A Study of Inspecting the Stress on Downhole Metal Casing i n Oilfields with Magnetic Memory Method

This paper introduces a surface experimental model machine of metal magnetic memory inspection(MMI) which is co-developed by Daqing Logging & Testing Services Company (DLTS) and EDDYSUN C ompany （Xiamen ）.The model machine is compared with the instrument which was introduced from Russia and an experimental study of cas ing enforcing inspection on 25 casings is carried out with the finding of good corresponding r elationship between the stress on casing and the information of magnetic memory. It provides a criterion of four-class semi-quantitative evaluation on the casing stress distri bution. On the basis of this, a model machine of down-hole 8-electrodes inspecting the metal cas ing magnetic memory is developed and field test has been done successfully. It provides the basis for overcoming the difficulty of evaluating the downhole casing and tubing lifetime in the oil field and for putting this model into commerce in the future.