Separated layer water injection process pipe column and using method thereof

Abstract

The invention relates to the technical field of separated layer water injection of oil fields, in particular to a separated layer water injection process pipe column and a using method thereof, and aims to relieve the technical problem of sealing failure of a packer in the separated layer water injection process. The tubular column comprises a casing protection packer, an expansion type packer, a water well two-way anchor and a compression type packer which are sequentially distributed at intervals along a straight line and connected through an oil pipe so as to be used for tripping in a casing pipe. The casing protection packer is used for being arranged outside a high-pressure water injection layer and a low-pressure water injection layer. The expansion type packer, the water well two-way anchor and the compression type packer are used for being arranged between a high-pressure water injection layer and a low-pressure water injection layer. According to the tubular column, through cooperation of the water well two-way anchor, the expansion type packer and the compression type packer, the combination mode of two-way anchoring and double packers is formed in the well section with the maximum packer failure risk, and therefore the reliability of tubular column setting is improved, and separated layer water injection can be smoothly conducted under the action of the packers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield separate layer water injection, and in particular to a separate layer water injection process pipe column and a use method thereof. BACKGROUND

[0002] The separate layer water injection technology is a selective water injection method for different layers in an oilfield during oilfield development in order to improve the exploitation efficiency of the oil layer and the recovery rate of crude oil.

[0003] During the separate layer water injection process, dynamic adjustment and single layer starting and stopping need to be frequently performed, and these operations will cause the separate layer packer to simultaneously bear the double effects of "large pressure difference + alternating pressure difference". Under this pressure environment, the water injection pipe column will produce a peristaltic effect, causing the rubber tube of the packer to gradually fail under the peristaltic effect, and once the separate layer sealing fails, the effective period of the water injection pipe column will be greatly shortened, and the original separate layer water injection will be changed into general water injection, thereby causing problems such as under injection or over injection. SUMMARY

[0004] The purpose of the present application is to provide a separate layer water injection process pipe column and a use method thereof to alleviate the technical problem of sealing failure of the packer during the separate layer water injection process.

[0005] In order to solve the above technical problems, the technical solution provided by the present application is as follows:

[0006] In a first aspect, the present application provides a separate layer water injection process pipe column, comprising: a casing protection packer, an expansion type packer, a water well bidirectional anchor and a compression type packer.

[0007] The casing protection packer, the expansion type packer, the water well bidirectional anchor and the compression type packer are sequentially and spacedly distributed along a straight line and connected by a tubing to form a pipe column for running into a casing.

[0008] The casing protection packer is arranged outside the high pressure water injection layer and the low pressure water injection layer.

[0009] The expansion type packer, the water well bidirectional anchor and the compression type packer are arranged between the high pressure water injection layer and the low pressure water injection layer.

[0010] Further, the separate layer water injection process pipe column further comprises a bridge type eccentric water distributor and a sitting sliding sleeve.

[0011] The bridge type eccentric water distributor is fixed to the tubing and located between the casing protection packer and the expansion type packer to be arranged in the low pressure water injection layer.

[0012] The sitting sliding sleeve is fixed to the oil pipe and is located at the side of the compression packer away from the water well bidirectional anchor for being arranged in the high-pressure water injection layer.

[0013] Further, the layered water injection process pipe column further comprises a ball seat, a bridge type eccentric water distributor and a constant pressure sliding sleeve.

[0014] The ball seat is fixed to the oil pipe and is located at the side of the compression packer away from the water well bidirectional anchor for being arranged outside the high-pressure water injection layer and the low-pressure water injection layer.

[0015] The bridge type eccentric water distributor is fixed to the oil pipe and is located between the ball seat and the compression packer for being arranged in the low-pressure water injection layer.

[0016] The constant pressure sliding sleeve is fixed to the oil pipe and is located between the casing protection packer and the expansion packer for being arranged in the high-pressure water injection layer.

[0017] Further, the layered water injection process pipe column further comprises a screen pipe fixed to the tail end of the oil pipe.

[0018] Further, the layered water injection process pipe column further comprises a thread protector fixed to the tail end of the screen pipe.

[0019] Further, from the wellhead to the thread protector, the inner wall of the oil pipe is provided with a corrosion-resistant coating.

[0020] Further, from the casing protection packer to the thread protector, the outer wall of the oil pipe is provided with a corrosion-resistant coating.

[0021] In the second aspect, the application further provides a layered water injection process pipe column using method, which is based on the layered water injection process pipe column described above and sequentially comprises the following steps.

[0022] Pretreatment, the wellbore is treated through sand washing, well flushing, scraping and well washing processes to clean the wellbore;

[0023] Lowering the well pipe column: the assembled layered water injection process pipe column is lowered into the casing, wherein the expansion packer, the water well bidirectional anchor and the compression packer are lowered to a depth between the high-pressure water injection layer and the low-pressure water injection layer;

[0024] Seating the packer: water injection is performed in the oil pipe to gradually increase the pressure at different pressure points and stabilize the pressure for five minutes, and the pressure is not decreased to be qualified, until the casing protection packer and the compression packer are completely seated, then the pressure is continued to be increased until the pressure is suddenly decreased.

[0025] Opening the bridge type eccentric water distributor water injection channel: the steel wire fishing instrument is lowered to the position of the bridge type eccentric water distributor, and the plug is fished out after successful docking.

[0026] Measuring and adjusting water injection: first control the total well injection rate from the wellhead, according to the demand of layered injection distribution, adjust the water nozzle size of the bridge eccentric water distributor, adjust the injection rate of the low-pressure injection layer, until the injection rate of the low-pressure injection layer meets the requirements;

[0027] Sealing test: the double cup sealing tester is connected with the bridge eccentric water distributor, and then the sealing test is performed by changing the injection pressure.

[0028] Further, in the well completion string step, for the layered injection well with high-pressure injection layer on top and low-pressure injection layer on bottom, the casing protector packer, bridge eccentric water distributor, expansion packer, water well bidirectional anchor, compression packer, setting sliding sleeve, screen pipe and plug are sequentially threaded connected with the tubing on the ground, the threads are tightened, and sealing oil is evenly applied on the threads to form a layered injection process string.

[0029] For the layered injection well with high-pressure injection layer on top and low-pressure injection layer on bottom, the casing protector packer, constant pressure sliding sleeve, expansion packer, water well bidirectional anchor, compression packer, bridge eccentric water distributor, ball seat, screen pipe and plug are sequentially threaded connected with the tubing on the ground, the threads are tightened, and sealing oil is evenly applied on the threads to form a layered injection process string.

[0030] Further, during the water injection process, after the water nozzle is damaged, the fishing tool is lowered from the wellhead to fish out the damaged water nozzle, and then a new water nozzle is dropped into the corresponding position.

[0031] The layered injection process string provided by the above technical solutions can achieve the following technical effects:

[0032] The layered injection process string provided by the present application comprises a casing protector packer, an expansion packer, a water well bidirectional anchor and a compression packer; the casing protector packer, the expansion packer, the water well bidirectional anchor and the compression packer are sequentially and spacedly distributed along a straight line and connected by tubing to form a string for running into a casing; the casing protector packer is arranged outside the high-pressure injection layer and the low-pressure injection layer; the expansion packer, the water well bidirectional anchor and the compression packer are arranged between the high-pressure injection layer and the low-pressure injection layer.

[0033] In the layered water injection process string, the casing protection packer is mainly used to prevent the injected water from entering the annulus formed by the tubing and the casing above each packer during production; during normal water injection, the expansion type packer is in the set state, and is unsealed after stopping injection, so as to realize the auxiliary setting between the high-pressure water injection layer and the low-pressure water injection layer, and ensure the sealing effect under large pressure difference; the compression type packer plays a main setting role between the high-pressure water injection layer and the low-pressure water injection layer; the water well bidirectional anchor is between the expansion type packer and the compression type packer, that is, in the well section with the highest risk of packer failure, so that the creep of the lower string under large pressure difference injection can be effectively prevented, and the effectiveness of the setting of each packer is ensured.

[0034] It can be seen that, compared with the prior art, the layered water injection process string forms a combination of "bidirectional anchor + double packer" in the well section with the highest risk of packer failure through the cooperation of the water well bidirectional anchor, the expansion type packer and the compression type packer, which further improves the reliability of the setting of the string, and the layered water injection can be carried out smoothly under the action of each packer. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art of the present application, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 Application schematic diagram of the layered water injection process string provided by the embodiment of the present application in one pressure environment;

[0037] Figure 2 Application schematic diagram of the layered water injection process string provided by the embodiment of the present application in another pressure environment.

[0038] Legend: 1 - casing protection packer; 2 - expansion type packer; 3 - water well bidirectional anchor; 4 - compression type packer; 5 - tubing; 6 - casing; 7 - high-pressure water injection layer; 8 - low-pressure water injection layer; 9 - bridge type eccentric water distributor; 10 - landing sleeve; 11 - ball seat; 12 - constant pressure sliding sleeve; 13 - screen pipe; 14 - plug. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0041] Some embodiments of the application will be described in detail with reference to the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0042] In the layered water injection process, dynamic adjustment and single-layer start and stop need to be frequently performed, which will make the layered packer simultaneously bear the double effects of "large differential pressure + alternating differential pressure". In this pressure environment, the water injection string will produce a peristaltic effect, causing the rubber tube of the packer to gradually fail under the peristaltic effect. Once the layered sealing fails, the effective period of the water injection string will be greatly shortened, and the original layered water injection will be changed into general water injection, thereby causing problems such as under-injection or over-injection.

[0043] Therefore, the present application provides a layered water injection process string, which comprises a casing protection packer 1, an expansion type packer 2, a water well bidirectional anchor 3 and a compression type packer 4; the casing protection packer 1, the expansion type packer 2, the water well bidirectional anchor 3 and the compression type packer 4 are sequentially and spacedly distributed along a straight line and connected through a tubing 5 to form a string for running into a casing 6; the casing protection packer 1 is arranged outside the high-pressure water injection layer 7 and the low-pressure water injection layer 8; the expansion type packer 2, the water well bidirectional anchor 3 and the compression type packer 4 are arranged between the high-pressure water injection layer 7 and the low-pressure water injection layer 8.

[0044] In the layered water injection process string, the casing protection packer 1 is mainly used to prevent the injected water from entering the annulus formed by the tubing 5 and the casing 6 above each packer during production; in the normal water injection process, the expansion type packer 2 is in the set sealing state and is unsealed after stopping injection, thereby achieving auxiliary setting sealing between the high-pressure water injection layer 7 and the low-pressure water injection layer 8 and ensuring the sealing effect under large differential pressure; the compression type packer 4 plays a main setting sealing role between the high-pressure water injection layer 7 and the low-pressure water injection layer 8; the water well bidirectional anchor 3 is between the expansion type packer 2 and the compression type packer 4, i.e. in the well section with the greatest risk of packer failure, so that the peristalsis of the lower string under large differential pressure injection can be effectively prevented, and the effectiveness of the setting sealing of each packer is ensured.

[0045] It can be seen that, compared with the prior art, the layered water injection process string forms a combination of "double anchor + double packer" in the well section with the highest risk of packer failure through the cooperation of the water well double anchor 3, the expanding packer 2 and the compression packer 4, which further improves the reliability of the string setting. Under the action of each packer, layered water injection can be carried out smoothly.

[0046] The structure and shape of the layered water injection process string provided by the embodiment will be described in detail below. Figure 1 And Figure 2 The structure and shape of the layered water injection process string provided by the embodiment will be described in detail below.

[0047] In an embodiment of the present application, referring to Figure 1 , the layered water injection process string further comprises a bridge type eccentric water distributor 9, a sitting sliding sleeve 10, a screen pipe 13 and a plug 14; from top to bottom, the casing protection packer 1, the bridge type eccentric water distributor 9, the expanding packer 2, the water well double anchor 3, the compression packer 4, the sitting sliding sleeve 10 and the screen pipe 13 are sequentially distributed, each tool is connected through the tubing 5, and the plug 14 is fixed to the tail end of the screen pipe 13. The sitting sliding sleeve 10 is used in conjunction with the compression packer 4, and the main function is to keep the downhole string unobstructed after the compression packer 4 is set and pressed, and the screen pipe 13 and the plug 14 constitute the tail pipe part of the process string, wherein the screen pipe 13 is used to filter dirty things in the casing 6 to prevent backflow into the tubing 5, and the plug 14 plays a role in maintaining the tubing to prevent falling objects from falling. It needs to be supplemented here that each tool is of existing structure.

[0048] In the above, the layered water injection process string is suitable for layered water injection wells with high-pressure injection layer 7 below and low-pressure injection layer 8 above. Specifically, when the casing 6 is lowered, the casing protection packer 1 is above the low-pressure injection layer 8, the bridge type eccentric water distributor 9 is in the low-pressure injection layer 8, the expanding packer 2, the water well double anchor 3 and the compression packer 4 are between the high-pressure injection layer 7 and the low-pressure injection layer 8, and the sitting sliding sleeve 10 is in the high-pressure injection layer 7.

[0049] Continuing the above, when injecting water, water is injected into the tubing 5 and gradually increased and stabilized at different pressure points for five minutes. The pressure is not decreased until the casing protection packer 1 and the compression packer 4 are completely set and pressed, then the pressure is continuously pressed until the pressure suddenly drops, at which time the sitting sliding sleeve 10 is opened; then the wireline fishing instrument is lowered to the position of the bridge type eccentric water distributor 9, and after the two are successfully connected, the plug is fished out, and the water injection channel is opened; the injected water is injected from the ground through the tubing 5, part of the injected water enters the low-pressure injection layer 8 through the water injection channel of the bridge type eccentric water distributor 9, and the other part of the injected water enters the annular space formed by the tubing 5 and the casing 6 through the sitting sliding sleeve 10 and the screen pipe 13, and finally enters the high-pressure injection layer 7 under the action of the pressure difference.

[0050] In the above design, the low-cost sliding sleeve technology is used for non-throttling injection of the high-pressure injection layer 7, and the bridge-type eccentric water distributor 9 with replaceable water nozzle is used for injection in the low-pressure injection layer 8, thereby improving the injection property of the high-pressure injection layer 7 and solving the problems of easy damage and easy blockage of the water nozzle in the low-pressure injection layer 8.

[0051] In another embodiment, referring to Figure 2 , the layered water injection process string further comprises a ball seat 11, a bridge-type eccentric water distributor 9, a constant-pressure sliding sleeve 12, a screen pipe 13 and a plug 14; from top to bottom, the casing protection packer 1, the constant-pressure sliding sleeve 12, the expansion-type packer 2, the water well bidirectional anchor 3, the compression-type packer 4, the bridge-type eccentric water distributor 9, the ball seat 11 and the screen pipe 13 are sequentially distributed, the tools are connected through the oil pipe 5, and the plug 14 is fixed at the tail end of the screen pipe 13. The ball seat 11 is mainly used for packer setting and constant-pressure sliding sleeve 12 opening, the constant-pressure sliding sleeve 12 is used in conjunction with the compression-type packer 4, and the main function is to continue to lift the pressure to cut off the pin after the compression-type packer 4 is pressed and set, and to open the channel between the high-pressure injection layer 7. It needs to be supplemented here that each tool is of an existing structure.

[0052] In the above, the layered water injection process string is suitable for layered water injection wells with the high-pressure injection layer 7 above and the low-pressure injection layer 8 below. Specifically, when the casing 6 is lowered, the casing protection packer 1 is above the high-pressure injection layer 7, the constant-pressure sliding sleeve 12 is in the high-pressure injection layer 7, the expansion-type packer 2, the water well bidirectional anchor 3 and the compression-type packer 4 are between the high-pressure injection layer 7 and the low-pressure injection layer 8, the bridge-type eccentric water distributor 9 is in the low-pressure injection layer 8, and the ball seat 11 is below the low-pressure injection layer 8.

[0053] Continuing the above, when injecting water, water is injected into the oil pipe 5 to pressurize, the pressure is gradually increased at different pressure points and stabilized for five minutes, and the pressure is not reduced to be qualified, until the casing protection packer 1 and the compression-type packer 4 are completely set, then continue to pressurize until the pressure suddenly drops, at this time the pin of the constant-pressure sliding sleeve 12 is cut off, and the constant-pressure sliding sleeve 12 is opened; then the wireline fishing instrument is lowered to the position of the bridge-type eccentric water distributor 9, after the two are successfully connected, the plug is fished out, and the water injection channel is opened; the injected water is injected from the ground through the oil pipe 5, part of the injected water enters the annular space formed by the oil pipe 5 and the casing 6 through the constant-pressure sliding sleeve 12, and finally enters the high-pressure injection layer 7 under the action of pressure difference, and the other part of the injected water enters the low-pressure injection layer 8 through the water injection channel of the bridge-type eccentric water distributor 9.

[0054] Further, the inner wall and the outer wall of the oil pipe 5 below the casing protection packer 1 are both subjected to corrosion prevention process to form a corrosion prevention coating, and only the inner wall of the oil pipe 5 above the casing protection packer 1 is subjected to corrosion prevention process to form a corrosion prevention coating. Such design ensures that the section of the oil pipe 5 in contact with water can be corrosion and scale prevention, and in addition, the different settings of the inner wall and the outer wall of the oil pipe 5 save costs.

[0055] The layered water injection process pipe column uses method provided by the application, based on the layered water injection process pipe column, in embodiment one, as shown in the figure, for the layered water injection well with high pressure water injection layer 7 below and low pressure water injection layer 8 above, the method sequentially comprises the following steps: Figure 1

[0056] The first step: pretreatment. Before the layered water injection process pipe column is lowered into the casing 6, the wellbore is treated by sand washing, well flushing, scraping, well washing and other processes to clean the wellbore.

[0057] The second step: completion pipe column lowering. The casing packer 1, bridge type eccentric water distributor 9, expansion type packer 2, water well bidirectional anchor 3, compression type packer 4, landing sliding sleeve 10, screen pipe 13, plug 14 and tubing 5 are threadedly connected one by one on the ground, the threads are tightened, and sealing oil is evenly applied at the threads, wherein the expansion type packer 2, water well bidirectional anchor 3 and compression type packer 4 are lowered to a depth between the high pressure water injection layer 7 and the low pressure water injection layer 8.

[0058] The third step: packer setting. The tubing 5 is pressurized for water injection, the pressure is gradually increased and stabilized for five minutes at different pressure points, and the pressure is not decreased until the casing packer 1 and the compression type packer 4 are completely set, then the pressure is continued to be increased until the pressure is suddenly decreased, at this time the landing sliding sleeve 10 is opened.

[0059] The fourth step: opening the water injection channel of the bridge type eccentric water distributor 9. The wireline fishing instrument is lowered to the position of the bridge type eccentric water distributor 9, the interface is successfully connected, and the plug is fished out to open the water injection channel; after the water is injected from the ground through the tubing 5, part of the injected water enters the low pressure water injection layer 8 through the water injection channel of the bridge type eccentric water distributor 9, and the other part of the injected water enters the annular space formed by the tubing 5 and the casing 6 through the landing sliding sleeve 10 and the screen pipe 13, and finally enters the high pressure water injection layer 7 under the action of pressure difference.

[0060] The fifth step: measuring and adjusting water injection. First, control the total well injection amount from the wellhead, adjust the water nozzle size of the bridge type eccentric water distributor 9 according to the layered injection requirement, and adjust the injection amount of the low pressure water injection layer 8, when the injection amount of the low pressure water injection layer 8 meets the requirement, the high pressure water injection layer 7 will also meet the injection requirement. It needs to be explained here that during normal water injection, the expansion type packer 2 is set under the action of pressure difference, and plays an auxiliary sealing role, and after stopping injection, the rubber cylinder is retracted to be unsealed.

[0061] The sixth step: seal verification. The seal verification method is the same as that of the conventional layered water injection process pipe column, after the double cup seal verification instrument is lowered to the position of the bridge type eccentric water distributor 9 and the interface is connected, the seal is verified by changing the injection pressure.

[0062] ​Step 7: Replace the water nozzle. The water injection layer corresponding to the bridge-type eccentric water distributor 9 is the low-pressure water injection layer 8. The pressure difference before and after the water nozzle of the water distributor is large, and it is easily damaged under the impact of high-pressure jet for a long time. However, the water nozzle of the bridge-type eccentric water distributor 9 can be replaced at any time. The damaged water nozzle can be retrieved by lowering the dropper into the wellhead, and then the new water nozzle can be put into the corresponding position.

[0063] In Example 2, as Figure 2 As shown, for a stratified water injection well with high-pressure water injection layer 7 on top and low-pressure water injection layer 8 below, the first step of this method is the same as in Example 1; in the second step, the casing packer 1, constant pressure sliding sleeve 12, expansion packer 2, water well bidirectional anchor 3, compression packer 4, bridge-type eccentric water distributor 9, ball seat 11, screen pipe 13, threaded plug 14 and oil pipe 5 are connected one by one by thread on the ground, the threads are tightened, and sealing oil is evenly applied to the threads; in the third step, the pressure is continued until the pressure drops sharply, at which point the pin of constant pressure sliding sleeve 12 is sheared, and constant pressure sliding sleeve 12 is opened; the fourth, fifth, sixth and seventh steps are the same as in Example 1.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A layered water injection workstring, characterized in that, It comprises: A casing protector packer (1), an expansion packer (2), a water well bidirectional anchor (3) and a compression packer (4); The casing protector packer (1), the expansion packer (2), the water well bidirectional anchor (3) and the compression packer (4) are sequentially and spacedly arranged along a straight line and connected by a tubing (5) to form a pipe column for lowering into a casing (6); The casing protector packer (1) is arranged outside the high-pressure water injection layer (7) and the low-pressure water injection layer (8); The expansion packer (2), the water well bidirectional anchor (3) and the compression packer (4) are arranged between the high-pressure water injection layer (7) and the low-pressure water injection layer (8).

2. The layered water injection process pipe column according to claim 1, wherein, The layered water injection process pipe column further comprises a bridge eccentric water distributor (9) and a sitting sliding sleeve (10); The bridge eccentric water distributor (9) is fixed to the tubing (5) and located between the casing protector packer (1) and the expansion packer (2) for being arranged in the low-pressure water injection layer (8); The sitting sliding sleeve (10) is fixed to the tubing (5) and located on the side of the compression packer (4) away from the water well bidirectional anchor (3) for being arranged in the high-pressure water injection layer (7).

3. The layered water injection process pipe column according to claim 1, wherein, The layered water injection process pipe column further comprises a ball seat (11), a bridge eccentric water distributor (9) and a constant pressure sliding sleeve (12); The ball seat (11) is fixed to the tubing (5) and located on the side of the compression packer (4) away from the water well bidirectional anchor (3) for being arranged outside the high-pressure water injection layer (7) and the low-pressure water injection layer (8); The bridge eccentric water distributor (9) is fixed to the tubing (5) and located between the ball seat (11) and the compression packer (4) for being arranged in the low-pressure water injection layer (8); The constant pressure sliding sleeve (12) is fixed to the tubing (5) and located between the casing protector packer (1) and the expansion packer (2) for being arranged in the high-pressure water injection layer (7).

4. The layered water injection process pipe column according to any one of claims 1 to 3, wherein, The layered water injection process pipe column further comprises a screen pipe (13) fixed to the tail end of the tubing (5).

5. The layered water injection process pipe column according to claim 4, wherein, The layered water injection process pipe column further comprises a thread protector (14) fixed to the tail end of the screen pipe (13).

6. The layered water injection process pipe column according to claim 5, wherein, From the wellhead to the thread protector (14), the inner wall of the tubing (5) is provided with a corrosion-resistant coating.

7. The layered water injection process pipe column according to claim 6, wherein, From the casing protector packer (1) to the thread protector (14), the outer wall of the tubing (5) is provided with a corrosion-resistant coating.

8. A method of using a layered water injection string, comprising: Based on the layered water injection process pipe column according to any one of claims 1 to 7, the following steps are sequentially included: The wellbore is treated by sand washing, wellbore cleaning, scraping and wellbore washing to clean the wellbore; Lowering the completion string: the assembled layered water injection string is lowered into the casing (6), wherein the expansion packer (2), the water well bidirectional anchor (3) and the compression packer (4) are lowered to a depth between the high-pressure water injection layer (7) and the low-pressure water injection layer (8); Setting the packer: water is injected into the tubing (5) to pressurize, the pressure is gradually increased at different pressure points and stabilized for five minutes, and the pressure is not decreased to be qualified, until the casing protection packer (1) and the compression packer (4) are completely set, then the pressure is continued to be increased until the pressure is suddenly decreased; Opening the bridge-type eccentric water distributor (9) water injection channel: the wireline fishing instrument is lowered to the position of the bridge-type eccentric water distributor (9), and the packer is fished out after successful docking; Measuring and adjusting water injection: first, the total well injection amount is controlled at the wellhead, and then the water nozzle size of the bridge-type eccentric water distributor (9) is adjusted to adjust the injection amount of the low-pressure water injection layer (8) until the injection amount of the low-pressure water injection layer (8) meets the requirements; Sealing test: the double-poppet sealing test instrument is lowered to the position of the bridge-type eccentric water distributor (9), and then the sealing test is performed by changing the injection pressure.

9. The layered water injection string use method according to claim 8, wherein, in the step of lowering the completion string, for a layered water injection well with a high-pressure water injection layer (7) above and a low-pressure water injection layer (8) below, the casing protection packer (1), the bridge-type eccentric water distributor (9), the expansion packer (2), the water well bidirectional anchor (3), the compression packer (4), the landing sleeve (10), the screen pipe (13) and the nipple (14) are sequentially screwed with the tubing (5) on the ground, the nipple is tightened, and sealing oil is evenly applied to the nipple to form the layered water injection string; For a layered water injection well with a high-pressure water injection layer (7) above and a low-pressure water injection layer (8) below, the casing protection packer (1), the constant-pressure sliding sleeve (12), the expansion packer (2), the water well bidirectional anchor (3), the compression packer (4), the bridge-type eccentric water distributor (9), the ball seat (11), the screen pipe (13) and the nipple (14) are sequentially screwed with the tubing (5) on the ground, the nipple is tightened, and sealing oil is evenly applied to the nipple to form the layered water injection string.

10. The layered water injection string use method according to claim 8, wherein, during water injection, the damaged water nozzle is fished out by lowering the fishing instrument from the wellhead, and then a new water nozzle is dropped into the corresponding position. ​ ​

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