T The Lower Cibulakan Formation Carbonate Reservoir is known to be well developed in the North West Java Basin. There are more than thousands of wells in the North West Java area that have been drilled and penetrated the carbonate rock reservoir in the Lower Cibulakan Formation. To this day, hundreds of wells have been producing from the carbonate rocks reservoir of the Lower Cibulakan Formation of the North West Java Basin, both onshore and offshore. Oil production in these wells will naturally cause an increase in oil-water contact, thus this study is to see changes in oil-water contact due to production using log data. Some existing subsurface data in the form of geological, reservoir and geophysical data can be used as supporting data for this study, but this study only use the complete log data, especially the existence of sonic log data, which uses petrophysical analysis for the manufacture of M and N and structure maps that will later be used as a method to see the movement of oil and water contacts in addition to other methods. This research is useful for determining the perforation hose and also for positioning the development well so that the results are optimum and the resulting water content is not too high because of the distance from oil-water contact.