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Abstract-A large number of thermal recovery wells casing was damaged during the early development of Du 84. Casing damage thermal production wells amounted to 214 by the end of 2002, accounting for 66.7% of the production wells. The casing damage had affected the normal production of these thermal wells. Thus casing damage mechanism and casing damage prevention were key issues in Du 84 thermal production wells. Through investigations and researches, reasons for the initial casing damage were determined as follows: higher thermal stress, sand production in oi1 wells, unfit sub with API round thread and bias buttress thread, and improper heat insulation tubing and heat insulation measures. In order to reduce the casing damage rate caused by the factors of thermal stress and low casing strength Etc., the related measures adopted are: pre-stress pulling completion, substituting N80 casing with bias buttress thread for the common casing, using special cement for thermal production wells and returning to the surface, and utilizing fine heat insulation tubing. After the management, the casing damage in therma1 wells was decreased, but the initia1 casing damage was stil1 heavy. Thus new techniques were adopted: reducing the casing stress during steam injection using heat stress compensate tool, increasing the deformation resistance using TP100H casing, and solving hoop stress problems of production casings caused by sand production and perforation using TP120TH external upset casing. Through the long-term researches and practices, the initial casing damage rate of therma1 wells was reduced, which ensure the effective development of Du 84 super heavy oil with steam stimulation method and SAGD development mode conversion.

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