A hydrocarbon containing formation may be treated using an in situ thermal
process. Hydrocarbons, H.sub.2, and/or other formation fluids may be
produced from the formation. Heat may be applied to the formation to raise
a temperature of a portion of the formation to a pyrolysis temperature.
Pyrolysis products may be produced from the formation. After pyrolysis,
the temperature of the portion may be raised to a synthesis gas production
temperature. A synthesis gas producing fluid may be introduced into the
formation to generate synthesis gas. After synthesis gas production, the
portion may be cooled and used to store carbon dioxide or other fluids.
