鄂尔多斯盆地环县地区延安组高分辨率层序地层学特征

High Resolution Sequence Stratigraphic Characteristics of Yanan Formation InHuanxian County of Ordos Basin

运用高分辨率层序地层学理论及方法,研究了鄂尔多斯盆地环县地区三叠系延安组不同级次的基准面旋回层序的界面特征、结构类型、叠加样式及空间分布模式、A/S变化对储集砂体的控制作用.结果表明:鄂尔多斯盆地环县地区延安组由3个长期、8个中期、36个短期基准面旋回层序组成,且存在向上变"深"非对称性(A型),向上变"浅"非对称型(B型)以及向上变"深"复变"浅"的对称旋回(C型)3种型式的中短期基准面旋回层序结构.沿三角洲生长轴向方向,旋回层序结构型式呈由A型-C型-B型变化.在旋回层序界面叠合部位及旋回下部为储层砂体发育有利部位.

Guided by the theory and method of high-resolution sequence stratigraphy, the datum plane cycle sequence of all levels in Yanan Formation of Triassic in Huanxian county was researched and the interface characteristics, structural types, superimposition mode, spatial distribution, and the control of A/S over the reservoir are discussed. The results indicate that 1) the Yanan Formation of this area is consisted of three long-term datum plane cycle sequences, eight middle-term datum plane cycle sequences, and thirty-six short-term cycle sequences; 2) there exists three typs of middle-short term datum plane cycle sequence structure types, which are upward deepening non-symmetric-type (mode A), upward shoaling non-symmetric-type(mode B), and symmetric-type with upward deepening first and then shoaling (mode C); 3) along the extending direction of this delta, the cycle sequence structure type changes from mode A to mode C, and then mode B. The advantageous place of reservoi0r is usually the superposition part and the lower part of cycle sequences.