鄂尔多斯盆地富县地区三叠系延长组长8—长6油层组类眼状构造成因探讨

鄂尔多斯盆地富县地区的三叠系延长组长8—长6油层组的岩石中发育类眼状构造。研究表明,类眼状构造由外部圈层和核心砂质团块组成,根据其形态特征和运动学特征,可分为侧向挤压、鞘褶皱横截面和垂向液化升降3种成因类型。结合古构造及古地理背景,对类眼状构造及相关软沉积变形构造的触发机制进行判别,由于长8—长6沉积时期湖盆处于扩张—收缩转换期,受同期秦岭造山带活动影响,构造运动活跃,地震频发,故认为地震及地震—涌浪作用最有可能形成类眼状构造及相关软沉积变形构造。鉴于类眼状构造存在于与深水块状砂岩相伴生的块状砂岩中,近年来被重新解释为砂质碎屑流的产物,进一步研究两者之间成因及沉积展布关系,对于研究区深水岩性油气藏勘探具有重要意义。

Genetic discussion about eye-like structure of the Chang 8-6intervals of Triassic Yanchang Formation in Fuxian area,Ordos Basin

Eye-like structure was developed in the cores of the Chang 8-6 intervals of Triassic Yanchang Formation in Fuxian area. The eye-like structure consists of external layers and sandy core. According to the geometry and kinematics,the eye-like structures in the research area can be classified as three kinds: lateral compression,the cross section of sheath fold and vertical liquidation. Combined with palaeotectonics and palaeogeography,earthquake was prone to happen because of the basin transition from expansion to contraction and the impaction of the Indosinian Movement in Qinling orogeny. So it suggests that earthquake or earthquake/seismic surge wave was the most possible trigger for the eye-like structure and associated structures. The eye-like soft sediment deformation is associated with massive sandstone,which has been explained as the product of sandy debris flow. Thus further research about the relationship between the two phenomena will be helpful for the oil exploration of lithologic oil-gas reservoir of the research area.