Terratek, Inc.

Arfon H Jones

Sidney J Green

Raymond Ashton Cutler

Ahmed S Abou-Sayed

Henri Samuel Swolfs

The present invention embodies an improved method for the in situ mining of low to impermeable minerals to sweep out sections of deposits beneath the surface of the earth. Practicing the method of the invention generally involves: locating, by exploration at depth, a mineral deposit suitable for in situ mining and drilling a well bore into that deposit; hydraulically fracturing that well bore utilizing a disintegrating solution to break up aggregate bonding, fully opening the formation, and, at the time of fracturing, by ground surface stress changes determining the principal fracture direction; from the determined fracture direction, locating at least one production well bore appropriately alongside the first well bore and fracturing that production well bore using a disintegrating solution, which solution, optionally, includes proppants therein; passing a leaching solution flow between the well bore and production well bore to dissolve appropriate minerals from the deposit; and drawing out, preferably through the production well bore, the pregnant leaching solution for further refining above ground.

Process for solution mining

Hollow, fine-grained ceramic proppants are less expensive and improve fracture control when compared to conventional proppants (dense alumina, mullite, bauxite, zirconia, etc.). Hollow proppants of the present invention have been fabricated by spray drying, followed by sintering in order to obtain a dense case and a hollow core. These proppants generally have high sphericity and roundness (Krumbein sphericity and roundness greater than 0.8), have diameters on average between 2250 and 125 .mu.m, depending on proppant size required, and have strength equal to or greater than that of sand. The hollow core, the size of which can be controlled, permits better fracture control in hydraulic fracturing treatments since the proppant can be transported in lower viscosity fluids. Hollow proppants produced at the same cost/weight as conventional proppants also provide for lower costs, since less weight is required to fill the same volume. The fine-grained (preferably less than 5 .mu.m in diameter) ceramic case provides the strength necessary to withstand closure stresses and prevent crushing.

Hollow proppants and a process for their manufacture

The present invention relates to a method for measuring the fracture toughness of rock as it would exhibit in its natural down-hole setting. Practicing the method of the present invention involves internally pressurizing a rock specimen while simultaneously exerting an increasing external horizontal stress thereon, raising simultaneously the internal pressure to maintain a desired relationship of exterior to interior pressures until the specimen fractures, which pressure, in relationship to the stress intensity factor and specimen geometry, provides the specimen fracture toughness as it would exist in a down-hole situation.

Process for measuring the fracture toughness of rock under simulated

This is an invention in a method for locating the azimuthal direction of fractures induced into an underground formation adjacent to a well bore. Practicing the method of the invention involves measurement of stresses created at or near ground surface by such fracture propagation, utilizing pressure sensitive devices making up stress meters which reflect those stress changes on standard pressure gauges. Such stress meters are preferably each placed at an optimum distance from a well bore and spaced therearound, and, when a fracture is induced in the formation around the well bore, preferably by hydraulic means, said stress meters measure surface stress changes as horizontal pressure changes, which pressure change measurements can then be used to mathematically determine the direction of the fracture.

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Salt Lake City, UT, United States of America

Arfon H Jones