Sampler, sampling tubular column and sampling method for deep monitoring well

Abstract

The invention discloses a sampler for a deep monitoring well, a sampling tubular column and a sampling method. The technical problems that in the prior art, a liquid sample is difficult to lift, stratified sampling is difficult and the like are solved. The sampler comprises an upper joint, a sampling main body, a threading coupling, a screen pipe nipple and a lower joint, wherein a sampling cavity for storing a liquid sample is formed in the sampling main body; the sampling main body is connected with the screen pipe nipple through a sampling pipeline; a one-way valve is arranged on the sampling pipeline; a pressurizing pipeline and a lifting pipeline are connected to the sampling main body, the pressurizing pipeline is used for being connected with external pressurizing equipment, the lifting pipeline is used for being connected with external collecting equipment, and a liquid sample in the sampling cavity can be discharged into the external collecting equipment through pressurizing. According to the invention, stratified sampling can be realized, packing between adjacent sampling layers can be ensured, the interlayer sealing performance can be verified, movable wellhead operations such as immovable tubular column sampling and no need of steel wire throwing and fishing can be realized, the workload is small, the sampling depth is larger, and pollution-free sampling can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of reinjection monitoring well completion technology, and in particular relates to a sampler, a sampling pipe string and a sampling method for a deep monitoring well. Background Art

[0002] Fracturing technology is one of the primary methods for increasing oilfield production and is widely used by major oilfields. During the fracturing process, a large amount of fracturing flowback fluid is produced. This fluid contains organic polymers used for fracturing, support sand or ceramsite, crude oil produced from the formation, seepage water, infiltrated rock debris, and various saprophytic bacteria in the formation. Currently, the most common method for disposing of fracturing flowback fluid is to reinject it into the formation after sewage treatment.

[0003] In order to ensure that the reinjected water does not pollute other aquifers, it is necessary to sample and analyze the formation water in the reinjection area through a sampling device to obtain data on the impact of the reinjected water on the groundwater, thereby providing a basis for the environmental evaluation of the reinjection.

[0004] At present, the sampling operations and sampling devices in related technologies have the following technical difficulties and problems:

[0005] (1) The formation energy is insufficient and does not meet the conditions for using large lifting equipment (rod pumps, electric submersible pumps, etc.);

[0006] (2) Monitoring wells are deeper than conventional geothermal wells and water source wells. Traditional wireline casting or shallow multi-tube sampling and monitoring techniques are not suitable for reinjection monitoring wells in the oil industry;

[0007] (3) There are many layers in the well, which requires stratified sampling. It requires absolute isolation between layers and a certain means of verifying the isolation effect. The existing sampling equipment and sampling operations do not meet the requirements of stratified sampling in the well. Summary of the Invention

[0008] In order to solve all or part of the above problems, the purpose of the present invention is to provide a sampler, sampling string and sampling method for deep monitoring wells, which can realize layered sampling, ensure the sealing between adjacent sampling layers, and verify the interlayer sealing. It can also realize static string sampling, without the need for dynamic wellhead operations such as wire casting and fishing, with a small workload, a greater sampling depth, and pollution-free sampling.

[0009] In a first aspect, the present invention provides a sampler for a deep monitoring well, comprising an upper joint, a sampling body, a threading coupling, a screen tube nipple, and a lower joint connected in sequence from top to bottom, wherein a sampling cavity for storing a liquid sample is provided in the sampling body;

[0010] The sampling body is connected to the screen tube nipple through a sampling pipeline, and the formation fluid filtered by the screen tube nipple can enter the sampling cavity through the sampling pipeline. A one-way valve is provided on the sampling pipeline to restrict the formation fluid from entering the sampling cavity.

[0011] The sampling body is connected to a pressure pipeline and a lifting pipeline. The pressure pipeline is used to connect to an external boosting device, and the lifting pipeline is used to connect to an external collection device. The liquid sample in the sampling cavity can be discharged into the external collection device through pressure.

[0012] Optionally, the sampling body includes a sampling inner cylinder and a sampling outer cylinder that are concentrically fixedly connected, and a ring-shaped sampling cavity is formed between the sampling inner cylinder and the sampling outer cylinder. The sampling pipeline, pressure pipeline and lifting pipeline are respectively connected to the sampling outer cylinder and respectively communicated with the sampling cavity.

[0013] Optionally, a plurality of the sampling pipelines are provided, and the plurality of sampling pipelines are arranged at equal intervals along the circumference of the sampling body, and each of the sampling pipelines is provided with the one-way valve.

[0014] Optionally, a plurality of the sampling pipelines pass through the threading couplings respectively.

[0015] Optionally, a check valve is provided on the lifting line to limit the liquid sample to be discharged only through the lifting line.

[0016] In a second aspect, the present invention provides a sampling string for a deep monitoring well, comprising three samplers and further comprising:

[0017] A completion string is used to be run into the casing, and the three samplers are respectively connected to the completion string;

[0018] a production packer connected to the completion string;

[0019] an upper isolation packer connected to the completion string and located below the production packer;

[0020] a lower isolation packer connected to the completion string and located below the upper isolation packer;

[0021] An opening sliding sleeve is connected to the completion string and is located between the upper isolation packer and the lower isolation packer;

[0022] closing the sliding sleeve and connecting it to the bottom of the completion string;

[0023] There are three inlet pipelines, one end of each inlet pipeline is connected to the pressure pipeline on the corresponding sampler, and the other end is connected to the external pressurizing equipment;

[0024] There are three outlet pipelines, one end of each outlet pipeline is connected to the lifting pipeline on the corresponding sampler, and the other end is connected to the external collection equipment;

[0025] Among them, the three samplers are arranged as an upper layer sampler, a middle layer sampler and a lower layer sampler from top to bottom. The upper layer sampler is located between the production packer and the upper isolation packer, the middle layer sampler is located between the upper isolation packer and the opening sleeve, and the lower layer sampler is located below the lower isolation packer.

[0026] In a third aspect, the present invention provides a method for sampling a deep monitoring well using a sampling device, comprising the following steps:

[0027] S1, position and tool determination;

[0028] S2, assembling the tubing string;

[0029] S3, lower into the pipe string;

[0030] S4, packer setting;

[0031] S5, interlayer sealing inspection;

[0032] S6, empty the pipeline;

[0033] S7, formation fluid sampling;

[0034] S8, liquid sample lifting.

[0035] Optionally, in S1, the depths of the three perforation sections in the wellbore are determined, and a piping table is determined based on the depths of the perforation sections to ensure that after the sampling string is lowered into the wellbore, the three samplers are respectively located at upper positions in the corresponding perforation sections, the upper isolation packer and the lower isolation packer are located between two adjacent perforation sections, and the production packer is located 10 m to 20 m above the top depth of the uppermost perforation section in the wellbore.

[0036] Optionally, in S4, a pressure steel ball with a ball diameter of 36 mm is put into the sampling string, and the sampling string is gradually pressurized by 3.5 MPa×5 min, 10.5 MPa×5 min, and 21.0 MPa×15 min through an external pressure device, so that the lower isolation packer, the upper isolation packer, and the production packer are successively sealed.

[0037] Optionally, in S5, the sampling string is pressurized by an external pressurizing device at 25 MPa for 5 minutes to control the opening of the opening sleeve. If the pressure in the sampling string suddenly drops, it proves that the opening sleeve is open. Otherwise, the pressurizing operation is repeated until the opening sleeve is opened.

[0038] Use an external pressure device to gradually pressurize the sampling string at 3.5 MPa for 5 minutes and 7.0 MPa for 10 minutes. If the outlet pipelines of the upper and lower samplers do not continuously discharge liquid, but the outlet pipeline of the middle sampler continuously discharges liquid, it proves that the upper and lower isolation packers have passed the sealing test. Otherwise, re-execute S4 and verify until the upper and lower isolation packers pass the sealing test.

[0039] Use the external pressure device to gradually pressurize the wellbore annulus at 3.5 MPa × 5 min and 7.0 MPa × 10 min. If the pressure is stable and there is no continuous liquid discharge from the outlet pipeline of the upper sampler, it proves that the production packer has passed the seal inspection. Otherwise, re-execute S4 and verify until the production packer has passed the seal inspection.

[0040] Optionally, in S6, the three inlet pipelines are respectively connected to external boosting equipment, and the three inlet pipelines are pressurized to 20-30 MPa through the external boosting equipment, so that the liquid in the three sampling chambers is lifted to the wellhead through the corresponding outlet pipelines, until the discharge from the outlet pipeline is all gas and no mist is produced, then the pressurization is stopped and the pressure is relieved.

[0041] Optionally, in S7 , the formation fluid in each layer enters the corresponding screen tube pup joint under the action of formation pressure, and then enters the corresponding sampling cavity through the sampling pipeline for storage, so as to realize stratified sampling of the formation fluid.

[0042] Optionally, in S8, the three inlet pipelines are pressurized separately by an external pressurizing device, and the liquid samples in the three sampling chambers enter the corresponding external collecting devices through the outlet pipelines under the action of pressure, so as to realize the separate collection of liquid samples in each layer.

[0043] As can be seen from the above technical solutions, the sampler, sampling string and sampling method for deep monitoring wells provided by the present invention have the following advantages:

[0044] The sampler, sampling string and sampling method realize layered sampling, ensure the isolation between adjacent sampling layers, and verify the sealing between layers. It can also realize sampling without moving the string, without the need for dynamic wellhead operations such as wire casting and fishing, with a small workload, while the sampling depth is greater and pollution-free sampling can be achieved.

[0045] Other features and advantages of the present invention will be set forth in the description that follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0047] Figure 1This is a diagram showing the overall structure of the sampler in Example 1 of the present invention;

[0048] Figure 2 is a cross-sectional view of the sampler in Example 1 of the present invention;

[0049] Figure 3 is a cross-sectional view of the sampling body in Example 1 of the present invention;

[0050] Figure 4 Schematic diagram of the structure of the sampling column in Example 2 of the present invention;

[0051] Figure 5 Schematic diagram of the process of the sampling method in Example 3 of the present invention.

[0052] Description of reference numerals:

[0053] 1. Upper joint; 2. Sampling body; 21. Sampling inner tube; 22. Sampling outer tube; 3. Threading coupling; 4. Screen tube nipple; 5. Lower joint; 6. Sampling chamber; 7. Sampling pipeline; 8. One-way valve; 9. Pressure pipeline; 10. Lifting pipeline; 11. Check valve; 12. Completion string; 13. Production packer; 14. Upper layer sampler; 15. Upper isolation packer; 16. Middle layer sampler; 17. Opening sleeve; 18. Lower isolation packer; 19. Lower layer sampler; 20. Closing sleeve; 21. Inlet pipeline; 22. Outlet pipeline

[0054] 100. Sampler; 200. Sampling column. DETAILED DESCRIPTION

[0055] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other in any manner.

[0056] Example 1

[0057] like Figure 1 、 Figure 2 、 Figure 3 The figure shows embodiment 1 of the present invention, which discloses a sampler 100 for a deep monitoring well, including an upper joint 1, a sampling body 2, a threading coupling 3, a screen tube short section 4 and a lower joint 5 that are threadedly connected in sequence from top to bottom. The upper joint 1 and the lower joint 5 are used to connect to the external pipe string, the screen tube short section 4 is used to filter the formation fluid, and a sampling cavity 6 for storing liquid samples is provided in the sampling body 2.

[0058] In one embodiment, Figure 1 、 Figure 2As shown, the sampling body 2 is connected to the screen tube short section 4 through multiple sampling pipelines 7, and the multiple sampling pipelines 7 are arranged at equal intervals along the circumference of the sampling body 2, so that the formation fluid filtered by the screen tube short section 4 can enter the sampling cavity 6 through the multiple sampling pipelines 7.

[0059] In one embodiment, Figure 1 、 Figure 2 As shown, each sampling line 7 is provided with a one-way valve 8, which is used to restrict formation fluid from entering the sampling chamber 6 to ensure smooth sampling. At the same time, multiple sampling lines 7 are respectively passed through the threading coupling 3 to achieve position limiting and protection of the sampling lines 7.

[0060] In one embodiment, Figure 1 、 Figure 2 As shown, the sampling body 2 is connected to a pressure pipeline 9 and a lifting pipeline 10. The pressure pipeline 9 is used to connect to an external pressurizing device so that high-pressure gas can enter the sampling chamber 6. The lifting pipeline 10 is used to connect to an external collection device so that the liquid sample in the sampling chamber 6 can be discharged into the external collection device through pressure.

[0061] In one embodiment, Figure 2 、 Figure 3 As shown, the sampling body 2 includes a concentrically fixed sampling inner cylinder 21 and a sampling outer cylinder 22, forming an annular sampling chamber 6 between the sampling inner cylinder 21 and the sampling outer cylinder 22. At the same time, the sampling line 7, the pressure line 9, and the lifting line 10 are respectively connected to the sampling outer cylinder 22, and the sampling line 7, the pressure line 9, and the lifting line 10 are respectively connected to the sampling chamber 6.

[0062] In one embodiment, Figure 1 、 Figure 2 As shown, a check valve 11 is provided on the lifting pipeline 10 , and the check valve 11 is used to limit the liquid sample to be discharged only through the lifting pipeline 10 , so as to ensure the smooth collection of the liquid sample.

[0063] In the sampler of this embodiment, when the formation liquid enters the sampling chamber 6, the liquid sample in the sampling chamber 6 can be lifted by pressurizing to ensure the smooth collection of the liquid sample. This design can realize sampling without moving the pipe string, and there is no need for moving wellhead operations such as wire casting and fishing, which reduces the workload and reduces the burden on the staff.

[0064] Example 2

[0065] like Figure 4The figure shows embodiment 2 of the present invention, which discloses a sampling string 200 for a deep monitoring well, including three samplers 100 in embodiment 1. The sampling string 200 also includes a completion string 12 for being lowered into the casing. The three samplers 100 are connected to the completion string 12 in sequence, and the three samplers 100 are arranged from top to bottom as an upper layer sampler 14, a middle layer sampler 16 and a lower layer sampler 19.

[0066] In one embodiment, Figure 4 As shown, the completion string 12 is connected to a production packer 13, an upper layer sampler 14, an upper isolation packer 15, a middle layer sampler 16, an opening sleeve 17, a lower isolation packer 18, a lower layer sampler 19 and a closing sleeve 20 from top to bottom.

[0067] In one embodiment, Figure 4 As shown, the sampling column 200 also includes three inlet pipelines 21 and three outlet pipelines 22. One end of each inlet pipeline 21 is connected to the pressure pipeline 9 on the corresponding sampler 100, and the other end is connected to the external boosting equipment. One end of each outlet pipeline 22 is connected to the lifting pipeline 10 on the corresponding sampler 100, and the other end is connected to the external collection equipment.

[0068] In this embodiment, the closing sleeve 20 utilizes a ball-dropping type. When the sampling string 200 is lowered into the casing, the closing sleeve 20 remains open, providing a balanced pressure channel between the inside and outside of the tubing, ensuring the ease of lowering the sampling string 200 and providing a well control channel. Once the sampling string 200 is properly lowered, a ball is dropped into the wellhead. Subsequently, pressure is applied to control the closing sleeve 20, thereby building up high pressure within the sampling string 200 to ensure the packer can function. Ball-dropping type closing sleeves are conventional technology and will not be described in detail here.

[0069] In this embodiment, the opening sleeve 17 is a pressure-operated opening sleeve. When the sampling string is lowered into the casing, the opening sleeve 17 remains closed. When opening is required, the pressure within the sampling string 200 is built up to a preset pressure. Pressure-operated opening sleeves are conventional technology and will not be described in detail here. In this embodiment, the opening pressure of the opening sleeve 17 is higher than the setting pressure of the packer. That is, the packer is set first, and then the opening sleeve 17 is opened.

[0070] In this embodiment, the production packer 13 and the upper isolation packer 15 each utilize a wireline packer to ensure interlayer sealing without compromising isolation effectiveness. The inlet and outlet pipelines 21 and 22 each utilize 1 / 4" control lines. Their narrow internal passages effectively minimize gas cross-flow, ensuring smooth and safe sampling.

[0071] The sampling string in this embodiment can realize layered sampling, ensure the isolation between adjacent sampling layers, and verify the sealing between layers. At the same time, a single trip of the string can realize multi-layer sampling operations of deep formation water, which is more practical.

[0072] Example 3

[0073] like Figure 4 The fifth embodiment of the present invention is shown. This embodiment discloses a sampling method for a deep monitoring well. Using the sampling string 200 in the second embodiment, the sampling method includes the following steps:

[0074] S1, position and tool determination;

[0075] S2, assembling the tubing string;

[0076] S3, lower into the pipe string;

[0077] S4, packer setting;

[0078] S5, interlayer sealing inspection;

[0079] S6, empty the pipeline;

[0080] S7, formation fluid sampling;

[0081] S8, liquid sample lifting.

[0082] In S1, the depths of the three perforated sections in the wellbore are determined, and a piping table is determined based on the perforated section depths to ensure that after the sampling string 200 is lowered into the wellbore, the three samplers 100 are located at the upper positions within the corresponding perforated sections, the upper isolation packer 15 and the lower isolation packer 18 are located between two adjacent perforated layer sections, and the production packer 13 is located 10m-20m above the top depth of the topmost perforated section in the wellbore.

[0083] In S2, the components are connected in sequence to ensure that the production packer 13, upper layer sampler 14, upper isolation packer 15, middle layer sampler 16, opening sleeve 17, lower isolation packer 18, lower layer sampler 19 and closing sleeve 20 are arranged in sequence from top to bottom.

[0084] In S4, a pressure steel ball with a ball diameter of 36 mm is put into the sampling string 200, and the pressure is gradually applied to the sampling string 200 by an external pressure device at 3.5 MPa×5 min, 10.5 MPa×5 min, and 21.0 MPa×15 min, so that the lower isolation packer 18, the upper isolation packer 15, and the production packer 13 are successively sealed.

[0085] In S5, the sampling column 200 is pressurized by an external pressure device at 25 MPa for 5 minutes to control the opening of the opening sleeve 17. If the pressure in the sampling column 200 suddenly drops, it proves that the opening sleeve 17 is open. Otherwise, the pressure operation is repeated until the opening sleeve 17 is opened.

[0086] The sampling string 200 is gradually pressurized with an external pressure device at 3.5 MPa for 5 minutes and 7.0 MPa for 10 minutes. If the outlet pipelines 22 of the upper layer sampler 14 and the lower layer sampler 19 do not continuously discharge liquid, and the outlet pipeline 22 of the middle layer sampler 16 continuously discharges liquid, it is confirmed that the upper isolation packer 15 and the lower isolation packer 18 have passed the sealing test. Otherwise, S4 is repeated and verified until the upper isolation packer 15 and the lower isolation packer 18 have passed the sealing test.

[0087] The wellbore annulus is gradually pressurized by an external pressure device at 3.5 MPa×5 min and 7.0 MPa×10 min. If the pressure is normally stable and the outlet pipeline 22 of the upper sampler 14 does not continuously discharge liquid, it proves that the production packer 13 has passed the sealing test. Otherwise, re-execute S4 and verify until the production packer 13 has passed the sealing test.

[0088] In S6, the three inlet pipelines 21 are respectively connected to external pumping equipment, and the three inlet pipelines 21 are respectively pressurized to 20-30Mpa through the external pumping equipment, so that the liquid in the three sampling chambers 6 is lifted to the wellhead through the corresponding outlet pipelines 22. When the discharge from the outlet pipelines 22 is all gas and no mist is produced, the pressurization is stopped and the pressure is released.

[0089] In S7 , the formation fluid in each layer enters the corresponding screen tube sub 4 under the action of formation pressure, and then enters the corresponding sampling cavity 6 through the sampling pipeline 7 for storage, so as to realize stratified sampling of the formation fluid.

[0090] In S8, the three inlet pipelines 21 are pressurized separately by an external pressurizing device, and the liquid samples in the three sampling chambers 6 enter the corresponding external collecting devices through the outlet pipelines 22 under the action of pressure, so as to realize the separate collection of liquid samples in each layer.

[0091] From the above, it can be seen that the sampler, sampling column and sampling method have the following advantages:

[0092] (1) Layered sampling can be performed to achieve absolute isolation between layers and verify the sealing between layers;

[0093] (2) By pressurizing the surface pipeline, the liquid sample can be lifted to the wellhead, realizing the sampling without moving the pipe string, without the need for wireline casting and other moving wellhead operations, which reduces the workload and improves the efficiency;

[0094] (3) The sampling depth is large, and sampling can be achieved at a well depth of 3000m;

[0095] (4) When the formation liquid enters the sampler, it flows in one direction to prevent the liquid sample from flowing back.

[0096] (5) Through specific sampling operation methods, pollution-free sampling of formation samples can be achieved.

[0097] It should be noted that, unless otherwise specified, the technical or scientific terms used in the present invention should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0098] In addition, the terms "upper", "lower", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A sampler for a deep monitoring well, characterized in that: The device comprises an upper joint (1), a sampling body (2), a threading coupling (3), a screen tube short section (4), and a lower joint (5) which are sequentially connected from top to bottom. A sampling cavity (6) for storing liquid samples is provided in the sampling body (2); The sampling body (2) is connected to the screen tube nipple (4) via a sampling line (7), and the formation fluid filtered by the screen tube nipple (4) can enter the sampling cavity (6) through the sampling line (7). A one-way valve (8) is provided on the sampling line (7) to restrict the formation fluid from entering the sampling cavity (6). The sampling body (2) is connected to a pressure pipeline (9) and a lifting pipeline (10), wherein the pressure pipeline (9) is used to be connected to an external pressurizing device, and the lifting pipeline (10) is used to be connected to an external collecting device, and the liquid sample in the sampling cavity (6) can be discharged into the external collecting device through pressure.

2. The sampler according to claim 1, characterized in that The sampling body (2) comprises a sampling inner cylinder (21) and a sampling outer cylinder (22) which are concentrically fixedly connected. An annular sampling cavity (6) is formed between the sampling inner cylinder (21) and the sampling outer cylinder (22). The sampling pipeline (7), the pressure pipeline (9) and the lifting pipeline (10) are respectively connected to the sampling outer cylinder (22) and are respectively communicated with the sampling cavity (6).

3. The sampler according to claim 1, characterized in that A plurality of the sampling pipelines (7) are provided, and the plurality of sampling pipelines (7) are arranged at equal intervals along the circumference of the sampling body (2), and each of the sampling pipelines (7) is provided with a one-way valve (8).

4. The sampler according to claim 3, characterized in that The plurality of sampling pipelines (7) pass through the threading couplings (3) respectively.

5. The sampler according to claim 1, characterized in that A check valve (11) is provided on the lifting line (10) to limit the liquid sample to be discharged only through the lifting line (10).

6. A sampling string for a deep monitoring well, comprising three samplers (100) according to any one of claims 1 to 5, characterized in that: Also includes: A completion string (12) is used to be lowered into the casing, and the three samplers (100) are respectively connected to the completion string (12); a production packer (13) connected to the completion string (12); an upper isolation packer (15), connected to the completion string (12) and located below the production packer (13); a lower isolation packer (18) connected to the completion string (12) and located below the upper isolation packer (15); An opening sliding sleeve (17) is connected to the completion string (12) and is located between the upper isolation packer (15) and the lower isolation packer (18); A closing sliding sleeve (20) is connected to the bottom of the completion string (12); There are three inlet pipelines (21), one end of each inlet pipeline (21) is connected to the pressure pipeline (9) on the corresponding sampler (100), and the other end is connected to an external pressurizing device; There are three outlet pipelines (22), one end of each outlet pipeline (22) is connected to the lifting pipeline (10) on the corresponding sampler (100), and the other end is connected to an external collection device; The three samplers (100) are sequentially arranged from top to bottom as an upper layer sampler (14), a middle layer sampler (16) and a lower layer sampler (19), the upper layer sampler (14) is located between the production packer (13) and the upper isolation packer (15), the middle layer sampler (16) is located between the upper isolation packer (15) and the opening sleeve (17), and the lower layer sampler (19) is located below the lower isolation packer (18).

7. A sampling method for a deep monitoring well, using the sampling string (200) according to claim 6, characterized in that: The steps include: S1, position and tool determination; S2, assembling the tubing string; S3, lower into the pipe string; S4, packer setting; S5, interlayer sealing inspection; S6, empty the pipeline; S7, formation fluid sampling; S8, liquid sample lifting.

8. The sampling method according to claim 7, characterized in that: In S1, the depths of the three perforation sections in the wellbore are determined, and a piping table is determined according to the depths of the perforation sections to ensure that after the sampling string (200) is lowered into the wellbore, the three samplers (100) are respectively located at the upper position in the corresponding perforation section, the upper isolation packer (15) and the lower isolation packer (18) are located between two adjacent perforation sections, and the production packer (13) is located 10m-20m above the top depth of the topmost perforation section in the wellbore.

9. The sampling method according to claim 7, characterized in that: In S4, a pressure steel ball with a ball diameter of 36 mm is introduced, and the sampling string (200) is gradually pressurized by 3.5 MPa×5 min, 10.5 MPa×5 min, and 21.0 MPa×15 min through an external pressure device, so that the lower isolation packer (18), the upper isolation packer (15), and the production packer (13) are set in sequence.

10. The sampling method according to claim 7, characterized in that: In S5, the sampling column (200) is pressurized by an external pressurizing device at 25 MPa for 5 minutes to control the opening of the opening sleeve (17). If the pressure in the sampling column (200) suddenly drops, it proves that the opening sleeve (17) is opened. Otherwise, the pressurizing operation is repeated until the opening sleeve (17) is opened. The sampling string (200) is gradually pressurized by an external pressure device at 3.5 MPa×5 min and 7.0 MPa×10 min. If the outlet pipelines (22) of the upper layer sampler (14) and the lower layer sampler (19) do not continuously discharge liquid, and the outlet pipeline (22) of the middle layer sampler (16) continuously discharges liquid, it is proved that the upper isolation packer (15) and the lower isolation packer (18) have passed the sealing test. Otherwise, S4 is re-executed and verified until the upper isolation packer (15) and the lower isolation packer (18) have passed the sealing test. The wellbore annulus is gradually pressurized by an external pressure device at 3.5 MPa×5 min and 7.0 MPa×10 min. If the pressure is normally stabilized and the outlet pipeline (22) of the upper layer sampler (14) does not continuously discharge liquid, it is proved that the production packer (13) has passed the sealing test. Otherwise, S4 is re-executed and verified until the production packer (13) has passed the sealing test.

11. The sampling method according to claim 7, characterized in that: In S6, the three inlet pipelines (21) are connected to external boosting equipment respectively, and the three inlet pipelines (21) are pressurized to 20-30 MPa respectively by the external boosting equipment, so that the liquid in the three sampling chambers (6) is lifted to the wellhead through the corresponding outlet pipelines (22) respectively, until the discharge from the outlet pipelines (22) is all gas and no mist is produced, then the pressurization is stopped and the pressure is released.

12. The sampling method according to claim 7, characterized in that: In S7, the formation fluid of each layer enters the corresponding screen tube short section (4) under the action of the formation pressure, and then enters the corresponding sampling cavity (6) through the sampling pipeline (7) for storage, so as to realize the layered sampling of the formation fluid.

13. The sampling method according to claim 7, characterized in that: In S8, the three inlet pipelines (21) are pressurized separately by an external pressurizing device, and the liquid samples in the three sampling chambers (6) enter the corresponding external collection devices through the outlet pipelines (22) under the action of pressure, so as to realize the separate collection of liquid samples in each layer.

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