高分辨率层序地层学的应用——以鄂尔多斯盆地榆林长北气田山西组2段为例

以高分辨率层序地层学原理为指导,利用测井、钻井和野外露头剖面等资料,对鄂尔多斯盆地榆林长北气田山西组2段不同级次基准面旋回进行了详细划分,将山西组2段划分为1个长期、2个中期和5个短期基准面旋回.短期基准面旋回细分为两大类5种结构;中期基准面细分为两大类3种结构;长期基准面旋回为不完全对称型结构,区域分布较稳定.分析了不同级别的基准面旋回叠加式样与沉积相展布、演化规律之间的关系,中期基准面旋回上升半旋回开始阶段是辫状河三角洲河道砂体连续叠置形成巨厚砂体时期,洪泛面期及下降半旋回为细粒沉积物发育期.连续叠置的主水道和分支水道砂体形成了有利储层发育区,水下分流河道砂体与河口坝砂体构成了较好储层发育区.

Application of high resolution sequence stratigraphy: Case study of the second member of Shanxi formation in Yulin Changbei gas field, Ordos basin

Using the high resolution sequence stratigraphy theory and based on comprehensive study of logging, drilling and field outcrop profiles, different base-level cycles of the second member in Shanxi formation of Yulin Changbei gas field were detailed classified, including one long-term, two middle-term and five short-term base-level cycles. The short-term base-level cycles can be further divided into two types including five subtypes and the middle-term base-level cycles can be also divided into two types including three subtypes. The long-term base-level cycle is usually of dissymmetric structures and has stable areal distribution. The relationship between the stacking pattern of the base-level cycles with different orders and the distribution and evolution laws of sedimentary facies was analyzed. The beginning phase of the ascending half cycle in middle-term base-level cycle is the time to form tremendous-thick sand body by continuous superposition of braid river delta sand bodies. Flooding surface stage and the descending half cycle is the time to develop fine grained sediments. The continuous overriding sand bodies of main stream channel facies and branch channel facies form the potential reservoir-developing zone; the sand bodies of subwater distributary channel and mouth bar form good reservoir-developing zone