渤海东部庙北地区古近系层序与沉积特征

Sequence and Sedimentary Characteristics of Paleogene in Miaobei Area,East Bohai Bay

综合壁心、薄片、钻井和三维地震等资料分析渤海东部庙北地区古近系层序与沉积特征,并运用地震相、古地貌和地震属性刻画沉积体系平面展布。研究表明,古近系由1个二级层序、4个三级层序组成,经历了一个完整的湖泊初始发育、扩张及萎缩阶段,主要发育扇三角洲、碳酸盐岩浅滩、半深湖-深湖、辫状河三角洲等沉积体系。不同的沉积体系形成于不同的湖泊演化阶段,地震响应特征也不同。扇三角洲和碳酸盐岩浅滩发育于湖泊初始发育阶段,扇三角洲表现为填充型楔形前积反射,沿凸起边缘断坡带呈朵状分布;碳酸盐岩浅滩表现为水进型丘形叠瓦状反射,呈椭圆状分布于水下古隆起带上,椭圆的长轴方向平行于水下古隆起带走向;半深湖-深湖相暗色泥岩发育于湖泊扩张期,表现为平行连续中弱振幅反射,在庙西北洼和渤东凹陷深陷带最为发育;辫状河三角洲发育于湖泊萎缩期,表现为低角度中高频、中弱振幅前积反射,沿凸起边缘挠曲坡折带呈朵叶状分布。庙北地区油气显示普遍,这种沉积体系识别与刻画结果对于该区油气勘探具有重要意义。

Based on cores,logging and seismic data,the sequence and sedimentary characteristics of Paleogene in Miaobei area in East Bohai Bay were analysed.The planar distribution of sedimentary systems were described by analyzing seismic facies,paleogeomorphic and seismic attributes.It showed that Paleogene were made up by one second-order sequence and four third-order sequences,in which fan delta,carbonate bank,braided delta,semi-deep-deep lake and so on developed well.It also experienced the whole lake initialing,expanding and dwindling evolution stage.Different sedimentary system developed at different lake evolution stage,and showed different seismic reflection characteristics.Fan delta and carbonate bank developed at lake initialing stage.Fan delta showed as wedge progradation reflection and distributed as lobe along salient peripheral fault-slope belt.Carbonate bank showed as mound-imbricate reflection of transgression model and distributed as ellipse along underwater uplift zone,of which the longest axes parallel to the trend of underwater uplift zone.The dark mudstone of semi-deep lake showed as parallel middle-high amplitude reflection and mainly distributed in deep subsidence belt.Braided delta developed at lake dwindling stage.It shows as low-angle,middle-high frequency and middle-weak amplitude progradation reflection.It distributed as lobe along salient peripheral flexure slope break.The hydrocarbon showed of Miaobei area was very popular.These results of sedimentary system identification and characterization had important meaning for looking for petroleum exploration in Paleogene.