Abstract:

Various types of the old oil pool sared eveloped in the Late Paleozoic strata of the Dianqiangui area，those developed in reef rocks of Devonian and Permian are especially wide spread.These old oil pools,especially for those belonging to sponge reef types that are developed in the margin of attached carbonate plat-form and on the isolated platforms,are almost characteristic of asphalt indications.The old dolomitic type oil pool developed in the intraplatform limestone strata of the Permian Maokou Formationis formed in the interior part of the attached platform,and is marked by oil indication and is obviously different to those old oil pools of sponge reef type.Apart from the potential source rocks that are constituted by deep water argilutites of inter platform basin,the hydrocarbon source for the old dolomitic type oil pool in Wudang of Guyang maybe come from the potential source rocks that are composed of the shallow platform dark limestone of the Permian Qixia Formation under lying the Maokou Fomation.The stratigraphic position and the out putting features for this old dolomitic type oil pool indicate several regularities as foUow:Firstly,two third-order sequences can be divided in the limestone strata of the Maokou Formation；Secondly,the dolomitic type reservoir is frequently formed in the top part of the third-order sequence,which is genetically related to the shoaling process of sedimentary environment caused by the forced regression;Thirdly,in the process of both accumulation and migration of oil and gas the special oil pool of the stratigraphic-lithologic type could be formed in the top part of the carbonate third-order sequence.All of these features show that the finding of this old dolomitic type oil pool could provide an important clue for the future exploration of oil and naturl gas.

Key words: old oil pool, the Maokou Formation, Pemian, Wudang of Guiyang City