Abstract: In view of the long-term high temperature and high pressure of the casing and frequent casing damage in the process of steam flooding, a statistical analysis of the casing damage in the steam flooding of the Qi 40 Block in Liaohe Oilfield was conducted, and the mechanical and thermodynamic study was conducted for the casing damage process. The results showed that when steam was injected into the oil well, the casing temperature raised, resulting in thermal expansion force which increased with temperature; when the thermal expansion force was greater than the cementing resistance of the casing, the casing broke away from the cement sheath and expanded freely, and an inclined plane effect was produced on the contact surface of them, making the thermal expansion force change from the longitudinal elastic force to the increasing lateral squeezing force that brought extrusion damage to the casing, which is the complete casing damage mechanism. Based on the damage mechanism, the casing coupon technology was developed. Preliminary tests have shown that the casing coupon can greatly increase its cementing force and reduce the probability of casing damage. The study results are of important significance for improving the development benefits of heavy oil old areas.

Key words: thermal recovery of heavy oil, casing damage mechanism, casing coupon, casing treatment, completion method, steam flooding, Liaohe Oilfield