JP2006307446A - Excavating conduit disconnecting method, excavating conduit disconnecting apparatus, and seabed excavating facilities using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excavating conduit disconnecting method according to which the vertical vibration of an excavation conduit is easily and effectively reduced when a riser pipe is disconnected, and to provide an excavating conduit disconnecting apparatus and seabed excavating facilities using the same. <P>SOLUTION: The excavating conduit disconnecting apparatus is formed of: the excavating conduit 7 of a double pipe structure having a drill pipe 3 into which muddy water MW having a specific gravity larger than that of sea water SW is supplied, and the riser pipe 6 arranged outside the drill pipe 3, and connecting between an excavating ship (floating body) floating on the sea, and an excavation port formed in the seabed; a separating device for separating the excavating conduit 7 and the excavation port from each other; a central valve 32 arranged at the longitudinal center of the drill pipe 3, for restricting flowage of fluid; and a sea water supply device for supplying the sea water SW to the drill pipe 3 at a location immediately below the central valve 32. According to the excavating conduit disconnecting method, the excavating conduit 7 is separated from the excavation port, and before and after the separation, the muddy water MW in the drill pipe 3 is replaced by the sea water SW except for the muddy water MW remaining at the longitudinal center of the drill pipe 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an excavation pipe separating method, excavation pipe separating apparatus, and a submarine excavation facility using the excavation pipe separating method used for submarine excavation for geological surveys, resource surveys, resource collection, and the like on the sea floor.

  There is a riser drilling method as a drilling method of the seabed. In the riser excavation method, first, a drill pipe provided with a drilling blade at the tip is suspended in the sea from a floating body such as a drilling ship floating on the sea, and the seabed is excavated to a predetermined depth by this drill pipe. Next, a drilling device is provided at the drilling port to contain a fluid such as gas that has entered from the formation into the drilling port, and a riser pipe is provided around the drill pipe so that the drill pipe and the floating body extend from the spraying device to the floating body. A double pipe structure consisting of a riser pipe is formed.

After that, by supplying muddy water with higher specific gravity and higher viscosity than seawater into the drill pipe, a water pressure exceeding the surrounding formation pressure is applied to the tip of the drill pipe, and into the drilling hole of gas or oil contained in the formation Drilling with a drill pipe is performed in a state in which the intrusion is prevented.
Here, the muddy water also acts as a lubricant and coolant for the drilling blade, thereby preventing or reducing wear of the drilling blade. In addition, since the muddy water is supplied to the tip of the drill pipe in this way, the drilling waste generated at the tip of the drill pipe is pushed away by the muddy water and quickly removed, so that the drilling by the drill pipe is performed smoothly.

  Muddy water used for riser drilling is not just muddy water, but by adding various additives to seawater containing drilling debris, it has a specific gravity, and the drilled debris that is taken in does not separate and settle Thus, it has a predetermined viscosity and is very expensive. For this reason, the muddy water supplied to the tip of the drill pipe is collected in the floating body through a space (annular) formed between the drill pipe and the riser pipe, and then reused as muddy water.

In the riser excavation method, as described above, since the floating body and the excavation port are connected by the excavation pipeline including the drill pipe and the riser pipe, the excavation pipe is moved when the floating body is largely displaced from the position directly above the excavation port. An excessive tensile force is applied to the road. For this reason, normally, the position of the floating body is grasped by a position information system using a satellite, and the position of the floating body is controlled so that the floating body is always directly above the excavation port.
However, it is difficult to stay in place if the location information system becomes unusable due to a location information system failure or a floating power supply facility failure, or if the floating power facility fails or is washed away by the ocean current. In this case, the excavation pipeline is immediately disconnected from the excavation port in order to avoid damage to the excavation pipeline.

Also, if the sea surface is rough due to typhoons, etc., the amount of vertical displacement of the floating body will increase and load will be applied to the excavation pipeline, so if the sea surface is predicted to be rough, the drilling pipe will be in advance before the sea surface is rough. The road is cut off.
And even when it becomes impossible to prevent the gas or oil in the formation from entering the excavation port, the excavation pipeline is immediately cut off in order to protect the excavation equipment.

Here, the riser pipe constituting the excavation pipeline has a diameter of about 0.5 m to 1 m, but its total length reaches 2500 m, so that it tends to buckle when subjected to a compressive force. Therefore, the riser tube is pulled upward by a riser tensioner provided on the floating body so that a compressive force does not act, and is always in a stretched state. For example, when the total length of the riser tube is 2500 m, the riser tube is stretched by about 3 m (this elongation is due to elastic deformation).
For this reason, when the excavation pipeline is disconnected from the excavation port, the excavation pipeline is pulled up and down by the tensile force of the riser tensioner and the restoring force of the riser pipe. Vibrate.
When vertical vibrations occur in the excavation pipeline in this way, if the vibration is large, the upper end of the excavation pipeline pushes up the equipment on the floating body, or the lower end of the excavation pipeline is the anti-blowing device And may collide with the seabed.

As a technique for suppressing such vibration of the excavation pipeline, for example, an anti-recoil control device for a riser tensioner described in Patent Document 1 described below is known.
This anti-recoil control device for riser tensioner is based on the tension of the riser tensioner, the relative position of the riser top relative to the hull (floating body), and information on the vertical movement of the hull, and the relative speed between the upper end of the riser pipe and the hull. The tensioner tensioner tension and the riser tube disconnection timing are controlled so as to be close to zero.

Japanese Patent Laid-Open No. 10-311191

  However, as described in Patent Document 1, in order to obtain an appropriate control condition of the tension of the riser tensioner and an appropriate disconnection timing of the riser pipe based on the actual behavior of the hull and the riser pipe, a complicated calculation is performed. There is a need. For this reason, for example, when the sea surface is rough and the vertical movement of the floating body becomes irregular, the calculation becomes more complicated under complicated conditions, making it difficult to accurately predict appropriate control conditions. In some cases, sufficient effects could not be obtained.

  The present invention has been made in view of such circumstances, and excavation pipeline separation that can easily and effectively reduce the vertical vibration of the excavation pipeline when the excavation pipeline is separated. It is an object of the present invention to provide a method, an excavation pipeline disconnecting device, and an undersea excavation facility using the method.

In order to solve the above problems, the present invention provides the following means.
That is, the present invention includes a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body that is provided outside the drill pipe and floats on the sea, and a riser pipe that connects a drilling port formed on the sea floor. Provided is a method for separating a pipe for excavation in which a double pipe-structured excavation pipe is separated from the excavation port, and the mud water in the upper region of the drill pipe is replaced with the sea water before and after this.

In this excavation pipeline separating method, when the excavation pipeline and the excavation port are separated, the lower region of the excavation pipeline is filled with muddy water and the upper region is filled with seawater.
Since the specific gravity of the muddy water is larger than the specific gravity of seawater, when the fluid in the excavation pipeline is included, the mass of the lower region of the excavation pipeline in the above state is larger than the mass of the upper region.

The excavation pipeline in this state is approximately a first spring with one end fixed, a small first truck connected to the other end of the first spring, and the first carriage. On the other hand, the large mass second carriage connected via the second spring can be replaced with a first spring / mass model having a configuration arranged in a straight line on a friction-free horizontal plane.
In this first spring-mass model, the mass of the first carriage is the mass of the upper area of the excavation pipeline including the internal seawater, and the mass of the second carriage is for excavation including the internal mud. The mass of the lower region of the pipeline. The spring constant of the first spring is the spring constant of the upper region of the excavation pipeline, and the spring constant of the second spring is the spring constant of the lower region of the excavation pipeline. The spring constants of the first and second springs can be regarded as approximately the same.

In the first spring / mass model, the second carriage is separated from the first carriage by a predetermined amount from the state in which the first and second springs are in the natural length (that is, tension is applied to the excavation pipeline). When the second carriage is released from the same state, and each carriage is vibrated, the masses of the first carriage and the second carriage are equal in the first spring / mass model. Or, the amplitude of the first carriage is smaller than when the mass of the first carriage is larger than the mass of the second carriage.
This can be easily confirmed by numerically analyzing the behavior of the first spring / mass model based on the equation of motion or by actually conducting an experiment.
If this is applied to the actual excavation pipeline, when mud is located only in the lower region of the excavation pipeline, the excavation pipeline is separated from the excavation port as described above. It can be seen that the amplitude of the upper end of the excavation pipeline is smaller than that of the conventional one even when vertical vibrations occur in the pipeline. Thereby, after the excavation pipeline is cut off, the floating body on the sea is hardly pushed up by the upper end of the excavation pipeline.

  Here, when the excavation pipeline is disconnected from the excavation port, if there is no time in advance to replace the muddy water in the upper region with seawater, By performing the operation and replacing the muddy water in the upper region with seawater, the amplitude of the upper end of the excavation pipeline can be made smaller than before.

In this excavation pipe disconnection method, the drill pipe is provided with a lower end valve for restricting fluid flow at the lower end thereof, and the seawater is supplied into the drill pipe from the upper end with the lower end valve opened. Then, a part of the muddy water in the drill pipe may be pushed out from the lower end of the drill pipe, and the lower end valve may be closed when the muddy water and the seawater are replaced in the upper region of the drill pipe.
In this case, the muddy water in the upper region of the drill pipe can be easily replaced with seawater only by the operation of supplying seawater to the upper end of the drill pipe and the opening / closing operation of the lower end valve.

  The present invention also includes a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body that is provided outside the drill pipe and floats on the sea, and a riser pipe that connects an excavation port formed on the sea floor. Provided is a method for separating an excavation pipeline, in which a double-pipe excavation pipeline is separated from the excavation port, and the mud water in the lower region of the drill pipe is replaced with the sea water before and after the excavation port.

In this excavation pipeline separating method, when the excavation pipeline and the excavation port are separated, the upper region of the excavation pipeline is filled with muddy water and the lower region is filled with seawater.
Since the specific gravity of the muddy water is larger than the specific gravity of seawater, when the fluid in the excavation pipeline is included, the mass of the upper region of the excavation pipeline in the above state is larger than the mass of the lower region.

In this state, the excavation pipeline is approximately composed of a third spring having one end fixed, a third mass carriage connected to the other end of the third spring, and the third carriage. On the other hand, the fourth carriage with a small mass connected via the fourth spring can be replaced with a second spring / mass model having a configuration arranged in a straight line on a friction-free horizontal plane.
In this second spring-mass model, the mass of the third carriage is the mass of the upper area of the excavation pipeline including the internal mud, and the mass of the fourth carriage is for excavation including the internal seawater. The mass of the lower region of the pipeline. The spring constant of the third spring is the spring constant of the upper region of the excavation pipeline, and the spring constant of the fourth spring is the spring constant of the lower region of the excavation pipeline. The spring constants of these third and fourth springs can be regarded as approximately the same.

In the second spring / mass model, the fourth and fourth springs are separated from the third carriage by a predetermined distance from the natural length of the third and fourth springs, and then opened to vibrate each carriage. Then, in the second spring / mass model, compared to the case where the masses of the third carriage and the fourth carriage are equal, or the mass of the fourth carriage is larger than the mass of the third carriage. The amplitude of the fourth carriage is reduced.
This can be easily confirmed by numerically analyzing the behavior of the second spring / mass model based on the equation of motion or by actually conducting an experiment.
If this is applied to the actual excavation pipeline, when mud is located only in the upper region of the excavation pipeline, the excavation pipeline is separated from the excavation port as described above. It can be seen that even when vertical vibrations occur in the pipeline, the amplitude of the lower end of the excavation pipeline is smaller than that in the prior art. As a result, after the excavation pipeline is cut off, the lower end of the excavation pipeline does not easily collide with the spray-proof device that closes the excavation port or the seabed.

  Here, when disconnecting the excavation pipeline from the excavation port, if there is no time in advance to replace the muddy water in the lower region with seawater, By performing the operation to replace the muddy water in the lower region with seawater, the amplitude of the lower end of the excavation pipeline can be made smaller than the amplitude of the upper end thereafter.

In this excavation pipe disconnection method, the drill pipe is provided with a central valve for restricting the flow of fluid in the central portion in the longitudinal direction, and the central valve of the drill pipe is closed. The seawater may be supplied directly below the muddy water in the lower region of the drill pipe to replace the seawater.
In this case, the muddy water in the lower region of the drill pipe can be easily replaced with seawater only by opening / closing the central valve and supplying seawater to the upper end of the drill pipe.

  The present invention also includes a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body that is provided outside the drill pipe and floats on the sea, and a riser pipe that connects an excavation port formed on the sea floor. The excavation pipe having a double pipe structure is separated from the excavation port, and before and after this, the mud water in the other region is replaced with the sea water while leaving the mud water in the center in the longitudinal direction of the drill pipe. Provided is a method for separating a pipeline for excavation.

In this excavation pipeline separating method, when the excavation pipeline and the excavation port are separated, the central portion in the longitudinal direction of the excavation pipeline is filled with muddy water, and the vicinity of the upper end and the lower region are filled with seawater.
Since the specific gravity of mud is larger than the specific gravity of seawater, when the fluid in the excavation pipeline is included, in the excavation pipeline in the above state, the mass in the longitudinal center is the mass in the vicinity of the upper end and the mass in the lower region. Bigger than.

  In this state, the excavation pipeline is approximately composed of a fifth spring having one end fixed, a fifth small carriage connected to the other end of the fifth spring, and the fifth carriage. A large-mass sixth carriage connected to the sixth carriage via a sixth spring, and a small-mass seventh carriage connected to the sixth carriage via a seventh spring, It can be replaced with the behavior of a third spring / mass model configured in a straight line on a friction-free horizontal plane.

  In this third spring-mass model, the mass of the fifth carriage is the mass near the top of the excavation pipeline including the internal seawater, and the mass of the sixth carriage is for excavation including the internal mud. It is the mass of the central part in the longitudinal direction of the pipeline, and the mass of the seventh carriage is the mass of the lower region of the excavation pipeline including the internal seawater. The spring constant of the fifth spring is the spring constant near the upper end of the excavation pipeline, the spring constant of the sixth spring is the spring constant of the central portion in the longitudinal direction of the excavation pipeline, and the seventh The spring constant of the spring is the spring constant of the lower region of the excavation pipeline. The spring constants of the fifth, sixth, and seventh springs can be regarded as approximately the same.

In the third spring / mass model, after the fifth, sixth, and seventh springs are in the natural length, the seventh carriage is separated from the sixth carriage by a predetermined amount and then opened. When each carriage is vibrated, the amplitudes of the fifth and seventh carriages become smaller than when the masses of the fifth, sixth, and seventh carriages are made equal. This can be easily confirmed by experimenting the behavior of the third spring / mass model.
When this is applied to an actual excavation pipeline, when mud is located only in the central portion in the longitudinal direction of the excavation pipeline, the excavation pipeline is separated from the excavation port as described above. In addition, it can be understood that the amplitude of the upper and lower ends of the excavation pipeline can be smaller than that of the prior art even when vertical vibrations occur in the excavation pipeline.
As a result, after the excavation pipeline is cut off, the lower end of the excavation pipeline is less likely to collide with the spray-proof device or the seabed that closes the excavation port, and at the same time, the floating body on the sea is hardly pushed up by the upper end of the excavation pipeline. .

  Here, when disconnecting the excavation pipeline from the excavation port, if there is no time to replace the mud near the upper end and the mud in the lower area with seawater in advance, disconnect the excavation pipeline from the excavation port. Thereafter, the above operation is performed to replace the muddy water in the vicinity of the upper end and the muddy water in the lower region with seawater, so that the amplitude of the lower end and the upper end of the excavation pipeline can be reduced thereafter.

In this excavation pipe disconnection method, the drill pipe is provided with a central valve that regulates the flow of fluid in the central part in the longitudinal direction thereof, and the central valve is opened from the upper end to the drill pipe. Supplying seawater to push out a part of the muddy water in the drill pipe from the lower end of the drill pipe, and closing the central valve when the muddy water is replaced with the seawater in the vicinity of the upper end of the drill pipe The seawater may be supplied directly below the central valve of the drill pipe to replace the muddy water in the lower region of the drill pipe with the seawater.
In this case, the muddy water near the upper end of the drill pipe and the muddy water in the lower area can be easily replaced with seawater only by opening / closing the central valve and supplying seawater to the upper end of the drill pipe. .

  The present invention also includes a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body that is provided outside the drill pipe and floats on the sea, and a riser pipe that connects an excavation port formed on the sea floor. A double-pipe excavation pipeline, a separation device that separates the excavation pipeline from the excavation port, a lower end valve that regulates the flow of fluid at the lower end of the drill pipe, and the inside of the drill pipe And a seawater supply device for supplying the seawater from the upper end thereof.

  In the excavation pipeline separating device configured as described above, when the excavation pipeline and the excavation port are separated by the separation device, the seawater is supplied from the upper end into the drill pipe by the seawater supply device. Push down the muddy water to the specified height, discharge the excess muddy water from the lower end of the drill pipe, and close the lower end valve in this state, replacing the muddy water in the upper area with seawater while filling the lower area of the drill valve with muddy water can do.

The behavior of the excavation pipeline in this state is the same as that of the first spring / mass model. Therefore, by separating the excavation pipeline from the excavation port, the excavation pipeline is moved up and down as described above. Even if vibration occurs, the amplitude of the upper end of the excavation pipeline becomes smaller than that of the conventional one, and after the excavation pipeline is cut off, the floating body on the sea is hardly pushed up by the upper end of the excavation pipeline.
Here, when disconnecting the excavation pipeline from the excavation port, if there is no time in advance to replace the mud in the interior with seawater, the above operation is performed after disconnecting the excavation pipeline from the excavation port. The muddy water in a predetermined area may be replaced with seawater.

  The present invention also includes a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body that is provided outside the drill pipe and floats on the sea, and a riser pipe that connects an excavation port formed on the sea floor. A double-pipe excavation pipeline, a separation device that separates the excavation pipeline and the excavation port, a central valve that regulates the flow of fluid in the central portion in the longitudinal direction of the drill pipe, An excavation pipe disconnecting device having a seawater supply device for supplying the seawater immediately below the central valve of the drill pipe is provided.

  In the excavation pipeline separating device configured as described above, when the excavation pipeline and the excavation port are separated by the separation device, the seawater supply device closes the central valve of the drill pipe with the central valve closed. By supplying seawater to the seawater, it is possible to replace the muddy water in the lower area with seawater while filling the upper area of the drill pipe with muddy water.

The behavior of the excavation pipeline in this state is the same as that of the second spring / mass model. Therefore, by separating the excavation pipeline from the excavation port, the excavation pipeline is moved up and down as described above. Even if vibration occurs, the amplitude of the lower end of the excavation pipeline becomes smaller than before, and after the excavation pipeline is cut off, the lower end of the excavation pipeline collides with an anti-blowing device that closes the excavation port or the seabed. Hateful.
Here, when disconnecting the excavation pipeline from the excavation port, if there is no time in advance to replace the mud in the interior with seawater, the above operation is performed after disconnecting the excavation pipeline from the excavation port. The muddy water in a predetermined area may be replaced with seawater.

In this excavation pipe disconnection device, the seawater supply device may be capable of supplying seawater into the drill pipe from its upper end.
In this case, when separating the excavation pipeline and the excavation port by the separation device, the seawater is supplied from the upper end into the drill pipe by the seawater supply device and the mud in the drill pipe before the central valve is closed. The muddy water near the upper end of the drill pipe can be replaced with seawater by pushing down to the middle of the upper end and the center in the longitudinal direction. After that, by closing the central valve and supplying seawater into the drill pipe from directly below the central valve, the middle part of the drill pipe in the longitudinal direction is filled with muddy water, while the muddy water near the upper end and the muddy water in the lower region are filled. Can be replaced with seawater.

  The behavior of the excavation pipeline in this state is the same as that of the third spring / mass model. Therefore, by separating the excavation pipeline from the excavation port, the excavation pipeline is moved up and down as described above. Even if vibration occurs, the amplitude of the upper and lower ends of the excavation pipeline will be smaller than before, and after the excavation pipeline is disconnected, the lower end of the excavation pipeline will be attached to the jet-proof device and the seabed that block the excavation port. It is difficult to collide, and at the same time, it is difficult for the floating body on the sea to be pushed up by the upper end of the excavation pipeline.

Moreover, in each of the above-described excavation pipeline disconnecting devices, the seawater supply device replaces the muddy water and the seawater obtained in advance from the seawater supply start time based on the seawater supply capability of the seawater supply device. The operation may be stopped when the required time elapses.
In the excavation pipeline separating apparatus configured as described above, the replacement work between the muddy water and the seawater by the seawater supply device is continued for the required time in advance, so the replacement work between the muddy water and the seawater is accurately and automatically performed. Can be done automatically.

  Also, each of the excavation pipe disconnecting devices described above measures a weight measuring device that measures the weight of the excavating pipeline including the internal fluid, and the measured value of the weight measuring device is replaced with the muddy water and the seawater. And a control device that stops the replacement operation of the replacement device when the weight of the excavation pipeline including the internal fluid in a state where the replacement is completed.

As mentioned above, since the mud used in the riser excavation method has a higher specific gravity than seawater, the replacement of the mud in the excavation pipeline with seawater by the replacement device proceeds, and the amount of mud in the excavation pipeline As the value decreases, the weight of the excavation line including the internal fluid decreases. When the replacement is completed, the weight of the excavation pipe including the internal fluid takes a constant value.
The above-described excavation pipe disconnecting device utilizes this fact, and the control device controls the operation of the replacement device based on the measurement value of the weight measuring device, so that the replacement work of mud water and seawater can be performed accurately and automatically. It can be carried out.

Each of the excavation pipeline disconnecting devices may include a pump that sends the fluid in the excavation pipeline downward.
As described above, the mud used in the riser excavation method has a higher viscosity than seawater. Therefore, when the mud water in the excavation pipeline is replaced with the seawater by using its own weight, a certain amount of time is required. Take it.
Therefore, as described above, by providing a pump for sending the fluid in the excavation pipeline downward, the mud is moved at a higher speed, and the replacement of the mud with seawater is completed in a shorter time. be able to.

As a result, when replacing the muddy water and seawater before the separation of the excavation pipeline, the replacement operation can be quickly terminated and the excavation pipeline can be separated in a short time after the operation is started. it can.
In addition, when replacing the muddy water and seawater after separating the excavation pipeline, the excavation pipeline can be completed in a short time after the excavation pipeline is separated. The amplitude of the upper end and the lower end can be quickly reduced.

The present invention also provides a submarine excavation facility for excavating a seabed using a riser excavation method, the submarine excavation facility having the excavation pipeline separating device according to any one of claims 7 to 12.
In the submarine excavation equipment configured in this way, vertical vibrations at the time of disconnection of the excavation pipeline can be easily and effectively reduced by replacing part of the muddy water in the excavation pipeline with seawater. .

  As described above, according to the excavation pipeline disconnection method, excavation pipeline disconnection device, and submarine excavation equipment using the excavation pipeline disconnection method according to the present invention, the vertical vibration at the time of disconnection of the excavation pipeline is easy and effective. Can be reduced.

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 4.
As shown in FIG. 1, a seabed excavation facility 1 according to the present invention includes a drilling ship 2 (floating body) floating on the sea, a drill pipe 3 suspended from the drilling ship 2 in the sea S and drilling the seabed F, a drill It is provided in the excavation port 4 by the pipe 3 and has a blow-proof device 5 that seals the excavation port 4 when a fluid such as gas enters the excavation port 4 from within the formation.

  As shown in FIG. 2, a riser pipe 6 is provided around the drill pipe 3 to connect the excavation ship 2 and the spray-proof device 5. The drill pipe 3 and the riser pipe 6 form a double-pipe excavation pipeline 7. An annular space (annular A) is formed between the drill pipe 3 and the riser pipe 6, and fluid flows through the annular A.

As shown in FIG. 1, the blow-proof device 5 includes a lower portion 5a that is fixedly provided at the excavation port 4 and seals the excavation port 4, and an upper portion 5b that is provided so as to be separable from the lower portion 5a. The riser pipe 6 is connected to the lower part 5a through the upper part 5b.
That is, the anti-injection device 5 also serves as a separation device that separates the riser pipe 6 and the excavation port 4. The upper portion 5b is provided with a cutting mechanism that cuts the drill pipe 3 when the riser pipe 6 and the excavation port 4 are separated, and a lower end valve that restricts the flow of fluid from the lower end of the drill pipe 3. (Not shown).

The excavation ship 2 is provided with a riser tensioner 9 that pulls the riser pipe 6 upward, so that the riser pipe 6 is always stretched.
In addition, as shown in FIG. 2, the drilling vessel 2 is provided with a mud supply device 11 that supplies mud MW having a higher specific gravity and higher viscosity than the seawater SW from the upper end of the drill pipe 3. The muddy water MW supplied into the drill pipe 3 is conveyed downward through the drill pipe 3 and supplied to the tip of the drill pipe 3.
The muddy water supply device 11 also serves as a muddy water treatment device that collects the muddy water MW supplied to the tip of the drill pipe 3 through the annular A and performs a predetermined process. And the muddy water supply apparatus 11 is set as the structure which sends the muddy water MW which finished the process into the drill pipe 3, and reuses it.

Here, in this embodiment, the muddy water supply apparatus 11 constitutes a seawater supply apparatus that takes in the seawater SW through the lower end of the annular A and supplies the seawater SW into the drill pipe 3 from the upper end.
Further, as shown in FIG. 1, a pump 14 for sending the fluid in the drill pipe 3 downward is provided in the vicinity of the lower end of the excavation pipeline 7, thereby moving the fluid in the drill pipe 3. The speed is improved.

In the seabed excavation equipment 1 configured as described above, excavation is performed from the operating state shown in FIG. 3A (the drill pipe 3 is filled with the muddy water MW and the annular A is filled with the seawater SW). In separating the opening 4 and the excavation pipeline 7, the following operation is performed.
First, the supply of the muddy water MW into the drill pipe 3 by the muddy water supply device 11 is stopped, and the seawater SW is supplied into the drill pipe 3 from the upper end instead of the muddy water MW.
As a result, the muddy water MW in the drill pipe 3 is pushed down to the center in the longitudinal direction of the drill pipe 3, and excess muddy water MW is discharged from the lower end of the drill pipe 3. In this state, by closing the lower end valve provided in the blow-proof device 5b, the lower region of the drill pipe 3 is filled with the muddy water MW as shown in FIG. The muddy water MW is replaced with the seawater SW.
At this time, the time required for the above operation can be shortened by operating the pump 14 to actively move the fluid in the drill pipe 3.

  Here, in controlling the amount of the mud MW in the drill pipe 3, the vibration of the excavation pipeline 7 is minimized under various environmental conditions (such as mud specific gravity and excavation depth) in advance using an analysis model described later. The amount of retained mud MW is determined, and the amount of retained mud MW suitable for the current conditions is determined based on this information.

Then, when supplying the seawater SW by the mud supply device 11, the seawater supply capability (muddy water discharge capability) of the mud supply device 11 under various environmental conditions (such as the viscosity of the mud MW in the drill pipe 3) is obtained in advance. Based on this information, the time for operating the mud supply device 11 is determined so that an amount of mud MW suitable for the current condition remains in the drill pipe 3.
Thereby, the replacement | exchange operation | work with the muddy water MW and seawater SW by the muddy water supply apparatus 11 can be performed correctly and automatically.

Since the specific gravity of the muddy water MW is sufficiently larger than the specific gravity of the seawater SW (specific gravity is about 2), in the state shown in FIG. 3B, if the fluid in the excavation pipeline 7 is included, the lower portion of the excavation pipeline 7 The mass of the region is greater than the mass of the upper region.
As shown in FIG. 3C, the excavation pipeline 7 in this state is connected to the first spring C ₁ having one end fixed and the other end of the first spring C _1. and a first carriage M ₁ of the small mass and a second carriage M ₂ massive connected via a second spring C ₁ with respect to the first carriage M ₁ of the small mass, friction It can be replaced with a first spring / mass model having a configuration arranged in a straight line on a horizontal plane without any gaps.

In this first spring / mass model, the mass of the first carriage M _{1 is} the mass of the upper region of the excavation pipeline 7 including the internal mud MW, and the mass of the second carriage M ₂ is the internal mass. This is the mass of the lower region of the excavation pipeline 7 including the seawater SW. The spring constant of the first spring C _{1 is} the spring constant of the upper region of the excavation pipeline 7, and the spring constant of the second spring C _{2 is} the spring constant of the lower region of the excavation pipeline 7. The spring constants of the first and second springs C ₁ and C ₂ can be regarded as approximately the same.

In the first spring / mass model, the second carriage M ₂ is separated from the first carriage M ₁ by a predetermined amount in a state where the first and second springs C ₁ and C ₂ have a natural length. when opened vibrates the respective dolly then it was smaller than that first bogie M ₁ mass and a second bogie M ₂ mass when the same (i.e., conventional conditions). This can be easily confirmed by numerically analyzing the behavior of the first spring / mass model based on the equation of motion or by actually conducting an experiment.

  If this is applied to the actual excavation pipeline 7, the excavation pipeline 7 in the above-described state is separated from the excavation port 4, so that the excavation pipeline 7 generates vertical vibrations as described above. However, it can be seen that the amplitude of the upper end of the excavation pipeline 7 is smaller than that in the prior art. Thereby, after the excavation pipeline 7 is cut off, the excavation ship 2 is hardly pushed up by the upper end of the excavation pipeline 7.

Here, for reference, the eigenmode of the excavation pipeline 7 calculated based on the first spring-mass model with the mass ratio of the upper region and the lower region set to 1: 2 is shown in the graph of FIG. Shown in
In FIG. 4, for comparison, the eigenmode when the mass ratio between the upper region and the lower region is 1: 1 is indicated by a broken line, and the mass ratio between the upper region and the lower region is 2: 1. The eigenmode in this case is indicated by a solid line. As is apparent from FIG. 4, when the mass of the lower region is larger than that of the upper region, the amplitude of the upper region is smaller than in other cases.

  Here, when the excavation pipeline 7 is disconnected from the excavation port 4, the excavation pipeline 7 is removed from the excavation port 4 when there is no time to replace the muddy water MW in the upper region with the seawater SW in advance. After the separation, the above operation is performed to replace the muddy water MW in the upper region with the seawater SW, so that the amplitude of the upper end of the excavation pipeline 7 can be made smaller than before.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The seabed excavation equipment 31 according to this embodiment has the same configuration as the seabed excavation equipment 1 shown in the first embodiment, and as shown in FIGS. A central valve 32 that restricts the flow of fluid in the excavation pipeline 7 is provided in the central portion.

  In the present embodiment, the central valve 32 is configured to restrict the flow of fluid in the drill pipe 3 and the annular A. In addition, the central valve 32 is configured to cut the drill pipe 3 at the time of closing and regulate the flow of fluid in the cutting portion of the drill pipe 3 that is located above the cutting position.

Further, as shown in FIG. 5, the excavation pipeline 7 is provided with a seawater supply device 33 that supplies seawater SW into the drill pipe 3. As shown in FIG. 5 (a), the seawater supply device 33 starts from a state where the central valve 32 is open, and is located below the central valve 32 of the drill pipe 3 (see FIG. 5 (b)). The position where the upper end of the lower part 3a is separated from the lower end of the upper part 3b by a predetermined distance when a portion above the central valve 32 (hereinafter referred to as the “upper part 3b”) is separated. And a holding device 34 for holding the lower portion 3a.
In the submarine excavation equipment 51 of the present embodiment, the lower end valve need not be provided in the upper part 5b of the blow prevention device 5.

The holding device 34 is provided at a predetermined distance below the protrusion 34a that protrudes laterally from the upper end of the lower part 3a and the central valve 32 in the riser pipe 6 and protrudes when the lower part 3a is separated from the upper part 3b. And a support part 34b for receiving the part 34a.
Here, the holding device 34 allows the fluid to flow in the annular A, and when the holding device 34 holds the lower portion 3a, the fluid flows from the annular A into the lower portion 3a. Distribution is allowed.

  As described above, the seawater supply device 33 opens the upper end of the lower part 3a of the drill pipe 3 into the annular A so that the specific gravity between the mud MW filled in the lower part 3a and the seawater SW filled in the annular A is obtained. Due to the difference, the muddy water MW in the lower portion 3a is dropped, and the seawater SW in the annular A is taken into the lower portion 3a from the upper end of the lower portion 3a due to the negative pressure generated in the lower portion 3a along with the falling flow of the muddy water MW. It is like that.

In the seabed excavation equipment 31 configured as described above, excavation is performed from the operating state shown in FIG. 6A (the drill pipe 3 is filled with the mud MW and the annular A is filled with the seawater SW). In separating the opening 4 and the excavation pipeline 7, the following operation is performed.
First, the central valve 32 is closed, and the drill pipe 3 is cut and the lower end of the upper part 3b of the drill pipe 3 is closed.
In this state, as described above, the gap between the upper end of the lower part 3a of the drill pipe 3 and the upper part 3b is formed, so that the seawater supply device 33 plays its role, and the muddy water MW in the lower part 3a becomes the seawater SW. Is replaced by As a result, as shown in FIG. 6B, the muddy water MW in the lower portion 3b is replaced with the seawater SW while the upper portion 3b of the drill pipe 3 is filled with the muddy water MW.

Since the specific gravity of the muddy water MW is larger than the specific gravity of the seawater SW, when the fluid in the excavation pipeline 7 is included, the mass of the upper region of the excavation pipeline 7 in the state shown in FIG. Greater than mass.
As shown in FIG. 6C, the excavation pipeline 7 in this state is connected to the third spring C ₃ having one end fixed and the other end of the third spring C _3. A third plane M ₃ having a large mass and a fourth carriage M ₄ having a small mass connected to the third carriage M ₃ via a fourth spring C ₄ are arranged in a horizontal plane without friction. It can be replaced with a second spring / mass model configured in a straight line above.

In this second spring / mass model, the mass of the third carriage M _{3 is} the mass of the upper region of the excavation pipeline 7 including the internal mud MW, and the mass of the fourth carriage M ₄ is the internal mass. This is the mass of the lower region of the excavation pipeline 7 including the seawater SW. The spring constant of the third spring C _{3 is} the spring constant of the upper region of the excavation conduit 7, and the spring constant of the fourth spring C _{4 is} the spring constant of the lower region of the excavation conduit 7. The spring constants of the third and fourth springs M ₃ and M ₄ can be regarded as approximately the same.

In the second spring / mass model, the fourth carriage M ₄ is separated from the third carriage M ₃ by a predetermined amount from the state in which the third and fourth springs C ₃ and C ₄ are in the natural length. When the trucks are opened and then oscillated, the masses of the third carriage M ₃ and the fourth carriage M ₄ in the second spring / mass model are equal, or the mass of the fourth carriage M ₄ . the compared to the case of greater than a third of the mass of the carriage M _3, the amplitude of the fourth carriage M ₄ is reduced.
This can be easily confirmed by numerically analyzing the behavior of the second spring / mass model based on the equation of motion or by actually conducting an experiment.

  When this is applied to the actual excavation pipeline 7, when the muddy water MW is located only in the upper region of the excavation pipeline 7, the excavation pipeline 7 is separated from the excavation port 4. As described above, it can be seen that the amplitude of the lower end of the excavation pipeline 7 is smaller than that of the conventional one even when vertical vibrations occur in the excavation pipeline 7. Thus, after the excavation pipeline 7 is cut off, the lower end of the excavation pipeline 7 is less likely to collide with the spray-proof device 5 and the seabed F that block the excavation port 4.

Here, when the excavation pipeline 7 is disconnected from the excavation port 4, the excavation pipeline 7 is removed from the excavation port 4 when there is no time to replace the muddy water MW in the lower region with the seawater SW in advance. After the separation, the above operation is performed to replace the muddy water MW in the lower region with the seawater SW, so that the amplitude of the lower end of the excavation pipeline 7 can be made smaller than before.
In this state, the time required for the above operation can be shortened by operating the pump 14 to actively move the fluid in the drill pipe 3.

Here, for reference, the natural mode of the excavation pipeline 7 calculated based on the second spring / mass model with the mass ratio of the upper region and the lower region being 2: 1 is shown in the graph of FIG. Shown in
In FIG. 7, for comparison, the eigenmode when the mass ratio between the upper region and the lower region is 1: 1 is indicated by a broken line, and the mass ratio between the upper region and the lower region is 0.5: 1. The eigenmode in the case of (ie, 1: 2) is indicated by a solid line. As is apparent from FIG. 7, when the mass of the lower region is larger than that of the upper region, the amplitude of the upper region is smaller than the amplitude of the lower region.

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
The seabed excavation equipment 51 according to the present embodiment has the same configuration as the seabed excavation equipment 31 shown in the second embodiment. In the seabed excavation equipment 51, the central valve 32 is configured not to cut the drill pipe 3 when closed, and the seawater supply device 33 and the holding device 34 are omitted.

In the seabed excavation equipment 51 configured as described above, excavation is performed from the operating state shown in FIG. 8A (the drill pipe 3 is filled with the mud MW and the annular A is filled with the seawater SW). In separating the opening 4 and the excavation pipeline 7, the following operation is performed.
First, the supply of the muddy water MW into the drill pipe 3 by the muddy water supply device 11 is stopped, and the seawater SW is supplied into the drill pipe 3 from the upper end instead of the muddy water MW.

As a result, the muddy water MW in the drill pipe 3 is pushed down to the vicinity of the center in the longitudinal direction of the drill pipe 3, and excess muddy water MW is discharged from the lower end of the drill pipe 3. In this state, by closing the central valve 32, as shown in FIG. 8 (b), the central portion in the longitudinal direction of the drill pipe 3 is filled with a predetermined amount of muddy water MW, near the upper end and the lower portion. The area is filled with seawater.
At this time, the time required for the above operation can be shortened by operating the pump 14 to actively move the fluid in the drill pipe 3.

  Here, in controlling the amount of mud water MW in the drill pipe 3, the vibration of the excavation pipeline 7 is minimized under various environmental conditions (such as mud specific gravity and excavation depth) using an analysis model described later in advance. The amount of retained mud MW is determined, and the amount of retained mud MW suitable for the current conditions is determined based on this information.

Then, when supplying the seawater SW by the mud supply device 11, the seawater supply capability (muddy water discharge capability) of the mud supply device 11 under various environmental conditions (such as the viscosity of the mud MW in the drill pipe 3) is obtained in advance. Based on this information, the time for operating the mud supply device 11 is determined so that an amount of mud MW suitable for the current condition remains in the drill pipe 3.
Thereby, the replacement | exchange operation | work with the muddy water MW and seawater SW by the muddy water supply apparatus 11 can be performed correctly and automatically.

  Since the specific gravity of the muddy water is greater than the specific gravity of seawater, when the fluid in the excavation pipeline 7 is included, in the excavation pipeline 7 in the state shown in FIG. It is larger than the mass in the vicinity and the mass in the lower region.

As shown in FIG. 8C, the excavation pipeline 7 in this state is connected to the fifth spring C ₅ having one end fixed and the other end of the fifth spring C _5. and a fifth carriage M ₅ of the small mass, the sixth carriage M ₅ massive connected via a sixth spring C ₆ to this fifth carriage M _5, the sixth carriage The behavior of the third spring-mass model having a configuration in which a small mass seventh carriage M ₇ connected to M ₆ via a seventh spring C ₇ is arranged in a straight line on a friction-free horizontal plane. Can be replaced.

In this third spring / mass model, the mass of the fifth carriage M _{5 is} the mass in the vicinity of the upper end of the excavation pipeline 7 including the internal seawater SW, and the mass of the sixth carriage M ₆ is the internal mass. The mass of the excavation pipeline 7 including the muddy water MW is the mass in the longitudinal direction, and the mass of the seventh carriage M _{7 is} the mass of the lower region of the excavation pipeline 7 including the internal seawater SW. The spring constant of the fifth spring C _{5 is} the spring constant near the upper end of the excavation pipeline 7, and the spring constant of the sixth spring C _{6 is} the spring constant of the central portion in the longitudinal direction of the excavation pipeline 7. The spring constant of the seventh spring C _{7 is} the spring constant of the lower region of the excavation pipeline 7. The spring constants of the fifth, sixth, and seventh springs C ₅ , C ₆ , and C ₇ can be regarded as approximately the same.

In the third spring-mass model, fifth, sixth, and seventh spring C _5, C _6, from a state where C ₇ is in the natural length of the seventh carriage M ₇ of the sixth carriage M When vibrating the respective bogie open from ₆ After is separated a predetermined amount, the amplitude of the fifth carriage M ₅ and seventh carriage M ₇ is, fifth, sixth, seventh carriage M _5, M _6, smaller than that in the case of equal mass of M _7. This can be easily confirmed by experimenting the behavior of the third spring / mass model.
When this is applied to the actual excavation pipeline 7, when the mud MW is located only in the central portion in the longitudinal direction of the excavation pipeline 7, the excavation pipeline 7 is separated from the excavation port 4. Thus, it can be understood that the amplitude of the upper end and the lower end of the excavation pipeline 7 can be smaller than that of the prior art even when vertical vibrations occur in the excavation pipeline 7 as described above.
Thus, after the excavation pipeline 7 is cut off, the lower end of the excavation pipeline 7 is unlikely to collide with the jet-proof device 5 that closes the excavation port 4 or the seabed F, and at the same time, the upper end of the excavation pipeline 7 on the sea. It is difficult for the excavation ship 2 to be pushed up.

  Here, when the excavation pipeline 7 is separated from the excavation port 4, if there is no time to replace the mud MW near the upper end and the mud MW in the lower region with the seawater SW in advance, the excavation pipeline 7 is cut off from the excavation port 4 and the above operation is performed to replace the mud MW near the upper end and the mud MW in the lower region with the seawater SW. Thereafter, the amplitude and upper end of the lower end of the excavation pipeline 7 are changed. The amplitude can be made smaller than before.

It is a front view which shows the structure of the submarine excavation equipment concerning 1st embodiment of this invention. It is a partially broken front view which shows the structure of the submarine excavation equipment concerning 1st embodiment of this invention. It is a figure which shows operation | movement of the submarine excavation equipment concerning 1st embodiment of this invention, Comprising: (a) shows the mode at the time of operation, (b) shows the mode of the separation preparation stage of the excavation pipeline, (c) is a figure which shows the mechanical property of the pipe for excavation shown in (b). It is a graph which shows the natural mode of the pipe for excavation at the time of isolate | separating the pipe for excavation of the submarine excavation equipment concerning a first embodiment of the present invention from the excavation port. It is a principal part expanded sectional view of the submarine excavation equipment concerning a second embodiment of the present invention, (a) shows the mode at the time of operation, and (b) shows the mode of separation preparation stage of the excavation pipeline. Yes. It is a figure which shows operation | movement of the submarine excavation equipment concerning 2nd embodiment of this invention, Comprising: (a) shows the mode at the time of operation, (b) shows the mode of the isolation | separation preparatory stage of the excavation pipeline, (c) is a figure which shows the mechanical property of the pipe for excavation shown in (b). It is a graph which shows the natural mode of the pipeline for excavation at the time of isolate | separating the pipeline for excavation of the submarine excavation equipment concerning 2nd embodiment of this invention from an excavation port. It is a figure which shows operation | movement of the submarine excavation equipment concerning 3rd embodiment of this invention, Comprising: (a) shows the mode at the time of operation, (b) shows the mode of the isolation | separation preparatory stage of the excavation pipeline, (c) is a figure which shows the mechanical property of the pipe for excavation shown in (b).

Explanation of symbols

1,31,51 Submarine drilling equipment 2 Drilling ship (floating body)
3 Drill pipe 4 Drilling port 5 Anti-spray device (separator, lower end valve)
6 Riser pipe 7 Excavation pipes 11, 33 Mud supply device (seawater supply device)
14 Pump 32 Central valve F Submarine MW Muddy water SW Seawater

Claims (13)

Drilling with a double-pipe structure having a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body provided outside the drill pipe and floating on the sea, and a riser pipe connected to a drilling opening formed on the seabed Separating the pipeline from the excavation port;
Before and after this, the excavation pipe cutting method for replacing the muddy water in the upper region of the drill pipe with the seawater. The drill pipe is provided with a lower end valve that regulates the flow of fluid at the lower end thereof,
Supplying the seawater from the upper end into the drill pipe with the lower end valve opened, and extruding a part of the muddy water in the drill pipe from the lower end of the drill pipe,
2. The excavation pipe disconnection method according to claim 1, wherein the lower end valve is closed when the muddy water and the seawater are replaced in an upper region of the drill pipe. Drilling with a double-pipe structure having a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body provided outside the drill pipe and floating on the sea, and a riser pipe connected to a drilling opening formed on the seabed Separating the pipeline from the excavation port;
Before and after this, the excavation pipe cutting method for replacing the muddy water in the lower region of the drill pipe with the seawater. The drill pipe is provided with a central valve that regulates the flow of fluid at the central portion in the longitudinal direction,
The excavation pipe according to claim 3, wherein the seawater is supplied directly below the central valve of the drill pipe with the central valve closed to replace the mud in the lower region of the drill pipe with the seawater. Way separation method. Drilling with a double-pipe structure having a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body provided outside the drill pipe and floating on the sea, and a riser pipe connected to a drilling opening formed on the seabed Separating the pipeline from the excavation port;
Before and after this, the excavation pipe separation method for replacing the muddy water in the other region with the seawater while leaving the muddy water in the center in the longitudinal direction of the drill pipe. The drill pipe is provided with a central valve that regulates the flow of fluid at the central portion in the longitudinal direction,
The seawater is supplied from the upper end into the drill pipe with the central valve opened, and a part of the muddy water in the drill pipe is pushed out from the lower end of the drill pipe,
When the muddy water is replaced with the seawater in the vicinity of the upper end of the drill pipe, the central valve is closed and the seawater is supplied directly below the central valve of the drill pipe so as to form the lower region of the drill pipe. The excavation pipe disconnection method according to claim 5, wherein the muddy water is replaced with the seawater. Drilling with a double-pipe structure having a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body provided outside the drill pipe and floating on the sea, and a riser pipe connected to a drilling opening formed on the seabed Pipelines,
A separating device for separating the excavation pipeline and the excavation port;
A lower end valve for regulating fluid flow at the lower end of the drill pipe;
An excavation pipeline separating device having a seawater supply device for supplying the seawater from an upper end thereof into the drill pipe. Drilling with a double-pipe structure having a drill pipe to which mud having a specific gravity greater than seawater is supplied, a floating body provided outside the drill pipe and floating on the sea, and a riser pipe connected to a drilling opening formed on the seabed Pipelines,
A separating device for separating the excavation pipeline and the excavation port;
A central valve that regulates the flow of fluid at the central portion in the longitudinal direction of the drill pipe;
An excavation pipe disconnecting device comprising: a seawater supply device for supplying the seawater immediately below the central valve of the drill pipe.   9. The excavation pipeline disconnecting device according to claim 8, wherein the seawater supply device can supply the seawater into the drill pipe from its upper end.   The seawater supply device stops operating when the time required for the replacement work of the muddy water and the seawater obtained in advance based on the seawater supply capability of the seawater supply device has elapsed since the start of supplying the seawater. The excavation pipe disconnecting device according to any one of claims 7 to 9, wherein the excavation pipe disconnecting device is configured. A weight measuring device for measuring the weight of the pipe for excavation including the internal fluid;
Control for stopping the replacement operation of the replacement device when the measured value of the weight measuring device becomes the weight of the excavation pipe including the internal fluid in a state where the replacement of the muddy water and the seawater is completed The excavation pipe disconnecting device according to any one of claims 7 to 9, further comprising an apparatus.   The excavation pipeline disconnecting device according to any one of claims 7 to 11, further comprising a pump for sending the fluid in the excavation pipeline downward. A seabed drilling facility that drills the seabed using the riser drilling method,
A submarine excavation facility comprising the excavation pipeline separating device according to any one of claims 7 to 12.

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