辽东湾西北部A区沙一、二段钻井层序地层和沉积相分析

Sequence stratigraphic and sedimentary facies analysis of the 1st and 2nd members of the Shahejie Formation in A district, northwestern Liaodong Bay

关键词:  辽东湾  沙一、二段  层序地层  沉积相分析

Key words:  Liaodong Bay  1st and 2nd members of the Shahejie Formation  sequence stratigraphic and sedimentary facies analysis

摘要:

利用辽东湾西北部A区6口井的录井、测井、岩心资料,通过细致的层序地层学及沉积学分析,将研究层段自下而上划分为SQs2和SQs1两个三级层序,每个层序均可划分出湖扩体系域(TST)和高位体系域(HST),并识别出三个层序边界和两个最大湖泛面,自下而上分别为SQs2底界面SBs2、最大湖泛面mfss2、SQs1底界面SBs1、最大湖泛面mfss1、SQs1顶界面SBd3。钻井揭示沙二段主要为砂岩、含砾砂岩,以粗碎屑岩发育为特征;沙一段主要为泥岩和白云岩,以泥岩发育为主要特征。研究区沉积相为湖泊相,滨浅湖亚相,微相发育泥滩、混合滩、砂质滩坝和钙质浅滩。低突起及其斜坡地区,在SQs2以混合滩沉积为主,在SQs1以泥滩沉积为主;陡坡地区,在SQs2发育砂质滩坝,在SQs1发育钙质浅滩。SQs2砂岩发育层段和SQs1的生物白云岩发育层段为良好的储层。

Abstract:

The 1st and 2nd members of the Shahejie Formation in A district, northwestern Liaodong Bay may be divided, on the core examination and sequence stratigraphic and sedimentary facies analysis, into two third-order sequences SQs2 and SQs1, each of which may be composed of the transgressive (TST) and high-stand (HST) systems tracts, three sequence bounding surfaces, and two maximum flooding surfaces including mfss2 and mfss1 in an ascending order. The sandstones, gravelly sandstones and coarse-grained clastic rocks appear in the second member, and mudstones and dolostones occur in the first member of the Shahejie Formation. Sedimentary facies are assembled by lake, littoral-shallow lake subfacies, and mud flat, mixed beach, sandy beach and calcareous beach microfacies. In the sequence SQs2, there occur the mixed beach and sandy beach deposits in which the sandstones serve as the excellent reservoir rocks. In the sequence SQs1, there occur the mud flat deposits in which the biogenic dolostones act as the excellent reservoir rocks.