Casings for use in a system for fracturing rock within a bore

A casing for an explosive unit for use in fracturing a geologic formation around a bore, the casing comprising:

• a tubular body having a first longitudinal end portion, a second longitudinal end portion, radial outer surface, and a radial inner surface;
• first and second end caps secured to the first and second longitudinal end portions of the tubular body, such that the casing defines an internal region configured to contain an explosive material;
• wherein the internal region is filled with explosive material that contacts the radial inner surface of the tubular body;
• and
• wherein, upon detonation of the explosive material within the casing within a bore in a geologic formation, the casing is configured to fracture or decompose to release explosive energy into the geologic formation without substantially limiting the permeability of the bore and the geologic formation around the bore;
• wherein the tubular body comprises stress concentrations such that the tubular body is configured to fragment into a plurality of smaller pieces upon detonation of explosive material within the casing, wherein the stress concentrations comprise grooves in the outer surface of the tubular body, and wherein the grooves comprise longitudinally extending grooves and circumferentially extending grooves that intersect one another, or the grooves comprise helically extending grooves.

A method of decreasing the adherence of casing material to the wall of a fractured bore that is fractured upon detonation of explosive materials within casings positioned within the bore, the method comprising:

• configuring the casings of a material that decomposes in response to detonation of the explosive material, configuring the casings with stress concentrations at selected regions of the casings, or both;
• lowering the casings into the bore;
• and
• with the explosive materials filling the casings and contacting radial side walls of the casings, at least partially decomposing the casings, at least partially fragmenting the casings at the regions of the stress concentrations, or both, in response to detonation of the explosive materials;
• wherein the act of configuring the casings with stress concentrations at selected regions of the casings comprises providing one or both of:
• (a) a pattern of grooves in a surface of walls of the casings;
• and (b) a pattern of thin and thick casing wall sections in an exterior wall of the casings.

A system comprising:

• a plurality of casings coupled together in longitudinal alignment, the casings configured for containing explosive material for detonation to fracture rock in a bore into which the plurality of coupled together casings have been inserted;
• the casings each comprising an elongated body comprising a cylindrical side wall having a longitudinal length and a circumferential dimension and a radial thickness, and upper and lower end caps at longitudinal ends of the side wall, the side wall having an interior surface configured to contact an explosive material contained by the side wall and an exterior surface facing a radial wall of the bore, and the side wall comprising a casing material;
• the side walls of the casings being configured so as to prevent a substantially continuous and substantially impermeable coating of the radial wall of the bore by the casing material upon detonation of the explosive material contained within the side walls;
• and
• wherein each casing side wall comprises stress concentrations positioned such that the side wall is configured to fragment into a plurality of smaller pieces upon detonation of explosive material within the casing, wherein the casing bodies comprise a plurality of thick portions and a plurality of thin portions, and wherein the thin portions comprise recessed pockets in the wall of the side wall.

A casing for an explosive unit for use in fracturing a geologic formation around a bore, the casing comprising:

• a tubular body having a first longitudinal end portion, a second longitudinal end portion, radial outer surface, and a radial inner surface;
• first and second end caps secured to the first and second longitudinal end portions of the tubular body, such that the casing defines an internal region configured to contain an explosive material;
• wherein the internal region is filled with explosive material that contacts the radial inner surface of the tubular body;
• and
• wherein, upon detonation of the explosive material within the casing within a bore in a geologic formation, the casing is configured to fracture or decompose to release explosive energy into the geologic formation without substantially limiting the permeability of the bore and the geologic formation around the bore;
• and
• wherein the tubular body comprises stress concentrations such that the tubular body is configured to fragment into a plurality of smaller pieces upon detonation of explosive material within the casing, wherein the tubular body comprises a plurality of thick portions and a plurality of thin portions, and wherein the thin portions comprise recessed pockets in the wall of the body.