Abstract: In order to improve mature single well production and speed up the curing process of casing damaged wells with casing diameter of ?146 mm, it is decided to use the reaming tool to increase the diameter of completed wells, and to increase cement sheath thickness, furthermore, to improve well service life. In this paper, the completion of Well Z3034 is designed and optimized from three aspects, completion method, completion fluid and borehole reaming. The working process of reaming and completion string tripping are introduced in detail, the success of the well completion provides a feasible way for subsequent treatment of slim-hole casing damaged wells in Redbai oil field and conducting of slim-hole sidetracking. The production of Well Z3034 has been relatively stable since the start of production, with the average rate of 5t/d, and it is 5 times of the non-sidetrack case.