Vortex-induced vibration reduction system of multiple riser pipes

Abstract

To provide a vortex-induced vibration reduction system of multiple riser pipes capable of efficiently reducing the vortex-induced vibration occurring by a water flow situation when multiple riser tubes are hung in water from an on-water structure.SOLUTION: A vortex-induced vibration reduction system reduces the vortex-induced vibration (VIV) occurring by the water flow of multiple riser pipes 10 installed toward a water bottom 3 from an on-water structure 2 near a water surface 1. The system comprises the multiple riser pipes 10, riser pipe rotating means 20 to rotate the entire multiple riser pipes 10, and control means 30 to control the rotation of the riser pipe rotating means 20 depending on the vortex-induced vibration occurrence situation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vortex-induced vibration reduction system that reduces vortex-induced vibration caused by water flow in a plurality of riser pipes that are installed from an above-water structure near the water surface toward the bottom of the water. [Background technology]

[0002] For risers suspended from floating structures used for underwater drilling and the extraction of underwater resources, it is extremely important in terms of fatigue strength to reduce vortex-induced vibration (VIV), which is induced by vortices periodically generated in the wake of the pipe in the flow, causing self-excited vibration of the pipe. Conventional vortex-induced vibration reduction devices generally include strakes and fairings that are attached directly to the riser pipe. Strakes are made of multiple fin-shaped attachments attached to the riser pipe in a spiral pattern, which distribute the phase of vortex shedding positions along the longitudinal direction to suppress the occurrence of vortex-induced vibration. Fairings are made of multiple attachments with airfoil-shaped cross sections that are attached to the riser pipe to suppress vortex shedding and thereby suppress the occurrence of vortex-induced vibration. Furthermore, Patent Document 1 discloses a vortex-induced vibration suppression system for a riser array in which at least three structures are arranged in a fluid environment, at least two of which are provided with vortex-induced vibration suppression devices, and at least one of which is not provided with a vortex-induced vibration suppression device. Furthermore, Patent Document 2 discloses a vortex-induced vibration optimization system including a structure, a vortex-induced vibration monitoring system adapted to monitor the vortex-induced vibration level of the structure, a tensioner connected to the structure, and a controller adapted to calculate the tension of the structure in order to optimize the vortex-induced vibration value of the structure. Furthermore, Patent Document 3 discloses a columnar structure that is installed in a place where there is a fluid flow, such as in a tidal current or a river current, and that is provided with a vortex-induced vibration prevention means in which vortex-induced vibration prevention blades with a streamlined cross section are attached to the columnar structure so that they can rotate freely at a position where vortices are generated in the wake region of the columnar structure. Furthermore, Patent Document 4 discloses a slewing device for a ship used in oil drilling and production, etc., which has a shaft extending vertically through the ship, a turret disposed within the shaft so that the ship can freely rotate relative to the turret in response to wind and ocean currents, and the turret has a vertically extending passageway, the turret comprising an outer rotor, an intermediate pipe, and an inner pipe, the intermediate pipe and the inner pipe being disposed concentrically with the cylindrical rotor, the cylindrical rotor preferably extending along the entire length of the shaft, the intermediate pipe having a diameter such that a vertically extending annular gap is formed between the intermediate pipe and the rotor such that a number of risers can pass freely through the intermediate pipe, the inner pipe having an inner diameter such that a row of drill pipes can pass freely through the inner pipe, the intermediate pipe being connected to the rotor, and the inner pipe being connected to the intermediate pipe and / or the rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2012 / 0006053 [Patent Document 2] International Publication No. 2006 / 074309 [Patent Document 3] Japanese Patent Application Publication No. 62-090432 [Patent Document 4] Special Publication No. 2001-519276 Summary of the Invention [Problem to be solved by the invention]

[0004] Many risers used in the development of offshore oil and gas fields consist of multiple riser pipes, and many production risers for the development of offshore mineral resources, which have recently been attracting attention, are also proposed that consist of multiple Kaiser pipes. Therefore, when multiple riser pipes are installed, it is necessary to efficiently reduce vortex-induced vibration. Here, a vortex-induced vibration reduction device using a strake or a fairing requires a huge amount of time to attach or detach the strake or fairing every time the riser is deployed or retrieved, and is basically only compatible with a single pipe. Furthermore, the riser array vortex-induced vibration suppression system described in Patent Document 1 requires the trouble of installing the vortex-induced vibration suppression device on the riser pipe. Furthermore, the vortex-induced vibration optimization system described in Patent Document 2 is basically for the case where there is one structure. Furthermore, the columnar structure provided with the vortex-induced vibration prevention means described in Patent Document 3 requires that vortex-induced vibration prevention blades be attached to the columnar structure, and is basically only applicable to the case where there is one columnar structure. Furthermore, the swivel device described in Patent Document 4 does not attempt to reduce vortex-induced vibration.

[0005] Therefore, an object of the present invention is to provide a vortex-induced vibration reduction system for multiple riser pipes that efficiently reduces vortex-induced vibration that occurs due to water flow conditions when a riser pipe (multiple riser pipes) made up of multiple pipes is suspended underwater from an offshore structure. [Means for solving the problem]

[0006] The vortex-induced vibration reduction system for multiple riser pipes according to claim 1 is a vortex-induced vibration reduction system that reduces vortex-induced vibration (VIV) caused by water flow in multiple riser pipes that are installed from an above-water structure near the water surface toward the bottom of the water, and is characterized by comprising multiple riser pipes, a riser pipe rotation means that rotates the multiple riser pipes as a whole, and a control means that controls the rotation of the riser pipe rotation means depending on the occurrence status of vortex-induced vibration. According to the present invention as set forth in claim 1, by rotating the entirety of the multiple riser pipes depending on the occurrence status of vortex-induced vibration, it is possible to reduce vortex-induced vibration without attaching any additional components such as strakes to the riser pipes.

[0007] The present invention as set forth in claim 2 is characterized in that the control means controls the riser pipe rotating means so that the plurality of riser pipes reciprocate in the rotational direction. According to the present invention as set forth in claim 2, if the rotation direction of the entire plurality of riser pipes is only one way, the connection structure between the lower part of the plurality of riser pipes and the connecting pipe such as the transfer pipe becomes complicated. However, by controlling the riser pipes to move back and forth, the connection structure can be simplified.

[0008] The present invention as defined in claim 3 is characterized in that the floating structure is a floating facility intended for the excavation or production / storage of underwater resources. According to the present invention as set forth in claim 3, it is possible to reduce vortex-induced vibration of multiple riser pipes suspended from an above-water facility, thereby improving the service life of the multiple riser pipes and reducing the CAPEX (capital expenditures) and OPEX (operation and maintenance expenses) of the entire project.

[0009] The present invention as set forth in claim 4 is characterized in that the surface facility is a drilling ship, and the riser pipe rotating means is also served as a rotating mechanism for drilling provided on the drilling ship. According to the present invention as set forth in claim 4, a rotation mechanism such as a rotary table for drilling work, which is generally installed on drilling ships, can also be used as a riser pipe rotating means, so there is no need to provide a new riser pipe rotating means.

[0010] The present invention as set forth in claim 5 is characterized in that it comprises a flow direction and flow velocity measuring means for measuring the flow direction and flow velocity of the water current in the vicinity where a plurality of riser pipes are installed, and predicts the occurrence state of vortex induced vibration based on the state of the flow direction and flow velocity of the water current measured by the flow direction and flow velocity measuring means, and controls the riser pipe rotation means with the control means. According to the present invention as set forth in claim 5, the occurrence of vortex-induced vibration can be suppressed by rotating the entire plurality of riser pipes in accordance with predictions based on flow direction and flow velocity before a large amount of vortex-induced vibration occurs.

[0011] The present invention as set forth in claim 6 is characterized in that an ultrasonic Doppler multi-layer current meter (ADCP) is provided on an underwater structure as a flow direction and flow velocity measuring means to measure the flow direction and flow velocity of a water current. According to the present invention as set forth in claim 6, since ADCPs are installed as standard equipment on many marine structures and drilling ships involved in the development of offshore oil and gas fields in recent years, it is possible to measure current direction and velocity without increasing the number of devices and use the measured values ​​to reduce vortex-induced vibration.

[0012] The present invention as set forth in claim 7 is characterized in that the distribution of flow direction and flow velocity over the longitudinal direction of a plurality of riser pipes is measured by an ultrasonic Doppler multi-layer flow direction and velocity meter (ADCP). According to the present invention as set forth in claim 7, it is possible to more accurately predict the occurrence of vortex-induced vibration using different flow directions and flow velocities in the water depth direction, and to suppress vortex-induced vibration by rotating the entirety of multiple riser pipes based on the prediction results.

[0013] The present invention as set forth in claim 8 is characterized in that the control means predicts the occurrence of vortex-induced vibration based on the distribution of flow direction and flow velocity measured by an ultrasonic Doppler current profiler (ADCP) and controls the rotation of the riser pipe rotation means. According to the present invention as set forth in claim 8, the occurrence of vortex-induced vibration can be suppressed by rotating the entirety of multiple riser pipes before a large amount of vortex-induced vibration occurs, in accordance with predictions based on the flow direction and flow velocity measured by the ADCP.

[0014] The present invention as set forth in claim 9 is characterized in that the lower parts of the plurality of riser pipes are provided with flexible connecting pipes for connecting to structures on the bottom of the water. According to the present invention as set forth in claim 9, the flexible connecting pipe deforms in accordance with the rotation of the entire plurality of riser pipes, so that the rotation of the entire plurality of riser pipes does not affect the structures on the seabed.

[0015] The present invention as set forth in claim 10 is characterized in that the distance between the plurality of riser pipes is such that the other riser pipes can be located in the wake region of a vortex generated in one of the riser pipes by the water flow. According to the present invention as set forth in claim 10, the influence of a vortex generated in one of the riser pipes by a water flow can be suppressed, thereby reducing vortex-induced vibration generated across the plurality of riser pipes.

[0016] The present invention according to claim 11 is characterized in that the plurality of riser pipes comprises two or more and six or less riser pipes. According to the present invention as set forth in claim 11, by limiting the number of riser pipes to be rotated to a predetermined number or less, it is possible to efficiently suppress the occurrence of vortex-induced vibration. [Effects of the Invention]

[0017] According to the present invention, it is possible to efficiently reduce vortex-induced vibration, thereby preventing fatigue failure of multiple riser pipes and extending their lifespan. [Brief explanation of the drawings]

[0018] [Figure 1] Schematic diagram of a multiple riser vortex-induced vibration reduction system in accordance with an embodiment of the present invention. [Figure 2] Figure showing the results of the same numerical simulation DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the multiple riser vortex-induced vibration reduction system of the present invention will be described. Figure 1 is a schematic diagram of a multiple riser vortex-induced vibration reduction system. The vortex-induced vibration reduction system for multiple riser pipes comprises: multiple riser pipes (multiple riser pipes) 10 arranged from an underwater structure (offshore structure) 2 located near the water surface (sea surface) 1 toward the water bottom (seabed) 3; riser pipe rotation means 20 for rotating the multiple riser pipes 10; control means 30 for controlling the riser pipe rotation means 20; current direction and current velocity measurement means 40 mounted on the underwater structure 2 for measuring the direction and velocity of water currents (ocean currents) in the vicinity where the multiple riser pipes 10 are installed; and connecting pipes 50 connected to the lower parts of the multiple riser pipes 10. The floating structure 2 is provided with a riser assembly device (derrick) for suspending the multiple riser pipes 10 to near the bottom of the water 3. The riser assembly device is also used to assemble the multiple riser pipes 10 and to support the multiple riser pipes 10 installed underwater.

[0020] The multiple riser pipes 10 are constructed by integrating multiple long riser pipes suspended from the floating structure 2 with hard connecting materials such as joints. The multiple riser pipes 10 are used when there are two or more types of fluids to be transported, when the pipes have two or more uses, etc. For example, in oil or gas development, the multiple riser pipes 10 are used to separate a pipe that injects seawater into the seabed (oil reservoir) from a pipe that lifts the oil or gas to the surface structure 2. In mineral resource development, the multiple riser pipes 10 are used to separate a pipe that lifts ore and seawater to the surface structure 2 from a pipe that returns unnecessary seawater to the seabed.

[0021] From the results of model experiments and numerical simulations of multiple riser pipes 10, the inventors of the present invention have found that an anisotropic arrangement of multiple riser pipes 10 can suppress the generation of vortices in specific flow directions, thereby reducing vortex-induced vibration. Therefore, in the vortex-induced vibration reduction system of the present invention, the multiple riser pipes 10 are rotatable around a vertical axis, and the control means 30 controls the riser pipe rotation means 20 connected to the multiple riser pipes 10 in accordance with the occurrence status of vortex-induced vibration, so that the multiple riser pipes 10 rotate by a predetermined angle and change their horizontal orientation relative to the flow direction. In this way, by controlling the horizontal orientation of the multiple riser pipes 10 and changing it according to the occurrence state of vortex-induced vibration, it is possible to reduce vortex-induced vibration without installing additional equipment for reducing vortex-induced vibration, such as strakes. Therefore, compared to installing additional equipment for reducing vortex-induced vibration, the time required for deploying and retrieving the multiple riser pipes 10 can be significantly reduced, and the cost of procuring additional equipment for reducing vortex-induced vibration is also unnecessary. The occurrence state of vortex-induced vibration can be obtained by direct detection using a sensor or the like, or can be obtained by estimation according to the orientation of the multiple riser pipes 10 relative to the flow direction.

[0022] Figure 2 shows the results of a numerical simulation, showing the behavior of wake vortices in a uniform flow. Figure 2(a) shows the case of a single riser pipe, while Figures 2(b) and (c) show the case of a multiple riser pipe consisting of three pipes. The orientation of the riser pipe relative to the water flow is shown above each figure. As shown in Figure 2(a), when the riser pipe is a single pipe, a vortex is generated behind the pipe. The vortex generated does not change even if the single pipe is rotated by a certain angle. On the other hand, as shown in Figures 2(b) and (c), in the case of multiple riser pipes 10, the vortices generated behind the riser pipes 10 vary significantly depending on the orientation of the multiple riser pipes 10 relative to the flow direction. When the multiple riser pipes 10 are oriented so that they are parallel to the flow, as in Figure 2(c), vortices are generated behind the pipes. However, when the multiple riser pipes 10 are oriented so that they are in series with the flow, as in Figure 2(b), the flow field around the multiple riser pipes 10 resembles the flow field when an appendage with an airfoil cross-section is attached, and it can be seen that the generation of wake vortices is significantly suppressed. Furthermore, it was confirmed that when the multiple riser pipes 10 are oriented so that they are in series with the flow, as in Figure 2(b), the drag acting on the multiple riser pipes 10 can also be significantly reduced.

[0023] Since the riser pipes are fixed to each other with a hard connecting material, the positional relationship between the riser pipes remains unchanged even if the multiple riser pipes 10 rotate. The riser pipes are arranged so that the other riser pipes can be located in the wake region of a vortex generated in one of the riser pipes by the water flow, and the distance between the riser pipes is set to satisfy this arrangement. This makes it possible to suppress the influence of a vortex generated in one of the riser pipes by the water flow and reduce vortex-induced vibration generated in the multiple riser pipes 10.

[0024] In terms of the occurrence and effect of vortex-induced vibration, the multiple riser pipes 10 preferably consist of 2 to 6 riser pipes, more preferably 2 or 3. By limiting the number of the multiple riser pipes 10 to a predetermined number, the occurrence of vortex-induced vibration can be efficiently suppressed.

[0025] The riser pipe rotation means 20 used to rotate the multiple riser pipes 10 has, for example, a rotation mechanism such as a rotary table mounted on the floating structure 2, and a drive device such as a motor used to drive the rotation mechanism. The control means 30 identifies the flow direction acting on the multiple riser pipes 10 using a flow direction and flow velocity measurement means 40 mounted on the floating structure 2, and uses the rotation mechanism of the riser pipe rotation means 20 to orient the multiple riser pipes 10 in a direction that reduces vortex-induced vibration.

[0026] The control means 30 may control the riser pipe rotating means 20 so that the multiple riser pipes 10 reciprocate in a rotational direction, such as rotating the multiple riser pipes 10 clockwise at one time and counterclockwise at another time. By controlling the multiple riser pipes 10 so that they do not rotate in only one direction but reciprocate in the rotational direction, when a connecting pipe 50 connected to a structure such as a drilling unit operating on the bottom 3 is connected to the lower part of the multiple riser pipes 10, the connection structure with the connecting pipe 50 can be made relatively simple. The connecting pipe 50 is a transfer pipe for transferring, for example, minerals or fluids.

[0027] The connecting pipe 50 connected to the lower part of the multiple riser pipes 10 is preferably flexible. The flexible connecting pipe 50 deforms as the multiple riser pipes 10 rotate, so that the rotation of the multiple riser pipes 10 does not affect the structure 4 on the water bottom 3, even without using a universal joint or the like.

[0028] The floating structure 2 of this embodiment is, for example, a floating facility intended for the excavation or production / storage of underwater resources. In this case, it is possible to reduce vortex-induced vibration of the multiple riser pipes 10 suspended from the floating facility, thereby improving the service life of the multiple riser pipes 10 and reducing the CAPEX (capital expenditures) and OPEX (operation and maintenance expenses) of the entire project. Surface facilities for the purpose of drilling for underwater resources are, for example, facilities that conduct exploratory drilling on the seabed for oil development and scientific research, while surface facilities for the purpose of production and storage are, for example, facilities that extract crude oil from offshore oil fields and extract deep ocean water from the deep sea.

[0029] Furthermore, when the surface facility is a drilling vessel, a rotation mechanism for drilling provided on the drilling vessel can also serve as the riser pipe rotating means 20. This allows a rotation mechanism such as a rotary table for drilling work that is generally installed on drilling vessels to be used as the riser pipe rotating means 20, eliminating the need to provide a new riser pipe rotating means 20.

[0030] As the current direction and velocity measurement means 40 capable of measuring both current direction and velocity, an electromagnetic current direction and velocity meter or an ultrasonic phase difference current direction and velocity meter can be used, but it is preferable to use an acoustic Doppler current profiler (ADCP). ADCPs are installed as standard equipment on many of the marine structures and drilling ships involved in the development of offshore oil and gas fields in recent years, for example. Therefore, by using an ADCP as the current direction and velocity measurement means 40, it is possible to measure current direction and velocity without increasing the number of devices, and use this to reduce vortex-induced vibration.

[0031] It is also possible to predict the occurrence of vortex-induced vibration based on the distribution of the water flow direction and flow velocity measured by the ADCP, and to control the riser pipe rotation means 20 using the prediction results by the control means 30. In this case, the occurrence of vortex-induced vibration can be suppressed by rotating the multiple riser pipes 10 according to the prediction based on the flow direction and flow velocity measured by the ADCP before a large amount of vortex-induced vibration occurs.

[0032] Furthermore, the ADCP may be used to measure the distribution of current direction and current velocity along the length of the multiple riser pipes. As shown in Figure 1, the current direction and velocity of the water body where the multiple riser pipes 10 are installed vary depending on the depth, so the occurrence of vortex-induced vibration can be predicted more accurately from the distribution of current direction and velocity using the different current directions and current velocities along the water depth, and vortex-induced vibration can be suppressed by rotating the multiple riser pipes 10 based on the prediction results. In Figure 1, the direction of the straight arrows indicates the flow direction, and their lengths indicate the flow speed. [Industrial Applicability]

[0033] The present invention can be widely used in all systems that have risers made up of multiple pipes and are susceptible to the effects of vortex-induced vibration, such as production risers for offshore oil and gas field development, drilling risers for drillships, and production risers for offshore mineral resource development, which have been attracting attention in recent years.The present invention can also be applied to use in lakes and marshes as well as in the ocean. [Explanation of symbols]

[0034] 1 water surface 2 Floating structures 3 Underwater 4 Underwater structures 10 Multiple riser pipes (multiple riser pipes) 20 Riser pipe rotation means 30 Control Means 40 Flow direction / velocity measurement means 50 Connecting pipe

Claims

1. A vortex-induced vibration reduction system for reducing vortex-induced vibration (VIV) caused by water flow in a plurality of riser pipes that are installed from an above-water structure near the water surface toward the bottom of the water, comprising: a plurality of the riser pipes; riser pipe rotation means for rotating the plurality of riser pipes as a whole; and control means for controlling the rotation of the riser pipe rotation means in accordance with the occurrence status of the vortex-induced vibration.

2. 2. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, wherein the control means controls the riser pipe rotating means so that the multiple riser pipes reciprocate in a rotational direction.

3. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, wherein the floating structure is an floating facility intended for the excavation or production / storage of underwater resources.

4. 4. The vortex-induced vibration reduction system for multiple riser pipes according to claim 3, wherein the surface facility is a drilling vessel, and a rotation mechanism for drilling provided on the drilling vessel also serves as the riser pipe rotating means.

5. 2. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, further comprising: a flow direction and flow velocity measurement means for measuring the flow direction and flow velocity of the water current in the vicinity of where the multiple riser pipes are installed; a prediction of the occurrence state of the vortex-induced vibration based on the flow direction and flow velocity of the water current measured by the flow direction and flow velocity measurement means; and a control means for controlling the riser pipe rotation means.

6. 6. The vortex-induced vibration reduction system for multiple riser pipes according to claim 5, wherein an ultrasonic Doppler multi-layer current meter (ADCP) is provided on the above-water structure as the flow direction and flow velocity measurement means, and the flow direction and flow velocity of the water flow are measured.

7. 7. The vortex-induced vibration reduction system for multiple riser pipes according to claim 6, wherein the ultrasonic Doppler multi-layer current profiler (ADCP) measures the distribution of the flow direction and the flow velocity over the longitudinal direction of the multiple riser pipes.

8. 8. The vortex-induced vibration reduction system for multiple riser pipes according to claim 7, wherein the control means predicts a state in which the vortex-induced vibration occurs based on the state of the flow direction and the state of the flow velocity measured by the ultrasonic Doppler multi-layer flow direction velocimeter (ADCP), and controls the rotation of the riser pipe rotation means.

9. 2. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, further comprising flexible connecting pipes at the lower portions of the multiple riser pipes for connecting to the structure on the seabed.

10. 2. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, wherein the distance between the plurality of riser pipes is such that the other riser pipes can be located in a wake region of a vortex generated in one of the riser pipes by the water flow.

11. 2. The vortex-induced vibration reduction system for multiple riser pipes according to claim 1, wherein the plurality of riser pipes comprises two to six riser pipes.

Images