Anti-precipitation method for hydraulic fracturing propping agent in shale gas exploitation

Abstract

The invention relates to an anti-precipitation method for a hydraulic fracturing propping agent for shale gas exploitation, and belongs to the technical field of shale gas exploitation. Comprising the following steps: S1, preparing a proppant containing iron powder particles: preparing raw materials, drying the raw material particles, adding an inorganic reinforcing agent and an adhesive solution, grinding, uniformly mixing, introducing into a mold, compacting, demolding, sintering at high temperature, cooling along with a furnace, crushing and rounding to prepare porous ferromagnetic proppant particles; and S2, the propping agent is injected into the sleeve with the electromagnet function. And the top of the sleeve is provided with an electromagnetic converter, so that the iron powder particles are suspended in the sleeve under the action of a magnetic field. Dolomite particles are used as a pore-forming agent and are oxidized and decomposed at high temperature to form pores, so that the porosity of the ceramic is improved and buoyancy is generated. According to the invention, the problem of precipitation of proppant particles in the fracturing fluid in the shale gas exploitation hydraulic fracturing process is solved through buoyancy generated by pores formed after high-temperature oxidation of the dolomite particles and suspension of the iron powder particles under the action of a magnetic field.

Description

Technical Field

[0001] The present invention belongs to the technical field of shale gas exploitation, and relates to a method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation. Background Art

[0002] In the field of shale gas exploitation, the hydraulic fracturing technology is a crucial production-increasing 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 sedimentation 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, the proppant particles are extremely prone to sedimentation 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 fracturing fluid: According to Stokes' law, 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, the viscosity of some fracturing fluids may degrade, further reducing the suspension ability.

[0006] (3) Low flow velocity condition in 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 flow 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 the existing shale gas extraction technologies, although various types of proppants have been developed, such as quartz sand, ceramsite, resin-coated sand, etc., there are still problems with the precipitation of proppant particles in the fracturing fluid during actual application. 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 seam 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 particle precipitation in the fracturing fluid encountered 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 precipitation 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 method for preventing precipitation of hydraulic fracturing proppants in shale gas extraction, which solves the problem of proppant particle precipitation in the fracturing fluid encountered 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 method for preventing precipitation of hydraulic fracturing proppants in shale gas extraction, comprising the following steps:

[0014] S1, producing proppants containing iron powder particles;

[0015] S2, injecting the proppants into the casing with the function of an electromagnet;

[0016] Wherein an electromagnetic converter is provided on the top inner wall of the casing in the horizontal section of the wellbore, and the electromagnetic converter is electrically connected to a controller outside the wellbore. The power of the electromagnetic converter is adjusted through the controller to make the iron-containing particles in the proppants suspended in the casing, preventing the phenomenon of sinking to the bottom.

[0017] Optionally, step S1 includes the following steps:

[0018] S11, preparing raw materials: kaolin particles, iron powder particles, pore-forming agent;

[0019] S12, drying the raw material particles, adding 1.5% inorganic reinforcing agent and grinding and mixing evenly; then adding a binder solution and mixing evenly, and introducing it into a mold and compacting;

[0020] S13, demolding the sample to obtain a green blank;

[0021] S14. Place the green sample into a high-temperature furnace for sintering at 1150 °C for 120 minutes, then cool it in the furnace.

[0022] S15. Place the sintered material into a crusher for crushing, and then put the fragments into a ball mill to round them. According to the required size, prepare porous ferromagnetic proppant particles with corresponding particle sizes.

[0023] Optionally, in step S12, the die pressure for compaction treatment is 100 MPa, and the pressure holding time is 2 minutes.

[0024] Optionally, the pore-forming agent is dolomite particles.

[0025] Optionally, the binder is a 5% polyvinyl alcohol solution.

[0026] Optionally, before injecting the proppant into the casing, lower the casing into the well first; the casing in the horizontal section includes spaced-apart perforation sections and electromagnetic sections, and the electromagnetic converter is only arranged in the electromagnetic section; the perforation sections and electromagnetic sections are alternately lowered into the well, and welding and anti-corrosion treatment are carried out at the connection; after the perforation section is lowered into the well, use a perforator to make the perforations on the wall of the perforation section.

[0027] Optionally, a concave hole is provided 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, and the installation head is screwed into the concave hole and welded to ensure tightness and no damage, so as to fix the electromagnetic converter at the top of the electromagnetic section.

[0028] Optionally, a wire groove recessed towards the inside of the casing is provided at the top of the casing wall, and the wire groove communicates from the installation location of the electromagnetic converter to the outside of the well along the radial direction of the casing. Wires connecting the electromagnetic converter and the controller are placed in the wire groove.

[0029] Optionally, after the electromagnetic converter and the wires are connected and installed, cover the wire groove with a cover plate and carry out welding and anti-corrosion treatment to make the outer surface of the casing flat and without damage.

[0030] Optionally, the casing includes a first-stage casing, a second-stage casing, and a third-stage casing sleeved in sequence, and the electromagnetic converter is installed on the inner wall of the innermost third-stage casing; sliding rail grooves that match each other are provided on each stage of the casing; the sliding rail grooves are arranged along the axial direction of the casing and recess into the casing, and the casing is lowered layer by layer, and the mutually matching sliding rail grooves play a guiding role for the casing to prevent the casing from twisting.

[0031] The beneficial effects of the present invention are as follows:

[0032] Dolomite undergoes thermal oxidative decomposition at high temperatures to produce CO2, forming pores inside the ceramic, increasing the porosity of the ceramic, and thus generating a certain buoyancy. The chemical reaction is as follows:

[0033]

[0034] The present invention utilizes this principle and combines it with the main component of the proppant, kaolin. After calcination, kaolinite mainly generates components such as mullite and aluminosilicate spinel. Dolomite particles are used as pore formers to generate a certain buoyancy, and inorganic strengtheners are used to enhance the strength of ceramic particles. Then, a small amount of iron powder is added to the proppant particles to make the proppant particles have a certain ferromagnetism and also have strong mechanical properties. Then, based on the principle of electromagnetic induction, during the drilling and completion stages, a casing with an electromagnet function is used. During hydraulic fracturing, the electromagnet is activated by electricity, and the porous ferromagnetic proppant generates an upward vertical attraction under the action of the magnetic field. Under the action of buoyancy and magnetic suction, the porous ferromagnetic proppant particles are suspended in the fracturing fluid, avoiding precipitation and improving the fracturing efficiency. At the same time, to achieve the particle suspension effect, while increasing the porosity of the proppant particles, the compressive strength and proppant performance of the particles are reduced, thus meeting the continuous and efficient requirements for deep shale gas exploitation fracturing. The ferromagnetic proppant of the present invention has a low manufacturing threshold, good economy, low relative density, and high strength, and is suitable for large-scale popularization and application.

[0035] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0037] Figure 1 is the flowchart of the method steps of the present invention;

[0038] Figure 2 is the overall perspective view of the present invention;

[0039] Figure 3 is the schematic diagram of the cross-section and surface morphology of the proppant in the fracture;

[0040] Figure 4 is the overall schematic diagram of the casing;

[0041] Figure 5 is the schematic diagram of the casing assembly;

[0042] Figure 6It is a schematic cross-sectional view of the perforation section of the three-stage casing;

[0043] Figure 7 It is a schematic cross-sectional view of the electromagnetic section of the three-stage casing;

[0044] Figure 8 It is an enlarged schematic view of the electromagnetic converter;

[0045] Figure 9 It is an enlarged schematic view of the mounting head of the electromagnetic converter;

[0046] Figure 10 It is a schematic cross-sectional view of the connection between the perforation section and the electromagnetic section of the three-stage casing;

[0047] Figure 11 It is a front view of the connection between the perforation section and the electromagnetic section of the three-stage casing;

[0048] Figure 12 It is a top view of the connection between the perforation section and the electromagnetic section of the three-stage casing.

[0049] Reference numerals:

[0050] 1 First-stage casing, 2 Second-stage casing, 3 Third-stage casing, 4 Perforation section, 5 Electromagnetic section, 6 Perforation, 7 Slide rail groove, 8 Wiring groove, 9 Electromagnetic converter, 10 Electric wire, 11 Controller, 12 Mounting head, 13 Thread, 14 Channel. Specific implementation mode

[0051] The following uses specific specific examples to illustrate the implementation mode of the present invention. Those skilled in the art can easily understand 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 implementation modes. The 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 diagrams 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.

[0052] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to 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.

[0053] 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, they are based on the orientation or positional relationship shown in the drawings. This 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 limiting 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.

[0054] Please refer to Figures 1 to 12 , a method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation, comprising the following steps:

[0055] S1, producing proppants containing iron powder particles;

[0056] S2, injecting the proppants into a casing with an electromagnet function;

[0057] An electromagnetic converter 9 is provided on the top of the inner wall of the casing in the horizontal section of the wellbore. The electromagnetic converter 9 is electrically connected to a controller 11 outside the wellbore. The power of the electromagnetic converter 9 is adjusted through the controller 11 to make the iron-containing particles in the proppants suspended in the tertiary casing 3, preventing the occurrence of sedimentation at the bottom.

[0058] Step S1 includes the following steps:

[0059] S11, preparing raw materials: kaolin particles, iron powder particles, pore-forming agents;

[0060] In some embodiments of the present invention, the pore-forming agent uses dolomite particles.

[0061] S12, drying the raw material particles, adding 1.5% inorganic reinforcing agent and grinding and mixing evenly; then adding a binder solution and mixing evenly, and introducing it into a mold and compacting it. The mold pressure for compacting is 100 MPa, and the pressure holding time is 2 minutes;

[0062] In some embodiments of the present invention, the binder uses a 5% polyvinyl alcohol solution.

[0063] S13, demolding the sample to obtain a green blank;

[0064] S14, putting 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;

[0065] S15. Put the sintered material into a crusher for crushing, and then put the fragments into a ball mill to round them. According to the required size, porous ferromagnetic proppant particles with corresponding particle sizes are produced.

[0066] Before injecting proppant into the casing, lower the casing into the wellbore first. To prevent conflicts at the installation position of the electromagnetic converter 9 in the perforation 6, the casing in the horizontal section is divided into perforation sections 4 and electromagnetic sections 5 arranged at intervals. The electromagnetic converter 9 is only arranged in the electromagnetic section 5. The perforation sections 4 and electromagnetic sections 5 are alternately lowered into the wellbore, and welding and anti-corrosion treatment are carried out at the connection. After the perforation section 4 is lowered into the wellbore, a perforator is used to open perforations 6 on the pipe wall of the perforation section 4.

[0067] 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 the inner surface of the third-stage casing 3. A channel 14 is opened on the mounting head 12 for the power supply 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, install from the inside of the casing. After screwing the mounting head 12 into the concave hole, connect the wire 10, and finally perform laser welding on the mounting head 12 and the concave hole part to ensure density and no damage, increase the strength of the component, and improve the sealing effect.

[0068] A wire groove 8 recessed towards the inside of the casing is provided at the top of the casing wall. The wire groove 8 communicates from the installation position of the electromagnetic converter 9 along the radial direction of the casing to the outside of the wellbore. The wire 10 connecting the electromagnetic converter 9 and the controller 11 is placed in the wire groove 8, and the power adjustment of the electromagnetic converter 9 is controlled through the controller 11 and the wire 10.

[0069] After the electromagnetic converter 9 and the wire 10 are connected and installed, cover the wire groove 8 with a cover plate and perform welding and anti-corrosion treatment to make the outer surface of the casing flat and without damage, make the surface of the third-stage casing 3 fit the inner wall of the second-stage casing 2, and play a role in sealing and protecting the wire 10 inside the wire groove 8.

[0070] The casing includes a first-stage casing 1, a second-stage casing 2, and a third-stage casing 3 sleeved in sequence. The electromagnetic converter 9 is installed on the inner wall of the innermost third-stage casing 3. Matching slide rail grooves 7 are provided on each stage of the casing. The slide rail grooves 7 are arranged along the axial direction of the casing and recess into the casing. The casing is lowered layer by layer, and the matching slide rail grooves 7 play a guiding role for the casing to prevent the casing from twisting.

[0071] 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.

[0072] All levels of casing pipes are prefabricated in the factory, including opening concave holes, prefabricating wire routing grooves 8, slide rail grooves 7 and laying and fixing electric wires 10, welding the cover plates of the wire routing grooves 8, and installing the electromagnetic converters 9. 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 electric wires 10 between the casing pipes need to be connected, and fixing, insulation, and anti-corrosion treatments are carried out to complete the installation work of the electric wires 10. Subsequently, 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 drilling well, and welding and anti-corrosion treatments are carried out at the joints. 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.

[0073] Before the casing pipes of all levels of the present invention are lowered, prefabrication and installation are carried out in the factory, which reduces the workload at the construction site as much as possible, improves the construction efficiency, and saves the time cost and labor cost of on-site construction.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended 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 spirit and scope of the technical solutions, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation, characterized in that: It includes the following steps: S1, fabricate proppants containing iron powder particles; S2, inject the proppants into a casing with electromagnetic function; Wherein, an electromagnetic converter (9) is provided on the top of the inner wall of the casing in the horizontal section of the wellbore, and the electromagnetic converter (9) is electrically connected to a controller (11) outside the wellbore. The power of the electromagnetic converter (9) is adjusted through the controller (11) to make the iron-containing particles in the proppants suspended in the casing, preventing the phenomenon of sinking to the bottom.

2. The method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation according to claim 1, characterized in that: Step S1 includes the following steps: S11, prepare raw materials: kaolin particles, iron powder particles, pore-forming agent; S12, dry the raw material particles, add 1.5% inorganic reinforcing agent and grind and mix evenly; then add a binder solution and mix evenly, then introduce it into a mold and compact it; S13, demold the sample to obtain a green blank; 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; S15, put the sintered material into a crusher for crushing, and then put the fragments into a ball mill to round them, and make porous ferromagnetic proppant particles with corresponding particle sizes according to the required size.

3. The method for preventing precipitation of hydraulic fracturing proppants in shale gas exploitation according to claim 2, wherein: In step S12, the pressure of the mold for compaction treatment is 100 MPa, and the pressure holding time is 2 minutes.

4. The method for preventing precipitation of hydraulic fracturing proppants in shale gas exploitation according to claim 2, wherein: The pore-forming agent is dolomite particles.

5. The method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation according to claim 2, wherein: The binder is a 5% polyvinyl alcohol solution.

6. The method for preventing precipitation of hydraulic fracturing proppants in shale gas extraction according to claim 1, wherein: Before injecting the proppants into the casing, first lower the casing into the wellbore; the casing in the horizontal section includes spaced perforation sections (4) and electromagnetic sections (5), and the electromagnetic converter (9) is only provided in the electromagnetic section (5); the perforation sections (4) and electromagnetic sections (5) are alternately lowered into the wellbore, and welding and anti-corrosion treatment are carried out at the joints; after the perforation section (4) is lowered into the wellbore, a perforator is used to open the perforations (6) on the pipe wall of the perforation section (4).

7. The method for preventing precipitation of hydraulic fracturing proppants in shale gas exploitation according to claim 6, characterized in that: A concave hole is provided at the top of the electromagnetic section (5), an installation head (12) is provided on the electromagnetic converter (9), a thread (13) is provided on the surface of the installation head (12), and the installation head (12) is screwed into the concave hole and welded to fix the electromagnetic converter (9) on the top of the electromagnetic section (5).

8. The method for preventing precipitation of hydraulic fracturing proppants in shale gas exploitation according to claim 1, characterized in that: A wire groove (8) recessed towards the inside of the casing is provided at the top of the casing pipe wall, and the wire groove (8) communicates from the installation place of the electromagnetic converter (9) along the radial direction of the casing to the outside of the wellbore, and a wire (10) connecting the electromagnetic converter (9) and the controller (11) is placed in the wire groove (8).

9. The method for preventing precipitation of hydraulic fracturing proppants in shale gas exploitation according to claim 8, wherein: After the electromagnetic converter (9) and the wire (10) are connected and installed, a cover plate is covered on the wire groove (8), and welding and anti-corrosion treatment are carried out to make the outer surface of the casing flat and intact.

10. The method for preventing sedimentation of hydraulic fracturing proppants in shale gas exploitation according to claim 1, wherein: The casing includes a first-stage casing (1), a second-stage casing (2), and a third-stage casing (3) that are sleeved in sequence. The electromagnetic converter (9) is installed on the inner wall of the innermost third-stage casing (3). Matching slide rail grooves (7) are provided on each stage of the casing. The slide rail grooves (7) are arranged along the axial direction of the casing and recess into the casing. As the casing is lowered layer by layer, the mutually matching slide rail grooves (7) play a guiding role for the casing to prevent the casing from twisting.

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