WO2022222333A1 - Sorting and separating device and method for natural gas hydrate underground cyclone - Google Patents

Abstract

A sorting and separating device for a natural gas hydrate underground cyclone. The device is composed of an outer pipe (1) and an inner pipe (2), wherein the inner pipe (2) is mounted in the outer pipe (1) by means of fixing plates (3) arranged at intervals, and a cyclone separator is mounted on an inner wall of the inner pipe (2). Also disclosed is a method for sorting and separating a natural gas hydrate underground cyclone by using the above device.

Description

Downhole cyclone sorting and separation device and method for natural gas hydrate technical field

The present disclosure belongs to the field of natural gas hydrate exploitation, relates to a natural gas hydrate downhole cyclone sorting and separation device, and also relates to a natural gas hydrate downhole cyclone sorting and separation method using the device.

Background technique

Clean natural gas hydrate, like ice and snow, can be directly ignited, commonly known as "combustible ice". Natural gas hydrate (combustible ice) is a white ice-snow-like crystal compound formed from natural gas (the main component methane) and water under low temperature and high pressure conditions. It has the characteristics of large reserves, wide distribution, shallow burial, high energy density and clean combustion. . Widely distributed in the sediments of the seafloor and permafrost areas on the continental margin, it is known as one of the most promising new energy sources in the future. Natural gas hydrates are widely distributed in sea areas and have a large amount of resources. They are the replacement energy for conventional oil and natural gas in the future. At present, many countries in the world are conducting scientific surveys and trial production.

The mainstream mining methods of natural gas hydrate are: pressure reduction method, heat shock method, CO ₂ /N ₂ replacement method, inhibitor injection method, solid-state fluidization method and the combined mining method that combines the above methods. Among these methods, the pressure reduction method has the lowest technical difficulty and cost, followed by the solid-state fluidization method. The other methods have relatively high mining costs, high equipment requirements, and harsh construction conditions. In 2017, the first and second rounds of depressurization were carried out on the seabed of Shenhu waters in the South China Sea with a water depth of 1266m and 1225m, respectively, and breakthroughs were made, but they still faced the risk of damaging the environment and engineering geology. In the same year, CNOOC successfully carried out the world's first successful solid-state fluidized test production of marine shallow non-diagenetic gas hydrate in Liwan, northern South China Sea. A breakthrough was made in natural gas hydrate production, and the environmental and Elimination of engineering geological risks.

There are many patent documents on the exploitation of natural gas hydrates:

As described in CN112081559A, a device and method for exploiting natural gas hydrate by means of depressurization and double-pipe injection of modified fluid, which utilizes the inner pipe string to depressurize and extract the natural gas hydrate in the reservoir, and utilizes the bottom of the outer wellbore pipe string to arrange The sensor is suitable for the storage conditions, improving the permeability of the reservoir, ensuring smooth fluid circulation channels and smooth depressurized gas production. However, since the depressurization method is a weakened passive mining method, its disadvantage is that the mining of natural gas is very slow and has certain limitations, and it cannot realize the separation and backfilling of the sediment mixed in the natural gas hydrate slurry, which increases the cost of natural gas hydrate mining. At the same time, if the sediment is not separated and discharged back to the seabed in time, the safety of the mining process cannot be guaranteed.

A natural gas hydrate heat shock reaction device as described in CN104196510A, which can hydrate natural gas by arranging a nano-aluminum powder conveying pipeline and a gas collection pipeline in an external conduit, and igniting explosives at the front end of the nano-aluminum powder conveying pipeline. The material extraction process is more flexible and the extraction efficiency of each shaft is improved. However, the heat shock method will cause a lot of heat loss and low heat utilization rate during the implementation process, resulting in a lot of energy waste. At the same time, since the sediment cannot be backfilled in time during the mining process, the safety and reliability of the mining process cannot be guaranteed. .

Therefore, in view of the above-mentioned defects of the prior art, there is an urgent need in the art to develop a natural gas hydrate downhole cyclone sorting and separation device and method that can overcome the above-mentioned defects of the prior art.

SUMMARY OF THE INVENTION

The present disclosure provides a novel downhole cyclone sorting and separation device and method for natural gas hydrate, thereby overcoming the defects existing in the prior art.

The purpose of the present disclosure is to: in view of the deficiencies of the prior art, to provide a method that can separate the natural gas hydrate from the sediment in situ, and discharge the sediment back to the seabed, so as to ensure safety and reliability and reduce the cost of exploitation. A device and method for downhole cyclone sorting and separation of natural gas hydrate.

In one aspect, the present disclosure provides a natural gas hydrate downhole cyclone sorting and separation device, which is composed of an outer tube and an inner tube, wherein an inner tube is installed in the outer tube through fixed plates arranged at intervals, and an inner tube is installed on the inner wall of the inner tube There is a cyclone separator.

In a preferred embodiment, the cyclone separator is composed of a cyclone cylinder, an upper support plate and a lower support plate, and the upper support plate and the lower support plate are fixed in the inner tube in an upper and lower spaced shape, and the upper support plate and the lower support plate are fixed. A swirl cylinder is fixed between the support plates.

In another preferred embodiment, the swirl cylinder is an inverted conical cylinder, and the diameter of its upper port is 150-500 mm; an overflow pipe is installed in the center of the upper support plate corresponding to the upper port of the swirl cylinder, The bottom end of the overflow pipe extends into the cyclone.

In another preferred embodiment, a swirl groove is arranged on the lower surface of the upper support plate between the upper port of the swirl cylinder and the overflow pipe, and a diversion groove is symmetrically arranged on the swirl groove. The cylinder is communicated with the annular space between the swirl cylinder and the inner pipe through the swirl groove and the guide groove.

In another preferred embodiment, the guide grooves are arranged tangentially on the swirl groove, and the number of guide grooves is 2-10.

In another preferred embodiment, the lower support plate is provided with a cross-shaped sand discharge hole communicating with the swirl cylinder, and the end of the sand discharge hole passes through the inner pipe, the fixing plate, the outer pipe and the outside of the outer pipe Connected.

In another preferred embodiment, circulation holes are evenly distributed on the lower support plate between the sand discharge holes, and the circulation holes communicate with the annular space between the swirl cylinder and the inner pipe.

In another preferred embodiment, a sealing blocking plate is arranged between the bottom port of the outer pipe and the bottom port of the inner pipe, and nozzles are evenly distributed on the sealing blocking plate.

In another preferred embodiment, a cyclone separator is welded on the inner wall of the inner tube.

In another aspect, the present disclosure provides a method for downhole cyclone sorting and separation of natural gas hydrate using the above device, the method comprising the following steps:

1) Assemble the device, tubing and screw drilling tools into a tool string, and then run it into the well;

2) After running into the well, the drilling fluid is injected through the tubing under the pressure of 14-18MPa; the injected drilling fluid is ejected from the nozzle through the annulus between the outer tube and the inner tube to form a jet, thereby hydrating the natural gas on the seabed debris and sand blasting;

3) After the ejected drilling fluid sprays and breaks the natural gas hydrate and sediment on the seabed, the drilling fluid mixed with natural gas hydrate and sediment enters the device through the lower port of the inner pipe;

4) The mixed slurry formed by drilling fluid, natural gas hydrate and sediment entering through the lower port of the inner pipe enters the annulus between the cyclone cylinder and the inner pipe through the flow hole, and then passes through the diversion groove and the cyclone concave. The groove enters the swirl cylinder;

5) Since the diversion groove is arranged tangentially on the swirl groove, the mixed slurry entering tangentially from the diversion groove forms a swirling flow along the inner wall of the swirl cylinder to perform centrifugal separation of the mixed slurry; and

6) During the process of the mixed slurry forming a swirling flow along the inner wall of the swirl cylinder, the sediment with large density and particle size is thrown to the side wall due to the large centrifugal force, and the natural gas hydrate is close to the center due to the small density and centrifugal force, that is, the density Solid materials with small specific gravity and natural gas are returned to the surface with the drilling fluid through the overflow pipe for further processing; at the same time, in the process of cyclone separation, the natural gas hydrate is broken again under the action of the fluid shear force, and the Washing to separate the sediment and gas hydrate attached to the surface of the gas hydrate again; after separation, the sediment with a large density gradually sinks into the sand discharge hole and is discharged to the outside of the device, backfilled to the seabed, through which The self-revolution coupling effect of the cyclone realizes the weakened cyclone gel breaking and separation process of natural gas hydrate.

Beneficial effects:

The cyclone sorting and separation device can realize the sorting of natural gas hydrate and silt particles through the inner pipe, thereby enhancing the separation effect of the cyclone cylinder, and by in-situ separation of natural gas hydrate and silt, it can obtain more pure Natural gas hydrate can effectively improve the mining efficiency and greatly reduce the cost of mining; the sediment can be re-discharged to the seabed through the sand discharge hole, so that the sediment can be backfilled, thereby ensuring the safety and reliability of mining, and solving the problem of existing The mining method has the problems of high mining cost, poor safety and reliability, and is especially suitable for the mining and use of natural gas hydrate.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present disclosure, and they only constitute a part of the present specification to further explain the present disclosure, and do not constitute a limitation to the present disclosure.

FIG. 1 is a schematic structural diagram of a natural gas hydrate downhole cyclone sorting and separation device according to a preferred embodiment of the present disclosure.

FIG. 2 is a schematic view of the structure in the direction A-A in FIG. 1 .

FIG. 3 is a schematic diagram of the structure in the direction B-B in FIG. 1 .

4 is a schematic cross-sectional structural diagram of a lower support plate according to a preferred embodiment of the present disclosure.

5 is a schematic bottom view of a natural gas hydrate downhole cyclone sorting and separation device according to a preferred embodiment of the present disclosure.

Figure 6 is a graph of diameter versus throughput for a cyclone separator of the present invention.

FIG. 7 is the appearance micrographs of the experimental group at 2 mm and 10 mm respectively in the examples of the present application.

FIG. 8 is a particle size distribution diagram of the experimental group in the examples of the present application.

FIG. 9 is a schematic structural diagram of a simulated separation experimental device according to a preferred embodiment of the present disclosure.

FIG. 10 is a statistical diagram of the separation efficiency of polypropylene powder under different flow rates in the examples of the present application.

FIG. 11 is a statistical diagram of the separation efficiency of quartz sand under different flow rates in the examples of the present application.

In the figure, each reference sign is as follows: 1, outer tube, 2, inner tube, 3, fixed plate, 4, swirl cylinder, 5, upper support plate, 6, lower support plate, 7, overflow pipe, 8 , diversion groove, 9, sand discharge hole, 10, flow hole, 11, nozzle, 12, swirl groove, 13, sealing blocking plate, 14, screw pump, 15, water storage tank, 16, return valve, 17 , flowmeter, 18, pressure gauge, 19, bypass valve, 20, main valve, 21, feeder, 22, discharge valve, 23, cyclone sorting separator, 24, accumulator, 25, water recovery and storage Tank, 26, make-up valve.

Detailed ways

In a first aspect of the present disclosure, a natural gas hydrate downhole cyclone sorting and separation device is provided, the device is composed of an outer tube and an inner tube, wherein the inner tube is installed in the outer tube through fixed plates arranged at intervals, and the inner tube is installed with an inner tube. A cyclone separator is welded on the inner wall.

In the present disclosure, the cyclone separator is composed of a cyclone cylinder, an upper support plate and a lower support plate, the upper support plate and the lower support plate are fixed in the upper and lower spaced shapes in the inner tube, and the upper support plate and the lower support plate are fixed between the upper and lower support plates. Equipped with whirlpool.

In the present disclosure, the swirl cylinder is an inverted conical cylinder, and the diameter of its upper port is 150-500 mm; an overflow pipe is threadedly installed at the center of the upper support plate corresponding to the upper port of the swirl cylinder, and the bottom of the overflow pipe is threaded. The tip extends into the swirl cylinder.

In the present disclosure, a swirl groove is provided on the lower surface of the upper support plate between the upper port of the swirl cylinder and the overflow pipe, the swirl groove is symmetrically provided with a diversion groove, and the swirl cylinder passes through the swirl groove and The guide groove is communicated with the annular space between the swirl cylinder and the inner pipe.

In the present disclosure, the diversion grooves are arranged tangentially on the swirl groove, and the number of the diversion grooves is 2-10.

In the present disclosure, the lower support plate is provided with a cross-shaped sand discharge hole communicating with the swirl cylinder, and the end of the sand discharge hole communicates with the outside of the outer pipe through the inner pipe, the fixing plate and the outer pipe.

In the present disclosure, circulation holes are evenly distributed on the lower support plate between the sand discharge holes, and the circulation holes communicate with the annular space between the swirl cylinder and the inner pipe.

In the present disclosure, a sealing blocking plate is arranged between the bottom port of the outer pipe and the bottom port of the inner pipe, and nozzles are evenly distributed on the sealing blocking plate.

In an exemplary embodiment, the natural gas hydrate downhole cyclone sorting and separation device of the present disclosure is composed of an outer pipe 1 and an inner pipe 2, and a fixed plate 3 is welded on the inner wall of the outer pipe 1 in a spaced shape. An inner pipe 2 is welded, and the inner pipe 2 is sleeved and connected with the outer pipe 1. During operation, drilling fluid is introduced into the annulus between the outer pipe 1 and the inner pipe 2, and the cemented slurry of natural gas hydrate is recovered through the inner pipe 2. The function of the fixing plate 3 is to isolate the inner tube 2 and the outer tube 1 to avoid friction between the inner tube 2 and the outer tube 1, thereby preventing the inner tube 2 and the outer tube 1 from being damaged; the inner tube 2 and the outer tube 1 are respectively segmented The way of welding is connected as a whole to facilitate the welding of the fixing plate 3 and the outer tube 1 and the inner tube 2 during assembly; a sealing blocking plate 13 is provided between the bottom port of the outer tube 1 and the bottom port of the inner tube 2, and the sealing blocking plate 13 There are nozzles 11 evenly distributed on the top, and the function of the sealing blocking plate 13 is to cooperate with the nozzle 11 to reduce the flow area of the drilling fluid, and when the pressure remains unchanged, increase the flow rate of the drilling fluid, so that the drilling fluid is ejected from the nozzle 11 at a high speed to form a jet flow, thereby The natural gas hydrate ore bed is impacted by the drilling fluid jet, and the natural gas hydrate and sediment are broken to form a mixed slurry of drilling fluid, natural gas hydrate and sediment; the inner wall of the inner pipe 2 is welded with a cyclone separator. It consists of a swirl cylinder 4, an upper support plate 5 and a lower support plate 6. The inner tube 2 is fixed with an upper support plate 5 and a lower support plate 6 in an up and down interval, and the upper support plate 5 and the lower support plate 6 are respectively connected with the inner The pipe 2 is welded so that the cyclone separator is fixed on the inner wall of the inner pipe 2; the cyclone cylinder 4 is fixed between the upper support plate 5 and the lower support plate 6, and the cyclone cylinder 4 is an inverted conical cylinder, which The diameter of the upper port is 150-500mm, and the separation accuracy and production capacity of the cyclone separator are closely related to its nominal diameter. For gas hydrate collection, through simulation research, when the diameter of the upper port of the cyclone 4 is 150-500mm, its The separation effect and production capacity are the best (see Figure 6); the center of the upper support plate 5 corresponding to the upper port of the swirl cylinder 4 is threadedly installed with an overflow pipe 7, and the bottom end of the overflow pipe 7 extends to the swirl cylinder 4 Inside; the lower surface of the upper support plate 5 between the upper port of the swirl cylinder 4 and the overflow pipe 7 is provided with a swirl groove 12, and the swirl groove 12 is symmetrically provided with a diversion groove 8, and the diversion groove 8 is in the swirl groove. The flow groove 12 is arranged tangentially, the number of the guide grooves 8 is 2-10, and the swirl cylinder 4 passes through the annular space between the swirl groove 12 and the guide groove 8 and the swirl cylinder 4 and the inner pipe 2 The function of the diversion groove 8 is to cooperate with the swirl groove 12 to make the mixed slurry communicate with the diversion groove 8 and The swirl groove 12 enters the swirl cylinder 4, thereby guiding the mixed slurry into the swirl cylinder 4, and the mixed slurry enters the swirl cylinder 4 through the diversion groove 8 and the swirl groove 12, and passes through the swirl flow. The guide grooves 8 arranged tangentially on the grooves 12 guide the mixed slurry to enter along the tangential direction of the swirl grooves 12, so that the mixed slurry has a tangential velocity relative to the swirl grooves 12, so that the mixed slurry has a tangential velocity relative to the swirl grooves 12. After entering the swirl cylinder 4, a swirl can be formed, thereby hydrating the natural gas in the mixed slurry. The sand and sediment are separated; the lower support plate 6 is provided with a cross-shaped sand discharge hole 9 that communicates with the cyclone 4, and the end of the sand discharge hole 9 passes through the inner pipe 2, the fixed plate 3 and the outer pipe 1 and 1. The outer pipe 1 is connected to the outside, and the function of the sand discharge hole 9 is to discharge the sediment with a larger specific gravity through the sand discharge hole 9 during the cyclone separation process, so that the sediment is backfilled to the seabed, and the seabed is not easy to be excavated during the mining process. The lower support plate 6 between the sand discharge holes 9 is evenly distributed with circulation holes 10, and the circulation holes 10 and the ring between the swirl cylinder 4 and the inner pipe 2 Empty communication, so that the mixed slurry can enter the cyclone 4 through the circulation hole 10, the annulus between the cyclone 4 and the inner pipe 2, the diversion groove 8 and the cyclone groove 12 in turn; During the process of the annular space between the swirl cylinder 4 and the inner tube 2, the diversion groove 8 and the swirl groove 12 entering the swirl cylinder 4, the diversion groove 8 and the swirl groove 12 can achieve different densities and particle sizes. The sorting of materials, that is, when the material density and particle size are different, the buoyancy of the material relative to the mixed slurry is different, and when the buoyancy of the material is different, the moving speed of the material in the mixed slurry is different, thereby realizing the different density and particle size materials. Sorting can effectively improve the separation efficiency of natural gas hydrate.

In a second aspect of the present disclosure, a method for downhole cyclone sorting and separation of natural gas hydrate using the above device is provided, the method comprising the following steps:

1) First, assemble the device, tubing and screw drilling tools into a tool string, and then run it into the well;

2) After running into the well, the drilling fluid is injected through the tubing under the pressure of 14-18MPa; the injected drilling fluid is sprayed out by the nozzle through the annulus between the outer tube and the inner tube, so that the natural gas hydrate on the seabed is ejected. and sand blasting;

3) After the drilling fluid ejected at high pressure and high speed breaks the natural gas hydrate and sediment on the seabed, the drilling fluid mixed with natural gas hydrate and sediment enters the device through the lower port of the inner pipe;

4) The mixed slurry formed by drilling fluid, natural gas hydrate and sediment entering through the lower port of the inner pipe enters the annulus between the cyclone cylinder and the inner pipe through the flow hole, and then passes through the diversion groove and the cyclone concave. The groove enters the swirl cylinder;

5) Since the diversion groove is arranged tangentially on the swirl groove, the mixed slurry entering tangentially from the diversion groove forms a swirling flow along the inner wall of the swirl cylinder to perform centrifugal separation of the mixed slurry; and

6) During the process of the mixed slurry forming a swirl along the inner wall of the swirl cylinder, the sediment with large density and particle size is thrown to the side wall due to the relatively larger centrifugal force, and the natural gas hydrate is closer to the center due to the relatively smaller density and centrifugal force. , that is, the solid materials and natural gas with small density and specific gravity are returned to the surface with the drilling fluid through the overflow pipe for further processing; at the same time, in the process of cyclone separation, the natural gas hydrate is broken again under the action of fluid shear force. , and wash it to separate the sediment and gas hydrate attached to the surface of the natural gas hydrate again; after separation, the sediment with higher density and specific gravity gradually sinks into the sand discharge hole and is discharged to the outside of the device, and is backfilled to The seabed, through the self-revolution coupling of the cyclone separator, the weakened cyclone gel breaking and separation process of natural gas hydrate is realized.

In an exemplary embodiment, the method for downhole cyclone sorting and separation of natural gas hydrate using the above device of the present disclosure is as follows:

First, the upper end of the device is assembled with tubing and screw drilling tools to form a tool string, and then run into the well;

After running into the well, the drilling fluid is injected through the oil pipe under the pressure of 14-18MPa; the injected drilling fluid is ejected by the nozzle through the annulus between the outer pipe 1 and the inner pipe 2 to form a jet, so that the natural gas hydrate on the seabed is ejected. and sediment jetting and crushing, so that the drilling fluid, natural gas hydrate and sediment form a mixed slurry that is easy to flow, thus making the natural gas hydrate and sediment have fluidity and facilitating the separation of natural gas hydrate and sediment; high-pressure high-speed ejection After the drilling fluid breaks the natural gas hydrate and sediment on the seabed, the drilling fluid mixed with the natural gas hydrate and the sediment enters the device through the lower port of the inner pipe 2, so that the natural gas hydrate and sediment are carried out through the device. In-situ separation to obtain relatively pure natural gas hydrate, and backfill the sediment to the seabed to avoid collapse during mining and ensure safety and reliability;

The mixed slurry formed by drilling fluid, natural gas hydrate and sediment entered through the lower port of the inner pipe 2 enters the annular space between the cyclone 4 and the inner pipe 2 through the flow hole, and is then passed through the diversion groove 8 and the cyclone. The flow groove 12 enters the swirl cylinder 4; since the diversion groove 8 is arranged tangentially on the swirl groove 12, the mixed slurry entering tangentially from the diversion groove 8 forms a swirl in the swirl cylinder 4 along its inner wall. In the process of the mixed slurry forming a swirling flow along the inner wall of the cyclone cylinder 4, the sediment with large density and particle size is thrown to the side wall due to the relatively larger centrifugal force, and the natural gas hydrate Because the density and centrifugal force are relatively smaller and close to the center, that is, the solid materials and natural gas with smaller density and specific gravity are returned to the surface with the drilling fluid through the overflow pipe 7 for further processing; Under the action, the natural gas hydrate is broken again, and during the swirling process, the drilling fluid repeatedly washes and washes the natural gas hydrate, and the sediment and the natural gas hydrate attached to the surface of the natural gas hydrate are separated again. The flow groove 8 is arranged tangentially on the swirl groove 12, so that the diversion groove 8 can guide the mixed slurry into the swirl cylinder 4 at a small angle (axial angle), thereby enabling the mixed slurry to enter the swirl cylinder 4. 4, it stays for a long time to strengthen the process of re-breaking and re-separation of natural gas hydrate under the action of fluid shear; Outside the separation device, it is backfilled to the seabed, thereby realizing the weakened cyclone gel breaking and separation process of natural gas hydrate through the self-revolution coupling of the cyclone separator.

See attached drawings below.

FIG. 1 is a schematic structural diagram of a natural gas hydrate downhole cyclone sorting and separation device according to a preferred embodiment of the present disclosure. As shown in FIG. 1 , the device is composed of an outer tube 1 and an inner tube 2. A fixed plate 3 is welded on the inner wall of the outer tube 1 in a spaced shape, and an inner tube 2 is welded on the fixed plate 3. The inner tube 2 and the outer tube 1 The cyclone separator is welded on the inner wall of the inner pipe 2. The cyclone separator is composed of a cyclone cylinder 4, an upper support plate 5 and a lower support plate 6. The inner pipe 2 is fixed with an upper support in an upper and lower interval. Plate 5 and lower support plate 6, the upper support plate 5 and the lower support plate 6 are respectively welded with the inner tube 2, so that the cyclone separator is fixed on the inner wall of the inner tube 2; between the upper support plate 5 and the lower support plate 6 The swirl cylinder 4 is fixedly installed, and the swirl cylinder 4 is an inverted conical cylinder; the center part of the upper support plate 5 corresponding to the upper port of the swirl cylinder 4 is threadedly installed with an overflow pipe 7, and the bottom end of the overflow pipe 7 is threaded. It extends into the swirl cylinder 4; the lower surface of the upper support plate 5 between the upper port of the swirl cylinder 4 and the overflow pipe 7 is provided with a swirl groove 12; 4 connected sand discharge holes 9, the ends of the sand discharge holes 9 communicate with the outside of the outer pipe 1 through the inner pipe 2, the fixing plate 3 and the outer pipe 1; a bottom port of the outer pipe 1 and the bottom port of the inner pipe 2 are provided with The sealing and blocking plate is provided with nozzles 11 evenly.

FIG. 2 is a schematic view of the structure in the direction A-A in FIG. 1 . As shown in Figure 2, the device is composed of an outer tube 1 and an inner tube 2. The inner wall of the outer tube 1 is welded with a fixed plate 3 in an interval shape; the inner wall of the inner tube 2 is welded with a cyclone separator. It consists of a swirl cylinder, an upper support plate 5 and a lower support plate; the center part of the upper support plate 5 corresponding to the upper port of the swirl cylinder is threadedly installed with an overflow pipe 7; The lower surface of the upper support plate 5 is provided with a swirl groove 12 , the swirl groove 12 is symmetrically provided with a guide groove 8 , and the guide groove 8 is arranged tangentially on the swirl groove 12 .

FIG. 3 is a schematic diagram of the structure in the direction B-B in FIG. 1 . As shown in Figure 3, the device is composed of an outer tube 1 and an inner tube 2. The inner wall of the outer tube 1 is welded with a fixed plate 3 in an interval shape; the inner wall of the inner tube 2 is welded with a cyclone separator. It consists of a swirl cylinder, an upper support plate and a lower support plate 6; the lower support plate 6 is provided with a cross-shaped sand discharge hole 9 that communicates with the swirl cylinder, and the end of the sand discharge hole 9 passes through the inner pipe 2 and is fixed. The plate 3 and the outer tube 1 communicate with the outside of the outer tube 1 ; the lower support plate 6 between the sand discharge holes 9 is evenly distributed with flow holes 10 , and the flow holes 10 communicate with the annular space between the swirl cylinder and the inner tube 2 .

4 is a schematic cross-sectional structural diagram of a lower support plate according to a preferred embodiment of the present disclosure. As shown in FIG. 4 , the lower support plate 6 is provided with sand discharge holes 9 communicating with the swirl cylinder in a cross shape; circulation holes 10 are evenly distributed on the lower support plate 6 between the sand discharge holes 9 .

5 is a schematic bottom view of a natural gas hydrate downhole cyclone sorting and separation device according to a preferred embodiment of the present disclosure. As shown in Figure 5, the device is composed of an outer tube 1 and an inner tube 2; a cyclone separator is welded on the inner wall of the inner tube 2, and the cyclone separator is composed of a cyclone cylinder, an upper support plate and a lower support plate 6, An upper support plate and a lower support plate 6 are fixed in the inner tube 2 in an upper and lower interval; a sealing blocking plate 13 is arranged between the bottom port of the outer tube 1 and the bottom port of the inner tube 2, and nozzles 11 are evenly distributed on the sealing blocking plate 13 ; The lower support plate 6 is provided with a cross-shaped sand discharge hole communicating with the swirl cylinder; the lower support plate 6 between the sand discharge holes is evenly distributed with flow holes 10 .

FIG. 9 is a schematic structural diagram of a simulated separation experimental device according to a preferred embodiment of the present disclosure. As shown in FIG. 9 , the device consists of a screw pump 14, a cyclone sorting separator 23, a material accumulator 24 and a feeder 21. The inlet of the screw pump 14 is connected to a water storage tank 15, and the outlet of the screw pump 14 is connected to the main pipe. A cyclone sorting separator 23 is connected, the underflow port of the cyclone sorting separator 23 is connected with a storage device 24, and the overflow port of the cyclone sorting separator 23 is connected with a water recovery storage tank 25; a flow meter is provided on the connecting main pipe 17. The connecting main pipe on one side of the flow meter 17 is connected to the top of the water storage tank 15 through the return valve 16; the connecting main pipe on the other side of the flow meter 17 is provided with a pressure gauge 18; A feeder 21 is arranged on the connecting main pipe between the two parts, the bottom outlet of the feeder 21 is connected with the connecting main pipe through the discharge valve 22, the upper inlet of the feeder 21 is connected with the connecting main pipe through the bypass valve 19; the bypass valve 19 is connected with the discharge A main valve 20 is provided on the main connecting pipe between the valves 22 ; a water replenishing valve 26 is connected above the water storage tank 15 .

Example

The present invention is further described below in conjunction with specific embodiments. However, it should be understood that these examples are only intended to illustrate the present invention and not to limit the scope of the present invention. In the following examples, the test methods without specific conditions are usually in accordance with conventional conditions, or in accordance with the conditions suggested by the manufacturer. All percentages and parts are by weight unless otherwise indicated.

Example 1:

In order to verify the separation effect of natural gas hydrate, the inventors simulated the actual working conditions in the production process and carried out the following experiments on the separation of natural gas hydrate:

1. Materials and experimental conditions

According to the physical properties of natural gas hydrate obtained by CNOOC in the Liwan water depth of 1310m and the burial depth of natural gas hydrate ore body at 117-196m in the northern South China Sea, the experimental materials selected quartz sand and polypropylene powder (PP) as the deep water and shallow natural gas hydrate in the South China Sea. It is a substitute for mud sand and natural gas hydrate in storage; the density of quartz sand selected in the experiment is 2510kg/m ³ and the median particle size is 70.4 microns; the density of PP is 910kg/m ³ and the median particle size is 47.6 microns.

Four groups of natural gas hydrate simulant materials with different cementing strengths are made by different proportions of quartz sand and PP. And use KQ-3 particle strength tester (purchased from: Yunnan Chemical Industry Research Institute) to test the compressive strength of the material, it can be seen that the higher the content of quartz sand, the higher the compressive strength and the better the degree of cementation; at the same time, Particle size distribution measurements were performed using a Malvern Laser Particle Sizer (available from: Malvern PANalytical) (see Table 1 below, and Figures 7 and 8).

Table 1 4 experimental groups with different bond strengths

	A	B	C	D
PP/g	0.968	2.078	3.362	4.866
Quartz sand/g	24.032	22.923	21.638	20.134
bond strength	0.184	0.135	0.112	0.098

2. Experimental setup and procedure

In order to study the separation effect of the cyclone sorting separation device on gas hydrate simulants with different cementation strengths at different flow rates, a simulated separation experimental device was designed:

As shown in FIG. 9 , the device consists of a screw pump 14, a cyclone sorting separator 23, a material accumulator 24 and a feeder 21. The inlet of the screw pump 14 is connected to a water storage tank 15, and the outlet of the screw pump 14 is connected to the main pipe. A cyclone sorting separator 23 is connected, the underflow port of the cyclone sorting separator 23 is connected with a storage device 24, and the overflow port of the cyclone sorting separator 23 is connected with a water recovery storage tank 25; a flow meter is provided on the connecting main pipe 17. The connecting main pipe on one side of the flow meter 17 is connected to the top of the water storage tank 15 through the return valve 16; the connecting main pipe on the other side of the flow meter 17 is provided with a pressure gauge 18; A feeder 21 is arranged on the connecting main pipe between the two parts, the bottom outlet of the feeder 21 is connected with the connecting main pipe through the discharge valve 22, the upper inlet of the feeder 21 is connected with the connecting main pipe through the bypass valve 19; the bypass valve 19 is connected with the discharge A main valve 20 is provided on the main connecting pipe between the valves 22 ; a water replenishing valve 26 is connected above the water storage tank 15 .

This experiment is a continuous experiment. The underflow port of the cyclone sorting separator 23 is connected to the accumulator 24 for material recovery after the cyclone gel breaking separation, and the overflow port of the cyclone sorting separator 23 is discharged to the outside for purification and recycling. , add the material into the feeder 21, after the feeding is completed, the main valve 20 is fully opened, the bypass valve 19 and the unloading valve 22 are kept closed, the screw pump 14 is started, and the flow rate of the screw pump 14 is adjusted through the return valve 16; the simulation separation experimental device Start feeding after 10 minutes of stable operation: open the unloading valve 22 and the bypass valve 19 in turn, and slowly adjust the main valve 20 to make the water flow into the feeder 21; after 5 minutes of stable operation, slowly close the main valve 20, Make the water completely flow into the feeder 21 to wash it, so that the material in the feeder 21 completely enters the cyclone sorting separator 23 for cyclone gel breaking separation, and a part of the separated materials and water pass through the cyclone sorting separator 23 The underflow port of the cyclone enters the storage tank 24, and another part of the material and water enters the water recovery storage tank 25 through the overflow port of the cyclone sorting separator 23. After separation and running for 10 minutes, the screw pump 14 is shut down.

The material captured in the accumulator 24 is firstly filtered by a vacuum suction filter, which adopts Shanghai Xinya 50*0.22 water-based microporous membrane; after suction filtration and drying, it is placed in an oven at 100 °C for 8 hours. It was moved into a desiccator to dry for 30 minutes, taken out, and weighed using an electronic analytical balance with a measurement accuracy of 0.0001 g, and the separation efficiency was calculated.

3. Experimental results and analysis

When the flow rate is 0.8m ³ /h and 1.2m ³ /h, the separation effect of polypropylene powder is higher than 99%, and the greater the inlet flow rate, the greater the inlet tangential force, and the separation effect slightly increases; at the same time, for For the four bonding strengths, the separation effect is higher than 99%, and the lower the bonding strength, the better the separation effect (see Figure 10).

For samples with different flow rates and cementation strengths, the separation effect of quartz sand was higher than 93% (see Figure 11).

It can be seen from the above experiments that the cyclone sorting and separation device of the present invention can well realize the separation of natural gas hydrate and sediment, is conducive to the purification and recovery of natural gas hydrate, and can effectively solve the sand blocking caused by seabed mud and sand. Or mining risks such as seabed collapse can effectively improve safety and reliability.

The cyclone sorting and separation device of the present invention can realize the sorting of natural gas hydrate and silt particles, and can separate natural gas hydrate and silt in situ, so that purer natural gas hydrate can be obtained, and the exploitation efficiency can be effectively improved. The mining cost is greatly reduced; the sediment can be re-discharged to the seabed through the sand discharge hole 9, so that the sediment can be backfilled, thereby ensuring the safety and reliability of mining; it solves the problem of the high mining cost, safety and reliability of the existing mining methods. The problem of poor reliability is especially suitable for the exploitation and use of natural gas hydrate.

The above listed embodiments are only preferred embodiments of the present disclosure, and are not intended to limit the implementation scope of the present disclosure. That is, all equivalent changes and modifications made according to the content of the patent scope of the present application shall fall within the technical scope of the present disclosure.

All documents mentioned in this disclosure are incorporated by reference in this application as if each document were individually incorporated by reference. In addition, it should be understood that after reading the above teaching content of the present disclosure, those skilled in the art can make various changes or modifications to the present disclosure, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (10)

1. A natural gas hydrate downhole cyclone sorting and separation device, the device is composed of an outer pipe (1) and an inner pipe (2), and is characterized in that: an inner pipe (1) is installed with an inner pipe (3) through a fixed plate (3) arranged at intervals. The pipe (2) is provided with a cyclone separator on the inner wall of the inner pipe (2).
2. The device according to claim 1, characterized in that: the cyclone separator is composed of a cyclone cylinder (4), an upper support plate (5) and a lower support plate (6), and the inner tube (2) has an upper and lower shape. The upper support plate (5) and the lower support plate (6) are fixedly arranged at intervals, and the swirl cylinder (4) is fixedly arranged between the upper support plate (5) and the lower support plate (6).
3. The device according to claim 2, characterized in that: the swirl cylinder (4) is an inverted conical cylinder, and the diameter of the upper port thereof is 150-500 mm; the upper port of the swirl cylinder (4) corresponds to the upper An overflow pipe (7) is installed at the center of the support plate (5), and the bottom end of the overflow pipe (7) extends into the swirl cylinder (4).
4. The device according to claim 3, characterized in that a swirl groove (12) is provided on the lower surface of the upper support plate (5) between the upper port of the swirl cylinder (4) and the overflow pipe (7). ), the swirl groove (12) is symmetrically provided with a diversion groove (8), and the swirl cylinder (4) passes through the swirl groove (12) and the diversion groove (8) and the swirl cylinder (4) and the inner Annular communication between the tubes (2).
5. The device according to claim 4, characterized in that: the diversion grooves (8) are arranged tangentially on the swirl groove (12), and the number of the diversion grooves (8) is 2-10.
6. The device according to claim 2, characterized in that: the lower support plate (6) is provided with a sand discharge hole (9) communicating with the swirl cylinder (4) in a cross shape. The end head communicates with the outside of the outer pipe (1) through the inner pipe (2), the fixing plate (3) and the outer pipe (1).
7. The device according to claim 6, characterized in that: the lower support plate (6) between the sand discharge holes (9) is uniformly distributed with circulation holes (10), the circulation holes (10) and the swirl cylinder ( 4) and the annular communication between the inner pipe (2).
8. The device according to claim 1, characterized in that: a sealing blocking plate (13) is provided between the bottom port of the outer pipe (1) and the bottom port of the inner pipe (2), and the sealing blocking plate (13) Nozzles (11) are evenly distributed on the top.
9. The device according to claim 1, characterized in that a cyclone separator is welded on the inner wall of the inner pipe (2).
10. A method for downhole cyclone sorting and separation of natural gas hydrate using the device according to any one of claims 1-9, the method comprising the steps of:

    1) Assemble the device, tubing and screw drilling tools into a tool string, and then run it into the well;

    2) After running into the well, the drilling fluid is injected through the tubing under the pressure of 14-18MPa; the injected drilling fluid is ejected from the nozzle through the annulus between the outer tube and the inner tube to form a jet, thereby hydrating the natural gas on the seabed debris and sand blasting;

    3) After the ejected drilling fluid sprays and breaks the natural gas hydrate and sediment on the seabed, the drilling fluid mixed with natural gas hydrate and sediment enters the device through the lower port of the inner pipe;

    4) The mixed slurry formed by drilling fluid, natural gas hydrate and sediment entering through the lower port of the inner pipe enters the annulus between the cyclone cylinder and the inner pipe through the flow hole, and then passes through the diversion groove and the cyclone concave. The groove enters the swirl cylinder;

    5) Since the diversion groove is arranged tangentially on the swirl groove, the mixed slurry entering tangentially from the diversion groove forms a swirling flow along the inner wall of the swirl cylinder to perform centrifugal separation of the mixed slurry; and

    6) During the process of the mixed slurry forming a swirling flow along the inner wall of the swirl cylinder, the sediment with large density and particle size is thrown to the side wall due to the large centrifugal force, and the natural gas hydrate is close to the center due to the small density and centrifugal force, that is, the density Solid materials with small specific gravity and natural gas are returned to the surface with the drilling fluid through the overflow pipe for further processing; at the same time, in the process of cyclone separation, the natural gas hydrate is broken again under the action of the fluid shear force, and the Washing to separate the sediment and gas hydrate attached to the surface of the gas hydrate again; after separation, the sediment with a large density gradually sinks into the sand discharge hole and is discharged to the outside of the device, backfilled to the seabed, through which The self-revolution coupling effect of the cyclone realizes the weakened cyclone gel breaking and separation process of natural gas hydrate.

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