Failure Analysis of Horizontal Well Tubing in Fire-Flooding Gravity Drainage

In the process of fire-flooding gravity drainage, the horizontal well is the only oil-exhaust and exhaust passage. The downhole oil pipeline is long-term serviced in the temperature ramge of 200~300 ℃ and CO₂ environment, intermittent high temperature and high oxygen content may appear. The physicochemical properties, metallographic structure, fracture morphology and corrosion products of a horizontal well fracture tubing were analyzed, and the causes of tubing fracture were explored. The results show that the failure mechanism of the fractured tubing was high temperature creep rupture. The aging of the tubular structure was caused by localized high temperature annealing for a long time. The yield strength and tensile strength were much lower than those of the standard. Under the axial tensile stress, the tubular body creeped and then fractured, and high temperature oxidation of the inner and outer walls of the tube caused thickness of the wall to be thinned, which aggravated the fracture of the oil pipe.