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The damaged casing is a headache in the Xingbei area of Daqing Oil Field,where a total of 1437 casing-damaged wells were found in the recent years.From 1982 to 1998, there were 515 casing-damaged wells in Xingbei area that were put into repair. Of those wells, 238 ones were successfully repaired, 130 ones were stopped before the repairing work was finished and 147 ones were abandoned as useless.The rehabilitation ratio was only 46 percent. Two reasons were found on the basis of analysis. One is that the smaller the casing damaged pathway is, the harder it is to rehabilitate. The other is that the reshaping and path-expanding technique is inadequate to meet the need for repair the small-path casing damaged wells, affecting improvement of the rehabilitation ratio. Therefore, the research has been made on the reshaping and path-expanding technique for the small-path casing damaged wells since 1999.