To deal with the world-class difficult problems for reef-flat complex (RFC) oil-gas field in Tazhong No.1 slope break, the assorted series of technologies for exploration of the marine carbonate reservoirs are presented. The hydrocarbon accumulation geologic theory of RFC large reservoirs is developed. The deepest and oldest giant condensate gas reservoir in the world has been found out: the RFC giant condensate gas field of the Ordovician is proved as the first one in China. These exploration and development achievements have enriched the theory and technology for exploration of hydrocarbon accumulation in domestic platform margin energetic facies belts.