Customs duty exemption for imports used in petroleum operations, subject to Ministry-issued certificate validating contract use. The notification exempts specified goods imported for petroleum operations under specified government contracts from customs duty and any additional duty, conditional on production of a certificate from an officer not below the rank of Deputy Secretary in the Ministry of Petroleum and Natural Gas. The exemption covers a listed range of equipment and materials used in exploration, drilling, production, pipeline installation, platform installation and maintenance, including vessels, drilling rigs and equipment, helicopters, specialised service equipment, casings and tubings, chemicals, platforms and associated machinery, line pipes, pipe-laying vessels, pollution-control vessels, stores, spares and oil well cement.