鄂尔多斯盆地东北部下石盒子组盒8段辫状河三角洲沉积特征

中二叠统下石盒子组盒8段为鄂尔多斯盆地东北部天然气的主产层位,其储集砂体受控于沉积相带的展布。通过对野外露头、岩心及测井曲线等综合分析,笔者认为研究区内主要以发育辫状河三角洲为特征,并对其沉积特征、影响其形成和发育的机理,以及岩相和砂体的展布特征进行深入研究。认为该区盒8段三角洲为辫状河-浅水型湖泊三角洲,在三角洲平原相区储集砂体为分流河道沉积;而在三角洲前缘相区则为水下分流河道沉积,河口坝、席状砂及远砂坝等沉积微相不发育。

Sedimentary characteristics of the braided deltas in the eighth member of the Lower Shihezi Formation in the northeastern part of the Ordos Basin

The eighth member of the Middle Permian lower Shihezi Formation is considered as the main gasproducing horizons in the northeastern part of the Ordos Basin, where the reservoir sandstones are mainly controlled by sedimentary facies. The examination of field outcrops and well logs on the basis of sedimentary characteristics, depositional mechanisms, sedimentary facies and sandstone distribution has disclosed that there widely occur the braided deltas, especially the braided-shallow water lacustrine deltas in the study area. The reservoir sandstones in the delta plain facies are interpreted as distributary channel sandstones, while those in the delta front facies are considered as the subaqueous distributary channel sandstones. The channel-mouth bar, sheet sandstone and distal bar sedimentary microfacies are less developed.