Abstract: In thermal recovery wells, casing is heated by the injection steam and thermal stresses are produced in the casing. Casing deforms when the thermal stresses exceed the yield point of the steel. Studies show that casing deformation is likely to happen in the conventionally cemented wells in normal injection steam temperature. Conventional technologies used to protect casing from failure are inefficient theoretically. Half pre-heating cementing technology involves running in a heater down to the production casing section where it is subject to the heating by injection steam and heating the casing to a pre-determined temperature, WOC in the heating condition and pulling out the heater finally. This technology keeps the casing in an elastic state in the whole thermal recovery process without plastic deformation taking place, and thus resolves the problem of thermal casing failure.