SYSTEM FOR SUBSEA PUMPING OR COMPRESSING

Abstract

System for subsea pumping or compressing, comprising: an ESP (electrical submersible pump), a flowline jumper, a connector part in either end of the flowline jumper, and an arrangement for lifting, the ESP has been arranged in the flowline jumper which has been orientated in substance horizontal, distinctive in that the system further comprises: a stiffening arrangement, ensuring a straight ESP shaft at ail times during lifting, installation and operation, and a load limiting arrangement for limiting or eliminating the load on structure and seabed supporting the system.

Claims

1. System for subsea pumping or compressing, comprising: an ESP (electrical submersible pump), a flowline jumper, a connector part in either end of the flowline jumper, and an arrangement for lifting, the ESP has been arranged in the flowline jumper which has been orientated in substance horizontal, characterised in that the system further comprises: a stiffening arrangement, ensuring a straight ESP shaft at all times during lifting, installation and operation, and a load limiting arrangement for limiting or eliminating the load on structure and seabed supporting the system.

2. System according to claim 1, wherein the load limiting arrangement comprises buoyancy elements in the form of syntactic foam based buoyancy elements having service life and total buoyancy in order to compensate for the added weight of the system compared to a traditional subsea jumper.

3. System according to claim 1, wherein the stiffening arrangement comprises a truss structure.

4. System according to claim 1, wherein the stiffening arrangement comprises a longitudinal rib-arrangement.

5. System according to claim 1, wherein the stiffening arrangement comprises at least one extendable support leg towards the sea-bottom at the jumper mid-section

6. System according to claim 1 or 2, wherein each connector or connector adapter comprises an isolation valve, to avoid leakage to the environment at installation, replacement or retrieval of the system.

7. System according to claim 1 or 2, comprising a separate by-pass pipe controlled by an electrically operated valve that closes when power is applied to the ESP.

8. System according to claim 1 or 2, comprising an intermediate landing structure that can be mounted at locations where the jumper containing the ESP needs to be at an angle compared to the initial jumper to allow enough space for installation.

9. System according to claim 1, 2 and 8, wherein the intermediate landing structure has been adapted for installation of more than one flowline jumper containing ESPs.

10. System according to claim 9 wherein the intermediate landing structure comprises manifolds and valves allowing routing of the flow.

11. System according to claim 10, wherein the intermediate landing structure comprises manifolds and valves allowing at least two ESPs to be run in parallel.

12. System according to claim 10, wherein the intermediate landing structure comprises manifolds and valves allowing at least two ESPs to be run in series.

13. System according to claim 10, wherein the intermediate landing structure comprises manifolds and valves for a by-pass pipe.

14. System according to claim 10, wherein the intermediate landing structure comprises remotely activated valves.

15. System according to claim 1, wherein it comprises a common structure for stiffening and load limiting.

Description

FIGURES

[0040] FIG. 1 gives a presentation of a typical flow-line jumper arrangement, not according to the invention.

[0041] Figures Nos. 2A, 2B, 3, 4, 5, 6, 7A-D, 8A-D and 9 illustrate embodiments of the system of the invention, or details thereof, as explained in detail below.

DETAILED DESCRIPTION

[0042] As illustration of background art, not according to the invention, FIG. 1 illustrates of a typical flow-line jumper arrangement (1) with vertical connector parts (2) in each end for connecting to a x-mas tree and with a manifold, respectively. Similar arrangement can also be made in a horizontal version. Horizontally made-up connectors will in such case be used instead of the vertical ones. Horizontal arrangements are typically used where trawling activity might be going on. The flowline will in such cases be trenched, located at or close to the seabed. A removable trawling protection mat or similar arrangement will typically be placed on top of the flow-line if it is not trenched.

[0043] FIG. 2A illustrates a preferred embodiment of the invention where there is enough space between the connection points to directly replace the existing jumper with the new jumper assembly (3). The new jumper version has the same connector parts (2), but it has a new mid-section (4) that contains the ESP (5) inside a generally horizontal section of the flow-line (6). FIG. 2B illustrates a variation of the embodiment as for FIG. 2A, wherein each connector part comprises a connector adaptor (7) at each end of the new jumper, between the connector part of original design towards the X-mas tree and manifold, respectively, and the mid-section. This adaptor comprises an isolation valve (8) and a new connector with new connector part (9). The initial connector part is permanently left in place with the isolation valve when the mid-section with new connector parts is retrieved. This allows for closing the flow-line ahead of pulling the jumper to avoid spillage to sea. This solves an important issue related to replacing an existing jumper with an ESP-Jumper as such isolation valves are typically not in place in the existing system. This arrangement also allows for selecting a new connector that is optimally suited for quick and reliable retrieval and re-installation and standardization of required tooling.

[0044] FIG. 3 illustrates another preferred embodiment of the invention. This version can be used in cases where there is not enough space between the connection points for direct replacement of the original jumper with a new ESP-jumper assembly (10). At least one intermediate landing structure (12) is in such case located between the original connection points. FIG. 3 is showing two such landing structures. Such structures are typically landed at the seabed on a mud-mat or similar foundations. They are having a simple manifold connecting the in and out-going flow. They can be arranged with isolation valves (8) and new connector parts (9) suitable for easy retrieval, re-landing and connecting the ESP-jumper (10). Suitable jumpers (11) are used in connecting the intermediate landing structures with the initial connection hubs. The jumpers 10 and 11 will typically be mounted at an angle to each other allowing more freedom to locate the equipment if the seabed space is limited in the area.

[0045] FIG. 4 illustrates an embodiment of the invention where the ESP-jumper (10) is equipped with a truss structure (13) to make the generally horizontal section of the jumper containing the ESP (6) stiff enough to avoid significant bending. Vertical connector parts (9) are mounted in each end. Wet-mate connector (14) for electric power feed to the ESP is mounted on the truss structure.

[0046] FIG. 5 illustrates an alternative embodiment of the invention where the ESP-jumper (10) is equipped with ribs (15) and buoyancy elements (16). Three such ribs are typically located 120 degrees apart to make the generally horizontal section of the jumper containing the ESP stiff enough to avoid significant bending. The ribs are typically covering the entire jumper pipe length and having a size that reduces bending to an acceptable level. Vertical connector parts (9) are mounted in each end. Wet-mate connector (14) for electric power feed to the ESP is mounted on one of the ribs. Buoyancy elements (16) are mounted between the ribs onto the ESP-pipe. The buoyancy elements are sized to compensate for the added weight by including the ESP and the large diameter pipe containing the pump. In this way the connection points see no significantly added weight compared to the initial loading.

[0047] Similar buoyancy elements can be mounted inside or attached to the truss structure shown in FIG. 4 for the same purpose as described here.

[0048] As a preferable embodiment, the load limiting of the system of the invention can be enhanced by adding more buoyancy, reducing the weight of the system to a value lower than the initial jumper load without an ESP, thereby increasing the structural integrity. This is particularly feasible for mature fields with overloaded support structure and fields with weak or unstable seabed. Additional weight required for efficient installation can preferably be a part of the lifting arrangement, and be retrieved after installation.

[0049] FIG. 6 illustrates an additional or alternative way of supporting jumpers containing an ESP to avoid sagging. The mid-section of the horizontal pipe comprises at least one supporting adjustable leg (21). The leg comprises a foundation resting on the seabed and can be adjusted to give proper support.

[0050] FIG. 7 illustrates four alternative arrangements of jumpers containing an ESP (5) landed onto two intermediate landing structures (12).

[0051] In FIG. 7A a single ESP-jumper is utilized. The isolation valve (8a) is set in open position during operation.

[0052] In FIG. 7B a single ESP-jumper is utilized in parallel with another pipe with no ESP. The pipe with no ESP can be utilized for by-pass if needed. If for example the ESP should be out of operation, the flow can be routed through this bypass pipe. The isolation valve (8a) for the pipe containing an ESP is set in closed position during bypass-operation. The bypass pipe can also allow for pigging through the system.

[0053] In FIG. 7C two ESP-jumpers are utilized in parallel for increased capacity. The isolation valves connected to the ESP-pipes are set in open position during operation.

[0054] In FIG. 7D two ESP-jumpers are connected in series for increased pressure boosting capacity. A third pipe, having no ESP, connecting the outlet of the first ESP with the inlet to the second ESP will allow this mode of operation. The isolation valves are set in open position during pumping.

[0055] FIG. 8 illustrates an alternative arrangement where the manifolds at the intermediate landing structures are re-arranged to allow for various operation modes by changing valve position. Three pipes (17a, 17b and 17c) are arranged in parallel. Pipe 17a and 17c contain ESPs and pipe 17b serve as by-pass line. Isolation valves 18a, 18b and 18c are located at the inlet of each of the pipes, while isolation valves 18d, 18e and 18f are located at the respective outlets. Routing valve 19 is located in the inlet cross-connecting header between pipe number one and two (17a and 17b), while valve 20 is located in the outlet cross-connecting header between the outlets of pipe two and three (17b and 17c). A setup with three ESPs in parallel can also be arranged (not shown). The valves are typically remotely controlled for efficient re-routing of the flow.

[0056] FIG. 8A illustrates a single ESP operation. A second ESP can be installed as back up. The by-pass line and the back-up ESP are closed off. Valves 18a, 18d and 20 are open. The other valves are closed.

[0057] FIG. 8B illustrates a by-pass operation with no ESPs in operation. The two ESPs are closed off. Valves 19, 18b, 18e and 20 are open. The others are closed.

[0058] FIG. 8C illustrates a parallel operation of two ESPs. The by-pass is closed off. Valves 18b and 18e are closed. The other valves are open.

[0059] FIG. 8D illustrates serial operation of two ESPs. The by-pass line is used to connect the two ESPs. Valves 19 and 20 are closed, all other valves are open.

[0060] FIG. 9 illustrates a pipe support frame (22) typically mounted in each end of the jumpers illustrated in FIGS. 4 and 5. The frame allows for temperature induced expansion/contraction in the direction of the pipe axis. The frame will however transfer torque and load in the vertical direction onto the connector hub. Side-load (in the horizontal direction) induced typically by any ocean current at the location, will also be transferred.

[0061] With the present invention, the prior art limitations are remedied by one or more of the following changes:

[0062] The weight of the jumper is different in air and submerged in water. The stiffening arrangement and a proper lifting arrangement to secure a straight pipe during lifting will be arranged so that the pipe containing the ESP will see minimal bending during lifting in air and in water, installation and in the landed, operational position. Long pumps, like the ESP type, shall preferably be operated with a straight shaft. The rotor-dynamic behaviour of this long shaft going through the motor, seal section and pump benefits from the present invention. Minimizing oscillations and vibrations will minimize the wear and tear on bearings and seals and ensure long service life. Such shaft straightness will be achieved by a stiffening arrangement on the ESP-pipe. A truss structure or fins mounted onto the pipe are two possible arrangements.

[0063] A spreader-bar and wires from this bar connected to lifting points distributed along the jumper allows for keeping the jumper straight also during lifting in air and going through the splash-zone during installation.

[0064] In order to avoid additional weight on the landing structures and vertical connectors beyond the initial loading of these connectors, buoyancy elements are included as a load limiting arrangement. Such buoyancy elements will compensate for the added weight introduced by the ESP and the larger pipe containing it. The buoyancy elements and stiffening devices can be combined either in a truss structure or with stiffening fins attached to the pipe and embedded in the buoyancy materials, or the same structure can be both stiffening and load limiting.

[0065] A subsea jumper arrangement that has a generally horizontal section containing an ESP will require a certain distance between the connector hubs. If such distance is sufficient, the ESP-jumper can directly replace the existing jumper. If the distance is too short, one or two intermediate landing structures can be installed and the ESP-jumper is installed between the structures. One or two flow-line jumpers will in such case have to be installed between the initial connection hubs and the intermediate landing structures. The jumpers are installed at an angle to each other in the horizontal plane to allow for flexible routing and enough space for the ESP pipe. In fields where horizontal connector systems are used, the arrangement can be adapted for such connectors. Trawling protection can be added both on the horizontal pipe section and also for the intermediate landing structures where needed.

[0066] Connectors exist in various make requiring relevant subsea tools for installation and retrieval. The ESP-jumper might need more frequent change-out, typically every 2-4 years, than the pipeline jumper due to required pump service. Installing a quick-connect connector type for the ESP-jumper is therefore preferable, for standardizing and availability of required tools and efficient operation.

[0067] Isolation of the in- and out-board pipeline ends is vital to contain hydrocarbons from leaking to the environment when the ESP-jumper is retrieved. If the ESP-jumper is landed directly onto the original hubs, a connector adaptor including such isolation valve is preferably used. Such adaptor will typically be a complete connector housing permanently left in place on the existing connection hub and terminated at the upper end with the standardized vertical connector hub. An isolation valve is included in the adaptor between the connectors. Such valve is typically operated by a Remote Operated Vehicle (ROV). If the ESP-jumper is landed onto one or more intermediate landing structures, a small manifold with isolations valves can be included.

[0068] Flow by-pass can be achieved by having a pipe arranged in parallel with the ESP-pipe and the flow path controlled by valves. The valves can be ROV operated or remotely controlled by the production control system. The valves can also be electrically operated by the electric power fed to the ESP so that it will be set in the desired position when the ESP is powered.

[0069] The embodiment where the ESP-jumper is arranged onto two intermediate landing structures can accommodate serial or parallel operation of ESPs. Three parallel pipes arranged with valves in each ends of the pipes onto the manifold mounted on the structures can direct flow in various ways. Two pipes will typically be equipped with ESPs while the third is empty. The empty pipe is used for by-pass.

[0070] For all these embodiments and variations thereof, means are provided to allow for hydrate inhibition. Injection ports are installed at suitable locations for supply of methanol or other inhibitors. This arrangement will also be used for flushing of the unit to remove hydrocarbons prior to retrieval. Supply and control of such injection is typically provided from the associated production system. Valves and connectors of the system are preferably designed to allow override by ROV in case of control failure.

[0071] Condition monitoring of the ESP (pressure, temperature and vibration signals) can be done in several ways: [0072] Signals modulated onto the power feed cable, as typically done for ESPs used in wells, can be applied if the data update frequency is not critical [0073] Signals can be routed through the production controls system [0074] Signals can be routed through a signal line or optical fiber in the ESP power umbilical.

[0075] As an example of the technical effect of the invention, a case study for a specific field in the Gulf of Mexico can be mentioned. For said field, an installed state of the art subsea pump system comprising 4 flowline jumpers with ESP for pressure boosting weights about 350 metric tons, including required substructure. A system of the invention, also comprising 4 flowline jumpers with ESP, providing identical pressure boosting, weighs about 60 metric tons, including required substructure. Accordingly, the weight reduction is about a factor 60/350, resulting in a weight of about 17% of the state of the art system, and it is reason to believe that also the cost reduction and reduced time for fabrication are accordingly. If comparison is made to traditional subsea pump systems, the technical effect is even more favorable.

[0076] For subsea fields with overloaded structure or unstable seabed or both, the system of the invention can be the only possible way of providing pressure boosting without building a completely new pressure boosting station for location on the seabed besides the existing structures.

[0077] The system of the invention may comprise any feature or step as here illustrated or described, in any operative combination, each such operative combination is an embodiment of the present invention.