Open hole segmented well completion pipe string capable of achieving full open hole section natural productivity and using method of open hole segmented well completion pipe string

Abstract

The invention discloses an open hole segmented well completion pipe string capable of achieving full open hole section natural productivity and a using method of the open hole segmented well completion pipe string, and belongs to the technical field of oil and gas field downhole tools and technologies. Organic saline water, white oil or clear water can be displaced to the position above the suspension well completion integrated packer, and the equivalent density of the whole well after fluid displacement is not lower than that before fluid displacement, so that it is guaranteed that the fluid in a shaft has enough density to balance the formation pressure. A well completion integrated packer is hung through independent setting, and a switchable sliding sleeve is opened, so that a safety barrier for displacing fluid of a back-inserting tubular column section and natural blowout of a full-open-hole section is constructed; after the full open hole section natural blowout test, accurate control and management of each reservoir section are achieved by setting the open hole packer and closing the openable and closable sliding sleeve, and respective transformation of each reservoir section is achieved by operations such as opening the fracturing sliding sleeve step by step through a ball or a special opening tool (aiming at the openable and closable sliding sleeve), so that the reservoir transformation effect is improved.

Description

Technical Field

[0001] This invention belongs to the field of downhole tools and technology in oil and gas fields, specifically a segmented open-hole completion string with full open-hole natural production capacity and its usage method. Background Technology

[0002] Natural productivity testing of oil and gas reservoirs plays a crucial role in reservoir evaluation and stimulation operations. Through natural productivity testing, the original production capacity of the reservoir before stimulation can be determined, providing a basis for subsequent stimulation plans. Currently, open-hole segmented completion stimulation technology is widely used, but some shortcomings still exist in practical applications.

[0003] Existing open-hole segmented completion and stimulation techniques involve setting the suspended packer and open-hole packer simultaneously after the segmented tubing is inserted, thus separating different reservoir segments and using sliding sleeves between segments for differentiated stimulation. However, this tubing and technique can only test the natural productivity of the first segment after opening the first sliding sleeve, and cannot test the natural productivity of the entire open-hole segment. This means that during the stimulation process, it is impossible to fully understand the natural productivity of each reservoir segment, thus affecting the formulation and implementation of the stimulation plan.

[0004] Currently, the standard practice for testing the natural productivity of a full open-hole section is to run a separate test string before running the open-hole section tubing. While this method allows for testing the natural productivity of the entire open-hole section, it also introduces several problems. First, running a separate test string significantly increases operational risk, as it requires multiple downhole operations and connections, increasing the risk of equipment damage and personnel injury. Second, this approach also increases the operational cycle and cost, as it requires additional time and resources to complete the testing. Summary of the Invention

[0005] This invention provides an open-hole segmented completion string for full open-hole natural production capacity and its usage method, which solves the problem of high risk in running a test string separately before running the open-hole segmented completion string for full open-hole natural production capacity testing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A fully open-hole segmented completion string with natural production capacity includes an insertion string and a return string; The delivery string includes an open hole and a casing connected to each other. The open hole and casing are equipped with tubing. From the open hole to the casing, the tubing is equipped with a guide shoe, a screen pipe, a three-backpressure valve, a self-sealing ball seat, a differential pressure sliding sleeve, a first open hole packer, a ball-dropping sliding sleeve, a second open hole packer, a switchable sliding sleeve, a suspended completion integrated packer, a return sleeve, and a delivery tool. The insertion string is sequentially equipped with a locking seal, a perforated screen, a telescopic short connector, a drop-out plug, a completion packer, a double male short connector, and a tubing hanger.

[0007] A method for using a fully open-hole segmented completion string with natural production capacity involves running the segmented string to the designed depth, then displacing the heavy mud from the original wellbore section using a screen. The required quantities and densities of various fluids are precisely calculated based on the wellbore dimensions to ensure that organic brine, white oil, or clean water can displace the mud above the suspended integrated completion packer. Simultaneously, the method ensures that the total well equivalent density after fluid displacement is not lower than before displacement. After fluid displacement, the suspended integrated completion packer is independently set and sealed. The delivery tool is retrieved, and the reinsertion string is run in. The reinsertion string is locked and sealed with the return sleeve. The wellhead is replaced, and a production tree is installed. Completion annulus protection fluid is used to displace the kill fluid in the well using a small-volume flow through a perforated screen. After fluid displacement, a dart is thrown onto the drop-out plug, and the well is pressure-sealed and sealed. The well packer is sealed, and then the annulus is pressurized to verify the sealing of the completion packer. After the verification is qualified, the dart is retrieved. A ball is dropped into the switchable sleeve, and the sleeve test hole is opened under pressure. The well is opened to produce fluid, and the fluid flows into the wellbore through the switchable sleeve test hole. The natural production capacity of the entire open hole is measured. The coiled tubing is run in under pressure to retrieve the ball seat and ball in the switchable sleeve and retrieve them out of the wellbore. Then, a special closing tool is run in to close the switchable sleeve. A ball is dropped into the self-sealing ball seat, and all open hole packers in the segmented tubing string are set under pressure. Positive pressure is continued to open the differential pressure sleeve. Then, the ball is dropped in sequence to open the ball-dropping sleeve, and the corresponding reservoir sections between the open hole packers are modified respectively. The opening tool is run in the coiled tubing to open the switchable sleeve and modify the upper reservoir section. After all reservoir sections have been fully modified, the well is opened to drain fluid and produce fluid.

[0008] Preferably, the throwing slide sleeve forms a sealed space inside the oil pipe by inserting a soluble ball of matching size, and the throwing slide sleeve is opened by pressurizing the oil pipe and cutting the shear pin at the throwing slide sleeve.

[0009] Preferably, the suspended well completion packer has independent setting capability, and can be set separately after the fluid replacement of the segmented tubing section is completed, thus achieving separate setting with the open hole packer.

[0010] Preferably, the locking seal is adapted to the return sleeve.

[0011] Preferably, the well completion packer is formed by combining a drop-and-retrieve plug with a spear to form a seal, and the wellhead is pressurized to complete the setting. After setting, the spear is retrieved by wireline operation or coiled tubing.

[0012] Preferably, the screen tube is a fluid displacement channel between the segmented tubing and the annulus.

[0013] Preferably, the differential pressure sleeve pressurizes the tubing through the sealed space formed by the sealing ball and the self-sealing ball seat, creating a pressure difference between the tubing and the casing annulus at the differential pressure sleeve. Under the action of the pressure difference, the differential pressure sleeve opens, forming a flow channel between the first reservoir section and the wellbore.

[0014] Preferably, the switchable sleeve includes a cylindrical body, a ball seat, a switchable mechanism, and a sealing structure. The ball seat achieves the initial opening of the switchable sleeve by receiving the sealing ball and pressing against the shear pin. At the same time, the ball seat is retrievalable, and the sealing ball and ball seat can be retrieved by a special retrieval tool lowered into the oil pipe. The switchable mechanism achieves repeated opening or closing of the switchable sleeve by forming a mechanism movement with a special opening or closing tool lowered into the oil pipe.

[0015] Preferably, the perforated screen tube is a fluid displacement channel between the oil pipe of the reinsertion tubing and the annulus.

[0016] Compared with existing technologies, this invention has the following beneficial effects: This invention discloses an open-hole segmented completion string and its usage method with full open-hole natural production capacity, belonging to the field of oil and gas field downhole tools and processes. By replacing heavy mud in the original wellbore of the segmented completion string section with a screen pipe, during the fluid replacement process, it ensures that organic brine, white oil, or clean water can be replaced above the suspended integrated completion packer, and that the equivalent density of the entire well after fluid replacement is not lower than before fluid replacement, thereby ensuring that the fluid in the wellbore has sufficient density to balance the formation pressure. By independently setting the suspended integrated completion packer and opening the switchable sliding sleeve, a safety barrier is constructed for fluid replacement in the back-inserted string section and for natural blowout in the full open-hole section. After the natural blowout test of the full open-hole section, by setting the open-hole packer and closing the switchable sliding sleeve, precise control and management of each reservoir section are achieved. By using ball dropping or special opening tools (for switchable sliding sleeves) to open the fracturing sliding sleeves step by step, the individual modification of each reservoir section is achieved, thereby improving the effect of reservoir modification. During operation, the use of switchable sliding sleeves, three back pressure valves, and self-sealing ball seats reduces the risks and improves the safety of the operation.

[0017] Furthermore, the ball-dropping sleeve can create a sealed space inside the tubing by inserting a soluble ball of a matching size. By pressurizing the tubing, the shear pin at the ball-dropping sleeve is cut to open the sleeve. This structural design allows for convenient separate modification of the reservoir section, improving the flexibility and effectiveness of construction.

[0018] Furthermore, the suspended completion packer has independent setting capability, allowing for separate setting from the open-hole packer. This design enables the suspended completion packer to be set independently after fluid replacement, simplifying the construction process and improving operational efficiency.

[0019] Furthermore, the locking seal is compatible with the reconnecting sleeve, which ensures the sealing performance between the reconnecting tubing and the wellbore, prevents liquid leakage, and guarantees the safety and reliability of the operation.

[0020] Furthermore, the completion packer forms a seal through a combination of a drop-and-retrieve plug and a spear, and setting is completed by wellhead pressure testing. This design allows for convenient setting and unsealing of the completion packer, simplifying the construction process and improving operational efficiency.

[0021] Furthermore, the switchable sleeve includes a cylinder, a ball seat, a switchable mechanism, and a sealing structure, enabling the initial opening and repeated opening or closing of the switchable sleeve. This design facilitates the modification and management of specific reservoir sections.

[0022] Furthermore, the perforated screen serves as a fluid displacement channel between the tubing and the annulus of the reinsertion tubing, enabling the removal of kill fluid from the well and improving the operational efficiency of the completion string. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the segmented tubular column structure of the present invention; Figure 2 This is a schematic diagram of the completion string structure of the back-insertion tubing string and the segmented tubing string combination of the present invention; In the diagram, 1-casing, 2-open hole, 3-guide shoe, 4-screen pipe, 5-three-backpressure valve, 6-self-sealing ball seat, 7-tubing, 8-differential pressure sleeve, 9-first open hole packer, 10-ball-dropping sleeve, 11-switchable sleeve, 12-suspended completion packer, 13-return sleeve, 14-feeding tool, 15-locking seal, 16-perforated screen pipe, 17-telescopic short joint, 18-drop-and-retrieve plug, 19-completion packer, 20-double male short joint, 21-tubing hanger, 22-second open hole packer. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] like Figure 1 and Figure 2 As shown, the present invention provides a fully open-hole segmented completion string with natural production capacity, including an insertion string and a return string; The insertion string includes an open hole 2 and a casing 1 connected to each other. An oil pipe 7 is installed inside the open hole 2 and the casing 1. The oil pipe 7 is provided with the following components in sequence from the open hole 2 to the casing 1: a guide shoe 3, a screen pipe 4, a three-backpressure valve 5, a self-sealing ball seat 6, a differential pressure sliding sleeve 8, a first open hole packer 9, a ball-throwing sliding sleeve 10, a second open hole packer 22, a switchable sliding sleeve 11, a suspended completion integrated packer 12, a return sleeve 13, and an insertion tool 14. The insertion string is sequentially equipped with a locking seal 15, a perforated screen pipe 16, a telescopic short joint 17, a drop-out plug 18, a completion packer 19, a double male short joint 20, and a tubing hanger 21. The tools are connected by tubing or variable thread connections.

[0029] The guide shoe 3, screen pipe 4, three-backpressure valve 5, and self-sealing ball seat 6 are matched with a threaded connection and can be directly connected; the differential pressure sleeve 8, ball-throwing sleeve 10, open hole packer, switchable sleeve 10, and suspended completion integrated packer 12 are connected by tubing 7 or variable thread. In addition, the upper part of the tubing string also includes a return sleeve 13 and a delivery tool 14.

[0030] The aforementioned downhole tools, including the guide shoe 3, screen pipe 4, three-stage backpressure valve 5, and self-sealing ball seat 6, are commonly used tools. The guide shoe 3 reduces end friction during tubing string insertion, enhancing its accessibility; the screen pipe 4 serves as a fluid displacement channel between the tubing and annulus in the segmented tubing string; the three-stage backpressure valve 5, composed of three single-flow valves, ensures blowout prevention safety within the tubing string; and the self-sealing ball seat 6 receives the sealing ball, acting as a pressure-blocking mechanism to assist in setting the open-hole packer. The differential pressure sliding sleeve 8 pressurizes the tubing string through the sealed space formed by the sealing ball and the self-sealing ball seat 6, creating a pressure difference between the tubing and the casing annulus at the sliding sleeve. Under the action of the pressure difference, the sliding sleeve opens, forming a flow channel between the first reservoir section and the wellbore. The aforementioned open-hole packer completes the setting action by receiving the sealing ball with the lower self-sealing ball seat 6, thereby achieving effective segmentation of different reservoir sections and creating conditions for implementing segmented stimulation. The ball-throwing slide 10 forms a sealed space in the oil pipe 7 by inserting a soluble ball of matching size. By pressurizing the oil pipe, the shear pin at the slide is cut to open the ball-throwing slide 10. The switchable sleeve 11 consists of a cylindrical body, a ball seat, an openable / closeable mechanism, and a sealing structure (including a seal). The ball seat receives the sealing ball and presses against the shear pin, enabling the initial opening of the switchable sleeve 11. Simultaneously, the ball seat is retrievalable; a dedicated retrieval tool can be lowered into the coiled tubing to retrieve the sealing ball and ball seat, increasing the tubing diameter. The openable / closeable mechanism, through its interaction with a dedicated opening or closing tool lowered into the coiled tubing, enables repeated opening and closing of the switchable sleeve 11. The suspended completion packer 12 has independent setting capability. After fluid replacement of the segmented tubing section, the suspended completion packer 12 is set independently, achieving separate setting with the open hole packer. The suspended completion packer forms a well barrier, ensuring both annular well control safety and unobstructed flow throughout the open hole section. The locking seal 15 is matched with the return sleeve 13 to achieve effective connection and sealing between the re-insertion tubing and the segmented tubing; The perforated screen 16 is a fluid replacement channel between the tubing and the annulus in the reinsertion string. The advantage of setting the perforated screen 16 here is that it can realize fluid replacement after wellhead replacement, ensuring construction safety. The telescopic shorting 17 is mainly used to compensate for the displacement of the mandrel during well completion packer setting. Whether the telescopic shorting 17 is configured depends on whether the mandrel is displaced during well completion packer setting. The aforementioned drop-type plug 18 is a spear receiving device, serving as an auxiliary tool for setting the well completion packer; The well completion packer 19 forms a seal by combining a drop-and-retrieve plugger with a spear. The wellhead is pressurized to complete the setting. After setting, the spear is retrieved by wireline operation or coiled tubing to keep the wellbore unobstructed. The double male short connector 20 is a connection tool for connecting oil pipes to oil pipe hangers; The aforementioned tubing hanger 21 is a tubing suspension tool that simultaneously separates and seals the tubing from the annulus.

[0031] This invention also provides a method for using a segmented open-hole completion string with full open-hole natural production capacity. The drill pipe is used to send the segmented tubing string to the predetermined position. A circulation system, formed by the screen pipe 4 at the bottom of the tubing string, displaces the kill fluid from the tubing 7 and annulus. The integrated completion packer 12 is set using the insertion tool, and the drill pipe is retrieved. The tubing string is then lowered to the return sleeve 13 to complete the anchoring and sealing action. After the wellhead is fitted with a production tree, a circulation system, formed by the perforated screen pipe of the return tubing string, displaces the kill fluid from the return tubing string and annulus. A matching dart is dropped into the drop-and-retrieve plug to form a seal, and pressure testing completes the setting of the completion packer. A ball is dropped to open the switchable sliding sleeve 11 to test the natural production capacity of the entire open hole section. After the test, a continuous working tubing string with a closing tool is lowered to close the switchable sliding sleeve 11, and the dropped ball and its seat are retrieved. The ball is dropped into the self-sealing ball seat 6 to set the open hole packer, achieving the segmented purpose. The sliding sleeves are opened stage by stage, and reservoir stimulation operations are performed on each segment separately. After completion, a unified blowout test is conducted to assess production capacity.

[0032] The detailed steps are as follows: After the segmented tubing is lowered to the designed depth, the heavy mud in the original wellbore of the segmented tubing section is displaced through screen pipe 4. The required quantity and density of various liquids are precisely calculated based on the wellbore dimensions to ensure that organic brine, white oil, or clean water can displace the mud above the suspended completion packer 12, while ensuring that the total well equivalent density after fluid displacement is not lower than before. After fluid displacement, the suspended completion packer 12 is independently set and sealed. The delivery tool 14 is retrieved, and the reinsertion tubing is lowered. The reinsertion tubing locking seal 15 is connected and sealed with the return sleeve 13. The wellhead is replaced, and the production tree is installed. The completion annulus protection fluid is used to displace the well control fluid in the well through perforated screen pipe 16 at a small rate. After fluid displacement, a dart is thrown onto the drop-out plug 18, and the completion packer 19 is set under pressure. Then, the annulus is pressurized to seal the completion packer. Packer 19 is sealed and, if the seal is deemed acceptable, the dart is retrieved. A ball is dropped into the switchable sleeve 11, and pressure is applied to open the sleeve's test hole. The well is then opened to produce fluid. The fluid flows through the test hole of the switchable sleeve 11 into the wellbore, and the natural production capacity of the entire open hole is measured. A coiled tubing retrieval tool is run under pressure, and the ball seat and ball in the switchable sleeve 11 are retrieved from the wellbore. Then, a special closing tool is run to close the switchable sleeve 11. A ball is dropped into the self-sealing ball seat 6, and pressure is applied to set all open hole packers 9 in the segmented tubing string. Positive pressure is continued, and the differential pressure sleeve 8 is opened. Then, a ball is dropped to open the ball-dropping sleeve 10 in sequence, modifying the corresponding reservoir sections between the open hole packers 9. A coiled tubing opening tool is run into the switchable sleeve 11 to modify the upper reservoir section. After all reservoir sections have been fully modified, the well is opened to drain fluid and produce fluid.

[0033] The aforementioned downhole tools, including the guide shoe 3, screen pipe 4, three-stage backpressure valve 5, and self-sealing ball seat 6, are commonly used tools. The guide shoe 3 reduces end friction during tubing string insertion, enhancing its accessibility; the screen pipe 4 serves as a fluid displacement channel between the tubing and annulus in the segmented tubing string; the three-stage backpressure valve 5, composed of three single-flow valves, ensures blowout prevention safety within the tubing string; and the self-sealing ball seat 6 receives the sealing ball, acting as a pressure-blocking mechanism to assist in setting the open-hole packer. The differential pressure sliding sleeve 8 pressurizes the tubing string through the sealed space formed by the sealing ball and the self-sealing ball seat 6, creating a pressure difference between the tubing and the casing annulus at the sliding sleeve. Under the action of the pressure difference, the sliding sleeve opens, forming a flow channel between the first reservoir section and the wellbore. The aforementioned open-hole packer completes the setting action by receiving the sealing ball with the lower self-sealing ball seat 6, thereby achieving effective segmentation of different reservoir sections and creating conditions for implementing segmented stimulation. The ball-throwing slide 10 forms a sealed space in the oil pipe 7 by inserting a soluble ball of matching size. By pressurizing the oil pipe, the shear pin at the slide is cut to open the ball-throwing slide 10. The switchable sleeve 11 consists of a cylindrical body, a ball seat, an openable / closeable mechanism, and a sealing structure (including a seal). The ball seat receives the sealing ball and presses against the shear pin, enabling the initial opening of the switchable sleeve 11. Simultaneously, the ball seat is retrievalable; a dedicated retrieval tool can be lowered into the coiled tubing to retrieve the sealing ball and ball seat, increasing the tubing diameter. The openable / closeable mechanism, through its interaction with a dedicated opening or closing tool lowered into the coiled tubing, enables repeated opening and closing of the switchable sleeve 11. The suspended completion packer 12 has independent setting capability. After fluid replacement of the segmented tubing section, the suspended completion packer 12 is set independently, achieving separate setting with the open hole packer. The suspended completion packer forms a well barrier, ensuring both annular well control safety and unobstructed flow throughout the open hole section. The locking seal 15 is matched with the return sleeve 13 to achieve effective connection and sealing between the re-insertion tubing and the segmented tubing; The perforated screen 16 is a fluid replacement channel between the tubing and the annulus in the reinsertion string. The advantage of setting the perforated screen 16 here is that it can realize fluid replacement after wellhead replacement, ensuring construction safety. The telescopic shorting 17 is mainly used to compensate for the displacement of the mandrel during well completion packer setting. Whether the telescopic shorting 17 is configured depends on whether the mandrel is displaced during well completion packer setting. The aforementioned drop-type plug 18 is a spear receiving device, serving as an auxiliary tool for setting the well completion packer; The well completion packer 19 forms a seal by combining a drop-and-retrieve plugger with a spear. The wellhead is pressurized to complete the setting. After setting, the spear is retrieved by wireline operation or coiled tubing to keep the wellbore unobstructed. The double male short connector 20 is a connection tool for connecting oil pipes to oil pipe hangers; The aforementioned tubing hanger 21 is a tubing suspension tool that simultaneously separates and seals the tubing from the annulus.

[0034] By configuring a retrieval and switchable sliding sleeve 11, an open-hole packer, and a separate setting of the integrated open-hole completion packer 12, along with corresponding process optimization measures, an innovative open-hole segmented modification string and usage method is proposed that can test the natural production capacity of the entire open-hole section in one trip. This makes up for the defects of the current open-hole segmented modification process, while also taking into account clean completion and reservoir protection, and achieving the same geological objectives in terms of operating cost and cycle.

[0035] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by the specification, can make many other modifications without departing from the scope of the claims of the present invention, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A fully open-hole segmented completion string with natural production capacity, characterized in that, This includes the insertion and re-insertion of the tubing; The feed string includes an open hole (2) and a casing (1) connected to each other. An oil pipe (7) is installed in the open hole (2) and the casing (1). The oil pipe (7) is provided with a guide shoe (3), a screen pipe (4), a three-back pressure valve (5), a self-sealing ball seat (6), a differential pressure sleeve (8), a first open hole packer (9), a ball-throwing sleeve (10), a second open hole packer (22), a switchable sleeve (11), a suspended completion integrated packer (12), a return sleeve (13), and a feed tool (14) in sequence from the open hole (2) to the casing (1). The insertion string is sequentially equipped with a locking seal (15), a perforated screen (16), a telescopic short joint (17), a drop-out plug (18), a completion packer (19), a double male short joint (20), and a tubing hanger (21).

2. A method for using a fully open-hole segmented completion string with natural production capacity, characterized in that, Based on the open-hole segmented completion string with full open-hole natural production capacity as described in claim 1, after the segmented string is lowered to the designed depth, the heavy mud in the original wellbore of the segmented string section is replaced by the screen pipe (4). The required amount and density of various liquids are accurately calculated according to the wellbore size to ensure that organic brine or white oil or clean water can replace the suspended integrated completion packer (12) and ensure that the equivalent density of the whole well after the replacement is not lower than that before the replacement. After the replacement is completed, the suspended integrated completion packer (12) is independently set and sealed. The delivery tool (14) is taken out and the reinsertion string is lowered. The reinsertion string lock seal (15) is connected and sealed with the reinsertion sleeve (13). The wellhead is replaced and the gas production tree is installed. The completion annulus protection fluid is used to replace the well control fluid in the well through the perforated screen pipe (16) at a small rate. After the replacement is completed, the dart is thrown to the retrieval plug (18) and the completion packer is set under pressure. 19), then pressurize the annulus to test the sealing of the well completion packer (19). After the sealing is qualified, take out the spear; throw the ball to the switchable sleeve (11), pressurize to open the sleeve test hole, open the well to produce, and flow through the test hole of the switchable sleeve (11) to the wellbore. Measure the natural production capacity of the open hole. Run the coiled tubing to retrieve the tool under pressure. Retrieve the ball seat and ball in the switchable sleeve (11) from the wellbore. Then run the special closing tool to close the switchable sleeve (11). Throw the ball to the self-sealing ball seat (6). Pressurize to set all the open hole packers (9) in the segmented tubing string. Continue to pressurize and open the differential pressure sleeve (8). Then throw the ball to open the ball throwing sleeve (10) in sequence. Modify the corresponding reservoir sections between the open hole packers (9) respectively. Run the coiled tubing to open the switchable sleeve (11) and modify the upper reservoir section. After the full modification of all reservoir sections is completed, open the well to drain the fluid and produce.

3. The method for using a fully open-hole segmented completion string with natural production capacity according to claim 2, characterized in that, The ball-throwing sleeve (10) forms a sealed space in the oil pipe by inserting a soluble ball of matching size. By pressurizing the oil pipe, the shear pin at the ball-throwing sleeve (10) is cut to open the ball-throwing sleeve (10).

4. According to claim 2, the method of using a full open-hole segmented completion string with natural production capacity, the suspended completion integrated packer (12) has independent setting capability, and after the well section of the segmented string is replaced, the suspended completion integrated packer (12) is set separately, realizing separate setting with the open-hole packer.

5. The method of using a full open-hole segment completion string with natural production capacity according to claim 2, wherein the locking seal (15) is adapted to the return sleeve (13).

6. The method of using a full open-hole segmented completion string with natural production capacity according to claim 2, wherein the completion packer (19) is formed by combining a drop-and-retrieve plugger with a spear to form a seal, the wellhead is pressurized to complete the setting, and after setting, the spear is retrieved by wireline operation or coiled tubing.

7. The method of using a full open-hole segmented completion string with natural production capacity according to claim 2, wherein the screen pipe (4) is a fluid displacement channel between the tubing (7) of the segmented string and the annulus.

8. The method of using a full open-hole segmented completion string with natural production capacity according to claim 2, wherein the differential pressure sleeve (8) pressurizes the string through the sealed space formed by the sealing ball and the self-sealing ball seat (6), and a pressure difference is formed between the tubing and the casing annulus at the differential pressure sleeve (8). Under the action of the pressure difference, the differential pressure sleeve (8) opens to form a flow channel between the first reservoir section and the wellbore.

9. The method of using a fully open-hole segmented completion string with natural production capacity according to claim 2, wherein the switchable sliding sleeve (11) includes a cylinder, a ball seat, a switchable mechanism, and a sealing structure, wherein, The ball seat achieves the initial opening of the switchable sleeve (11) by receiving the sealing ball and pressing the shear pin. At the same time, the ball seat is retrievalable. The sealing ball and ball seat are retrieved by a special retrieval tool lowered through the oil pipe (7). The switchable mechanism achieves repeated opening or closing of the switchable sleeve (11) by forming a mechanism movement with the special opening or closing tool lowered through the oil pipe (7).

10. The method of using a full open-hole segmented completion string with natural production capacity according to claim 2, wherein the perforated screen (16) is a fluid displacement channel between the tubing (7) of the back-insertion string and the annulus.

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