WO2008047253A2 - Agent de soutènement électrofondu, procédé de fabrication et procédé d'utilisation - Google Patents

Agent de soutènement électrofondu, procédé de fabrication et procédé d'utilisation Download PDF

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WO2008047253A2
WO2008047253A2 PCT/IB2007/004331 IB2007004331W WO2008047253A2 WO 2008047253 A2 WO2008047253 A2 WO 2008047253A2 IB 2007004331 W IB2007004331 W IB 2007004331W WO 2008047253 A2 WO2008047253 A2 WO 2008047253A2
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Prior art keywords
proppant
electrofused
pellet
metal oxide
spheres
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PCT/IB2007/004331
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English (en)
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WO2008047253A3 (fr
Inventor
Jean-André Alary
Sebastian Sachse
Thomas Parias
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Imerys
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Priority claimed from US11/465,602 external-priority patent/US7654323B2/en
Application filed by Imerys filed Critical Imerys
Publication of WO2008047253A2 publication Critical patent/WO2008047253A2/fr
Publication of WO2008047253A3 publication Critical patent/WO2008047253A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/60—Compositions for stimulating production by acting on the underground formation
    • C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
    • B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/021—After-treatment of oxides or hydroxides
    • C01F7/027—Treatment involving fusion or vaporisation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/02—Particle morphology depicted by an image obtained by optical microscopy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/90—Other properties not specified above

Definitions

  • the present invention relates to a proppant for fractured earth having a high compressive strength and a good conductivity.
  • Naturally occurring deposits containing oil and natural gas have been located throughout the world. Given the porous and permeable nature of the subterranean structure, it is possible to bore into the earth and set up a well where oil and natural gas are pumped out of the deposit. These wells are large, costly structures that are typically fixed at one location. As is often the case, a well may initially be very productive, with the oil and natural gas being pumpable with relative ease. As the oil or natural gas near the well bore is removed from the deposit, other oil and natural gas may flow to the area near the well bore so that it may be pumped as well.
  • the fractures have a tendency to collapse due to the high compaction pressures experienced at well-depths, which can be more than 20,000 feet.
  • a propping agent also known as a proppant
  • the goal is to be able to remove as much of the injection fluid as possible while leaving the proppant behind to keep the fractures open.
  • proppants must be capable of withstanding high compressive forces, often greater than 10,000 pounds per square inch (“psi"). Proppants able to withstand these forces (e.g., up to and greater than 10,000 psi) are referred to as high strength proppants. In shallower wells, high strength proppants may not be necessary as intermediate strength proppants may suffice. Intermediate strength proppants are typically used where the compressive forces are between 5,000 and 10,000 psi. Still other proppants can be used when the compressive forces are low. For example, sand is often used as a proppant at low compressive forces.
  • the nature of the packing also has an effect on the overall turbulence generated through the fractures. Too much turbulence can increase the flowback of the proppant particles from the fractures toward the well bore. This may undesirably decrease the flow of oil and natural gas, contaminate the well, cause abrasion to the equipment in the well, and increase the production cost as the proppants that flow back toward the well must be removed from the oil and gas.
  • the shape of the proppant has a significant impact on how it packs with other proppant particles and the surrounding area.
  • the shape of the proppant can significantly alter the permeability and conductivity of a proppant pack in a fracture.
  • Different shapes of the same material offer different strengths and resistance to closure stress. It is desirable to engineer the shape of the proppant to provide high strength and a packing tendency that will increase the flow of oil or natural gas. The optimum shape may differ for different depths, closure stresses, geologies of the surrounding earth, and materials to be extracted.
  • Another property that impacts a proppant's utility is how quickly it settles both in the injection fluid and once it is in the fracture.
  • a proppant that quickly settles may not reach the desired propping location in the fracture, resulting in a low level of proppants in the desired fracture locations, such as high or deep enough in the fracture to maximize the presence of the proppant in the pay zone (i.e., the zone in which oil or natural gas flows back to the well). This can reduce the efficiency of the fracturing operation.
  • a proppant disperses equally throughout all portions of the fracture. Gravity works against this ideal, pulling particles toward the bottom of the fracture.
  • proppants with properly engineered densities and shapes may be slow to settle, thereby increasing the functional propped area of the fracture. How quickly a proppant settles is determined in large part by its specific gravity. Engineering the specific gravity of the proppant for various applications is desirable because an optimized specific gravity allows for a proppant to be better placed within the fracture.
  • Still another property to consider for a proppant is its surface texture.
  • a surface texture that enhances, or at least does not inhibit, the conductivity of the oil or gas through the fracture is desirable. Smoother surfaces offer certain advantages over rough surfaces, such as reduced tool wear and a better conductivity, but porous surfaces may still be desirable for some applications where a reduced density may be useful.
  • the primary method of reducing the density of proppants is to replace at least a portion of the higher density alumina with lower density silica.
  • the original bauxite based proppants of the early 1970's contained >80% alumina (Cooke).
  • Subsequent generations of proppants contained an alumina content of >70% (Fitzgibbons), 40% to 60% (Lunghofer), and later 30% to ⁇ 40% (Rumpf, Fitzgibbons).
  • proppants manufactured from high-alumina materials such as bauxite.
  • An embodiment consistent with the present invention is a high strength proppant comprising an electrofused pellet.
  • a high strength proppant comprises a substantially solid and substantially spherical pellet produced by electrofusion of at least one metal oxide.
  • a method of making a proppant is also provided, with that method comprising melting at least one metal oxide in an electrical arc furnace, pouring the molten metal oxide to create a pour stream, and separating the pour stream to form at least one electrofused pellet.
  • a method of fracturing subterranean formations is also provided, with that method comprising injecting a fluid containing at least one electrofused pellet. Description of the Figures
  • Fig. 1 is an image of an exemplary electrofusion process.
  • Fig. 2 is a table containing U.S. standard sieve sizes.
  • Fig. 3a is an image of a sintered spherical proppant.
  • Fig. 3b is an image of an electrofused proppant consistent with the present invention. Description of the Invention
  • a high strength electrofused proppant is found to achieve superior crush resistance, conductivity, and other benefits when used in fracturing subterranean formations surrounding oil and/or gas wells under relatively high closing pressures.
  • a high strength proppant in accordance with one embodiment of the present invention may be a spherical particle prepared by an electrofusion process (hereinafter referred to as an "electrofused sphere" or “electrofused pellet”).
  • an alumina-containing material such as, for example, so-called pure or technical alumina, bauxite, mullite, or a combination of these or any other suitable alumina-containing material may be melted in an electric arc furnace.
  • An example of such a furnace is described below in connection with an exemplary electrofusion process.
  • the metal oxide mixture may be formulated to include at least about 50% alumina by weight. In some embodiments, such as where bauxite is used as an alumina source, it may be desirable to create a molten mixture comprising more than about 90% alumina by weight.
  • the primary source material contains little or no SiO 2 (e.g., pure alumina, meaning alumina that has impurities fewer than about 2% by weight)
  • the addition of SiO 2 may be accomplished either prior to or during the melting stage of the process.
  • the addition of a small amount of SiO 2 has the advantage of improving the viscosity and flowability of the molten mixture, which contributes to achieving a more spherical product than electrofused pellets prepared without SiO 2 , thereby providing improved crush resistance.
  • a mixture with improved flowability also offers a wider range of speeds with which the mixture can be poured, allowing more control over the resultant particle size distribution.
  • those skilled in the art will recognize that adding too much SiO 2 to the mixture can weaken the electrofused spheres, so care must be taken to balance the needs of improved flowability with the final properties of the electrofused product. Consequently, in some embodiments the SiO 2 content of the mixture may be limited to between about 0.3% and about 0.6% by weight.
  • FIG. 1 is an illustration of the bessemehzing process in accordance with one embodiment of the present invention. Near the top of the Figure, the molten mixture is shown being poured from a pouring nozzle 102 to form a steady pour stream 104.
  • a pressure nozzle 106 located, for example, below the pouring nozzle 102, blasts a stream of compressed air directly into pour stream 104, causing the pour stream 104 to disperse into a plurality of spherical droplets 108 and rapidly solidify into spherical particles.
  • FIG. 1 is merely illustrative of the bessemerizing process in accordance with one embodiment of the present invention. Any other suitable variations of this process may be used.
  • the electrofused spheres created from the above bessemerizing process are collected, for example, using a suitable collection tray located below pour stream 104.
  • the collected spheres are then sorted into desirable sizes by any method known to those skilled in the art such as, for example, by centrifugation or sieving according to the dimensions specified in the U.S. Standard Sieve Series commonly used within the art.
  • a Mesh Table showing the commonly used U.S. Standard Sieve Series is shown in FIG. 2.
  • the sieving analysis involves a number of specific steps.
  • sieves of desirable sizes are cleaned to ensure that they are free of loose proppants, resins, or dust.
  • the sieves are then weighed individually and stacked on top of each other inside a base pan with the lowest sieve size (i.e., the one with the largest holes) at the top and the largest sieve size at the bottom.
  • the collected electrofused spheres are separated into batches of about 80 grams and weighed. Each batch is then poured into the top sieve of the stack. A lid is place upon this top sieve and firmly secured in place by an "o" ring. The stack of sieves is placed on a sieve shaker and shaken for about 10 minutes. After shaking, the sieves are individually weighed again along with the spheres that were held by the sieve. The previously recorded sieve weight is subtracted from the total sieve weight with the electrofused spheres to determine the weight of the electrofused spheres at a particular sieve size.
  • the total weight of the electrofused spheres in all sieves is calculated and compared to the initially recorded weight of the electrofused spheres prior to sieving to identify procedural errors. If the weight difference is within an allowable range, such as about 1 %, then the process is considered to be valid and the weight of the electrofused spheres in each sieve is calculated as a percentage of the total weight of electrofused spheres from all the sieves. In this way, the sieving analysis provides an assessment of the percentages of electrofused spheres produced at various sizes in accordance with one embodiment of the present invention.
  • the electrofused spheres for use as proppants are formed to an average diameter of about 0.1 mm to about 3 mm, which corresponds to a mesh size of about 6 to about 140 mesh.
  • the choice of size may depend upon considerations such as the intended fracture depth, the choice of carrier fluid, or other factors known to those skilled in the art.
  • the electrofused spheres may have varying apparent specific gravities. While “specific gravity” is known in the art to refer to the weight per unit volume of a material as compared to the weight per unit volume of water at a given temperature, "apparent specific gravity” as used in this application refers to the weight per unit volume of a material including only the material itself and its internal porosity as compared to the weight per unit volume of water. Thus, in the apparent specific gravity computation, first the weight of the material being measured is determined. Then the volume of the material, including only the volume of the material and its internal pores, is determined. For some materials, this step is easily accomplished by placing the material in water and measuring the volume of the displaced water.
  • Electrofused spheres of the sizes discussed above generally have an associated apparent specific gravity of less than about 3.9.
  • the apparent specific gravity of the electrofused spheres may be limited to between about 3.0 to about 3.9. It may be further desirable to restrict the apparent specific gravity of the electrofused spheres from about 3.4 to about 3.7 in some embodiments.
  • the above electrofused spheres also have an associated bulk density of between about 1.7 g/cm 3 to about 2.7 g/cm 3 . In some embodiments, it may be desirable for the bulk density to be between about 1.9 g/cm 3 and about 2.5 g/cm 3 .
  • Bulk density as used in this application and understood within the art refers to the mass of a particular volume of electrofused spheres divided by the volume occupied by the electrofused spheres where the mass has been compacted. This is sometimes referred to as "packed” or “tapped” bulk density.
  • the measurement method of the "packed” or “tapped” bulk density is that set forth by the Federation of European Producers of Abrasives (FEPA) as standard number 44-D.
  • the volume used for the calculation of bulk density includes both the space between the electrofused spheres and the pore spaces (both interior and exterior) of the electrofused spheres.
  • Crush resistance as used in this application is measured according to procedures promulgated by the API for measuring proppant crush. Specifically, a certain volume of the spherical particles of a given dimension range (e.g., 20/40 mesh) is loaded into a crush cell with a floating piston. For a desired stress level, the piston presses onto the proppant at the required stress level (e.g., 20,000 psi) for a set period of time (e.g., two minutes). The weight percentage of crushed materials, for example, gathered by sieving the fines through a sieve of a desired size (e.g., less than about 1 mm), is measured.
  • required stress level e.g., 20,000 psi
  • thermocouple was inserted into the middle portion of the electrofused sphere collection to record the temperature.
  • a servo-controlled loading ram provided a closing pressure on the proppant between the Ohio sandstone rocks.
  • the test cell was initially set at 8O 0 F. and 1 ,000 psi. The cell was then heated to 25O 0 F. and held for 4 hours before the stress was increased to 2,000 psi over 10 minutes. After 50 hours at 2,000 psi, measurements were made, and then the stress level was raised to 3,000 psi. The same procedures were applied and subsequent measurements were made at 5,000 psi, 7,500 psi, and 10,000 psi over a total of 254 hours.
  • permeability is part of the proportionality constant in Darcy's Law, which relates flow rate and fluid physical properties (e.g., viscosity) to the stress level applied to a pack of electrofused spheres.
  • Permeability is a property specifically relating to a pack of electrofused spheres, not the fluid.
  • Conductivity describes the ease with which fluid moves through pore spaces in a pack of electrofused spheres. Conductivity depends on the intrinsic permeability of an electrofused sphere pack as well as the degree of saturation. In particular, conductivity expresses the amount of fluid that will flow through a cross-sectional area of an electrofused sphere pack under the desired stress level.
  • a 70 mbar full range differential pressure transducer was started. When the differential pressure appeared to be stable, a tared volumetric cylinder was placed at the outlet and a stopwatch was started. The output from the differential pressure transducer was fed to a data collector, which recorded the output every second. Fluid was collected for 5 to 10 minutes after which the flow rate was determined by weighing the collected effluent. The mean value of the differential pressure was retrieved from a multi-meter, as were the peak high and low values. If the difference between the high and low values was greater than 5% of the mean, the data was disregarded. Temperature was recorded at the start and end of the flow test period.
  • Viscosity of the fluid was obtained using the measured temperature and viscosity tables. At least three permeability determinations were made at each stage using Darcy's Law. The standard deviation of the determined permeabilities had to be less than 1 % of the mean value before the test was accepted.
  • a pack of 20/40 mesh electrofused spheres in accordance with one embodiment of the present invention exhibited conductivity of at least about.3,400 md-ft and a permeability of at least about 230 Darcies at a closing pressure of about 5,000 psi.
  • Other embodiments may exhibit conductivities of at least about 4,000 md-ft at 5,000 psi, and permeabilities of at least about 100 Darcies at 5,000 psi, such as 200 Darcies and above.
  • the surprisingly superior conductivity and permeability of the electrofused spheres at that closing pressure may be attributed to the spheres' relatively smooth surface, their superior crush resistance as a result of their high alumina content, and their highly spherical shape that provides an increased void volume over the more irregular spherical proppants of the prior art.
  • the highly spherical shape and substantially smooth surface are particularly advantageous when compared to the sintered spheres that are currently being used in the industry. More specifically, the spheres made from the commonly used sintering method acquire their form from, for example, a dry pelletizing process commonly used in the proppant manufacturing industry (as described in detail in U.S. Pat. No.
  • a mixing device such as an Eirich Mixer having a horizontal or inclined circular table and capable of rotating at a speed of from about 10 to about 60 revolutions per minute is used to mix a ground dry power of the desired base material for forming the pellets.
  • a rotatable impact impeller is provided inside the circular table, which rotates in an opposite direction to the rotational direction of the circular table and causes the material added to the mixer to flow over itself in a countercurrent manner. While the circular table and the impact impeller are both rotating, the dry powder for forming the pellets is continually added until the desired size of unsintered pellets is formed. The pellets are then sintered to cause crystallization and hardening of the base material.
  • Another known method for pelletizing spheres for sintering is a wet method. This method involves preparing an aqueous feed from the desired pellet materials and continuously atomizing the feed into a layer of already partly dried particles made from the same pellet material that is fluidized in a stream of drying air. The formed pellets are continuously retrieved from the layer and separated into desired sizes before sintering.
  • This wet method also produces particles that are of less than ideal sphericity due to uneven contact with dry ingredients and variations in the air stream.
  • Sintered spherical proppants prepared according to the above processes generally have a sphericity of slightly better than 0.7 on the Krumbein scale. An exemplary image of such sintered spheres currently being used in the industry is shown in FIG. 3a. The irregular shapes and rough surfaces of these sintered spheres are apparent.
  • a sintered sphere may satisfy the basic requirements of a proppant, it has a number of draw backs in proppant applications.
  • the less than ideal spherical shape does not facilitate an even distribution of load pressure and creates stress points throughout the proppant pack under high closing pressure. This uneven distribution of stress leads to crushing and the generation of fines.
  • Sintered spheres under pressure break into very minute, dust-like pieces that have a tendency to create densely packed fine layers that significantly reduce both permeability and conductivity. Additionally, the fines tend to have sharp edges, which when in contact with surrounding intact spheres, concentrate the compression forces onto other spheres at the sharp contact points and contribute to the destruction of the surrounding spheres in the proppant pack.
  • electrofusing spheres results in spheres that have been homogeneously cooled from the outside to the inside. Consequently, a radial organization of crystals form toward the center of the sphere, thereby creating a potential radial cleavage plane.
  • electrofused spheres may fail under high compressive forces to result in fines shaped like half-spheres, or slices of spheres. These fines have fewer sharp edges and are less aggressive in their destructive effect on the other spheres in the pack than the fines created when a sintered sphere fails.
  • the electrofused sphere is able to achieve a sphericity of at least about 0.8 on the Krumbein scale. In some embodiments, the electrofused spheres possess a sphericity of at least about 0.9 on the Krumbein scale. It is even possible to make electrofused spheres with a sphericity of more than about 0.95 on the Krumbein scale. This improved sphericity is a direct consequence of the electrofusion process, described above.
  • FIG. 3b An image of exemplary electrofused spheres in accordance with one embodiment of the present invention is shown in FIG. 3b.
  • the electrofused spheres in this Figure are much closer to ideal spheres than the sintered spheres of FIG. 3a. Consequently, the electrofused spheres have a more uniform fit within a proppant pack and distribute load pressure more evenly between individual spheres. This results in less crushing and fewer undesirable fines, along with a larger void volume on average.
  • the electrofusion process starts from a molten liquid as opposed to a mixture of powders that is typically used in preparing sintered spherical proppants. This distinction means that the electrofused proppants can have a smoother exterior, as the smoothness of the prior art proppants is limited by the size of the original powder used to create them.
  • the highly spherical shape and smooth exterior of the electrofused proppant overcome the disadvantages of the prior art.
  • a smooth proppant has a lower coefficient of friction than one having an irregular surface. Accordingly, the fracturing fluid can more easily be removed from the pack, leading to increased conductivity and a lower cost of clean up.
  • a smooth, spherical proppant will also result in increased void spaces in the pack, also aiding conductivity.
  • Yet another advantage is that a smooth spherical proppant will not be nearly as abrasive to well equipment or to the equipment used in the fracturing operation. All of these advantages lead to an increased return on investment through lower clean up costs, higher well up-time, and increased conductivity.
  • the specific surface areas of the electrofused spheres are obtained according to the widely-used BET method (Brunauer, Emmett and Teller) that calculates specific surface area based on adsorption of gaseous molecules, such as nitrogen, on the sphere surface.
  • the electrofused spheres in accordance with one embodiment of the present invention generally acquire a substantially smooth surface measuring between about 0.05 m 2 /g and about 0.5 m 2 /g.
  • electrofused spheres produced using this modified bessemerizing process range between about 0.1 mm and about 5 mm in diameter.
  • Other materials known in the art to absorb large amounts of energy may be used as well to rapidly decrease the temperature and speed solidification to the desired extent to provide a greater percentage of the desired sized sphere, so long as the material does not adversely impact the final product properties.
  • Yet another modification for the production of smaller electrofused spheres involves reducing the flow of the pour stream. With a reduced pour stream, the compressed air may be more effective in causing rapid solidification of individual droplets, thereby resulting in a higher proportion of smaller diameter electrofused spheres. With the reduction of flow, it may be necessary to monitor the viscosity of the flow to ensure that the slower pour does not result in solidification in the pour spout or the casting channel leading up to the pour spout. In some embodiments of the present invention, adoption of one or more of the above modifications may result in as much as up to 100% of the electrofused spheres measuring below about 2 mm in diameter.
  • a mixture of 1 ,000 kg of pure alumina and 4 kg of silica sand was melted in a lidded electrical arc furnace.
  • the electrical arc furnace had a diameter of about 1.8 meters, a power of about 1.2 megawatts, and a voltage of about 172 volts.
  • the arc furnace was tilted and the molten mixture was poured from a pour spout to form a pour stream. Concurrently with the pouring, the pour stream was bessemerized with compressed air through a tube having an air nozzle directed at the pour stream.
  • An air pressure of 8 bars was used, but other suitable pressures can be determined by those skilled in the art.
  • the pressurized air caused individual droplets of the molten mixture to separate and rapidly solidify into spheres.
  • the electrofused spheres were then collected in the bessemehzing chamber with a base comprising water-cooled steel plates.
  • the electrofused spheres were then transported into a cooling tube by an air stream. After sufficient cooling, the electrofused spheres were screened into suitable sizes by sieving as described above.
  • Table 1 shows the physical properties of electrofused spheres that were obtained using the raw materials described above in the examples. It will be understood that these properties are merely illustrative and may vary depending on modifications to the electrofusion process and raw materials.
  • the Vollstaedt grain crushing resistance was measured using the known method involving the computerized testing of individual grain fracture strength, with size and shape analysis of the individual grains.
  • the particular FEPA grit on the Vollstaedt sieve was 35.
  • the pore volume percentage was measured using a combination of optical microscopy and software-controlled digital image analysis. Using various microscopy contrast methods (e.g., bright field), it was possible to distinguish different phases (minerals or pores) by the different gray scales appearing in the image. The software was then able to compute the porosity of the sample.
  • electrofused spheres prepared in accordance with an embodiment of the present invention are well-suited as proppants.
  • the electrofused spheres contain a high percentage of alumina, which is known to improve strength and crush resistance in proppants.
  • the electrofusion of the specific compositions of materials introduces finer pores within the sphere, which allows a better distribution of load within the sphere when under pressure, thereby reducing crushing and the production of undesirable fines.
  • the electrofusion of the specific compositions also creates spheres that are very close to an ideal spherical shape with a smooth surface. Such spheres may have a reduced resistance and may allow for the creation of a more uniform proppant pack, which in turn improves the crush resistance and conductivity of the proppant pack.

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Abstract

L'un mode de réalisation conforme à la présente invention est un agent de soutènement à haute résistance qui comprend une pastille électrofondue. Dans un autre mode de réalisation, un agent de soutènement à haute résistance comprend une pastille sensiblement solide et sensiblement sphérique obtenue par électrofusion d'au moins un oxyde métallique. L'invention concerne également un procédé de fabrication d'un agent de soutènement, ce procédé comprenant la fusion d'au moins un oxyde métallique dans un four à arc électrique, le versement de l'oxyde métallique fondu de manière à créer un courant de versement et la séparation du courant de versement afin de former au moins une pastille électrofondue. L'invention concerne également un procédé de fracturation de formations souterraines, ce procédé comprenant l'injection d'un fluide qui contient au moins une pastille électrofondue.
PCT/IB2007/004331 2006-08-18 2007-08-15 Agent de soutènement électrofondu, procédé de fabrication et procédé d'utilisation WO2008047253A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US11/465,602 US7654323B2 (en) 2005-09-21 2006-08-18 Electrofused proppant, method of manufacture, and method of use
US11/465,602 2006-08-18

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Publication Number Publication Date
WO2008047253A2 true WO2008047253A2 (fr) 2008-04-24
WO2008047253A3 WO2008047253A3 (fr) 2008-10-16

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PCT/IB2007/004331 WO2008047253A2 (fr) 2006-08-18 2007-08-15 Agent de soutènement électrofondu, procédé de fabrication et procédé d'utilisation

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CA (1) CA2597880C (fr)
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1871792A (en) * 1925-03-02 1932-08-16 Aluminum Co Of America Treatment of metallic oxides
US2340194A (en) * 1941-11-14 1944-01-25 Carborundum Co Refractory of insulating material
US3497008A (en) * 1968-03-05 1970-02-24 Exxon Production Research Co Method of propping fractures with ceramic particles
US4068718A (en) * 1975-09-26 1978-01-17 Exxon Production Research Company Hydraulic fracturing method using sintered bauxite propping agent
US4607697A (en) * 1980-11-13 1986-08-26 Societe Europeenne Des Produits Refractaires Propping agent based on zirconia and silica for deep geological fractures
US20040093804A1 (en) * 1999-02-15 2004-05-20 Pem Abrasifs-Refractaires Abrasive grains consisting of polycrystalline alumina

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1871792A (en) * 1925-03-02 1932-08-16 Aluminum Co Of America Treatment of metallic oxides
US2340194A (en) * 1941-11-14 1944-01-25 Carborundum Co Refractory of insulating material
US3497008A (en) * 1968-03-05 1970-02-24 Exxon Production Research Co Method of propping fractures with ceramic particles
US4068718A (en) * 1975-09-26 1978-01-17 Exxon Production Research Company Hydraulic fracturing method using sintered bauxite propping agent
US4607697A (en) * 1980-11-13 1986-08-26 Societe Europeenne Des Produits Refractaires Propping agent based on zirconia and silica for deep geological fractures
US20040093804A1 (en) * 1999-02-15 2004-05-20 Pem Abrasifs-Refractaires Abrasive grains consisting of polycrystalline alumina

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WO2008047253A3 (fr) 2008-10-16
CA2597880C (fr) 2015-02-24
CA2597880A1 (fr) 2008-02-18

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