In this research, gravity surveying is used for exploration of petroleum reservoirs in the Chenaran region, northeast of Iran. For this purpose a gravity survey is conducted by making gravimeter readings at 816 sites, located along 26 parallel lines of profiles. The recording sites are at equal distances of I km and the lines of profiles are spaced at equal intervals of 2 km. After estimating the surface density value, two dimensional and three dimensional Bouguer anomaly maps are made in which all the relevant corrections, including the free-air correction, the Bouguer correction, the latitude correction, the terrain correction, the drift correction, and the tidal correction, have been applied. For interpretation of these maps, local and regional anomalies have been separated by using two of the most widely used schemes that involve computation of weighted averages, namely upward continuation method and the second vertical derivative respectively. The local patterns of Bouguer gravity variation reveal the presence of buried anticlinal structures and fault zones in the region. Due to the favourable geological conditions for petroleum accumulation in the region, it is very likely that petroleum reservoirs have been trapped by these buried structures. Finally the results indicate that gravity survey, particularly, Bouguer anomaly separation, plays ae important role in petroleum exploration.