A compressed air energy storage system may have an accumulator and a thermal storage subsystem having a cold storage chamber for containing a supply of granular heat transfer, a hot storage chamber and at least a first mixing chamber in the gas flow path and having an interior in which the compressed gas contacts the granular heat transfer particles at a mixing pressure that is greater than the cold storage pressure and the hot storage pressure and a conveying system operable to selectably move the granular heat transfer particles from the cold storage chamber, through the first mixing chamber and into the hot storage chamber, and vice versa.

A bund system for the retention of solid or liquid or pourable waste material; bunds of the bund system comprising retaining structures; the retaining structures including at least one vertical structural element relative a base; the base covering a portion of a ground surface; the bunds maintained in a selected position on the ground surface by interaction of the retaining elements with a mass of compacted material.

Also disclosed is a method of forming a waste retention area by enclosing the waste retention area by bunds; the bunds comprising at least one substantially vertical retaining structure relative a base extending over a portion of a ground surface; the method including the steps of; positioning retaining structures on the ground surface to form an enclosed area; horizontal base panels of the retaining structures facing inwards to the enclosed area, welding overlap portions of sealing elements at adjacent vertical and horizontal joints between adjoining retaining structures, placing an impervious liner over the ground surface of the enclosed area, welding edges of the impervious liner to edges of sealing elements at inward edges of the horizontal base panels.

A bund system for the retention of solid or liquid or pourable waste material; bunds of the bund system comprising retaining structures; the retaining structures including at least one vertical structural element relative a base; the base covering a portion of a ground surface; the bunds maintained in a selected position on the ground surface by interaction of the retaining elements with a mass of compacted material.

Also disclosed is a method of forming a waste retention area by enclosing the waste retention area by bunds; the bunds comprising at least one substantially vertical retaining structure relative a base extending over a portion of a ground surface; the method including the steps of; positioning retaining structures on the ground surface to form an enclosed area; horizontal base panels of the retaining structures facing inwards to the enclosed area, welding overlap portions of sealing elements at adjacent vertical and horizontal joints between adjoining retaining structures, placing an impervious liner over the ground surface of the enclosed area, welding edges of the impervious liner to edges of sealing elements at inward edges of the horizontal base panels.

A method for an underground gas storage reservoir management may include obtaining feed from a domestic master gas system. The method further includes simultaneously injecting and reproducing in an underground gas storage via a plurality of dual producer and injector wells. The method further includes enhancing the underground gas storage reservoir management to maximize gas and condensate recovery. The method further includes improving a switching cycle between dual operation modes in the underground gas storage for faster reaction times through a completely segregated injection and reproduction lines.

A method for an underground gas storage reservoir management may include obtaining feed from a domestic master gas system. The method further includes simultaneously injecting and reproducing in an underground gas storage via a plurality of dual producer and injector wells. The method further includes enhancing the underground gas storage reservoir management to maximize gas and condensate recovery. The method further includes improving a switching cycle between dual operation modes in the underground gas storage for faster reaction times through a completely segregated injection and reproduction lines.

A method for increasing CO.sub.2 sequestration efficiency in depleted reservoirs using a CO.sub.2 thickener is provided. The method may include the steps of introducing a thickened CO.sub.2 mixture into the depleted reservoir, where the thickened CO.sub.2 mixture comprises a mixture of CO.sub.2 and a CO.sub.2 thickener. The method may include using CO.sub.2 is in a liquid or supercritical state upon introduction into the depleted reservoir. The method may also include the step of using a CO.sub.2 thickener comprising a methyl acrylate-based copolymer, a CO.sub.2 solvent, and a solvent.

A method for increasing CO.sub.2 sequestration efficiency in depleted reservoirs using a CO.sub.2 thickener is provided. The method may include the steps of introducing a thickened CO.sub.2 mixture into the depleted reservoir, where the thickened CO.sub.2 mixture comprises a mixture of CO.sub.2 and a CO.sub.2 thickener. The method may include using CO.sub.2 is in a liquid or supercritical state upon introduction into the depleted reservoir. The method may also include the step of using a CO.sub.2 thickener comprising a methyl acrylate-based copolymer, a CO.sub.2 solvent, and a solvent.

Methods and systems for treating tailings at an elevated pH using lime are disclosed herein. In some embodiments, the method comprises (i) providing a tailings stream comprising bicarbonates and a pH less than 9.0, (ii) adding a coagulant comprising calcium hydroxide to the tailings stream to form a mixture having a pH of at least 11.5 and a soluble calcium level no more than 800 mg/L, and (iii) dewatering the mixture to produce a product having a solids content of at least 40% by weight. In some embodiments, the pH and soluble calcium level of the mixture cause chemical modification of clay materials of the mixture via pozzolanic reactions. In some embodiments, the undrained shear strength of the product increases over a period of time of at least two days.

A method for operating a kerogen-rich unconventional gas reservoir characterized by there being multiple hydraulically-fractured wells drilled thereinto comprises: recovering a methane-containing gas from a first hydraulically-fractured well drilled into the gas reservoir, steam-methane reforming the recovered methane-containing gas to yield a hydrogen gas and an inorganic carbon-containing gas, injecting at least a portion of the hydrogen gas into a second hydraulically-fractured well drilled into the gas reservoir, and injecting at least a portion of the inorganic carbon-containing gas into a third hydraulically-fractured well drilled into the gas reservoir.

A method for operating a kerogen-rich unconventional gas reservoir characterized by there being multiple hydraulically-fractured wells drilled thereinto comprises: recovering a methane-containing gas from a first hydraulically-fractured well drilled into the gas reservoir, steam-methane reforming the recovered methane-containing gas to yield a hydrogen gas and an inorganic carbon-containing gas, injecting at least a portion of the hydrogen gas into a second hydraulically-fractured well drilled into the gas reservoir, and injecting at least a portion of the inorganic carbon-containing gas into a third hydraulically-fractured well drilled into the gas reservoir.