济阳坳陷新近系层序地层构型

Model of sequence stratum of Neogene of Jiyang depression

济阳坳陷新近系是重要含油气层位之一,但由于研究区内油气分布极不均衡,使得区内不同部位研究程度差异较大,缺乏整体性和系统性。根据沉积学、层序地层学基本理论以及地质、地球物理等资料,对全区进行了层序地层构型的系统研究。结果表明,研究区冲积-河流相地层的体系域构型包括4部分,即低位体系域、扩张体系域、高位体系域和收缩体系域。低位体系域主要发育冲积扇-辫状河沉积;扩张体系域发育辫状河向曲流河过渡沉积;高位体系域主要发育曲流河沉积,其泛滥平原亚相广泛分布;收缩体系域发育曲流河向辫状河过渡沉积。在不同沉积背景下,同一时期的相同类型体系域中发育的沉积类型及沉积体系不同,陡坡带发育冲积扇-辫状河体系,缓坡带发育小型扇及扇前洪泛平原-间歇河道体系。准层序组类型与经典层序地层学中的类型相似,但是其内部各准层序以正韵律为主。

The Neogene is one of main target strata of oil and gas exploration in Jiyang depression. As the disproportion of oil and gas distribution, there is obvious disaccord of degree of exploration and researching between different areas. Synthetically investigating indicates that according to the principle of sedimentology and sequence stratigraphy, data of geology and geophysics, there are 4types of system tracts in alluvial-fluvial facies： lowstand system tract, extension system tract,highstand system tract ,contraction system tract in Jiyang depression. The model of sequence stratum of alluvial-fluvial facies was built. The types of sediment systems and facies were pointed out correspond to different system tracts, as following：alluvial-braided river facies in lowstand system tract; transition from braided river to meandering river in extension system tract; meandering river in the highstand system tract; transition from meandering fiver to braided river in the contraction system tract. In same period, there are different sedimentation type and depositional system in distinct depositional setting. There are alluvial fan and braided fiver in steep slope and small-size alluvial fan, bet lands and intermittent river channel in gentle slope. The type of parasequence sets is similar to classic sequence stratigraphy, and the parasequence mainly consists of positive rhythm.