A coal formation may be treated using an in situ thermal process. A mixture
of 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. Heat
sources may be used to heat the formation. The heat sources may be
positioned within the formation in a pattern. The pattern may be a
repeating pattern of triangles.
