An oil shale formation may be treated using an in situ thermal process. A mixture
of hydrocarbons, H2, 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 desired temperature. An average temperature and/or
pressure within the formation may be controlled to inhibit production of hydrocarbons
that have carbon numbers greater than a selected carbon number. In some embodiments,
the selected carbon number may be 25. A small amount of hydrocarbons having carbon
numbers greater than the selected carbon number may be entrained in vapor produced
from the formation.
