Large marine carbonate condensate gas reservoirs occur in the Yingshan Formation in the north slope of Tazhong uplift and their cap rock is tight carbonates in the 3

rd

-5

th

member of Lianglitage Formation.The carbonates are distributed widely in the whole north slope of Tazhong uplift

which is massive and is superimposed vertically and connected laterally

sealing the hydrocarbons in the underlying Yingshan Formaiton.Based on analyses of lithology

thickness and clay content of the tight carbonates

we summarized their distribution patterns and relationships with hydrocarbon accumulation and discussed the control of their thickness and clay content on oil/gas distribution.The study shows that the tight carbonate cap rock in the north slope of Tazhong uplift may be efficient seals when its thickness is equal to or more than 80 m and its clay content GR value is over 20 API

Thickness and clay content can complement each other for sealing capacity.