Abstract: This paper presents two methods for easy determination of water influx in reservoirs based on material balance theory, i.e., the NetProduction Volume Curve and the Production Index Curve. These methods can be used for estimation of water influx in reservoirs without anyassumption of aquifer shape and size by apply ing the production performance data. Hence the tedium of the conventional trial-and-error cailculation and obnious uncerlainty couldbe overcome imapplication of the easy and pract cal new methods

Key words: reservoir, edge water, bottom water, water influx, material balance method