WO2011019688A1

WO2011019688A1 - Low dust extended peroxides

Info

Publication number: WO2011019688A1
Application number: PCT/US2010/044967
Authority: WO
Inventors: Crit E. Nethero; Sri R. Seshadri; Bert Macpherson; Thomas H. Kozel; Leonard H. Palys
Original assignee: Arkema Inc.
Priority date: 2009-08-11
Filing date: 2010-08-10
Publication date: 2011-02-17

Abstract

A low dusting extended peroxide comprises 4 - 60% by weight peroxide and a filler where the peroxide is supported on the filler. The filler comprises 20 - 100% by weight calcium carbonate and optionally silica. The extended peroxide has an angle of repose of 50° or less. A method of making the low dusting extended peroxide comprises mixing the filler material(s) and spraying the peroxide onto the filler material while it is mixing to achieve a uniform distribution of the peroxide on the filler material. A method of using the low dusting extended peroxide may include dispersing the low dusting extended peroxide in water to form an aqueous dispersion and supplying the aqueous dispersion to a fracture fluid comprising a polymer to cause the polymer to decompose.

Description

LOW DUST EXTENDED PEROXIDES FIELD OF THEINVENTION

The invention relates to formulations, methods of making, and methods of using extended peroxides. BACKGROUND OF THE INVENTION

Liquid peroxides have historically been applied to inert fillers to form extended peroxides. This is because the extended peroxides are often more stable and easier to transport than the liquid peroxides. Traditional extended peroxides, however, also typically have had handling problems. In particular, traditional extended peroxides have been extremely dusty (or as is generally known in the industry, have "dusting" problems). While dusting has been an ongoing problem, heightened health and safety standards have brought this issue to the forefront. Yet, low dust extended peroxides have not been seen.

Additionally, traditional extended peroxides have poor flowability, i.e., the material properties do not allow the extended peroxides to flow easily during use or in applications. In other words, some traditional extended peroxides were not free flowing, hi particular, it has been recognized that traditional extended peroxides were unable to have both good flowability and low dusting simultaneously. For instance, if the extended peroxide had improved flowability, it usually exhibited increased dusting. Conversely, when a traditional extended peroxide was shown to have decreased dusting, it had poor flowability.

Also, traditional extended peroxides had difficulty being dispersed in water. While most extended peroxides are used in the polymer (e.g., crosslinking rubber) industries and need only be dispersed within the polymers during processing, some applications also require the peroxides to be readily dispersed in water.

Unfortunately, fillers which fail to disperse within water make it difficult to achieve uniform dispersions. SUMMARY OF THE INVENTION

Compositions of the present invention have been shown to be low dusting, an extremely flowable product, and readily disperse in water. Aspects of the present invention include such compositions, the methods of making the

compositions, and methods of using the extended peroxides.

According to an embodiment of the present invention, a low dusting extended peroxide comprises 4 - 60% by weight peroxide and a filler. The filler comprises 20% by weight or greater calcium carbonate and optionally silica. The peroxide is supported on the filler. The extended peroxide has an angle of repose of 50° or less.

According to another embodiment of the present invention, a low dusting extended peroxide comprises 4 - 60% by weight peroxide and a filler. The peroxide is supported on the filler. The filler comprises 75 - 99% by weight calcium carbonate; 1 - 40% by weight magnesium carbonate; 0 - 50% calcium oxide; and 0 - 6% magnesium oxide. The extended peroxide has an angle of repose of 50° or less.

According to another embodiment of the present invention, a method of making a low dusting extended peroxide comprises mixing a filler material comprising 20% by weight or greater calcium carbonate and optionally silica. 4 - 60% by weight of a peroxide is sprayed onto the filler material while the filler material is mixing to achieve a uniform distribution of the peroxide on the filler material. The extended peroxide has an angle of repose of 50° or less.

According to another embodiment of the present invention, a method of using a low dusting extended peroxide comprises providing a low dusting extended peroxide and dispersing the low dusting extended peroxide in water to form an aqueous dispersion. The method may optionally include supplying the aqueous dispersion to a fracture fluid comprising a polymer to cause the polymer to

decompose. DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention include low dusting extended peroxide compositions, methods of making the compositions, and methods of using the extended peroxides. As used herein, the terms "dust," "dusty," "dustiness," and "dusting" are used interchangeably. The degree of dusting or dustiness of certain materials is generally understood by one skilled in the art. The degree of dusting may be interpreted to mean a quantity of particles which may remain suspended in the air (i.e., are airborne) for some period of time, hi other words, the particles remain in the air for some extended period of time and do not quickly settle. Thus, the degree of dusting may be correlated, for example, to the particle size, density, and makeup of the formulation. The Occupational Safety and Health Association (OSHA) and state agencies set exposure limits based on parts per million (ppm) or mg/m³ (weight per volume) for air contaminants, such as silica. Accordingly, one skilled in the art would be able to ascertain a low dust formulation based on observations or measurements.

As used herein, the terms "ease of dispersion" or "dispersability" are understood to mean the ability of the extended peroxide to disperse in a liquid medium, e.g., water. While the filler materials of the extended peroxide may dissolve in the liquid medium, the peroxide may be uniformly dispersed using suitable means known in the art.

As used herein, the terms "flowability," "flowable," and "free flowing" are used interchangeably. Flowability, in simple terms, is the ability of a granular material or a powder to flow. Factors that influence the flow of a material may include the density of the material (e.g., bulk density), cohesive strength, internal friction, and wall friction. Flowability may be correlated to the angle of repose, i.e., the internal angle between the slope of a conical pile of granular material and the horizontal surface.

As used herein, unless specified otherwise, the values of the constituents or components of the formulation are expressed in weight percent or % by weight of each ingredient in the extended peroxide formulation. According to one aspect of the present invention, a low dusting extended peroxide comprises a peroxide supported on a filler. The peroxides may include any peroxide compositions, such as organic peroxides. Suitable peroxides may include liquid and low melting solid peroxides. As is clear to one skilled in the art, a liquid peroxide is liquid at standard temperature and pressure (STP) and a low melting solid is solid at STP but can be readily melted into liquid phase (i.e., melting at a relatively low temperature). In embodiments of the present invention, the peroxides may be selected to be essentially water insoluble. An essentially water insoluble peroxide will allow the final extended peroxide formulation to be dispersed in water. Thus, it is desirable to select a peroxide that can easily and uniformly disperse in an aqueous solution. Such peroxides may be obtainable from Arkema in Philadelphia, PA under the tradename LUPEROX^®. In particular, the peroxides may include diacyl peroxides, peresters, peroxyketals, diperoxyketals, dialkyl peroxides, hydroperoxides, ketone peroxides, peroxydicarbonates, peroxyesters, and mixtures thereof. In one embodiment, the peroxide may be selected from diacyl peroxides, hydroperoxides, peresters, peroxyketals, dialkyl peroxides, and mixtures thereof. In a preferred embodiment, the peroxide is tert-butyl peroxybenzoate (available as LUPEROX^® P from Arkema).

The peroxide may be present in the formulation in an amount ranging from about 4 - 60 weight percent of the extended peroxide formulation. In another embodiment, the peroxide may be present at a loading of 4 - 13% by weight of the extended peroxide. More particularly, the peroxide maybe present in an amount of 4 - 8 weight percent. The loading of peroxide is used to achieve the desired active oxygen (by weight) of the formulation (i.e., an indication of the peroxide's reactivity). LUPEROX^® P, for example, has a % active oxygen (by weight) of greater than or equal to 8.07. The loading of peroxide may, for instance, be influenced by standards from the Department of Transportation (DOT) for transporting peroxide, hi particular, a lower amount of peroxide, e.g., less than 13% by weight of the formulation, eliminates the DOT transport regulations on the size of the container used. Also, the form of the extended peroxides allows for ease of distribution in a wide variety of climates and conditions. For example, a liquid peroxide could freeze in a cold climate, but the extended peroxides are stable regardless of the environmental conditions (e.g., they will not freeze).

According to an embodiment of the present invention, the low dusting extended peroxide comprises the peroxide supported on a filler. The peroxides may be applied to the filler in neat (i.e., essentially pure) form or dispersed in a liquid phase. In one embodiment, the peroxide is diluted in a solvent or diluent. The solvent may be selected from any suitable solvents as generally known in the art. For example, the solvent may include organic solvents, such as mineral spirits or xylene.

The filler (e.g., also known as a carrier or substrate) may comprise calcium carbonate and optionally silica. Traditional fillers have incorporated both calcium carbonate and silica, but the formulations were generally considered dusty. In particular, previous formulations included a high content of silica to provide for a free flowing product. Embodiments of the present invention, however, have demonstrated both low dusting and increased flowability. Additionally, embodiments of the present invention were found to not lump or clump together, were readily dispersed in water, and maintained their activity. In particular, fillers described herein were selected due to their ability to break down quickly in water and require only a minimal amount of water to do so.

The filler includes calcium carbonate. The calcium carbonate may be a precipitated calcium carbonate (i.e., essentially pure form). For example, a suitable calcium carbonate may have the following product specifications:

Table 1

Alternatively, the calcium carbonate may be calcitic limestone and/or calcific and dolomitic limestone (e.g., in a natural state). Calcium carbonate is a common substance found in rock and shells of marine organisms. Accordingly, as will be understood to one skilled in the art, natural calcium carbonate may comprise other impurities, which may also be considered as part of the calcium carbonate. In an embodiment of the present invention, the calcium carbonate composition is in the form of a granular pellet (i.e., prilled from calcitic limestone and/or calcific and dolomitic limestone). The filler may also include other ingredients such as magnesium carbonate, calcium oxide, magnesium oxide, or a mixture thereof.

Binders and/or coatings may also be employed in the preparation of a pelletized filler. In one aspect of the invention, the binder and/or coating is water-soluble or water- swellable to facilitate rapid dispersion of the extended peroxide when placed in contact with a volume of water. The pellets may, for example, be essentially free of any water-insoluble and non-water swellable binders and coatings. Table 2 shows the different ranges of the possible constituents in one type of pelletized calcium carbonate composition.

TABLE 2

As is evident from Table 2, the pelletized calcium carbonate

composition may also include magnesium carbonate, calcium oxide, and magnesium oxide. The values for the calcium and magnesium include all the different forms (e.g., different oxides) that the calcium and magnesium may take. The weight percent lists ranges for the different constituents for the filler. The preferred range lists particularly suitable amounts of the constituents. Table 2 also lists a moisture content. As will be recognized by one skilled in the art, the amount of moisture is variable based on the environment and conditions. Accordingly, in one embodiment of the present invention, a low dusting extended peroxide comprises 4 - 60% by weight peroxide and a filler. The filler comprises 75 - 99% by weight calcium carbonate; 1 - 40% by weight magnesium carbonate; 0 - 50% by weight calcium oxide; and 0 - 6% by weight magnesium oxide. More particularly, the filler may include 10 - 15% by weight magnesium carbonate; 1 - 5% by weight calcium oxide; and/or 1 - 5% by weight magnesium oxide.

The filler maybe essentially free from silica. "Essentially free from silica" is understood to mean that the filler contains none or only trace amounts of silica (e.g., impurities). In embodiments of the present invention where silica is absent, the peroxide may be present in a lesser amount. Ih particular, the peroxide may be present in an amount of about 4 - 8 weight percent of the formulation. More preferably, the peroxide is present at about 7 - 8 weight percent of the extended peroxide. In an embodiment of the present invention, the formulation comprises about 7.7% peroxide and about 92.3% calcium carbonate. Without wishing to be bound to a particular theory, it is believed that silica absorbs a greater amount of peroxide than calcium carbonate because the peroxide is absorbed throughout the silica (i.e., silica is porous and has a greater surface area) whereas the peroxide only coats the surface of the calcium carbonate (i.e., calcium carbonate is nonporous with a low surface area). The surface area of the calcium carbonate may be about 1 - 20 m²/g. The surface area of the silica may be greater than about 50 m^z/g or about 100 - 300 m²/g. Accordingly, when silica is absent from the formulation, a lesser amount of peroxide may be coated on the calcium carbonate. Thus, in one embodiment of the present invention, a low dusting extended peroxide composition may comprise 4 - 8% by weight peroxide and 92 - 96% by weight calcium carbonate. In embodiments of the present invention where silica is present, the amount of peroxide is not as limited. As discussed above, without wishing to be limited to the theory, it is believed that silica is able to absorb a significant quantity of peroxide, e.g., like a sponge. Moreover, it was found that silica improved the flowability of the resulting extended release peroxide. Silica, however, was also discovered to contribute significantly to the dusting problem. Thus, the amount of silica should also be limited to minimize the dusting effect, but maybe present to enhance flowability. Until the discovery of the formulations of the present invention, however, it was generally believed that a formulation could not have both high flowability and low dusting (i.e., it was a tradeoff of one property for the other). In an embodiment of the present invention, the silica may be present in an amount of up to 35 weight percent, or more preferably 20 weight percent, without causing deleterious dusting effects, hi a preferred embodiment, the silica is present in an amount of 5 weight percent or less. Furthermore, it is envisioned that silica may be substituted for other similar materials, such as carbon black.

Silica or other similar materials of various forms may be used. For example, precipitated, fumed, crystalline or amorphous silica may be used in embodiments of the present invention. The different types of silica were also found to contribute differently to the dusting problem and flowability improvement. In particular, precipitated silica was found to cause less dusting, but also lessen flowability. Fumed silica was found to improve flowability, but also increase dusting. The silica may have a surface area of at least 50m²/g. A fumed silica may have a surface area of at least 150m²/g. In one embodiment of the present invention, the precipitated silica may have the following properties: a particle size of about 0.022 microns and a B.E.T. surface area of about 125-150 m²/g. In another embodiment of the present invention, the fumed silica may have the following properties: a B.E.T. surface area of about 200-450 m²/g, a 325 mesh size (44 microns) with a residue of 0.02% max; a bulk density of: 3.0 lb/ft³ (max); and a pour density of 50 g/1 tap density. The following Table 3 provides product specifications for suitable types of silica.

Table 3

In an embodiment of the present invention, the filler may be essentially free from fumed silica and still result in a low dusting, free flowing formulation, hi another embodiment, both precipitated and fumed silica may be used together in the formulation. However, when both precipitated and fumed silica are used, the fumed silica is typically used in lesser amounts. Thus, in one embodiment of the present invention, a low dusting extended peroxide composition may comprise 4 - 60% by weight peroxide; 20 - 96% by weight calcium carbonate; 1 - 30% by weight precipitated silica, and 0 - 5% by weight fumed silica. In a preferred embodiment, the low dusting extended peroxide may contain silica in a ratio of calcium carbonate/silica of greater than 17/1.

In another embodiment, the composition may include about 10% by weight peroxide, about 85% by weight calcium carbonate, and about 5% by weight silica. More preferably, the formulation may include a weight ratio of

carbonate/silica/fumed silica of about 21/14/1.

The filler may also include other ingredients such as Kaolin clay, non- acidic clays (i.e., water washed clay), silica (various forms— precipitated, crystalline or amorphous, fused), sand, diatomaceous earth, zeolites, and carbon black. The diatomaceous earth or any of the other ingredients may be incorporated into the calcium carbonate filler as part of the pelletized product to be coated with the peroxide. Thus, any of the filler materials may be pelletized prior to incorporation with the peroxide. Other binders and coatings may also be added to the filler, such as guar, functionalized guar, hydroxycellulose, ethylene vinyl alcohols, gelatins(s), polyvinyl alcohol(s), pectin(s), polyacrylamide(s) and co/ter polymers of

polyacrylamide(s), etc. It is preferred that these binders/coatings are at least water soluble or water miscible/swellable. The filler materials may come in a variety of forms, e.g., powder, granular, and pelletized forms. The filler materials may be mixed together to form a powdery mix, a clumpy mix, or the mix may be subsequently pelletized. While particle size is an important factor in minimizing dust in the final extended peroxide composition, the particle size of the constituents is not especially restricted, hi one embodiment, the particle size of a pelletized product is less than 2.38 mm, or more preferably less than 0.853 ram. In particular, the pelletized product particle size may be approximated by the following values shown in Table 4:

TABLE 4

The peroxide is supported on the filler to form the extended peroxide.

The peroxides may be applied using any suitable means to allow the peroxide to uniformly coat and/or absorb onto the filler materials. As will be understood in the art, "supported" will be understood to include a surface coating on the filler/support, incorporation through at least a portion or throughout the entire filler (for example, within the pores of a porous filler), or any other suitable understanding in the art.

The low dusting extended peroxides, according to an embodiment of the present invention, have an angle of repose of 50° or less. The angle of repose is an engineering property of granular materials. When bulk granular materials or powder is poured onto a horizontal surface, a conical pile will form. The angle of repose is generally understood in the art to mean the internal angle between the surface of the pile (e.g., the slope) and the horizontal surface. The maximum angle of a stable slope may be determined by friction, cohesion, and the shape of the particles. It is also related to the density, surface area, and coefficient of friction of the material. Thus, materials with a low angle of repose will form a "flatter" pile (or lesser slope) than a material with a high angle of repose (or a greater slope). The angle of repose is also an indicator of the "flowability" of the material. Accordingly, a more flowable material with have a lower angle of repose whereas a less flowable material will have a greater angle of repose, hi the present invention, it is desirous to obtain a very flowable material, e.g., a high flowability. Thus, the material should have a low angle of repose, hi an embodiment of the present invention, the angle of repose is 50 degrees or less. In a preferred embodiment, the angle of repose is 45 degrees or less or more preferably 40 degrees or less. According to another embodiment of the present invention, a method of making a low dusting extended peroxide comprises mixing a filler material comprising 20% by weight or greater calcium carbonate and optionally silica. If the silica is present, it maybe present in amounts of from 0 - 30% by weight precipitated silica and 0 - 5% by weight fumed silica. 4 - 60% by weight of a peroxide may be sprayed onto the filler material while the filler material is mixing to achieve a uniform distribution of the peroxide on the filler material. The extended peroxide has an angle of repose of 50° or less.

The filler materials may be mixed together using any suitable techniques known in the art. In particular the filler materials may be mixed together using a paddle or ribbon (e.g., helical) mixer. The filler materials may be pre-mixed prior to applying the peroxide or the peroxide may be applied simultaneously while mixing the filler materials. The peroxide is sprayed onto the filler material while the filler material is mixing to achieve a uniform distribution of the peroxide on the filler material. Any suitable techniques may be used to apply the peroxide to the filler materials as long as a uniform distribution of peroxide on the filler occurs.

Once the peroxide is coated onto the filler materials, the mixture may be prilled, pelleted, or granularized. Thus, a pelletized extended peroxide results when the resulting mixture is prilled. Any suitable techniques, as readily known in the art, may be used to prill, pellet, or granularize the extended peroxides. As noted above, the peroxide may come in liquid or low melting solid forms. When the peroxide is a liquid peroxide, it may be directly sprayed or applied to the filler materials. When the peroxide is a low melting solid peroxide, it may first be melted into a liquid form prior to being sprayed on the filler material. However, any suitable techniques may be used to prepare the peroxide and apply it to the filler materials. According to another embodiment of the present invention, a method of using a low dusting extended peroxide comprises providing a low dusting extended peroxide comprising 4 - 60% by weight peroxide, 20% by weight or greater calcium carbonate, 0 - 30% by weight precipitated silica, and 0 - 5% by weight fumed silica wherein the extended peroxide having an angle of repose of 50° or less. Such an extended peroxide may be used as a catalyst in polymerization and crosslinking reactions. In such cases, the extended peroxide may be directly incorporated into the polymerization mix without needing any further processing. For example, the extended peroxide may be added to a polymer using a screw/auger feed without generating dust and without being harmful to the health and safety of the workers.

Additionally, it has been found that low dusting extended peroxides of the present invention may be used in the fracture fluid industry. Hydraulic fracturing and fracture-acidizing are techniques commonly utilized to stimulate the production of oil and gas from subterranean formations of low permeability, hi such treatments, fracture fluids are introduced into the subterranean formation under sufficient pressure to create cracks or fractures in the formation and to also propagate these fractures out into the formation. Generally, the fracture fluids contain entrained proppants, such as sand or sintered bauxite, so that as the fracture fluid seeps into the formation or is backflowed out from the fractures, the fractures close upon the proppants to maintain the fractures in an open state for increased permeability.

In using certain fracture fluids, such as high viscosity aqueous gels, water-hydrocarbon emulsions, or oil-based fluids, the high viscosity of these fracturing fluids should be maintained while the fractures are being created and propagated, as well as to aid in transporting the proppants to the farthest reaches of the fractures. After the proppants have been trapped in the fractures, however, it is desirable that the viscosity of the fracture fluids are quickly reduced to allow the fluids to flow back through the fractures, around the proppants and back into the wellbore. Chemicals utilized to reduce the viscosity of fracturing fluids are commonly called "breakers" or "breaker fluids" and are introduced into the fractures to act immediately upon the fracturing fluids upon contact with the fluids or upon reaching a

predetermined temperature. The peroxides may be used in embodiments of the present invention as such breakers. In order for the peroxides to reach the fracturing fluids, it is desirous that the extended peroxides are first prepared into a suitable form. For instance, the low dusting extended peroxide may be dispersed in water to form an aqueous dispersion. Alternatively, an emulsion may be formed. Any suitable mixing or dispersion techniques may be used to allow the extended peroxide to adequately and uniformly disperse. Solvents, other than water, may also be used, but water is preferred due to its inert nature (e.g., it will not be harmful in end use) and abundance. Suitable quantities of the extended peroxides, as will be recognized in the art. may be added to the water to allow for adequate amounts of peroxide to reach the fracturing fluids while not causing excessive amounts of the filler materials to precipitate out. In the field, the extended peroxide maybe added to an on-site tank of water. Once the extended peroxide is dispersed in water, it maybe supplied to a fracture fluid comprising a polymer to cause the polymer to decompose. By causing the polymer to decompose, the viscosity of the fracture fluid is reduced. Due to the ease of dispersion in water, the peroxides may intimately associate with the polymer causing such decomposition. As will also be understood to one skilled in the art, the extended peroxides may be applied to the fracture fluid at any time deemed appropriate to decompose the polymer and reduce the viscosity of the fracture fluid (e.g.,

decomposition may be activated at a later time). Typical fracture fluids may include high viscosity gelled aqueous fluids and high viscosity water-hydrocarbon emulsions. The polymer(s) contained in or making up the fracture fluids may include polymers, such as cross-linked functional polymers. The high viscosity water-hydrocarbon emulsions may include hydratable polysaccharides, polyacrylamides, polyacrylamide copolymers and polyvinyl alcohol. Hydratable polysaccharides may include galactomannan gums and derivatives thereof, glucomannan gums and derivatives thereof, and cellulose derivatives. Examples of such compounds are guar gum, locust beam gum, karaya gum, sodium

carboxymethylguar. hydroxyethylguar, sodium carboxymethylhydroxyethylguar, hydroxypropylguar, sodium carboxymethylhydroxymethylcellulose, sodium

carboxymethyl-hydroxyethylcellulose, and hydroxyethylcellulose. Accordingly, in an embodiment of the present invention, the polymer in the fracture fluid may include functionalized guar derivatives, guar gum, and mixtures thereof. Additionally, in one embodiment, it is desirable that the polymer is a water soluble and/or a water swellable polymer. Water soluble and water swellable polymers are well known and may be appropriately selected by those skilled in the art.

Thus, the low dusting extended peroxides of the present invention have far-reaching applications from cros slinking polymers to fracture fluid industries. The low dusting extended peroxide formulations have been found to be low dusting while simultaneously maintaining or improving iϊowability. Also, the formulations have been shown to be non-clumping. For applications such as hydraulic fracturing and fracture-acidizing, the extended peroxides have been shown to readily and uniformly disperse in water to allow for easy distribution of the peroxides to the site of the fracture fluids. Additionally, the activity (i.e., active oxygen) of the extended peroxide formulations was also maintained, hi other words, the activity was not compromised as compared to prior high dust versions.

EXAMPLES

The following examples were shown to produce low dusting, free flowing, and easily dispersed extended peroxides. The formulations were made by charging a Marion mixer with the dry, filler ingredients. The mixer was started. As the mixer mixed the dry ingredients, a liquid peroxide was slowly sprayed onto the supports (i.e., filler) using spray nozzles.

The following formulation was prepared including both precipitated and fumed silica and was still found to provide a material that is dustless and free flowing:

LUPEROX P is a peroxide, tert-butyl peroxybenzoate (available from Arkema). The calcium carbonate is calcitic limestone and/or calcitic and dolomitic limestone.

HiSil™ 233 is a precipitated silica available from PPG Industries in Monroeville, PA. Cab-O-Sil^® is a fumed silica available from Cabot Corp. in Tuscola, IL. Additional formulations were prepared as follows;

As described above, the angle of repose indicates the amount of flowability of the material. The internal angle between the surface of the pile (e.g., the slope) and the horizontal surface (e.g., degrees from horizontal) was measured. The degree of dusting was determined based on a test where the formulation was added to ajar. The jar was capped and shaken. The cap was removed and the amount of dusting was quantified on a scale of 1-5 with 1 being none to a low degree of dusting and 5 being a high degree of dusting. Similarly, the ease of dispersion was based on a test where the formulation was added to cold water and shaken. The amount of dispersion within the water was quantified on a scale of 1-5 with 1 being poor dispersion in the water and 5 being excellent dispersion in water. It will be

recognized that an adequate dispersion may result even if some of the formulation precipitates out (especially when the aqueous dispersion is allowed to sit for an extended period of time).

While the degree of dusting and ease of dispersion were qualitatively assessed, it is envisioned that these properties may be measured and quantified. As discussed in more detail below, a test is provided for determining the degree of dusting using the accumulation on a sheet of MYLAR (polyester film). Additionally, the degree of dusting may be quantified based on the particle size and/or density of the resulting extended peroxide (e.g., while in use). Accordingly, a mesh/sieve test could be conducted to determine the amount and/or size of fines which results in a dusty formulation. Similarly, the ease of dispersion may also be quantified, for example, by a light scattering test. Although the tests provided were qualitative, they show that formulations according to embodiments of the present invention do exhibit low dusting, improved flowability, and ease of dispersion.

Formulation 1 was shown to have a slightly reduced dust, but was also slightly less free flowing. There were no caking or clumping problems. Formulation 2 showed lower dust, but was also less free flowing. There was slight caking, but no clumping. Formulation 3 had no dust. The formulation was very grainy with 1/16" to 1/4" crumbs. The formulation was less free flowing and had some slight caking. The small clumps broke easily and the formulation was easily dispersed in water.

Formulation 4 had only a very slight dust. The formulation was free flowing. There was no caking and the soft clumps broke easily. The formulation easily dispersed in water. Formulation 5 similarly had only a very slight dust. The formulation was free flowing. There was no caking and the soft clumps broke easily. The formulation easily dispersed in water. Formulation 6 produced a single large lump of sticky dough and required a lot of hot water to disperse the formulation in water. The comparative example is a very dusty formulation, hi fact, the dust floats in the air and spreads throughout the room. However, the formulation is very free flowing and exhibited no caking or clumping.

Additional formulations were prepared on the following types of pelletized calcium carbonate materials:

These values are the maximum percent weight of the constituents of each of the filler materials.

Extended peroxide formulations were prepared using peroxide loadings in the range of 4-13% peroxide on the above pelletized calcium carbonate materials. All samples were prepared based on 20Og total weight.

An extended peroxide formulation was prepared using 6wt% t-butyl perbenzoate (LUPEROX^® P) on the pelletized calcium carbonate. 192g of North Pacific limestone (pelletized calcium carbonate) was weighed in a wide mouth glass jar. A total of 8g of LUPEROX^® P was added to the limestone in 4g increments. After each 4g increment was added, the glass jar was shaken. A homogeneous, free- flowing, non-dust formulation was obtained.

An extended peroxide formulation was prepared using 7.75wt% t-butyl perbenzoate (LUPEROX^® P) on the pelletized calcium carbonate. 184.5g of North Pacific limestone (pelletized calcium carbonate) was weighed in a wide mouth glass jar. A total of 15.5g of LUPEROX^® P was added to the limestone in 4g increments. After each 4g increment was added, the glass jar was shaken. A homogeneous, free- flowing, non-dust formulation was obtained.

An extended peroxide formulation was prepared using 10wt% t-butyl perbenzoate (LUPEROX^® P) with 5% HiSiI 233 (precipitated synthetic silica from PPG) added to North Pacific Limestone (pelletized calcium carbonate). 17Og of North Pacific Limestone was weighed in a wide mouth glass jar. 1Og of Hi SiI 233 was weighed and added to the North Pacific Limestone. The wide mouth glass jar was shaken until the Hi SiI 233 and North Pacific limestone were mixed well. 2Og of LUPEROX^® P was added to the HiI SiI 233/North Pacific Limestone blend in 4g increments. After each 4g increment was added, the product was shaken. A

homogeneous, free-flowing, non-dust formulation was obtained. The water dispersability of the formulations were evaluated using the following testing in order to determine how fast the North Pacific's Limestone changes from a dry pellet form to a fine powder dispersion in water. The objective was to obtain a 0.1% pure LUPEROX^® P to be added to 200 g of frac fluid (a.k.a. water in this example). Assuming the 10wt% LUPEROX^® P used in the previous example, the calculations are as follows:

20Og water x (0.1/100) = 0.2g pure t-butylperbenzoate (LUPEROX^® P)

0.2g pure t-butylperbenzoate x (10/100) = 2g of pellets @ 10% assay required in 20Og of water. Accordingly, 2g of the 10wt% t-butylperbenzoate pellets were added to

20Og of water. The result was that the pellets instantly broke up without any stirring into a fine powder in the water to form a uniform dispersion of peroxide within the water phase.

As a comparative example, the water dispersability of LUPEROX^® F40 (a commercial calcium carbonate pelletized peroxide grade) was contrasted to the above results. A commercial sample of 40% di(t-butylperoxy)diisopropylbenzene) on 60% precipitated calcium carbonate, sold commercially in a free-flowing pellet form (LUPEROX^® F40), was used. A few pellets were placed into a large glass of water. The pellets retained their original shape and size. The glass of water with the pellets was stirred with a spoon for a few minutes. There was still no change. The pellets were then allowed to soak in the water for over one hour. The pellets still retained their original size and shape. In other words, the commercial calcium carbonate pelletized peroxide grade was not readily dispersible in water.

With respect to dusting, a test was conducted where the amount of dust that accumulated on a piece of MYLAR (e.g., biaxially-oriented polyethylene terephthalate (PET) polyester film) was considered to correlate to the degree of dusting. A piece of MYLAR was first weighed. 20Og samples of the extended peroxides were added to a bag with the same piece of MYLAR. The bag was shaken. The MYLAR was again weighed and compared against its original weight. Any change in weight of the piece of MYLAR indicated the degree of dusting of the given formulation.

For the 7.75wt% t-butyl perbenzoate (LUPEROX^® P) on the pelletized calcium carbonate, the amount of dust accumulated on the MYLAR was 0.00Og. In other words, the formulation was completely non-dusting. For the 1 Owt%

LUPEROX^® P dispersed in a blend of 5wt% HiSiI 233 silica and 85wt% Old Castle Limestone (pelletized calcium carbonate), the amount of dust accumulated on the MYLAR was 0.016g. This would be considered virtually non-dusting.

In comparison, the same dusting test was performed with a 20Og formulation containing LUPEROX^® P peroxide and Mississippi Lime M-όO (a precipitated calcium carbonate powder). For that comparative example, the amount of dust accumulated on the MYLAR was .096g. Thus, the amount of dust was at least six times greater than a formulation according to the invention.

While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.

Claims

What is Claimed:

1. A low dusting extended peroxide comprising:

4 - 60% by weight peroxide; and a filler comprising 20% weight or greater calcium carbonate and optionally silica, wherein the peroxide is supported on the filler; and wherein the low dusting extended peroxide has an angle of repose of 50° or less.

2. A low dusting extended peroxide according to claim 1, wherein the filler is essentially free from silica.

3. A low dusting extended peroxide according to claim 2, wherein the peroxide is present in an amount of 4 - 8 weight percent of the extended peroxide.

4. A low dusting extended peroxide according to claim 1, wherein the silica is present in an amount of up to about 20 weight percent of the extended peroxide.

5. A low dusting extended peroxide according to claim 1, wherein the silica comprises a precipitated silica present in an amount of 1 - 30% by weight of the extended peroxide and a fumed silica present in amount of 0 - 5% by weight of the extended peroxide.

6. A low dusting extended peroxide according to claim 1, wherein the silica is present in a weight ratio of calcium carbonate/silica of greater than 17/1.

7. A low dusting extended peroxide according to claim 1, wherein the peroxide is present at a loading of 4 - 13% by weight of the extended peroxide.

8. A low dusting extended peroxide according to claim 1, wherein the calcium carbonate is in the form of a granular pellet.

9. A low dusting extended peroxide according to claim 1, wherein the peroxide is a liquid or low melting solid peroxide.

10. A low dusting extended peroxide according to claim 1 , wherein the peroxide is diluted in a solvent.

11. A low dusting extended peroxide according to claim 1. wherein the peroxide is selected from the group consisting of diacyl peroxides, peresters, peroxyketals, diperoxyketals, dialkyl peroxides, hydroperoxides, ketone peroxides, peroxydicarbonates, peroxyesters, and mixtures thereof.

12. A low dusting extended peroxide according to claim 1 , wherein the peroxide is selected from the group consisting of diacyl peroxides,

hydroperoxides, peresters, peroxyketals, dialkyl peroxides, and mixtures thereof.

13. A low dusting extended peroxide according to claim 1, wherein the peroxide is t-butylperoxybenzoate.

14. A low dusting extended peroxide according to claim 1, wherein the filler further comprises magnesium carbonate, calcium oxide, magnesium oxide, or a mixture thereof.

15. A low dusting extended peroxide comprising: 4 - 60% by weight peroxide; and a filler comprising:

75 - 99% by weight calcium carbonate;

1 - 40% by weight magnesium carbonate;

0 - 50% calcium oxide; and

0 - 6% magnesium oxide; wherein the peroxide is supported on the filler and the extended peroxide has an angle of repose of 50° or less.

16. A method of making a low dusting extended peroxide comprising: (a) mixing a filler material comprising 20% or greater by weight calcium carbonate and optionally silica; and

(b) spraying 4 - 60% by weight of a peroxide onto the filler material while the filler material is mixing to achieve a uniform distribution of the peroxide on the filler material, wherein the extended peroxide has an angle of repose of 50° or less.

17. A method of making a low dusting extended peroxide according to claim 16, further comprising prilling the resulting mixture from step (b) to achieve a pelletized extended peroxide.

18. A method of making a low dusting extended peroxide according to claim 16, wherein the peroxide is a liquid peroxide.

19. A method of making a low dusting extended peroxide according to claim 16, wherein the peroxide is a low melting solid peroxide which is melted prior to being sprayed on the filler material.

20. A method of using a low dusting extended peroxide comprising:

(a) providing a low dusting extended peroxide comprising 4 - 60% by weight peroxide, 20% by weight or greater calcium carbonate, 0 - 30% by weight precipitated silica, and 0 - 5% by weight filmed silica, wherein the extended peroxide has an angle of repose of 50° or less; and

(b) dispersing the low dusting extended peroxide in water to form an aqueous dispersion.

21. A method of using a low dusting extended peroxide according to claim 20, further comprising:

(c) supplying the aqueous dispersion to a fracture fluid comprising a polymer to cause the polymer to decompose.

22. A method of using a low dusting extended peroxide according to claim 21, wherein the polymer is a water soluble or water swellable polymer.

23. A method of using a low dusting extended peroxide accordingerein the polymer is a functionalized guar derivative or guar gum.