Dissoluble shot hole fracturing device

Abstract

The invention discloses a dissoluble shot hole fracturing device which is mainly used for first section fracturing of an oil and gas well and comprises a constant pressure valve, a main body, a gland, a dissoluble plug, a dissoluble gasket and the like. The soluble plug is made of soluble magnesium alloy, the constant pressure valve can set starting pressure according to parameters such as the temperature and the depth of an oil and gas well, after the pressure is reached, the constant pressure valve is opened, the soluble plug and well fluid start to be in contact and dissolved, after a period of time, the soluble plug is completely dissolved, blockages of holes of soluble shot holes disappear, and a shaft is communicated. The soluble blast holes and the casing pipes are put into a well together, the casing pipes are connected like casing pipe couplings, and 5-8 soluble blast holes are formed in a casing pipe string at the bottom of the casing pipes. Casing pipe pressure testing is carried out before fracturing, after a period of time, the soluble plug is dissolved, during fracturing, dissolving of the shot holes is completed, fracturing fluid can enter the stratum through the shot holes, and multi-cluster fracturing is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a soluble blasthole fracturing device. Background Art

[0002] To achieve economic production, low-grade oil and gas wells require staged fracturing. For the initial fracturing stage, three methods are commonly used to connect the formation to the wellbore: continuous perforation, crawler perforation, and toe-end sliding sleeves. Both continuous perforation and crawler perforation have limitations in deep wells and are relatively expensive. Toe-end sliding sleeves, a new technology developed in recent years, can only be deployed twice, effectively fracturing the formation in two clusters, and the success rate is low.

[0003] Before fracturing an oil and gas formation, the entire casing needs to be tested for leaks. Then, the connection between the wellbore and the formation is established to create a channel for fracturing. Soluble blastholes meet both of these requirements. Wellbore leaks are also tested during drilling handover, as the time between drilling handover and fracturing can be quite long. Summary of the Invention

[0004] In order to solve the technical problems existing in the background technology, the present invention aims to provide a soluble blasthole fracturing device. The blasthole is blocked with soluble materials. After the casing sealing test is completed, the soluble material in the blasthole automatically dissolves and the blasthole is connected. Multiple soluble blastholes can be installed at the toe end of the casing, so that multi-cluster fracturing can be achieved.

[0005] In order to solve the technical problem, the technical solution of the present invention is:

[0006] A soluble blasthole fracturing device, wherein a plurality of blasthole holes are radially opened on the cylindrical side wall of the soluble blasthole, each blasthole hole is a multi-step stepped cylindrical hole, and a constant pressure valve, a soluble plug, a rubber pad and a pressure cover are installed in the cylindrical hole from the inside to the outside in sequence; the pressure cover is the outermost component, which is screwed into the cylindrical hole by a thread to compress and fix the internal rubber pad and the soluble plug, and the rubber pad is located between the pressure cover and the soluble plug to isolate the well fluid from the soluble plug, and the soluble plug is located on the inner side of the rubber pad, and the constant pressure valve is installed on the inner side of the blasthole near one end of the wellbore, and is used to rupture when the internal pressure of the wellbore exceeds a preset value, thereby allowing the well fluid to enter the blasthole and contact the soluble plug; the soluble plug is made of a controllable dissolving metal material, and after contacting the well fluid, begins to dissolve at a preset rate until it completely disappears, opening a channel connecting the formation and the wellbore, providing a fluid path for fracturing operations.

[0007] Furthermore, the plurality of blastholes are evenly distributed on the circumference, corresponding to different fracturing directions or clusters.

[0008] Furthermore, after the soluble plug is completely dissolved, a cavity channel is formed inside the blasthole. As the fracturing fluid is injected, the high pressure in the wellbore will forcefully eject the liquid through the blasthole hole, while breaking through the rubber pad and pushing out the pressure cap, opening up a direct connection path with the formation, allowing the fracturing fluid to enter the target layer.

[0009] Furthermore, each blasthole hole is a stepped structure, including a pressure regulating valve installation position, a soluble plug installation position, a sealing ring groove and a gland threaded hole;

[0010] First, place the pressure regulating valve into the bottom of the innermost cylindrical hole of the blasthole, and use the positioning groove or limit shoulder to ensure its correct position;

[0011] Then, a soluble plug made of soluble metal material is inserted into the cavity above the constant pressure valve. The soluble plug should precisely match the aperture to avoid leakage. The soluble plug should conform to the mineralization of the well fluid and the dissolution law of the bottom hole temperature.

[0012] Next, place the rubber pad on the soluble plug. The diameter and thickness of the rubber pad must completely fit the blasthole hole. If there is a sealing ring groove, install the sealing ring at the same time to ensure double sealing.

[0013] Finally, screw the pressure cap into the threaded section of the blasthole and tighten it gradually. During the screwing process, the pressure cap presses the rubber pad to the surface of the soluble plug and tightens it to the specified torque to ensure that the rubber pad is in a reliable compression state.

[0014] Furthermore, the soluble blasthole is a short cylindrical structure; a female thread is provided at its upper end, which can be connected to the male thread of the previous section of casing; a male thread is provided at its lower end, which is connected to the next section of casing or the soluble blasthole section; multiple soluble blastholes can be screwed in series and installed in the lower or middle part of the casing string. After installation, they form a closed wellbore structure with the casing as a whole.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] The soluble blasthole fracturing device of the present invention has significant advantages through innovative design and material selection, especially in the staged fracturing process of low-grade oil and gas wells, which can effectively improve operating efficiency and reduce costs.

[0017] First, the implementation of multi-cluster fracturing is a major highlight of this invention. By installing multiple soluble blastholes at the toe of the casing or other appropriate locations, directional multi-cluster fracturing can be achieved, effectively developing different intervals. This design not only improves the development efficiency of oil and gas wells but also reduces operational complexity and costs. In particular, compared to traditional perforating and sliding sleeve technologies, it offers greater operational flexibility and lower costs.

[0018] Secondly, the simplified structural design makes the device easier to install and use within the wellbore. The soluble blasthole is connected to the casing via threads, and the installation process is similar to conventional casing installation, making it compatible with existing technologies and eliminating the need for complex perforating operations or multiple operations, saving construction time.

[0019] Another advantage of this device is its reliable sealing performance. The rubber pad and gland effectively prevent premature contact between the wellbore fluid and the soluble plug, ensuring that the soluble plug will not dissolve prematurely before fracturing, thus ensuring the stability and safety of the operation.

[0020] Finally, the efficient dissolution technology enables the soluble plug to dissolve smoothly during the fracturing process, quickly establishing a connecting channel with the formation, providing a smooth path for the injection of fracturing fluid, and ensuring the fracturing effect.

[0021] In summary, the soluble blasthole fracturing device of the present invention has significant advantages in reducing costs, improving efficiency, and ensuring safety, and is particularly suitable for oil and gas well development in complex formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic cross-sectional structure diagram of the present invention;

[0023] Figure 2 It is a schematic diagram of the main structure of the present invention;

[0024] Figure 3 It is a schematic diagram of the blasthole structure of the present invention. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described below in conjunction with examples:

[0026] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0027] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0028] Example 1:

[0029] like Figure 1As shown, a soluble blasthole includes a main body 1, on which a plurality of cylindrical holes (blastholes) are processed from the outside to the inside, and in these cylindrical holes, a constant pressure valve 2, a soluble plug 3, a rubber pad 4, and a pressure cover 5 are installed in sequence from the inside to the outside.

[0030] The rubber pad 4 is pressed against the soluble plug 3 by the gland 5 to prevent the well fluid from coming into contact with the soluble plug 3 and dissolving.

[0031] The day before fracturing or 5-6 hours before, a wellbore sealing pressure test is carried out. During the pressure test, the constant pressure valve 2 is broken, and the well fluid contacts the soluble plug 3 and begins to dissolve. After a certain period of time, the soluble plug 3 is completely dissolved, and the blasthole is unobstructed, providing a channel for fracturing.

[0032] like Figure 2 The main body 1 includes a thread 21 on the upper end, outer cylindrical surfaces 22 and 23 from left to right, a thread 24 on the lower end, and an inner cylindrical surface with a through hole 25 that is equal to (matched to) the inner diameter of the connecting sleeve. A plurality of radial holes 26 (blast holes) are processed on the cylindrical surface 23.

[0033] like Figure 3 As described above, multiple radial holes 26 (blastholes) are machined on the cylindrical surface 23, cylindrical holes 31, 32, 33 are machined from the outside to the inside of the circular hole 26, and a sealing ring groove 34 is machined on the cylindrical hole. Eyelet thread sections 35 are machined on the cylindrical hole, and the gland 5 is connected through the threads 35.

[0034] Multiple soluble blastholes are installed at the toe of the casing, one per casing, or a shorter distance installation is performed using a casing nipple, to achieve multi-cluster fracturing at the toe of the oil and gas well, and also to achieve fracturing at any position of the layer above the bottom of the well.

[0035] Example 2:

[0036] This embodiment 2 is applied to embodiment 1, and further explains the working principle and process of a soluble blasthole fracturing device in embodiment 1 in detail.

[0037] Structural relationship between soluble blasthole and casing:

[0038] During installation, the soluble blasthole is not integral to the casing, but is connected to the casing through a threaded connection. The soluble blasthole is essentially a special connecting nipple, similar in structure and appearance to the casing, but with multiple radial blasthole holes machined on its cylindrical sidewall. This structure is connected to the casing in the following ways:

[0039] With female thread on the upper end and male thread on the lower end (or vice versa), like a casing coupling;

[0040] When running into the well, multiple soluble blasthole sections are installed at the bottom of the casing string, such as 5 to 8 in series;

[0041] They are connected to the casing in a section-by-section screw-on manner, and the installation position is controllable, which facilitates segmented design;

[0042] Compared with ordinary casing, its differences lie in the existence of blasthole structure, internal components (pressure regulating valve, soluble plug, etc.) and sealing structure.

[0043] Relationship between installation and fracturing workflow:

[0044] Run together with casing: the soluble blasthole and other casing together form a casing string and run into the well to form a closed system;

[0045] After cementing is completed: before fracturing, perform casing pressure test;

[0046] Start the constant pressure valve: a few hours before fracturing (such as the day before or 5-6 hours), the downhole pressure reaches the set value to open the constant pressure valve;

[0047] The soluble plug begins to dissolve: after contacting with the well fluid, it completely dissolves within the set time;

[0048] Fracturing fluid enters the formation: the blastholes are opened, and the fracturing fluid enters different formation sections from multiple blastholes to achieve multi-cluster fracturing.

[0049] To further explain, the outside of the gland 5 is exposed to the well fluid, but due to the cooperative sealing of the gland, rubber gasket and soluble plug, the well fluid cannot contact the inside of the soluble plug, thereby preventing premature dissolution.

[0050] The casing is filled with well fluid (drilling fluid / fracturing fluid) for a long time:

[0051] After the well is completed, the inside of the casing is always filled with well fluid;

[0052] The blasthole is a hole on the side wall of the casing, that is, the well fluid also covers the outside of the gland 5;

[0053] Therefore, it can be said that the outside of the gland 5 is always in the well fluid.

[0054] To further explain why the soluble plug doesn't dissolve prematurely, the reason is that the gland 5 is screwed into the blasthole, forming a physical seal. The rubber pad 4 fits snugly between the soluble plug 3 and the gland, providing a seal and isolation. This entire seal prevents well fluid from seeping into the blasthole, thus protecting the soluble plug from contact with the well fluid before fracturing.

[0055] To further explain, under what circumstances does dissolution begin? The wellbore pressure rises, rupturing constant-pressure valve 2 first. This opens the blasthole, allowing well fluid to enter the blasthole. The rubber gasket 4 fails due to rupture / deformation / pressure, allowing well fluid to flow into and contact the soluble plug 3. At this point, the dissolution timer for the soluble plug begins.

[0056] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

[0057] Many other changes and modifications can be made without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A soluble blasthole fracturing device, characterized in that: A plurality of blasthole holes are radially opened on the cylindrical side wall of the soluble blasthole, and each blasthole hole is a multi-step cylindrical hole. A constant pressure valve (2), a soluble plug (3), a rubber pad (4) and a pressure cover (5) are sequentially arranged in the cylindrical hole from the inside to the outside; the pressure cover (5) is screwed into the cylindrical hole by a thread, pressing and fixing the rubber pad (4) and the soluble plug (3) inside, the rubber pad (4) isolates the well fluid from the soluble plug (3), the soluble plug (3) is located on the inner side of the rubber pad, and the constant pressure valve (2) is installed on the inner side of the blasthole near one end of the wellbore, and is used to open when the pressure in the wellbore exceeds a preset value, so that the well fluid can enter the blasthole and contact the soluble plug (3); the soluble plug (3) is made of a controllable dissolving metal material, and begins to dissolve at a preset rate after contacting the well fluid until it completely disappears, opening a channel connecting the formation and the wellbore, and providing a fluid path for the fracturing operation.

2. A soluble blasthole fracturing device according to claim 1, characterized in that: The multiple blastholes are evenly distributed on the circumference, corresponding to different fracturing directions or clusters.

3. A soluble blasthole fracturing device according to claim 1, characterized in that: After the soluble plug (3) is completely dissolved, a cavity channel is formed inside the blasthole. As the fracturing fluid is injected, the high pressure in the wellbore will forcefully eject the liquid through the blasthole hole, breaking through the rubber pad (4) and flowing out of the gland (5), thus opening a direct communication path with the formation and allowing the fracturing fluid to enter the target layer.

4. A soluble blasthole fracturing device according to claim 1, characterized in that: Each blasthole hole is a stepped structure, comprising a pressure regulating valve (2) installation position, a soluble plug installation position, a sealing ring groove and a gland threaded hole; First, place the constant pressure valve (2) into the bottom of the innermost cylindrical hole of the blasthole, and use the positioning groove or limit shoulder to ensure its correct position; Then, a soluble plug (3) made of soluble metal material is embedded in the cavity above the constant pressure valve (2). The soluble plug (3) should be precisely matched with the hole diameter to avoid leakage. The soluble plug (3) should conform to the mineralization of the well fluid used and the dissolution law of the bottom hole temperature; Next, place the rubber pad (4) on the soluble plug. The diameter and thickness of the rubber pad (4) must completely fit the blasthole hole and be provided with a sealing ring groove (34). Then, install the sealing ring simultaneously to ensure double sealing. Finally, screw the gland (5) into the blasthole threaded section (35) and tighten it gradually. During the screwing process, the gland (5) presses the rubber pad (4) to the surface of the soluble plug (3) and tightens it to the specified torque to ensure that the rubber pad (4) is in a reliable compression state.

5. The soluble blasthole fracturing device according to claim 1, characterized in that: The soluble blasthole is a short cylindrical structure; its upper end is provided with a female thread, which can be connected to the male thread of the previous section of casing; the lower end is provided with a male thread, which is connected to the next section of casing or the soluble blasthole section; multiple soluble blastholes can be screwed in series and installed in the lower or middle part of the casing string. After installation, they form a closed wellbore structure with the casing as a whole.

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