Systems and methods used in treating a subsurface formation are described herein. Some embodiments also generally relate to barriers and/or methods to seal barriers. A method used to treat a subsurface formation may include heating a portion of a formation adjacent to a plurality of wellbores to raise a temperature of the formation adjacent to the wellbores above a mobilization temperature of bitumen and below a pyrolysis temperature of hydrocarbons in the formation; and allowing the bitumen to move outwards from the wellbores towards a portion of the formation comprising water cooler than the mobilization temperature of the bitumen so that the bitumen solidifies in the formation to form a barrier.