陕北地区上三叠统延长组层序地层格架内岩性油气藏分析

Analysis of litho-stratigraphic reservoirs distribution in sequence stratigraphic at the upper triassic Yanchang formation in northern Shanxi

应用高分辨率层序地层学的原理和方法,综合露头、钻井、岩芯以及测井资料,在鄂尔多斯盆地陕北地区延长组长7-长4+5识别出长61底部为三级基准面旋回的层序界面,并划分出1个三级基准面下降半旋回与1个三级基准面上升半旋回,由此建立露头与井下高分辨层序地层格架;通过地层充填序列和基准面的变化关系,构建大型坳陷湖盆高分辨率层序地层格架内砂体的分布模型;在层序地层格架内对岩性油气藏的分布进行分析预测。研究结果表明:层序的演化对岩性油气藏的发育起控制作用;基准面旋回下降期和层序界面附近是有利的岩性油气藏分布区。

According to the theory and approach of the high resolution sequence stratigraphy, combined with outcrops, drilling, well core and well-logging, the sequence boundary at the bottom of the Chang 61 was identified. The high resolution sequence stratigraphy of outcrops and wells was built, too. Based on the relation of strata filling sequence and the changing of base-level, a sandbody distribution model in high resolution sequence stratigraphy of large-scale depression basin was built. After studying the distribution of litho-stratigraphic reservoirs in sequence stratigraphic, it is found that there is a semi-rising cycle and a semi-downing cycle 3rd base-level in the upper Triassic Yanchang formation Chang 7-Chang 4＋5 in the north of Shaanxi of Ordos Basin. The development of litho-stratigraphic reservoirs is controlled by the changing of sequence. Beneficial area of litho-stratigraphic traps lie in the sequence of semi-downing base level and beside the sequence boundary（SB）.