Working principle:

During the steam injection process, the axial stress of the casing caused by temperature changes acts on both ends of the thermal compensator. The center tube and outer tube of the compensator generate relative motion, compensating for the slight expansion and contraction of the casing, effectively reducing the damage of thermal stress to the casing, and thus achieving the purpose of protecting the completion string of thermal directional wells and thermal horizontal wells. 

Performance characteristics:

The prestressed protection device has the same strength performance as the selected casing

Having good airtightness, ensuring no leakage during cementing, steam injection and thermal recovery processes;

Simultaneously using techniques such as prestressed cementing can better prevent casing damage.