Yunnan-Guizhou-Guangxi Region

which is covered by 580

000 km

2

sedi-mentary rocks

can be divided into three fields in petroleum prospecting.The first being covered continuosly by Palaeozoic carbonate rocks was avast sea basin during Palaeozoic-Early Mesozoic and then became a huge oil-and gas-bearing basin.But it was disintergrated after Indo-China tectonic move-ment.Therefore

the possible oil and gas pools there might be distroied con-siderably.Different source rocks are preserved in structural basins in localparts of the region.High hopes of petroleum prospecting were at first placed onthis field and a lot of exploration work was done.Due to the complexity of geo-logical structures and the difficulties in exploration

the effect is confirmedto be quite disappointing.The second field is the region covered by Mesozoic continental red beds su-perposed on formations of the previous carbonate rocks after its uplift.Nowsome gas fields have been discovered in the region.The exploration effect and petroleum prospects in this field are much better than that in the first field.The third one is small Cenozoic basins superposed on Palaeozoic-Mesozoicstrata separately.Though they are small both in area and scale of oil and gas pools

yet these basins can be explored easily.So the exploration effectis the best among all three.The author suggest that the first field should not be considered at presentas the main target in petroleum prospecting due to the difficulties in explo-ration;the second field should be taken as the main target in recent years ac-cording to its favourable conditions in oil generation and present prospectingmethods;the third field is important in practice.Certain reserves have beenfound in Baise Basin and we are bound to find more small oilfields like Baise type with less investment.