in Figure 8, consists of actuating screw 51, mandrel 20, cage 11, segments 4, retaining nut 21, sliding sleeve 17, spring housing 24, spring housing cover 23, grooved spring discs 9 and 25, and piston 22. Other components outside the internal movable drive subassembly are grayed out in this figure for easy viewing.

[0013] This subassembly, through actuating screw 51, operates the movements of the internal components of the LTM, hydraulically or mechanically actuated, to perform the functions of approaching and locking the LTM, as well as unlocking and retracting it. In the hydraulic drive mode in the initial stage, called approach, the piston is displaced from the initial retracted position (Figures 2A and 2B) towards the HOA, on the right in this example (Figures 3A and 3C), jointly moving the actuating screw 51, mandrel 20, segments 4, retaining nut 21, sliding sleeve 17, spring housing 24, spring housing cover 23, grooved spring discs 9 and 25 and cage 11 until it meets the HOA.

[0014] In the second stage, locking, the cage is prevented from continuing its movement by contact with the HOA, however, the other components continue their movement to the right (Figures 4A and 4B), which forces the segments 4 to a radial movement due to the taper of the mandrel 20. In the locking stage, after the movement of the segments 4 eliminates the radial clearances, the compression of the segments between the load ring jacket 28 and the mandrel 20 begins. The reduced cone angle has the property of self-locking, that is, once locked, it is maintained in this position regardless of hydraulic pressure on the piston 22. The equilibrium condition for locking to occur is obtained when the coefficient of friction between the parts is greater than the tangent of the cone angle, according to the standard described in "BS 1660-1:1992 / ISO 296 - Machine Tapers: Specification for shanks and sockets with self-holding tapers (morse and metric 5%)". The lowest coefficient of friction that can theoretically be adopted is 0.1, which results in a maximum mandrel angle of 5.7° for self-locking. Preferably, the mandrel angle is equal to or greater than 1°, reaching up to 5.7°, as mentioned. Most preferably, the mandrel angle is equal to 1.867°.

[0015] In mechanical drive mode, piston 22 remains stationary, but actuating screw 51 is moved forward by the effect of rotation on its helical thread, as with any screw. The other components are driven in the same manner as previously described.

[0016] The grooved spring disc 25 has the function of preventing the movement of the piston 22 until a minimum actuation pressure greater than the hydrostatic pressure of the LTM control umbilical is reached. The purpose is to prevent unintentional movement of the piston 22 by hydrostatic pressure during the pull in activity, in which the LTM must remain retracted. The grooved spring disc 9 has the function of transmitting the movement of the actuating screw 51 and retaining nut 21 to the cage 11, mandrel 20 and segments 4 in the approach stage. After contact between cage 11 and the HOA is initiated during the LTM locking stage, the force of actuating screw 51 and retaining nut 21 deforms grooved spring disc 9, allowing mandrel 20 to be displaced into cage 11, in its turn compressing segments 4 against the load ring sleeve 28. The fixed hydraulic cylinder subassembly, illustrated in Figure 10, consists of outer sleeve 32, screws 7 securing the outer sleeve to the mounting plate, inner cover 19, outer cover 26, inner sleeve 16, and screws 6 securing the inner sleeve to the outer sleeve. Some of these elements are seen in detail in Figures 2A to 4B and 9. Other components outside the fixed hydraulic cylinder subassembly are grayed out in Figure 10 for easier visualization.

[0017] This subassembly serves as a chamber for containing the hydraulic fluid during LTM locking and unlocking. The internal surfaces serve to guide the piston in its movement and maintain sealing in the sliding areas with the aid of sealing rings. Connections 14a and 14b connect the hydraulic supply pipes to the internal cylinder chambers. Additionally, the grooved profile of the inner sleeve 16 illustrated in Figure 11 allows the movement of the moving components highlighted in Figure 8 when hydraulically actuated, while also enabling the independent mechanical actuation by ROV of the actuating screw 51 and other moving components highlighted in Figure 9 (with the remaining components grayed out in this figure for ease of visualization).

[0018] Figures 2A and 2B, respectively, illustrate a simplified isometric view and a simplified cross-sectional side view of the LTM at an early stage before its locking with the Hang- off Adaptor (HOA) of the riser. Only the essential elements of the LTM 100 are shown for clarity. The specialist will be able to include secondary connections and fasteners based on their prior knowledge and the description being disclosed, so such secondary elements will not be discussed here for the sake of brevity.

[0019] In the initial stage, the LTM 100 is at a distance n3 from the HOA, preferably at least 16 millimeters. The sliding sleeve 17 and the retaining nut 21 are spaced apart, keeping the LTM 100 in an open configuration where only the actuating screw 51 forms an interface between the two parts, front and rear, spaced apart. The piston 22 and an inner cylinder 16 are spaced apart by a distance n1, preferably 1 millimeter. The segments 4 are diametrically recessed from the cage 11 by a distance n2, preferably 0.04 millimeters. The retaining nut 21 and the rear of the cage 11 are spaced apart by a distance n4.

[0020] The LTM locking actuation sequence has two stages. The first stage is the approach stage, shown in Figures 3A and 3B, which respectively illustrate a simplified isometric view and a simplified side cutaway view of the LTM during the approach stage. The LTM hydraulic circuit is actuated remotely, for example, from the platform or from a surface station or vessel. The hydraulic fluid is preferably supplied through an umbilical lowered together with the LTM. Optionally, the umbilical can be carried by the ROV. The entry of hydraulic fluid through connection 14a of outer cylinder 32 (Figure 1A) imparts a movement in the forward direction (in this example, to the right) to piston 22, spring housing 24, spring 25, housing cover 23, sliding sleeve 17, actuating screw 51, and retaining nut 21. The grooved spring disc 9 transmits the movement of the retaining nut 21 to cage 11, segments 4, and mandrel 20 as illustrated in Figure 8 until the movement of cage 11 is stopped when it encounters a stop or obstacle, in this case, the HOA. At this moment, the distance n3 between cage 11 and the HOA becomes equal to 0 millimeters, that is, the front part of the LTM becomes solid with the HOA. As a result of the stroke of actuating screw 51, the distance n1 between piston 22 and an inner cylinder 16 increases, preferably to 17 millimeters. The distance n4 between the retaining nut 21 and the rear of the cage 11 remains unchanged.

[0021] The second stage is the locking stage itself, shown in Figures 4A and 4B, which respectively illustrate a simplified isometric view and a simplified side cross-sectional view of the LTM during the locking stage. It occurs when the cage 11 touches the HOA and the locking of the LTM 100 begins. Upon interruption of the movement of the cage 11, the grooved spring disc 9 is compressed radially, which allows the continuation of the movement of the mandrel 20 entering the stationary cage 11. The mandrel 20 is kept in motion by the piston 22 and the sliding sleeve 17 expands the locking means 4 radially, compressing the locking means 4 against the jacket of the load ring 28. Locking is completed when the mandrel 20 finishes the locking stroke with the pressure in the hydraulic line of the connection 14a of the external cylinder 32 reaching its maximum value. For example, and preferably, this maximum value is 5000 psi.

[0022] As previously mentioned, the LTM 100 can be operated hydraulically or, alternatively, mechanically using a ROV-operated torque wrench. Both operating modes have the two stages described above. In the case of mechanical operation, the ROV removes the anti-rotation plate 10, couples the torque wrench to the actuating screw 51, and rotates it until the locking described above is completed.

[0023] Mechanical operation may be required, for example, in the event of a hydraulic circuit failure.

[0024] Due to the mechanism consisting of the mandrel 22, expansion segments 4, and load ring 28, illustrated in Figure 7, the locking remains even after the hydraulic circuit has been depressurized, or, in the case of mechanical operation, after the torque wrench of the ROV has ceased operation.

[0025] The reverse operation, of unlocking, is performed by the disconnect line connected to the right connection 14b of the external cylinder 32 illustrated in Figure 1A or mechanically imparting a reverse torque by the ROV torque wrench. The entry of hydraulic fluid through the connection 14b of the external cylinder 32 (Figure 1A) imparts movement to the piston 22 in a retracting direction, that is, away from the HOA (in this example, to the left) together with spring housing 24, spring 25, housing cover 23, sliding sleeve 17, actuating screw 51 and retaining nut 21 and mandrel 20. Initially, the cage 11 and the segments 4 remain stationary, but, as the mandrel 20 moves away and makes radial space for the segments 4, the compressive force of the locking is reduced to zero. The continued retraction of the moving parts described above forces segments 4 and cage 11 to move in the retraction direction, thus completing the unlocking and retraction of the LTMs. Figures 5 and 6 show a set of LTMs according to the present invention already locked into the HOA of the TSUDL in an exemplary application.

[0026] Advantageously, the set of LTMs 100 supports the bending and shear loads of the rigid riser termination, mitigating fatigue and wear problems due to movement and shock within the support tube. As a result, the service life of the riser is extended and maintenance operations are less necessary, reducing operating costs.

[0027] The LTM is actuated remotely from the production unit in the final pull in stage or mechanically by ROV. Advantageously, this allows the rigid riser to be locked and unlocked without divers, eliminating risks to human health and making the process much faster and cheaper. While aspects of the present disclosure may be susceptible to several modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention should cover all modifications, equivalents, and alternatives that fall within the scope of the invention, as defined by the following appended claims.

Claims

1. LATERAL LOCKING MODULE (LTM) (100) FOR RIGID RISERS, characterized by comprising: ▪ a fixed external locking subassembly comprising: ▪ a locking ring (29), a mounting plate (31), set screws (8), a load ring sleeve (28), and segment locking means (4); ▪ an internal movable drive subassembly comprising: ▪ an actuating screw (51), mandrel (20), cage (11), retaining nut (21), sliding sleeve (17), spring housing (24), spring housing cover (23), grooved spring discs (9, 25), and a piston (22); and ▪ a fixed hydraulic cylinder subassembly comprising: ▪ an outer sleeve (32), mounting plate mounting screws (7), an inner cover (19), and an outer cover (26), ▪ wherein actuation of the actuating screw (5 1) moves the cage (11) in an axial direction away from the sliding sleeve (17), and wherein when the cage (11) is urged by the actuating screw (51) against a stop (HOA), the LTM (100) transitions to a locked configuration.

2. LATERAL LOCKING MODULE (LTM) (100), according to claim 1, characterized in that the actuating screw (51) is actuated by a hydraulic circuit.

3. LATERAL LOCKING MODULE (LTM) (100), according to claim 1 or 2, characterized by further comprising a detachably attached anti-rotation plate (10).

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