鄂尔多斯盆地大牛地气田上古生界沉积演化特征

鄂尔多斯盆地上古生界海陆变迁过程中其沉积演化特征决定了气田内储层成因类型,分布特征和分类评价。通过对大牛地地区太原组-山西组-下石盒子组岩芯观察,结合测井,地震等资料分析,综合确定太原组为滨浅海环境,下部发育碳酸盐岩斜坡体系,上部为障壁-潮坪-潟湖沉积体系;受北部物源区抬升影响,陆源推进和尚未完全褪去的海水影响,山西组为海陆过渡环境,发育潮控辫状三角洲沉积体系;伴随北部物源区逐渐抬升,陆相碎屑显著推进至研究区,下石盒子组底部形成陆相河流环境,发育辫状-曲流河沉积体系;大牛地上古生界整体呈陆进海退特征。由海向陆变迁过程中,太原组和山西组发育的煤层是研究区重要烃源岩;太原组上部障壁砂坝和潮道等砂体,山西组下部辫状河道,潮道和潮砂坝砂体和下石盒子组底部厚层叠置辫状-曲流河道砂体是研究区内上古生界重要的产气储层。

Characteristics of Sedimentary Evolution in the Upper Paleozoic,Daniudi Gasfield,Ordos Basin

Characteristics of the sedimentary evolution in the progress of transformation from ocean to continent determines the genetic type, distribution, and classified evaluation of gas reservoir in Upper Paleozoic of Daniudi Gasfield, Ordos Basin. Analysis of core observation, in combination with logging, seismic data of Taiyuan-Shanxi-Xiashihezi Formations, resulted that carbonate ramp in lower part and barrier-lagoon-tidal flat system in the upper part of the Taiyuan Formation in a shore environment; the Shanxi Formation is a tidal dominated braided delta system in the background of transition environment; and the Xiashihezi Formation is a fluvial system as the continually north uplift and continental clastic significantly advance to the study area; the whole Upper Paleozoic shows a continued progress of progradation. In the change from sea to land environment, coals of the Taiyuan and Shanxi Formations are main hydrocarbon resources in the study area; sand bodies of the barrier bar, tidal channel of Taiyuan Formation, the braided and tidal channel and tidal sand flat of Shanxi Formation, and the stacking braided-meandering channel of Xiashihezi Formation are favorable reservoir in Upper Paleozoic.