The Oulituozhi oil-gas field in the Liaohe Tertiary ba sin,Northeast China,has a dail y output of more than 200 tons of crude oil and a significant amount of gas.Oil and gas are accumulated in the top portion of a subvolcanic trachytic porphyry whichintruded in the Eocene Shahejia Formation.Reservoir space is dominated by crypto-explosive breccias,crack networks,vertical open cracks and tensional microfissures.These varieties of space were produced by explosions of water and other volatiles below an crystalline rind,by upwelling forces of the magma from the depth,and by cooling and volume contraction of the solidified rocks.Because such a combination of space is characteristic of a subvolcanic porph yry,the reservoir at Oulituozhi could be designated as a porphyry-type reservo ir.Such a model should be taken into account during exploration work for oil and gas in the Olituozhi area.
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