A coal 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 pyrolysis temperature. Heat and pressure applied to the formation may be controlled so that a majority of the hydrocarbons produced from the formation have carbon numbers less than 25. Conditions may be controlled to produce low quantities of olefins in condensable hydrocarbons produced from the formation and low quantities of olefins in non-condensable hydrocarbons produced from the formation.