RU2739158C1 - Method for producing proppant - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to proppants—propping agents used in production of oil and gas by hydraulic fracturing. Method includes preparation of charge containing heating of bauxite to temperature from 900 to 1,300 °C. Second component of the charge is unfired low-melting clay in amount of 15 wt % of charge weight. It is naturally dried until moisture content is no more than 5 %. Components of the mixture are ground to obtain particle size of up to 50 mcm, granulated with addition of 0.5 % aqueous solution of carboxymethyl cellulose. Before annealing, the formed granules are dried for 30 minutes at temperature of 200 °C, and annealing is carried out at temperatures from 1,100 to 1,500 °C. Finished proppant is sorted by fractions.

EFFECT: technical result of invention is reduction of power consumption and reduction of granulation time.

1 cl, 1 dwg, 4 ex, 2 tbl

Description

The invention relates to the creation of proppants - proppants, which are used in oil and gas production by hydraulic fracturing.

Hydraulic fracturing is a method of oil and gas production that can significantly increase well productivity. The essence of the hydraulic fracturing method consists in pumping a viscous fluid under high pressure into oil and gas reservoirs, which leads to the formation of cracks in the reservoir, into which the fluid penetrates. To keep the fractures in an open state, mechanically strong proppants that do not interact with the well fluid are introduced into them, which, penetrating with the liquid into the fracture and partially filling it, create a strong proppant framework that is permeable to oil and gas released from the formation. Proppants - artificially created granules must resist not only high formation pressure, which tends to deform proppant particles, which leads to the inevitable closure of the fracture, but also withstand the action of an aggressive downhole environment (moisture, acid gases, salt solutions) at high temperatures. When the proppant particles are destroyed under the action of the wellbore environment, the fracture also closes with an inevitable decrease in the well flow rate. Proppants are produced commercially by processing raw materials such as bauxite. Quartz sand, kaolin, aluminum and zirconium oxides, various aluminosilicate raw materials, etc. were used as starting materials for the production of proppants, depending on the conditions of their use (in addition to bauxite).

There are known ways to obtain proppants:

- proppants are obtained from bauxite calcined at 1000 ° C (US patent No. 4668645);

- proppants are obtained from a mixture of bauxite and kaolin to impart plasticity to the initial mass, which improves the sphericity and roundness of the obtained proppants (US patent No. 4879181);

- proppants are obtained using a special firing mode from kaolin containing 30.0-42.5 wt. % aluminum oxide (RF patent No. 2140874);

Known US Patent No. 6,632,527, which proposes composite proppants consisting of a filler, a binder and covered with a surface film.

Known proppants with a synthetic hydrophobic coating that prevents watering of wells, for example, RF patent No. 2180397.

The closest in terms of the totality of features to this invention (prototype) is RF patent No. 2392295 "Proppant and a method for its production." The method includes preparing a charge containing heating bauxite at a temperature of 650-1450 ° C to carry out the process of its calcination, drying a material containing hygroscopic moisture to remove moisture, grinding these components of the charge in a ball mill to obtain a particle size of up to 5 microns, joint granulation of the components of the charge into the presence of a binder, drying the resulting granules at a temperature of 150-600 ° C, followed by their firing at 1000-1550 ° C.

The disadvantage of the prototype is the difficulty of granulating the proppant from the crushed raw materials and the high consumption of the adhesive binder, for which, in particular, carboxymethyl cellulose (CMC) is used.

The problem to be solved by the claimed invention is a general reduction in energy costs for the production of proppants, in particular, at the stage of the granulation process (by significantly reducing the time of the granulation process), as well as reducing the cost of an adhesive binder while maintaining the performance of proppants.

This result is achieved by the fact that the proppant manufacturing method includes preparation of a charge containing heating bauxite at a temperature of 900-1300 ° C, which ensures the implementation of the process of its calcination and drying of the second component of the charge (low-melting clay) containing hygroscopic (bound) moisture, grinding these components of the charge in a ball mill, joint granulation of the charge components in the presence of a binder (aqueous solution of carboxymethyl cellulose), drying the resulting granules at a temperature of 200 ° C, followed by their firing at 1100-1500 ° C. The finished proppant is sorted into fractions.

Unlike the prototype, in the present invention, bauxite is heated at a temperature of 900-1300 ° C. The second component of the charge is used unfired low-melting clay in the amount of 15.0 wt. % of the batch weight, while drying it is carried out in a natural way to a moisture content of no more than 5%, the components of the batch are crushed to obtain a particle size of up to 50 microns, and with the joint granulation of the batch components, the amount of binder is reduced by adding dried to a moisture content of no more than 5% unbaked low-melting clay. The resulting granules are dried at a temperature of 200 ° C, followed by firing at 1100-1500 ° C.

The typical chemical composition of clays, which are widespread and used in industry, is shown in Table 1.

Low-melting clay is the most widespread and cheapest and has the best plastic properties, which favorably affects the granulation process. It is fusible clay that is used in the invention.

The addition of unfired low-melting clay to the composition of the raw material during granulation improves the rolling of the proppant to the formation of a spherical shape of granules of the required size, while the speed of granulation increases, the consumption of an adhesive binder, for example, carboxymethyl cellulose, decreases. This effect is achieved due to the presence of cohesive water in the clay, which provides its additional plastic properties, which lead to the formation of rolling centers (seeds) of the granules, which improves the proppant granulation process and reduces the granulation time. Bound moisture (or bound water) is capillary moisture chemically bound at the molecular level. This type of moisture differs in that drying of the material does not naturally lead to its release. Removal of cohesive water requires high-temperature exposure (calcination), or treatment with microwave or ultrasound, which leads to the removal of cohesive water and the addition of such material does not lead to the required technical result. Thus, the addition of clay should be carried out after its natural drying and grinding, without additional effects on it.

To test the possibility of replacing a part of an expensive binder (aqueous solution of carboxymethyl cellulose) with low-melting clay, four samples of raw proppant granules were made (the granules were not subjected to final firing in order to determine their strength after the granulation stage.

Sample 1

To obtain proppants, low-melting clay grades (Table 1) and bauxite were used as the starting material. For example, bauxite containing (wt%): Al2O3 - 67.0-73.0; SiO2 15.5-19.0; Fe2O3 - 1.0-2.9; TiO2 - 2.7-4.5; Cao + MgO - 0.5-1.0; R2O - 0.9-1.1, which was previously fired at a temperature of 900-1300 ° C. Since clay can contain hygroscopic moisture, it was dried naturally to a moisture content of no more than 5%. Fired bauxite and dried clay, in the amount of 5 mass. % by weight of the charge, (proportion 95: 5) was jointly ground in a ball mill to a content of particles with an average size of not more than 50 microns. The co-milling mixture was loaded into a mixer granulator. The mixture was granulated while adding a binder. An aqueous solution of carboxymethyl cellulose was used as a binder. At the same time, the concentration of the binder solution was reduced from 3% to 2%.

The resulting granules were dried at 200 ° C.

Sample 2

To obtain proppants, low-melting clay grades (Table 1) and bauxite were used as the starting material. For example, bauxite containing (wt%): Al2O3 - 67.0-73.0; SiO2 15.5-19.0; Fe2O3 - 1.0-2.9; TiO2 - 2.7-4.5; Cao + MgO - 0.5-1.0; R2O - 0.9-1.1, which was previously fired at a temperature of 900-1300 ° C. Since clay can contain hygroscopic moisture, it was dried naturally to a moisture content of no more than 5%. Fired bauxite and dried clay, in the amount of 10 mass. % by weight of the charge, (proportion 90:10) was jointly ground in a ball mill to a content of particles with an average size of not more than 50 microns. The co-milling mixture was loaded into a mixer granulator. The mixture was granulated while adding a binder. An aqueous solution of carboxymethyl cellulose was used as a binder. At the same time, the concentration of the binder solution was reduced from 2% to 1%.

The resulting granules were dried at 200 ° C.

Sample 3

To obtain proppants, low-melting clay grades (Table 1) and bauxite were used as a starting material. For example, bauxite containing (wt%): Al2O3 - 67.0-73.0; SiO2 15.5-19.0; Fe2O3 - 1.0-2.9; TiO2 - 2.7-4.5; Cao + MgO - 0.5-1.0; R2O - 0.9-1.1, which was previously fired at a temperature of 900-1300 ° C. Since clay can contain hygroscopic moisture, it was dried naturally to a moisture content of no more than 5%. Fired bauxite and dried clay, in the amount of 15 mass. % by weight of the charge, (proportion 85:15) was jointly ground in a ball mill to a content of particles with an average size of not more than 50 microns. The co-milling mixture was loaded into a mixer granulator. The mixture was granulated while adding a binder.

An aqueous solution of carboxymethyl cellulose was used as a binder. At the same time, the concentration of the binder solution was reduced from 1% to 0.5%.

The resulting granules were dried at 200 ° C.

Sample 4

To obtain proppants, low-melting clay grades (Table 1) and bauxite were used as the starting material. For example, bauxite containing (wt%): Al2O3 - 67.0-73.0; SiO2 15.5-19.0; Fe2O3 - 1.0-2.9; TiO2 - 2.7-4.5; Cao + MgO - 0.5-1.0; R2O - 0.9-1.1, which was previously fired at a temperature of 900-1300 ° C. Since clay can contain hygroscopic moisture, it was dried naturally to a moisture content of no more than 5%. Fired bauxite and dried clay, in an amount of 20 mass. % by weight of the charge, (proportion 80:20) was jointly ground in a ball mill to a content of particles with an average size of not more than 50 microns. The co-milling mixture was loaded into a mixer granulator. The mixture was granulated while adding a binder. An aqueous solution of carboxymethyl cellulose was used as a binder. The concentration of the binder solution was taken at 0.5%.

The resulting granules were dried at 200 ° C.

The samples obtained in the examples were tested for strength for various fractions (see table 2). The method for determining crushing resistance was used (GOST R 51761-2013 Aluminosilicate proppants. Specifications, p. 8.9).

Table 2 shows that the optimal value is the addition of 15 mass. % low-melting clay with a simultaneous decrease in the amount of a binder solution of carboxymethylcellulose from 3% to 0.5%.

In general, the proppant manufacturing method according to this invention is illustrated by a brief flow diagram of a proppant production line (Fig. 1):

1. Prepared the charge: bauxite 1 was heated to a temperature of 900 to 1300 ° C for the process of calcination of bauxite and added in an amount of 15.0 wt. % unfired naturally dried low-melting clay 2, which contains cohesive moisture at a level of no more than 5%.

2. Dry raw materials were ground to the required fineness in a ball mill 3 (for example, D1200 × 3000 produced by NPO Sibprommash, Russia) to a particle size of up to 50 microns.

3. Added a binder (0.5% aqueous solution of carbomethylcellulose (for example, corresponding to TU 2231-034-07507908-2001)) using a dispenser 4.

4. The crushed mixture was granulated in a disc-type mixer-granulator 5 (for example, OT-150 manufactured by OOO Phoenix, Russia).

5. Before final firing, the granules were dried at 200 ° C for 30 minutes.

6. Produced the final firing of the pellets in furnace 7 at temperatures from 1100 to 1500 ° C.

7. Made the final sorting of the granules through a sieve 8 into fractions and storage in warehouse 9.

The specified method provides a reduction in granulation time, energy savings and a decrease in the consumption of liquid binder (carbomethylcellulose).

Claims (1)

A method for producing a proppant, including preparing a charge containing heating bauxite, ensuring the process of its calcination, drying the second component of the charge, grinding these components of the charge in a ball mill, joint granulation of the charge components in the presence of a binder in the form of an aqueous solution of carboxymethyl cellulose, drying the resulting granules, followed by by firing them, sorting the finished proppant into fractions, characterized in that bauxite is heated to a temperature of 900 to 1300 ° C, the second component of the charge is used unfired low-melting clay in an amount of 15 wt.% of the charge weight, it is dried naturally to a moisture content of no more 5%, the components of the charge are crushed to obtain a particle size of up to 50 μm, granulated with the addition of a 0.5% aqueous solution of carboxymethyl cellulose, before firing, the resulting granules are dried for 30 minutes at a temperature of 200 ° C, and firing is carried out at temperatures from 1100 to 1500 ° FROM.

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