三塘湖盆地马朗凹陷西山窑组层序地层及沉积相研究

Sequence Stratigraphy and Sedimentary Facies of Xishanyao Formation in Malang Depression,Santanghu Basin

马朗凹陷是三塘湖盆地的富油凹陷之一,具有多样的成藏类型和巨大的油气勘探潜力.运用岩心、测井、录井等资料,对研究区马朗凹陷西山窑组进行层序地层划分和沉积相研究.研究表明,马朗凹陷西山窑组为一个长期旋回,发育1个三级层序(JSQ_2),进一步识别出3个四级层序界面(sb_4、sb_5、sb_6),并将其划为2个四级层序(SC_4、SC_5).通过研究,认为马朗凹陷西山窑组发育冲积扇、扇三角洲、辫状河三角洲、湖泊四种主要的沉积相.其中,辫状河三角洲相是最主要的沉积相,辫状河三角洲平原分流河道、辫状河三角洲前缘水下分流河道、河口坝、远砂坝等为广泛发育的主要沉积微相.

Malang Depression is one of the oil-rich sags in Santanghu Basin,which has diversiform pool-formingtypes and enormous oil-gas exploration potential. Comprehensively applying data of core,logging,mud logging,etc,sequence stratigraphic division and sedimentary facies characteristics of Xishanyao Formation,are studied,in MalangDepression. The study shows that Xishanyao Formation of Malang Depression is a long-term cycle,namely it developsone three-level sequence(JSQ_2). Besides,three four-level sequence boundaries are recognized,therefore XishanyaoFormation can be further divided into two four-level sequences(SC_4,SC_5). Four kinds of primary sedimentary faciesare identified in Xishanyao Formation of Malang Depression,including alluvial fan,fan delta,braided river deltaand lake. Among these,the braided river delta is the most significant sedimentary facies,which mainly develops twosub-facies:braided river delta plain and braided river delta front. The braided river delta widely developsfollowing sedimentary microfacies:distributary channel,underwater distributary channel,mouth bar and distal bar.