Abstract: After a long-time developing with water-injection, the distribution of oil water in Machang Oilfield reservoir has changed greatly, which results in the falsification of electric feature of logging, and therefore no guide meaning for the oilfield development. Because of the complex geological condition, the result of O/C monitor and DDL-Ⅲ air-lift seeking water can not meet the residual oil monitor and water plugging, which leads to bad effect in production fluid frame adjustment. The application of high precision C/O spectral logging can monitor residual oil, solve the problem of principal water-producing formation in multiplayer commingled production, seek high water-cut oil layer and image the vertical distribution of residual oil so as to provide geological dependency for tapping potential to old oil wells and adjustment to production fluid frame. There is good application effect in Machang Oilfield.