Hydraulic fracturing casing pipe for shale gas exploitation

Abstract

The invention relates to a hydraulic fracturing sleeve for shale gas exploitation, and belongs to the field of shale gas exploitation. Comprising a perforation and a sliding rail groove which are formed in a sleeve; the casing pipe comprises a first-stage casing pipe, a second-stage casing pipe and a third-stage casing pipe, the top of the inner wall of the third-stage casing pipe is provided with an electromagnetic converter and a wiring groove, a proppant containing iron particles is introduced into the third-stage casing pipe, and the electromagnetic converter is connected with a controller outside a drilling well through an electric wire located in the wiring groove; and the power of the electromagnetic converter is adjusted, so that the iron particles are suspended in the third-stage sleeve under the action of a magnetic field. A cover plate is welded on the wiring groove; a threaded mounting head is arranged at the top of the electromagnetic converter and is screwed into the concave hole of the third-stage sleeve for fixing; when the casing pipe is put down, a certain direction is maintained under the guiding effect of the sliding rail grooves of the casing pipes at all levels, torsion is avoided, the electromagnetic converter is located at the top of the casing pipe all the time, and the problem that propping agent particles are precipitated in fracturing fluid in the shale gas exploitation hydraulic fracturing process is solved.

Description

Technical Field

[0001] The present invention belongs to the field of shale gas exploitation and relates to a hydraulic fracturing casing for shale gas exploitation. Background Art

[0002] In the field of shale gas exploitation, the hydraulic fracturing technology is a crucial production enhancement measure. This technology injects high-pressure fracturing fluid into the shale formation to form a fracture network, thereby increasing the permeability and production of shale gas. However, during the hydraulic fracturing process, the precipitation problem of proppant particles in the fracturing fluid has become a technical problem that urgently needs to be solved.

[0003] Proppants play a crucial role in hydraulic fracturing. When the fracturing fluid is injected into the shale formation and fractures are formed, the sand-carrying fluid carrying the proppants then enters the fractures, and the proppant particles are deposited in the fractures to prevent the fractures from closing again after the pressure is released, thereby maintaining the conductivity of the fractures. However, proppant particles are extremely prone to precipitation in the fracturing fluid, mainly due to the following factors:

[0004] (1) Density difference between proppant and fracturing fluid: The density of proppant particles is usually significantly higher than that of the fracturing fluid. Under the action of gravity, the particles tend to settle downward.

[0005] (2) Insufficient viscosity of the fracturing fluid: According to Stokes' formula, the particle settlement velocity is proportional to the density difference and inversely proportional to the fluid viscosity. When the viscosity of the fracturing fluid is insufficient, the settlement velocity increases; at high temperatures or high shear rates, some fracturing fluids may undergo viscosity degradation, further reducing the suspension ability.

[0006] (3) Low flow velocity conditions inside the casing: When the inner diameter of the casing is large, the flow velocity will decrease at the same displacement; if the flow velocity of the fracturing fluid is too low (laminar flow state), the fluid carrying capacity will decrease; according to the critical suspension velocity formula, when the flow velocity is lower than the critical value, the particles cannot be effectively carried.

[0007] (4) Influence of proppant particle size and shape: The larger the proppant particle size, the faster the settlement velocity (Stokes velocity is proportional to the square of the particle size); irregularly shaped proppants may affect their buoyancy due to changes in the drag coefficient.

[0008] (5) Others: Such as improper control of construction parameters, multiphase flow effects, local effects of the casing geometry, etc., are also extremely prone to local particle accumulation and other situations.

[0009] In existing shale gas extraction technologies, although various types of proppants have been developed, such as quartz sand, ceramic proppants, resin-coated sand, etc., there are still problems with proppant particles settling in the fracturing fluid during actual applications. The settlement of proppants in the casing may block the casing or perforation holes, affecting the injection of the fracturing fluid. It may also lead to uneven distribution of proppants in the formation fractures, reducing the conductivity, and resulting in poor filling effect, affecting the fracturing and fracture creation effect. Even worse, it may cause the failure of the fracturing operation and an increase in costs.

[0010] Therefore, in view of the problem of proppant particles settling in the fracturing fluid during the hydraulic fracturing process of shale gas extraction, developing a new type of proppant and its preparation method to improve the dispersibility and stability of proppants in the fracturing fluid and reduce sedimentation is of great significance for improving the efficiency and economy of shale gas extraction. Summary of the Invention

[0011] In view of this, the purpose of the present invention is to provide a hydraulic fracturing casing for shale gas extraction to solve the problem of proppant particles settling in the fracturing fluid during the hydraulic fracturing process of shale gas extraction.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A hydraulic fracturing casing for shale gas extraction, the casing is provided with perforations and a slide rail groove for guiding, the slide rail groove is arranged along the axial direction of the casing and recesses towards the inside of the casing;

[0014] The casing includes a first-stage casing, a second-stage casing, and a third-stage casing sleeved in sequence, and the slide rail grooves that match each other are provided on each stage of the casing; the casing includes a vertical section in the vertical well and a horizontal section in the horizontal well, and the perforations and slide rail grooves are both arranged on the horizontal section;

[0015] The third-stage casing is located in the innermost layer, and an electromagnetic converter is provided on the top of the inner wall of the third-stage casing in the horizontal section; a proppant containing iron particles is injected into the third-stage casing, and the magnetic field strength is adjusted by controlling the power of the electromagnetic converter, so that the iron-containing particles are suspended in the third-stage casing to prevent sedimentation.

[0016] Optionally, a wire groove recessed towards the inside is provided on the inner wall of the third-stage casing on the side close to the electromagnetic converter, the wire groove is arranged along the axial direction of the third-stage casing and extends to the ground wellhead; a wire connected to the electromagnetic converter is provided in the wire groove, and the wire extends to the ground wellhead and is connected to a controller outside the drilling rig, and the power of the electromagnetic converter is controlled through the controller and the wire.

[0017] Optionally, a cover plate is provided on the wire groove.

[0018] Optionally, the cover plate is welded to the wire groove, so that the surface of the three-stage casing fits against the inner wall of the two-stage casing.

[0019] Optionally, the three-stage casing located in the horizontal section includes a perforation section and an electromagnetic section arranged at intervals. The electromagnetic converter is only arranged in the electromagnetic section, and the perforation is only arranged in the perforation section; the perforation section and the electromagnetic section are welded and connected to each other.

[0020] Optionally, a concave hole is formed at the top of the electromagnetic section. An installation head is provided on the electromagnetic converter. Threads are provided on the surface of the installation head. The installation head is screwed into the concave hole and welded to fix the electromagnetic converter at the top of the electromagnetic section.

[0021] Optionally, one end of the electromagnetic converter close to the inner wall of the three-stage casing is arc-shaped and fits against the inner surface of the three-stage casing.

[0022] Optionally, a channel is formed in the installation head for the wire to pass through.

[0023] Optionally, the channel is located on the central axis of the installation head.

[0024] Optionally, an anticorrosive material is wound around the outside of the casing.

[0025] The beneficial effects of the present invention are as follows:

[0026] According to the principle of electromagnetic induction of the present invention, during drilling and well completion, an electromagnetic converter is arranged at the top of the casing, and a proppant containing iron is used during fracturing. During hydraulic fracturing, the electromagnet is activated by power on, the electromagnetic converter generates a magnetic field, and the proppant containing iron particles generates a vertically upward attraction force under the action of the magnetic field, suspending in the fracturing fluid, avoiding the phenomenon of sinking to the bottom, and improving the fracturing efficiency.

[0027] Among them, by setting the recessed slide rail groove, it plays a guiding role for the lower part of each stage of the casing, avoiding the twisting phenomenon during the lowering process, so as to ensure that the electromagnetic converter arranged in the casing is always located at the top of the casing, thereby realizing the upward attraction force on the proppant containing iron particles under the action of the magnetic field and avoiding the sinking of the proppant particles to the bottom.

[0028] The present invention has a low manufacturing threshold, good economy, mature electromagnetic converter technology, can effectively solve the problem of proppant sinking to the bottom, reduce the viscosity of the fracturing fluid, reduce the fracturing resistance, and improve the fracturing efficiency. At the same time, the usage amount of additives such as thickeners of the fracturing fluid is reduced, and the construction is more environmentally friendly. The power is on during fracturing and off during gas production. If secondary fracturing is carried out, the electromagnetic converter can still be recycled, meeting the requirements of continuous and efficient deep shale hydraulic fracturing and adapting to large-scale popularization and application.

[0029] Other advantages, objects, and features of the present invention will be set forth in part in the following description, and in part will be obvious to those skilled in the art upon examination of the following, or may be learned by practice of the present invention. The objects and other advantages of the present invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out hereinafter. Brief Description of the Drawings

[0030] In order to make the objects, technical solutions, and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, where:

[0031] Figure 1 is an overall schematic diagram of the casing of the present invention;

[0032] Figure 2 is a schematic assembly diagram of the casing;

[0033] Figure 3 is a schematic cross-sectional view of the perforation section of the three-stage casing;

[0034] Figure 4 is a schematic cross-sectional view of the electromagnetic section of the three-stage casing;

[0035] Figure 5 is an enlarged schematic view of the electromagnetic converter;

[0036] Figure 6 is an enlarged schematic view of the mounting head of the electromagnetic converter;

[0037] Figure 7 is a schematic cross-sectional connection view of the perforation section and the electromagnetic section of the three-stage casing;

[0038] Figure 8 is a front view of the connection of the perforation section and the electromagnetic section of the three-stage casing;

[0039] Figure 9 is a top view of the connection of the perforation section and the electromagnetic section of the three-stage casing;

[0040] Figure 10 is for Figure 1 overall perspective view;

[0041] Figure 11 is a schematic diagram of the cross-section and surface morphology of the proppant in the fracture.

[0042] Reference Signs:

[0043] 1 primary casing, 2 secondary casing, 3 tertiary casing, 4 perforation section, 5 electromagnetic section, 6 perforation, 7 slide rail groove, 8 wire routing groove, 9 electromagnetic converter, 10 wire, 11 controller, 12 mounting head, 13 thread, 14 channel. Detailed Description of the Preferred Embodiments

[0044] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0045] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0046] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0047] Please refer to Figures 1 to 11 , which is a hydraulic fracturing casing for shale gas extraction. The casing is provided with perforations 6 and a slide rail groove 7 for guiding. The slide rail groove 7 is arranged along the axial direction of the casing and recesses towards the inside of the casing; the casing includes a first-stage casing 1, a second-stage casing 2, and a third-stage casing 3 that are sleeved in sequence, and the slide rail grooves 7 that match each other are provided on each stage of the casing; the casing includes a vertical section in the vertical well and a horizontal section in the horizontal well, and the perforations 6 and the slide rail groove 7 are both arranged in the horizontal section; the third-stage casing 3 is located in the innermost layer, and an electromagnetic converter 9 is provided on the top of the inner wall of the third-stage casing 3 in the horizontal section; a proppant containing iron particles is injected into the third-stage casing 3, and the magnetic field strength is adjusted by controlling the power of the electromagnetic converter 9, so that the iron particles are suspended in the third-stage casing 3 to prevent the phenomenon of sinking to the bottom. When lowering the casing, each stage of the casing slides along the slide rail groove 7 without torsion and maintains a certain direction to ensure that the electromagnetic converter 9 is always above the casing.

[0048] In some embodiments of the present invention, a plurality of slide rail grooves 7 are uniformly arranged along the axial direction of the casing, preferably 4.

[0049] On one inner wall side of the third-stage casing 3 close to the electromagnetic converter 9, there is a wire groove 8 recessed towards the inside. The wire groove 8 is arranged along the axial direction of the third-stage casing 3 and extends to the ground wellhead; a wire 10 connected to the electromagnetic converter 9 is provided in the wire groove 8. After the wire 10 extends to the ground wellhead, it is connected to a controller 11 outside the drilling. The power adjustment of the electromagnetic converter 9 is controlled through the controller 11 and the wire 10.

[0050] A cover plate is welded on the wire groove 8 and anti-corrosion treatment is carried out, making the outer surface of the casing flat and undamaged, making the surface of the third-stage casing 3 fit with the inner wall of the second-stage casing 2, and playing a role in sealing and protecting the wire 10 inside the wire groove 8.

[0051] To prevent conflicts between the perforation 6 and the installation position of the electromagnetic converter 9, the third-stage casing 3 in the horizontal section is divided into a perforation section 4 and an electromagnetic section 5 arranged at intervals; the electromagnetic converter 9 is only arranged in the electromagnetic section 5, and the perforation 6 is only arranged in the perforation section 4. The perforation 6 and the electromagnetic converter 9 are installed separately; the perforation section 4 and the electromagnetic section 5 are alternately lowered into the drilling, and welding and anti-corrosion treatment are carried out at the connection; the perforation 6 needs to be made on the pipe wall of the perforation section 4 by a perforator after the perforation section 4 is lowered into the drilling.

[0052] A concave hole is opened at the top of the electromagnetic section 5. The electromagnetic converter 9 is provided with a mounting head 12. Threads 13 are provided on the surface of the mounting head 12. The mounting head 12 is screwed into the concave hole and welded to fix the electromagnetic converter 9 at the top of the electromagnetic section 5. One end of the electromagnetic converter 9 close to the inner wall of the third-stage casing 3 is arc-shaped and fits with the inner surface of the third-stage casing 3. A channel 14 is opened on the mounting head 12 for the wire 10 to pass through. One end of the channel 14 leads to the electromagnetic converter 9, and the other end can be arranged at the top of the central axis of the mounting head 12 or opened on the upper side wall of the mounting head 12. During installation, the installation is carried out from the inside of the casing. After the mounting head 12 is screwed into the concave hole, the wire 10 is connected, and finally, laser welding processing is carried out on the mounting head 12 and the concave hole part to increase the strength of the component and improve the sealing effect.

[0053] Before the casing is lowered, an anti-corrosion material is wound around its outside for thermal anti-corrosion treatment to extend the service life of the casing.

[0054] All levels of casing pipes are prefabricated in the factory, including the opening of concave holes, the prefabrication of wire grooves 8, slide rail grooves 7 and the laying and fixing of wires 10. The cover plates of the wire grooves 8 are welded, and the electromagnetic converters 9 are installed. After transporting the third-level casing pipe 3, the first-level casing pipe 1 and the second-level casing pipe 2 with the electromagnetic converters 9 installed to the construction site, the casing pipes are lowered step by step; when connecting and lowering the third-level casing pipe 3, only the joints of the wires 10 between the casing pipes need to be connected, and the fixing, insulation and anti-corrosion treatments are done, then the installation work of the wires 10 can be completed, and then the casing pipe welding and anti-corrosion work can be carried out; the perforation section 4 and the electromagnetic section 5 are alternately lowered into the wellbore, and the joints are welded and anti-corrosion treated. After the third-level casing pipe 3 is lowered completely, a perforator is used to open perforations 6 in the casing pipe of the perforation section 4.

[0055] Before the casing pipes of all levels of the present invention are lowered, they are prefabricated and installed in the factory, which reduces the workload at the construction site as much as possible, can improve the construction efficiency, and save the time cost and labor cost of on-site construction.

[0056] Using the hydraulic fracturing casing pipe for shale gas extraction of the present invention to realize the method for preventing proppant particles from settling includes the following steps:

[0057] S1, fabricate proppants containing iron powder particles;

[0058] S11, prepare raw materials: kaolin particles, iron powder particles, pore-forming agents;

[0059] In some embodiments of the present invention, the pore-forming agent uses dolomite particles. Dolomite is oxidized and decomposed at high temperature, forming pores inside the ceramic, increasing the porosity of the ceramic, and thus generating a certain buoyancy.

[0060] S12, dry the raw material particles, add 1.5% inorganic reinforcing agent and grind and mix evenly; then add the binder solution and mix evenly, then introduce it into the mold and compact it; the pressure of the compacted mold is 100 MPa, and the pressure holding time is 2 minutes;

[0061] In some embodiments of the present invention, the binder uses a 5% polyvinyl alcohol solution.

[0062] S13, demold the sample to obtain a green blank;

[0063] S14, put the sample green blank into a high-temperature furnace for sintering, the sintering temperature is 1150 °C, the heat preservation time is 120 min, and it is cooled with the furnace;

[0064] S15, put the sintered material into a crusher for crushing, then put the fragments into a ball mill to round them, and prepare porous ferromagnetic proppant particles with corresponding particle sizes according to the required size.

[0065] S2, inject the proppant into the casing with the electromagnetic converter 9 installed at the top. The electromagnetic converter 9 is electrically connected to the controller 11 outside the drilling well. Adjust the power of the electromagnetic converter 9 through the controller 11 to make the iron particles contained in the proppant suspended in the tertiary casing 3 and prevent the phenomenon of sinking to the bottom.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A shale gas exploitation hydraulic fracturing casing, characterized by: The casing is provided with perforations (6) and a guide rail groove (7), wherein the guide rail groove (7) is arranged along the axial direction of the casing and is recessed toward the inside of the casing; The casing comprises a primary casing (1), a secondary casing (2) and a tertiary casing (3) which are sequentially sleeved, and each level of the casing is provided with the slide rail grooves (7) which match each other; the casing comprises a vertical section located in a vertical well and a horizontal section located in a horizontal well, and the perforations (6) and the slide rail grooves (7) are both provided in the horizontal section; The tertiary casing (3) is located in the innermost layer, and an electromagnetic converter (9) is provided on the top of the inner wall of the tertiary casing (3) in the horizontal section; a proppant containing iron particles is injected into the tertiary casing (3), and the magnetic field strength is adjusted by controlling the power of the electromagnetic converter (9), so that the iron particles are suspended in the tertiary casing (3) to prevent sinking to the bottom.

2. The shale gas extraction hydraulic fracturing casing according to claim 1, characterized in that: A wiring groove (8) recessed inwardly is provided on the inner wall of one side of the tertiary casing (3) close to the electromagnetic converter (9); the wiring groove (8) is arranged along the axial direction of the tertiary casing (3) and extends to the surface wellhead; an electric wire (10) connected to the electromagnetic converter (9) is arranged in the wiring groove (8); after the electric wire (10) extends to the surface wellhead, it is connected to a controller (11) outside the drilling well; the power adjustment of the electromagnetic converter (9) is controlled by the controller (11) and the electric wire (10).

3. The shale gas extraction hydraulic fracturing casing according to claim 2, characterized in that: A cover plate is provided on the wiring groove (8).

4. The shale gas extraction hydraulic fracturing casing according to claim 3, characterized in that: The cover plate is welded on the wiring groove (8) so that the surface of the tertiary casing (3) fits the inner wall of the secondary casing (2).

5. The shale gas extraction hydraulic fracturing casing according to claim 2, characterized in that: The tertiary casing (3) located in the horizontal section comprises a perforation section (4) and an electromagnetic section (5) which are arranged at intervals, the electromagnetic converter (9) is only arranged in the electromagnetic section (5), and the perforations (6) are only arranged in the perforation section (4); the perforation section (4) and the electromagnetic section (5) are welded to each other.

6. The shale gas extraction hydraulic fracturing casing according to claim 5, characterized in that: The electromagnetic section (5) has a concave hole at the top, the electromagnetic converter (9) has a mounting head (12), a surface of the mounting head (12) has a thread (13), and the mounting head (12) is screwed into the concave hole and welded to fix the electromagnetic converter (9) to the top of the electromagnetic section (5).

7. The shale gas extraction hydraulic fracturing casing according to claim 6, characterized in that: The installation head (12) is provided with a channel (14) for the electric wire (10) to pass through.

8. The shale gas extraction hydraulic fracturing casing according to claim 7, characterized in that: The channel (14) is located on the central axis of the mounting head (12).

9. The shale gas extraction hydraulic fracturing casing according to claim 1, characterized in that: One end of the electromagnetic converter (9) close to the inner wall of the tertiary casing (3) is arc-shaped and fits closely with the inner surface of the tertiary casing (3).

10. The shale gas extraction hydraulic fracturing casing according to claim 1, characterized in that: The sleeve is externally wound with anti-corrosion material.

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