METHOD AND APPARATUS FOR USING PRESSURE CYCLING AND COLD LIQUID CO2 FOR RELEASING NATURAL GAS FROM COAL AND SHALE FORMATIONS

摘要

A method and apparatus for sequestering carbon dioxide (CO2) gas and releasing natural gas from underground coal and/or gas shale formations using CO2 gas captured from the flue gas of a coal burning power plant, and processing it to produce cold liquid pressurized CO2, and injecting the cold liquid CO2 under pressure to create fractures within the formation and causing the CO2 to be adsorbed into the coal or gas shale and natural gas (CH4) to be desorbed, released and recovered. A special pressure cycling process is used to enable the pressure within the formation to be increased and decreased, including allowing the liquid CO2 to change phase to a gaseous CO2, and injecting the liquid CO2 under pressure repeatedly, which causes greater expansion of the proliferation zone within the formation, and more efficiently releases CH4.

主权项

1. A method of sequestering carbon dioxide and recovering natural gas from a coal or gas shale reservoir, comprising:
capturing or producing carbon dioxide gas from coal or from flue gases of a power plant, incinerator or chemical processing plant; cooling carbon dioxide gas to create liquid carbon dioxide; injecting the liquid carbon dioxide into an injection pipe extended into said reservoir, wherein said injection pipe has perforations that allow the carbon dioxide to be released into said reservoir, using the following steps: 1) introducing said liquid carbon dioxide into said injection pipe gradually with a top vent of said injection pipe open and a bottom valve of said injection pipe closed; 2) turning on a pump to pressurize said liquid carbon dioxide; 3) closing said top vent of said injection pipe and injecting said pressurized liquid carbon dioxide into said injection pipe until the pressure within said injection pipe reaches a predetermined amount which is above the fracture strength of said coal or shale in said reservoir; 4) opening said bottom valve of said injection pipe and allowing said liquid carbon dioxide to be released under pressure through said perforations and into said coal or shale reservoir and causing the coal or shale in said reservoir to break up; 5) closing said bottom valve and allowing said liquid carbon dioxide in said reservoir to change phase into a gaseous carbon dioxide; 6) allowing the gaseous carbon dioxide to adsorb onto the coal or shale and allowing natural gas to be desorbed and released from the coal or shale; 7) recovering the natural gas released from the coal or shale through one or more recovery pipes; and 8) repeating steps 1) through 7).