Casing Cementing with Internal Pre-pressurization for Thermal Recovery Wells

Thermal recovery is a very common and effective method for producing heavy oil. Casing failure is a very serious problem in thermal recovery wells. In some oilfields, more than 95% of the casing for thermal recovery wells failed due to thermal stresses. In the steam injection process, the casing is heated by steam. The change in casing temperature produces thermal stresses. The casing deforms when stresses exceed the yield point of its material. If using conventional cementing technology for thermal recovery wells, the casing will deform as a result of thermal stresses as a result of the steam injection process. Conventional technologies used to protect thermal recovery well casing from failure are theoretically ineffective. Casing cementing with internal pre-pressurization for thermal recovery wells refers to the exertion of inner pressure on payzone production casing to make payzone production casing expand in the cement solidifying period. Calculations show that casing with internal pre-pressurization technology achieves a greater safety coefficient during the whole production cycle and results in no plastic deformation. This technology will be an important method to prolong thermal recovery well casing life.