梨树断陷营城组层序地层格架与沉积相特征

Framework of Sequence Stratigraphy and Depositional Characteristics of Yingcheng Formation in Lishu Fault Depression

以Vail层序地层学理论为指导,综合利用地震、岩芯、测井及其他资料,通过多种方法,建立了梨树断陷营城组层序地层格架,有力地验证了前人提出的该工区存在4个三级层序的观点,认为由下至上所发育的SQ1~SQ4四个三级层序,分别对应YC1、YC2、YC3、YC4段地层。其中,底部SQ1~SQ3为二分层序,发育湖侵域和湖退域,SQ4为一分层序,仅发育湖侵域。针对研究区目的层段的层序发育特点,在层序地层单元划分和对比的基础之上,对层序格架内的沉积相类型和沉积相展布规律进行了研究,确定研究区主要沉积相类型包括湖泊相、扇三角洲相和辫状河三角洲相等,且沉积砂体具有混源沉积、连片发育的特征。SQ1层序,整个工区发育扇三角洲沉积相;SQ2层序,研究区东部继承发育扇三角洲沉积相,北部则演变为辫状河三角洲沉积相;SQ3、SQ4层序,研究区整体演变为辫状河三角洲沉积相。

Based on the sequence stratigraphy theory of Vail,sequence stratigraphy framework of Yingcheng Formation in Lishu fault depression is established through analysing seismic data,core data,logging data and other materials.Yingcheng Formation is divided into 4 3rd-order sequences from the bottom to the top,SQ1,SQ2,SQ3,SQ4,which are,respectively,equal to YC1,YC2,YC3,YC4 stages.SQ1-SQ3 at the bottom are T-R sequences,and SQ4sequence is composed of transgressive system.According to the characteristics of sequence development of target strata in the study area,and based on the division and comparison of sequence formation unit,this paper studies on sedimentary types and its distribution law.This area mainly develops fan delta and braided river delta,which are characteristicted by mixed-source sedimentary and regional distribution.The whole area develops fan delta in SQ1; SQ2 exits fan delta in the east area and braided river delta in the north area of the depression.The sedimentary facies evolved to braided river delta within the scope of whole depression in SQ3 and SQ4 sequences.