CASING CEMENTING WITH INTERNAL PREPRESSURIZATION FOR THERMAL RECOVERY WELLS

The thermal recovery is a very common and effective method for producing heavy oil. The casing failure is a very serious problem in thermal recovery wells. In steam injection process, casing is heated by steam. The change of casing temperature produces thermal stresses in the casing. The casing deforms when stresses exceed the yield point of its material. If using conventional cementing technology for thermal recovery wells, the casing deforms due to thermal stresses in steam injection process. Technologies conventionally used to protect the casing from failure for thermal recovery wells are inefficacy theoretically. The casing cementing with internal prepressurization for thermal recovery wells refers to exert inner pressure on payzone production casing and make payzone production casing expand in the cement solidifying period. The calculations show that the casing with internal prepressurization technique performs greater safety coefficient during the whole production cycle and no plastic deformation. This technique will be an important method to prolong the casing life of the thermal recovery well.