Formation mechanisms of hydrocarbon reservoirs associated with volcanic and subvolcanic intrusive rocks: Examples in Mesozoic-Cenozoic basins of eastern China

Abstract

Numerous petroleum-producing Mesozoic–Cenozoic basins are present in the coastal areas of eastern China. Voluminous volcanic and subvolcanic intrusive rocks, dominantly basaltic and, to a lesser degree, trachytic in composition, are intercalated or intruded in the sedimentary sequences. These magmatic rocks can serve as cap rocks as well as reservoir beds for hydrocarbons. Hydrocarbon reservoirs related to volcanic rocks can be classified into the volcanic-trapped type, the volcanic-sealed type, and the weathering crust type, and those related to subvolcanic intrusions include the doming-derived fracture type, the cryptoexplosive breccia type, the primary fracture type, the alteration zone type, the contact zone type, and the laterally sealed type. A generalized model for the formation of hydrocarbon reservoirs related to volcanic and subvolcanic rocks is proposed. We call for more attention to volcanic- and subvolcanic-related reservoirs during the exploration for hydrocarbons.