CERAMIC PROPPANT AND METHOD FOR PRODUCING SAME

Abstract

The invention relates to a method for producing a ceramic proppant, including a step for preparing an original charge material, involving the grinding of source materials, particularly magnesium-containing materials, and auxiliary materials, thus producing a charge material, granulating the charge material so as to produce granules of a proppant precursor, and firing the granules of proppant precursor, thus producing proppant granules, wherein the method includes a step for pre-firing the magnesium-containing material in a reducing atmosphere. The invention also relates to a ceramic proppant produced via the indicated method.

Claims

1. A method for producing a ceramic proppant, comprising the steps of: a) preparation, including grinding source materials, which contain magnesium-containing material, and auxiliary materials to produce a charge material; b) granulating the charge material to produce proppant precursor granules; and c) firing the proppant precursor granules to produce proppant granules, wherein the method comprises the step of pre-firing the magnesium-containing material in a reducing atmosphere.

2. The method according to claim 1, characterized in that the pre-firing step is carried out before the step a).

3. The method according to claim 1, characterized in that the pre-firing step is carried out at a temperature from about 900? C. to about 1100? C.

4. The method according to claim 1, characterized in that the step a) of preparing the source materials comprises co-grinding the magnesium-containing material and the auxiliary material.

5. The method according to claim 1, characterized in that the step a) of preparing the source materials further comprises mixing the ground source materials with water to form a slurry, drying and grinding the slurry to obtain a charge material.

6. The method according to claim 1, further comprising fractionation of the proppant granules.

7. The method according to claim 1, further comprising drying and fractionation of the proppant precursor granules.

8. The method according to claim 1, characterized in that the reducing atmosphere is the atmosphere with an oxygen content of less than 5 wt %, preferably less than 2-3 wt %.

9. The method according to claim 8, characterized in that the reducing atmosphere during the pre-firing process is provided by introducing a carbon-containing additive selected from the group, which comprises natural gas, coal, charred coal or mixtures thereof.

10. The method according to claim 1, characterized in that the pre-firing step is carried out in shaft furnaces.

11. The method according to claim 1, characterized in that the magnesium-containing material is a material based on a magnesium silicate selected from peridotites, including olivines, dunite, serpentinite.

12. The method according to claim 1, characterized in that firing the magnesium-containing material in the step c) is carried out at a temperature from about 1200? C. to about 1350? C.

13. The method according to claim 1, characterized in that the auxiliary material is represented by silica-containing components, including quartz sand, hydromicaceous and/or montmorillonite clays and refractory clays.

14. The method according to claim 1, characterized in that the charge material contains 45 to 70 wt % of magnesium-containing material.

15. The method according to claim 14, characterized in that the auxiliary materials comprise quartz sand in an amount of 30 to 55 wt % of the charge material weight and clay in an amount from 0 to 10 wt % of the charge material weight.

16. The ceramic proppant is produced by the method according to claim 1.

17. The ceramic proppant according to claim 16, characterized by an enstatite content of 50 to 80 wt % and magnesioferrite content of 4 to 8 wt %.

18. The ceramic proppant according to claim 17, characterized in that the enstatite is clinoenstatite.

19. The ceramic proppant according to claim 17, further comprising magnetite of 0.5 to 2 wt %.

20. The method for treating a subterranean formation, comprising: a) providing the ceramic proppant according to claim 16; b) mixing said ceramic proppant with an operating fluid for hydraulic fracturing of a formation; c) injecting the mixture from the step b) into the subterranean formation.

21. Use of the ceramic proppant according to claim 16 for hydraulic fracturing a subterranean formation.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0061] Further, the invention will be illustrated with the reference to the following non-limiting examples. Test samples of the proppant with dunite and serpentinite, which were used as a source magnesium-containing material and heat-treated in various ways, were obtained and studied.

Comparison Example 1

[0062] Dunite was preliminarily fired in a laboratory furnace at the temperature of 1000? C. in an oxidizing atmosphere, then ground together with quartz sand and fusible clay in the ratio of 48:48:4 weight percent to a size of 40 ?m or less. After that, the obtained material was granulated with a laboratory granulator to a fraction of 1.1-1.7 mm. The material was dried at 120? C., fired at various temperatures and scattered. Qualitative indicators were tested in accordance with the requirements of ISO 13503-2:2006 for crushing resistance (mass fraction of broken granules) at the specific pressure of 10 000 psi and the bulk density was determined. The indicators are given in the Table 1.

Comparison Example 2

[0063] As the magnesium-containing component, dunite was used, which was preliminarily fired at a temperature of 1250-1300? C. in an oxidizing atmosphere in a rotary kiln. The samples were made as in the Example 1.

Comparison Example 3

[0064] As the magnesium-containing component, serpentinite was used, which was preliminarily fired at a temperature of 1250-1300? C. in an oxidizing atmosphere in a rotary kiln. The samples were made as in the Example 1.

Example 4

[0065] As the magnesium-containing component, dunite was used, which was preliminarily fired at a temperature of 950-1050? C. in a reducing atmosphere in a shaft furnace. The samples were made as in the Example 1.

Example 5

[0066] As the magnesium-containing component, dunite was used, which was preliminarily fired at a temperature of 950-1050? C. in a reducing atmosphere in a shaft furnace. The samples were made as in the Example 1 at the ratio of dunite, sand and clay of 65:30:5 weight percent.

TABLE-US-00001 TABLE 1 Crushing Firing Bulk Resistance Temperature Density of at the Pre-firing of the Final Raw Specific Source Charge Constituents, Temperature, Product, Material, Pressure of No. wt % ? C. ? C. g/cm.sup.3 10 000 psi, % Dunite, Laboratory Firing - 48 1000 1300 1.52 18.6 Quartz Sand - 48 1310 1.54 17.6 Fusible Clay - 4 1320 1.57 17.2 1330 1.56 20.1 Dunite in a Rotary Kiln - 48 1250-1300 1280 1.55 20.4 Quartz Sand - 48 1300 1.57 16.1 Fusible Clay - 4 1320 1.57 18.6 Serpentinite - 48 1250-1300 1300 1.49 23.6 in a Rotary Kiln 1310 1.50 20.3 Quartz Sand - 48 1320 1.53 19.5 Fusible Clay - 4 1330 1.56 19.7 1340 1.57 23.5 Dunite in a Shaft Furnace - 48 950-1050 1280 1.55 15.9 Quartz Sand - 48 1300 1.57 15.1 Fusible Clay - 4 1320 1.58 16.7 Dunite in a Shaft Furnace - 65 950-1050 1300 1.58 15.3 Quartz Sand - 30 1320 1.60 14.6 Fusible Clay - 5 1340 1.61 16.2

[0067] As can be seen from the table results, changing the pre-firing modes affects the qualitative indicators of the final product and the preliminary heat treatment in the shaft furnace has made it possible to obtain more durable proppants.

Example 6

[0068] The finished samples were additionally examined to determine the quantitative phase composition by means of the ART 9900 Workstation X-Ray Fluorescence Spectrometer with an integrated diffraction system.

[0069] In the samples from the Examples 1-3, the content of enstatites was 63.8-67.9% and the content of magnesioferrites was 2.4-3.6%. At the same time, magnetites in the amount of 3.1-4.5% are present in the phase composition.

[0070] In the samples from the Examples 4 and 5, the content of enstatites was 66.3% and 74.6% respectively, the content of magnesioferrites was 5.2-5.6%, and the content of magnetite was 0.8-1.5%. The high content of magnesioferrites and the low content of magnetite indicates the more complete reaction on the intrusion of iron into the crystal lattice of enstatite.