Assembly type liquid nitrogen fracturing shaft

Abstract

The utility model discloses a liquid nitrogen fracturing shaft capable of being assembled, and relates to the field of indoor petroleum engineering tests, in particular to a petroleum engineering test device, which comprises an external shaft, an internal shaft, a gasket and a base. Wherein the external shaft plays a supporting and connecting role, is communicated with the liquid nitrogen injection pipe through threads and is connected with the internal shaft, and cross-shaped lines formed by embedding pieces at the upper end of the external shaft can enhance the stability of the shaft. The internal shaft is used for guiding liquid nitrogen fracturing fluid, and holes in the boundary of the internal shaft can effectively exhaust a large amount of gas generated by liquid nitrogen phase change. After the liquid nitrogen reaches the bottom end of the shaft, the gasified liquid nitrogen jacks up the gasket to reach the top of the shaft, the gasket and the cross-shaped lines on the external shaft form a whole, and a closed fracturing environment is created. The base is connected with an internal shaft through threads so that the gasket can be prevented from sliding off in the early liquid injection stage. The matching design can effectively solve the problem that fracturing fluid is difficult to inject due to liquid nitrogen gasification, and an indoor manual sample liquid nitrogen fracturing experiment is achieved.

Description

Technical Field

[0001] This experimental application relates to the field of indoor petroleum engineering testing, specifically to a petroleum engineering testing device, and particularly to an assemblable liquid nitrogen fracturing wellbore. Background Technology

[0002] During liquid nitrogen fracturing, the cryogenic effect of liquid nitrogen causes a sharp drop in rock temperature at the main fracture surface, inducing shrinkage stress and forming a network of microfractures. Due to the deep burial of reservoirs during on-site construction, fracture propagation morphology is difficult to observe effectively, and on-site testing is costly. Therefore, equivalent analysis is often performed using indoor physical simulation experiments combined with CT scanning technology. In actual construction, the rapid vaporization of liquid nitrogen at the fracture tip can easily create high-pressure gas resistance, preventing effective injection of fracturing fluid. To address these issues, including the inability to inject fracturing fluid due to liquid nitrogen vaporization, this patent designs an assemblable liquid nitrogen fracturing wellbore that can effectively simulate liquid nitrogen fracturing using artificial indoor samples, solving the problem of inability to inject fracturing fluid due to liquid nitrogen vaporization and reducing testing costs. Summary of the Invention

[0003] To address the problem of fracturing fluid injection failure caused by liquid nitrogen vaporization, this invention provides an assemblable liquid nitrogen fracturing wellbore.

[0004] The novel wellbore comprises an outer wellbore, an inner wellbore, gaskets, and a base. The outer wellbore serves as a support and connection, connected to the liquid nitrogen injection pipe and the inner wellbore via threads. The cross-shaped pattern formed by the inserts at its upper end enhances wellbore stability. The inner wellbore guides the liquid nitrogen fracturing fluid, and the pores at its boundaries effectively expel the large amount of gas generated during the liquid nitrogen phase change. When the liquid nitrogen reaches the bottom of the wellbore, the vaporized liquid nitrogen pushes the gasket to the top of the wellbore, forming a unified structure with the cross-shaped pattern on the outer wellbore, thus creating a sealed fracturing environment. The base is threaded to the inner wellbore, preventing the gasket from slipping off during the initial injection phase. The outer wellbore, inner wellbore, gaskets, and base are interconnected to form a novel, assemblable liquid nitrogen fracturing wellbore.

[0005] The novel well casing device comprises: a main outer well casing 170mm long, with an inner diameter of 16mm and an outer diameter of 20mm, open at both the top and bottom. The upper part of the outer well casing contains a hollow cylinder 10mm long, with an inner diameter of 8mm and an outer diameter of 10mm. This hollow cylinder is integrated with the outer well casing by four 2mm thick arc-shaped inserts symmetrically distributed at 90° intervals. Both the upper and lower inner walls of the inner cylinder are threaded with a 4mm high thread. The inner well casing is 160mm long, with an inner diameter of 4mm and an outer diameter of 8mm. Its upper outer wall is threaded with a 4mm high thread, and its lower inner wall is threaded with a 3mm high thread. Both ends are open. The inner well casing has six layers of holes, each 3mm in diameter, starting 45mm from the top. The holes are evenly distributed at 60° intervals, with adjacent layers aligned and spaced 20mm apart. The base is 7mm long in total. Its upper outer wall has a 3mm long thread, an inner diameter of 3mm, and an outer diameter of 4mm. The lower end is 4mm long, has an inner diameter of 3mm, and an outer diameter of 10mm. The base has openings at both ends, the dimensions of which match the internal well shaft. The gasket has an inner diameter of 8mm, an outer diameter of 16mm, and a length of 2mm.

[0006] The beneficial effects achieved by this utility model are: it provides a fracturing tool for liquid nitrogen fracturing tests, effectively solving the problem of fracturing fluid not being able to be injected due to liquid nitrogen vaporization; at the same time, it has designed an assembly and disassembly system for the wellbore, making the equipment assembly and disassembly process simple, improving the efficiency of the test and reducing the test cost.

[0007] The new wellbore device

[0008] This invention is simple to install and easy to use, solving the problem of fracturing fluid injection failure caused by liquid nitrogen vaporization, improving fracturing fluid injection efficiency, and reducing testing costs. Furthermore, it facilitates sample assembly and disassembly after the test, effectively accelerating the testing process. The device is made of iron, a readily available material, ensuring testing accuracy and allowing for widespread application. Attached Figure Description

[0009] Other features, objectives, and advantages of this utility model will become more apparent upon reading the following accompanying drawings and detailed description:

[0010] Figure 1 This is a schematic diagram of an assemblable liquid nitrogen fracturing wellbore structure according to the present invention;

[0011] Figure 2 This is a cross-sectional view of the external wellbore structure of an assemblable liquid nitrogen fracturing wellbore according to the present invention;

[0012] Figure 3 This is a schematic diagram of the internal structure of an assemblable liquid nitrogen fracturing wellbore according to the present invention;

[0013] Figure 4 This is a schematic diagram of an assemblable liquid nitrogen fracturing wellbore base structure according to the present invention;

[0014] Figure 5 This is a schematic diagram of an assemblable liquid nitrogen fracturing wellbore gasket structure according to the present invention;

[0015] like Figure 1 As shown: (1) outer shaft, (2) inner shaft, (3) base, (4) gasket Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this utility model easier to understand, the present utility model will be further described below in conjunction with specific embodiments.

[0017] Please see Figure 1 This utility model provides a technical solution: an assemblable liquid nitrogen fracturing wellbore, including (1) an outer wellbore, (2) an inner wellbore, (3) a base, and (4) a gasket.

[0018] In this example, before the experiment, the outer wellbore (1) was inverted, and the inner wellbore (2) was connected to the outer wellbore (1) by the upper thread. The gasket (4) was placed between the outer wellbore (1) and the inner wellbore (2). The base (3) was then connected to the inner wellbore (2) by the upper thread, thus completing the assembly. In use, the assembled wellbore was first connected to the fracturing sample by high-strength glue. Then, the liquid nitrogen injection pipe was connected to the upper end of the outer wellbore (1) by the thread. During the experiment, liquid nitrogen entered the inner wellbore (2) through the upper end of the outer wellbore (1) and underwent a phase change reaction, generating a large amount of gas. The generated gas flowed into the gap between the outer wellbore (1) and the inner wellbore (2) through the holes on the surface of the inner wellbore (2) and continued to rise, and was discharged through the gap between the cross patterns at the top of the outer wellbore (1). When liquid nitrogen enters the open hole section of the wellbore (i.e., the space between the bottom of the wellbore and the bottom of the rock), the vaporized nitrogen will push the (4) gasket upwards until it reaches the top of the wellbore, thereby creating a sealed fracturing space between the wellbore and the rock sample. After the experiment, the wellbore is removed, and the (3) base, (4) gasket, (2) inner wellbore, and (1) outer wellbore are removed in sequence for use in the next experiment.

[0019] The basic principles, main features, and advantages of this utility model have been described above. For those skilled in the art, this utility model is not limited to the details in the above exemplary embodiments and can be embodied in other specific forms without departing from its features. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment has only one technical solution; the descriptive style of the specification is merely for ease of understanding.

[0020] Those skilled in the art should consider this specification as a whole, and the technical solutions in each implementation case can also be appropriately combined to form an implementation scheme that can be understood by everyone.

Claims

1. An assemblable liquid nitrogen fracturing wellbore, characterized in that: It consists of four parts: an outer wellbore, an inner wellbore, a gasket, and a base. The upper end of the outer wellbore has a cross-shaped insert to enhance its stability. The liquid nitrogen injection pipe is connected to the inner wellbore through the matching threads at the upper and lower ends of the hollow cylinder inside. The inner wellbore is used to guide the liquid nitrogen fracturing fluid, and the holes on its boundary can effectively remove the large amount of gas generated by the liquid nitrogen phase change. The base is connected to the inner wellbore through a matching thread to prevent the gasket from slipping off in the early stage of fluid injection. The size of the gasket matches the inner and outer wellbore to create a closed fracturing environment. The outer and inner wellbore are connected by threads. After the gasket is placed, it is connected to the base through the matching thread to form a complete wellbore.

2. The assemblable liquid nitrogen fracturing wellbore according to claim 1, characterized in that: The outer shaft, inner shaft, and base can be easily installed and removed using the threaded structure. The gasket shape and size are adapted to the inner and outer shafts and can be placed between them.

3. The assemblable liquid nitrogen fracturing wellbore according to claim 2, characterized in that: The outer well casing is 170mm long, with an inner diameter of 16mm and an outer diameter of 20mm. It is open at both the top and bottom. The upper end of the outer well casing has a hollow cylinder with a length of 10mm, an inner diameter of 8mm, and an outer diameter of 10mm. The hollow cylinder is integrated with the outer well casing by four arc-shaped inserts with a thickness of 2mm and symmetrically distributed at 90°. The inner walls at the top and bottom ends are threaded with a height of 4mm.

4. The assemblable liquid nitrogen fracturing wellbore according to claim 2, characterized in that: The internal well casing is 150mm long, with an inner diameter of 4mm and an outer diameter of 8mm. The upper outer wall has a thread height of 4mm, and the lower inner wall has a thread height of 3mm. Both ends are open.

5. The assemblable liquid nitrogen fracturing wellbore according to claim 3, characterized in that: The inner shaft has six layers of holes 45mm from the top. The holes are 3mm in diameter, and each layer has six holes. The holes are all the same size and shape, and are evenly distributed at 60°. The holes in adjacent layers are aligned, and each layer is 20mm apart.

6. The assemblable liquid nitrogen fracturing wellbore according to claim 2, characterized in that: The base is 7mm long in total. The upper outer wall has a thread length of 3mm, an inner diameter of 3mm, and an outer diameter of 4mm. The lower end is 4mm long, has an inner diameter of 3mm, and an outer diameter of 10mm. The base has openings at both the top and bottom, and the dimensions match the internal well shaft.

7. The assemblable liquid nitrogen fracturing wellbore according to claim 2, characterized in that: The gasket has an inner diameter of 8mm, an outer diameter of 16mm, and a length of 2mm, and is matched with the inner and outer well casings.

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