JP6335605B2 - Gas recovery device and gas recovery method - Google Patents

Description

  The present invention relates to a gas recovery device that recovers methane gas, a gas recovery method, and methane gas recovered by the gas recovery method.

  Conventionally, natural gas mainly composed of methane gas is extracted from the gas layer and used commercially as an energy resource. Methane gas is a very effective energy resource from the viewpoint of global warming countermeasures because it emits less carbon dioxide during combustion than oil and coal.

  By the way, methane hydrate is attracting attention as a promising energy resource containing a large amount of methane gas. This methane hydrate is a clathrate hydrate surrounded by water molecules around methane, and exists in a low temperature and high pressure environment. And this methane hydrate exists in the sandy layer etc. of several hundred meters below the sea bottom.

  As a method of recovering methane gas from such methane hydrate, methane hydrate is decompressed by sucking up water in the production well extending to the layer containing methane hydrate, and methane hydrate is decomposed to recover methane gas. A decompression method is known (for example, Patent Document 1).

  Another method for recovering methane gas from methane hydrate is a heating method in which hot water or the like is injected into a layer containing methane hydrate through a production well and heated, and the methane hydrate is decomposed to recover methane gas. Is known (for example, Patent Document 2).

JP 2010-261252 A Japanese Patent No. 3914994

  However, even when methane gas is recovered from the production well using any one of the above-described decompression method and heating method, sand and water on the seabed (or lake bottom) are produced together with the methane gas. Then, after the methane gas mixed with sand and water is sucked up to the ocean or the land, separating the methane gas is time-consuming and leads to an increase in cost. Furthermore, if the distance of the pipe that sucks up the methane gas mixed with sand and water becomes long, the inside of the pipe may be blocked by the sand, and it is difficult to continuously recover the methane gas.

  The present invention has been made in view of the above-described circumstances. The gas recovery device, the gas recovery method, and the methane gas recovered by the gas recovery method are capable of continuously recovering methane gas while suppressing the cost. provide.

The present invention employs the following means in order to solve the above problems.
That is, the gas recovery device according to one aspect of the present invention is a gas recovery device that recovers methane gas from methane hydrate present on the seabed or lake bottom through a production well provided on the seabed or lake bottom, wherein the production A suction pipe that is inserted into a well and sucks a mixed fluid containing the methane gas, water, and sand in the methane hydrate , and is provided below the surface of the seabed or lake bottom and connected to the suction pipe, and the mixed fluid A separation device that separates the methane gas, water, and sand from the mixed fluid from each other by a specific gravity difference, and a decompression unit that is connected to the separation device and depressurizes the separation device. device includes a first gas separation section defining a space in which one end of the suction tube extends along the vertical direction are connected, said one stroke to communicate with the space at the top of the first gas separation section A first recovery part for recovering the methane gas in the separation part, a solid separation part having a tubular member extending along the seabed or lake bottom, and a lower part of the first gas separation part. And a connecting portion.

According to such a gas recovery device, the pressure in the separation device is reduced by the pressure reduction unit, so that the production well is reduced in pressure through the separation device, so that methane hydrate is decomposed by a so-called pressure reduction method, and methane gas Occurs. And this methane gas is introduce | transduced into a separation apparatus with water and sand as a mixed fluid. Here, the separation device is provided under the surface of the water, and it is not necessary to suck the mixed fluid up to the surface of the water or to the land through the suction pipe, and the separation of the mixed fluid under the surface of the water can recover only the methane gas on the surface of the water. It becomes possible.
Further, in this separation device, since the first gas separation part defines a space extending in the vertical direction, only the methane gas is separated from the mixed fluid by a specific gravity difference in the space, and the first gas separation part is disposed above the first gas separation part. It becomes possible to collect. Therefore, only methane gas can be recovered through the first recovery unit.
Furthermore, since the solid separation part has a tubular member extending along the seabed or the lake bottom, when the mixed fluid from the first gas separation part flows into the tubular member, the mixed fluid flows through the tubular member, The sand is separated from the mixed fluid by the sand settling inside the tubular member due to the specific gravity difference.

  Moreover, the said tubular member in said gas recovery apparatus may be provided with two or more, and the said some tubular member may be connected to this connection part so that each may branch from the said connection part.

Thus, in the solid separation part, the tubular member is provided so as to branch into a plurality from the connection part. For this reason, the mixed fluid that has passed through the first gas separation section branches and flows to each tubular member. Therefore, compared with the case where only one tubular member is provided, the flow rate of the mixed fluid flowing through each tubular member can be reduced.
As a result, the time for the mixed fluid to pass through the solid separation part can be lengthened, and the sedimentation time of sand can be lengthened. Therefore, even if the length of the tubular member is shortened, a sufficient sand settling time can be ensured, so that the compactness can be achieved by shortening the length of the tubular member. In addition, by providing a plurality of tubular members, the tube diameter of each tubular member can be made smaller than when only one tubular member is provided. As a result, the pressure resistance against the water pressure of the solid separation unit can be enhanced. As the pressure resistance is improved, the thickness of the tubular member can be reduced, leading to cost reduction.

  The gas recovery device includes a second gas separation unit that communicates with one end of the tubular member on the side away from the first gas separation unit, and that defines a space extending along the seabed or lake bottom. And a second recovery portion that communicates with the space above the second gas separation portion and recovers the methane gas in the second gas separation portion.

  By providing such a second gas separation unit, the mixed fluid that has passed through the solid separation unit is circulated along the seabed or lake bottom, and the methane gas remaining in the mixed fluid is separated by a specific gravity difference while increasing the separation time, It becomes possible to collect in the upper part of a 2nd gas separation part. Furthermore, this methane gas can be recovered through the second recovery unit.

  Further, the gas recovery apparatus includes a first flushing pipe connected to the one end portion of the tubular member and allowing water to flow into the tubular member toward the connection portion, and the first flushing pipe. A first opening and closing device that opens and closes; a second flushing pipe that is connected to the connection part and allows water to flow into the connection part toward the connection part; and a second opening and closing part that opens and closes the second flushing pipe The apparatus may further include a discharge portion that is provided in the connection portion at a position different from the position where the second flushing pipe is connected and discharges the water that has flowed into the connection portion.

  Since the first flushing tube, the second flushing tube, and the discharge portion are provided in this way, the first flushing tube is opened by the first opening / closing device, thereby allowing water to flow into the tubular member, that is, the solid separation portion. be able to. Therefore, the sand that has settled inside the tubular member can be washed away together with water toward the connecting portion. Thereafter, the second flushing pipe is opened by the second opening / closing device to allow water to flow into the connecting portion, and the sand in the connecting portion can be discharged by the discharging portion together with this water. That is, sand can be discharged from the separation device by flushing.

  In the gas recovery apparatus, the first flushing pipe and the second flushing pipe are connected to the decompression section, and the water is caused to flow into the tubular member and the connection section by the power of the decompression section. May be.

  In this manner, the flushing in the separation device can be performed using the power of the decompression unit, and there is no need to separately provide a pump for feeding water to the solid separation unit and the connection unit.

  Furthermore, the gas recovery device may further include a suction auxiliary unit that is installed in the production well and actively sucks the mixed fluid from the production well toward the separation device into the suction pipe. .

  With such a suction auxiliary part, the mixed fluid from the production well can be positively and forcibly introduced into the separation device. Therefore, it can suppress that sand accumulates in a suction pipe and obstruct | occludes a suction pipe.

  The suction auxiliary portion is inserted into the suction pipe and extends in a rod shape centered on the axis, and is provided to protrude from the outer peripheral surface of the main body, and is formed in a spiral shape toward the axis. An auger having a blade portion, and a drive portion that rotatably supports the main body portion around the axis.

  By such an auxiliary suction portion, the auger can be rotated, and the sand in the production well can be lifted upward in accordance with the rotation of the blade portion of the auger, so that the suction of the sand in the suction pipe can be promoted.

  The suction auxiliary part connects the ejection pipe inserted into the production well, the flow pipe connected to the first recovery part and through which the methane gas flows, the suction pipe and the flow pipe, and the methane gas And a jetting device that blows into the production well through the jetting pipe.

  By blowing the methane gas recovered by the first recovery unit from the first gas separation unit into the production well by such a suction auxiliary unit, the sand in the production well can be agitated and the amount of sand sucked by the suction pipe can be increased. it can.

  The gas recovery method according to an aspect of the present invention is a gas recovery method for recovering the methane gas by separating the water and the sand from the mixed fluid using the gas recovery device, Through a first introduction step of introducing the mixed fluid into the first gas separation unit, a first separation step of separating the methane gas from the mixed fluid by the first gas separation unit by a specific gravity difference, and the first recovery unit A recovery step of recovering the methane gas separated by the first gas separation unit, and a second introduction step of introducing the mixed fluid from the first gas separation unit into the solid separation unit via the connection unit; And a second separation step in which the sand is settled and separated by the tubular member in the solid separation part.

  According to such a gas recovery method, the methane hydrate is decomposed by a so-called decompression method, and the methane gas in the methane hydrate is introduced into the separation device as a mixed fluid together with water and sand. Here, this separation device is provided under the surface of the water, and it is not necessary to suck the mixed fluid up to the surface of the water or the land through the suction pipe, and the mixed fluid is separated under the surface of the water to collect only methane gas on the surface of the water. Is possible.

  Further, in the gas recovery method, the first flushing step in which water flows into each of the tubular members in the solid separation portion toward the connection portion, and the water flows in toward the connection portion. And a second flushing step that is allowed to flow out later.

  By such a first flushing step, it is possible to flush the solid separation portion and the sand from the solid separation portion to the connection portion with water. In addition, it is possible to flush the connecting portion by the second flushing step and discharge sand from the connecting portion. As a result, the retention of sand in the solid separation unit can be suppressed, the separation device can function normally, and methane gas can be recovered.

  Moreover, the methane gas which concerns on 1 aspect of this invention is collect | recovered by said gas recovery method.

  According to the gas recovery device of the first aspect, it is not necessary to separate the methane gas after sucking up the methane gas mixed with sand and water to the ocean or the land, and it is possible to continuously recover the methane gas while suppressing the cost.

  Further, according to the gas recovery device of the second aspect, the sand separation effect in the solid separation part can be improved by the plurality of tubular members.

  Further, the gas recovery device of claim 3 can further improve the separation effect of methane gas in the separation device by the second gas separation unit, which leads to further improvement of productivity of methane gas.

  Further, according to the gas recovery device of the fourth aspect, it is possible to suppress the stagnation of sand in the solid separation unit, and it is possible to recover the methane gas by continuously operating the separation device normally.

  Further, according to the gas recovery device of the fifth aspect, by performing flushing of the separation device using the decompression unit that decompresses the inside of the separation device, it becomes possible to discharge sand from the separation device while suppressing cost. .

  Moreover, according to the gas recovery device of the sixth aspect, the methane gas can be continuously recovered from the production well by the suction auxiliary portion.

  Further, according to the gas recovery device of the seventh aspect, the auger can prevent the suction pipe from being more effectively blocked, and methane gas can be continuously recovered from the production well.

  Moreover, according to the gas recovery device of the eighth aspect, it is possible to suppress the suction pipe from being effectively blocked by the ejection pipe, and methane gas can be continuously recovered from the production well.

  Further, according to the gas recovery method of claim 9, it is not necessary to separate the methane gas after the methane gas mixed with sand and water is sucked up to the ocean or the land, and it is possible to continuously recover the methane gas while suppressing the cost. Become.

  Further, according to the gas recovery method of the tenth aspect, it is possible to suppress the retention of sand in the solid separation part, and it is possible to recover the methane gas by continuously operating the separator normally.

Moreover, according to the methane gas collect | recovered by the gas recovery method of Claim 9 or 10, it can collect | recover continuously, restraining cost.

It is a whole side view showing the gas recovery device concerning a first embodiment of the present invention. It is a side view of the separation device in the gas recovery device concerning a first embodiment of the present invention. It is a top view of the separation apparatus in the gas recovery apparatus which concerns on 1st embodiment of this invention, Comprising: The arrow A of FIG. 2 is shown. It is a front view of the separation apparatus in the gas recovery apparatus which concerns on 1st embodiment of this invention, Comprising: The arrow B of FIG. 2 is shown. It is a flow figure showing the work procedure of the gas recovery method which collects methane gas with the gas recovery device concerning a first embodiment of the present invention. (A) shows the flow of steady operation, and (b) shows the flow of flushing operation. It is a whole side view which shows the gas recovery apparatus which concerns on 2nd embodiment of this invention.

[First embodiment]
Hereinafter, a gas recovery apparatus 1 according to an embodiment of the present invention will be described in detail with reference to the drawings.
The gas recovery apparatus 1 is an apparatus for recovering the generated methane gas G by decomposing methane hydrate present in, for example, the sea floor BS by a decompression method.

  As shown in FIG. 1, the gas recovery device 1 is connected to the suction pipe 2 installed in the production well 100 provided in the vertical hole formed in the seabed BS, and installed in the seabed BS. A separation device 3, a pump 4 (decompression unit) connected to the separation device 3, and a suction auxiliary unit 5 provided in the production well 100 are provided.

  Here, the production well 100 is provided inside a vertical hole drilled downward from the seabed BS so as to extend to the methane hydrate layer H where methane hydrate in the ground of the seabed BS exists. The production well 100 mainly includes a metal tube 101 provided so as to cover the inner surface of the vertical hole. Inside the metal pipe 101 in the upper part of the production well 100, a packer 102 capable of sealing the production well 100 in a state where the suction pipe 2 is inserted into the production well 100 is provided.

  The suction pipe 2 is inserted into the production well 100 so that the mixed fluid F including the methane gas G, the seawater W, and the sand S from the methane hydrate layer H can flow. Further, the end of the suction pipe 2 that protrudes from the production well 100 into the sea extends through a bent portion 2a that bends along the seabed BS, and is connected to the separation device 3 so that the separation device 3 3 is communicated. The gap between the suction pipe 2 and the production well 100 can be sealed by the packer 102 described above.

  The suction assisting part 5 has an auger 11 provided by being inserted into the suction pipe 2 and a drive part 12 that rotatably supports the auger 11.

  The auger 11 is inserted into the suction pipe 2 and extends in a rod shape centered on the axis O, and is provided to protrude from the outer peripheral surface of the main body 11a, and is formed in a spiral shape in the direction of the axis O. And a blade portion 11b.

The main body portion 11 a extends to the vicinity of the bottom surface of the production well 100.
The blade portion 11b is formed so as to be twisted toward the one side in the direction of the axis O in the circumferential direction of the main body portion 11a.

The drive unit 12 is a motor or the like that rotatably supports the main body 11a of the auger 11, and rotates the entire auger 11 by rotating the main body 11a around the axis O. The rotation direction of the auger 11 is counterclockwise when the auger 11 is viewed from above when the blade portion 11b is formed in a right-hand thread shape. On the other hand, when the blade | wing part 11b is formed in left-handed screw shape, it sees the auger 11 from upper direction, and becomes clockwise.
In the present embodiment, the drive unit 12 is disposed above the bent portion 2a of the suction pipe 2 and is inserted into the suction pipe 2 so as to penetrate the suction pipe 2 at the bent portion 2a.

The pump 4 decompresses the inside of the separating apparatus 3 by sucking out the seawater W in the separating apparatus 3, and depressurizes the production well 100 through the suction pipe 2 accordingly.
Here, a discharge pipe 38 is connected to the pump 4, and a discharge valve 39 that opens and closes the discharge pipe 38 is provided.

Next, details of the separation device 3 will be described with reference to FIGS.
The separation device 3 includes a first gas separation unit 21 to which the suction pipe 2 is connected, a branch unit 22 (connection unit) connected to the downstream side of the flow of the mixed fluid F from the first gas separation unit 21, and a branch The solid separation unit 23 connected to the downstream side of the unit 22, the second gas separation unit 24 connected to the downstream side of the solid separation unit 23, and the discharge unit 25 connected to the downstream side of the second gas separation unit 24. And have.

  In addition, the separation device 3 includes a first recovery unit 26 connected to the top of the first gas separation unit 21, a second recovery unit 27 connected to the top of the second gas separation unit 24, and a solid separation unit 23. And a flushing section 28 for allowing the seawater W to flow into the branch section 22.

  The first gas separation section 21 has a first gas separation pipe 21a that extends along the vertical direction and has a circular shape that bends along the seabed BS at the bottom. The mixed fluid F from the production well 100 flows into the space inside the first gas separation pipe 21 a through the suction pipe 2. Further, the methane gas G in the mixed fluid F that has flowed in is separated from the sand S and the seawater W by the difference in specific gravity, and the separated methane gas G is collected in the upper part.

The first recovery part 26 is a first recovery pipe 26a having a circular shape communicating with the space inside the first gas separation pipe 21a, and a first recovery pipe 26a that opens and closes the first recovery pipe 26a. And a valve device 26b.
When the first valve device 26b is opened, the methane gas G collected in the upper part of the first gas separation pipe 21a flows out of the separation apparatus 3 through the first recovery pipe 26a.

The branch part 22 has a branch pipe 22a extending along the seabed BS so as to form a circular tube and to be orthogonal to the first gas separation pipe 21a. The branch pipe 22a is connected to and communicates with a lower bent portion of the first gas separation pipe 21a so that the mixed fluid F from the first gas separation pipe 21a flows into the branch pipe 22a.
The vertical position where the branch portion 22 is connected to the first gas separation pipe 21a is from the liquid surface of the mixed fluid F in the first gas separation portion 21, that is, the boundary surface between the gas phase and the liquid phase. Further, it is preferable to control the opening and closing of the first valve device 26b in the first recovery unit 26 so as to be positioned below.

The solid separation part 23 has a plurality of (two in this embodiment) solid separation pipes 23a (tubular members) connected to and communicating with the branch part 22 and extending along the seabed BS.
In the present embodiment, these solid separation pipes 23a are based on the central axis perpendicular to the extending direction of the branch pipe 22a from the positions on both ends of the branch pipe 22a through the central position in the extending direction of the branch pipe 22a. As shown in FIG. 2, the axis extends symmetrically and in parallel to each other so as to be orthogonal to the extending direction of the branch portion 22.

  The mixed fluid F flows from the branch portion 22 into the space inside the solid separation tube 23a. Further, the sand S in the mixed fluid F that has flowed in is separated from the seawater W by the difference in specific gravity, and the separated sand S is allowed to settle in the lower part of each solid separation pipe 23a.

  The second gas separation unit 24 is connected to and communicates with each solid separation tube 23a, and an oblique tube 24b having a tubular shape, and a tubular shape connected to and communicated with the oblique tube 24b so as to collect these oblique tubes 24b. And a second gas separation pipe 24a.

  The oblique tube 24b is connected to an end portion of the solid separation tube 23a on the side away from the first gas separation portion 21, and inclines so as to gradually approach each other as it goes upward along the vertical direction from this end portion. Is provided.

  One end of the second gas separation tube 24a is connected to the oblique tube 24b, and extends toward the first gas separation tube 21a along the seabed BS. That is, the second gas separation tube 24a is provided above the solid separation tube 23a so as to be parallel to the solid separation tube 23a. In the present embodiment, the second gas separation pipe 24a is a position sandwiched between the two solid separation pipes 23a, and is located on the central axis passing through the central position in the extending direction of the branch pipe 22a. One is arranged.

  The mixed fluid F flows into the space inside the second gas separation pipe 24a from the solid separation section 23 through the oblique pipe 24b. Further, among the inflowing mixed fluid F, the methane gas G remaining in the mixed fluid F without being separated by the first gas separation unit 21 is separated from the seawater W by the difference in specific gravity, and the separated methane gas G is placed in the upper part. It comes to collect.

  The second recovery part 27 is provided in the second recovery pipe 27a and the second recovery pipe 27a that extends in the vertical direction and forms a circular tube that communicates with the space inside the second gas separation pipe 24a. A second valve device 27b for opening and closing the tube 27a.

  The second recovery pipe 27a is connected to the second gas separation pipe 24a at the end of the second gas separation pipe 24a on the side close to the first gas separation section 21.

  The second valve device 27b causes the methane gas G collected at the top in the second gas separation tube 24a to flow out of the separation device 3 through the second recovery tube 27a by opening the second recovery tube 27a.

  The discharge part 25 is connected to the second gas separation part 24 at the end of the second gas separation pipe 24a on the side close to the first gas separation part 21, that is, at the position where the second recovery pipe 27a is connected. A vertical tube 25a having a circular tube shape and a horizontal tube 25b having a circular tube shape connected to and communicated with the lower end of the vertical tube 25a are provided.

  The vertical pipe 25a extends downward in the vertical direction, which is the opposite direction to the second recovery pipe 27a, and its lower end is located further below the vertical position where the solid separation pipe 23a is provided. .

  The horizontal tube 25b is connected to the vertical tube 25a and extends so as to be separated from the first gas separation unit 21 along the seabed BS. That is, the horizontal tube 25b is provided below the solid separation tube 23a so as to be parallel to the solid separation tube 23a. Further, in the present embodiment, the horizontal tube 25b is located between the two solid separation tubes 23a, and one is arranged on the central axis passing through the central position in the extending direction of the branch portion 22. ing.

  And the pump 4 is connected to the edge part on the side spaced apart from the 1st gas separation pipe | tube 21a of this horizontal pipe 25b, and seawater W is discharged from the separation apparatus 3 to the exterior (underwater) through the horizontal pipe 25b. Yes.

  The flushing section 28 includes a first flushing pipe 31 connected to an end of the solid separation pipe 23a that is separated from the first gas separation section 21, a first opening / closing device 32 that opens and closes the first flushing pipe 31, and a branch. It has the 2nd flushing pipe | tube 33 connected to the one end part of the pipe | tube 22a, the 2nd opening / closing device 34 which opens and closes the 2nd flushing pipe | tube 33, and the discharge part 35 connected to the other end part of the branch pipe. .

  One first flushing pipe 31 is provided in each solid separation pipe 23a so that seawater W flows into each solid separation pipe 23a.

  The first opening / closing device 32 is a valve device and switches presence / absence of inflow of seawater W into the solid separation pipe 23a.

  The second flushing pipe 33 allows the seawater W to flow into the branch pipe 22a.

  The second opening / closing device 34 is a valve device and switches presence / absence of inflow of the seawater W into the branch pipe 22a.

Here, the other end of the branch pipe 22a is opened, and the discharge part 35 is a lid member that can open and close the opening.
In the discharge unit 35, the lid member may be electrically controlled to open and close by a control unit (not shown), or when the seawater W about to flow out of the branch pipe 22a exceeds a predetermined pressure, The lid member may be mechanically controlled so as to open the opening by this pressure and to close the lid member below a predetermined pressure.
Further, the discharge unit 35 may be configured to include a pipe connected to the opening of the branch pipe 22a and a valve device provided in the pipe instead of such a lid member. The seawater W can be discharged from the branch pipe 22a by controlling the opening and closing of the valve device.

  Furthermore, the first opening / closing device 32 and the second opening / closing device 34 may use a lid member similar to the discharge unit 35 instead of the valve device.

  In the present embodiment, the first flushing pipe 31 and the second flushing pipe 33 are connected to the pump 4 via the connection pipe 40. More specifically, the connection pipe 40 extends so as to branch from the discharge pipe 38 between the pump 4 and the discharge valve 39, and connects the two second flushing pipes 33 and the first flushing pipe 31 in parallel. doing.

  Next, the operation of the gas recovery apparatus 1 of the present embodiment will be described along with the method for recovering the methane gas G along FIG.

  As shown in FIG. 5A, first, the separation device 3 is decompressed by the pump 4. Since the inside of the production well 100 communicates with the separation device 3 through the suction pipe 2, the inside of the production well 100 is also decompressed as the separation device 3 is decompressed. Decomposition is performed, and methane gas G is generated.

  And this methane gas G is introduce | transduced into the 1st gas separation part 21 in the separation apparatus 3 as the mixed fluid F with the seawater W and the sand S (1st introduction process S1).

  Then, in the 1st gas separation part 21, only methane gas G is isolate | separated from the mixed fluid F by specific gravity difference, and it collects on the upper part of the 1st gas separation part 21 (1st separation process S2). The methane gas G thus separated is recovered through the first recovery unit 26 (first recovery step S3).

  Next, the mixed fluid F after the methane gas G is separated by the first gas separation unit 21 flows into the branching unit 22 and is further branched and introduced into the solid separation pipe 23a in the solid separation unit 23 (first). Two introduction steps S4).

  As described above, when the mixed fluid F from the first gas separation unit 21 flows into the solid separation tube 23a, the sand S has a specific gravity inside the solid separation tube 23a while the mixed fluid F flows through the solid separation tube 23a. The sand S is separated from the mixed fluid F by settling due to the difference (second separation step S5).

  Then, the mixed fluid F that has passed through the solid separation unit 23 is collected from each solid separation tube 23a through the inclined tube 24b and introduced into the second gas separation tube 24a (third introduction step S6). In the second gas separation pipe 24a, the methane gas G remaining in the mixed fluid F without being separated by the first gas separation section 21 is separated by the difference in specific gravity and collected on the second gas separation pipe 24a (third separation). Step S7).

  The methane gas G collected at the upper part of the second gas separation pipe 24a is recovered through the second recovery part 27 (second recovery step S8).

  Thereafter, seawater W of the mixed fluid F is introduced into the vertical pipe 25a and the horizontal pipe 25b in the discharge section 25, and discharged to the outside of the separation device 3 by the discharge pipe 38 connected to the pump 4 (discharge process S9). ).

  And in the steady operation state which isolate | separates the mixed fluid F by the separator 3 in this way, the discharge valve 39 is an open state, and the 1st opening / closing device 32 and the 2nd opening / closing device 34 are a closed state.

  On the other hand, when performing the flushing operation of the separation device 3 as shown in FIG. 5B, first, the discharge valve 39 provided in the pump 4 is closed, and the first opening / closing device 32 is opened. (First valve adjustment step S11).

  And the seawater W discharged from the discharge part 25 with the motive power of the pump 4 is made to flow in into the solid separation pipe 23a. As a result, the sand S that has settled in the solid separation tube 23a is swept away with the seawater W toward the branching portion 22 (first flushing step S12).

  And the 2nd opening / closing apparatus 34 is made into an open state (2nd valve adjustment process S13), and the seawater W discharged from the discharge part 25 with the motive power of the pump 4 is poured in into the branch pipe 22a. Then, the sand S that has been swept into the branch portion 22 by the first flushing step S12 and stayed in the branch pipe 22a is discharged from the branch portion 22 through the discharge portion 35 together with the seawater W (second flushing step S14).

  Note that the order of the first valve adjustment step S11 and the second valve adjustment step S13 may be reversed, or may be executed simultaneously. Further, the first valve adjustment step S11 may not be executed. That is, the second opening / closing device 34 may be opened while the first opening / closing device 32 is opened.

  According to such a gas recovery device 1, the separation device 3 is provided on the seabed BS, that is, below the water surface, and it is not necessary to suck the mixed fluid F up to the water surface through the suction pipe 2. It becomes possible to collect only the methane gas G on the water surface by performing the separation.

  Further, in the separation device 3, only the methane gas G is separated from the mixed fluid F by the specific gravity difference by the first gas separation pipe 21a extending in the vertical direction, and can be collected on the upper part of the first gas separation pipe 21a. Therefore, only the methane gas G can be recovered through the first recovery unit 26.

  Furthermore, the solid separation part 23 has a plurality of solid separation pipes 23 a extending along the seabed BS, and these solid separation pipes 23 a are provided so as to branch into a plurality from the branch part 22. For this reason, the mixed fluid F that has passed through the first gas separation unit 21 is branched and circulated to each solid separation pipe 23a. That is, as compared with the case where only one solid separation tube 23a is provided, the flow rate of the mixed fluid F flowing through each solid separation tube 23a can be reduced.

  As a result, the time for the mixed fluid F to pass through the solid separation unit 23 can be lengthened, and the sedimentation time of the sand S can be lengthened to improve the sand S separation effect. Therefore, even if the length of the solid separation tube 23a is shortened, a sufficient sedimentation time of the sand S can be ensured. Therefore, the length of the solid separation tube 23a can be shortened, and the compactness can be achieved. it can.

  Further, by providing a plurality of solid separation tubes 23a, it is possible to reduce the diameter of each solid separation tube 23a as compared to the case where only one solid separation tube 23a is provided. As a result, the pressure resistance against the water pressure of the solid separation tube 23a can be enhanced. As the pressure resistance improves, the thickness of the solid separation tube 23a can be reduced, leading to cost reduction.

  Further, by providing the second gas separation pipe 24a as the second gas separation section 24, the mixed fluid F that has passed through the solid separation section 23 is circulated along the seabed BS, so that the separation fluid can be obtained while increasing the separation time. The methane gas G remaining in the gas can be separated by the specific gravity difference and collected on the upper part of the second gas separation pipe 24a. Further, the methane gas G can be recovered through the second recovery unit 27. Therefore, the effect of separation and recovery of the methane gas G can be improved, and the productivity of the methane gas G can be improved. In addition, the amount of methane gas G flowing into the pump 4 can be reduced, the occurrence of cavitation in the pump 4 can be suppressed, and damage to the pump 4 can be suppressed.

  Further, by providing the flushing portion 28, it is possible to perform the flushing in which the sand S settled in the solid separation pipe 23a is discharged to the outside of the separation device 3 through the branch pipe. Thereby, it can suppress that sand S accumulates in the solid separation part 23, the separation apparatus 3 is made to function normally continuously, and recovery of the methane gas G is attained.

  Further, in the present embodiment, since the flushing is performed by the power of the pump 4, it is not necessary to separately provide a pump or the like for feeding the seawater W to the solid separation unit 23 and the branching unit 22. The sand S can be discharged from.

  Further, by rotating the auger 11 as the suction auxiliary portion 5, the sand S in the production well 100 is lifted upward according to the rotation of the blade portion 11 b of the auger 11, so that the sand S in the suction pipe 2 is lifted. Inhalation can be promoted. Therefore, it can suppress more effectively that the suction pipe 2 is obstruct | occluded with the sand S in the mixed fluid F, and can collect | recover methane gas G from the production well 100 continuously.

  According to the gas recovery apparatus 1 of the present embodiment, it is not necessary to separate the methane gas G after sucking the methane gas G mixed with sand S and seawater W to the ocean or land, and it is possible to recover the methane gas G while reducing costs. Become.

[Second Embodiment]
Hereinafter, with reference to FIG. 6, the gas collection | recovery apparatus 51 which concerns on 2nd embodiment of this invention is demonstrated.
In addition, the same code | symbol is attached | subjected to the component similar to 1st embodiment, and detailed description is abbreviate | omitted.
In the present embodiment, the suction auxiliary portion 55 is different from the first embodiment.

  The suction auxiliary portion 55 connects the ejection pipe 55a inserted into the production well 100, the circulation pipe 55b connected to the first recovery pipe 26a and through which the methane gas G circulates, and the ejection pipe 55a and the circulation pipe 55b. There is an ejection device 55c that blows methane gas G into the production well 100 through the ejection pipe 55a.

  The methane gas G collected by the first gas separation unit 21 circulates through the circulation pipe 55b.

  In the present embodiment, the ejection device 55c is disposed above the bent portion 2a of the suction pipe 2. And it is a compressor etc. which pumps methane gas G from the distribution pipe 55b toward the ejection pipe 55a.

  The ejection pipe 55a is connected to the ejection device 55c. In the present embodiment, the ejection pipe 55a is inserted into the suction pipe 2 so as to penetrate the suction pipe 2 at the bent portion 2a of the suction pipe 2, and the methane hydrate layer H The position extends to the bottom of the production well 100. Then, the methane gas G pumped by the ejection device 55c is blown into the production well 100.

  According to the gas recovery device 51 of the present embodiment, the auxiliaries 55 blow the methane gas G recovered by the first recovery unit 26 from the first gas separation unit 21 into the production well 100 by the suction auxiliary unit 55, thereby sand in the production well 100. S can be agitated and the suction amount of sand S can be increased by the suction pipe 2. Therefore, it is possible to suppress the suction pipe 2 from being blocked more effectively, and the methane gas G can be continuously recovered from the production well 100.

  In the present embodiment, the ejection pipe 55a may not be inserted into the suction pipe 2, and the suction pipe 2 and the ejection pipe 55a may be inserted into the production well 100 in parallel.

  Further, the seawater W may flow into the ejection pipe 55a together with the methane gas G. Further, the circulation pipe 55b may be connected to the second recovery pipe 27a, and the methane gas G recovered from the second gas separation unit 24 may be caused to flow into the ejection pipe 55a. Further, methane gas G, seawater W, and other fluids may be allowed to flow from other than the separation device 3, that is, from outside the gas recovery device 51.

As mentioned above, although embodiment of the gas collection | recovery apparatuses 1 and 51 of this invention was described, this invention is not limited to the structure shown by the said embodiment, It can change in the range which does not deviate from the meaning of this invention. it can.
For example, the first flushing pipe 31 and the second flushing pipe 33 may not be connected to the pump 4. That is, when the first flushing pipe 31 and the second flushing pipe 33 open into the sea and the first opening / closing device 32 and the second opening / closing device 34 are opened, only the pressure difference between the sea and the separation device 3 is obtained. The seawater W may be caused to flow into the solid separation unit 23 and the branching unit 22. Further, a pump for performing flushing may be provided separately from the pump 4.

  Moreover, the relative relationship of the installation position of the 1st gas separation part 21, the 2nd gas separation part 24, the solid separation part 23, the branch part 22, and the discharge part 25 is not limited to the above-mentioned case. For example, the horizontal tube 25 b in the discharge unit 25 may be disposed above the solid separation tube 23 a in the solid separation unit 23.

  The pipes in the first gas separation unit 21, the second gas separation unit 24, the solid separation unit 23, the branching unit 22, and the discharge unit 25 are not limited to those having a tubular member, and the mixed fluid F flows therein. The shape is not limited as long as it is a member in which a possible space is defined.

  A plurality of second gas separation tubes 24a may be provided so as to correspond to the respective solid separation tubes 23a.

  In addition, a plurality of solid separation tubes 23a are not necessarily provided.

  In the above-described embodiment, the pump 4 is used as the pressure reducing unit. However, for example, an air lift device may be provided instead of the pump 4. This air lift device reduces the specific gravity of water by blowing air into the water, and sucks out the water having a reduced specific gravity through a pumping pipe by water pressure.

  Furthermore, even when the methane hydrate layer is present at the bottom of the lake, the above gas recovery apparatuses 1 and 51 can be applied.

DESCRIPTION OF SYMBOLS 1 ... Gas recovery apparatus 2 ... Suction pipe 2a ... Bending part 3 ... Separation apparatus 4 ... Pump (pressure reduction part)
DESCRIPTION OF SYMBOLS 5 ... Suction assistance part 11 ... Auger 11a ... Main-body part 11b ... Blade | wing part 12 ... Drive part 21 ... 1st gas separation part 21a ... 1st gas separation pipe 22 ... Branch part (connection part)
22a ... Branch pipe 23 ... Solid separation part 23a ... Solid separation pipe (tubular member)
24 ... Second gas separation unit 24a ... Second gas separation tube 24b ... Slanting tube 25 ... Discharge unit 25a ... Vertical tube 25b ... Horizontal tube 26 ... First recovery unit 26a ... First recovery tube 26b ... First valve device 27 ... Second recovery section 27a ... second recovery pipe 27b ... second valve device 28 ... Flushing section 31 ... first flushing pipe 32 ... first opening / closing apparatus 33 ... second flushing pipe 34 ... second opening / closing apparatus 35 ... discharge section 38 ... Discharge pipe 39 ... Discharge valve 40 ... Connection pipe 100 ... Production well 101 ... Metal pipe 102 ... Packer G ... Methane gas W ... Sea water S ... Sand F ... Mixed fluid H ... Methane hydrate layer BS ... Submarine O ... Axis S1 ... First Introduction process S2 ... 1st separation process S3 ... 1st collection process S4 ... 2nd introduction process S5 ... 2nd separation process S6 ... 3rd introduction process S7 ... 3rd separation process S7 ... 2nd collection process S8 ... Discharge process S11 ... First One valve adjustment step S12 ... First flushing step S13 ... Second valve adjustment step S14 ... Second flushing step 51 ... Gas recovery device 55 ... Suction assisting portion 55a ... Jet pipe 55b ... Flow pipe 55c ... Jet device

Claims (10)

A gas recovery device for recovering methane gas from methane hydrate present on the sea bottom or lake bottom through a production well provided on the sea bottom or lake bottom,
A suction pipe inserted into the production well and sucking a mixed fluid containing the methane gas, water, and sand in the methane hydrate ;
A separator provided below the water surface of the seabed or lake bottom and connected to the suction pipe, wherein the mixed fluid is introduced and the methane gas, water, and sand are separated from each other by a specific gravity difference from the mixed fluid;
A decompression unit connected to the separation device for decompressing the separation device;
With
The separation device includes a first gas separation unit that defines a space that is connected to one end of the suction pipe and extends in the vertical direction;
A first recovery unit that communicates with the space at an upper portion of the first gas separation unit and recovers the methane gas in the first gas separation unit;
A solid separation portion having a tubular member extending along the seabed or lake bottom;
A communicating portion communicating with the tubular member and communicating with a lower portion of the first gas separating portion;
A gas recovery apparatus comprising: A plurality of the tubular members are provided,
The gas recovery apparatus according to claim 1, wherein the plurality of tubular members are connected to the connection portion so that each of the tubular members branches from the connection portion. A second gas separation portion that communicates with one end of the tubular member on the side away from the first gas separation portion, and that defines a space extending along the seabed or lake bottom;
A second recovery unit that communicates with the space above the second gas separation unit and recovers the methane gas in the second gas separation unit;
The gas recovery device according to claim 1, further comprising: A first flushing pipe connected to the one end of the tubular member to allow water to flow into the tubular member toward the connection part, and a first opening / closing device for opening and closing the first flushing pipe;
A second flushing pipe connected to the connection part for allowing water to flow into the connection part toward the connection part, and a second opening / closing device for opening and closing the second flushing pipe;
A discharge portion that is provided in the connection portion at a position different from the position where the second flushing pipe is connected, and discharges the water that has flowed into the connection portion;
The gas recovery device according to any one of claims 1 to 3, further comprising:   The said 1st flushing pipe | tube and the said 2nd flushing pipe | tube are connected to the said pressure reduction part, The said water is made to flow in the inside of the said tubular member and the said connection part with the motive power of this pressure reduction part. The gas recovery apparatus as described.   The suction auxiliary part which is installed in the said production well, and sucks the said mixed fluid from this production well toward the said separation apparatus into the said suction pipe further, The one of Claim 1 to 5 characterized by the above-mentioned. The gas recovery device according to one item. The suction auxiliary portion is inserted into the suction pipe and extends in a rod shape centered on the axis, and is provided to protrude from the outer peripheral surface of the main body, and is formed in a spiral shape toward the axis. An auger having a wing portion,
A drive unit that rotatably supports the main body around the axis;
The gas recovery device according to claim 6, further comprising: The suction auxiliary part is an ejection pipe inserted into the production well;
A circulation pipe connected to the first recovery unit and through which the methane gas flows;
An ejection device that connects the suction pipe and the flow pipe, and blows the methane gas into the production well through the ejection pipe;
The gas recovery device according to claim 6, further comprising: A gas recovery method for recovering the methane gas by separating the water and the sand from the mixed fluid using the gas recovery device according to any one of claims 1 to 8.
A first introduction step of introducing the mixed fluid into the first gas separation unit;
A first separation step of separating the methane gas by a specific gravity difference from the mixed fluid in the first gas separation unit;
A recovery step of recovering the methane gas separated in the first gas separation unit through the first recovery unit;
A second introduction step of introducing the mixed fluid from the first gas separation unit into the solid separation unit through the connection unit;
A second separation step of settling and separating the sand with the tubular member in the solid separation portion;
A gas recovery method comprising: A first flushing step for flowing water into the tubular member in the solid separation portion toward the connection portion; a second flushing step for flowing out the water after flowing the water toward the connection portion;
The gas recovery method according to claim 9, further comprising:

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