松辽盆地他拉哈西地区下白垩统青山口组下部沉积微相分析

Sedimentary microfacies in the lower part of the Qingshankou Formation in the Talin Hiag region,northern Songliao Basin

关键词:  沉积微相|青山口组|沉积相分析|松辽盆地

Key words:  sedimentary microfacies|Qingshankou Formation|sedimentary facies analysis|Songliao Basin

摘要:

笔者通过观察岩心,结合测井、录井资料,采用沉积学最新分析方法,查明了主要研究层青山口组(K₁qn)下部发育的沉积微相类型及其特征,建立了相标志,同时查明了不同体系域沉积相、亚相、微相的空间展布。研究层段发育的沉积类型有湖泊相和湖底扇相,湖泊相主要为半深湖-深湖亚相,湖底扇相区分为内扇和外扇两个亚相。通过单井相划分和3条不同方向的联井剖面查明沉积微相在纵向上的变化,利用沉积微相平面分布图分析了研究区各沉积微相的平面分布特征。纵向上研究层段底部湖底扇较发育,向上湖底扇的面积逐渐减小。平面上,以深湖-半深湖沉积为主,在研究区的西侧、西南和西北地区发育湖底扇。湖底扇具有多期性、多物源的特点。该区的主体砂岩为碎屑流、浊流成因的湖底扇砂,其典型特征是厚层暗色的深湖-半深湖亚相的烃源岩夹由重力流成因的湖底扇,上下均呈突变接触关系,具有很好的隐蔽油藏成藏的条件。

Abstract:

The present paper deals,in detail,with sedimentary microfacies types,and criteria for the recognition and spatial distribution of facies,subfacies and microfacies developed in the lower part of the Qingshankou Formation in the Talin Hiag region,northern Songliao Basin.The sedimentary facies in the study area consist of the lacustrine facies including the semi-deep lacustrine to deep lacustrine subfacies,and sublacustrine fan facies including the inner fan and outer fan subfacies.Longitudinally,the sublacustrine fan facies is mostly developed at the base of the studied intervals,and gradually decreases in area upwards.Viewed from the planar distribution,the semi-deep lacustrine to deep lacustrine deposits are accentuated.The sublacustrine fan deposits mostly occur in the western,southwestern and northwestern parts of the study area,and have multiphase and polygenic features of origins.The bulk of the sandstones are made up of the debris flow and turbidity current sublacustrine fan sandstones.The dark thick-bedded source rocks in the semi-deep lacustrine to deep lacustrine subfacies are intercalated with the gravity flow sublacustrine fan deposits,between which there is a sharp contact,constituting the good hydrocarbon reservoirs of concealed oil accumulation.