A compressed gas energy storage system may include an accumulator for containing a layer of compressed gas atop a layer of liquid. A gas conduit may have an upper end in communication with a gas compressor/expander subsystem and a lower end in communication with accumulator interior for conveying compressed gas into the compressed gas layer of the accumulator when in use. A shaft may have an interior for containing a quantity of a liquid and may be fluidly connectable to a liquid source/sink via a liquid supply conduit. A partition may cover may separate the accumulator interior from the shaft interior. An internal accumulator force may act on the inner surface of the partition and the liquid within the shaft may exert an external counter force on the outer surface of the partition, whereby a net force acting on the partition is less than the accumulator force.

This disclosure relates to a method and a system for sequestering carbon-containing materials in underground wells. An example method includes: obtaining a material comprising a carbon-containing liquid; optionally testing the material for compatibility with an underground well; optionally adjusting a property of the material to improve the compatibility; and providing the material for injection into the underground well.

The disclosure discloses a method for constructing a pumping-injection well of a groundwater reservoir in a dump of an open-pit mine. The pumping-injection well includes a bottom pipe, intermediate pipes, and a top pipe in sequence from bottom to top connected from bottom to top. The method includes: arranging a rubble barrier around the pumping-injection well, and installing the bottom pipe of the pumping-injection well at a designed position of the pumping-injection well as a center of circle; continuing to install an intermediate pipe on the bottom pipe, and pile up a rubble pile; continuing to stack multiple intermediate pipes, and starting the construction of the groundwater reservoir; discarding discarded materials from the open-pit mine to form a dump; continuing to stack intermediate pipes to build an inverted trapezoidal surface sump around the pumping-injection well; and installing the top pipe and a well cover to form a complete pumping-injection well.

Systems for underground energy storage and methods for their construction. Methods include forming a plurality of chambers underground connected to a plurality of multiple flow conduits, the plurality of chambers including an upper chamber and a lower chamber each containing a working fluid, each multiple flow conduit of the plurality of multiple flow conduits comprising an inner tubular segment having a flowbore interior to the inner tubular segment configured to flow the working fluid, and an outer tubular segment containing the inner tubular segment, wherein each multiple flow conduit defines an annulus between the outer tubular segment and the inner tubular segment configured to flow a compressed gas, by drilling a borehole in the earth formation, installing an outer tubular segment in the borehole, cementing the outer tubular segment at a target location, and installing the inner tubular segment inside the outer tubular segment.

Systems for underground energy storage and methods for their construction. Methods include forming a plurality of chambers underground connected to a plurality of multiple flow conduits, the plurality of chambers including an upper chamber and a lower chamber each containing a working fluid, each multiple flow conduit of the plurality of multiple flow conduits comprising an inner tubular segment having a flowbore interior to the inner tubular segment configured to flow the working fluid, and an outer tubular segment containing the inner tubular segment, wherein each multiple flow conduit defines an annulus between the outer tubular segment and the inner tubular segment configured to flow a compressed gas, by drilling a borehole in the earth formation, installing an outer tubular segment in the borehole, cementing the outer tubular segment at a target location, and installing the inner tubular segment inside the outer tubular segment.

A flow control assembly including a subassembly including an annular safety valve, a shroud, a bushing connecting the shroud to the subassembly at one of two opposing ends of the shroud, and another bushing connecting the shroud to the subassembly at the other of the two opposing ends of the shroud. The method for operating a hydrogen storage and production system including pumping hydrogen into the salt cavern for storage through a borehole and producing hydrogen from the salt cavern through the same borehole.

A flow control assembly including a subassembly including an annular safety valve, a shroud, a bushing connecting the shroud to the subassembly at one of two opposing ends of the shroud, and another bushing connecting the shroud to the subassembly at the other of the two opposing ends of the shroud. The method for operating a hydrogen storage and production system including pumping hydrogen into the salt cavern for storage through a borehole and producing hydrogen from the salt cavern through the same borehole.

A method and a system for sequestering carbon dioxide (CO.sub.2) while producing freshwater are provided. An exemplary method includes producing saline water from a saline aquifer, desalinating at least a portion of the saline water, producing freshwater and waste brine, mixing waste CO.sub.2 with the waste brine forming a brine/CO.sub.2 mixture, and injecting the brine/CO.sub.2 mixture into the saline aquifer.

A method and a system for sequestering carbon dioxide (CO.sub.2) while producing freshwater are provided. An exemplary method includes producing saline water from a saline aquifer, desalinating at least a portion of the saline water, producing freshwater and waste brine, mixing waste CO.sub.2 with the waste brine forming a brine/CO.sub.2 mixture, and injecting the brine/CO.sub.2 mixture into the saline aquifer.

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.