饶阳凹陷留北地区新近系河流相沉积模式

为了深入认识河流相储层分布规律,通过地层对比、沉积相、主控断裂特征等分析对饶阳凹陷留北地区新近系河流相砂体展布特征及影响因素进行了研究.结果表明:饶阳凹陷新近系各超短期旋回的砂体在平面上呈带状展布,砂体主要延伸方向与边部控洼断层大致平行.留北地区的NE向及NEE向主控断裂在新近纪仍表现为继承性生长的特征,受NE及NEE向近平行于盆地轴向的盆缘继承性主控断裂的影响,在下降盘形成大致平行于其轴向的河谷洼地、斜坡或山脊复合古地貌体系,断层上盘发育的沉降中心沿轴向延伸,地层厚度呈NE向展布.盆缘断层附近发育高梯度扇体或河流沉积,以沉积物的横向搬运体系为主.远离物源区,在主控断层下降盘,来自短轴物源的横向河流或冲积扇的影响变弱,河流向着轴向倾斜下端方向(最大斜坡方向)改道,汇聚形成轴向搬运沉积体系,平行于主要断层边界走向的方向延伸.

Neogene Sedimentary Models of Raoyang Sag in Liubei Area

To understand the distribution of fluvial reservoirs,we investigated the fluvial sand bodies’ characteristics and influencing factors of Neogene in Liubei area of Raoyang sag through combining the strata correlation,sedimentary facies,and main faults characteristics.The results showed that the sand bodies of the ultra short-term cycles of Neogene in Raoyang sag appeared as a belt distribution in plane,and the main extending direction was substantially paralleled to the boundary faults that controlled the depression.The main faults of NE and NEE in Liubei area still show the growing characteristics inherited from Neogene.Controlled by the inherited NE and NEE faults,the axis of the basin margin extended parallel to the faults;and the composited paleo-geomorphology system of valley depressions, slopes or ridges were formed substantially paralleled to the axis as the downthrown side.The subsidence center of the upthrow side extended axially;and the strata extended northeast.The high-gradient fan or fluvial sediments were deposited near the faults of the basin margin, and they were mainly transported laterally.Away from the provenance area,the influence of transverse fluvial or alluvial fan sediment from the short axis provenance was weakened in the downthrown side of the main faults. The rivers changed their course along the low end of the axial tilt direction (representing the maximum slope direction),and converged to form the sedimentary system of axial transport extending to the strike of the main fault boundary.