Ceramsite proppant for exploiting shale gas as well as preparation method and application of ceramsite proppant

Abstract

The invention relates to the technical field of shale gas exploitation, in particular to a ceramsite proppant for shale gas exploitation and a preparation method and application of the ceramsite proppant. The ceramsite proppant disclosed by the invention is prepared from the following raw materials in parts by weight: 1 to 22 parts of oil-based rock debris, 4 to 18 parts of potassium feldspar powder and 66 to 95 parts of low-grade bauxite. Wherein the mass percent of Al2O3 in the low-grade bauxite is 45 wt%-50 wt%. The preparation process comprises the following steps: heating and grinding oil-based rock debris at the temperature of 300-350 DEG C to obtain rock debris tailings with the oil content of less than 1%; sequentially calcining, crushing and sieving the rock debris tailings to obtain rock debris fine powder; mixing the rock debris fine powder with potassium feldspar powder and low-grade bauxite to obtain mixed raw material powder; granulating the mixed raw material powder by using water as a balling medium to obtain green pellets; sintering the green pellets to obtain sintered ceramsite; and sieving the sintered ceramsite to obtain the ceramsite proppant. The ceramsite proppant has the effect of recycling the low-grade bauxite so as to reduce the manufacturing cost of the ceramsite proppant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shale gas exploitation, and particularly relates to a ceramic proppant for shale gas exploitation and a preparation method and application thereof. BACKGROUND

[0002] In the process of shale gas exploitation, a large amount of oil-based rock debris is generated, which not only pollutes the environment, but also further affects the health of animals and plants and human beings. Therefore, it is urgent to effectively dispose the oil-based rock debris. The best disposal method is to use the oil-based rock debris as raw material to manufacture products for shale gas exploitation operation.

[0003] Using the oil-based rock debris as raw material to manufacture the proppant to achieve the purpose of supporting the reservoir cracks and improving the gas production rate becomes a feasible resource utilization outlet of the oil-based rock debris. In the preparation process of the conventional ceramic proppant, bauxite with high alumina content is usually added. However, the high-quality bauxite with high alumina content has a high cost, and the reserves of the bauxite with high alumina content are also decreasing. Therefore, it is necessary to develop a ceramic proppant which meets the economic efficiency and related performance indicators. SUMMARY

[0004] The present application discloses a ceramic proppant for shale gas exploitation and a preparation method and application thereof, and aims to recycle the low-grade bauxite to reduce the manufacturing cost of the ceramic proppant.

[0005] In a first aspect, the present application discloses a ceramic proppant for shale gas exploitation, which comprises the following raw materials in parts by weight: 1-22 parts of oil-based rock debris, 4-18 parts of potassium feldspar powder and 66-95 parts of low-grade bauxite.

[0006] The mass percentage of Al2O3 in the low-grade bauxite is 45wt%-50wt%.

[0007] Optionally, the components of the potassium feldspar powder include SiO2, Al2O3 and K2O.

[0008] Optionally, the mass percentage of Al2O3 in the potassium feldspar powder is 18.4%.

[0009] In a second aspect, the present application further discloses a preparation method of the ceramic proppant of the first aspect, which comprises the following steps.

[0010] The oil-based rock debris is heated and ground at a temperature of 300-350 DEG C to obtain rock debris tailings with an oil content of less than 1%;

[0011] The rock debris tailings are sequentially calcined, crushed and sieved to obtain rock debris fine powder;

[0012] The rock debris fine powder is mixed with the potassium feldspar powder and the low-grade bauxite to obtain a mixed raw material powder.

[0013] The mixed raw material powder is granulated with water as a granulating medium to obtain green balls;

[0014] The green balls are sintered to obtain sintered haydite;

[0015] The sintered haydite is sieved to obtain haydite proppant.

[0016] Optionally, in the mixed raw material powder, the ratio by weight of the potassium feldspar powder to the low-grade bauxite is in the range of 1:3.5 to 1:24.

[0017] Optionally, in the mixed raw material powder, the mass percentage of the fine rock debris in the mixed raw material powder is 1-22% based on 100% of the mass of the mixed raw material powder.

[0018] Optionally, the mixing of the fine rock debris with the potassium feldspar powder and the low-grade bauxite to obtain the mixed raw material powder comprises:

[0019] The 1-15 parts of oil-based rock debris are mixed with 4-10 parts of potassium feldspar powder and 80-95 parts of low-grade bauxite to obtain the mixed raw material powder.

[0020] Optionally, the calcination temperature of the fine rock debris tailings is 600-650°C.

[0021] Optionally, the sintering temperature of the green balls is 1220-1300°C, and the sintering time is 1-2 hours.

[0022] In a third aspect, the application discloses the application of the haydite proppant of the first aspect in shale gas exploitation.

[0023] Based on the above technical solution, the application has the following beneficial effects compared with the prior art:

[0024] 1. In the haydite proppant of the application, the raw material is low-grade bauxite containing 45wt%-50wt% of alumina, and the proppant product has the properties of low density, high strength, high sphericity and low acid solubility. Therefore, by recycling the low-grade bauxite, the overall utilization rate of bauxite can be improved, the waste of bauxite can be avoided, and the use amount of high-grade bauxite can be reduced, which is conducive to maintaining the balance between supply and demand of high-grade bauxite. In addition, by introducing potassium feldspar powder, the supporting strength of the proppant can be enhanced, and the sintering temperature of the haydite proppant can be reduced, thereby saving energy. The liquid phase environment created by potassium feldspar is conducive to the mass transfer of aluminum and silicon elements, and it is easier to form mullite phase, which can effectively improve the sphericity and surface smoothness of the haydite proppant and reduce the shrinkage and deformation during the cooling process of the sintered haydite.

[0025] 2. The ceramsite proppant in this application uses oil-based rock cuttings, a hazardous waste generated during shale gas extraction, as a main raw material. It is combined with low-grade bauxite and potassium feldspar powder, and prepared using a solid-state sintering method. Since no organic reagents are used in the entire preparation process, the environmental pollution caused by oil-based rock cuttings and organic reagents is mitigated, making the entire preparation process more environmentally friendly.

[0026] 3. In the embodiments of this application, the ceramsite proppant uses potassium feldspar powder, which is cheaper, to supplement the content of alumina and silica, so that the overall mechanical properties of the proppant can meet the requirements, the production cost of the proppant is further reduced, and the economical preparation of ceramsite proppant is realized.

[0027] 4. The ceramsite proppant prepared in the embodiments of this application, under the set raw material composition and ratio, has a breakage rate between 3.73% and 8.11% at 35 MPa and between 4.31% and 8.91% at 69 MPa, with a sphericity higher than 0.9 and an acid solubility lower than 7%. Therefore, it can meet the mechanical properties and quality requirements of a proppant. Detailed Implementation

[0028] Exemplary embodiments of this disclosure will now be described in more detail. While exemplary embodiments of this disclosure have been shown, it should be understood that this disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0029] The inventors, referring to Chinese Patent No. CN116177883B – A High-Strength Ceramic Fracturing Proppant and Its Preparation Method – directly used oil-based rock cuttings as the sole raw material to prepare the ceramic proppant. The oil-based rock cuttings contained 15-30 wt% barium sulfate. However, barium sulfate decomposes during sintering, generating bubbles and reducing strength. Therefore, the ceramic proppant prepared by this process maintained a breakage rate of approximately 10% at 103 MPa, which is insufficient to meet the mechanical performance requirements of the proppant.

[0030] The inventors also referenced Chinese Patent CN116177881 B – An Ultra-Low Density Ceramic Fracturing Proppant and Its Preparation Method – to prepare ceramsite proppant using oil-based rock cuttings and quartz sand tailings as raw materials. To ensure that the strength, density, and other properties of the proppant product meet the required specifications, barium sulfate extraction is necessary before calcination of the dried oil-based rock cuttings. Specifically, most of the barium sulfate needs to be separated through gravity separation, ensuring that the barium sulfate content in the dried slag is ≤5%. However, extracting barium sulfate from rock cuttings complicates the process and increases additional processing costs.

[0031] The inventors further refer to a Chinese patent with publication number CN115724679A - A kind of low-density high-strength environment-friendly ceramsite proppant and preparation method thereof, with 20-40% water-based drilling cuttings and 60-80% bauxite as raw materials to prepare ceramsite proppant.The ceramsite proppant prepared by using the raw materials has a crushing rate of about 4% at 69MPa, which can meet the mechanical property requirements of proppant.However, the content of the key component aluminum oxide of the bauxite used by the proppant needs to be between 77-80%, which belongs to high-grade high-quality bauxite, and the use cost is higher, and its reserves are also declining, which is difficult to meet the high usage requirements in the production of the proppant.

[0032] In summary, the inventors found that when oil-based cuttings and bauxite are used as raw materials to make ceramsite proppant, aluminum oxide in bauxite is one of the most important components, which can provide physical strength and stability of the proppant, and has the most significant impact on the quality of the proppant.In general, within a certain range, by using bauxite with higher aluminum oxide content (more than 70%), the strength of the proppant can be improved.However, bauxite with high aluminum oxide content has a higher cost, and its reserves are also declining.This greatly increases the manufacturing cost of ceramsite proppant, and easily causes waste of high-grade bauxite resources.

[0033] Based on the above problems, the inventors further developed to reuse low-grade bauxite, in order to reduce the manufacturing cost of ceramsite proppant.

[0034] In a first aspect, the present application discloses a ceramsite proppant for shale gas exploitation, which comprises the following raw materials in parts by weight: 1-22 parts of oil-based cuttings, 4-18 parts of potassium feldspar powder and 66-95 parts of low-grade bauxite.The mass percentage of Al2O3 in the low-grade bauxite is 45wt%-50wt%.

[0035] The ceramsite proppant in the embodiments of the present application uses bauxite with 45wt%-50wt% of aluminum oxide as raw material, to realize the reuse of low-grade bauxite, avoid the waste of bauxite, and reduce the usage of high-grade bauxite.By introducing potassium feldspar powder with lower price, since potassium feldspar powder contains a certain content of aluminum oxide, it can play a role in supplementing the content of aluminum oxide.Potassium feldspar powder, as a mineral powder with good physical strength, can enhance the supporting strength of the proppant and change the pore structure of the proppant after being added.

[0036] In addition, since the potassium feldspar powder itself belongs to a monoclinic system and has a low melting point, the sintering temperature of the ceramsite proppant can be reduced, thereby saving energy. Further, the liquid phase environment created by the potassium feldspar is conducive to the mass transfer of aluminum and silicon elements, and is more likely to form mullite, thereby effectively improving the sphericity, surface smoothness of the ceramsite proppant, and reducing shrinkage and deformation during the cooling process of the sintered ceramsite.

[0037] In some optional embodiments, the components of the potassium feldspar powder specifically include SiO2, Al2O3 and K2O, wherein the mass percentage of SiO2 is 64.7%, the mass percentage of Al2O3 is 18.4%, and the mass percentage of K2O is 16.9%. Therefore, the potassium feldspar powder in the embodiments of the present application contains a high content of SiO2 and Al2O3, which can supplement the content of aluminum and silicon.

[0038] In a second aspect, the present application discloses a preparation method of the above-mentioned ceramsite proppant, and the preparation method of the ceramsite proppant includes the following steps S1-S6:

[0039] S1: Heating and grinding the oil-based cuttings at a temperature of 300-350℃ to obtain cuttings tailings with an oil content of less than 1%. Specifically, the oil-based cuttings can be placed in a heating furnace, and electromagnetic heating and ball milling are combined as the heating method. The heating time can be 1h.

[0040] S2: The cuttings tailings are sequentially calcined, crushed and sieved to obtain cuttings fine powder. Specifically, the calcination temperature of the cuttings tailings can be 600-650℃.

[0041] S3: The cuttings fine powder is mixed with potassium feldspar powder and low-grade bauxite to obtain a mixed raw material powder. Specifically, in the mixed raw material powder, the weight ratio of the potassium feldspar powder to the low-grade bauxite ranges from 1:3.5 to 1:24. And the mass percentage of the cuttings fine powder in the mixed raw material powder is 1-22% based on 100% of the mass of the mixed raw material powder. As an option, the mixed raw material powder includes 1-15 parts of oil-based cuttings, 4-10 parts of potassium feldspar powder and 80-95 parts of low-grade bauxite.

[0042] S4: The mixed raw material powder is granulated with water as the granulation medium to obtain green balls. Specifically, the mixed raw material powder can be added to a powerful balling machine for granulation at a rotation speed of 540r / min.

[0043] S5: The green balls are sintered to obtain sintered ceramsite. Specifically, the green balls can be sieved through a 30-mesh sieve before sintering. The sintering temperature of the green balls is 1220-1300℃, and the sintering time is 1-2h.

[0044] S6: sieving the sintered haydite to obtain the haydite proppant. Specifically, the sintered haydite can be sieved through a 40-70 mesh sieve after being cooled to obtain the haydite proppant.

[0045] In a third aspect, the application further discloses application of the haydite proppant in shale gas exploitation. The haydite proppant in the application has a breakage rate of 4.97% under a closed pressure of 35 MPa, a breakage rate of 6.77% under a closed pressure of 69 MPa, a sphericity of >0.9, and an acid solubility of <7%, and has good performance indexes. The haydite proppant in the application can be used as a filler in the process of oil and gas exploitation to increase the yield, flow conductivity, permeability and service life of oil and gas wells.

[0046] The application will be described in detail below through specific examples:

[0047] Example 1

[0048] The preparation process of the haydite proppant in the application includes the following steps S1-S7:

[0049] S1: placing the oil-based rock debris in a heating furnace, using electromagnetic + ball milling as the heating method, and staying at a temperature of 325℃ for 1h to obtain rock debris tailings with an oil content of less than 1%.

[0050] S2: calcining the rock debris tailings at a temperature of 600℃ for 2h to obtain rock debris ash, and then sequentially crushing, ball milling and sieving through a 300 mesh sieve to obtain rock debris fine powder.

[0051] S3: mixing 1 part of the rock debris fine powder, 4 parts of potassium feldspar powder and 95 parts of low-grade bauxite to obtain mixed raw material powder. The potassium feldspar powder has a composition of 64.7% SiO2, 18.4% Al2O3 and 16.9% K2O, and the low-grade bauxite has an Al2O3 content of 45wt%-50wt%.

[0052] S4: adding the mixed raw material powder into a powerful balling machine to granulate at a rotating speed of 540r / min, and adding an appropriate amount of tap water as the balling medium to obtain green balls.

[0053] S5: sieving the green balls through a 30 mesh sieve, and then sintering at a temperature of 1300℃ for 1h to obtain sintered haydite.

[0054] S6: sieving the sintered haydite after being cooled through a 40-70 mesh sieve to obtain the final haydite proppant.

[0055] The haydite proppant has a breakage rate of 4.97% under a closed pressure of 35 MPa, a breakage rate of 6.77% under a closed pressure of 69 MPa, a sphericity of >0.9, and an acid solubility of <7%.

[0056] Example 2

[0057] This example differs from Example 1 in that, in Step S4, 5 parts of the fine rock powder, 10 parts of the potassium feldspar powder, and 85 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1300°C for 1.5 h to obtain a sintered haydite.

[0058] Example 3

[0059] This example differs from Example 1 in that, in Step S4, 8 parts of the fine rock powder, 12 parts of the potassium feldspar powder, and 80 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1280°C for 2 h to obtain a sintered haydite.

[0060] Example 4

[0061] This example differs from Example 1 in that, in Step S4, 10 parts of the fine rock powder, 10 parts of the potassium feldspar powder, and 80 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1280°C for 1.5 h to obtain a sintered haydite.

[0062] Example 5

[0063] This example differs from Example 1 in that, in Step S4, 10 parts of the fine rock powder, 15 parts of the potassium feldspar powder, and 75 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1220°C for 2 h to obtain a sintered haydite.

[0064] Example 6

[0065] This example differs from Example 1 in that, in Step S4, 15 parts of the fine rock powder, 18 parts of the potassium feldspar powder, and 67 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1240°C for 2 h to obtain a sintered haydite.

[0066] Example 7

[0067] This example differs from Example 1 in that, in Step S4, 15 parts of the fine rock powder, 5 parts of the potassium feldspar powder, and 80 parts of the low-grade bauxite are mixed to obtain a mixed raw material powder. In Step S6, sintering is performed at a temperature of 1240°C for 1.5 h to obtain a sintered haydite.

[0068] Example 8

[0069] The difference between this embodiment and embodiment 1 is that in step S4, 18 parts of the fine rock debris powder, 10 parts of the potassium feldspar powder and 72 parts of the low-grade bauxite are mixed to obtain the mixed raw material powder. In step S6, sintering is performed at a temperature of 1260°C for 1.5h to obtain the sintered ceramsite.

[0070] Embodiment 9

[0071] The difference between this embodiment and embodiment 1 is that in step S4, 20 parts of the fine rock debris powder, 8 parts of the potassium feldspar powder and 72 parts of the low-grade bauxite are mixed to obtain the mixed raw material powder. In step S6, sintering is performed at a temperature of 1240°C for 1.5h to obtain the sintered ceramsite.

[0072] Embodiment 10

[0073] The difference between this embodiment and embodiment 1 is that in step S4, 22 parts of the fine rock debris powder, 12 parts of the potassium feldspar powder and 66 parts of the low-grade bauxite are mixed to obtain the mixed raw material powder. In step S6, sintering is performed at a temperature of 1240°C for 2h to obtain the sintered ceramsite.

[0074] The conditions for preparing the ceramsite proppants in embodiments 1-10 of the present application are shown in Table 1:

[0075] Table 1 Preparation conditions of the ceramsite proppants in embodiments 1-10

[0076]

[0077] The performance parameters of the ceramsite proppants prepared in embodiments 1-10 of the present application are shown in Table 2:

[0078] Table 2 Performance parameters of the ceramsite proppants in embodiments 1-10

[0079]

[0080] As shown in Table 2, the ceramsite proppants prepared in the embodiments of the present application have the characteristics of low density, high strength, high sphericity and low acid solubility. The breakage rate at 35MPa is between 3.73-8.11%, the breakage rate at 69MPa is between 4.31-8.91%, the sphericity is higher than 0.9 and the acid solubility is lower than 7%.

[0081] The above description includes examples of one or more embodiments. Of course, not all possible combinations of components or methods described above can be claimed as an embodiment, but one of ordinary skill in the art will recognize that further combinations and permutations of the embodiments described herein are possible. Therefore, the description herein is intended to cover all such modification and variations as are within the scope of the appended claims. Further, the use of the term "comprising" in the description or claims is not intended to exclude any embodiments except those claimed in the claims. In addition, the use of the term "or" is intended to mean "and / or" unless otherwise indicated.

Claims

1. A shale gas development ceramic proppant characterized by, The raw materials include 1-22 parts of oil-based rock debris, 4-18 parts of potassium feldspar powder and 66-95 parts of low-grade bauxite. The mass percentage of Al2O3 in the low-grade bauxite is 45wt%-50wt%.

2. The ceramsite proppant of claim 1, wherein, The components of the potassium feldspar powder include SiO2, Al2O3 and K2O.

3. The ceramsite proppant of claim 2, wherein, The mass percentage of Al2O3 in the potassium feldspar powder is 18.4%.

4. The method of making ceramic proppants according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The oil-based rock debris is heated and ground at a temperature of 300-350℃ to obtain rock debris tailings with an oil content of less than 1%; The rock debris tailings are sequentially calcined, crushed and sieved to obtain rock debris fine powder; The rock debris fine powder is mixed with potassium feldspar powder and low-grade bauxite to obtain mixed raw material powder; The mixed raw material powder is granulated with water as the granulation medium to obtain green balls; The green balls are sintered to obtain sintered haydite; The sintered haydite is sieved to obtain haydite proppant.

5. The preparation method according to claim 4, characterized in that, In the mixed raw material powder, the weight ratio of the potassium feldspar powder to the low-grade bauxite ranges from 1:3.5 to 1:

24.

6. The preparation method according to claim 5, characterized in that, In the mixed raw material powder, the mass percentage of the rock debris fine powder is 1-22% based on 100% of the mass of the mixed raw material powder.

7. The preparation method according to claim 6, characterized in that, The rock debris fine powder is mixed with potassium feldspar powder and low-grade bauxite to obtain mixed raw material powder, which comprises the following steps: 1-15 parts of oil-based rock debris are mixed with 4-10 parts of potassium feldspar powder and 80-95 parts of low-grade bauxite to obtain mixed raw material powder.

8. The preparation method according to claim 4, characterized in that, The calcination temperature of the rock debris tailings is 600-650℃.

9. The preparation method according to claim 4, characterized in that, The sintering temperature of the green balls is 1220-1300℃, and the sintering time is 1-2h.

10. Application of the haydite proppant of any one of claims 1-3 in shale gas exploitation.

Images