Marine carbonate rocks in South China cover an area of 200?10

4

km

2

.From Upper Sinian to Lower Triassic

the total thickness of source rocks is up to several thousand me-ters with rich organic matter.But preservative condition underwent serious damage as in-tensive tectonic movements took place in Indo-China period.As faults and denuda-tion caused surface water to distroy reservoir

thus favourable preservation region must be the one that has fine covery rocks in vertical and good sealing hydrogeological condition in horizontal.The Middle Triassic-Jurassic

Silurian

Lower Cambrian in the study area are perfect regional covery rocks which may seal gas reservoir with more than 500m high gas column.There are three kinds of preservation area:1.Paloozoic bare zone;2.Meso-Cenozoic covering zone;3.The frontal zone of nappe structure.