Metal-soluble seal assembly and horizontal well fracturing process

Abstract

The application discloses a metal soluble sealing assembly and a horizontal well staged fracturing process. The metal soluble sealing assembly comprises a connecting body, a releasing hand (12) arranged at the lower end of the connecting body, a necking portion and an inner cavity of the releasing hand, and the inner cavity contains a dissolving agent (13). A setting mechanism is arranged axially along the connecting body. After the setting mechanism is set in a casing (20), the thickness between the cross section of the releasing hand (12) cut from the necking portion (12-1) and the inner cavity is smaller than the wall thickness of other parts of the inner cavity. The problems that the existing bridge plug cannot simultaneously consider the pressure-bearing capacity and the dissolving rate in some special cases and the problem that the dissolving rate adjustment is limited for different working conditions are solved.

Description

Technical Field

[0001] This disclosure relates to a metal soluble sealing assembly for large-scale staged fracturing processes in horizontal wells, used to set the casing to withstand the high pressure during fracturing, requiring good pressure-bearing reliability, and the assembly needs to dissolve as soon as possible after fracturing to form a production channel to meet the purpose of rapid production. Background Technology

[0002] The statements in this section provide only background information in connection with this disclosure and do not constitute prior art.

[0003] Metal soluble sealing components are primarily used in large-scale staged fracturing processes in horizontal wells. During fracturing, the components need to withstand high pressure and possess good pressure-bearing reliability; after fracturing, the components need to dissolve quickly to form production channels to achieve rapid production. Therefore, the design of sealing components needs to balance pressure-bearing capacity and dissolution rate, improving the dissolution rate of the components after fracturing while meeting pressure-bearing requirements.

[0004] The main factors affecting the dissolution rate of the sealing components are the chloride concentration in the well fluid and the bottom hole temperature. Differences in chloride concentration and bottom hole temperature between different well conditions cause insufficient dissolution of some components. For components that are not fully dissolved downhole, well cleaning, milling, and other treatment processes are required, which increases construction costs and affects the application effect of the sealing components.

[0005] ZL201921650684.4 discloses a soluble bridge plug (i.e., a metal soluble sealing assembly) that facilitates rapid dissolution. To improve the dissolution rate of the bridge plug, a soluble fracturing ball is carried by a conical sleeve of the soluble bridge plug. The soluble fracturing ball is filled with a solubilizing powder and is made of a soluble material. After the soluble fracturing ball dissolves, the solubilizing powder in the inner cavity of the ball can be quickly dispersed and dissolved into various components of the bridge plug, thus accelerating the dissolution of the bridge plug.

[0006] However, firstly, the bridge plugs used in horizontal well fracturing operations need to undergo pumping, fracturing, and dissolution processes. If a component of the bridge plug is accidentally damaged during pumping or fracturing, or if the component dissolves prematurely due to special circumstances such as construction stoppage during fracturing, it will have a serious adverse impact on the pressure-bearing reliability of the bridge plug.

[0007] Secondly, the amount of co-solvent carried by the fracturing soluble ball is fixed, and the amount of co-solvent carried cannot be easily adjusted, thus limiting its adaptability to different working conditions.

[0008] Thirdly, in order to ensure the reliability of the seal before fracturing, the outer soluble metal layer of the fracturing soluble ball is relatively thick. When the bridge plug needs to be dissolved more quickly after the fracturing operation, the thickness of the metal layer will directly affect the release time of the solubilizing powder. The thicker the soluble metal layer, the longer the release time of the solubilizing powder, which will affect the effect of accelerating dissolution.

[0009] Fourthly, after fracturing operations are completed, well cleaning is usually used to determine whether the soluble bridge plug has completely dissolved, which is costly.

[0010] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art. Summary of the Invention

[0011] In view of at least one of the above technical problems, this disclosure provides a metal soluble sealing assembly with a new structural form, which solves the problem that the existing bridge plugs, which use fracturing soluble balls to accelerate dissolution, cannot simultaneously take into account pressure bearing capacity and dissolution rate under some special conditions, and the problem that the dissolution rate adjustment is limited for different working conditions.

[0012] In addition, this disclosure also provides a horizontal well staged fracturing process using metal soluble sealing components.

[0013] In a first aspect, the metal-soluble sealing assembly is characterized by comprising:

[0014] The connecting body has a handle at its lower end, the handle has a constricted neck and an inner cavity, and the inner cavity contains a co-solvent.

[0015] A setting mechanism is provided along the axial direction of the connecting body. After the setting mechanism completes the setting inside the sleeve, the thickness between the cut surface where the release hand is cut off from the neck and the inner cavity is less than the wall thickness of other parts of the inner cavity.

[0016] In the embodiments or possible embodiments disclosed herein, an identifier is provided in the connecting body. The identifiers used in each stage of horizontal well fracturing are different. After the connecting body is dissolved, the identifier falls into the casing and is transported to the wellhead by its own buoyancy or with the flowback fluid and captured by the catcher.

[0017] In the embodiments or possible embodiments of this disclosure, the connecting body includes an upper cone and a lower cone. The connecting body is delivered to a predetermined position by a setting tool connected to the upper cone. A first inclined surface is provided at the lower end of the upper cone, and a second inclined surface is provided at the upper end of the lower cone. The setting mechanism is fixed between the first inclined surface and the second inclined surface by shear pins.

[0018] During the setting process, the setting tool applies a force to drive the upper cone to axially displace and cut the shear pin. Then, the setting mechanism expands radially under the constraint of the first and second inclined planes to complete the setting.

[0019] In the embodiments or possible embodiments disclosed herein, the setting mechanism includes a slip assembly, the upper end of which overlaps with the upper cone through the constraint of a sealing ring, and the lower end of which is connected to the lower cone through a pin; when the sealing ring expands radially along with the slip assembly to fit against the inner wall of the sleeve, it seals the annular space between the upper cone and the sleeve and completes the anchoring.

[0020] In the embodiments or possible embodiments disclosed herein, the setting mechanism further includes a locking mechanism, the locking mechanism including a cylinder with a spring claw at the upper end, the cylinder being connected to the lower cone, a first locking tooth being provided on the outer side of the spring claw, and a second locking tooth being provided on the inner wall of the upper cone, wherein when the slip assembly is anchored on the inner wall of the sleeve, the first locking tooth is locked onto the second locking tooth.

[0021] In embodiments or possible embodiments of this disclosure, the axially extending end of the constricted neck is connected to a pull rod, and when it is necessary to cut the constricted neck, the force applied by the setting tool to the upper cone is converted into a shearing force to cut the constricted neck through the pull rod.

[0022] In embodiments or possible embodiments of this disclosure, the inner cavity of the hand-dropping device is provided with an interface, the interface being sealed to a plug.

[0023] Secondly, the horizontal well staged fracturing process based on the metal soluble sealing assembly described in the first aspect is characterized by comprising:

[0024] In horizontal well segmented fracturing operations, the aforementioned soluble metal sealing components are installed in each fracturing stage except for the first stage.

[0025] In the embodiments or possible embodiments of this disclosure, after the sealing assembly is set in the current fracturing stage, the release mechanism of the metal soluble sealing assembly falls into the next fracturing stage, releasing the solvent within the release mechanism to assist in the dissolution of the sealing assembly in the next fracturing stage.

[0026] In embodiments or possible embodiments of this disclosure, markers are captured after the horizontal well is fracturing in stages, and the metal soluble sealing components of the corresponding segment are determined by the markers to see if they have dissolved.

[0027] This disclosure has the following beneficial effects:

[0028] The metal soluble sealing assembly disclosed herein features a release handle filled with a fluxing agent. In horizontal well staged fracturing, this sealing assembly is installed in each stage except the initial stage. After the sealing assembly of the current stage is set and before fracturing operations begin, the release handle is cut and pumped to the next stage. Because the distance between the fracture surface of the release handle and the inner cavity is less than the wall thickness of other parts of the inner cavity, the fracture surface is dissolved first to release the fluxing agent in the inner cavity. The fluxing agent combines with the well fluid to accelerate the dissolution rate of the sealing assembly in the next stage of fracturing without affecting the pressure-bearing capacity of the sealing assembly in the current stage of fracturing, thus achieving a balance between pressure-bearing capacity and dissolution rate. Furthermore, the amount of fluxing agent filled in the inner cavity of the release handle can be adjusted according to the operating conditions, thereby adjusting the dissolution rate accordingly. This solves the problem that the amount of fluxing agent that can be filled in the fracturing soluble ball used in existing bridge plugs is fixed, resulting in limited adjustment of the dissolution rate under different operating conditions. Attached Figure Description

[0029] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0030] Figure 1 This is a schematic diagram of the structure of a metal soluble sealing assembly according to an embodiment of this disclosure;

[0031] Figure 2 This is a schematic diagram of the connection between the identifier and the components according to an embodiment of this disclosure;

[0032] Figure 3 This is a schematic diagram of a spring claw according to an embodiment of the present disclosure;

[0033] Figure 4 This is a schematic diagram of the connection state structure of the components before being seated according to an embodiment of this disclosure;

[0034] Figure 5 This is a schematic diagram of the component's seated state structure according to an embodiment of the present disclosure;

[0035] Figure 6 This is a schematic diagram of the accelerated dissolution of the previous stage component according to an embodiment of this disclosure. Detailed Implementation

[0036] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0037] Furthermore, those skilled in the art should understand that the accompanying drawings are only for illustrating the purpose, features, and advantages of this disclosure, and are not actually drawn to scale. The component designations used herein, such as "first," "second," etc., are merely for distinguishing the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). In the description of this application, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this application.

[0038] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0039] Figure 1 This is a schematic diagram of the structure of a metal soluble sealing assembly according to an embodiment of this disclosure; by Figure 1 As shown, the metal soluble sealing assembly includes a connecting body with a release handle 12 at its lower end. The release handle 12 has a neck 12-1 and an inner cavity. The inner cavity contains a fluxing agent 13. The thickness between the section of the release handle 12 that is cut off from the neck 12-1 and the inner cavity is less than the wall thickness of other parts of the inner cavity. A setting mechanism is provided along the axial direction of the connecting body. After the setting mechanism completes the setting within the casing 20, the release handle 12 is cut off from the neck 12-1 and pumped to the next higher fracturing section of this fracturing section.

[0040] exist Figure 1 In this embodiment of the present disclosure, a marker 3 is provided in the connecting body. The markers 3 used in each segment of the horizontal well fracturing are different. For example, the markers in the connecting body of the sealing components in different segments are different colors, or the markers adopt the same structure, but additional distinguishing marks or structures are set on the structure. After the connecting body is dissolved, the marker 3 falls into the casing 20 and is transported to the wellhead by its own buoyancy or with the flowback fluid and captured by the catcher. The marker 3 is made of a lightweight material, such as plastic. Of course, other lightweight materials that are not easily corroded and destroyed by well fluid can also be used. This disclosure does not limit the marker.

[0041] exist Figure 1In this embodiment, the connecting body includes an upper cone 4 and a lower cone 11. The connecting body is delivered to a predetermined position by a setting tool 30 connected to the upper cone 4. A first inclined surface is provided at the lower end of the upper cone 4, and a second inclined surface is provided at the upper end of the lower cone 11. The setting mechanism is fixed between the first and second inclined surfaces by shear pins. During the setting process, the setting tool 30 applies a force to the upper cone 4. Driven by this force, the upper cone 4 undergoes axial displacement, thereby cutting the shear pins. Driven by the continuous axial displacement of the upper cone 4 and constrained by the first and second inclined surfaces, the setting mechanism expands outward in the radial direction, ultimately achieving the setting purpose.

[0042] exist Figure 1 In this embodiment, the sealing mechanism includes a slip assembly 8. The upper end of the slip assembly 8 is connected to the upper cone 4 by a sealing ring 5, and the lower end is connected to the lower cone 11 by a pin 9. Slip teeth are provided on the outer wall of the slip assembly 8. When the sealing ring 5 expands radially with the slip assembly 8 to fit against the inner wall of the sleeve 20, it seals the annular space between the upper cone 4 and the sleeve 20. The upper end of the slip assembly 8 is also provided with a spacer ring 6. Under the action of the slip assembly 8, the sealing ring 5 and the spacer ring 6 expand radially to fit against the inner wall of the sleeve 20, sealing the annular space between the upper cone 4 and the sleeve 20. Simultaneously, the slip assembly 8 and the lower cone 11 undergo radial relative displacement, shearing the pin 9, and the slip assembly 8 breaks through the constraint of the spacer ring 6 and anchors to the inner wall of the sleeve 20.

[0043] exist Figure 1 In this embodiment of the present disclosure, the sealing mechanism further includes a locking mechanism, which includes a cylinder 10 with a spring claw 10-1 at its upper end, such as... Figure 3 As shown; in this embodiment, there are 6 spring claws. A first locking tooth is provided on the outer side of the spring claw 10, and a second locking tooth is provided on the inner wall of the upper cone 4. The cylinder 10 and the lower cone 11 are threadedly connected. When the slip assembly 8 is anchored on the inner wall of the sleeve 20, the first locking tooth is locked onto the second locking tooth. In the initial state, a shear pin 7 is provided between the upper cone 4 and the cylinder 10, and the cylinder 10 and the lower cone 11 are threadedly connected. The upper cone 4, the cylinder 10, the setting mechanism, and the lower cone 11 are connected together.

[0044] exist Figure 1 In this embodiment, the lower end of the lower cone 11 overlaps with the release handle 12, and the axial extension end of the constricted neck 12-1 of the release handle 12 is connected to the pull rod 40. When it is necessary to cut the constricted neck 12-1, the force applied by the setting tool 30 to the upper cone 4 is converted into a shearing force to cut the constricted neck 12-1 through the pull rod 40.

[0045] exist Figure 1In this embodiment, the inner cavity of the dropper 12 is provided with an interface, which is connected to a plug 15. A sealing ring 14 is provided at the interface of the plug 15 to seal the inner cavity of the dropper 12 and protect the flux 13 filled in the inner cavity. The flux 13 in this disclosure is KCL powder. The plug 15 is opened, the flux 13 is filled, and the plug 15 is closed after filling. The amount of flux 13 filled in the inner cavity can be adjusted according to different downhole operating conditions, that is, the amount of flux 13 filled in the inner cavity is not fixed.

[0046] The connection relationships of the metal soluble sealing assembly according to embodiments of this disclosure will be described in detail below with reference to the accompanying drawings:

[0047] like Figure 2 As shown, four markers 3 are inserted into the holes of the upper cone 4, and then connected to the upper cone 4 by pins 2; sealing rings 5 ​​and spacers 6 are fitted onto the upper cone 4, shear pins 7 are connected to the upper cone 4 by threads, and the upper end of the nine clamping assembly 8 overlaps with the upper cone 4 and is embedded in the spacers 6, while the lower end is connected to the lower cone 11 by pins 9; as shown Figure 3 As shown, the upper end of the spring claw 10 is connected to the upper cone 4 via six strips 10-1 with locking teeth, and the lower end is threaded to the lower cone 11. The release handle 12 is connected to the lower cone 11. The solvent 13 is inserted into the cavity at the lower end of the release handle 12. The O-ring 14 is embedded in the plug 15. The plug 15 is threaded to the release handle 12, thereby sealing the solvent 13 in the cavity at the lower end of the release handle 12.

[0048] The components of this embodiment are made of the following materials: the shear pin 7 is made of 45 steel, the O-ring 14 is made of rubber, the marker 3 is made of plastic, the flux is KCL powder, the slip teeth in the slip assembly 8 are made of ceramic material, and the remaining components are made of magnesium-based soluble alloy material.

[0049] The following is a description of a horizontal well fracturing process using a metal soluble sealing assembly according to an embodiment of this disclosure, with reference to the accompanying drawings:

[0050] The first stage of fracturing in each well (the first stage) uses a pipe-driven perforation or other means to form a flow channel. Starting from the second stage of fracturing, the sealing components of this disclosure are delivered to carry out segmented fracturing.

[0051] For the second-stage fracturing section, the first-stage sealing assembly is deployed by using a cable to deliver the perforating gun, matching setting tool, and sealing assembly to the predetermined position, and then setting the sealing assembly. Figure 4 As shown, before setting, the setting tool pull rod 40 is threadedly connected to the release handle 12, and the setting tool outer sleeve 30 is connected to the upper cone 4.

[0052] During setting, the setting tool sleeve 30 pushes the upper cone 4 axially. The sealing ring 5, spacer ring 6, shear pin 7, slip assembly 8, spring claw 10, lower cone 11, release handle 12, flux 13, O-ring 14, and plug 15 generate axial relative displacement with the upper cone 4. The shear pin 7 is sheared off. Under the action of the slip assembly 8, the sealing ring 5 and spacer ring 6 expand radially to fit against the inner wall of the casing, sealing the annular space between the upper cone 4 and the casing 20. Simultaneously, the slip assembly 8 and lower cone 11 generate radial relative displacement, the pin 9 is sheared off, and the slip assembly 8 breaks through the constraint of the spacer ring 6 and anchors to the inner wall of the casing. At this time, the six locking teeth on the upper end of the spring claw 10 engage with the locking teeth inside the upper cone 4 to achieve locking. Figure 5 As shown, the component enters the setting state; after setting is completed, perforation is carried out, and then the matching setting tools and perforation gun are taken out, soluble balls are put in, and the soluble balls are pumped to the component position to seal the central channel of the component before carrying out fracturing construction in this section (second-stage fracturing section).

[0053] Before carrying out the fracturing operation in this section, the outer sleeve of the setting tool 30 continues to apply displacement through the upper cone 4, and the release tool 12 is sheared off at the necking point 12-1, as... Figure 5 As shown, the release 12, along with the flux 13, O-ring 14, and plug 15, detaches into the casing 20. Similarly, except for the release 12, flux 13, O-ring 14, and plug 15 of the first-stage sealing assembly that detach into the casing and are pumped to the bottom of the well, the release 12, flux 13, O-ring 14, and plug 15 of the sealing assemblies in the remaining fracturing sections are all pumped to the vicinity of the top of the next-stage sealing assembly, such as... Figure 6 As shown, the release 12 of the sealing assembly of the Nth stage fracturing segment 200 falls off to near the top of the sealing assembly of the N-1th stage fracturing segment 100.

[0054] Because the cross-section of the necking point 12-1 and the inner cavity wall of the fluxing agent 13 are as thin as possible, for example, only 1.5-2.5 mm, this cross-section is a weak point relative to other parts of the inner cavity. This weak point will be dissolved first, releasing the fluxing agent KCl powder. Before the sealing components of the previous fracturing section lose their anchoring function, the fluxing agent 12 comes into contact with the well fluid, rapidly increasing the chloride concentration of the well fluid around the sealing components in the previous fracturing section, thus aiding in the dissolution of the sealing components in the previous fracturing section, i.e., accelerating the dissolution rate of the sealing components in the previous fracturing section that has already completed fracturing. For the sealing components in the last fracturing section, since they have not fallen to this stage, there is no fluxing agent to accelerate the dissolution of the components in this stage. Therefore, a KCl solution with a concentration of 1% and 1.5 times the volume of the wellbore of the corresponding section is pumped in to assist in the dissolution of the sealing components in the last fracturing section. Because the fluxing agent detaches and falls to the next fracturing stage without being released into the current fracturing stage, it does not accelerate the dissolution of the sealing components in this stage. Therefore, even if a component of the sealing components in this stage is accidentally damaged or special circumstances such as a work stoppage occur during fracturing, the sealing components in this stage will not dissolve prematurely. The pressure-bearing reliability of the sealing components in this stage will not be adversely affected, thus effectively ensuring its pressure-bearing capacity.

[0055] Since the previous fracturing segment is a segment that has already been fractured, the flux 13 accelerates the dissolution of the sealing components in the previous fracturing segment without interfering with the pressure-bearing capacity of the sealing components in this fracturing segment, thus ensuring the fracturing operation of this fracturing segment. Therefore, the sealing components disclosed in this invention achieve a balance between pressure-bearing capacity and dissolution rate, and improve the dissolution rate of the post-fracturing components while meeting the pressure-bearing requirements.

[0056] As the upper cone 4 of the component dissolves, the slip assembly 8 loses its support, and the undissolved residue of the sealing component falls into the casing 20. Among them, the marker 3 falls into the casing 20 and is transported to the wellhead by its own buoyancy or with the backflow and production fluid, where it is captured by the trap. Since the marker 3 of different components has different colors and the components are set at different depths in the well, the dissolution status of components at different depths can be intuitively and conveniently judged based on the color and number of captured marker 3.

[0057] The sealing assembly described in this embodiment is used in the field as follows:

[0058] The disclosed sealing component (Level 3) was applied in a staged fracturing operation on a horizontal well. The well was drilled to a depth of 3077m, with a horizontal section length of 1103m. The formation temperature was 97.5℃, and the chloride concentration was 1247mg / L. A total of 14 stages of staged fracturing were performed, using a soluble bridge plug (Level 13). Stages 2-11 used other types of soluble bridge plug tools, while the disclosed sealing component was applied in stages 12-14. The construction steps are as follows:

[0059] Step 1: Connect the perforating gun, matching setting tool, and soluble sealing assembly using a cable (each sealing assembly carries 30g of KCl powder as a co-solvent; the identifier for the 12th stage is red, the 13th stage is yellow, and the 14th stage is blue). Deploy the tool string to the predetermined depth, set the assembly, and perform the perforation operation. Remove the perforating gun and matching setting tool from the wellhead.

[0060] Step 2: Drop the soluble pellets into the well and pump them to the component depth, then carry out fracturing operations according to the fracturing design requirements.

[0061] Step 3, Sections 12 and 13 repeat Step 1 and Step 2. When the fracturing operation enters the displacement stage in Section 14 (the last section), pump in a KCl solution with a concentration of 1% and a volume of 1.5 times the corresponding wellbore.

[0062] Step 4: After 48 hours of well shut-in, blowout prevention and backflow prevention began. On the first day of blowout prevention, 3 blue markers, 3 yellow markers, and 2 red markers were captured. On the second day of blowout prevention, 1 blue marker was captured, for a total of 9 markers. The total time from well shut-in to completion was 4 days (indoor tests showed that under conditions of 90℃, chloride concentration of 1000mg / L, and no release of co-solvent, the complete dissolution test of the components used in sections 12-14 took 7 days). The remaining markers could not be captured due to sand. Among them, only 2 markers were captured for the sealing component corresponding to section 12, indicating that sand production in section 12 was more serious.

[0063] Step 5: 25 days after the pressure construction is completed, sand flushing and well cleaning operations are carried out. There is no obstruction at the setting position of the components in sections 12-14, and the component dissolution effect is good.

[0064] As can be seen from the above embodiments and application examples, the metal soluble sealing component for large-scale segmented fracturing of horizontal wells disclosed herein adopts a drop-and-carry method to accelerate the dissolution rate of the component in the already fracturing segment. It has the advantages of reliable pressure-bearing performance, fast dissolution rate, and intuitive and convenient judgment of the component's dissolution state.

[0065] Furthermore, the amount of flux carried by different fracturing sections can be easily adjusted according to specific well conditions, and the dissolution time of the components can be controlled.

[0066] Furthermore, the dissolution state of the component is determined by capturing the number and color of the markers. The determination method is simple, intuitive, and low in cost.

[0067] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A metal-soluble seal assembly, characterized by, Comprising: a connecting body, the lower end of which is provided with a drop-off (12), the drop-off is provided with a necking portion and an inner cavity, the inner cavity contains a dissolving agent (13); an axial setting mechanism is provided along the connecting body, after the setting mechanism is set in the casing (20), the thickness between the cross section of the drop-off (12) being cut off from the necking portion (12-1) and the inner cavity is less than the wall thickness of other parts of the inner cavity.

2. The metal dissolvable sealing assembly according to claim 1, characterized in that: an identifier (3) is provided in the connecting body, the identifier (3) used for each layer of the horizontal well staged fracturing is different, after the connecting body is dissolved, the identifier (3) falls into the casing (20) and is transported to the wellhead by the self buoyancy or the flowback fluid and is captured by the catcher.

3. The metal dissolvable sealing assembly according to claim 1 or 2, characterized in that: the connecting body comprises an upper cone (4) and a lower cone (11), the connecting body is delivered to the predetermined position by the setting tool connected with the upper cone (4), the lower end of the upper cone (4) is provided with a first inclined surface, the upper end of the lower cone (11) is provided with a second inclined surface, the setting mechanism is fixed between the first inclined surface and the second inclined surface by the shear pin respectively; during the setting process, the setting tool (30) applies a force to drive the upper cone (4) to axially displace to cut off the shear pin, then the setting mechanism is radially expanded under the constraint of the first inclined surface and the second inclined surface to complete the setting.

4. The metal dissolvable sealing assembly according to claim 3, characterized in that: the setting mechanism comprises a slip assembly (8), the upper end of the slip assembly (8) is overlapped with the upper cone (4) by the constraint of the sealing ring (5), the lower end of the slip assembly (8) is connected with the lower cone (11) by the pin (9); when the sealing ring (5) is radially expanded to be attached to the inner wall of the casing (20) with the slip assembly (8), the sealing ring (5) seals the annular space between the upper cone (4) and the casing (20) and completes anchoring.

5. The metal dissolvable sealing assembly according to claim 4, characterized in that: the setting mechanism further comprises a locking mechanism, the locking mechanism comprises a cylinder body provided with a spring claw at the upper end, the cylinder body is connected with the lower cone (11), the outer side of the spring claw is provided with a first locking tooth, the inner wall of the upper cone (4) is provided with a second locking tooth, when the slip assembly (8) is anchored on the inner wall of the casing (20), the first locking tooth is locked on the second locking tooth.

6. The metal dissolvable sealing assembly according to claim 4 or 5, characterized in that: the axial extension end of the necking portion (12-1) is connected with a pull rod (40), when the necking portion (12-1) needs to be cut off, the force applied by the setting tool (30) to the upper cone (4) is converted into the shear force for cutting off the necking portion (12-1) through the pull rod (40).

7. The metal dissolvable sealing assembly according to claim 6, characterized in that: The inner cavity of the releasing head (12) is provided with an interface, and the interface is sealingly connected with a plug (15).

8. A process for the staged fracturing of a horizontal well based on the metal-soluble seal assembly according to any one of claims 2 to 7, characterized in that, The method comprises the following steps: In the horizontal well staged fracturing operation, the metal soluble sealing assembly is arranged in each fracturing layer segment except the first segment.

9. The horizontal well staged fracturing process according to claim 8, characterized in that: After the metal soluble sealing assembly is set in the current fracturing layer segment, the releasing head (12) falls off into the upper fracturing layer segment, and the dissolving agent (13) in the releasing head (12) is released to assist the dissolution of the sealing assembly in the upper fracturing layer segment.

10. The horizontal well staged fracturing process according to claim 9, characterized in that: After the horizontal well staged fracturing, an identifier is captured, and whether the metal soluble sealing assembly of the layer segment corresponding to the identifier is dissolved is determined through the identifier.

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