浅水湖盆河控三角洲短期基准面旋回结构样式与沉积演化:以松辽盆地扶新隆起带南部扶余油层为例

Sedimentary evolution and structure types of short-term base-level cycle sequences of shallow lacustrine fluvial-dominated delta: Example of Fuyu oil layer in southern Fuxin uplift of Songliao Basin

利用22口取心井岩心资料和830口井的录井、测井资料,系统分析松辽盆地扶新隆起带南部扶余油层浅水湖盆河控三角洲体系的短期基准面旋回界面类型、成因特征、结构样式及分布模式,总结出扶余油层的沉积层序演化模式。研究结果表明:(1)扶余油层短期基准面旋回界面类型主要有基准面下降至基准面上升转换面、基准面上升至基准面下降转换面和基准面旋回界面对比局部参照等时面;(2)短期基准面旋回结构样式可分为3大类7亚类,即向上"变深"非对称型旋回(可分为2亚类)、向上"变浅"非对称型旋回(可分为2亚类)和对称型旋回(可分为3亚类),以向上"变深"非对称型旋回为主;(3)扶余油层划分为1个长期基准面旋回的上升半旋回、4个中期基准面旋回、13个短期基准面旋回,其在总体水进的背景下,主要经历4个变化阶段:早期的缓慢上升阶段、中期的快速上升阶段、中后期的缓慢上升阶段及末期的快速上升后略有下降阶段,近似对应于识别出的4个中期基准面旋回层序。在这4个阶段的变化过程中,依次发育高能河控三角洲分流平原、低能河控三角洲平原、河控三角洲分流平原近岸沉积区及三角洲前缘前三角洲沉积。

With the data of 22 well cores and 830 logging data analysis was done on the interface types, genetic characteristics distribution pattern and structure types of short-term cycle in shallow lacustrine fluvial-dominated delta in Fuyu oil layer of the southern Fuxin uplift, Songliao Basin, China. And sedimentary sequence evolution model of Fuyu oil layer was summarized. The results show that interface types of short-term base-level cycles in the Fuyu oil layer are base-level fall to base-level rise turnaround surface, base-level rise to base-level fall turnaround surface and correlation of base-level cycle local reference isochronous surface. The short-term base-level cycles are divided into three basic structure types which are up-deepening non-symmetry, up-shallowing non-symmetry and symmetry from up-deepening to up-shallowing. In the light of the high or low accommodation, and the thickness of the uprising periods and subsiding periods of the short-term base-level cycle, seven subtypes of structure are distinguished and they are up-deepening non-symmetry of low accommodation or high accommodation, up-shallowening non-symmetry of low accommodation or high accommodation, complete-nearly complete symmetry, in complete symmetry with the majority of uprising semi-cycle or subsiding semi-cycle. Up-deepening non-symmetry cycle is the main. One long-term, four middle-term and about thirteen short-term base-level cycle sequences from Fuyu oil layer are classified. In the transgressive background, Fuyu oil layer mainly experienced four stages, early to rise slowly stage, middle to rise quickly stage, middle and later to rise slowly stage, end to rise quickly and fall slightly stage, which approximately correspond to the identified four middle-term base-level cycle sequence. During the four stage, Fuyu oil layer are developed successively in high fluvial-dominated delta distributary plain, low fluvial-dominated delta plain, coastal deposition area of fluvial-dominated delta distributary plain and delta front - pro-delta deposition.