Liaohe Oilfield has developed heavy oil for more than 40 years, and accumulated a lot of experience in research and practice for well integrity under Cyclic Steam Stimulation, Steam Flooding, SAGD, In-situ Combustion. This paper will introduce the systematical achievements, including well completion design, casing selection, cementing slurry, string attachment, etc.

Based on the continuous study of fundamental principles, thermal casing, details of pre-stress method and industrial evaluation, the well completion design method has been optimized and the practicality has been checked ultimately. In particularly, the pre-stress method has been deeply studied through experiments and calculations. We have made a further improvement on string attachments. According to thermal recovery environment and low-cost requirement, a Portland cementing slurry characterized with low Young’s modulus, high compressive strength, and good temperature resistance, has been researched and used in field.

The pre-stress method for the completion string design is testified to be effective in some extent, because the stress pre-imposed can reduce the string stress and minimize the wellhead growth in thermal recovery. The newly researched cementing slurry has been systematically tested in laboratory, the results are excellent: Young’s modulus ≤6, compressive strength ≥21MPa, temperature resistance 350°C, cost lower than 1000$/t. Casing used in thermal well should have a good performance of collapse strength, and the thickness to diameter ratio is important as well as the premium connection. The newly designed anchor with 6-cylinder anchor claws attached the completion string can adapt with softy and hard stratum. With the standardization of all the measures used in Liaohe oilfield, the thermal well integrity becomes better and better. The statistical data shows that the casing damage rate lowered 34%, and the life of the thermal well prolonged at least 2 years on average.

Some contents in this paper are novel, such as the result of the pre-stress experiment, Portland cementing slurry with low-cost and good performance, newly designed anchor, etc. We believe all the experience accumulated and introduced in this paper could give some useful directives for thermal well integrity all over the world.

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