鄂尔多斯张夏期原型盆地类型与油气勘探前景

中寒武统张夏组鲕粒灰(云)岩在鄂尔多斯具有一定规模分布,是值得探索的油气勘探领域之一。综合分析认为:张夏期盆地为隆坳相间格局,南北向展布的中央古隆起雏形起到了分隔鄂尔多斯西缘祁连海和南缘秦岭海的作用,盆地原型为克拉通台地型盆地。张夏组储层鲕粒结构类型复杂,主要成岩作用为白云岩化和埋藏溶蚀作用等;孔隙结构与储层物性分析表明为低孔、低渗储层,局部发育一些较好的储集岩。油气地质条件有利因素包括储集条件、储盖组合和构造背景,不利因素为寒武系烃源岩不发育。加强对寒武系的研究和勘探力度,争取油气勘探新突破是可能的。

THE PROTOTYPE BASIN OF CAMBRIAN ZHANGXIA PERIOD AND OIL-GAS EXPLORATION PROSPECT IN THE ORDOS BASIN

The substantially distributed Middle Cambrian oolitic limestone and oolitic dolomite in Ordos Basin are potential targets for petroleum and gas explorations.The appearance of alternative pattern of depressions and uplifts of Zhangxia Stage,together with the north—south trending of central paleouplift actually played the role of separating the Qilian Sea on the west margin of Ordos Basin and the Qinling Sea on the south margin of Ordos Basin.The Zhangxia Formation is composed mainly of complex oolitic structures with dolomitization and burial erosion as major diagenetic processes.The Zhangxia Formation is predominately low porosity and low permeability carbonate reservoirs.The reservoir capacity,cap assemblage and tectonic setting are among those favorable conditions for the preservation of petroleum or gas while the poorly developed source rock for hydrocarbon in Cambrian was the disadvantage of further exploration.