A thick sedimentary sequence of Tertiary and Quaternary ages, which chiefly consists of turbidites, is developed in the Omaezaki district, Shizuoka Prefecture.Structural traps such as anticlinal, fault and combination traps are found in this area. Fine-grained sandstones in the Sagara and Kurami Groups of Miocene age are considered to be main reservoirs. The source rocks are argillaceous sediments in the lower Miocene as indicated by total organic carbon content, type of organic matter and its maturity. However, the potential for yeilding hydrocarbons is relatively low in comparison with the potential of source rocks in the Niigata district. Geochemical data of source rocks and of oil and gas in reservoirs suggest that the B Formation in the MITI Sagara well is the possible source rock for the oil and gas which are produced from the Sagara oil field and also from this well.In the offshore area, several structures remain undrilled, and there is a possibility that hydrocarbon pools (mainly gas) may be discovered.