RU2761435C1 - Method for manufacturing a magnesia-silicate proppant and a plasticizing additive for its implementation - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: group of inventions relates to the oil and gas industry, namely to the technology for manufacturing ceramic proppants intended for use as wedging agents in the extraction of oil or gas by hydraulic fracturing (fracking). The method for manufacturing a magnesium silicate proppant includes the production of a raw charge by calcining magnesia silicate rock and its joint grinding with silica raw materials, wet grinding of the raw charge with the introduction of at least one plasticizing and/or modifying additive, granulation and drying of the resulting ceramic mixture, sieving and sintering of granules. In the process of grinding the raw charge, a plasticizing moisturizing additive is introduced in the form of a clay-lignosulfonate suspension in an amount of 13-15, wt.%, of the resulting ceramic mixture, and then during grinding and/or granulation of the resulting ceramic mixture, a dry binding mineral additive is also introduced: a powder of plastic kaolinite clay. The plasticizing suspension contains components in the following ratio, wt.%: clay 15-20, lignosulfonate 5-10, water the rest.

EFFECT: increase in the strength and crack resistance of the proppant.

4 cl, 7 tbl

Description

Technology area

The proposed invention relates to the oil and gas industry, in particular to the technology of manufacturing ceramic proppants intended for use as proppants in oil or gas production by hydraulic fracturing (hydraulic fracturing).

State of the art

A characteristic feature of modern oil production is an increase in the share of hard-to-recover hydrocarbon reserves in the world structure of raw materials, which, in addition to high-viscosity and bituminized oils, also include traditional and so-called shale oils, which require special methods of extraction, treatment and transportation.

Currently, Russia has more than 40% of hard-to-recover oil reserves in reservoirs with low permeability. Every year the share of such reserves is steadily growing, since the reserves of easily-produced oil lying close to the surface are being depleted.

The most common modern method of increasing the productivity of wells in the fields of hard-to-recover oils of low and medium viscosity is the method of hydraulic fracturing (hydraulic fracturing), which cannot be carried out without the use of proppants - ceramic proppants (high-strength granular ceramic materials that can withstand the pressure of the earth formation up to 70-100 MPa and more ), which play a critical role in hydraulic fracturing technology. Their function is to anchor and maintain open the newly created fracture in the earth formation after the gel used to deliver the proppants and create the fracture in the reservoir is destroyed.

Among modern ceramic proppants of industrial production, the most used are aluminosilicate and magnesium silicate proppants, differing in their strength and density characteristics.

Comparative analysis of theoretical information and known practical experience in the creation of ceramic proppants indicates that the use of natural magnesia-silicate raw materials, which are more affordable, allows you to obtain a more competitive ceramic product in terms of price. Moreover, it is possible to manufacture both a dense proppant made entirely of serpentinite asbestos rock and a lightweight proppant made from a mixture of heat-treated serpentinite with quartz-feldspar sand. With regard to magnesium silicate proppants, proppants with an MgO content of 18-28 wt. %.

The main criteria for the selection of proppants for specific reservoir conditions in order to ensure long-term fracture conductivity at the formation depth is their mechanical strength and bulk density. High strength of proppants is necessary to resist the pressure of soil formations, and the density of the material affects the processes of proppant transfer by the fluid (the liquid with which the proppant is delivered to the fracture in the formation) when filling the fractures and the choice of the type of fluid.

Therefore, the main problems in the development of the technology of modern ceramic proppants, regardless of their chemical composition, is to ensure such mutually competing properties of the granular material as its high strength while maintaining low bulk density values, as well as reducing energy consumption in proppant production (reducing grinding time and reducing the fineness grinding of raw materials, lowering the temperatures of thermal preparation of raw materials and firing of granular material) while maintaining the strength of the finished product.

Known technology for the manufacture of proppant, disclosed in the description of the invention according to patent RU 2617853 C1, IPC C09K 8/80, C04B 35/20, C04B 35/64, 04/28/2017 (hereinafter - RU 2617853). This source describes a widely used technological scheme for the manufacture of magnesium silicate proppant, including a combination of dry and wet grinding of the feedstock. At the same time, research has established that the use of wet grinding is the most preferable from the point of view of the stability of the consumer properties of the proppant.

The production of ceramic magnesium silicate proppants using wet grinding includes the following technological conversions:

1) manufacturing of raw materials;

2) wet grinding of the raw material mixture and obtaining a slip;

3) drying the slip in a tower spray dryer to obtain a molding mixture;

4) granulation of the molding mixture to obtain the raw proppant;

5) roasting and sieving granular raw proppant.

The raw material charge is made by mixing serpentinite and quartz-feldspar sand fired at a temperature of 750-1200 ° C (preferably 1150-1160 ° C) and its subsequent preliminary dry grinding, as a rule, to a fraction of less than 80 microns. Slurry preparation is carried out by wet grinding of the raw mixture, as a rule, to a fraction of less than 30 microns (preferably less than 10 microns). During wet grinding, the chemical composition of the material is adjusted by additionally introducing heat-treated serpentinite or quartz-feldspar sand into the mixture, as well as the introduction of plasticizing and modifying additives. The resulting slip is subjected to spray drying in a tower spray dryer (BRS), and the resulting molding mixture (BRS - groats) is fed to granulation. Granular raw proppant is subjected to high-temperature firing, which is performed to maximize compaction and optimize the chemical and phase composition of the ceramic.

We will take this known technology as a prototype of the present invention.

The main problem in obtaining magnesia-silicate proppants from compositions of serpentinites, olivinites and dunites (and their natural mixtures) is the difficulty of sintering granular material based on them. Poor sintering affects the relatively low strength of the ceramic material, especially in the granular state, and also necessitates an increase in the firing temperature, which entails an increase in the energy consumption of the process.

The strength (in a broad sense) of a granular ceramic material depends, in particular, on the degree of internal porosity. The absence of internal porosity and the most dense packing of material grains during the formation of granules increase the strength of the finished product.

The technical objective of the present invention is to create a magnesium silicate proppant with increased strength, including fracture toughness, taking into account the above factor.

The essence of the invention

The proposed invention is aimed at achieving the following technical result: increasing the strength and, in particular, the fracture toughness of the proppant due to the production of granules with a thin layer of viscous glass phase between the crystals, which ensures the shear of the grains between each other under load without destroying the structure of the granule.

The specified technical result is achieved by the directional regulation of the granule formation processes and the activation of the sintering process of a ceramic material of magnesia-silicate composition based on serpentinite, olivinite or dunite and natural siliceous components by moisturizing and plasticizing the raw mixture with a clay-lignosulfonate suspension, as well as by adding during grinding and / or granulation of the obtained plasticized raw material mixture of the dry binder mixture of the mineral additive - the powder of plastic kaolinite clay (clay bond).

The causal relationship between the specified essential features of the invention and the achieved technical result is confirmed by the following.

The reason for the increase in the strength of the proppants made according to the method according to the invention is the improvement of the sinterability of the samples due to:

a) uniform distribution of the moisturizing and plasticizing suspension throughout the entire volume of the raw material,

b) the formation of the thinnest films of plastic clay on particles of calcined serpentinite and silica, contributing to a denser packing of particles in the volume of the formed granule,

c) baking the clay bond and its interaction with the surface of the particles of the raw mixture as a result of the creation of low-melting eutectics in the films by introducing an alkaline and / or alkaline-earth component in the form of a clay-lignosulfonate suspension.

All this together provides, during sintering, the development of a glass-crystalline viscous transition layer with the participation of a clay bond, and, as a consequence, an increase in the strength properties of the granule, since the thinner the interlayer between the elements of the ceramic structure, the higher the specific strength of the ceramic material. Also, due to the fact that the interlayer consists of a viscous glass phase, when a load is applied, viscous deformation occurs without destruction of the structure - such a strength characteristic of the proppant as crack resistance increases.

A method of manufacturing a magnesium silicate proppant and a plasticizing moisturizing additive for its implementation are proposed.

A method for manufacturing a magnesium silicate proppant includes making a raw material mixture by calcining a magnesian silicate rock and grinding it together with a silica raw material, wet grinding the raw material mixture with the introduction of at least one plasticizing and / or modifying additive, granulating and drying the resulting ceramic mixture, screening and sieving.

In this case, according to the invention, in the process of grinding the raw mixture, a plasticizing moisturizing additive is introduced in the form of a clay-lignosulfonate suspension in an amount of 13-15% of the resulting ceramic mixture, and then, during grinding and / or granulation of the resulting ceramic mixture, a dry binder mineral additive is additionally introduced - a powder of plastic kaolinite clay (clay bond).

To implement the method according to the invention, it is proposed to use a plasticizing wetting additive for the manufacture of a proppant in the form of a clay-lignosulfonate suspension. Moreover, according to the invention, the ratio of lignosulfonate and clay in said suspension is in the range of 1: 3-1: 2.

The most effective implementation of the proposed method has the following additional features:

- as a plasticizing moisturizing additive for the raw mixture, a suspension of the composition (wt.%) is used: clay - 15-20, lignosulfonate - 5-10, water - the rest.

- as a binding mineral additive, plastic kaolinite clay with an Al ₂ O ₃ content of at least 28% in the calcined state is used.

Plasticization of the raw mixture is reduced to modifying the state of the particle surface during its processing with a clay-lignosulfonate suspension, followed by mixing with a dry clay binder. This ensures close contact between the moistened non-plastic particles of the raw mixture and the clay binder, which adheres to their surface due to the action of the resinous and sugary substances of the lignosulfonate and is firmly held on it. The formed layers of plastic clay on the particles of the raw mixture help to reduce shear forces during the subsequent granulation of the raw mixture and more dense packing of the particles in the volume of the formed granule. It is allowed to introduce plastic clay at the stage of joint grinding of calcined magnesian silicate rock with silica raw material. The amount of clay binder used depends on the composition of the silica raw material, including the presence of clay particles in them, and is selected for each raw material mixture individually.

A plasticizing moisturizing additive in the form of a clay-lignosulfonate suspension with a density of 1.15-1.18 g / cm ^{3 is} used in an amount of 13-15% of the ceramic mixture. The introduction of a plasticizing moisturizing additive of less than 13% impairs the process of mass granulation and lowers the strength of the raw granules. An increase in the content of the plasticizing moisturizing additive over 15% leads to an increase in the moisture content of the granulated mass over 10%, which causes the danger of granules sticking together and deteriorating their shape (roundness and sphericity).

A plasticizing moisturizing additive in the form of a suspension with a ratio of lignosulfonate and clay in the range of 1: 3-1: 2 allows achieving the required degree of plasticization of the charge and achieving optimal conditions for adhesive interaction with clay binder during granulation of raw grains and obtaining the maximum amount of the target fraction.

Implementation of the invention

The possibility of carrying out the invention is confirmed by an example, as well as by the data and illustrations given in tables 1-7.

An example of implementation of the invention

Serpentinite rock of the Orsko-Khalilovsky deposit (Orenburg region), olivinite of the Kytlymsky deposit and dunite of the Solovyovogorsky deposit (Nizhny Tagil) are used as the magnesium silicate component according to the claimed method.

In terms of mineralogical composition, the Orsk-Khalilovskaya serpentinite rock is composed of serpentine with an admixture of magnesite. The chemical composition in the calcined state is characterized by a high content of magnesium oxide (up to 47 wt.%).

As used tripoli silica component Zikeevskogo deposit (Kaluzhskaya area) flask and diatomaceous rock deposit Inza (Ul'yanovskaya region) the content of SiO ₂ from 87.8 to 91.4% (in the calcined state) in which the prevailing phase is the amorphous silica ( 72-82%) with some impurity of crystalline quartz (up to 15%).

As a natural binder, plastic kaolinite clay of the Novoorsk deposit in the Orenburg region is used, which, in terms of chemical composition, is the main raw material (Al ₂ O ₃ - 32.3% in the calcined state) with an average content of coloring oxides Fe ₂ O ₃ + TiO ₂ (up to 3 , 3% in the calcined state), in terms of mineralogical composition - kaolinite-hydromica clay raw material with a predominance of kaolinite (59%) over hydromica of the illite type (12.5%). The peculiarities of the mineralogical composition of Novoorsk clay determine its technological properties - average plasticity (P-15.7), high cohesion (compressive strength in a dried state - 7 MPa), complete sintering temperature - 1350 ° C.

The characteristics of the raw materials in terms of chemical composition are shown in Table 1 and Table 2.

Preparation of magnesian silicate rock includes calcining at temperatures of 1100-1300 ° C in order to ensure the dehydration of the rock (serpentinite, olivinite and / or dunite), the formation and crystallization of the main crystalline phases - forsterite and enstatite.

Preparation of the raw mixture, consisting of calcined magnesian silicate rock and silica additive, consists in joint fine grinding of both components in a grinding unit to a size at which at least 90% of the particles have a size of less than 20 microns.

The preparation of a natural binder (clay bond) is carried out by drying it in a drying drum to a moisture content of less than 2% and subsequent grinding to a size of less than 0.1 mm.

The preparation of a plasticizing moisturizing additive in the form of a suspension is carried out according to the slip method by joint wet (water - 70 wt.%) Grinding of plastic kaolinite clay (20 wt.%) With the addition of lignosulfonate (10 wt.%) To a size at which not less than 90 % of the particles are less than 20 microns in size.

The dosage of all components is carried out by weight.

According to this method, samples were made with a different composition of components, confirming the achievement of the technical result while observing the quantitative ranges indicated in the claims.

The component compositions of the raw materials are shown in Table 3, and of the ceramic materials - in Table 4.

Plasticization of the prepared raw mixture is carried out by processing it with a prepared clay-lignosulfonate suspension with a density of 1.15-1.18 g / cm ³ in an amount of 13-15 wt. %, providing a ceramic mass with a moisture content of 9-10%.

The preparation of the ceramic mass consists in homogeneous mixing of the prepared binder component (crushed kaolinite clay) with the plasticized raw mixture.

Granulation of the prepared ceramic mixture was carried out in a disc granulator. Then the granules were dried at a temperature of 105-120 ° C and sieved.

The bulk density of the dried granular material is not less than 1.15-1.18 g / cm ³ .

For the obtained dried granules of the 16/20 mesh fraction, the static strength of the raw proppant was measured in accordance with GOST 21560.2, which was 550-750 Pa. Data on the effect of the amount of the plasticizing additive on the strength of the granules are shown in Table 5. Data on the effect of the composition of the plasticizing additive on the strength of the granules and the yield of the target fraction are shown in Table 6.

Firing of a semi-finished product is carried out at a temperature of 1250-1350 ° C.

The bulk density and strength of the granules were determined for the fired proppant according to the generally accepted method ISO 13503-2: 2006 (E).

The properties of the fired proppants are shown in Table 7.

Thus, moistening the raw mixture with a plasticizing clay-lignosulfonate suspension followed by the introduction of a clay binder makes it possible to obtain a magnesia-silicate proppant with an increased mechanical strength at a firing temperature of 1250-1350 ° C. A further increase in the firing temperature leads to the onset of the formation of agglomerates and reduces the percentage of the yield of suitable products.

Table 1 - Chemical composition of the starting components

Component The content of oxides, wt. % SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO K ₂ O Na ₂ O TiO ₂ Δm _prc magnesia-silicate raw materials Orsko-Khalilovskaya serpentinite rock 38.65 0.65 7.24 0.09 37.06 0.01 0.03 0.03 16.17 olivinite of the Kytlym deposit 38.26 0.39 8.47 0.23 47.31 - - - 4.61 dunite solovievogorsky 37.58 0.21 6.28 0.46 42.23 - - - 13.23 silica raw material Inza diatomite 86.44 5.30 1.60 0.74 0.53 - - - 5.39 inzin flask 83.00 5.25 2.72 2.05 1.47 - - - 5.51 trembled 82.41 5.05 2.53 2.04 0.50 1.15 - 6.32 sand 93.45 2.90 0.59 - 0.44 0.31 1.22 0.18 0.91 clay raw materials clay novoorskaya NK-5 56.10 29.25 1.59 0.51 0.68 0.73 0.16 1.42 9.55

Table 2 - Chemical composition of the starting components in the calcined state

Component The content of oxides, wt. % SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO K ₂ O Na ₂ O TiO ₂ magnesia-silicate raw materials Orsko-Khalilovskaya serpentinite rock 46.10 0.78 8.64 0.11 44.21 0.01 0.04 0.04 olivinite of the Kytlym deposit 40.10 0.41 8.88 0.24 49.60 dunite solovievogorsky 43.31 0.24 7.23 0.53 48.67 silica raw material Inza diatomite 91.36 5.60 1.69 0.78 0.54 - - - inzin flask 87.84 5.56 2.89 2.17 1.54 - - - trembled 87.97 5.39 2.70 2.18 0.53 1.23 - sand 94.31 2.93 0.60 - 0.44 0.31 1.23 0.18 clay raw materials clay novoorskaya NK-5 62.02 32.34 1.76 0.56 0.75 0.81 0.19 1.57

Table 3 - Component compositions of raw mixtures,%

Content of components,
wt% Raw mix compositions one 2 3 4 5 6 Outrageous composition Calcined serpentinite 82 81 81 65 Calcined olivinite 73 73 Dunite calcined 76 Sand - - - - - - Diatomite eighteen - - - - 24 35 Trepel - nineteen - 27 - - Flask - - nineteen - 27 -

Table 4 - Component compositions of ceramic mixtures,%

Content of components,
wt% Ceramic mix compositions one 2 3 4 5 6 Outrageous composition Raw mix 75 76 76 77 77 75 73 Clay novoorskaya NK-5 12 eleven eleven 10 10 12 15 Plasticizing moisturizing additive, incl. Clay novoorskaya NK-5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Lignosulfonate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Water 10 10 10 10 10 10 9

Table 5 - Influence of the amount of plasticizing moisturizing additive on the strength of the raw proppant granule

(moisturizing additive composition: clay - 17.5%, lignosulfonate - 7.5%, water - the rest)

The amount of added additive Static strength of granules of various compositions, Pa one 2 3 4 5 6 Moisturizing Supplement 12% 486 517 535 536 541 497 Moisturizing additive 13% 565 581 643 584 589 562 Moisturizing Supplement 14% 686 718 749 723 737 658 Moisturizing Supplement 15% 611 633 652 641 635 561 Moisturizing additive 16% 553 569 581 528 542 503

Table 6 - Influence of the composition of the plasticizing additive on the strength of the granules and the yield of the target fraction of the raw proppant

(raw mix No. 2, amount of moisturizing additive 14%)

The composition of the moisturizing additive
wt% Static strength of granules, Pa Granulometric composition, wt. % clay lignosulfonate water Pass through a 20 mesh sieve Main faction 16/20 Residue on a 16 mesh sieve 10 2.5 87.5 427 33.1 49.4 17.5 15 5 80 693 24.5 56.8 18.7 17.5 7.5 75 718 13.2 68.3 18.5 twenty 10 70 743 12.8 65.1 22.1 25 10 65 761 12.1 52.6 35.3 twenty 15 65 752 20.6 57.9 21.5

Table 7 - Temperature parameters of proppant production and its properties

Property indicators Parameters of heat treatment of raw materials, granules and properties of proppants Firing temperature of pellets, ^о С Compositions one 2 3 4 5 6 Transcendent true density, g / cm ³ Calcining magnesia-silicate raw materials at 1100 ^O WITH 1250 2.33 - 2.34 2.31 - 2.32 2.33 2.32 - 2.33 1300 fraction of broken granules at 7500 psi,% (fr. 30/50) 1300 0.8-1.1 0.7-1.0 0.8 1.5 fraction of broken granules at 10,000 psi,% (fr. 16/20) 1250 17.0 - 17.9 18.1 - 18.6 18.0 19.7 - 19.8 1300 16.8 -17.0 16.6 - 16.8 16.9 19.8 - 19.9 bulk density of granules (fraction 16/20) 1250 1.56 - 1.58 1.55 - 1.56 1.57 1.53 - 1.54 1300 1.56 -1.57 1.57 -1.58 1.59 1.55 -1.56 Calcining magnesia-silicate raw materials at 1300 ^O WITH True density, g / cm ³ 1250 2.35 -2.36 2.33 -2.34 2.35 2.33 - 2.34 1300 Fraction of broken granules at 10,000 psi,% (fr. 16/20) 1250 16.4-16.9 17.1 -17.9 18.0 19.8-20.1 1300 16.2 - 16.4 17.0 -17.3 17.3 19.7 -19.9 Bulk density, g / cm ³ (fr. 16/20) 1250 1.57 -1.59 1.56-1.57 1.58 1.54 - 1.55 1300 1.58 -1.59 1.57 -1.58 1.59 1.55 -1.56

Claims (4)

1. A method for the manufacture of magnesium silicate proppant, including the manufacture of a raw material charge by calcining magnesia silicate rock and its joint grinding with silica raw material, wet grinding of the raw material charge with the introduction of at least one plasticizing and / or modifying additive, granulating and drying the resulting ceramic mixture, granules, characterized in that in the process of grinding the raw charge, a plasticizing moisturizing additive is introduced in the form of a clay-lignosulfonate suspension in an amount of 13-15 wt% of the resulting ceramic mixture, and then a dry binding mineral additive is additionally introduced - a powder of plastic kaolinite clay. 2. The method according to claim 1, characterized in that a plasticizing suspension of the composition (wt.%) Is used as a plasticizing moisturizing additive for a finely ground raw mixture: clay - 15-20, lignosulfonate - 5-10, water - the rest. 3. The method according to claim 1, characterized in that plastic kaolinite clay with an Al ₂ O ₃ content of at least 28% in the calcined state is used as a binder mineral additive. 4. Plasticizing wetting additive for the manufacture of proppant by the method according to claim 1, which is a clay-lignosulfonate suspension, characterized in that the ratio by weight of lignosulfonate and clay in said suspension is in the range of 1: 3-1: 2.