Lightweight and high-strength proppant prepared from water-based rock cuttings and preparation method thereof

Abstract

The invention discloses a light and high-strength proppant prepared by using water-based rock cuttings and a preparation method thereof. The light and high-strength proppant is composed of water-based rock cuttings A and water-based rock cuttings B. The water-based rock cuttings are used as raw materials, no additives are required, and the raw materials are evenly mixed by ball milling through a reasonable mass ratio, and then water is added to granulate the raw materials by spraying to form a green body, and heat treatment is performed using different sintering atmospheres to obtain a light and high-strength proppant; corundum phase and mullite phase can be obtained by using water-based rock cuttings A and B, and the mullite phase has high hardness and toughness, which can make the proppant have high strength; the corundum phase has high hardness, which can improve the mechanical properties of the proppant. The light and high-strength proppant prepared by the water-based rock cuttings of the present invention can realize the recycling of water-based rock cuttings, which is conducive to solving environmental pollution problems and is expected to be used in the field of oil and gas production.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and resource recycling, and particularly relates to a light and high-strength proppant prepared from water-based rock cuttings and a preparation method thereof. Background Art

[0002] Water-based cuttings are a type of solid waste generated during oil exploration and development, with the main components being shale, bentonite, lubricants, chlorides, etc. If water-based cuttings are not treated or treated improperly, they can easily cause environmental pollution and harm human health. In recent years, as my country has paid more attention to environmental issues, it has required solid waste to be reduced, environmentally friendly, and resource-based. Surveys have shown that my country does not yet have the ability to efficiently, large-scale, and industrially treat water-based cuttings. Therefore, there is an urgent need to develop new ways to treat water-based cuttings harmlessly and as a resource.

[0003] Proppants are divided into ultra-low density (ultra-lightweight) proppants, low-density (lightweight) proppants, medium-density proppants and high-density proppants according to their bulk density and apparent density. The bulk density of ultra-low density proppants is less than 1.50 g / cm 3 , apparent density <2.60 g / cm 3 , low-density proppant bulk density is 1.50~1.65 g / cm 3 , apparent density is 2.60~3.00 g / cm 3 The volume density of medium-density proppant is 1.65~1.80 g / cm 3 , apparent density is 3.00~3.35 g / cm 3 , high-density proppant volume density>1.80 g / cm 3 , apparent density>3.35 g / cm 3 . Generally, medium-density and high-density proppants have higher requirements on pumping conditions and the performance of fracturing fluids, increasing the difficulty of construction. In addition, they are prone to produce shorter support belts during application, which accumulate at the ends of the fractures, which is extremely unfavorable for diversion, thus affecting the subsequent oil production effect. In contrast, ultra-low-density and low-density proppants are easier to carry under the fracturing fluid, which can greatly reduce the viscosity of the fracturing fluid, reduce damage to pipelines and pumps, achieve clean fracturing, and have a low diversion decline rate, effectively reducing the difficulty of construction and oil production costs.

[0004] Although the prior art has disclosed the use of water-based rock cuttings to prepare proppants, bauxite and additives are often added to enhance the strength of the proppant, and the density and strength of the proppant cannot be regulated. There are problems such as cumbersome preparation process and difficulty in balancing density and strength. In particular, it is difficult to obtain a proppant with both low density and high strength. This is because increasing the strength of the proppant usually increases the density; reducing the strength of the proppant usually reduces the density. Water-based rock cuttings contain K2O and Na2O in their chemical composition, and modulation of these two components can achieve the regulation of the material's pores, density and mechanical properties. At present, the modulation of K2O and Na2O components has not been used to achieve the recycling of water-based rock cuttings resources. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a lightweight and high-strength proppant prepared with water-based rock cuttings and a preparation method thereof, so as to solve the current problem that it is difficult to prepare a proppant with both low density and high strength.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a light and high-strength proppant prepared from water-based rock cuttings, which comprises, by weight, 100 parts of water-based rock cuttings A and 10 parts of water-based rock cuttings B; the components of the water-based rock cuttings A, by weight, comprise 12.0-14.0 parts of Al2O3, 3.60-3.80 parts of Fe2O3, 0.40-0.60 parts of TiO2, 1.80-2.10 parts of K2O, 0.60-0.80 parts of Na2O, 18.00-19.0 parts of CaO. 0 parts, MgO2 2.60~24.80 parts; the components of water-based rock cuttings B, by mass, include Al2O3 16.00~18.00 parts, SiO2 48.00~52.00 parts, Fe2O3 5.00~6.00 parts, TiO2 0.60~0.90 parts, K2O 2.00~4.00 parts, Na2O 1.00~2.00 parts, CaO 1.80~3.50 parts, MgO 2.50~3.60 parts.

[0008] Preferably, the mass fractions of CaO and MgO in the water-based cuttings A are both greater than 10%.

[0009] Preferably, the molar ratio of Al2O3 to SiO2 in the water-based cuttings B is less than 2.

[0010] Preferably, the bulk density of the lightweight high-strength proppant is 1.54-1.71 g / cm 3 , apparent density is 2.71~3.12 g / cm 3 .

[0011] The present invention also discloses a method for preparing the above-mentioned lightweight and high-strength proppant, comprising the following steps:

[0012] Step 1, weighing water-based rock cuttings A and water-based rock cuttings B raw materials, ball milling and mixing them evenly, granulating, drying, and making green bodies;

[0013] Step 2: heat-treating the green body under different sintering atmospheres and cooling it to room temperature to obtain a light and high-strength proppant.

[0014] Preferably, in step 1, the ball milling speed is 100 r / min; the drying temperature is 80-120° C., and the drying time is 4-12 h.

[0015] Preferably, in step 2, the different sintering atmospheres are air atmosphere, oxygen atmosphere, hydrogen atmosphere or vacuum atmosphere.

[0016] Preferably, in an oxygen atmosphere, oxygen with a purity of 99.5% is used, and the oxygen flow rate is 10 L / min; in a hydrogen atmosphere, hydrogen with a purity of 99% is used, and the hydrogen flow rate is 10 L / min; in a vacuum atmosphere, the vacuum degree is 133 Pa.

[0017] Preferably, in step 2, the heat treatment is a two-step heat treatment method, firstly heating to 1250°C at 2°C / min and sintering for 5 minutes, then cooling to 1200°C at a cooling rate of 5°C / min and keeping at this temperature for 2 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention discloses a light and high-strength proppant prepared by using water-based rock cuttings, comprising water-based rock cuttings A and water-based rock cuttings B. The water-based rock cuttings A and B are used to obtain a corundum phase and a mullite phase, wherein the mullite phase has high hardness and toughness, which is the essential reason why the proppant has high strength; the corundum phase has high hardness, which can improve the mechanical properties of the proppant.

[0020] Furthermore, the bulk density of the obtained lightweight and high-strength proppant is 1.54-1.71 g / cm 3 , apparent density is 2.71~3.12g / cm 3 Low-density proppants are easier to carry under the fracturing fluid, which can greatly reduce the viscosity of the fracturing fluid, reduce damage to pipelines and pumps, achieve clean fracturing, and have a low diversion decline rate, effectively reducing construction difficulty and oil production costs.

[0021] Furthermore, the water-based rock cuttings A contain CaO and MgO in amounts greater than 10% by mass. CaO and MgO can form a liquid phase during the sintering process, which helps to improve the density of the proppant, thereby improving the strength of the proppant.

[0022] Furthermore, the molar ratio of Al2O3 to SiO2 is less than 2, and Al2O3 and SiO2 can form a mullite phase during the sintering process. Since the mullite phase has the properties of both light weight and high strength, it is helpful to obtain a light weight and high strength proppant.

[0023] The present invention also discloses a method for preparing the above-mentioned lightweight and high-strength proppant, which uses water-based rock cuttings as raw materials, does not require additives and component modulation, and can obtain a proppant with both low density and high strength by changing the sintering atmosphere and modulating the K2O and Na2O contents in the water-based rock cuttings. At the same time, the water-based rock cuttings can be recycled and reused, which is beneficial to solving environmental pollution problems and can be used for oil and gas production.

[0024] Furthermore, the different sintering atmospheres are air atmosphere, oxygen atmosphere, hydrogen atmosphere or vacuum atmosphere. By changing the sintering atmosphere and utilizing the different volatilization degrees of K2O and Na2O in oxygen atmosphere, air atmosphere, hydrogen atmosphere and vacuum atmosphere, the contents of K2O and Na2O in the water-based cuttings during the sintering process can be effectively controlled, thereby affecting the liquid phase contents of K2O and Na2O, and further regulating the density and strength of the proppant. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD diagram of the lightweight and high-strength proppant obtained in Example 3 of the present invention when the sintering atmosphere is a hydrogen atmosphere;

[0026] Figure 2 This is a SEM image of a lightweight high-strength proppant obtained in Example 3 of the present invention in which the sintering atmosphere is a hydrogen atmosphere; in the image, M represents the mullite phase, and the light-colored grains are the corundum phase. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] The light and high-strength proppant of the present invention comprises two kinds of water-based rock chips containing K2O and Na2O, namely water-based rock chips A and water-based rock chips B. The components of water-based rock chips A include 12.0-14.0 parts of Al2O3, 3.60-3.80 parts of Fe2O3, 0.40-0.60 parts of TiO2, 1.80-2.10 parts of K2O, 0.60-0.80 parts of Na2O, 18.00-19.00 parts of CaO, and 2.60-24.80 parts of MgO2; the water-based rock chips A comprises 12.0-14.0 parts of Al2O3, 3.60-3.80 parts of Fe2O3, 0.40-0.60 parts of TiO2, 1.80-2.10 parts of K2O, 0.60-0.80 parts of Na2O, 18.00-19.00 parts of CaO, and 2.60-24.80 parts of MgO2. The components of cuttings B include 16.00~18.00 parts of Al2O3, 48.00~52.00 parts of SiO2, 5.00~6.00 parts of Fe2O3, 0.60~0.90 parts of TiO2, 2.00~4.00 parts of K2O, 1.00~2.00 parts of Na2O, 1.80~3.50 parts of CaO, and 2.50~3.60 parts of MgO, wherein the water-based cuttings A contain CaO and MgO with a mass fraction greater than 10%; the crushing rate of the proppant is less than 10%.

[0030] The preparation method of the light-weight and high-strength proppant provided by the present invention is as follows: after the uniformly mixed raw materials are ball-milled and mixed, granulation is carried out to form spherical green bodies with a diameter of 0.8 cm, and sintering is carried out for heat treatment under different atmospheres, including air atmosphere, oxygen atmosphere, hydrogen atmosphere and vacuum atmosphere, and cooling to room temperature with the furnace to obtain a light-weight and high-strength proppant sample.

[0031] In the above preparation method, the uniformly mixed raw materials are water-based rock cuttings A and water-based rock cuttings B containing K2O and Na2O.

[0032] In the above preparation method, the mass ratio of water-based rock cuttings A to water-based rock cuttings B is 100:10.

[0033] In the above preparation method, the sintering atmosphere includes air atmosphere, oxygen atmosphere, hydrogen atmosphere and vacuum atmosphere.

[0034] In the above preparation method, the heat treatment is a two-step heat treatment method, firstly, the temperature is raised to 1250°C at a rate of 2°C / min and sintered for 5 minutes, then the temperature is lowered to 1200°C at a rate of 5°C / min and kept at this temperature for 2 hours, and then the furnace is cooled to room temperature.

[0035] Table 1 Composition of two water-based cuttings

[0036]

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0038] Example 1

[0039] In this embodiment, water-based rock cuttings A and water-based rock cuttings B are used as raw materials, and the composition is shown in Table 1, and the mass ratio is 100:10. According to the mass ratio, 10 kg of water-based rock cuttings A and 1.0 kg of water-based rock cuttings B are weighed, and the mixture is uniformly mixed in a ball mill at a speed of 100 r / min. The powder is added to a granulator, and water is added to granulate by spraying, and a 0.8 cm spherical green body is obtained at 80-120 ° C for a drying time of 4-12 h. The green body is sintered in an air atmosphere in a muffle furnace, and the heating program and the cooling program are controlled. The temperature is first raised to 1250 ° C at 2 ° C / min and sintered for 5 min, and then the temperature is lowered to 1200 ° C at a cooling rate of 5 ° C / min, and the temperature is kept for 2 h, and the sample is cooled to room temperature with the furnace to obtain a sample, which is numbered 1#, and its performance is shown in Table 2.

[0040] Example 2

[0041] The difference between this embodiment and embodiment 1 is that the sintering atmosphere is an oxygen atmosphere. The use of oxygen atmosphere means that oxygen with a purity of 99.5% is introduced into the muffle furnace, and the oxygen flow rate is maintained at 10 L / min. The other processes are the same. The obtained sample is numbered 2#, and its performance is shown in Table 2.

[0042] Example 3

[0043] The difference between this embodiment and embodiment 1 is that the sintering atmosphere is a hydrogen atmosphere. The use of a hydrogen atmosphere means that 99% pure hydrogen is introduced into the muffle furnace, and the oxygen flow rate is maintained at 10 L / min. The other processes are the same. The obtained sample is numbered 3#, and its properties are shown in Table 2. The phase composition and micromorphology characterization results of the obtained samples are shown in Figure 1 and Figure 2 .

[0044] Figure 1The XRD test results of Example 3 show that the peaks corresponding to the diamond marks are mullite phases, and the peaks corresponding to the circular marks are mullite and corundum phases. Among them, the mullite phase has high hardness and toughness, which is the essential reason why the proppant has high strength; the corundum phase has high hardness and can improve the mechanical properties of the proppant. Therefore, it can be concluded from the XRD test results that the proppant has a lower breakage rate under hydrogen atmosphere. Figure 2 The SEM characterization results of Example 3, the letter M corresponds to the micromorphology and grains of the mullite phase, and the letter M corresponds to the micromorphology and grains of the corundum phase. The SEM characterization results show that the proppant sample contains both mullite and corundum phases, which corresponds to the XRD test results. It can also be seen from the figure that the distribution of the mullite phase and the corundum phase is relatively uniform, the grain size is between 200-500 nm, and there are relatively uniform refined grains. Studies have shown that the finer the grains, the fewer defects in the material, and the higher the degree of grain slip along the grain boundary, so that the material has higher mechanical properties, which can improve the mechanical properties of the proppant sample and reduce the crushing rate. In addition, the figure shows that the proppant sample has fewer pores (black tiny holes), that is, it has a higher density. The higher the density, the fewer defects in the material, which can improve the mechanical properties of the proppant sample, so that the crushing rate of the proppant sample obtained under the hydrogen atmosphere is lower. Therefore, the proppant sample obtained by the present invention has both low density and high strength.

[0045] Example 4

[0046] The difference between this embodiment and embodiment 1 is that the sintering atmosphere is a vacuum atmosphere. The use of a vacuum atmosphere means that a vacuum treatment is performed in a muffle furnace and the vacuum degree is maintained at 133 Pa. The other processes are the same. The obtained sample is numbered 4#, and its properties are shown in Table 2.

[0047] Table 2 Indicators of samples

[0048]

[0049] It can be seen from the examples that sintering in different atmospheres has a great influence on various indicators of the samples. The sample obtained in oxygen atmosphere has the largest volume density and apparent density, but the crushing rate is lower; the volume density and apparent density of the sample obtained in air atmosphere are lower than those of the sample obtained in oxygen atmosphere, and the crushing rate is slightly improved; the volume density and apparent density of the sample obtained in hydrogen atmosphere are lower than those of the sample obtained in air atmosphere, and the crushing rate is the lowest; the sample obtained in vacuum atmosphere has the smallest volume density and apparent density, but the crushing rate is greatly improved. Considering that practical applications require lower volume density and apparent density, as well as the lowest crushing rate, sintering in hydrogen atmosphere is the optimal condition. Therefore, the present invention can achieve comprehensive utilization of water-based rock cuttings by controlling the sintering atmosphere of water-based rock cuttings.

[0050] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a lightweight and high-strength proppant, characterized in that: The following steps are involved: Step 1, weighing water-based rock cuttings A and water-based rock cuttings B raw materials, ball milling and mixing them evenly, granulating, drying, and making green bodies; Step 2, heat treating the green body under different sintering atmospheres, and cooling to room temperature to obtain a light and high-strength proppant; In step 2, the different sintering atmospheres are air atmosphere, oxygen atmosphere, hydrogen atmosphere or vacuum atmosphere; In the oxygen atmosphere, oxygen with a purity of 99.5% was used, and the oxygen flow rate was 10 L / min; in the hydrogen atmosphere, hydrogen with a purity of 99% was used, and the hydrogen flow rate was 10 L / min; in the vacuum atmosphere, the vacuum degree was 133 Pa; In step 2, the heat treatment is a two-step heat treatment method, firstly, the temperature is raised to 1250 °C at 2 °C / min and sintered for 5 min, then the temperature is lowered to 1200 °C at a cooling rate of 5 °C / min and kept at this temperature for 2 h; The lightweight high-strength proppant comprises, by weight, 100 parts of water-based rock cuttings A and 10 parts of water-based rock cuttings B; the components of the water-based rock cuttings A, by weight, comprise 12.0-14.0 parts of Al2O3, 3.60-3.80 parts of Fe2O3, 0.40-0.60 parts of TiO2, 1.80-2.10 parts of K2O, 0.60-0.80 parts of Na2O, 18.00-19.00 parts of CaO, and 22.60-24.80 parts of MgO; the mass fractions of CaO and MgO in the water-based rock cuttings A are both greater than 10%; The components of water-based rock cuttings B, in parts by mass, include 16.00~18.00 parts of Al2O3, 48.00~52.00 parts of SiO2, 5.00~6.00 parts of Fe2O3, 0.60~0.90 parts of TiO2, 2.00~4.00 parts of K2O, 1.00~2.00 parts of Na2O, 1.80~3.50 parts of CaO, and 2.50~3.60 parts of MgO.

2. The method for preparing a lightweight and high-strength proppant according to claim 1, characterized in that: In step 1, the ball milling speed is 100 r / min; the drying temperature is 80~120 ℃, and the drying time is 4~12 h.

3. A light-weight high-strength proppant prepared from water-based rock cuttings obtained by the method for preparing a light-weight high-strength proppant according to any one of claims 1 to 2, characterized in that: The turbidity of the lightweight and high-strength proppant prepared with water-based rock cuttings is 11~12.

4. The light and high-strength proppant prepared from water-based rock cuttings according to claim 3, characterized in that: The bulk density of the lightweight high-strength proppant is 1.54-1.71 g / cm 3 , apparent density is 2.71~3.12 g / cm 3 .

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