Method and apparatus for in situ gasification of coal and the commercial products derived therefrom

A method of in situ gasification of a subsurface coal formation comprising the steps of:

• establishing a passage between a surface location and the coal formation,
• setting a casing in the passage,
• injecting a plurality of hot particles in a non-flammable environment into said casing, said particles having a temperature in excess of the ignition temperature of coal, and
• allowing at least some of the particles to come into contact with the coal to ignite the coal causing it to burn and give off useful gases.

A method of in situ gasification of a subsurface coal formation comprising the steps of:

• establishing a passage between a surface location and the coal formation,
• setting a casing in the passage,
• placing a plurality of rigid particles in the casing,
• igniting the coal formation, and
• allowing the rigid particles to move into cavities formed in the burning coal formation to serve as a propping agent in the event of a cave-in.

A method of in situ gasification of a subsurface coal formation comprising the steps of:

• establishing a passage between a surface location and the coal formation,
• setting a casing in the passage,
• providing a plurality of dividers in the casing separating the casing into a plurality of vertically aligned compartments, each of said dividers having an opening therein to provide fluid communication between the compartments,
• positioning an injection conduit in the casing for injecting gasifying agents into the coal formation,
• positioning gas removal conduits in the casing to remove produced gases from the coal formation, said removal conduits being positioned so as to pass through the compartments in the casing,
• positioning a fluid removal conduit in the casing to transfer fluids from a compartment adjacent to the lower end of the casing to the surface location,
• igniting the coal formation so as to produce hot gases which are transferred to the surface location through the gas removal conduits, and
• circulating a heat receptive fluid downwardly through said compartments and upwardly through said fluid removal conduit to effect a heat transfer from the produced gas to the heat receptive fluid.

A method of in situ gasification of a subsurface coal formation comprising the steps of:

• establishing a passage between a surface location and the coal formation,
• setting a casing in the passage,
• establishing an hermetic seal between the coal formation and the surface location,
• igniting the coal formation,
• burning the coal in situ to form and maintain a reaction zone,
• injecting an oxidizing agent into the coal formation while alternately adjusting the quantity, quality and pressure of the injected oxidizer to alternately establish an oxidizing and reducing environment in the coal formation, and
• withdrawing the produced gases from the coal formation and delivering them to the surface location.