鄂尔多斯盆地南缘下奥陶统马家沟组马六段成藏条件分析

Reservoir-forming Conditions of Early Ordovician Majiagou Formation Ma 6 Member,Southern Margin of Ordos Basin

鄂尔多斯盆地下奥陶统马家沟组马六段在盆地南缘广泛分布,从北向南厚度增大。岩性为含藻石灰岩、云斑灰岩、粉晶白云岩和颗粒白云岩。从早奥陶世华北地台南缘大地构造背景出发,分析了鄂尔多斯盆地南缘下奥陶统马家沟组马六段的沉积环境和沉积模式。综合露头剖面与井下岩心分析资料及岩性组合特征,探讨了马六段成藏要素及其空间配置关系,指出马六段以局限洼地和白云质石灰岩台坪沉积为主,局部层段发育礁滩相沉积,经后期成岩白云岩化可形成有效的白云岩储层,与上覆富含泥质的平凉组共同形成上生下储型成藏组合,具有一定的资源潜力。

The Ma 6 member of the Early Ordovician Majiagou formation distributes broadly along the southern margin of Ordos basin, its thickness increases gradually from north to south, and its rocks mainly of algal limestone, patchy limestone, powder crystal dolomite and grained dolomite. Based on the tectonic setting of the southern margin of the Early Ordovician North China platform, the sedimentary environments and sedimentary patterns of the Majiagou Formation are analyzed. The reservoir-forming factors and their space arrangement are researched using the outcrop data, downhole core data and lithologic combina- tion features. The result shows that reef flat facies deposition is developed in some parts of the Majiagou Formation and they form dolomite reservoirs through later diagenesis and dolomitisation. These dolomite reservoirs and the neighboring muddy intervals form reservoir-forming combination of up generation and down storage, and have a exploration potential.