鄂尔多斯盆地三叠系延长组砂质碎屑流储集体的首次发现

依据岩心、露头观察与分析测试及地震层序解释资料,在鄂尔多斯盆地湖盆中心深水区延长组长6段地层中识别出3种类型的重力流沉积物,即砂质碎屑流、经典浊积岩和滑塌岩。其中砂质碎屑流最为发育,而由浊流作用形成的经典浊积岩分布有限,以往延长组深水沉积研究夸大了浊流沉积作用。进一步研究认为,砂质碎屑流等深水重力流砂体平面分布及其物性变化主要受深水沉积坡折控制,总体而言,砂体物性坡上比坡下好,缓坡比陡坡好。从3种类型岩石的含油气性看,砂质碎屑流含油性最好,经典浊积岩A段含油性次之,而滑塌岩含油性较差。

First discovery of the sandy debris flow from the Triassic Yanchang Formation, Ordos Basin

Based on the large amount of the core data, field observations and analysis as well as seismic sequence interpretation, three kinds of sediment-gravity flows (the sandy debris flow, the classic turbidite and the slumps) were identified from the Chang 6 member of the Triassic Yanchang Formation in the deepwater area at the center of the ancient Ordos Basin lake, of which the sandy debris flow is dominant, whereas the classic turbidite is limited in distribution. The identification of sandy debris flow indicates previous study about deepwater sedimentation of the Yanchang Formation might overrate the turbidite sedimentation. Further study suggests that the distribution and the reservoir character of the deep water sediment-gravity flows sand bodies such as sandy debris flow are mainly controlled by the slope break. In general, the upper slope is better than the lower slope and the ramp is favorable than steep slope and consequently, sandy debris flow is the best oil prone, classic turbidite A section is moderate oil bearing and the slump is poor.