一种沿深水箕状谷纵向搬运的重力流沉积

REPLACED DEPOSITION OF GRAVITY FLOWS ALONG MOVING A DEEP WATER DUSTPAN THALWEG

姜在兴 赵徵林 刘孟慧

Jiang Zaixing Zhao Weiling Liu Mengbui

华东石油学院

East China Petroleum Institute

东濮凹陷西部早第三纪沙三段早期由于庆祖集断层和长垣断层的差异断裂活动,结果在二断层之间形成了一条走向与盆地长轴平行的箕状谷.重力流从南、北两个方向进入箕状谷后不能径直向前搬运,而是拐弯沿谷的延伸方向相向流动,形成拐弯纵向搬运的深水箕状谷重力流沉积.其鉴别标志是:1,沙体平面上呈带状或椭圆形,在走向上砂层向中间变薄,沉积物粒度虽有变细,但不十分显著;在横向上砂岩中间后、两侧薄,粒度也明显变细.2,在垂向层序上,向上变细的正韵律发育,显似二元结构.其沉积相包括水道和漫溢两个亚相和水道轴、点坝、近水道漫溢和远水道漫溢四个微相.其中的水道部分是最活跃的沉积单元,具迁移性.箕状谷重力流沉积是油气勘探的新领域.

In the early stage of the deposition of the 3rd Member of Tertiary,Shahejie Section,a dustpan thalweg developed between Qingzuji and Changheng faults due to differential faultings in western Dongpu Depression and the strike line of the thalweg paralled with the axial line of the depression.Since the gravity flows entered the dustpan thalweg from the opposite directions of south aud north,it had to be turned in direction and moved along the extensional trend of the thalweg.Therefore,the replaced deposition of the gravity flow developed,for which the recognized configuration is band or ellipsoid.1,Laterally,the sand sequences are quite thick at central part and thin out toward both sides with obvious changes in grain size.2,Vertically,the upper the sequence,the finer the grain size.The depositional facies includes channel and outflow subfacies with four microfacies of channel axis,point bar (bam),outflow near channel and outflow far from channel in which the channel microfacies are the most active depositional unit with moving feature.However,the replaced deposition of gravity flows is a frontier for oil/gas exploration.

https://doi.org/10.11781/sysydz198802106