满加尔坳陷西南部柯坪塔格组下段潮汐沉积特征

志留系柯坪塔格组下段是满加尔坳陷西南部重要的勘探层位之一,但前人对于这套产层的砂体沉积相仍然存在很大争议.在岩心观察的基础上,通过对薄片、粒度、测井和地震等资料的综合分析,结合前人对塔里木盆地志留系的研究成果认为,该区柯坪塔格组下段主要发育受潮汐控制的滨岸沉积体系,可识别出潮下带和潮间带2个亚相.潮下带进一步划分为潮汐砂坝和潮汐水道2个微相,潮间带自下而上划分为砂坪、混合坪、泥坪微相3个微相.纵向上砂体相互叠置,平面上环满加尔坳陷呈带状分布,储层物性受沉积微相控制,潮下带形成的潮汐砂坝和潮汐水道砂体物性相对较好,为最有利储集砂体.该研究成果将为该区储集相带预测、储层评价及下一步大规模勘探开发提供地质依据.

Depositional characteristics of tidal deposits for Lower Member of Kepingtage Formation in southwestern Manjiaer Depression

The Lower Member of Silurian Kepingtage Formation in the southwestern margin of Manjiaer Depression of Tarim Basin is one of the main exploration horizons.The sedimentary facies of the reservoir in the study area has long been under discussion.According to the comprehensive studies of core observation,well logging,grain size,thin section,well logging and seismic,and based on previous study on Silurian of Tarim Basin,it is considered that the kind of depositional system is mainly tide-controlled shore sedimentary system in the area.Two subfacies such as the subtidal zone and intertidal zone can be divided.Subtidal zone can further be divided into two microfacies such as tidal sand dam and tidal channel.Intertidal zone can be divided into three microfacies such as sand fiat,mixed flat and mud flat.In vertical direction,sand bodies are overlapped each other and are distributed within a linear zone along the Manjiaer Depression laterally.Reservoir is controlled by sedimentary microfacies.The tidal bar and tidal channel sandstones during progression with the better physical property are the most favorable reservoirs.This new understanding of the sedimentary facies type will be favorable for the prediction,evaluation and exploitation of reservoir facies belts in this area.