Within a period of 5 years Royal Dutch Shell will be searching for oil and natural gas in the Silistar Block 1-14 in the Black Sea after today the company signed an agreement for exploration with the Bulgarian government. The contract has a term of five years with an option for two extensions for two years each, it was reported. In order for actual research works to begin, it is still necessary that Shell obtains all necessary permits. According to Bulgarian Minister of Energy, Temenuzhka Petkova, the agreement was an important step towards achieving one of the main priorities of Bulgaria in the energy sector - diversification of supply sources of natural gas.