An oil shale formation may be treated using an in situ thermal process. Heat may be provided to the treatment area. Fluids may be injected into the formation to remove a component within the formation. Hydrocarbons, H₂, and/or other formation fluids may be produced from the formation. In some embodiments, fluids may be injected prior to production of formation fluids. Alternatively, fluids may be injected after production of formation fluids.