Method of making proppants used in gas or oil extraction

A system of making frac sand having a selected grade from a naturally occurring, mined sand having a SiO2 content of at least about 80 percent and having a particle size range where the maximum particle size is less than about 8.0 mm, said system comprising:

• (a) a device for crushing said mined sand into an intermediate particulate material;
• (b) a device for screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles;
• (c) a blast tube with an outlet to pneumatically abrade said particles and propel said feedstock in a stream under a given pressure from said outlet;
• (d) a fixed target located at a given distance from said outlet of said tube to physically abrade said particles to form an output mass containing abraded particles:
• (e) a controller for repeatedly passing said feedstock through said tube and against said target a number of times or process stages until said particles resulting from said repeatedly abraded output mass is a final output mass having both processed roundness and sphericity values of at least 0.6 and wherein said values are greater than said initial values by at least about 0.10;
• and,
• (f) a grading screen network for screening said final output mass to obtain a frac sand with said selected grade.

A method of making frac sand having a selected grade and improved crush resistance from a naturally occurring, mined sand having a SiO2 content of at least about 80 percent and with a general particle shape classified as between round and angular and having a particle size range where the maximum particle size is less than about 8.0 mm, said method comprising:

• (a) crushing said mined sand into an intermediate particulate material;
• (b) screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles;
• (c) pneumatically abrading said particles by pressurized grain to grain agitation of said particles;
• (d) abrading said particles by crashing said particles against a fixed target under high speed and/or high pressure;
• (e) repeating operations (c) and (d) a number of times or stages until said particles resulting from said repeatedly abraded output mass is a final output mass having both processed roundness and sphericity values of at least 0.6 and wherein said values are greater than said initial values by at least about 0.10;
• and,
• (f) screening said final output mass to obtain a frac sand with said selected grade.

A method of making spherical proppant having a selected grade from a naturally occurring, mined granular mineral having a hardness over 6 Mohs and having a particle size range where the maximum particle size is less than about 8.0 mm, said method comprising:

• (a) crushing said mined mineral into an intermediate particulate material;
• (b) screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles;
• (c) passing said particles of said feedstock through a blast tube with an outlet to pneumatically abrade said particles and propel said feedstock in a stream under a given pressure from said outlet;
• (d) directing said pressurized stream against a fixed target located at a given distance from said outlet to physically abrade said particles to form an output mass containing abraded particles;
• (e) repeating operations (c) and (d) a number of times or process stages until said particles resulting from said repeatedly abraded output mass is a final output mass having both processed roundness and sphericity values of at least 0.6 and wherein said values are greater than said initial values by at least about 0.10;
• and,
• (f) screening said final output mass to obtain a spherical proppant with said selected grade.

A method of making spherical proppant having a selected grade from a mass of compound or clustered particles, each of which has a generally spherical shape, but are clumped together, said method comprising:

• (a) screening said mass into a feedstock;
• (b) passing said particles of said feedstock through a blast tube with an outlet to pneumatically abrade said particles and propel said feedstock in a stream under a given pressure from said outlet;
• (c) directing said pressurized stream against a fixed target located at a given distance from said outlet to physically abrade said particles to form an output mass containing abraded particles;
• (d) repeating operations (b) and (c) a number of times or process stages until said particles resulting said repeatedly abraded output mass is a final output mass having both processed roundness and sphericity values of at least 0.6;
• and,
• (e) screening said final output mass to obtain a spherical proppant with said selected grade.

A method of making spherical proppant having a selected grade from a naturally occurring, mined granular mineral having a hardness over 6 Mohs and having a particle size range where the maximum particle size is less than abut 8.0 mm, said method comprising:

• (a) crushing said mined mineral into an intermediate particulate material;
• (b) screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles;
• (c) abrading said particles by particle-to-particle contact at high velocity and also impinging said particles at high velocity against a metal member;
• (d) performing abrading and impinging actions until said particles constitute a final output mass having both processed roundness and sphericity values greater than about 0.6;
• and,
• (e) screening said final output mass to obtain a spherical proppant with said selected grade.

A method of making a mineral with spherical particles from a naturally occurring, mined granular mineral having a hardness over 6 Mohs and having a particle size range where the maximum particle size is less than about 8.0 mm, said method comprising:

• (a) crushing said mined mineral into an intermediate particulate material;
• (b) screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles is substantially less than 0.6;
• (c) abrading said particles by particle-to-particle contact at high velocity and also impinging said particles at high velocity against a metal member;
• and,
• (d) performing abrading and impinging actions until said particles constitute a final output mass having both processed roundness and sphericity values greater than about 0.6.