基准面旋回对砂岩成岩作用的控制--以鄂尔多斯盆地西南缘汭水河延长组露头为例

The control of the sequence boundary over the sandstone reservoir and diagenesis:a case study of Yanchang Formation outcrop along the Ruishui River profile

以鄂尔多斯盆地西南缘汭水河露头剖面延长组长9—长7辫状河三角洲沉积为例,重点讨论三级层序界面上下的砂岩储层成岩特征。通过大量的铸体薄片鉴定,扫描电镜、X衍射等实验分析,发现汭水河延长组露头剖面层序界面对砂岩储层成岩具有控制作用,基准面下降半旋回内填隙物以浊沸石为主,基准面上升半旋回内以方沸石为主,孔隙主要为溶蚀填隙物形成的次生孔隙,界面之上面孔率好于界面之下的面孔率,有利于储层发育。

Exemplified by Chang 9-Chang 7 braided-channel delta sediments of Yanchang Formation along Ruishui River outcrop profile in southwestern Ordos Basin, this paper deals mainly with sandstone reservoir and diagenseis characteristics of the Grade 3 sequence boundary. An analysis by such experimental means as thin-section identifi- cation, SEM and X-ray diffraction has revealed that the sequence boundary along the Ruishui River outcrop profile controlled the sandstone reservoir and its diagenetic process, that the main matrix below the sequence boundary is aedelforsite, while that over the boundary is aedelforsite, and that the pores are mainly secondary pores formed by matrix dissolution. The area-porosity ratio is higher over the sequence boundary than below the boundary, which is favorable for the development of the reservoir.