Simple integrated underwater water injection system

Abstract

The invention discloses a simple integrated underwater water injection system which comprises a base, a wellhead body and a first gate valve, and a connecting cylinder is arranged on the base; the lower end of the wellhead body is connected with the connecting cylinder, and a vertically-through containing cavity is formed in the wellhead body. The casing hanger A, the packing device A, the casing hanger B, the packing device B and the oil pipe hanger are arranged in the containing cavity from bottom to top; a vertically-through cavity is formed in the inner side of the oil pipe hanger, and a blanking plug used for isolating the cavity from the outer space of the oil pipe hanger is arranged in the cavity. The first gate valve is arranged on the outer side of the wellhead body and is communicated with the cavity in the tubing hanger; the Christmas tree cap is arranged on the top of the wellhead body. The integral function and operation process of the water injection device are optimized, the integrated underwater water injection system which is simple and reliable in structure and more convenient to use is formed, the economical underwater water injection requirement is met, and the problem that a water injection device well groove and an oil extraction device well groove are tight is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater oil and gas exploitation engineering, and particularly relates to a simple integrated underwater water injection system. Background Art

[0002] During the process of oil and gas exploitation, especially the exploitation of offshore oil, it is necessary to first drill production wells on the seabed and then install production equipment for exploitation. After the offshore oil has been exploited to a certain extent, due to insufficient pressure in the oil layer, the oil cannot be completely pumped out. At this time, water injection is often used to inject water into the oil layer to increase the pressure, so that the oil can flow out along the pipeline under the action of high pressure.

[0003] Due to the imperfect existing oilfield injection-production well pattern, the demand for development water injection is increasing day by day. There is an urgent need to increase the number of injection wells to improve the water injection development effect. However, the development cost of injection wells is relatively high, and the structure of the conventional simple underwater injection-production system is complex, and the equipment cost is relatively high. At present, the production platform faces the problem of insufficient well slot resources. The limited remaining well slots are preferentially used for production wells, and there are no extra well slots to meet the needs of injection wells. Developing injection wells separately is too costly. If production wells are used as injection wells, the number of production wells will be insufficient, affecting the oil production. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and design a simple integrated underwater water injection system. This kind of underwater water injection system is applicable to underwater water injection in shallow water areas and solves the problem of tight well slots for water injection devices and oil production devices.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] A simple integrated underwater water injection system, comprising:

[0007] A base, on which a connecting cylinder is provided;

[0008] A wellhead body, the lower end of which is connected to the connecting cylinder, and the wellhead body has a vertically penetrating accommodation cavity;

[0009] A casing hanger A, which is seated in the accommodation cavity;

[0010] A packing device A, which is located above the casing hanger A and is seated in the accommodation cavity;

[0011] A casing hanger B, which is located above the packing device A and is seated in the accommodation cavity;

[0012] Packer device B, which is located above the casing hanger B and is set and hung in the accommodation cavity;

[0013] A tubing hanger, which is located above the packer device B and is set and hung in the accommodation cavity. The inner side of the tubing hanger has a cavity that penetrates up and down, and a plug is provided in the cavity to isolate the cavity from the external space of the tubing hanger;

[0014] A first gate valve, which is provided on the outer side of the wellhead body and is connected to the cavity inside the tubing hanger;

[0015] A Christmas tree cap, which is provided on the top of the wellhead body.

[0016] Further, it further includes:

[0017] A second gate valve, which is provided on the outer side of the wellhead body and is connected to the accommodation cavity inside the wellhead body.

[0018] Further, three clamping grooves are provided on the inner wall of the accommodation cavity, and expandable locking rings are respectively provided on the outer sides of the packer device A, the packer device B and the tubing hanger. The locking rings are clamped with the clamping grooves.

[0019] Further, an extrusion ring is provided above the locking rings at the packer device A and the packer device B to control the outward expansion of the locking rings and make them clamped with the clamping grooves.

[0020] Further, a first sealing ring is provided between the packer device A and the casing hanger A, and a second sealing ring is provided between the packer device A and the wellhead body;

[0021] Optionally, a third sealing ring is provided between the packer device B and the casing hanger B, and a fourth sealing ring is provided between the packer device B and the wellhead body;

[0022] Optionally, the tubing hanger is provided with a water inlet hole corresponding to the first gate valve, and two rubber seals are provided between the tubing hanger and the wellhead body, and the rubber seals are respectively located on the upper side and the lower side of the water inlet hole.

[0023] Further, the Christmas tree cap includes a sealing cover and a pipeline fixing device. The pipeline fixing device is provided below the sealing cover. A plurality of sealing heads are provided on the sealing cover, and the sealing heads are connected to the pipeline fixing device at the bottom. The bottom of the pipeline fixing device is provided with positioning pins corresponding to the sealing heads, and a plurality of wire passing holes are provided on the tubing hanger corresponding to the positioning pins.

[0024] Further, a hook is provided at the bottom of the sealing cover, and the hook is used to hang the ethylene glycol device;

[0025] Optionally, a lifting lug is welded to the top of the sealing cover.

[0026] Further, an interference fit is provided between the plugging device and the cavity inside the tubing hanger;

[0027] Optionally, the Christmas tree cap is fixed to the wellhead body through a locking block;

[0028] Optionally, blind flange plugs are installed at the water inlet of the first gate valve and the water outlet of the second gate valve.

[0029] Further, a plurality of guide cylinders are provided on the base, a guide rod is inserted and connected in the guide cylinder, the lower end of the guide rod is inserted into the seabed, and the guide cylinder slides along the guide rod.

[0030] Further, an anode block and a mechanical compass disk are provided on the base.

[0031] In summary, the technical effects and advantages of the present invention are as follows:

[0032] The present invention optimizes the overall function and operation process of the water injection device, forms an integrated underwater water injection system with a simple and reliable structure and more convenient use, meets the economic underwater water injection requirements. The water injection system controls the opening and closing of the water path through the first gate valve and communicates with the cavity of the tubing hanger through the water inlet hole. The upper side of the cavity of the tubing hanger is isolated from the external pressure through the plugging device. When performing water injection operations, the first gate valve is opened to inject water into the tubing, and water injection pressure is applied to the oil layer. It is possible to increase the oil production through water injection without affecting the number of production well slots on the oil production platform. This water injection system has a simple and reliable structure and is convenient to use;

[0033] This water injection system can be directly installed on the production well, and can be used for both water injection operations and oil production operations, without the need for additional injection wells, solving the problem of tight well slots for the water injection device and the production device. Especially, sealing structures are provided on both the upper and lower sides of the water inlet hole. This sealing structure uses rubber extrusion sealing, with a simple and reliable design, low cost, and convenient installation, greatly reducing the difficulty of underwater blind operation during installation, and at the same time reducing the loss rate of seals during the installation process;

[0034] The top of the wellhead body is sealed by the Christmas tree cap. The Christmas tree cap is designed with a sealing head for easy threading. A pipeline plug-in board and a pipeline joint are installed on the upper part of the sealing head. The bottom has a positioning pin and a card slot. The positioning pin and the card slot cooperate with the top of the tubing hanger for positioning. The circuit enters the high-pressure wellhead through the sealing head and is fixed through the pipeline plug-in board and the pipeline joint, with a firm and reliable installation;

[0035] The tubing hanger is designed with multiple wire threading holes, which correspond one by one to the sealing heads on the Christmas tree cap, and can accommodate multiple downhole valve control pipelines to pass through. By controlling the opening and closing of valves at different formation depths in the well, the function of stratified water injection is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic diagram of the overall structure of an integrated underwater water injection system according to an embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of the structure of the integrated underwater water injection system according to an embodiment of the present invention when the wellhead body is removed;

[0039] Figure 3 It is a schematic cross-sectional structure diagram of the integrated underwater water injection system according to an embodiment of the present invention;

[0040] Figure 4 It is Figure 3 The enlarged structure diagram at position A in

[0041] Figure 5 It is a schematic diagram of the structure of the Christmas tree cap and its accessory components according to an embodiment of the present invention;

[0042] Figure 6 It is a schematic diagram of the bottom structure of the Christmas tree cap according to an embodiment of the present invention;

[0043] Figure 7 It is an axonometric cross-sectional structure diagram of the integrated underwater water injection system according to an embodiment of the present invention when the guide rod is removed;

[0044] Figure 8 It is a cross-sectional plan view of the integrated underwater water injection system according to an embodiment of the present invention when the guide rod is removed;

[0045] Figure 9 It is Figure 8 The enlarged structure diagram at position B in

[0046] Figure 10 It is Figure 8 The enlarged structure diagram at position C in

[0047] Figure 11 It is Figure 8 The enlarged structure diagram at position D in

[0048] Figure 12 is Figure 11 The enlarged view of the structure at position E in the figure.

[0049] In the figure, 1 is the base; 2 is the wellhead body; 3 is the casing hanger A; 4 is the casing hanger B; 5 is the tubing hanger; 6 is the first gate valve; 7 is the Christmas tree cap; 8 is the mechanical compass; 9 is the anode block; 10 is the packer A; 11 is the packer B; 12 is the connecting cylinder; 13 is the second gate valve; 14 is the extrusion ring; 15 is the set screw; 16 is the locking ring; 17 is the sealing cover; 18 is the first sealing ring; 19 is the second sealing ring; 20 is the casing A; 21 is the casing B; 22 is the fixed retaining ring; 23 is the limit retaining ring; 24 is the limit ring; 25 is the excitation ring; 26 is the tubing; 27 is the rubber seal; 271 is the sealing part; 28 is the locking block; 29 is the pipeline fixing device; 291 is the positioning pin; 30 is the hook; 31 is the sealing head; 32 is the guide key; 33 is the lifting lug; 34 is the blind plate plug; 35 is the plugging device; 36 is the guide cylinder; 37 is the guide rod; 38 is the screw; 1001 is the cavity; 1002 is the water inlet hole; 1003 is the wire threading hole; 1004 is the drain hole. Specific embodiments

[0050] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] This embodiment proposes a simple integrated underwater water injection system, as Figures 1 - 12 shown. The water injection system mainly includes components such as the base 1, the wellhead body 2, the casing hanger A 3, the casing hanger B 4, the tubing hanger 5, the first gate valve 6, the second gate valve 13, the packer A 10, the packer B 11, the mechanical compass 8, the anode block 9, and the Christmas tree cap 7. In this embodiment, both the first gate valve 6 and the second gate valve 13 adopt underwater ROV manual gate valves.

[0053] Refer to Figure 1, a connecting cylinder 12 is welded on the base 1, and the lower end of the wellhead body 2 is fixedly connected to the connecting cylinder 12 through a flange. The wellhead body 2 is cylindrical in shape and has an accommodating cavity that penetrates up and down inside. Inside the accommodating cavity on the inner side of the wellhead body 2, a casing hanger A3, a packer device A10, a casing hanger B4, a packer device B11, and a tubing hanger 5 are successively seated from bottom to top, and a Christmas tree cap 7 is provided at the top of the wellhead body 2.

[0054] As Figure 3 , Figure 9 , Figure 10 and Figure 11 shown, three card slots corresponding to the packer device A10, the packer device B11, and the tubing hanger 5 are respectively formed on the inner wall of the accommodating cavity from top to bottom. Locking rings 16 are installed on the outer sides of the packer device A10, the packer device B11, and the tubing hanger 5. The locking ring 16 is designed with an opening and has a certain elasticity.

[0055] As Figure 10 shown, the packer device A10 is inserted into the space between the casing hanger A3 and the wellhead body 2 and is seated on the casing hanger A3. The packer device A10 is designed with a locking ring 16 and a pressing ring 14. The pressing ring 14 is installed on the packer device A10 through a set screw. During the installation process, by pressing the pressing ring 14 downward, the pressing ring 14 is inserted downward into the gap between the locking ring 16 and the packer device A10, so that the locking ring 16 expands outward and is engaged with the card slot on the inner wall of the wellhead body 2, fixing the packer device A10 and the wellhead body 2 together.

[0056] A first sealing ring 18 is provided between the packer device A10 and the casing hanger A3, and a second sealing ring 19 is provided between the packer device A10 and the wellhead body 2. When installing the packer device A10, by pressing the first sealing ring 18 and the second sealing ring 19 downward, the first sealing ring 18 and the second sealing ring 19 will closely adhere to the inner wall of the wellhead body 2 and the outer wall of the casing hanger A3, thereby sealing the pressure between the well and the annulus.

[0057] The structure of the packer device B11 is the same as that of the packer device A10. The packer device B11 is inserted into the space between the casing hanger B4 and the wellhead body 2 and is seated on the casing hanger B4. By the same principle, the packer device B11 is designed with a locking ring and a pressing ring. The pressing ring is installed on the packer device B11 through a set screw. During the installation process, by pressing the pressing ring downward, the pressing ring is inserted downward into the gap between the locking ring and the packer device B11, so that the locking ring expands outward and is engaged with the card slot on the inner wall of the wellhead body 2, fixing the packer device B11 and the wellhead body 2 together. At the same time, the casing hanger B4 is seated on the top of the packer device A10.

[0058] A third sealing ring is provided between the packer device B11 and the casing hanger B4, and a fourth sealing ring is provided between the packer device B11 and the wellhead body 2. When installing the packer device B11, the third sealing ring and the fourth sealing ring are squeezed downward, and the third sealing ring and the fourth sealing ring will closely adhere to the inner wall of the wellhead body 2 and the outer wall of the casing hanger B4, thereby sealing the pressure between the well and the annulus.

[0059] See Figure 8 , the lower end of the casing hanger A3 is threadedly connected to the casing A20, the casing A20 extends downward continuously, the lower end of the casing hanger B4 is threadedly connected to the casing B21, and the casing B21 passes through the casing hanger A3 and the casing A20.

[0060] Refer to Figure 9 , a fixed retaining ring 22, a limit retaining ring 23, a limit ring 24 and an excitation ring 25 are provided on the outside of the tubing hanger 5. How these components cooperate with the locking ring 16 can be referred to the hanger recovery tool with the publication number of CN118442016A. With the above structure, the installation and recovery of the tubing hanger 5 can be quickly completed by this tool. After the locking ring 16 on the tubing hanger 5 is activated, it will be engaged with the card slot on the inner wall of the wellhead body 2, so that the tubing hanger 5 is fixed to the wellhead body 2. The locking system has a reliable structure, good stability and convenient installation.

[0061] As Figure 8 , Figure 11 shown, the inside of the tubing hanger 5 has a cavity 1001 that penetrates up and down. The lower end of the tubing hanger 5 is threadedly connected to the tubing 26, and the tubing 26 communicates with the cavity 1001. The tubing 26 will pass through the casing hanger B4, the casing B21, the casing hanger A3, the casing A20, and extend downward.

[0062] As Figure 7 shown, the first gate valve 6 and the second gate valve 13 are distributed and installed on both sides of the wellhead body 2. The valves are mechanically manually controlled and matched with the ROV interface within the API 17H standard. The valves control the opening and closing of the waterway.

[0063] As Figure 11 , Figure 12As shown, a drain hole 1004 is opened on one side of the wellhead body 2 to connect the second gate valve 13 with the accommodation cavity inside the wellhead body 2. When lowering and installing the casing hanger A3, the casing hanger B4, and the tubing hanger 5, the downhole fluid can be discharged by opening the gate valve on this side. An inlet hole 1002 is opened on the other side of the wellhead body 2 and the tubing hanger 5 to connect the first gate valve 6 with the cavity 1001 inside the tubing hanger 5. During the water injection operation, water can be injected by opening the gate valve on this side. And two rubber seals 27 are arranged between the tubing hanger 5 and the wellhead body 2. The rubber seals 27 are located above and below the inlet hole 1002 to ensure the sealing performance.

[0064] Reference Figure 12 , the rubber seal 27 bulges outwards to form a sealing part 271. The sealing part 271 is activated by extrusion for sealing. The sealing form is simple and reliable, easy to install, has high pressure resistance, good corrosion resistance, low economic cost, long service life and high stability, greatly reducing the difficulty of underwater blind installation, and at the same time reducing the loss rate of the seal during installation.

[0065] Reference Figure 9 , a rubber seal 27 is also arranged on the upper part of the tubing hanger 5. The sealing form of the rubber seal 27 is the same as that of the aforementioned rubber seal 27. The rubber seal 27 is located below the locking ring 16 on the tubing hanger 5.

[0066] Reference Figure 4 、 Figure 5 , the Christmas tree cap 7 is installed on the top of the wellhead body 2 and fixed to the wellhead body 2 by a lock block 28. At the same time, using a rubber seal between the Christmas tree cap 7 and the wellhead body 2 can prevent seawater and marine organisms from entering the wellhead body 2.

[0067] The Christmas tree cap 7 is composed of a sealing cover 17 and a pipeline fixing device 29. A hook 30 is designed at the bottom of the sealing cover 17 to hang the ethylene glycol device. Ethylene glycol is provided inside the ethylene glycol device. Since there is still a certain space between the tubing hanger 5 and the sealing cover 17, the ethylene glycol device is hung on the hook 30. After the ethylene glycol volatilizes, it can prevent corrosion and improve the service life of the device.

[0068] Reference Figure 4 、 Figure 5 、 Figure 9, a sealing head 31 is installed on the sealing cover 17. The sealing head 31 is connected to the pipeline fixing device 29 at the bottom. The pipeline fixing device 29 is a hollow cylindrical structure. The bottom of the pipeline fixing device 29 has positioning pins 291 and clamping grooves for positioning and fixing with the oil pipe hanger 5 below. The middle of the above-mentioned sealing head 31 has a wire-passing hole that penetrates up and down, so that the pipeline can pass through the wire-passing hole. The pipeline will pass through the wire-passing hole and through the pipeline fixing device 29 to achieve the coherence of pipeline crossing and at the same time restrain and fix the pipeline.

[0069] The oil pipe hanger 5 is provided with a plurality of wire-passing holes 1003 and corresponds to the sealing heads 31 on the Christmas tree cap 7 one by one, and can accommodate a plurality of downhole valve control pipelines to pass through. By controlling the opening and closing of valves at different formation depths in the well, the function of stratified water injection is realized.

[0070] Reference Figure 4 、 Figure 9 , a guiding key 32 is arranged on the pipeline fixing device 29. The guiding key 32 is fixed to the pipeline fixing device 29 by screws 38. A corresponding guiding groove is designed in the accommodating cavity in the wellhead body 2. When installing the Christmas tree cap 7, the wire-passing holes 1003 on the oil pipe hanger 5 and the sealing head 31 can be quickly and accurately aligned. During installation, the positioning pin 291 is inserted into the upper end of the wire-passing hole 1003 on the oil pipe hanger 5.

[0071] A lifting lug 33 is welded on the top of the Christmas tree cap 7 for hoisting the underwater water injection system.

[0072] Such as Figure 1 、 Figure 7 As shown, blind flange plugs 34 are installed at the water inlet of the first gate valve 6 and the water outlet of the second gate valve 13. The blind flange plugs 34 are fixedly installed on the first gate valve 6 and the second gate valve 13 through flanges. When not injecting or draining water, the inlets and outlets of the first gate valve 6 and the second gate valve 13 are blocked by the blind flange plugs 34. When injecting or draining water, the blind flange plugs 34 are removed and a water pipe is connected.

[0073] Since the upper part of the cavity 1001 inside the oil pipe hanger 5 is through, a plug 35 needs to be placed in the cavity 1001 at this time to isolate the injection pressure from the external pressure. Water cannot flow out from the upper part of the cavity 1001. After the upper part of the cavity 1001 is blocked, water will flow downward along the cavity 1001 and be injected into the oil layer at the bottom of the seabed through the oil pipe 26 to increase the pressure in the oil layer.

[0074] The plug 35 and the cavity 1001 inside the oil pipe hanger 5 are in interference fit and are hard pressed in. It can be taken out by a special tool when taking it out.

[0075] When no water is injected, the first gate valve 6 is closed, and at the same time, the plug 35 is taken out, and then the Christmas tree cap 7 is removed. The oil can flow upward along the oil pipe 26. That is to say, only when the pressure of the oil layer is insufficient, water will be injected into the oil layer to increase the pressure.

[0076] As Figure 1 , Figure 2 shown, the anode block 9 and the mechanical compass disk 8 are both installed on the upper surface of the base 1. The anode block 9 is used to slow down the seawater corrosion, and the mechanical compass disk 8 is used for leveling when installing the wellhead.

[0077] Guide cylinders 36 are welded at multiple positions on the base 1. Guide rods 37 are inserted and connected in the guide cylinders 36. The lower ends of the guide rods 37 will be inserted into the seabed. Then when the underwater water injection system is lowered, the guide cylinders 36 will slide downward along the guide rods 37. Due to the certain fluidity of the seawater, the underwater water injection system can be lowered to the designated position on the seabed through the guide rods 37.

[0078] In summary, the present application optimizes the overall function and operation process of the water injection device, forms an integrated underwater water injection system with a simple and reliable structure and more convenient use, meets the economic underwater water injection requirements. The water injection system controls the opening and closing of the water circuit through the first gate valve, and is communicated with the cavity of the tubing hanger through the water inlet hole. The upper side of the cavity of the tubing hanger is isolated from the external pressure through the plug during the water injection operation. When the water injection operation is carried out, the first gate valve is opened to inject water into the oil pipe to pressurize the oil layer. It can improve the oil production by injecting water while not affecting the number of production well slots of the oil production platform. This water injection system has a simple and reliable structure and is convenient to use;

[0079] This water injection system is directly installed on the production well, and can be used for both water injection operations and oil production operations, without the need for additional injection wells, solving the problem of the tightness of the well slots of the water injection device and the production device. Especially, sealing structures are arranged on both the upper and lower sides of the water inlet hole. The sealing structure adopts rubber extrusion sealing, with a simple and reliable design, low cost, and convenient installation, greatly reducing the difficulty of blind operation during underwater installation, and at the same time reducing the loss rate of the seals during the installation process;

[0080] The top of the wellhead body is sealed by the Christmas tree cap. The Christmas tree cap is designed with a sealing head convenient for threading. A pipeline plug-in board and a pipeline joint are installed on the upper part of the sealing head. The bottom has a positioning pin and a card slot. The positioning pin and the card slot will cooperate with the top of the tubing hanger for positioning. The circuit enters the high-pressure wellhead through the sealing head and is fixed by the pipeline plug-in board and the pipeline joint, with a firm and reliable installation;

[0081] The tubing hanger is designed with multiple wire threading holes, which correspond one by one to the sealing heads on the Christmas tree cap, and can accommodate multiple downhole valve control pipelines to pass through. By controlling the opening and closing of valves at different formation depths downhole, the function of stratified water injection is realized.

[0082] For ease of explanation, spatial relative terms such as "upper", "lower", "outer layer", "inner layer", etc. are used in the embodiments to describe the relationship of one element or feature shown in the figure relative to another element or feature. It should be understood that, in addition to the orientation shown in the figure, the spatial terms are intended to include different orientations of the device during use or operation. Therefore, the exemplary term "lower" can include both upper and lower orientations.

[0083] Moreover, relational terms such as "3" and "4" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0084] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms of specific transformations without departing from the spirit of the invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A simple integrated underwater water injection system, characterized in that: include: A base (1), wherein a connecting tube (12) is provided on the base (1); A wellhead body (2), the lower end of which is connected to the connecting tube (12), and the wellhead body (2) has a receiving cavity which is connected vertically; A casing hanger A (3), wherein the casing hanger A (3) is suspended in the accommodating cavity; An isolation device A (10), the isolation device A (10) is located above the casing hanger A (3) and is suspended in the accommodating cavity; A casing hanger B (4), the casing hanger B (4) being located above the isolation device A (10) and hanging in the accommodating cavity; A sealing device B (11), the sealing device B (11) is located above the casing hanger B (4) and is suspended in the accommodating cavity; A tubing hanger (5), the tubing hanger (5) being located above the isolation device B (11) and hanging in the accommodating cavity, the inner side of the tubing hanger (5) being provided with a cavity (1001) penetrating from top to bottom, the cavity (1001) being provided with a plug (35) for isolating the cavity (1001) from the external space of the tubing hanger (5); a first gate valve (6), the first gate valve (6) being arranged on the outside of the wellhead body (2), the first gate valve (6) being in communication with the cavity (1001) in the tubing hanger (5); A Christmas tree cap (7), the Christmas tree cap (7) is arranged on the top of the wellhead body (2).

2. The simple integrated underwater water injection system according to claim 1, characterized in that: Also includes: A second gate valve (13), wherein the second gate valve (13) is arranged on the outside of the wellhead body (2), and the second gate valve (13) is communicated with the accommodating cavity in the wellhead body (2).

3. The simple integrated underwater water injection system according to claim 1, characterized in that: The inner wall of the accommodating cavity is provided with three slots, and the outer sides of the isolation device A (10), the isolation device B (11) and the tubing hanger (5) are respectively provided with locking rings (16) that can be opened and closed, and the locking rings (16) are engaged with the slots.

4. The simple integrated underwater water injection system according to claim 3, characterized in that: An extrusion ring (14) is provided above the locking ring (16) at the isolation device A (10) and the isolation device B (11), and the extrusion ring (14) is used to control the locking ring (16) to expand outwards and engage with the locking groove.

5. The simple integrated underwater water injection system according to claim 1, characterized in that: A first sealing ring (18) is provided between the isolation device A (10) and the casing hanger A (3), and a second sealing ring (19) is provided between the isolation device A (10) and the wellhead body (2); and / or, a third sealing ring is provided between the isolation device B (11) and the casing hanger B (4), and a fourth sealing ring is provided between the isolation device B (11) and the wellhead body (2); And / or, the tubing hanger (5) is provided with a water inlet hole (1002) corresponding to the first gate valve (6), and two rubber seals (27) are provided between the tubing hanger (5) and the wellhead body (2), and the rubber seals (27) are respectively located on the upper side and the lower side of the water inlet hole (1002).

6. The simple integrated underwater water injection system according to claim 1, characterized in that: The Christmas tree cap (7) comprises a sealing cover (17) and a pipeline fixing device (29). The pipeline fixing device (29) is arranged below the sealing cover (17). A plurality of sealing heads (31) are arranged on the sealing cover (17). The sealing heads (31) are connected to the pipeline fixing device (29) at the bottom. A positioning pin (29) is arranged at the bottom of the pipeline fixing device (29) corresponding to the sealing head (31). A plurality of threading holes (1003) are opened on the tubing hanger (5) corresponding to the positioning pin (29).

7. The simple integrated underwater water injection system according to claim 6, characterized in that: A hook (30) is provided at the bottom of the sealing cover (17), and the hook (30) is used to hang the ethylene glycol device; And / or, a lifting lug (33) is welded on the top of the sealing cover (17).

8. The simple integrated underwater water injection system according to claim 1, characterized in that: The plug (35) and the cavity (1001) inside the tubing hanger (5) are in interference fit; And / or, the Christmas tree cap (7) and the wellhead body (2) are fixed by a locking block (28); And / or, a blind plate plug (34) is installed at the water inlet of the first gate valve (6) and the water outlet of the second gate valve (13).

9. The simple integrated underwater water injection system according to claim 1, characterized in that: The base (1) is provided with a plurality of guide cylinders (36), the guide cylinders (36) are connected with guide rods (37) inserted therein, the lower ends of the guide rods (37) are inserted into the seabed, and the guide cylinders (36) slide along the guide rods (37).

10. The simple integrated underwater water injection system according to claim 1, characterized in that: An anode block (9) and a mechanical compass (8) are provided on the base (1).

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