MX2014004760A - Porous proppants. - Google Patents

Abstract

Ceramic ultra-lightweight porous proppants can be cost-effective for use in hydraulic fracturing operations. Silicon carbide and silicon nitride can advantageously provide a high degree of strength while having sufficient porosity to remain lightweight and facilitate fluid transport. Oxycarbides and oxynitrides of silicon are also suitable lightweight proppant materials. In one aspect, a porous proppant has a generally spherical shape with a particle diameter between 100 and 2,000 microns, median pore sizes between 1 and 50 microns, and a porosity between 10 and 70% of the total spherical volume. For a plurality of porous proppants, each porous proppant individually can form a proppant pack.

Description

POROUS POINTERS PRIORITY CLAIM This request claims priority to the provisional request of E.U.A. No. 61 / 549,878, entitled "Porous Planter" and filed on October 21, 2011, which is incorporated for reference in its entirety.

TECHNICAL FIELD This invention discloses porous props for use in hydraulic fracturing, and methods of fabrication and use thereof.

BACKGROUND OF THE INVENTION Hydraulic fracturing, or fracking, is a common stimulation technique used to increase the production of fluids from underground formations. In a typical hydraulic fracturing treatment, fracturing the treatment fluid containing a proppant material is injected into the formation at a pressure sufficiently high enough to cause the formation or elongation of the fractures in the reservoir. Proppant material remains in the fracture after completing the treatment, where it serves to keep the fracture open, thereby increasing the ability of the fluids to migrate from the formation to the perforation through the fracture.

Many different materials have been used as proppant including sand, glass beads, walnut shells and metal shot. Sand-based sills are commonly used due to the low cost of sand. However, these proppants often can not be used in the depths where pressures are greater than approximately 2500 psi. The relatively recent increase in the use of hydraulic ramming, often referred to as hydraulic fracturing, has presented a need for proppants that have improved crushing forces.

Many hydraulic fracturing wells in depths greater than a few hundred feet and can subject proppant materials to pressures in excess of 10,000 psi. Therefore, strengthening coatings on sand and sintered ceramic proppant have been used to achieve greater crushing forces.

Two important proppant properties are crushing strength and density. High crushing force may be desirable for use in deeper fractures where pressures are greater, eg, greater than approximately 2500 psi. As the relative strength of several materials increases, so they also have the respective particle densities. Tarpings that have higher densities may be more expensive to use, for example due to transportation costs. Accordingly, there is a need for ultra-lightweight proppant having increased crushing force.

BRIEF DESCRIPTION OF THE INVENTION Porous ultra-light ceramic tiles can be cost effective for use in hydraulic fracturing operations. Silicon carbide and silicon nitride can advantageously provide a high degree of strength while having sufficient porosity to remain light and facilitate fluid transport. Oxicarbides and silicon oxynitrides are also suitable light propping materials.

In one aspect, a porous proppant has a generally spherical shape with a particle diameter between 100 and 2,000 microns, average pore sizes between 1 and 50 microns, and a porosity between 10 and 70% of the total spherical volume.

For a plurality of porous proppant, each porous proppant can individually form a proppant pack having a crushing force of at least 2,000 psi and an apparent specific gravity of 1.0 g / cc or less; a crushing force of at least 4,000 psi and an apparent specific gravity of 1.3 g / cc or less; a crushing force of at least 6,000 psi and an apparent specific gravity of 1.6 g / cc or less; a crushing force of at least 8,000 psi and an apparent specific gravity of 1.8 g / cc or less; a crushing force of at least 10,000 psi and an apparent specific gravity of 2.0 g / cc or less; or a crushing force of at least 12,000 psi and an apparent specific gravity of 2.2 g / cc or less.

For a plurality of porous proppant, each porous proppant can individually form a proppant pack that produces 10% or less of fines in a trituration test.

The porous particles can include silicon carbide, silicon nitride or a combination thereof. The porous particles may include 90% or more of silicon carbide. The porous particles may have a sphericity of 0.91 or greater, or 0.95 or greater. The porous particles may have a roundness of 0.91 or greater, or 0.95 or greater.

In another aspect, a composition includes a plurality of particles including silicon carbide, silicon nitride or a combination thereof, forming a porous proppant having a generally spherical with a particle diameter between 100 and 2,000 microns, average pore sizes between 1 and 50 microns and a porosity between 10 and 70% of the total spherical volume.

For a plurality of compositions, each porous proppant can individually form a pack of proppant having a crushing force of at least 2,000 psi and an apparent specific gravity of 1.0 g / cc or less; a crushing force of at least 4,000 psi and an apparent specific gravity of 1.3 g / cc or less; a crushing force of at least 6,000 psi and an apparent specific gravity of 1.6 g / cc or less; a crushing force of at least 8,000 psi and an apparent specific gravity of 1.8 g / cc or less; a crushing force of at least 10,000 psi and an apparent specific gravity of 2.0 g / cc or less; or a crushing force of at least 12,000 psi and an apparent specific gravity of 2.2 g / cc or less.

For a plurality of compositions, each porous proppant can individually form a pack of proppant that produces 10% or less fines in a crushing test.

In the composition, the particles may have a sphericity of 0.91 or greater, or 0.95 or greater. The particles may have a roundness of 0.91 or greater, or 0.95 or greater.

In another aspect, a method of using a composition of claim 15, which comprises injecting the composition into a hydrofracture.

In another aspect, a method of making a porous proppant includes heating a composition that includes a carbon source and a silicon source between 10 and 70% porosity of the total proppant volume thereby forming a carbide proppant. porous silicon.

The porous silicon carbide proppant can have a particle diameter of between 100 and 2,000 microns, average pore sizes between 1 and 50 microns, and a porosity between 10 and 70% of the total spherical volume.

Other aspects, modalities and characteristics will be apparent from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1-2 are SEM images of a porous proppant.

Figures 3A-3B show results of short-term conductivity and permeability test of porous proppant.

Figures 4A-4B show results of long-term conductivity and permeability test of a porous proppant.

DETAILED DESCRIPTION OF THE INVENTION Two important physical attributes of proppant packages - packet strength and packet porosity - depend on many factors. Proppant density is also an important attribute. These three important attributes strongly influence the overall performance of the well's conductivity. Although there are many factors that determine the resistance to compression, porosity and density to achieve total conductivity, they can be categorized into four levels of importance.

The first and most important level (the objective) is conductivity. This determines the performance of the well. Permeability and other related flow terminology are associated with conductivity. It is well known that the strength and porosity of the proppant package are primary factors in the determination of conductivity. Accordingly, proppants provide increased well performance, for example, proppants that have strength and / or increased porosity, are desirable.

The second level of importance is combined strength and porosity. A proppant package must be strong in compression and do not produce fines that will plug the pores of the proppant package in the well. When the proppers are crushed they produce small fractions called fines that can reduce the performance of the well. Therefore porous, strong proppant packs are more desirable for conductivity.

A third level of importance is the proppant density. Although the density does not affect the conductivity once a proppant package is in place, a less dense proppant can be supplied in the well before being installed. Lighter runners flow with water, brine or other fluid media to allow deeper penetration into the well.

Fourth level attributes that contribute to important attributes of a higher level include, but are not limited to: composition of the primary material; composition of secondary material; choke size of the composite grains of the primary material with itself or secondary composition; Sintered grain size of the composition of the primary material; volume of porosity - total volume in proppant; pore size; pore shape; open vs closed pores; sphericity / roundness; proppant particle size (eg sphere diameter); proppant particle size distribution; nature of the size distribution (for example, single-mode, bimodal, or other size distribution).

While many variables determine overall performance, the combined properties of strength and Porosity mainly influence conductivity. A desirable proppant is one that has low density yet with high compressive force.

The failure mode of proppant packs typically involves the fracturing of individual proppers, under well-forming pressure, thus producing the smallest (fine) proppant particles. The clogging failure mode results from fines produced from crushing performance of the proppant at poorer conductivity when finer products are produced.

With reference to Figure 1, a porous proppant is generally indicated by the numeral 100. Porous stalk 100 may generally be spherical, ovoid, elongate, cylindrical or other, including an irregular shape. For example, the porous proppant can be spherical and has a Krumbein sphericity of less than about 0.5, at least 0.6 or at least 0.7, at least 0.8 or at least 0.9, and / or a roundness of at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8 or at least 0.9. The term "spherical" can refer to the roundness and sphericity in the Krumbein and Sloss graph by visually classifying 10 to 20 randomly selected particles. Sphericity and roundness of at least .9 is more desirable to achieve greater strength at lower densities.

Porous stanchion 100 can be formed from any suitable oxide, carbide, or silicon nitride, boron, aluminum, zirconium, iron, titanium, zinc, tin, chromium, manganese, magnesium or calcium. For example, the porous proppant of a silicon carbide, a silicon nitride, a silicon oxide, an aluminum oxide, a boron carbide or a combination thereof can be formed. In some cases, the porous proppant 100 may be composed of at least 90% of the silicon carbide, at least 95% of silicon carbide, at least 98% of the silicon carbide, or at least 99% of the silicon carbide. . In some cases, porous proppant 100 may be composed of at least 90% silicon nitride, at least 95% silicon nitride, at least 98% silicon nitride, or at least 99% silicon nitride. . Porous bolster 100 can have a diameter ranging from about 1 miera to about 3,000 microns, for example, between about 100 and 2,000 microns. In some embodiments, porous proppant 100 has a diameter of approximately 500 microns.

The average pore sizes of the porous proppant can be between, for example, about 1 miera and about 50 microns, and the porosity can represent about 10% to about 70% of the total spherical volume. Pore sizes can be adapted in size and volume to achieve different crushing forces for different well formations.

The porous proppant can have a crushing force greater than 10,000 psi with a specific gravity of less than 2.2 g / cc. The porous proppant may have a crushing force greater than 11,000 psi, greater than 12,000 psi, or higher. The porous proppant can have a specific gravity of less than 2.0 g / cc, less than 1.8 g / cc, less than 1.6 g / cc, less than 1.5 g / cc or less than 1.4 g / cc, or less. The porous proppant desirably combines the properties of high crushing strength and low density. For example, porous proppant can have a crushing force greater than 10,000 psi with a specific gravity of less than 2.2 g / cc; a crushing force greater than 11,000 psi with a specific gravity of less than 2.0 g / cc; a crushing force greater than 12,000 psi with a specific gravity of less than 1.8 g / cc; or even higher crushing forces combined with even smaller specific gravities.

Figure 2 shows a proppant with higher magnification than Figure 1. porous proppant 100 has a scaffold 110 that form heterogeneous pore structure of bars 120. The scaffold 110 imparts increased strength for proppant and proppant 100 can resist crushing forces over 12.000 psi.

In addition, pores 120 offer permeability so that, once injected in a hydrofracture, the released fluid can pass through the pores of the proppant as well as around the spaces formed by the packing of the particles. Non-porous fasteners, or those proppant modified with external surface treatments, are limited in the extraction of fluid as the fluid can only pass through the tortuous path created by the packing of the particles. Thus, porous proppant can greatly increase the amount of fluid extracted and also extracts the fluid faster than the proppant currently used.

Porous bolster 100 can be formed by reduction of silicon and carbon based materials, for example, to provide a porous proppant of silicon carbide. In one embodiment, a carbon source is reacted with a silicon source to form a porous silicon carbide by controlling the reaction to avoid densification. Alternatively, the pores can be formed during a sintering process. Template creation approaches can also be used to form pores.

A suitable carbon source can be derived from charcoal. Other suitable carbon sources include graphite or carbon black.

In some embodiments, a carbon source is combined with a source of silicon (such as a silicon dioxide, eg, silica or sand) and reduced in the presence of reducing agents to produce silicon carbide. The porosity resulting from oxygen degassing can impart porosity to the resulting silicon carbide. Silicon carbide powder can also be sintered without pressure to produce porous proppant. Reaction binding is another process that can be used to produce porous proppant. Any suitable method can be used to process a solid material into spherical particles, such as, for example, grinding, spray drying, spheronization, encapsulation, granulation or extrusion. In most embodiments, spherical particles are desirable. For example, the porous non-sintered source may have a Krumbien sphericity of 0.8 or higher, 0.9 or higher, 0.95 or higher, 0.98 or higher, or 0.99 or higher.

Sintering can be performed using any suitable method of heating a silicon carbide source, or a carbon source and a silicon source, including, for example, resistance, radiation, convection, induction, plasma, laser, microwave or other methods. Additional sintering aids can optionally be included, such as a polymeric binder or binders organic The measurement of the sintering can be controlled by adjusting the temperature and duration. In a first phase of formation of a porous proppant, a reduction step of a carbon source and a silicon dioxide produces a porous silicon carbide. Therefore, a particulate carbon carbon source can produce particulate porous silicon carbide. In a second optional phase of formation a porous proppant, sintering particulate particulate silicon carbide particles can produce a controllable degree of fusion. Therefore, "choking" can occur between the porous silicon carbide particles, that is, the formation of bridges that bind porous silicon carbide particles. The bridges thus formed are desirably composed of silicon carbide, instead of a silicon oxide, which would result in a weak proppant of similar material with bridges composed of silicon carbide. Amounts of less than 10% of the oxides are preferable in the tightening regions (for example, oxides such as silicon oxide, alumina, zirconia, glass, mullite and other clay bonds) may be acceptable, whereby 90% or more of the porous proppant is composed of silicon carbide or silicon nitride. Boron carbide and boron nitride are also acceptable in the choke region at levels less than 10%. Preferably silicon carbide is bonded to silicon carbide as the region of strangulation.

The throttling process can form a structure that has an additional level of porosity, that is, the porosity formed between the particles that are joined by bridges. Thus the resulting material can have a large-scale porosity (for example, of the order of one miera at 50 microns) between the particles; and porosity on a smaller scale (for example, in the order of less than one miera to 10 microns). Control over this large-scale porosity is achieved by controlling the degree of fusion between the particles. Higher temperatures and increased time promotes a higher degree of fusion. When they are fused to a higher degree, the bridges between the particles become larger and more numerous; Individual particles become less distant and more agglomerated.

Fine of less than 10% may be generally acceptable in crushing tests. 90% or larger original particle sizes should be retained in the sieve during a crushing test procedure. Crushing tests are not a substitute for current well performance or conductivity but are an adequate indicator of propping performance, and for comparisons of different propping materials.

Backward flow is another issue that can result in poor well conductivity performance.

The strength of the proppant pack is not only determined by the compressive strength of the proppant but also how well they stay in the pack. Lower density siding may have negative backward flow problems, then traditional coatings (resins) may be used in the porous props mentioned here to reduce or prevent backward flow articles.

Packed random shoring (similar to similar bulk density packing methods) produces more than 30% by volume to less than 70% by volume of the porous proppant packages. However, this does not include the porosity of the proppant by itself as it only includes the porous volume in the proppant package.

Many attributes and variables determine the porous volume of a proppant package such as packing method, particle size, particle shape and particle distribution. However, these properties combine to form a total package porosity that determines maximum conductivity in conjunction with the strength of the package.

Specific gravity is the density of the material and is also defined as the skeletal density of the porous proppant. The apparent specific gravity is the adjusted proppant density when considering the addition of the pore density with the material density of the proppant.

For example, silicon carbide may have a specific gravity of 3.2 g / cc even if the proppant may have an apparent specific gravity of 1.6 g / cc when considering 50% of the volume of porosity. The term "density" of the proppant here refers to apparent specific gravity, density of volume or any other density term may be used elsewhere.

Sphericity and roundness of at least .9 is more desired to achieve greater strength at lower densities.

Suitable proppant particle sizes are in many cases 20/40 mesh. However, other mesh sizes can perform similar strength and density attribute results.

A mesh size range is determined by retaining all the proppant particles in the smaller mesh screen (such as 40 mesh) and allowing all proppant particles to pass through the larger mesh screen (such as 20 mesh). ).

The following discussion provides an example of the relationship between dense proppant strength and porous package strength.

Solid silicon carbide that has a proppant strength of 540,000 psi can produce 180,000 psi for a single solid sphere, producing then 60,000 psi for a porous proppant pack of non-porous (dense) spheres. The result can decrease less than 10% fines after the crushing test.

Solid spheres made of silicon carbide can be "excessive" for most rock formations since porous silicon carbide produces a lightweight, strong solution compared to sand and sintered ceramics. Starting with the highest levels of compressive strength that allows porous silicon carbide to provide similar strength levels such as sand and ceramics, even at lower desirable densities.

The following discussion provides an example of porous proppant strength in relation to porous package strength.

Given 60,000 psi for 60% porous block, producing 20,000 psi for 60% a single porous sphere, then producing 6,000 psi for a 50% porous proppant package consisting of 60% porous spheres.

Table 1 below shows that silicon carbide is desirable for a lightweight proppant. Boron carbide can also be a good choice for proppant, but it can be cost prohibitive. Only widely available raw materials such as sand, certain clays, carbon, and aluminosilicate forms are acceptable in terms of cost. The conversion of sand and carbon into porous applied carbide is a preferred embodiment for low density, high strength, low cost proppant.

TABLE 1 Material Strength Density Ratio of compressive proppant strength (gram / cc) to density (psi) Silica 165,343 2.6 63,593 Mullite 188,549 2.8 67,339 Alumina 377,098 3.8 99,236 Boron carbide 415,442 2.5 166,177 Silicon carbide 565,647 3.2 176,765 (Compressive strength per g) EXAMPLES EXAMPLE 1 Conductivity and short-term permeability Figure 3A shows the results of a short-term conductivity test using a silicon carbide proppant (diamonds), a commercial sintered bauxite proppant (squares), and a commercially mixed aluminum oxide / silicon oxide proppant (triangles) ). Figure 3B shows the results of short-term permeability tests for the same materials.

EXAMPLE 2 Permeability and long-term conductivity Figure 4A shows the results of a long-term conductivity test using a silicon carbide proppant; Figure 4B shows the results of a long-term permeability test using the same material.

EXAMPLE 3 Force measurements Degree of proppant Force Density% Thin Compressive porous size (gram / cc) generated mesh (psi) 99% SiC p / 1% oxide 5, 000 1.4 9% 30 90% SiC w / 10% mullite 8, 000 1.6 7% 20/40 99% SiC p / 1% oxide 10, 000 1.8 6% 30 98% SiC p / 2% oxide 12,000 2.2 9% 20/40 Other embodiments are within the scope of the following claims.

Claims (29)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. - A porous proppant having a spherical shape generally with a particle diameter between 100 and 2,000 microns, average pore sizes between 1 and 50 microns, and a porosity between 10 and 70% of the total spherical volume.

2. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 2,000 psi and an apparent specific gravity of 1.0 g / cc or less.

3. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 4,000 psi and an apparent specific gravity of 1.3 g / cc or less.

4. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a package of proppant having a crushing force of at least 6,000 psi and an apparent specific gravity of 1.6 g / cc or less.

5. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 8,000 psi and an apparent specific gravity of 1.8 g / cc or less.

6. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 10,000 psi and an apparent specific gravity of 2.0 g / cc or less.

7. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a package of proppant having a crushing force of at least 12,000 psi and an apparent specific gravity of 2.2 g / cc or less.

8. - The plurality of porous proppant according to claim 1, characterized in that each porous proppant individually forms a pack of proppant that produces 10% or less fines in a test of crushing.

9. The porous proppant according to claim 1, characterized in that the porous particles include silicon carbide, silicon nitride or combinations thereof.

10. - The porous proppant according to claim 9, characterized in that the porous particles include 90% or more of silicon carbide.

11. The porous proppant according to claim 1, characterized in that the porous particles have a sphericity of 0.91 or greater.

12. - The porous proppant according to claim 1, characterized in that the porous particles have a roundness of 0.91 or greater.

13. The porous proppant according to claim 1, characterized in that the porous particles have a sphericity of 0.95 or greater.

14. The porous proppant according to claim 1, characterized in that the porous particles have a roundness of 0.95 or greater.

15. A composition comprising a plurality of particles including silicon carbide, silicon nitride, or a combination thereof, which form a porous proppant having a spherical shape generally with a particle diameter between 100 and 2,000 microns, size of average pore between 1 and 50 microns, and a porosity between 10 and 70% of the total spherical volume.

16. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 2,000 psi and an apparent specific gravity of 1.0 g / cc or less.

17. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 4,000 psi and an apparent specific gravity of 1.3 g / cc or less.

18. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 6,000 psi and an apparent specific gravity of 1.6 g / cc or less.

19. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 8,000 psi and an apparent specific gravity of 1.8 g / cc or less.

20. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 10,000 psi and an apparent specific gravity of 2.0 g / cc or less.

21. - The plurality of compositions according to claim 15, characterized in that each porous proppant individually forms a pack of proppant having a crushing force of at least 12,000 psi and an apparent specific gravity of 2.2 g / cc or less.

22. - The composition according to claim 15, characterized in that each porous proppant individually forms a pack of proppant that produces 10% or less fines in a trituration test.

23. - A method for using a composition according to claim 15, comprising injecting the composition in a hydrofracture.

24. - The composition according to claim 15, characterized in that the particles have a sphericity of 0.91 or greater.

25. - The composition according to claim 15, characterized in that the particles have a roundness of 0.91 or greater.

26. - The composition according to claim 15, characterized in that the particles have a sphericity of 0.95 or greater.

27. - The composition according to claim 15, characterized in that the particles have a roundness of 0.95 or greater.

28. A method for making a porous proppant, which comprises heating a composition that includes a carbon source and a silicon source between 10 and 70% porosity of the total proppant volume thereby forming a silicon carbide proppant.

29. The method according to claim 24, characterized in that the porous silicon carbide proppant has a particle diameter between 100 and 2,000 microns, average pore sizes between 1 and 50 microns, and a porosity between 10 and 70% of the volume total spherical