A two-stage float collar completion string and method of use thereof

Abstract

The present application relates to the technical fields of oil and gas well completion, and particularly relates to a two-stage floating collar well completion pipe string and a use method thereof, which aims to solve the problem of early opening of the floating collar. The two-stage floating collar well completion pipe string comprises a first blind plate type floating collar and a second blind plate type floating collar, and the first blind plate type floating collar and the second blind plate type floating collar are of the same structure. The upper end of the first blind plate type floating collar is connected with a first drilling fluid filling casing pipe, and the lower end of the first blind plate type floating collar is connected with an isolation section casing pipe which is a closed air section casing pipe. The upper end of the second blind plate type floating collar is connected with a second drilling fluid filling casing pipe, and the lower end of the second blind plate type floating collar is connected with a floating section casing pipe which is a closed air section casing pipe. The drilling fluid column in the pipe string is divided into two sections, so that the liquid column pressure borne by a single floating collar is reduced, and the impact of liquid column agitation on the floating collar caused by too fast pipe string lowering speed is reduced.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well completion technology, and in particular to a two-stage floating coupling well completion string and its application method. Background Technology

[0002] Currently, the development of unconventional oil and gas resources such as shale gas, shale oil, tight oil, and tight gas in China generally adopts the horizontal well completion method with Φ139.7mm casing. Subsequent reservoir stimulation is achieved through high-volume fracturing using bridge plug perforation and casing injection. Horizontal wells commonly face the challenge of running casing. During normal running, drilling fluid is injected into the casing, and the weight of the tubing string entering the horizontal section is entirely converted into frictional resistance. The longer the horizontal section, the more difficult it is to run the casing. The floating casing technology involves installing a temporary sealing device, called a floating coupling, on the casing completion string. Below the floating coupling, no drilling fluid is injected into the casing; the casing is sealed with air to reduce the normal pressure of the tubing string on the wellbore, effectively reducing the frictional resistance as the tubing string descends in the horizontal section. Above the floating coupling, drilling fluid is injected into the casing to increase the weight of the upper tubing string. The weight of the upper tubing string propels the tubing string downwards, thus achieving safe and smooth running of the entire tubing string.

[0003] There are two main types of floating couplings: sliding sleeve type and blind plate type. The blind plate in a blind plate type floating coupling is typically made of stress-breaking material. After pressurization at the wellhead, the blind plate will directly break into small particles under the breaking pressure, which can circulate out of the wellbore through the annulus between the casing and the wellbore. Furthermore, the blind plate type floating coupling does not form a narrowing effect internally after opening. However, the manufacturing process of the blind plate is relatively complex, and the opening pressure is difficult to control precisely. Additionally, excessively rapid descent during tubing string insertion can cause drilling fluid column excitation, leading to premature blind plate opening and potentially triggering complex downhole accidents. Summary of the Invention

[0004] The purpose of this invention is to provide a two-stage floating coupling well completion string and its usage method to solve the problem of premature opening of the floating coupling.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A two-stage floating coupling completion string includes a first blind-plate type floating coupling and a second blind-plate type floating coupling, both having identical structures. The upper end of the first blind-plate type floating coupling is connected to a first drilling fluid filling casing, and the lower end is connected to an isolation section casing, which is a closed air section casing. The upper end of the second blind-plate type floating coupling is connected to a second drilling fluid filling casing, and the lower end is connected to a floating section casing, which is also a closed air section casing. The end of the isolation section casing facing away from the first blind-plate type floating coupling is connected to the upper end of the second drilling fluid filling casing. The first and second blind-plate type floating couplings are configured to open sequentially after wellhead pressurization.

[0007] Furthermore, the first blind plate type floating coupling includes a blind plate and a sliding sleeve disposed below the blind plate, with a striker disposed at one end of the sliding sleeve near the blind plate; the first blind plate type floating coupling is configured such that when the blind plate moves down and strikes the striker during startup, the blind plate generates a stress breakage point.

[0008] Furthermore, the first blind plate floating coupling also includes a shear ring, the shearing pressure of which is lower than the breaking stress of the blind plate; the first blind plate floating coupling is configured to shear the shear ring first during startup, and then push the blind plate down.

[0009] Furthermore, the first blind plate type floating coupling also includes a pressure-bearing sliding sleeve, which is fitted onto the lower sliding sleeve, with the lower end of the pressure-bearing sliding sleeve abutting against the upper side of the shear ring; the inner wall of the pressure-bearing sliding sleeve is provided with a pressure-bearing boss, and the blind plate is inserted into the pressure-bearing sliding sleeve and abuts against the upper end face of the pressure-bearing boss.

[0010] Furthermore, the first blind plate floating coupling also includes an isolation sleeve, which is inserted into the upper side of the pressure-bearing sliding sleeve; the lower end of the isolation sleeve abuts against the upper end of the blind plate and cooperates with the pressure-bearing boss to limit the blind plate.

[0011] Furthermore, the first blind plate type floating coupling also includes a lower connector, the upper end of which abuts against the lower side of the shear ring; the upper side of the lower connector is fitted onto the lower side of the sliding sleeve.

[0012] Furthermore, the first blind plate type floating coupling also includes an upper connector, the lower side of which is fitted onto the lower connector, and a first step is provided on the outer side of the lower connector, with the lower end of the upper connector abutting against the first step; the blind plate, the sliding sleeve, the shear ring, the pressure-bearing sliding sleeve, and the isolation sleeve are all inserted into the upper connector.

[0013] Furthermore, a first annular space is formed between the lower sliding sleeve and the pressure-bearing sliding sleeve, and a second annular space is formed between the lower connector and the upper connector; the first annular space and the second annular space are used to ensure the downward movement distance of the pressure-bearing sliding sleeve; a first through hole is opened on the side wall of the sliding sleeve, and the first through hole communicates with the first annular space; a second through hole is opened on the side wall of the lower connector, and the second through hole communicates with the second annular space.

[0014] Furthermore, after the first and second blind plate floating couplings are opened, their inner diameters are consistent with the inner diameter of the casing.

[0015] In another aspect of the present invention, a method of using the dual-stage floating coupling completion string as described above includes the following steps:

[0016] Collect basic data on the drilling well, including actual drilling inclination data, drilling fluid density, casing wall thickness, casing steel grade, and section weight.

[0017] Calculate the liquid column pressure and check the casing's resistance to external extrusion;

[0018] Determine the location of the floating coupling: Calculate the length of the floating section sleeve based on software simulation analysis to determine the installation location of the second blind plate floating coupling. Determine the location of the first blind plate floating coupling based on the pressure setting principle, so that the first and second blind plate floating couplings can withstand appropriate liquid column pressure.

[0019] Run the double-stage floating coupling completion string: Install the completion string structure and run each component in sequence. The floating section casing and the isolation section casing are not filled with drilling fluid, while the first and second drilling fluid filling casings are filled with drilling fluid.

[0020] Open the floating coupling: After the completion string is lowered to the designed well depth, pressurize the wellhead and open the first blind plate floating coupling and the second blind plate floating coupling in sequence;

[0021] Air removal from the casing: Inject drilling fluid and perform static displacement to displace the air in the floating section of the casing from the wellhead, preventing air from being squeezed into the annulus of the casing and well wall;

[0022] Start the drilling mud pump and enter the cementing preparation stage.

[0023] In summary, the technical effects achieved by this invention are as follows:

[0024] This invention provides a two-stage floating coupling completion string, comprising a first blind-plate type floating coupling and a second blind-plate type floating coupling, both having identical structures. The upper end of the first blind-plate type floating coupling is connected to a first drilling fluid filling casing, and the lower end is connected to an isolation section casing, which is a closed air section casing. The upper end of the second blind-plate type floating coupling is connected to a second drilling fluid filling casing, and the lower end is connected to a floating section casing, which is also a closed air section casing. The end of the isolation section casing facing away from the first blind-plate type floating coupling is connected to the upper end of the second drilling fluid filling casing. The first and second blind-plate type floating couplings are configured to open sequentially after wellhead pressurization.

[0025] Because this invention uses two floating couplings in the dual-stage floating coupling completion string, the fluid column of the injection fluid inside the string is divided into two segments, reducing the fluid column pressure on a single floating coupling. This effectively reduces the impact force on the floating coupling caused by the rapid lowering speed of the string due to the drilling fluid column, preventing premature opening of the floating coupling. Simultaneously, the isolation casing prevents the pressure from rising due to formation temperature inside the floating casing. This pressure increase would then be transmitted to the first blind plate floating coupling via the fluid column in the second blind plate floating coupling and the second injection fluid casing, thus preventing an increase in the opening pressure of the first blind plate floating coupling and avoiding increased difficulty in opening the first blind plate floating coupling due to the use of two floating couplings. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of the two-stage floating coupling completion string provided in an embodiment of the present invention;

[0028] Figure 2 for Figure 1 Schematic diagram of the first blind plate type floating coupling in China;

[0029] Figure 3 This is a schematic diagram of the shear ring structure;

[0030] Figure 4 This is a schematic diagram of the structure of a pressure-bearing sliding sleeve;

[0031] Figure 5 This is a schematic diagram of the lower connector.

[0032] Figure 6 A flowchart illustrating the usage method of the two-stage floating coupling completion string provided in this embodiment of the invention.

[0033] Icons: 100-First blind plate floating coupling; 200-Second blind plate floating coupling; 300-First drilling fluid filling casing; 400-Isolation section casing; 500-Second drilling fluid filling casing; 600-Floating section casing; 700-Blind plug sub; 800-Floating collar; 900-Floating shoe; 110-Blind plate; 120-Sliding sleeve; 130-Shear ring; 140-Pressure-bearing sliding sleeve; 150-Isolation sleeve; 160-Lower connector; 170-Upper connector; 180-L-shaped sealing ring; 141-Pressure-bearing boss; 161-First step; 162-Second step; 163-Third step; a-First annular space; b-Second annular space. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] Example 1:

[0038] Blind flange floating couplings typically use stress-breaking materials for the blind flanges. When pressurized at the wellhead, the blind flange will directly break into small particles under the breaking pressure, which can circulate out of the wellbore through the annulus between the casing and the wellbore. Furthermore, the internal diameter of the blind flange floating coupling does not narrow after opening. However, the manufacturing process of blind flanges is relatively complex, and the opening pressure is difficult to control precisely. Additionally, excessively rapid descent during tubing string insertion can cause drilling fluid column excitation, leading to premature blind flange opening and potentially triggering complex downhole accidents.

[0039] In view of this, the present invention provides a two-stage floating coupling completion string, including a first blind plate floating coupling 100 and a second blind plate floating coupling 200, the first blind plate floating coupling 100 and the second blind plate floating coupling 200 having the same structure; the upper end of the first blind plate floating coupling 100 is connected to a first drilling fluid injection casing 300, and the lower end of the first blind plate floating coupling 100 is connected to an isolation section casing 400, the isolation section casing 400 being a closed air section. The casing; the upper end of the second blind-plate floating coupling 200 is connected to the second drilling fluid filling casing 500, and the lower end of the second blind-plate floating coupling 200 is connected to the floating section casing 600, which is a closed air section casing; the end of the isolation section casing 400 facing away from the first blind-plate floating coupling 100 is connected to the upper end of the second drilling fluid filling casing 500; the first blind-plate floating coupling 100 and the second blind-plate floating coupling 200 are configured to open sequentially after the wellhead is pressurized.

[0040] Because the present invention uses two floating couplings in the dual-stage floating coupling completion string, the fluid column of the injection fluid inside the string is divided into two segments, reducing the fluid column pressure on a single floating coupling. This effectively reduces the impact force on the floating coupling caused by the rapid lowering speed of the string due to the drilling fluid column, preventing the floating coupling from opening prematurely. Simultaneously, the isolation section casing 400 prevents the pressure increase of the air inside the floating section casing 600 due to formation temperature from being transmitted to the first blind plate floating coupling 100 through the fluid column in the second blind plate floating coupling 200 and the second injection drilling fluid casing 500, thus preventing an increase in the opening pressure of the first blind plate floating coupling 100 and avoiding increased difficulty in opening the first blind plate floating coupling 100 due to the use of two floating couplings.

[0041] The following combination Figures 1-6 The structure and shape of the two-stage floating coupling completion string provided in this embodiment are described in detail:

[0042] In an optional embodiment, the first floating coupling includes an upper connector 170 and a lower connector 160, such as... Figure 2 , Figure 5 As shown, the lower side of the upper connector 170 is fitted onto the lower connector 160. A first step 161 is provided on the outer side of the lower connector 160, and the lower end of the upper connector 170 abuts against the first step 161. Specifically, the lower connector 160 has an external thread on its outer side, and the upper connector 170 has an internal thread on its lower side. The upper connector 170 and the lower connector 160 are threaded together, and the first step 161 limits the thread engagement length. When rotating the lower sleeve, the rotation direction is consistent with the thread engagement direction, thereby preventing further thread engagement and damage. Furthermore, the upper connector 170 has an internal thread on its upper side for connection with the sleeve; the lower connector 160 has an external thread on its lower side for connection with the sleeve.

[0043] In this embodiment, the first blind-plate type floating coupling 100 includes a blind plate 110 and a sliding sleeve 120 disposed below the blind plate 110. A striking pin is disposed at one end of the sliding sleeve 120 near the blind plate 110. The first blind-plate type floating coupling 100 is configured such that, upon startup, the blind plate 110 moves downward and strikes the striking pin, causing a stress breakage point in the blind plate 110. Both the blind plate 110 and the sliding sleeve 120 are inserted into the upper connector 170, with the blind plate 110 dividing the inner cavity of the upper connector 170. The lower side of the sliding sleeve 120 is inserted into the upper side of the lower connector 160, and a second step 162 is disposed on the inner side of the lower connector 160. The lower end of the sliding sleeve 120 abuts against the second step 162. Specifically, the sliding sleeve 120 is provided with four evenly distributed protruding striking pins. By cooperating with the blind flange 110 and the firing pin, the crushing pressure of the blind flange 110 can be increased during its manufacturing process to prevent it from breaking. When the first floating coupling needs to be opened, the blind flange 110 impacts the firing pin, thereby generating a stress fracture point. Only a small amount of pressure is needed to open the blind flange 110, reducing the manufacturing process requirements for the blind flange 110. Precise control of the crushing pressure of the blind flange 110 is not required, thus reducing the manufacturing cost of the blind flange 110.

[0044] Among them, the blind plate 110 is mainly composed of chemical components such as silicon dioxide and aluminum oxide. It is a stress-breaking material with alkali resistance, high temperature resistance and high pressure resistance. It has good crushing performance, uniform crushing and particle size ≤5mm. It can be recycled out of the wellbore and can effectively reduce the risk of cementing operations.

[0045] Meanwhile, the impact of the blind flange 110 with the firing pin creates a stress fracture point, allowing the blind flange 110 to open under relatively low pressure, effectively preventing situations where the blind flange 110 cannot be opened. In conventional structures without firing pins, the opening pressure of the blind flange is difficult to control precisely during manufacturing. When encountering a blind flange with excessively high opening pressure, it may be difficult to open, or even impossible to open by pressurizing at the wellhead. In extreme cases, the opening pressure of the blind flange may even exceed the rated internal pressure resistance of the casing. When the blind flange cannot be opened by pressurizing at the wellhead, a small drill string needs to be lowered to drill it out, which incurs additional costs and is complex. Furthermore, because the waiting time for lowering the small drill string and the construction time can take 3-4 days, the drilling fluid in the well is in a stagnant state. During this time, the drilling fluid is prone to water loss, which in severe cases can lead to failure to pass through the well and make cementing impossible.

[0046] In this embodiment, the first blind-plate type floating coupling 100 further includes a pressure-bearing sliding sleeve 140 and an isolation sleeve 150, both of which are inserted into the upper connector 170. Figure 2 , Figure 4As shown, a pressure-bearing sleeve 140 is fitted onto a lower sleeve 120. The inner wall of the pressure-bearing sleeve 140 is provided with a pressure-bearing boss 141. A blind flange 110 is inserted into the pressure-bearing sleeve 140 and abuts against the upper end face of the pressure-bearing boss 141. An isolation sleeve 150 is inserted into the upper side of the pressure-bearing sleeve 140. The lower end of the isolation sleeve 150 abuts against the upper end of the blind flange 110 and cooperates with the pressure-bearing boss 141 to limit the blind flange 110. The lower side of the isolation sleeve 150 is provided with an external thread, and the upper side of the pressure-bearing sleeve 140 is provided with an internal thread. The pressure-bearing sleeve 140 and the isolation sleeve 150 are connected by threads. When the blind flange 110 moves downward under the pressure of the drilling fluid, it causes the pressure-bearing sleeve 140 and the isolation sleeve 150 to move downward synchronously.

[0047] Specifically, the outer side of the sliding sleeve 120, the inner side of the pressure-bearing sliding sleeve 140, the upper end face of the lower connector 160, and the lower end face of the pressure-bearing boss 141 form a first annular space a to ensure the downward movement distance of the pressure-bearing boss 141. Furthermore, a first through hole is provided on the side wall of the sliding sleeve 120, communicating with the first annular space a. When the pressure-bearing sliding sleeve 140 moves downward, air in the first annular space a is discharged through the first through hole, preventing compressed air from affecting the downward movement of the pressure-bearing sliding sleeve 140. Specifically, four first through holes are evenly distributed around the circumference of the side wall of the sliding sleeve 120.

[0048] In an optional embodiment, an L-shaped sealing ring 180 is provided between the blind flange 110 and the pressure-bearing boss 141, and an L-shaped sealing ring 180 is provided between the blind flange 110 and the lower end face of the isolation sleeve 150. The L-shaped sealing ring 180 simultaneously improves the sealing and protects the blind flange 110, enhances the sealing of the blind flange 110 against the upper connector 170, and prevents the blind flange 110 from being damaged by impact during transportation and installation.

[0049] In this embodiment, the first blind-plate type floating coupling 100 further includes a shear ring 130, which is fitted onto the sliding sleeve 120 and inserted into the lower side of the pressure-bearing sliding sleeve 140. For example... Figure 2 , Figure 3As shown, the upper end face of the lower connector 160 abuts against the step inside the shear ring 130, and the lower end face of the pressure-bearing sleeve 140 abuts against the step outside the shear ring 130. The shearing pressure of the shear ring 130 is lower than the crushing stress of the blind plate 110. The first blind plate floating coupling 100 is configured to first shear the shear ring 130 during startup, and then push the blind plate 110 downward, causing the blind plate 110 to strike the striker and generate a stress breakage point. Optionally, the shear ring 130 is made of brass, which has good shearing performance and helps to stabilize the opening pressure of the first blind plate floating coupling 100. Specifically, the crushing pressure of the blind plate 110 should be 10 MPa higher than the shearing pressure of the shear ring 130, and the shearing pressure of the shear ring 130 should also be 10-15 MPa higher than the liquid column, to prevent the shear ring 130 from being sheared prematurely and the blind plate 110 from being crushed prematurely by the liquid column during the tubing insertion process.

[0050] Furthermore, a third step 163 is provided on the outer side of the lower connector 160. The outer side of the lower connector 160, the inner side of the upper connector 170, the inner side of the shear ring 130, and the third step 163 form a second annular space b; the first annular space a and the second annular space b are used to ensure the downward movement distance of the pressure-bearing sleeve 140. Similarly, a second through hole is provided on the side wall of the lower connector 160, which communicates with the second annular space b to prevent compressed air from affecting the downward movement of the pressure-bearing sleeve 140.

[0051] In this embodiment, after the first blind plate floating coupling 100 and the second blind plate floating coupling 200 are opened, their inner diameters are consistent with the inner diameter of the casing, realizing the full bore of the casing string, which facilitates the entry of subsequent working tools and reduces the risk of subsequent working tools being entered.

[0052] In this embodiment, as Figure 2 As shown, a step is provided on the outer side of the isolation sleeve 150. Stress concentration is easily generated at this step. Through holes are evenly distributed along the circumference of the side wall to improve stress distribution and prevent damage to the isolation sleeve 150.

[0053] In this embodiment, a sealing ring is provided between the pressure-bearing sliding sleeve 140 and the upper connector 170, and a sealing ring is provided between the upper connector 170 and the lower connector 160 to improve the sealing performance and ensure the sealing of the upper and lower sides of the blind plate 110.

[0054] In the optional embodiment, the two-stage floating coupling completion string also includes a blind plug 700, a floating collar 800, and a floating shoe 900. For example... Figure 1As shown, the blind plug 700 is connected to the end of the floating section casing 600, sealing off the floating section casing 600. One side of the blind plug 700 is the floating section casing 600, and the other side is the float collar 800. The pressure at which the blind plug 700 opens from one side of the floating section casing 600 is lower than the pressure at the other side, preventing drilling fluid from flowing back into the floating section casing 600 and causing floating failure if the float collar 800 or float shoe 900 is damaged by high fluid column pressure. Optionally, the blind plug 700 can adopt the structure of a first blind plate type floating collar 100. For reference, the pressure at which the blind plug 700 opens from one side of the floating section casing 600 is 6-7 MPa, and the pressure at the other side is 70 MPa.

[0055] In this embodiment, the opening pressure of the second blind-plate floating coupling 200 is higher than the liquid column pressure between the first blind-plate floating coupling 100 and the second blind-plate floating coupling 200. Specifically, the opening pressure of the second blind-plate floating coupling 200 is 8-10 MPa higher than the liquid column pressure between the first blind-plate floating coupling 100 and the second blind-plate floating coupling 200.

[0056] The opening process of the dual-stage floating coupling completion string provided in this embodiment is as follows:

[0057] Pressurization at the wellhead increases the pressure within the first drilling fluid-filled casing 300, shearing the shear ring 130 on the first blind plate floating coupling 100. This then pushes the blind plate 110 downwards to impact the striker, creating a stress fracture point and allowing it to break under relatively low pressure. The blind plate 110 subsequently breaks under drilling fluid pressure, opening the first blind plate floating coupling 100. This connects the first and second drilling fluid-filled casings 300 and 500, opening the second blind plate floating coupling 200 under drilling fluid pressure. Drilling fluid injection continues, and static displacement is performed to displace air from the floating section casing 600 from the wellhead, preventing air from being forced into the annulus and affecting wellbore stability. After the air is purged, the floating section of the casing is filled with drilling fluid, the drilling mud pump is started, the blind plug section 700 is opened, and after a small-volume jacking, the double-stage floating coupling completion string is opened.

[0058] In this embodiment, if there is no isolation section casing 400, under the influence of formation temperature, the air pressure inside the floating section casing 600 increases. This pressure acts on the blind plate 110 of the second blind plate floating coupling 200, and at the same time, it squeezes the L-shaped sealing ring 180 on the second blind plate floating coupling 200, causing the blind plate 110 to deform and shift, thereby squeezing the liquid inside the second drilling fluid filling casing 500, and increasing the liquid pressure inside the second drilling fluid filling casing 500. The liquid pressure inside the second drilling fluid filling casing 500 then acts on the blind plate 110 of the first blind plate floating coupling 100, affecting the downward movement of the blind plate 110, thus affecting the opening of the first blind plate floating coupling 100.

[0059] Example 2:

[0060] A method for using a two-stage floating coupling completion string as described in Example 1 includes the following steps:

[0061] S100. Collect basic data on the drilling well: mainly including actual drilling inclination data, drilling fluid density, casing wall thickness, casing steel grade, and section weight.

[0062] S200, calculate the liquid column pressure and check the casing's resistance to external extrusion.

[0063] S300. Determine the position of the floating coupling: Based on software simulation analysis, calculate the length of the floating section sleeve 600 to determine the installation position of the second blind plate floating coupling 200. Based on the pressure setting principle, determine the position of the first blind plate floating coupling 100 so that the first blind plate floating coupling 100 and the second blind plate floating coupling 200 can withstand appropriate liquid column pressure.

[0064] S400, Run the double-stage floating coupling completion string: Install the completion string structure, and run each component in sequence. Among them, the floating section casing 600 and the isolation section casing 400 are not filled with drilling fluid, while the first drilling fluid filling casing 300 and the second drilling fluid filling casing 500 are filled with drilling fluid.

[0065] S500, Open the floating coupling: After the completion string is lowered to the designed well depth, pressurize the wellhead and open the first blind plate floating coupling 100 and the second blind plate floating coupling 200 in sequence.

[0066] S600, Expel air from the casing: Inject drilling fluid and perform static displacement work to displace the air in the floating section of the casing 600 from the wellhead, preventing air from being squeezed into the annulus of the casing and well wall.

[0067] S700, Start the drilling mud pump and enter the cementing preparation stage.

[0068] 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 two-stage floating coupling completion string, characterized in that, It includes a first blind plate type floating coupling (100) and a second blind plate type floating coupling (200), and the first blind plate type floating coupling (100) and the second blind plate type floating coupling (200) have the same structure; The upper end of the first blind plate floating coupling (100) is connected to the first drilling fluid injection casing (300), and the lower end of the first blind plate floating coupling (100) is connected to the isolation section casing (400), wherein the isolation section casing (400) is a closed air section casing. The upper end of the second blind plate type floating coupling (200) is connected to the second drilling fluid filling casing (500), and the lower end of the second blind plate type floating coupling (200) is connected to the floating section casing (600), wherein the floating section casing (600) is a closed air section casing. The end of the isolation section casing (400) opposite to the first blind plate floating coupling (100) is connected to the upper end of the second drilling fluid filling casing (500); The first blind plate floating coupling (100) and the second blind plate floating coupling (200) are configured to open sequentially after the wellhead is pressurized; The first blind plate type floating coupling (100) includes a blind plate (110) and a sliding sleeve (120) disposed below the blind plate (110). A firing pin is provided at one end of the sliding sleeve (120) near the blind plate (110). The first blind plate floating coupling (100) is configured such that when the blind plate (110) is activated, it moves down and strikes the striker, causing the blind plate (110) to generate a stress breakage point.

2. The dual-stage floating coupling completion string according to claim 1, characterized in that... The first blind plate floating coupling (100) also includes a shear ring (130), the shearing pressure of which is lower than the breaking stress of the blind plate (110); The first blind plate floating coupling (100) is configured to cut the shear ring (130) first upon startup, and then push the blind plate (110) downward.

3. The dual-stage floating coupling completion string according to claim 2, characterized in that, The first blind plate type floating coupling (100) also includes a pressure-bearing sliding sleeve (140), which is fitted onto the lower sliding sleeve (120), and the lower end of the pressure-bearing sliding sleeve (140) abuts against the upper side of the shear ring (130); The inner wall of the pressure-bearing sleeve (140) is provided with a pressure-bearing boss (141), and the blind plate (110) is inserted into the pressure-bearing sleeve (140) and abuts against the upper end face of the pressure-bearing boss (141).

4. The dual-stage floating coupling completion string according to claim 3, characterized in that, The first blind plate type floating coupling (100) also includes an isolation sleeve (150), which is inserted into the upper side of the pressure-bearing sliding sleeve (140); The lower end of the isolation sleeve (150) abuts against the upper end of the blind plate (110) and cooperates with the pressure-bearing boss (141) to limit the blind plate (110).

5. The dual-stage floating coupling completion string according to claim 4, characterized in that, The first blind plate type floating coupling (100) also includes a lower connector (160), the upper end of which abuts against the lower side of the shear ring (130); The upper side of the lower connector (160) is fitted onto the lower side of the lower sleeve (120).

6. The dual-stage floating coupling completion string according to claim 5, characterized in that, The first blind plate type floating coupling (100) also includes an upper connector (170), the lower side of which is fitted onto the lower connector (160), and the outer side of the lower connector (160) is provided with a first step (161), and the lower end of the upper connector (170) abuts against the first step (161). The blind plate (110), the sliding sleeve (120), the shear ring (130), the pressure-bearing sliding sleeve (140), and the isolation sleeve (150) are all inserted into the upper connector (170).

7. The dual-stage floating coupling completion string according to claim 6, characterized in that, A first annular space (a) is formed between the lower sliding sleeve (120) and the pressure-bearing sliding sleeve (140), and a second annular space (b) is formed between the lower connector (160) and the upper connector (170). The first annular space (a) and the second annular space (b) are used to ensure the downward movement distance of the pressure-bearing sliding sleeve (140); The side wall of the sliding sleeve (120) is provided with a first through hole, which is connected to the first annular space (a); The lower connector (160) has a second through hole on its side wall, and the second through hole communicates with the second annular space (b).

8. The dual-stage floating coupling completion string according to claim 7, characterized in that, After the first blind plate floating coupling (100) and the second blind plate floating coupling (200) are opened, their inner diameters are consistent with the inner diameter of the casing.

9. A method of using the dual-stage floating coupling completion string as described in claim 8, characterized in that, Includes the following steps: Collect basic data on the drilling well, including actual drilling inclination data, drilling fluid density, casing wall thickness, casing steel grade, and section weight. Calculate the liquid column pressure and check the casing's resistance to external extrusion; Determine the position of the floating coupling: Calculate the length of the floating section sleeve (600) based on software simulation analysis, thereby determining the installation position of the second blind plate floating coupling (200). Determine the position of the first blind plate floating coupling (100) based on the pressure setting principle, so that the first blind plate floating coupling (100) and the second blind plate floating coupling (200) can withstand appropriate liquid column pressure. Run the double-stage floating coupling completion string: Install the completion string structure and run each component in sequence, wherein the floating section casing (600) and the isolation section casing (400) are not filled with drilling fluid, and the first drilling fluid filling casing (300) and the second drilling fluid filling casing (500) are filled with drilling fluid. Open the floating coupling: After the completion string is lowered to the designed well depth, pressurize the wellhead and open the first blind plate floating coupling (100) and the second blind plate floating coupling (200) in sequence. Air removal from casing: Inject drilling fluid and perform static displacement work to displace the air in the floating section of casing (600) from the wellhead, preventing air from being squeezed into the annulus of casing and well wall; Start the drilling mud pump and enter the cementing preparation stage.

Images