WO2013021842A1

WO2013021842A1 - Gas lift system and gas lift method

Info

Publication number: WO2013021842A1
Application number: PCT/JP2012/069173
Authority: WO
Inventors: 拓樹中村; 雅樹川瀬; 章糸島
Original assignee: 三井海洋開発株式会社
Priority date: 2011-08-09
Filing date: 2012-07-27
Publication date: 2013-02-14
Also published as: JP2013036421A

Abstract

The upper section of a riser tube (11) in a gas lift system (10) is provided with a degassing device (14) for: creating a rotational flow in a fluid mixture rising inside the riser tube (11); causing gas and air bubbles to gather at the center of rotation due to the effect of centrifugal force; and discharging the gathered gas and air bubbles to the exterior of the riser tube (11) through a degassing tube (14c) having an opening located at the center of rotation. This degassing device (14) makes it possible to more evenly distribute the gas inside the riser tube (11) overall by degassing the centrifugally separated gas even in the shallow-water region of the riser tube (11). As a result, it is possible to provide a gas lift system (10) and gas lift method which can be efficiently used even in a deep-water region.

Description

Bubble lift system and bubble lift method

The present invention provides a bubble lift for lifting solid or liquid substances such as deep seabeds, lake bottoms, riverbeds, etc., or sand, sediments, minerals, etc. The present invention relates to a system and a bubble lift method.

Gas lift technology is widely used for crude oil production in order to efficiently lift heavy oil that is slightly lighter than seawater from undersea oil fields that have poor self-injection pressure. In this technology, by injecting a gas whose mass is relatively negligible into the liquid inside the riser pipe, the liquid column pressure in the pipe is lowered by the volume ratio, and at the lower end of the riser pipe, the riser pipe This is a technology that generates indentation force due to the pressure of seawater and oil reservoir pressure. It has been confirmed that a bubble lift (including air lift or gas lift) technology can be effectively used even in minerals having a large specific gravity by making a slurry finely crushed and mixed with seawater.

As an example of this, as described in Japanese Patent Application Laid-Open No. 2005-291171, for example, sediment such as sediment, sludge, and the like deposited and compressed at the bottom of a sea, lake, dam, or storage tank Air lift riser (riser pipe) for raising water and air inside for the purpose of an efficient device that can remove objects and has high pumping capacity, and provided at the bottom of the air lift riser, There has been proposed a bubble jet type air lift pump that includes a bubble jet generating device for jetting water in which bubbles are mixed.

In the case of slurries, earth and sand, sludge, etc. (hereinafter collectively referred to as slurries) whose specific gravity is considerably larger than the surrounding liquid (seawater or water), if a considerable amount of bubbles are not injected, The average specific gravity of the mixed fluid cannot be reduced below the surrounding liquid, and an upward flow cannot be generated in the riser pipe, so that it is not possible to generate a pushing force due to a pressure difference between the inside and outside of the lower end of the riser pipe. .

On the other hand, the bubbles injected into the riser pipe in the deep water region and the medium water depth region increase the volume of the bubble as the mixed fluid consisting of the bubbles and slurry rises to the shallow water depth region and the pressure decreases. Since the volume of the solid hardly increases, the volume ratio of the bubble in the mixed fluid increases at an accelerated rate. As a result, as the upper end of the riser pipe is approached, the flow velocity of the upward flow becomes too large, the ratio of the amount of the object to be lifted in the mixed fluid is relatively lowered, the pulling efficiency is deteriorated, or in the worst case The problem that the object to be lifted cannot be lifted at all occurs. This problem is due to the fact that the relationship between the volume of the bubbles and the water depth is approximately inversely proportional, and becomes more significant as the water depth where the object to be lifted exists is larger. It happens prominently when it comes to the area.

For example, when an object to be lifted is lifted from the sea floor 100 m by a bubble lift, the bubbles injected at the lower end of the riser pipe only have a volume 10 times higher at the upper end of the riser pipe. However, when the object to be lifted is lifted from the seabed at a depth of 5,000 m, the volume of bubbles injected at the lower end of the riser pipe is 500 times as high as the upper end of the riser pipe. Looking at this in more detail, the volume of bubbles injected at a water depth of 5,000 m increases only by 25% while it rises to a water depth of 4,000 m, but increases fivefold at a water depth of 1,000 m. The water depth is 50 times at 100 m, and further 500 times near the water surface.

For this reason, in a typical example, the bubble flow rate is set so that the flow velocity at the upper end of the riser pipe does not exceed, for example, 10 m / sec in consideration of erosion even when only seawater is inhaled. When trying to pull up a slurry heavier than seawater under fixed conditions, if the ratio of bubbles in the mixed fluid at the upper end of the riser pipe (hereinafter referred to as bubble ratio) is to be kept below 90%, Only slurries that are only a few percent heavier than seawater can be lifted.

Also, when the slurry is pulled up from the seabed at a depth of 1,000 m under the same conditions, the slurry can be lifted only up to about 20% heavier than seawater. For this reason, in order to pull up minerals with a high specific gravity, the proportion of seawater in the slurry must be maintained so that the specific gravity of the slurry is 1.2 or less. It is generally not easy to manage the mixing ratio in the deep sea.

In other words, in the prior art bubble lift, when the bubble injected below the riser pipe rises to near the upper end of the riser pipe, the volume increases approximately in inverse proportion to the water depth. There was a drawback in that bubbles could not be injected so as to pull up something higher than seawater or the like, and bubble lift was not realized or the efficiency was very bad.

Japanese Application No. 2005-291171

The present invention has been made in view of the above situation, and its purpose is to provide a degassing device for degassing the air bubbles that have been centrifuged even in the shallow water depth region in the middle of the riser pipe, An object of the present invention is to provide a bubble lift system and a bubble lift method that can evenly distribute bubbles and can be used efficiently even in a deep water region.

In other words, a bubble lift that pulls up an object such as a slurry with an average specific gravity larger than the surrounding seawater from the deep water area, and lowers the average liquid column pressure in the riser pipe. Even if it is injected into the riser pipe in the area or the middle water depth area, the shallow water depth area, for example, about 1/10 of the upper part of the riser pipe, that is, about 100 m above the water surface, that is, about 100 m above the water surface if the water depth is 1,000 m An object of the present invention is to provide a bubble lift system and a bubble lift method capable of avoiding an excessive bubble ratio such that the volume of bubbles exceeds, for example, 90% of the volume of the mixed fluid in a portion from the water surface to the vicinity of the water surface.

In addition, in order to make it possible to use a slurry containing a mixture of particles of various sizes, a slurry mixed with minerals crushed to a size of pebbles, etc. Even if the solid concentration in the slurry decreases and the specific gravity is about the same as that of seawater, the flow rate does not become a problem of erosion, and conversely, even if the specific gravity of the slurry approaches that of the solid alone, it can be stacked. There is no bubble lift system and a bubble lift method.

Further, in order to handle such slurries, the riser is equipped with rotating equipment, shut-off valves, pressure regulating valves, throttle valves, orifices, etc. that are likely to fail due to breakage, biting, and biting. An object of the present invention is to provide a bubble lift system and a bubble lift method that are not disposed in a slurry system of a pipe or a receiving device.

In order to achieve the above object, the bubble lift system of the present invention comprises a bottom of the riser pipe for raising the bottom of the water or a solid or liquid substance below the bottom of the water through the riser pipe to the vicinity of the water surface. Bubbles that inject gas, raise the gas in a bubble state, suck the object to be pulled up into the riser pipe at the lower end of the riser pipe by the effect of pressure reduction of the fluid column in the riser pipe by the bubble, and pull it up on the water surface In the lift system, in the middle of the vicinity of the upper end portion of the riser pipe, the mixed fluid in the riser pipe is rotated to collect bubbles and gas in the mixed fluid at the rotation center by the centrifugal force effect, and from the rotation center. A deaeration device for discharging bubbles and gas to the outside of the riser pipe is provided.

With this configuration, by providing this deaeration device at an appropriate position, for example, in the vicinity of a water depth of 200 m, the mixed fluid that rises with the bubbles inside the riser pipe is spirally formed at the spiral portion (volute portion). The degassing pipe (vent) is inserted into the rotation center by collecting the bubbles and gas at the rotation center by centrifugal effect that induces rotation and causes the slurry containing the object to be pulled up in the mixed fluid to be pressed against the outer wall by centrifugal force. The excess bubbles and gas are discharged from the tube) to the outside of the riser tube by a deaeration device, and the gas volume can be reduced at this depth. The mixed fluid after reducing the bubbles is mixed well again with the slurry by a fixed vane or the like provided in the pipe so that the fluid can be efficiently lifted even above it.

A plurality of the deaeration devices of the present invention may be installed at different water depths, and may be deaerated (vented) little by little. With this configuration, it is possible to equalize the ratio of the volume occupied by the bubbles from the deep water region to the shallow water region, thereby further equalizing the flow velocity of the fluid and maximizing the fluid pulling efficiency.

In the above bubble lift system, the deaeration device does not need to be dynamically controlled in accordance with the state of drawing in the amount of gas injected into the lower portion of the riser pipe, and only the surrounding water is used. One or more should be installed so that the flow rate of the mixed fluid is within the preset range even if the vacuum is drawn, and the specific gravity exceeds the specific gravity even if only the object to be pulled is sucked. Configure.

According to this configuration, in consideration of the lifting depth, the specific gravity of the object to be lifted, etc., one or more deaeration devices are set so as to be within a pressure range set in advance by a calculation simulation or the like, and the pressure range is set. The object to be lifted can be lifted efficiently simply by adjusting the deaeration amount so as to be inside.

Further, in the above-described bubble lift system, the deaeration device is configured to cause rotation by guiding the mixed fluid in the riser pipe spirally. According to this configuration, the swirl flow can be generated with a very simple configuration.

In the bubble lift system, in the deaeration device, bubbles or gas discharged to the outside of the riser pipe is guided to the water surface by a deaeration transfer pipe connected to the deaeration pipe and released to the atmosphere. Configured to do. According to this configuration, since the pressure at the time of opening becomes atmospheric pressure, the pressure in the deaeration transfer pipe is lowered, and deaeration in the deaeration device is facilitated.

In the above-described bubble lift system, in the deaeration apparatus, the bubbles or gas discharged to the outside of the riser pipe are guided to the compressor on the water surface again by a deaeration transfer pipe connected to the deaeration pipe. It compresses and it comprises so that it may send in the lower side of the said riser pipe | tube. With this configuration, the energy required for compression can be reduced.

Further, in the above-described bubble lift system, the compressor is configured by a multistage compressor, and a plurality of the degassing devices are installed at different water depths, and the degassing transfer pipes from the respective degassing devices are compressed by the multistage compression. Configure to lead to different stages of the machine. With this configuration, it is possible to equalize the ratio of the volume occupied by the bubbles from the deep water region to the shallow water region, thereby further equalizing the flow velocity of the fluid and maximizing the fluid pulling efficiency. In addition, the energy required for compression can be reduced.

In the above-described bubble lift system, the deaeration transfer pipe is configured to control the deaeration amount on the water surface by providing a pressure regulating valve, a throttle valve, an orifice, etc. on the water surface.

According to this, it is generally considered difficult to lift solid matter such as sand, sediment, minerals, etc. from deep seabed, lake bottom, riverbed, etc. Therefore, it is not necessary to control the mixing ratio between the solid matter and the seawater, and it is possible to cope with a situation in which the specific gravity of the slurry changes every moment.

Ideally, the flow rate of the mixed fluid at the upper end of the riser pipe is within the design maximum flow rate and only solids are drawn even if only seawater is drawn in while maintaining a certain amount of bubble injection. It is also desirable to have the ability to be pulled up without being stuck.

According to the present invention, since the amount of deaeration in each deaeration device can be controlled, the flow rate does not increase excessively even if a slurry lighter than the design specific gravity is drawn. For example, when pulling up solids whose specific gravity is more than twice that of seawater by bubble lift at a water depth of 5,000 m, even if the seawater concentration in the slurry becomes 100%, the solids concentration becomes 100%. However, continuous operation with the set amount of bubble injection fixed is practically possible.

In the bubble lift system, in the deaeration device, the deaeration pipe is provided with a pressure relief valve that operates due to a pressure difference between the inside and outside of the riser pipe, and the deaeration amount is controlled by the pressure relief valve. , Configured to regulate the pressure in the riser tube. According to this configuration, the deaeration pipe of the deaeration device is provided with a pressure relief valve that opens and closes at the same 5 atm as the pressure difference inside and outside the riser pipe. Even if injected from the part, the bubbles can be discharged until a pressure difference of 5 atm is reached at a certain depth of the deaeration device, as before, before the volume of the bubbles becomes excessive at the top of the riser tube.

In order to achieve the above object, the bubble lift method of the present invention lowers the riser pipe from the vicinity of the water surface or below the water bottom, and injects the gas in the form of bubbles below the riser pipe. Due to the effect of reducing the pressure of the fluid column in the riser pipe due to the bubbles, the object to be lifted collected near the lower end of the riser pipe is sucked at the lower end side of the riser pipe and provided at the upper end of the riser pipe. In the bubble lift method for pulling up the mixed fluid containing the object to be pulled up to the receiving device, the bubble or part of the gas in the mixed fluid is degassed by the deaeration device provided on the upper side of the riser pipe. To do.

According to this method, an increase in the volume ratio of bubbles or gas in the mixed fluid in the vicinity of the upper end of the riser pipe can be further suppressed. In addition, the flow rate is within the design range even if dynamic control according to the pull-in situation is not applied to the amount of injected air or only the seawater is pulled in (the specific gravity is minimized). Even if only the solid content having a large specific gravity is drawn in, it can be kept within the design upper limit specific gravity.

According to the bubble lift system and the bubble lift method of the present invention, by providing a deaeration device in the middle of the riser pipe, the place where the maximum bubble ratio is generated is not limited to the upper end portion of the riser pipe but also to a shallow water depth region. Since multiple locations can be set, the proportion of bubbles occupied by the entire riser pipe from the deep water region to the shallow water region can be equalized, so the bubble rate should be increased on average without increasing the maximum flow velocity. Can do.

As a result, the overall flow rate inside the riser tube, especially the flow rate at the upper end of the riser tube, can be greatly reduced, so the problem of erosion can be drastically reduced, and the riser tube itself and its connection from the upper end to downstream processes can be reduced. Elasticity that can absorb metal with lower hardness, use lighter materials such as plastics and elastomers, and corrosion-resistant materials, and absorb coatings, liner materials, vibration-proof materials, vibration-damping materials, and bending. It is possible to use materials and the like. As a result, the use of lightweight riser pipes can cope with greater depths of water, the cost reduction effect of using inexpensive corrosion-resistant coatings and liners, and the effect of avoiding longitudinal vibration resonance and vortex-excited vibration with the wave period by changing materials Can be played. In addition, a flexible riser or bellows using a thin metal plate on the inner surface can be used, and an expensive and complicated riser tensioner or telescopic joint can be eliminated.

This also equalizes the flow velocity in the riser pipe, so there are problems due to the pulsation of the flow in the riser pipe, and the two-phase flow mode of slurry and bubbles (bubble flow, slug flow, annular flow, spray flow, etc.) It is possible to solve the problem of transition and the problem of solid-liquid separation in the slurry due to stagnation, and to realize a long riser tube efficiently.

This makes it possible to lift the object to be lifted by the bubble lift system even at a significantly deeper water depth than in the case of the prior art, and it is possible to lift the object having a higher specific gravity. Further, there is an effect that the pressure loss approximately proportional to the square of the flow velocity can be reduced and efficient lifting can be achieved. For example, with a bubble lift at a water depth of 5,000 m, it is practically possible to pull up a fluid having a specific gravity more than twice that of seawater.

And, when the lifting operation in the deep water area is performed by the bubble lift system and the bubble lift method of the present invention, high-functional parts and heavy parts that require power and control, such as pumps in the deep sea part and intermediate water depth part. Since the specific gravity of the mixed fluid in the riser pipe is lowered below the specific gravity of the liquid such as seawater and water by bubbles, the combined force of the riser pipe's own weight and fluid weight, tidal force, etc. is supported. The design load required for the rig can be greatly reduced.

In addition, when the sea state is rough during the pulling operation, it is necessary to detach, but according to the bubble lift system and the bubble lift method of the present invention, the detachment can be performed simply by lifting the riser pipe just like the conventional drilling rig. It becomes possible to do. Also, in the unlikely event of an emergency, parts outside the hull will be separated and removed, and even if a situation occurs in which the separated objects cannot be recovered, the possibility of detaching expensive high-functional parts is excluded. Can be.

In addition, since the riser tube is relatively thin and has the same diameter from the lower end to the upper end, it can be lifted efficiently. Therefore, while using the conventional drill rig system and the drill rig system that handles the riser tube, Can raise in the area. Therefore, the development cost can be greatly reduced.

FIG. 1 is a diagram schematically showing a configuration of a bubble lift system according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the configuration of the deaeration device. FIG. 3 is a diagram schematically illustrating a configuration of a receiving device including a pressurized chamber, a run-up weir, and the like. FIG. 4 is a diagram showing the relationship between the set pressure of the pressurizing chamber and the maximum specific gravity of the slurry to be pulled up. FIG. 5 is a diagram showing the relationship between the maximum specific gravity of the slurry pulled up by the set pressure of the pressurizing chamber and the water depth.

Hereinafter, a bubble lift system and a bubble lift method according to embodiments of the present invention will be described. Here, an example will be described in which an ocean bottom resource is raised using a drill ship in the ocean, but the present invention is not limited to the ocean, and can be applied to a lake, a river, and the like.

The bubble lift system 10 according to the embodiment of the present invention is configured as shown in FIG. A drill ship 1 that floats on the sea surface (water surface) 2, a system that is used to lift the sea bottom (water bottom) 3 or resources under the sea bottom 3, a riser pipe 11, a collector 12, gas The feeding device 13, the deaeration device 14, and the receiving device 20 are provided.

The bubble lift system 10 passes through a riser pipe 11 through a riser pipe 11 with a bottom 3 such as a seabed, a lake bottom, or a riverbed, or a solid or liquid substance (a target to be lifted) such as sand, sediment, or mineral below the bottom 3. In order to pull up to the vicinity of the water surface 2, a gas is injected and raised at the lower part of the riser pipe 11, and the object to be lifted is surrounded at the lower end of the riser pipe 11 by the effect of reducing the pressure of the fluid column in the riser pipe 11. This is a system in which the water is sucked into the riser pipe 11 together with water and the object to be pulled up is pulled up on the water surface 2 together with water and gas.

This drillship 1 uses a drillship equipped with an automatic ship position retention system in order to lift deep seabed sediments. Further, the riser pipe 11 of the drill ship 1 is used as the riser pipe 11 of the bubble lift system 10. The riser pipe 11 of the drill ship 1 is usually used for recovering the drilling mud during excavation using a method using the drilling mud. Note that the drilling function of the drilling rig provided in the drill ship 1 need not be used.

The riser pipe 11 is constituted by connecting a number of short pipes having an inner diameter of 50 cm and a length of about 27 m with flanges, for example. It is preferable to use a material resistant to erosion in the shallow water depth region where the flow velocity of the riser pipe 11 is relatively high, and to use a lightweight material in the middle water depth region and the large water depth region. The riser tube 11 is provided with a collection device 12 at the lower end, a gas inlet device 13 on the lower side, and a deaeration device 14 on the upper side, respectively. The upper end side of the riser pipe 11 is connected to the pressurizing chamber 21 of the receiving device 20. In addition, an auxiliary pump, a pulverizer, or the like may be used at the lowermost end or the middle part of the riser pipe 11 if necessary. A collecting device 12 such as a strainer is provided at the lower end part of the riser pipe 11. Provide. Since this bubble lift system 10 requires a minimum amount of equipment, heavy objects such as a lower marine riser package (LMRP) and high-functional parts are not required, and the riser pipe 11 is lengthened by the weight. It is possible to cope with deeper water depth. Further, in order to obtain stability against tidal forces and the like, it is conceivable to reduce buoyancy bodies (not shown) that give buoyancy to the riser pipe 11 in deep water.

As a pipe for sending compressed air for bubble lift to the gas inlet device 13 provided at the lower part of the riser pipe 11, it is usually used outside the main pipe of the riser pipe 11 for an ejection prevention device. Since a narrow tube called a kill line or a choke line is arranged and held, a high-pressure thin tube arranged and held in the same manner as these is used. The gas inlet device 12 is composed of a special short tube with an air lift valve for injecting compressed air into the riser tube 11, and the short tube as the gas inlet device 13 has a deep water depth, Used for several short pipes used in deep water.

Also, as shown in FIG. 2, a special short pipe provided with a deaeration device 14 is used for several short pipes used in shallow water depths. The deaeration device 14 includes an outer wall 14a, a spiral pipe 14b, a deaeration pipe 14c, and a deaeration transfer pipe (vent exclusive pipe) 14d. A pressure relief valve may be provided in place of the deaeration transfer pipe (vent exclusive pipe) 14d. In FIG. 2, white circles indicate bubbles, and cross hatched portions indicate, for example, mixed slurry of seawater and an object (sand, crushed minerals, etc.), and single hatched portions are The seawater-only part is shown, and the white part is the gas part.

The outer wall 14a is formed with a diameter larger than that of the main pipe of the riser pipe 11, and includes a cylindrical portion, a lower tapered portion on the lower side thereof, and an upper tapered portion on the upper side of the cylindrical portion. The entire outer wall 14a accommodates the entire spiral pipe 14b and a part of the deaeration pipe 14c, and is formed to have a size capable of containing the swirling flow of the mixed fluid flowing in from the short pipe of the lower riser pipe 11. The spiral pipe 14b is a pipe whose lower end is connected to the main pipe of the lower riser pipe 11 and is spirally arranged along the inside of the lower taper portion of the outer wall 14a. There is an opening in the cylindrical part. The mixed fluid flowing out from the spiral pipe 14b is configured to form a swirling flow along the outer wall 14a. That is, a swirling flow is generated by guiding the mixed fluid in the riser pipe 11 in a spiral shape.

The deaeration pipe 14c is configured by a pipe having an opening at a central portion with respect to the cross section of the cylindrical portion of the outer wall 14a and passing through the outer wall 14a and going out. The deaeration pipe 14 c is connected to a deaeration transfer pipe (vent exclusive pipe) 14 d provided outside the main pipe of the riser pipe 11.

That is, the deaeration device 14 generates a swirling flow in the mixed fluid that rises inside the riser pipe 11 in the upper portion of the riser pipe 11, that is, in the middle of the vicinity of the upper end of the riser pipe 11. The air bubbles are collected by the rotation center, and the collected bubbles are discharged to the outside of the riser pipe 11 from a deaeration pipe 14c having an opening at the rotation center.

By this deaeration device 14, the mixed fluid that rises inside the riser pipe 11 together with the bubbles is spirally guided in the shell-shaped spiral pipe (volute) 14 b to cause rotation, and the object of pulling up slurry etc. by centrifugal force Due to the centrifugal effect of pressing the object against the outer wall 14a, the bubbles can be collected at the center of rotation, and excess bubbles can be discharged out of the deaeration device 14 from the deaeration tube 14c inserted into the center of rotation.

In this deaeration device 14, bubbles or gas discharged to the outside of the riser pipe 11 are guided to the water surface 2 by a deaeration transfer pipe 14 d connected to the deaeration pipe 14 c and released into the atmosphere under atmospheric pressure. Alternatively, the deaeration transfer pipe 14d connected to the deaeration pipe 14c may be led into the pressurization chamber 21 and released under pressure. In this case, the energy required for the compression is obtained by circulating the discharged gas to the compressor together with the gas separated in the pressurizing chamber 21 and reusing it as air lift bubbles without expanding the discharged gas to atmospheric pressure. Can be reduced.

Furthermore, a pressure regulating valve, a throttle valve, and an orifice may be provided on the water surface 2 so that the deaeration transfer pipe 14d can adjust the deaeration amount flowing into the pressurizing chamber 21 and the compressor. With this configuration, the deaeration amount can be adjusted on the water surface 2 as necessary.

Further, in order to inject compressed air into the lower side of the riser pipe 11, a compressor that compresses air is configured as a multistage compressor, and the air (gas) separated in the pressurizing chamber 21 is compressed to It is configured to be sent again to the lower side, and bubbles or gas discharged to the outside of the riser pipe 11 by the deaeration pipe 14c in the deaeration device 14 and the deaeration transfer pipe 11d connected to the deaeration pipe 11c are used for the multistage compressor. The gas from the pressurized chamber 21 is led to the high pressure stage. As a result, the energy required for compression can be further reduced by turning the discharged gas to the compressor with higher pressure and reusing it as bubbles for bubble lift.

By providing the pressurizing chamber 21 at the upper end of the riser pipe 11, a unique phenomenon that the pressure inside the riser pipe 11 becomes higher than the water pressure outside the pipe can be used. Due to the effect of the chamber 21, the pressure inside the riser pipe 11 is set in a shallow water depth region where the pressure outside the pipe is higher than the pressure outside the pipe, and bubbles or gas are introduced into the sea (underwater) outside the riser pipe 11 using the pressure difference between the inside and outside. May be discharged. In this case, the deaeration transfer pipe 14d can be dispensed with.

Further, the deaeration pipe 14c is provided with a pressure relief valve (not shown) that operates due to a pressure difference between the inside and outside of the riser pipe 11, and the pressure inside the riser pipe 11 is adjusted by controlling the deaeration amount by this pressure relief valve. To be configured. According to this configuration, the pressure in the riser pipe 11 can be adjusted with a very simple configuration.

Furthermore, a fixed vane or the like is provided inside the riser pipe 11 so that the mixed fluid after the bubbles are reduced by the degassing device 14 can be efficiently raised even above the portion where the bubbles are reduced, and the object to be lifted It is preferable that the air bubbles and the seawater are mixed well again.

This deaeration device 14 may be provided at a plurality of locations (two locations in FIG. 1) with different water depths so as to gradually deaerate (vent) at a plurality of stages. With this configuration, the volume ratio of bubbles in the mixed fluid that rises inside the riser pipe 11 can be substantially equalized from the deep water area to the shallow water area, and thus the flow velocity of the mixed fluid can be more equalized. Fluid pulling efficiency can be maximized.

With this configuration, for example, a deaeration device 14 is provided at an appropriate position, for example, in the vicinity of a water depth of 200 m, and the pressure relief in which the pressure difference between the inside and outside of the riser pipe 11 is opened and closed at the same 5 atmospheres as the initial in the deaeration pipe 14c. If a valve is provided, even if more bubbles are injected from the lower part of the riser pipe 11, the volume of the bubbles is the same as the original at a depth of 200 m before the volume of the bubbles becomes excessive at the top of the riser pipe 11. Until the pressure difference between the inside and outside reaches 5 atm, the bubbles in the deaeration device 14 can be discharged to the outside.

As shown in FIG. 3, on the drill ship 1 corresponding to the upper end portion of the riser pipe 11, a pressurizing chamber 21, multistage

upstream weirs

22A, 22B, 22C, a separation tank 23, a U seal liquid supply pump 24, U A receiving device (pickup object receiving system) 20 including a sealing liquid supply pipe 25, a U sealing liquid reservoir 26, U seals (air traps) 27A, 27B, and the like, and a compressor (not shown) that generates compressed air for bubble lift ) Etc., the main pipe of the riser pipe 11 is connected to the pressurizing chamber 21 of the receiving apparatus 20, and the blower side piping of the compressor for sending the compressed air to the gas inlet apparatus 12 is the main pipe of the riser pipe 11. It is connected to a high-pressure tubule placed outside the tube.

By providing a pressurization chamber 21 at the upper end of the riser pipe 11 and pressurizing the inside of the riser pipe 11, the ratio of the volume of bubbles in the mixed fluid rising in the riser pipe 11 in the shallow water depth region is It is configured to suppress the increase.

The pressurizing pressure of the pressurizing chamber 21 does not need to be dynamically controlled in accordance with the drawing state into the gas injection amount injected at the lower portion of the riser pipe 11, and only the surrounding water is sucked. The flow rate of the mixed fluid is within the preset range, and even if only the object to be pulled is sucked, the pressure within the preset pressure range is set so that the specific gravity exceeds the design upper limit specific gravity. Constitute. According to this configuration, the pressurization pressure of the pressurization chamber 21 is set within a pressure range set in advance by a calculation simulation or the like in consideration of the pulling depth, the specific gravity of the pulling target, and the like. Thus, the object to be lifted can be efficiently lifted simply by adjusting the pressurizing pressure of the pressurizing chamber 21.

Further, the pressure in the pressurizing chamber 21 is preferably adjusted to 1/50 or more and 1/3 or less, more preferably 1/50 or more and 1/10 or less of the water pressure at the lower end portion of the riser pipe 11. When this pressure is less than 1/50, the effect of suppressing the volume of bubbles by the pressurizing chamber 21 is reduced, and the merit for providing the pressurizing chamber 21 is lost. On the other hand, if this pressure is greater than 1/3, the pressure resistance of the pressurizing chamber 21 is increased, and the required capacity of the compressor is increased, but no further improvement in the pulling capacity can be expected. Further, by setting the upper limit to 1/10, the pressure resistance performance of the pressurizing chamber 21 can be lowered, the receiving device 20 as a whole can be made compact, and if necessary, by using a deaeration system together Sufficient pulling performance can be obtained.

Further, as shown in FIG. 3, the pressurized chamber 21 is formed in a cyclone shape so that the mixed fluid from the riser pipe 11 is introduced into the pressurized chamber 21 from the tangential direction, thereby generating a swirling flow. And the function as a separator which isolate | separates the slurry containing gas and the pulling-up target object can be given by the centrifugal separation effect using the flow velocity of this mixed fluid. Also in this case, the separated gas A is extracted from the top of the pressurizing chamber 21 and is rotated to a compressor while being pressurized, and is reused as compressed air for bubble lift without being expanded to atmospheric pressure. be able to. In FIG. 3, white circles indicate bubbles, and cross hatched portions indicate, for example, a slurry in which seawater and an object (sand, crushed minerals, etc.) are mixed, and a single hatched portion. Indicates only seawater, and the white part indicates the gas part.

Further, in order to keep the pressure of the pressurizing chamber 21 within the design range, the

upstream weirs

22A, 22B, and 22C including the pressure vessel 22a and the slurry pipe 22b accommodated in the pressure vessel 22a are provided downstream of the pressurization chamber 21. Are provided in a single stage or multiple stages (three stages in FIG. 3). The upstream

downstream weirs

22A, 22B, and 22C of the respective stages are configured to keep the pressure downstream of the slurry tube 22b within the design range by controlling the pressure in the gas phase portion of the pressure vessel 22a including the upper end of the slurry tube 22b. . Furthermore,

communication pipes

28A and 28B are provided for communicating the gas phase portion of the pressure vessel 22a of the

upstream weirs

22A, 22B and 22C and the upper portions of the U seals 27A and 27B, and pressure control of the gas phase portion of the pressure vessel 22a is provided. Is configured to be performed by

U seals

27A and 27B that are provided with a single stage or a plurality of stages (two stages in FIG. 3) and use the pressure of the liquid column.

The slurry pipes 22b of the

upstream weirs

22A, 22B, and 22C communicate with the lower part of the preceding pressurization chamber 21 and the pressure vessel 22b, and the slurry introduced from these parts into the slurry pipe 22b from the lower part to the inside. It guides and overflows into the pressure vessel 22b at the upper part. The amount of pressure reduction in each stage can be adjusted by the height of the slurry tube 22b and the specific gravity of the slurry. Further, since the pressure in the lower portion of the slurry tube 22b is the sum of the pressure in the gas phase portion of the pressure vessel 22a and the liquid pressure of the slurry in the slurry tube 22b, the pressure in the gas phase portion of the pressure vessel 22a can be adjusted. The internal pressure of the pressure chamber 21 or the pressure vessel 22b in the preceding stage can be adjusted and controlled.

That is, the operating pressure of each pressure vessel 22a having each

upstream weir

22A, 22B, 22C can be maintained by controlling the gas phase pressure in each pressure vessel 22a. The control of the gas phase pressure can be performed by a pressure regulating valve or the like provided in the gas phase, but the

multistage U-seal

27A, 27B that uses the pressure of the liquid column by aligning the number of stages with the

upstream weirs

22A, 22B, 22C. It can also be. According to the

multi-stage U-seal

27A, 27B, troubles such as a pressure regulating valve caused by mist-like sand, mud, etc. can be avoided.

In the configuration shown in FIG. 3, the upper part of the pressure vessel 22a of the first stage upstream dam 22A communicates with the upper part of the first stage U-seal 27A through the communication pipe 28A, and the second stage upstream dam. The upper part of the pressure vessel 22a of 22B communicates with the upper part of the second stage U-seal 27B via a communication pipe 28B, and the upper part of the pressure vessel 22a of the third stage upstream weir 22C is opened to the atmosphere by an open pipe 28C. It is open.

According to this configuration, the pressure P3 inside the pressure vessel 22a of the third stage upstream weir 22C is the atmospheric pressure Po, and the pressure inside the pressure vessel 22a of the second stage upstream weir 22B. P2 is the sum of the atmospheric pressure Po and the pressure Pb of the liquid column of the second stage U-seal 27B. Further, the pressure P1 inside the pressure vessel 22a of the first stage upstream weir 22A is the sum of the pressure P2 and the pressure Pa of the liquid column of the first stage U seal 27A. That is, P3 = Po, P2 = Po + Pb, and P1 = P2 + Pa = Po + Pa + Pb. Therefore, the pressures P1 and P2 in each pressure vessel 22a can be controlled by controlling the pressures Pa and Pb of the liquid columns of the U seals 27A and 27B.

The separation tank 23 is connected to the outlet of the last

upstream weir

22A, 22B, 22C, and the slurry containing the object to be lifted is temporarily stored, and the object to be lifted is settled. Let it separate from seawater. When the slurry-like lifting object itself is in the form of a slurry, the precipitate B is extracted from the lower side in consideration of the time for precipitation. The precipitate B accumulates below the separation tank 23 and is pushed out from the lower outlet by the pressure due to its own weight in the separation tank 23, but may be discharged by a slurry pump (not shown). Further, the liquid (seawater) C from which the precipitate B has been removed becomes a supernatant and is discharged from the upper outlet to the outside of the separation tank 23, and after performing necessary post-treatment such as removal of the mixture, it is returned to the ocean. . Further, a part of the liquid (seawater) C is discharged from the upper side of the separation tank 23 by the U-seal liquid supply pump 24 and extracted from the U-seal liquid supply pipe 25 to the liquid reservoir 26. This liquid is used for the liquid columns of the U seals 27A and 27B.

According to the above-described bubble lift system 10, the riser pipe 11 is lowered from above the sea surface 2 such as the drill ship 1 floating on the sea surface (water surface) 2 to the bottom of the seabed 3 or below the bottom of the seabed 3. A gas is injected into the gas supply device 13 provided in the form of bubbles to rise, and due to the fluid column pressure reduction effect in the riser tube 11 by this gas, the collector 12 provided at the lower end of the riser tube 11 The collected object to be pulled is sucked at the lower end side of the riser pipe 11, and when the mixed fluid containing the object to be pulled is pulled up to the receiving device 20 provided at the upper end of the riser pipe 11, A degassing device 14 is provided to degas bubbles or a part of the gas in the mixed fluid, and a riser pipe is provided by a pressurized chamber 21 provided at the upper end of the riser pipe 11. It is possible to take the bubble lift method of applying pressure to the inside of one of the upper end, it is possible to suppress the increase in the ratio of the volume of the bubble or gas in the fluid mixture in the vicinity of the upper end of the riser pipe 11.

Further, the object to be pulled up such as slurry accumulated in the lower portion of the pressurizing chamber 21 is pushed out by the pressure inside the pressurizing chamber 21 and moves up the

upstream weirs

22A, 22B, 22C. The slurry pipe 22b provided in the dedicated pressure vessel 22a is run up, and the slurry containing the object to be pulled up is moved up the slurry pipes 22b of the run-up

weirs

22A, 22B, and 22C. The pressure inside the pressure vessel 22a dedicated to the run-up weir is one step lower than the pressure inside the pressurizing chamber 21 so as to be substantially balanced with the pressure of the slurry after the pressure reduction. To be kept.

The slurry goes up the slurry pipes 22b of the run-up

weirs

22A, 22B, and 22C, then falls inside each pressure vessel 22a, and the slurry accumulated at the bottom of the pressure vessel 22a moves further downstream. It is pushed out to another pressure vessel 22a in the

weir

22B or 22C. By repeating this, the pressure by the slurry containing the object to be pulled is finally lowered to atmospheric pressure.

Next, a bubble lift method according to an embodiment of the present invention using the bubble lift system 10 will be described. In this bubble lift method, the riser pipe 11 is lowered from the vicinity of the water surface 2 to the bottom 3 or below the bottom 3, and the gas is injected into the lower side of the riser pipe 11 to rise, Due to the effect of reducing the pressure of the fluid column in the riser pipe 11 by the bubbles, the objects to be lifted collected near the lower end of the riser pipe 11 are sucked at the lower end side of the riser pipe 11 and the receiving device 20 provided at the upper end of the riser pipe 11 In this method, the mixed fluid containing the object to be pulled up is pulled up, and a part of bubbles or gas in the mixed fluid is degassed by the deaeration device 14 provided on the upper side of the riser pipe 11.

In this bubble lift method, pressure is applied to the inside of the upper end of the riser pipe 11 by the pressurizing chamber 21 provided at the upper end of the riser pipe 11.

According to the bubble lift system 10 and the bubble lift method configured as described above, in the process of pulling up the object to be lifted, a rotating device, a shut-off valve, and a pressure regulator that are highly likely to fail due to breakage, biting, biting, etc. There is no need to provide valves, throttle valves, orifices, etc. in the slurry system.

Figures 4 and 5 show the simulation results. FIG. 4 is a diagram showing the relationship between the set pressure of the pressurized chamber 21 and the maximum specific gravity of the mixed fluid to be pulled up. The horizontal axis represents the set pressure of the pressurized chamber 21, and the vertical axis represents the bubble lift at a water depth of 5,000 m. The specific gravity of the upper limit slurry at is shown. FIG. 5 is a diagram showing the relationship between the maximum specific gravity of the slurry pulled up by the set pressure of the pressurizing chamber 21 and the water depth, the horizontal axis is the water depth, and the vertical axis is the set pressure of the pressurizing chamber 21 of 20 atm. The specific gravity of the upper limit slurry in each case is shown.

In this calculation simulation, the pressure of the pressurizing chamber 21 and the amount of bubble injection are fixed in the bubble lift system 10 that pulls up the object from the water bottom 3. The bubble injection amount is set to an upper limit amount at which the mixed fluid flow velocity at the upper end of the riser pipe 11 does not exceed 10 m / second even when the water concentration in the slurry becomes 100%. If the solid concentration is increased and the specific gravity of the slurry is increased with the setting, the flow rate is decreased, while the bubble ratio is increased. It is assumed that the slurry specific gravity at which the bubble ratio at the upper end of the riser tube 11 reaches 90% is a practical upper limit of the slurry specific gravity raised by the bubble lift system 10.

FIG. 4 shows a change in performance when the pressure setting of the pressurizing chamber 21 is changed at a water depth of 5,000 m. When the present invention is not carried out, it corresponds to the case where the pressure of the pressurizing chamber 21 of the present invention is atmospheric pressure. In this case, it can be said that the slurry having a specific gravity higher than seawater is not pulled up. It can be seen that the slurry having a specific gravity of about 1.5 times that of seawater can be pulled up by setting the pressure of the pressurized chamber 21 to about 20 atmospheres. Furthermore, it can be seen that if the pressure in the pressurizing chamber 21 is set higher, a slurry having a specific gravity more than twice that of seawater can be pulled up, but the same effect can be obtained even if the pressure in the pressurizing chamber 21 remains at 20 atm. 14 can be obtained by providing only one stage (not shown).

FIG. 5 shows changes in performance when the bubble lift system 10 in which the pressure of the pressurizing chamber 21 is 20 atm is used at various water depths. At a water depth of 1,000 m, it is possible to pull up slurry having a specific gravity about three times that of seawater. The deeper the water depth, the lower the specific gravity of the upper limit. It shows that the slurry of the degree can be pulled up.

According to the bubble lift system 10 and the bubble lift method of the invention having the above-described configuration, by providing the pressurization chamber 21 at the upper end portion of the riser pipe 11, in the conventional technology, in a large water depth region, for example, a water depth of 5,000 m. In the air bubble lift, since the volume ratio of the air bubbles is 500 times that of the lower end portion at the upper end portion of the riser tube 11, it can be lifted up to a slurry that is only a few percent heavier than seawater. Even in such a case, an increase in the volume ratio occupied by bubbles at the upper end of the riser tube 11 can be suppressed to a practical tens of times or less.

This makes it possible to lift the object to be lifted by the bubble lift system 10 even at a significantly deeper depth than in the case of the prior art, and to lift the object having a higher specific gravity. Further, there is an effect that the pressure loss approximately proportional to the square of the flow velocity can be reduced and efficient lifting can be achieved. For example, with a bubble lift at a water depth of 5,000 m, it is practically possible to pull up a slurry having a specific gravity more than twice that of seawater.

Furthermore, by providing the deaeration device 14 in the middle of the riser pipe 11, a place where the maximum bubble ratio is generated can be set not only at the upper end of the riser pipe 11 but also at a shallow water depth region. Since the ratio of the volume occupied by bubbles in the entire riser pipe 11 from the region to the shallow water region can be equalized, the ratio of bubbles can be increased on average without increasing the maximum flow velocity.

As a result, the flow rate of the entire riser pipe 11, particularly the flow speed at the upper end of the riser pipe 11, can be greatly suppressed, so that the problem of erosion can be drastically reduced. Use a metal with lower hardness, a light weight material such as plastic or elastomer, or a corrosion-resistant material, or a coating, liner material, vibration-proof material, vibration-damping material, or bending. It is possible to use an elastic material or the like that can absorb water.

As a result, the use of lightweight riser pipes can cope with greater depths of water, the cost reduction effect of using inexpensive corrosion-resistant coatings and liners, and the effect of avoiding longitudinal vibration resonance and vortex-excited vibration with the wave period by changing materials Can be played. In addition, a flexible riser or bellows using a thin metal plate on the inner surface can be used, and an expensive and complicated riser tensioner or telescopic joint can be eliminated. *

Then, when the lifting operation in the deep water area is performed by the bubble lift system 10 and the bubble lift method configured as described above, high-functional parts that require power and control, such as pumps in the deep sea part and the intermediate water part, Heavy components can be made unnecessary, and the specific gravity of the mixed fluid in the riser pipe 11 is reduced to below the specific gravity of the liquid such as the surrounding seawater and water by bubbles, so that the own weight of the riser pipe 11 and the fluid weight, tidal force The design load required for the rig that supports the resultant force can be greatly reduced.

In addition, when the sea state is rough during the pulling operation, separation is necessary. However, according to the bubble lift system 10 and the bubble lift method configured as described above, the riser pipe 11 is simply lifted in the same manner as the conventional drilling rig. It becomes possible to leave. Also, in the unlikely event of an emergency, parts outside the hull will be separated and removed, and even if a situation occurs in which the separated objects cannot be recovered, the possibility of detaching expensive high-functional parts is excluded. Can be.

Furthermore, the riser pipe 11 that is relatively thin and has the same diameter from the lower end to the upper end can be efficiently lifted, so that the riser pipe 11 of the conventional drilling ship and the drill rig system that handles the riser pipe 11 are used as they are. Can be lifted in deep water. Therefore, the development cost can be greatly reduced.

According to the bubble lift system and the bubble lift method of the present invention, a swirl flow is generated in the mixed fluid that rises inside the riser tube in the upper portion of the riser tube, and the bubbles and the gas are rotated about the center of rotation by the centrifugal force effect. In addition to collecting the collected bubbles and gas, a degassing device that discharges the collected bubbles and gas from the degassing tube with an opening at the center of rotation to the outside of the riser tube can be used at the upper end of the riser tube even in a bubble lift in a deep water area. Since the increase in the volume ratio occupied by bubbles can be suppressed to a practical tens of times or less, collection of submarine resources such as submarine hydrothermal deposits, manganese nodules, methane gas hydrate, rare earths, rare metals, cobalt rich crusts, diamonds, Underground at the bottom of the sea, lake, river, and below, such as dredging for sand and gravel collection, offshore structure installation work, etc. Solids from, can be utilized in all industrial raising liquid, a slurry.

1 Drillship 2 Sea surface (water surface)
3 Seabed (Waterbed)
DESCRIPTION OF SYMBOLS 10 Bubble lift system 11 Riser pipe 12 Collection apparatus 13 Gas supply apparatus 14 Deaeration apparatus (vent system)
14a Outer wall 14b Spiral shape part (volute part)
14c Deaeration pipe 14d Deaeration transfer pipe (vent exclusive pipe)
20 Receiving device 21 Pressurization chamber (type that has gas / slurry separation function)
22A, 22B, 22C Upstream weir

22a Pressure vessel

22b Slurry pipe 23 Separation tank 24 U seal liquid supply pump 25 U seal liquid supply pipe 26 U

seal liquid reservoir

27A, 27B U seal (air trap)
28A, 28B Communication pipe A Gas (bubbles and gas)
B Solid content C Liquid (seawater)

Claims

Injecting a gas at the lower part of the riser pipe to raise the bottom of the water or a solid or liquid substance below the bottom through the riser pipe to the vicinity of the water surface, raising the gas in a bubble state, In the bubble lift system in which the object to be lifted is sucked into the riser pipe at the lower end of the riser pipe by the effect of reducing the pressure of the fluid column in the riser pipe due to the bubbles, and lifted to the water surface.
In the upper part of the riser tube, a swirling flow is generated in the mixed fluid rising inside the riser tube, and bubbles and gas are collected at the rotation center by the centrifugal force effect, and the collected bubbles and gas are opened at the rotation center. A bubble lift system characterized in that a deaeration device is provided for discharging the deaeration pipe provided with a portion to the outside of the riser pipe.
The deaerator does not need to be dynamically controlled in accordance with the state of drawing into the gas injection amount injected at the lower part of the riser pipe, and the flow rate of the mixed fluid can be obtained even if only the surrounding water is sucked. 1 or 2 is installed so that it has a design upper limit specific gravity that is within a preset range and exceeds the specific gravity even if only the object to be pulled is sucked. Bubble lift system.
The bubble lift system according to claim 1 or 2, wherein in the deaeration device, a swirling flow is generated by guiding the mixed fluid in the riser pipe in a spiral shape.
2. The degassing apparatus according to claim 1, wherein bubbles or gas discharged to the outside of the riser pipe is led to the water surface by a degassing transfer pipe connected to the degassing pipe and released to the atmosphere. The bubble lift system according to any one of items 1 to 3.
In the deaeration device, bubbles or gas discharged to the outside of the riser pipe are led to a compressor on the water surface by a deaeration transfer pipe connected to the deaeration pipe and compressed again to be below the riser pipe The bubble lift system according to any one of claims 1 to 3, wherein the bubble lift system is configured so as to be fed into the air.
The compressor is composed of a multistage compressor, a plurality of the deaeration devices are installed at different water depths, and the deaeration transfer pipes from the respective deaeration devices are led to different stages of the multistage compressor. The bubble lift system according to claim 5.
In the deaeration device, a deaeration amount adjustment formed by a pressure relief valve, a pressure control valve, a throttle valve, or an orifice that operates on the deaeration pipe or the deaeration transfer pipe by a pressure difference between the inside and outside of the riser pipe The bubble lift system according to any one of claims 1 to 6, wherein a device is provided, and the pressure in the riser pipe is adjusted by controlling a deaeration amount by the deaeration amount adjusting device.
From the vicinity of the water surface, the riser pipe is lowered to the bottom of the water or below the bottom of the water, and a gas is injected into the bottom of the riser pipe to raise the pressure, and the pressure of the fluid column in the riser pipe is reduced by the bubbles. A bubble lift method for sucking up a lifted object collected near the lower end of the riser pipe on the lower end side of the riser pipe and pulling up a mixed fluid containing the lifted object in a receiving device provided at the upper end of the riser pipe. And a deaeration device provided on the upper side of the riser tube to degas bubbles or a part of the gas in the mixed fluid.