A low-density and high-strength micro-nano ceramic proppant and preparation method thereof

Abstract

The present invention discloses a low-density and high-strength micro-nano ceramic proppant and a preparation method thereof, belonging to the technical field of oil exploitation. The bulk density of the proppant is 1.0 - 1.5 g / cm<supgt;3< / supgt>, the true density is 2.4 - 2.8 g / cm<supgt;3< / supgt>, and the compressive strength is 52 - 103 MPa. The preparation method is as follows: mixing powders of drilling cuttings, bauxite and potassium feldspar, adding water and stirring evenly to form a slurry; grinding the slurry, adding a binder and a dispersant, stirring evenly and aging; placing the aged product in a centrifugal spray drying tower for forming to obtain a proppant green body; sintering the green body to obtain the product. By using drilling cuttings as raw materials to prepare the micro-nano ceramic proppant, the present invention solves the problems of stacking and treatment of drilling cuttings, and realizes the recycling and reuse of drilling cuttings; at the same time, the prepared micro-nano ceramic proppant has ultra-low density and high strength.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a low-density and high-strength micro-nano ceramic proppant and a preparation method thereof. Background Art

[0002] Oil fracturing proppant is a kind of seam filling material used in oil extraction. With the deepening of oil extraction, in order to increase oil well production and extend the exploitation period, proppant needs to be injected into the fracturing fluid during oil extraction to keep the extraction cracks open to ensure the smooth progress of oil extraction.

[0003] At present, the petroleum fracturing proppants used in the market mainly include natural quartz sand, micro-nano ceramic proppants, and resin-coated sand. Commonly used micro-nano ceramic proppants are generally based on quartz sand, bauxite, kaolin, etc.

[0004] Traditional micro-nano ceramic proppants are made of bauxite and hard clay as raw materials, through powder granulation and high-temperature sintering, and the binding phase of the finished product is a high-strength corundum mullite phase. However, with the large-scale development and utilization of mine resources in my country, the price of bauxite, the main raw material for making ceramsite or micro-nano ceramic microbeads by traditional methods, has not only risen sharply, but also the bauxite resources are becoming increasingly scarce. Therefore, finding cheap, effective and alternative raw materials to produce low-density and high-strength micro-nano ceramic proppants has always been one of the goals pursued in this field.

[0005] In addition, bauxite, as a mineral raw material, is a non-renewable resource. As time goes by, the supply of bauxite resources is becoming increasingly scarce.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a low-density and high-strength micro-nano ceramic proppant and a preparation method thereof. By using drilling cuttings as raw materials to prepare the micro-nano ceramic proppant, the problem of stacking and processing drilling cuttings is solved, and the recycling and reuse of drilling cuttings is realized. At the same time, the prepared micro-nano ceramic proppant has ultra-low density and high strength.

[0008] To achieve the above objectives, the present invention adopts the following specific technical solutions:

[0009] A low-density, high-strength micro-nano ceramic proppant, wherein the bulk density of the proppant is 1.0-1.5 g / cm 3 , true density is 2.4-2.8g / cm 3 , the compressive strength is 52-103MPa.

[0010] Furthermore, the proppant comprises drilling cuttings, bauxite and potassium feldspar.

[0011] Furthermore, the drilling cuttings, bauxite and potassium feldspar are 45-75 parts, 20-45 parts and 5-10 parts respectively by weight. The addition of potassium feldspar can reduce the sintering temperature.

[0012] Preferably, the particle size of the proppant is 20-140 mesh.

[0013] More preferably, the particle size of the proppant is 20-40 mesh, 40-70 mesh or 70-140 mesh.

[0014] Furthermore, the proppant has a turbidity of ≤40, an acid solubility of ≤7, and a sphericity of ≥0.9.

[0015] The present invention also provides a method for preparing the low-density and high-strength micro-nano ceramic proppant, comprising the following steps:

[0016] S1: Mix the powders of drilling cuttings, bauxite and feldspar, add water and stir evenly to form a slurry. The drilling cuttings can be recycled and reused, bauxite can increase the strength of the proppant, and feldspar can reduce the sintering temperature.

[0017] Furthermore, in terms of mass, the drilling cuttings, bauxite and potassium feldspar are 45-75 parts, 20-45 parts and 5-10 parts respectively.

[0018] Furthermore, the particle size of the powder of drilling cuttings, bauxite and potassium feldspar is 30-150 μm.

[0019] Preferably, the particle size of the drilling cuttings powder is 30-80 μm, the particle size of the bauxite powder is 40-100 μm, and the particle size of the potassium feldspar powder is 30-150 μm.

[0020] S2: Grind the slurry, add a binder and a dispersant, stir evenly, and then age.

[0021] Preferably, the grinding is performed to grind the slurry to a particle size of ≤6 μm, and the sphericity thereof is the highest during centrifugal spray drying.

[0022] Preferably, the binder includes one or more of polyvinyl alcohol, water glass, paraffin or polyvinyl chloride; the dispersant includes one or more of ammonium citrate, polyacrylic acid, methyl cellulose or sodium alginate.

[0023] Furthermore, the aging time is 3-5 hours, so that the slurry, the binder and the dispersant can be evenly mixed. Furthermore, after aging, the viscosity of the slurry is controlled to be 18-25 seconds.

[0024] S3: The aged product is placed in a centrifugal spray drying tower for forming to obtain a proppant blank. The centrifugal spray drying tower has an air inlet temperature of 200-500°C, an air outlet temperature of 110-150°C, a feed rate of 10-20kg / min, and an atomizing disk speed of 15-50Hz.

[0025] Preferably, the aged product is injected into the centrifugal spray drying tower through a diaphragm pump.

[0026] Preferably, the particle size of the proppant blank is 20-140 mesh.

[0027] Preferably, by controlling the centrifugal spray drying molding technology, combined with adjusting the slurry viscosity and the rotation speed of the atomizing disk, the sphericity of the proppant blank is greater than 0.9.

[0028] S4: Sintering the green body to obtain.

[0029] Furthermore, the sintering temperature is 1100-1280°C, at which the proppant can be vitrified to achieve a smooth surface and acid resistance, thereby making the proppant turbidity ≤40 and the acid solubility ≤7. At the same time, if the sintering temperature is too low, the strength of the proppant cannot reach 52MPa, and if the sintering temperature is too high, the proppant is prone to adhesion, resulting in a low yield.

[0030] Compared with the prior art, the present invention uses drilling cuttings as raw materials to prepare micro-nano ceramic proppants, which not only solves the problem of the stacking of solid waste such as drilling cuttings, but also solves the problem of the decreasing bauxite resources, so that the back-end product of drilling cuttings, micro-nano ceramic microbeads, has high added value, and realizes the recycling and reuse of drilling cuttings. At the same time, the preparation process is simple, and the prepared micro-nano ceramic proppants have ultra-low density and high strength, which are particularly suitable for the field of shale oil mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0032] Figure 1 This is a sample picture of the proppant prepared in Example 3;

[0033] Figure 2 This is a light microscope image of the proppant prepared in Example 3. DETAILED DESCRIPTION

[0034] The embodiments of the present invention will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If specific conditions are not specified in the examples, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0035] Example 1

[0036] A method for preparing a low-density and high-strength micro-nano ceramic proppant:

[0037] Drilling cuttings with an average particle size of 80 μm, bauxite and potassium feldspar are mixed in a mass ratio of 6:3:1, and water of 0.8 times the mass of the raw materials is added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to 6 μm, and the slurry is injected into an aging tank. After the slurry is injected, polyvinyl alcohol and methyl cellulose are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 20 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 350°C, the outlet temperature is controlled to be 150°C, the feed rate is 20kg / min, and the atomizing disk speed is 45Hz. A proppant blank with a roundness greater than 0.9 is obtained. The blank is sent to a rotary kiln through a belt conveyor and sintered at 1280°C. A 20-40 mesh micro-nano ceramic proppant is obtained by screening, and its bulk density is measured to be 1.2 g / cm 3 , the true density is 2.45g / cm 3 , compressive strength is 52MPa, turbidity is 39, acid solubility is 6.7. Because ultra-low density micro-nano ceramic proppants can be prepared, when used in oil field fracturing, they do not precipitate in the fracturing fluid, are easy to pipe, and have good fracturing effects.

[0038] Example 2

[0039] A method for preparing a low-density and high-strength micro-nano ceramic proppant:

[0040] Drilling cuttings with an average particle size of 75 μm, bauxite and potassium feldspar are mixed in a mass ratio of 5:3.5:1.5, and 0.8 times the mass of water of the raw materials is added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to 5 μm, and the slurry is injected into an aging tank. After the slurry is injected, water glass and ammonium citrate are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 25 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 250°C, the outlet temperature is controlled to be 110°C, the feed rate is 10kg / min, and the atomizing disk speed is 20Hz. A proppant blank with a roundness greater than 0.9 is obtained. The blank is sent to a rotary kiln through a belt conveyor and sintered at 1280°C. A micro-nano ceramic proppant with a mesh size of 40-70 is obtained by screening, and its bulk density is measured to be 1.3g / cm 3 , true density is 2.6g / cm 3 , compressive strength is 69MPa, turbidity is 35, and acid solubility is 6.0.

[0041] Example 3

[0042] A method for preparing a low-density and high-strength micro-nano ceramic proppant:

[0043] Drilling cuttings with an average particle size of 35 μm, bauxite and potassium feldspar with an average particle size of 100 μm are mixed in a mass ratio of 4.5:4.5:1, and 0.8 times the mass of water of the raw materials are added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to be 6 μm, and the slurry is injected into an aging tank. After the slurry is injected, paraffin and polyacrylic acid are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 20 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 300°C, the outlet temperature is controlled to be 130°C, the feed rate is 15kg / min, and the atomizing disk speed is 35Hz. A proppant blank with a roundness greater than 0.9 is obtained. The blank is sent to a rotary kiln through a belt conveyor and sintered at 1180°C. A 70-140 mesh micro-nano ceramic proppant is obtained by screening, such as Figure 1 Sample pictures and Figure 2 The measured bulk density is 1.0 g / cm 3 , the true density is 2.40g / cm 3 , compressive strength is 103MPa, turbidity is 33, and acid solubility is 5.9.

[0044] Example 4

[0045] A method for preparing a low-density and high-strength micro-nano ceramic proppant:

[0046] Drilling cuttings with an average particle size of 30 μm, bauxite and potassium feldspar are mixed in a mass ratio of 7:2:1, and water of 0.8 times the mass of the raw materials is added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to 6 μm, and the slurry is injected into an aging tank. After the slurry is injected, polyvinyl chloride and sodium alginate are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 18 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 450°C, the outlet temperature is controlled to be 150°C, the feed rate is 20kg / min, and the atomizing disk speed is 50Hz. A proppant blank with a roundness greater than 0.9 is obtained. The blank is sent to a rotary kiln through a belt conveyor and sintered at 1100°C. A 40-70 mesh micro-nano ceramic proppant is obtained by screening, and its bulk density is measured to be 1.4g / cm 3 , the true density is 2.42g / cm 3 , compressive strength is 69MPa, turbidity is 35, and acid solubility is 6.1.

[0047] Example 5

[0048] A method for preparing a low-density and high-strength micro-nano ceramic proppant:

[0049] Drilling cuttings with an average particle size of 80 μm, bauxite and potassium feldspar are mixed in a mass ratio of 6.5:2.5:1, and water of 0.8 times the mass of the raw materials is added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to 6 μm, and the slurry is injected into an aging tank. After the slurry is injected, water glass and ammonium citrate are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 20 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 300°C, the outlet temperature is controlled to be 130°C, the feed rate is 15kg / min, and the atomizing disk speed is 35Hz. A proppant blank with a roundness greater than 0.9 is obtained. The blank is sent to a rotary kiln through a belt conveyor and sintered at 1200°C. A 40-70 mesh micro-nano ceramic proppant is obtained by screening, and its bulk density is measured to be 1.3g / cm 3 , the true density is 2.46g / cm 3 , compressive strength is 89MPa, turbidity is 38, and acid solubility is 6.8.

[0050] Example 6

[0051] The difference from Example 3 is that the average particle size of drilling cuttings, bauxite and potassium feldspar is 75 μm, and the roundness of the obtained proppant blank is greater than 0.9, and its bulk density is measured to be 1.2 g / cm 3 , the true density is 2.48g / cm 3, compressive strength is 89MPa, turbidity is 36, and acid solubility is 6.9.

[0052] Comparative Example 1

[0053] The difference from Example 3 is that the viscosity of the slurry is controlled to be 28 seconds during aging, a proppant blank with a roundness greater than 0.9 is obtained, and the measured proppant bulk density is 1.8 g / cm 3 , true density is 2.75g / cm 3 , compressive strength is 77MPa, turbidity is 40, and acid solubility is 7.3.

[0054] Comparative Example 2

[0055] The difference from Example 3 is that the viscosity of the slurry is controlled to be 15 seconds during aging, a proppant blank with a roundness greater than 0.9 is obtained, and the measured proppant bulk density is 1.5 g / cm 3 , the true density is 2.55g / cm 3 , compressive strength is 47MPa, turbidity is 38, and acid solubility is 6.8.

[0056] Comparative Example 3

[0057] The difference from Example 3 is that the sintering temperature is 1350°C, the roundness of the obtained proppant blank is greater than 0.9, and the measured proppant bulk density is 1.4 g / cm 3 , the true density is 2.52g / cm 3 , the compressive strength is 56MPa, the turbidity is 48, the acid solubility is 8.1, the proppant is easy to stick together, and the yield is low.

[0058] Comparative Example 4

[0059] The difference from Example 3 is that the sintering temperature is 1000°C, the roundness of the obtained proppant body is greater than 0.9, and the measured proppant bulk density is 1.8 g / cm 3 , true density is 2.65g / cm 3 , compressive strength is 32MPa, turbidity is 39, and acid solubility is 7.8.

[0060] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0061] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and to form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a low-density and high-strength micro-nano ceramic proppant, characterized in that: include: Drilling cuttings with an average particle size of 35 μm, bauxite and potassium feldspar with an average particle size of 100 μm are mixed in a mass ratio of 4.5:4.5:1, and water of 0.8 times the mass of the raw materials is added to mix evenly. Then, the slurry is ground by a grinder to control the particle size of the slurry to be 6 μm, and the slurry is injected into an aging tank. After the slurry is injected, paraffin and polyacrylic acid are added respectively, and the slurry is aged after stirring evenly. The viscosity of the slurry is controlled to be 20 seconds. The aged slurry is injected into a centrifugal spray drying tower through a diaphragm pump for molding. The inlet temperature of the centrifugal spray drying tower is controlled to be 300° C., the outlet temperature is controlled to be 130° C., the feed rate is 15 kg / min, and the atomizing disk speed is 35 Hz. A proppant green body with a roundness greater than 0.9 is obtained, and the green body is sent to a rotary kiln through a belt conveyor and sintered at 1180° C., and a 70-140 mesh micro-nano ceramic proppant is obtained by screening.

Images