In situ oxidation of subsurface formations

A method for treating a subsurface formation, comprising:

• heating a first portion of the formation from one or more heaters located in the first portion;
• producing hydrocarbons from the first portion;
• reducing or turning off the heat provided to the first portion after a selected time;
• injecting an oxidizing fluid in the first portion to cause a temperature of the first portion to increase sufficiently to oxidize hydrocarbons in the first portion and a third portion of the formation, the third portion being substantially below the first portion;
• heating a second portion of the formation from heat transferred from the first portion and/or third portion and/or one or more heaters located in the second portion such that an average temperature in the second portion is at least about 100° C., wherein the second portion is substantially adjacent to the first portion;
• allowing hydrocarbons to flow from the second portion into the first portion and/or third portion;
• discontinuing or reducing injection of the oxidizing fluid in the first portion;
• and
• producing additional hydrocarbons from the first portion of the formation, the additional hydrocarbons comprising hydrocarbons oxidized in the first portion, at least some hydrocarbons from the second portion, at least some hydrocarbons from the third portion of the formation, or mixtures thereof, and wherein a temperature of the first portion is below 600° C.