RU2515280C2 - Method of magnesian-quartz proppant production - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil and gas industry, and namely to the manufacturing procedure of ceramic proppants intended to be used as propping agents at production of oil or gas using hydraulic fracturing method. The manufacturing procedure of magnesian-quartz proppants includes treatment of the stock, wet milling, granulating and annealing of granules. Wet milling is made in a ball crusher charged with a mix of metal grinding bodies and grinding bodies made of the stock used for production of magnesian-quartz proppants with the following ratio of charged components, wt %: metal grinding bodies 37-55, mill feed 26-30, magnesian-quartz grinding bodies 37-15, at that coefficient of the crusher charge is equal to 0.48-0.55.

EFFECT: reducing breakability of proppant granules due to improved quality of the stock milling.

3 cl, 1 tbl

Description

The invention relates to the production of ceramic proppants (proppants) of magnesian-quartz composition, intended for use in the oil and gas industry as proppants in hydrocarbon production by hydraulic fracturing.

Proppants are strong spherical granules that hold hydraulic fractures from closing under high pressure and provide the necessary productivity of oil wells by providing a conductive channel in the formation. Various organic and inorganic materials are used as proppants, for example, walnut shells, sand, polymer coated sand, etc. However, due to their microstructural features, ceramic proppants are the most used, since the main technical characteristics are determined by the requirements of ISO 13503-2 : 2006 (E) (granulometric composition, sphericity, roundness, crush resistance, density, acid solubility and turbidity of a proppant-wetting liquid), they are superior other types rasklinivateley used for hydraulic fracturing.

Among ceramic proppants, the most common are aluminosilicate and magnesian-quartz, to a lesser extent, silica proppants are on the market. The technological schemes for the production of ceramic proppants in the vast majority of cases are similar and include the preparation of a mixture (as a rule, mixing pre-crushed initial components in a predetermined ratio or their joint grinding), granulation of the material and high-temperature firing of granules, which is performed to maximize compaction and optimization of chemical and phase composition of ceramics. Crush resistance is one of the most important characteristics determining the consumer properties of proppants. Numerous studies conducted by interested organizations have found that granules obtained from a mixture containing more than 45 wt.% Fractions of less than 5 μm have the minimum destructibility under compressive loads, since it is precisely the fine fractions that ensure the completion of the sintering process. In laboratory conditions, a similar fractional composition is achieved with long-term dry vibration grinding or by sequentially performing first dry and then continuous wet grinding. In the conditions of mass large-scale production, the achievement of such a degree of grinding is impossible without a significant reduction in equipment productivity. In this regard, proppant manufacturers are conducting intensive research aimed at improving the quality of grinding of the initial materials without loss of mill productivity. This problem is especially acute in the production of magnesian-quartz proppants, produced on the basis of physical mixtures of calcined serpentinite and quartz-field sand, since due to the different grinding ability of the components, the charge is difficult to grind together, as a result of which the proppant has insufficiently high strength.

A known method of manufacturing ceramic proppants (proppants) of oil wells (see RF patent No. 2235703) from a magnesium silicate material based on forsterite with a content of the latter 55-80%, which is subsequently crushed, granulated and fired at a temperature of 1150-1350 ° C. This method of manufacturing proppant was implemented at the enterprises of LLC "FORES" (Russia, Yekaterinburg) using dry grinding.

The disadvantage of this method is that the proppants made in this way have insufficiently high strength indicators. This is due to several reasons, including the fact that the content of the fraction of less than 5 microns in the ground mixture does not exceed 35-40 wt.%. As a result, after sintering, the ceramic contains a residual porosity in the range of 5-8 vol.%, Adversely affecting the strength of the material.

The closest in technical essence to the claimed solution is a method of manufacturing products from aluminum slag (RF patent No. 2163227), in which ceramic oil well proppants are obtained from cheaper alumina-containing raw materials. The method includes the following operations: sintering of the feedstock, its grinding, compaction and firing of the obtained granules. Sintering of the feedstock is carried out in an agglomerate at 1360-1650 ° C, and granules are fired at 1180-1350 ° C. Grinding is carried out by wet grinding in a slightly acidic environment at pH 4.5-6.0 to a specific surface of more than 12000 cm ² / g, and the products are compacted by granulation from powders obtained by spray drying of a slip in a tower spray dryer (BRS) in the presence of 0.01 -0.3% hydrophobic surfactant.

The known method of manufacturing proppant was also implemented at the enterprises of LLC "FORES" (Russia, Yekaterinburg) using preliminary dry and final wet grinding. The use of wet grinding to some extent improves the strength characteristics of the proppant, however, the fraction content of less than 5 μm remains not high enough (within 40-45 wt.%), In addition, the content of ground iron sharply increases in the crushed mixture entering the BRS and further to granulation, which, when fired, violates the micro- and macrostructure of ceramics. Both of these factors adversely affect the strength characteristics of the material.

The technical problem to which the claimed invention is directed is to reduce the breakability of the proppant granules by improving the quality of the charge grinding, achieved by increasing the amount of finely dispersed (less than 5 microns) fraction over 50 wt.%, As well as by reducing the total amount of ground iron.

This result is achieved by the fact that in the known method of manufacturing magnesian-quartz proppant, including the preparation of the mixture, dry and wet grinding, granulation and firing of granules, wet grinding is carried out in a ball mill loaded with a mixture of metal and ceramic grinding media, in the following ratio, wt.% :

metal grinding bodies 50-90 ceramic grinding bodies 10-50,

moreover, the ceramic grinding bodies are made of a mixture used in the production of the specified proppant, and the fill factor of the mill is 0.48-0.55. In addition, the size of ceramic grinding media does not exceed the size of metallic grinding media.

The inclusion of a mixture of metal and ceramic grinding media in the mill loading is due to the need to combine impact grinding of the material and its abrasion. Metal grinding bodies provide impact grinding, and ceramic grinding work. Since the used ceramic grinding bodies have a lower density compared to metal, the loading of the wet grinding mill with grinding bodies in the claimed ratio provides a fill factor in the range of 0.48-0.55, as a result of which, when grinding, the charge is completely closed by grinding bodies, and the crushed material contains over 50 wt.% fractions less than 5 microns. The use of a mixture of the same composition as the material to be ground for the manufacture of ceramic grinding bodies does not introduce additional impurities into the mixture, and also reduces the total amount of ground iron, which favorably affects the micro- and macrostructure of sintered ceramics and, ultimately, its strength characteristics. A decrease in the mill fill factor below 0.48 (with the same load of the crushed material) reduces the productivity of the equipment, an increase in the fill factor above 0.55 reduces the grinding intensity and leads to the fact that the material remains underfinished. In addition, it should be noted that replacing a portion of metal grinding media with ceramic reduces the cost of production by reducing the net grinding energy and increasing the life of the grinding equipment. A loading of ceramic grinding media in an amount of less than 10 wt.% Does not provide the required amount of fine fractions, and an increase in the loading of ceramic grinding media over 50 wt.% Leads to the fact that the crushed material contains significant amounts of larger fractions that impair the sintering ability of the ceramic. In order to improve the abrasion effect during grinding, it is preferable that the size of the ceramic grinding media does not exceed the size of the metal.

An example embodiment of the invention.

To conduct the study, a pre-crushed magnesian-quartz charge, which is a physical mixture of calcined serpentinite and quartz-feldspar sand of the following chemical composition, wt.%: MgO - 27.9, SiO ₂ - 58.3, Fe ₂ O ₃ - 8.1, impurities - the rest in the amount of 2.5 tons. For wet grinding, an MSMMP - 17 industrial wet grinding mill was used (diameter 1.7 m, length 2.0 m), into which steel grinding bodies were loaded (diameter 20 mm ) in an amount of 75 wt.% (6 t) and ceramic grinding media (diameter 15-18 mm) made of the above mixture in an amount of 25 wt.% (2 t). The mixture was crushed for 2.5 hours, with a mill rotation speed of 28 rpm. The fractional composition was determined on a crushed charge on a Horiba LA-300 photosedimentograph and fed to granulation and firing. The fired granules of the 20/40 mesh fraction were tested for destructibility according to the requirements of ISO 13503-2: 2006 (E). At the same mill with the same loading and operating parameters, the material was ground with a different ratio of metal and ceramic grinding media. Additionally, the specified charge was milled only with metal grinding bodies (by analogy with Russian patents No. 2163227 and No. 2235703). The research results are presented in the table.

Table No. Mill loading The fractional composition of the crushed mixture, wt.% Mill fill factor Destructibility, wt.% At 10000 psi one Metal grinding bodies - 100%, dry grinding (US Pat. RF No. 2235703) <5 μm -40
5-10 microns -40
10-30 microns -20 0.35 6.0-6.5 2 Metal grinding bodies - 100%, dry + wet grinding (US Pat. RF №2163227) <5 μm -45
5-10 microns -40
10-30 microns -15 0.35 5.0-5.5 3 Metal grinding bodies - 90% Ceramic grinding bodies - 10% dry + wet grinding <5 μm -50
5-10 microns -40
10-30 μm -10 0.48 4,5-5 four Metal grinding bodies - 75% Ceramic grinding bodies - 25% dry + wet grinding <5 μm -55
5-10 microns -40
10-30 microns -5 0.51 4.0-4.5 5 Metal grinding bodies - 50% Ceramic grinding bodies - 50% dry + wet grinding <5 μm -55
5-10 μm -35
10-30 μm -10 0.55 4.0-4.5 6 Metal grinding bodies - 45% Ceramic grinding bodies - 55% dry + wet grinding <5 μm -45
5-10 microns -30
10-30 microns -25 0.58 6.0-6.5 7 Metal grinding bodies - 90% Ceramic grinding bodies - 5% dry + wet grinding <5 μm -45
5-10 microns -40
10-30 microns -15 0.41 5.0-5.5

Analysis of the data in the table shows that magnesian-quartz proppant (examples 3-5) obtained by the claimed method has a higher strength than the known analogues.

Claims (3)

1. A method of manufacturing magnesian-quartz proppant, including the preparation of the mixture, its wet grinding, granulation and firing of granules, characterized in that the wet grinding of the material is carried out in a ball mill loaded with a mixture of metal grinding media and grinding media made from a mixture used to produce the specified magnesian-quartz proppant, in the following ratio of loading components, wt.%:
metal grinding bodies 37-55 ground material 26-30 magnesian-quartz grinding bodies 37-15,
moreover, the fill factor of the mill is 0.48-0.55. 2. The method according to claim 1, characterized in that before wet grinding produce dry grinding of the mixture to a particle size of 50 microns or less. 3. The method according to claim 1, characterized in that the size of the magnesian-quartz grinding media does not exceed the size of the metallic grinding media.