Precretaceous marine sediments(T

2

-Z)in Jianghan Plain

being 1000—5000m thick

is in fine source-reservoir-cap rock assemblage.The main source rocks are platform biolithite of the Permian

Silurian

Ordovician

Cambrian

Sinian and dark mudrock in deep basin facies.The organic matter of the source rocks is highly matured and natural gas is the main product.The weak tension reformed areas of Cenozoic usually have fine hydrocarbon preservation condition while the uplifted areas formed after Indo-Chinese epoch are generally in lower organic matter evolution stage and have secondary oil-generation condition.The study area contains three kinds of hydrocarbon-pooling areas:intra-marine facies structures

buried hills and the lower walls of the overthrusts.The ex-ploration area ranges 3.74×10

4

km

2

.Taking Silurian as the boundary

the marine sedi-ments form two source-reservoir-cap rock assemblages

the upper one

that is to say

the anticlinal structural zones in the central parts of Dangyang and Chenhu synclinoria arefavourable for recent hydrocarbon exploration.