CN106837259B - Device and method for increasing yield of marine shallow natural gas hydrate microtubules - Google Patents

Abstract

The invention discloses a device and a method for increasing the yield of an ocean shallow natural gas hydrate micro-tube. A certain number of micro-pipes are arranged in a hydrate reservoir underground surrounding a shallow ocean natural gas hydrate well, the micro-pipes are high-pressure resistant steel pipes with holes and certain flexibility, and a micro-pipe network which is uniform, has certain intervals and is spatially distributed is formed in the well section of the whole hydrate reservoir, namely, an unblocked fixed production channel is formed. The invention is suitable for various marine natural gas hydrate exploitation methods such as a depressurization method, a heat shock method, a chemical reagent injection method and the like; the method can effectively enlarge the contact area between the production channel and the hydrate reservoir, thereby improving the permeability of the reservoir, improving the heat and mass transfer efficiency and the flow conductivity of the reservoir, and achieving the purposes of improving the exploitation efficiency and realizing the economic and efficient exploitation of the marine shallow natural gas hydrate.

Description

A marine shallow natural gas hydrate microtube stimulation device and method

technical field

The invention relates to the field of commercial exploitation of marine hydrates, in particular to a micro-pipe stimulation device and method for marine shallow natural gas hydrates.

Background technique

Natural gas hydrate refers to a cage-shaped crystal substance formed by natural gas and water at a specific temperature and pressure (low temperature and high pressure). It looks like ice and snow. Because it can be ignited, it is commonly called "combustible ice". Natural Gas Hydrate is a clean and efficient emerging energy with huge reserves. The reserves of total organic carbon in gas hydrates on the earth are about twice the sum of oil, natural gas and coal, and the resources of gas hydrates in marine areas account for 99% of the total resources. With the gradual and in-depth research on the exploitation of marine gas hydrates, commercial exploitation is getting closer and closer to the possibility.

At present, the theoretical methods for exploiting marine gas hydrate mainly include depressurization method, thermal shock method, chemical reagent injection method and CO ₂ replacement method. The heat shock method can make the hydrate decompose faster, but limited by the limited contact area between the production channel and the hydrate reservoir, the hydrate layer can only be heated locally, and the heat utilization efficiency is low; the depressurization method is more economical. However, due to the characteristics of poor permeability, low heat and mass transfer efficiency and low flow conductivity of marine hydrate reservoirs, _{depressurization} production cannot be carried out efficiently and continuously; During the process, chemical reagents and CO ₂ have a slow effect on the natural gas hydrate layer. In order to improve the production efficiency, it is necessary to increase the physical and chemical reaction contact area. Exploitation efficiency is an important factor restricting the commercial exploitation of hydrates, and expanding the contact area between production channels and hydrate reservoirs can effectively improve reservoir permeability, heat and mass transfer efficiency and flow conductivity of reservoirs, and improve the production capacity. Therefore, expanding the contact area between production channels and hydrate reservoirs is a necessary way to achieve economical and efficient production of subsea natural gas hydrates.

Existing patent search found that CN201310488336.2 discloses a natural gas hydrate mining method and device combined with decompression and hydraulic fracturing technology, which improves the permeability of the hydrate reservoir by injecting fracturing fluid into the hydrate reservoir for hydraulic fracturing. Pressure-reducing mining; the invention patent application with the Chinese application number 201510455687.2 proposes a pressure-reducing marine natural gas hydrate mining method and a seabed mining system. By constructing multi-cluster perforated horizontal wells on the seabed, the mining contact area is increased. Depressurization mining of hydrates.

It can be seen that there are two existing methods to expand the contact area between the production channel and the hydrate reservoir, one is hydraulic fracturing of the hydrate reservoir, and the other is to construct a production horizontal well in the hydrate reservoir. On the other hand, the shallow gas hydrate layer on the seabed has experienced less structural movement, low density, and fast deposition rate, and most of them are in the saturated or semi-saturated non-diagenetic stage. The reservoir cementation degree is weak, the sediment particles are loosely arranged, and the strength is low. , clay, silt, and sand-mud mixed layers, mainly cohesive soil and sandy soil; this will cause problems such as easy closure of hydraulic fracturing stimulation cracks and difficult construction of horizontal wells, resulting in the hydration of shallow seabed It is not easy to expand the contact area between production channels and hydrate reservoirs by hydraulic fracturing and building horizontal wells; therefore, there is an urgent need for a method to expand the production channels and hydrate reservoirs in shallow oceans. The production increasing device and method of the contact area.

Contents of the invention

In view of the above problems, the present invention proposes a marine shallow natural gas hydrate micro-pipe stimulation device and method, by arranging a certain number of micro-pipes in the hydrate reservoir around the marine shallow natural gas hydrate underground, the micro-pipes are provided with holes Moreover, the high-pressure steel pipe with certain flexibility forms a micro-pipe network with uniform spacing and spatial distribution in the entire well section of the hydrate reservoir, thereby effectively expanding the contact area between the production channel and the hydrate reservoir, and improving the production efficiency. Efficient, to achieve the purpose of economical and efficient exploitation of marine shallow natural gas hydrate.

A marine shallow natural gas hydrate micro-pipe stimulation device of the present invention is composed of a guide device, a wellhead device, a central pipe string, a cable, a thick-walled conduit, a micro-pipe, and a pilot drill bit.

The guide device includes a central channel, a seat seal mechanism, an inclined hole, an electrochemical cutter, a positioning mechanism, a guide cone and a guide hole; the guide hole is a circular channel with a suitable curvature, and there are six guide holes, six guide holes Symmetrically distributed around the central channel; six electrochemical cutters are arranged, and the six electrochemical cutters are respectively connected to the outlets of the six guide holes for cutting microtubes. The central pipe string is used to connect the central channel of the guiding device, lower the guiding device to the production well, and be used for setting and unsealing the guiding device. The electrical cable is connected to the electrochemical cutter through the center column, the center channel and the inclined hole. The positioning mechanism plays the role of guiding and positioning. The thick-walled catheter is accurately located on the guiding cone surface through the positioning mechanism, and the thick-walled catheter and the guiding cone surface cooperate. The wellhead device is arranged at the wellhead, and the wellhead device provides vertical downward feeding force for the micropipe during the arrangement of the micropipe. The annular gap between the microtube and the thick-walled catheter is smaller than the outer diameter of the microtube, which prevents buckling of the microtube in the channel of the thick-walled catheter and ensures smooth operation of the microtube arrangement. The end port of the micropipe is provided with a pilot drill bit, which is used to squeeze and break the hydrate reservoir when the micropipe is arranged. The micropipe is a high-pressure resistant steel pipe with certain flexibility. There are holes with the same diameter on the outer wall of the micropipe. The diameter range is 15mm-35mm.

A method for increasing production of shallow marine natural gas hydrate described in the present invention comprises the following steps:

1) Construct production wells: Drill vertical boreholes in shallow marine natural gas hydrate reservoirs, pass through the overburden, and after drilling near the top boundary of hydrate reservoirs, stop drilling and run in casings for cementing, and then Drill through the gas hydrate reservoir to the top boundary of the gas hydrate lower overburden, run into the casing without cementing, and directly run into the perforating equipment for perforation, forming uniformly spaced wells in the entire hydrate reservoir section. Perforation channel; After a period of time, the perforation channel gradually closes, forming a fracture zone distributed along the perforation channel.

2) Micropipe layout operation:

① Lowering the guide device: the central pipe string is connected to the central channel of the guide device, and the guide device is lowered to the well section of the hydrate reservoir through the central pipe string, and the outlet of the guide hole corresponds to the perforation channel.

②Setting operation: The setting mechanism in the guide device adopts the mechanical setting method, and the guide device is set on the inner wall of the casing through actions such as rotation, lowering, and lifting of the central pipe string.

③Micropipe layout: First, lower the thick-walled conduit from the wellhead of the production well to the guide device. The thick-walled conduit is accurately positioned on the guide cone surface through the positioning mechanism, and the thick-walled conduit cone cooperates with the guide cone surface; The microtube and the microtube enter the guide hole in the guide device along the inner channel of the thick-walled catheter, and the annular gap between the microtube and the thick-walled catheter is smaller than the outer diameter of the microtube, which can avoid buckling of the microtube in the thick-walled catheter; finally, in the wellhead device Under the action of the vertically downward feeding force provided, the micropipe enters the hydrate reservoir horizontally along the broken zone of the perforation channel after passing through the guide hole with a suitable curvature, and under the guidance of the broken zone of the perforated channel, The pilot drill bit squeezes and breaks the hydrate reservoir, and gradually penetrates into the hydrate reservoir until reaching the predetermined depth. The depth range is 10m-20m.

④ Microtube cutting: the cable is connected to the electrochemical cutter through the central pipe column, the central channel and the inclined hole, and the six electrochemical cutters are respectively connected to the outlets of the six pilot holes; the KCL aqueous solution is pumped from the wellhead, and the KCL aqueous solution passes through the center The central passage and inclined hole of the pipe column, guide device reach the electrochemical cutter, and then the cable is energized, and the microtube is electrochemically cut by using DC power supply; after the microtube is cut off, the remaining part is lifted away from the thick-walled catheter channel, so , the assignment of the first microtube ends. Afterwards, the thick-walled catheter is lifted up for a certain distance, and then accurately lowered to another guiding cone surface through the positioning mechanism, and the operation is repeated; once the guiding device is set, six microtubes can be inserted into the hydrate reservoir through six guiding holes.

⑤ Lift the central pipe string, unsealing the guide device, lift the guide device and lower it to another well section of the hydrate reservoir. Pipe layout work. After the micropipe layout operation is completed, the guide device is lifted out of the production well; finally, a uniform micropipe network with a fixed spacing and spatial distribution is formed in the entire hydrate reservoir well section.

The beneficial effect that the present invention has:

1) The device of the present invention is flexible in operation and easy to use, and it is easy to arrange a micropipe network for expanding the contact area between the production channel and the hydrate reservoir in shallow seabed natural gas hydrate reservoirs with weak cementation, looseness and low strength , while ensuring that the microtubule channel (ie, the output channel) is not blocked.

2) The micropipe network arranged in the hydrate reservoir effectively expands the contact area between the production channel and the hydrate reservoir, thereby improving the reservoir permeability, improving the heat and mass transfer efficiency and flow conductivity of the reservoir , to achieve the purpose of improving mining efficiency and realizing the economical and efficient mining of shallow marine natural gas hydrates.

3) The present invention is applicable to various marine natural gas hydrate exploitation methods such as depressurization method, thermal shock method and chemical reagent injection method, and can combine various hydrate exploitation methods to give full play to their respective advantages and significantly improve the production increase effect.

Description of drawings

Fig. 1 is a schematic diagram of the marine shallow natural gas hydrate microtube stimulation device and its principle of the present invention.

Fig. 2 is a top view of the guiding device of the present invention.

Among them: 1. Guiding device; 2. Wellhead device; 3. Central pipe string; 4. Cable; 5. Thick-walled conduit; 1. Inclined hole; 11. Electrochemical cutter; 12. Positioning mechanism; 13. Guide cone; 14. Guide hole; 15. Production well; 16. Casing; 17. Perforation channel.

A-overlying formation, B-hydrate reservoir, C-underlying formation.

Detailed ways

As shown in Fig. 1 and Fig. 2, a kind of marine shallow natural gas hydrate microtube stimulation device of the present invention is composed of a guide device 1, a wellhead device 2, a central pipe string 3, a cable 4, a thick-walled conduit 5, a microtube 6. Composed of 7 pilot drill bits.

The guide device 1 includes a central channel 8, a seat seal mechanism 9, an inclined hole 10, an electrochemical cutter 11, a positioning mechanism 12, a guide cone 13 and a guide hole 14; the guide hole 14 is a circular channel with a suitable curvature, and the guide hole 14 are arranged in six, and the six guide holes 14 are symmetrically distributed around the central passage 8; there are six electrochemical cutters 11, and the six electrochemical cutters 11 are respectively connected with the outlets of the six guide holes 14 for Micropipe 6 carries out cutting operation. The central pipe string 3 is used to connect the central channel 8 of the guiding device 1 , to lower the guiding device 1 to the production well 15 , and to perform setting and unsealing operations on the guiding device 1 . The cable 4 is connected to the electrochemical cutter 11 through the central column 3 , the central channel 8 and the inclined hole 10 . The positioning mechanism 12 plays a guiding and positioning role. The thick-walled conduit 5 is accurately positioned on the guiding cone surface 13 through the positioning mechanism 12, and the cone surface of the thick-walling conduit 5 cooperates with the guiding cone surface 13. The wellhead device 2 is arranged at the wellhead, and the wellhead device 2 provides vertical downward feeding force for the micropipe 6 when the micropipe is arranged. The annular gap between the microtube 6 and the thick-walled conduit 5 is smaller than the outer diameter of the microtube 6, so as to avoid buckling of the microtube 6 in the channel of the thick-walled conduit 5 and ensure the smooth operation of the microtube arrangement. The end port of the micropipe 6 is provided with a pilot drill bit 7, which is used to squeeze and break the hydrate reservoir B when the micropipe is deployed. The micropipe 6 is a high-pressure resistant steel pipe with certain flexibility, and the outer wall of the micropipe 6 is provided with holes with the same aperture, and the holes are circular holes of a certain size, so as to ensure that the micropipe channel (i.e., the output channel) is not blocked during the mining process; The outer diameter of the tube 6 ranges from 15mm to 35mm.

A method for increasing production of shallow marine natural gas hydrate described in the present invention comprises the following steps:

1) Construct production well 15: Drill a vertical wellbore in the shallow marine natural gas hydrate reservoir area, pass through the overlying formation A, and after drilling to the top boundary of the hydrate reservoir B, stop drilling and run in the casing 16 for cementing Cement the well, and then drill through the hydrate reservoir B to the top boundary of the stratum C overlying the natural gas hydrate. Perforation channels 17 with uniform spacing are formed in the well section of the layer; after a period of time, the perforation channels 17 are gradually closed to form broken zones distributed along the perforation channels 17 .

2) Micropipe layout operation:

① Lowering the guiding device: the central pipe string 3 is connected to the central channel 8 of the guiding device 1, and the guiding device 1 is lowered to the well section B of the hydrate reservoir through the central pipe string 3, and the outlet of the pilot hole 14 corresponds to the perforation channel 17.

②Setting operation: The setting mechanism 9 in the guide device 1 adopts a mechanical setting method, and the guide device 1 is set on the inner wall of the casing 16 through actions such as rotation, lowering, and lifting of the central pipe string 3 .

③Micropipe layout: First, lower the thick-walled conduit 5 from the wellhead of the production well 15 to the guide device 1, the thick-walled conduit 5 is accurately positioned on the guide cone 13 through the positioning mechanism 12, and the thick-wall conduit 5 is matched with the guide cone 13 Then enter the microtube 6 by the thick-walled conduit 5, the microtube 6 enters the guide hole 14 in the guide device 1 along the thick-walled conduit 5 inner passages, the microtube 6 and the thick-walled conduit 5 annular gaps are less than the microtube outer diameter, can Avoid micropipe buckling in the thick-walled conduit; finally, under the action of the vertical downward feeding force provided by the wellhead device 2, the micropipe 6 passes through the guide hole 14 with a suitable curvature and breaks along the perforation channel 17 zone horizontally enters the hydrate reservoir B, and under the guidance of the perforation channel 17 crushing zone, the pilot bit 7 squeezes and breaks the hydrate reservoir, and gradually penetrates into the hydrate reservoir B until reaching the predetermined depth, the depth range is 10m -20m.

④ Microtube cutting: the cable 4 is connected to the electrochemical cutter 11 through the central pipe string 3, the central channel 8 and the inclined hole 10, and the six electrochemical cutters 11 are respectively connected to the outlets of the six guide holes 14; pumped in from the wellhead KCL aqueous solution, the KCL aqueous solution reaches the electrochemical cutter 11 through the central pipe column 3, the central channel 8 and the inclined hole 10 of the guide device, and then the cable 4 is energized, and the microtube 6 is electrochemically cut by direct current power supply; the microtube is cut off After 6, the remaining part is lifted away from the thick-walled conduit 5 channels, so far, the first microtube arrangement operation is completed. Subsequently, the thick-walled conduit 5 is lifted up for a certain distance and accurately lowered to another guide cone 13 through the positioning mechanism 12, and the operation is repeated; the guide device 1 can be inserted into the hydrate reservoir B through six guide holes 14 once set Six microtubules6.

⑤ Lift the central pipe string 3, unsealing the guide device 1, lift the guide device 1 and lower it to another well section of the hydrate reservoir B, the outlet of the guide hole 14 corresponds to the perforation channel 17, and then After setting, repeat the microtube arrangement operation. After the micro-pipe arrangement operation is completed, the guide device 1 is lifted away from the production well 15; finally, a micro-pipe network with uniform spacing and spatial distribution is formed in the entire hydrate reservoir B well section.

Claims (4)

1. A shallow layer natural gas hydrate microtubule of ocean increases output device which characterized in that: the device consists of a guide device (1), a wellhead device (2), a central pipe column (3), a cable (4), a thick-wall guide pipe (5), a micro pipe (6) and a guide drill bit (7);

the guide device (1) comprises a central channel (8), a seat sealing mechanism (9), an inclined hole (10), an electrochemical cutter (11), a positioning mechanism (12), a guide conical surface (13) and a guide hole (14); the guide holes (14) are circular channels, six guide holes (14) are arranged, and the six guide holes (14) are symmetrically distributed around the central channel (8); six electrochemical cutters (11) are arranged, and the six electrochemical cutters (11) are respectively connected with outlets of the six guide holes (14) and are used for cutting the microtubes (6); the central pipe column (3) is used for connecting a central passage (8) of the guide device (1), lowering the guide device (1) to a production well (15), and performing setting and unsealing operation on the guide device (1); the cable (4) is connected to the electrochemical cutter (11) through the center pipe column (3), the center channel (8) and the inclined hole (10); the positioning mechanism (12) plays a role in guiding and positioning, the thick-wall catheter (5) is accurately positioned on the guiding conical surface (13) through the positioning mechanism (12), and the conical surface of the thick-wall catheter (5) is matched with the guiding conical surface (13);

the wellhead device (2) is arranged at a wellhead, and the wellhead device (2) provides vertical downward feeding force for the micro-pipe (6) when the micro-pipe (6) is arranged; the annular gap between the micro-tube (6) and the thick-wall guide tube (5) is smaller than the outer diameter of the micro-tube (6), and a guide drill bit (7) is arranged at the tail end port of the micro-tube (6); the outer wall of the microtube (6) is provided with holes with the same aperture.

2. The marine superficial natural gas hydrate microtubule stimulation device according to claim 1, which is characterized in that: the micro-pipe (6) is a high-pressure resistant steel pipe.

3. The marine superficial natural gas hydrate microtubule stimulation device according to claim 1, which is characterized in that: the outer diameter of the micro-tube (6) is 15mm-35mm.

4. The stimulation method of the marine superficial natural gas hydrate stimulation device of claim 1, comprising the steps of:

1) Constructing a production well (15): drilling a vertical borehole in a marine shallow natural gas hydrate reservoir region, penetrating an overlying stratum (A), stopping drilling, setting a casing (16) for cementing and well cementing after drilling to the position near the top boundary of a hydrate reservoir (B), drilling through the hydrate reservoir (B) to the top boundary of a natural gas hydrate underlying stratum (C), directly setting perforating equipment for perforating without performing well cementing operation after setting the casing (16), and forming perforating channels (17) with uniform intervals in the whole hydrate reservoir well section; after a period of time, the perforation channel (17) is gradually closed to form crushing zones distributed along the perforation channel (17);

2) Arranging and operating the micro-pipes:

(1) lowering a guide device: the center pipe column (3) is connected to a center channel (8) of the guiding device (1), the guiding device (1) is lowered to a well section of the hydrate reservoir (B) through the center pipe column (3), and an outlet of the guiding hole (14) corresponds to the perforation channel (17);

(2) setting operation: a seat sealing mechanism (9) in the guide device (1) adopts a mechanical seat sealing mode, and the guide device (1) is sealed on the inner wall of the casing (16) in a seat way through actions of rotating, lowering and lifting the central pipe column (3) and the like;

(3) arranging a micro tube: firstly, a thick-wall guide pipe (5) is placed from the wellhead of a production well (15) to a guide device (1), the thick-wall guide pipe (5) is accurately located on a guide conical surface (13) through a positioning mechanism (12), and the conical surface of the thick-wall guide pipe (5) is matched with the guide conical surface (13); then, a micro-tube (6) is put into the guide device through the thick-wall guide tube (5), the micro-tube (6) enters a guide hole (14) in the guide device (1) along an inner channel of the thick-wall guide tube (5), and an annular gap between the micro-tube (6) and the thick-wall guide tube (5) is smaller than the outer diameter of the micro-tube, so that the micro-tube can be prevented from buckling in the thick-wall guide tube; finally, under the action of vertical downward feeding force provided by the wellhead device (2), the micro-pipe (6) passes through a guide hole (14) with proper curvature and then horizontally enters the hydrate reservoir stratum (B) along the crushing area of the perforation channel (17), and under the guiding action of the crushing area of the perforation channel (17), the guide drill bit (7) extrudes the crushed hydrate reservoir stratum and gradually penetrates into the hydrate reservoir stratum (B) until the preset depth is reached, wherein the depth range is 10m-20m;

(4) cutting the microtubes: the cable (4) is connected to the electrochemical cutters (11) through the central pipe column (3), the central channel (8) and the inclined holes (10), and the six electrochemical cutters (11) are respectively connected with outlets of the six guide holes (14); pumping a KCL aqueous solution from a wellhead, leading the KCL aqueous solution to reach an electrochemical cutter (11) through a central pipe column (3), a central channel (8) of a guide device and an inclined hole (10), then electrifying a cable (4), and carrying out electrochemical cutting on a microtube (6) by using direct current power supply; after the micro-pipe (6) is cut off, the rest part is lifted away from the channel of the thick-wall guide pipe (5), and the first micro-pipe arrangement operation is finished; then, lifting the thick-wall guide pipe (5) for a certain distance, accurately lowering the thick-wall guide pipe to the other guide conical surface (13) through a positioning mechanism (12), and repeating the operation; six micro-pipes (6) can be inserted into the hydrate reservoir stratum (B) through six guide holes (14) by one-time setting of the guide device (1);

(5) lifting the central pipe column (3), carrying out deblocking operation on the guiding device (1), lifting or lowering the guiding device (1) to the other well section of the hydrate reservoir (B), setting the outlet of the guiding hole (14) corresponding to the perforation channel (17), and repeatedly carrying out microtubule arrangement operation; after the microtube arrangement operation is finished, lifting the guide device (1) away from the production well (15); finally, a uniform, spaced and spatially distributed micro-pipe network is formed in the whole hydrate reservoir (B) well section.

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