酒泉盆地鸭儿峡地区白垩系下沟组砂砾岩储层特征及主控因素

摘要

为了研究砂砾岩储层特征,以鸭儿峡白垩系下沟组(K1g)砂砾岩为研究对象,通过岩心、铸体薄片、阴极发光、扫描电镜及储层物性等相关资料分析,探讨了碎屑岩的宏观和微观储层特征及其影响因素.结果表明,研究区下沟组储层岩石类型以长石岩屑砂岩及岩屑砂岩为主,填隙物主要为白云石,结构及成分成熟度较低;储集空间主要为粒间(内)溶孔、残余原生粒间孔及特大孔,孔隙结构主要表现为细喉、微细喉特征;碎屑岩储层物性较差,孔隙度平均为7.68%,渗透率平均为4.92 mD,总体表现为特低孔—低孔、超低渗—特低渗特征;沉积、成岩及构造作用共同控制储层物性,其中细砂岩及含砾砂岩物性最优,扇三角洲前缘水下分流河道及河口坝均是最有利的微相类型,机械压实及胶结作用均导致储层物性变差,而长石、碳酸盐等可溶物的溶蚀及构造作用,共同改善了储层物性.研究结果可为该区油气勘探提供地质依据.%In order to study the characteristics of glutenite reservoir,the data of core,casting thin sections,cath-odoluminescence,scanning electron microscope and reservoir properties of glutenite of Cretaceous Xiagou For-mation(K1g)in Ya'erxia area were studied to discuss the macroscopic and microscopic reservoir characteristics and influencing factors of clastic rocks. The results show that the K1g reservoir rocks are mainly composed of feldspathic lithic sandstone and lithic sandstone,and the fillings are mainly dolomites,with low texture and com-position maturity.The pores are dominated by intergranular dissolved pores,intragranular dissolved pores,primary intergranular pores and super-macro pores,together with fine throat.The average porosity and permeability of the glutenite reservoir are 7.68% and 4.92 mD,respectively,showing the characteristics of low porosity and low permeability.The reservoir properties are controlled by sedimentation,diagenesis and tectonism.The favorable rock types are fine sandstone and pebbled sandstone,and the favorable sedimentary microfacies are mainly subaque-ous distributary channel and mouth bar in fan delta front.Compaction and cementation make the reservoir proper-ties poor,and dissolution of feldspar and carbonate and tectonism improves the reservoir properties.The study re-sults can provide geologic basis for oil and gas exploration in this area.