柴达木盆地西北部南翼山地区古近系下干柴沟组上段储层特征及主控因素  

Reservoir characteristics and main controlling factors of upper member of Paleogene Xiaganchaigou Formation in Nanyishan area,northwestern Qaidam Basin

作　　者：张振华 张小军[2,3] 钟大康[1] 苟迎春[2,3] 张世铭[2,3] ZHANG Zhenhua;ZHANG Xiaojun;ZHONG Dakang;GOU Yingchun;ZHANG Shiming(College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;PetroChina Research Institute of Petroleum Exploration and Development-Northwest,Lanzhou 730020,China;Key Laboratory of Reservoir Description,CNPC,Lanzhou 730020,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油勘探开发研究院西北分院,兰州730020 [3]中国石油天然气集团公司油藏描述重点实验室,兰州730020

出　　处：《岩性油气藏》2023年第3期29-39,共11页Lithologic Reservoirs

基　　金：中国石油股份公司重大专项“柴西地区石油勘探区带评价及目标优选”(编号:2016E-01-03)资助。

摘　　要：通过岩心观察、薄片鉴定和电子探针分析等多种实验手段,对柴达木盆地西北部南翼山地区古近系下干柴沟组上段储层特征及其主控因素进行了研究。研究结果表明:①南翼山地区下干柴沟组上段储层具有混积特征,以碳酸盐岩为主,平均质量分数为42.6%,含陆源碎屑、硬石膏和黏土矿物,平均质量分数分别为24.9%,9.0%和12.8%;储层的主要岩性为灰云岩、白云岩和藻灰岩,平均体积分数分别为49.0%,12.0%和6.0%。②研究区储层为低孔、特低渗储层,孔隙度为1.0%~13.3%,平均为4.9%,92%的样品渗透率小于0.02 mD;孔隙类型以溶蚀孔、晶间孔为主,发育微裂缝,但常被胶结物充填,连通性较差;按孔喉半径可分为中等喉道、细—中和细—微喉道3类,平均孔喉半径分别为0.350μm,0.110μm和0.030μm,占比分别为15%,40%和45%。③研究区主要为浅湖—半深湖亚相,可细分为灰云坪、藻席、砂坪及泥坪4种微相,储层的发育在宏观上受控于沉积微相,其中灰云坪储层占比最多,占储层总厚度的67%,藻席发育优质储层,藻灰岩厚度越大,储层的物性越好,而泥坪几乎不发育储层。④研究区储层在微观上受控于成岩作用和构造作用,准同生白云岩化作用、溶蚀作用及构造作用增加了储层的储集空间,改善了其渗透性,沉积后期的胶结作用对储层具有破坏性作用。By means of core observation,thin section identification and electron probe analysis,the reservoir characteristics and main controlling factors of the upper member of Paleogene Xiaganchaigou Formation(E_(3)^(2))in Nanyishan area of northwestern Qaidam Basin were studied.The results show that:(1)The reservoirs of E_(3)^(2) in Nanyishan area are characterized mixed sedimentation,dominated by carbonate rocks,with an average mass fraction of 42.6%,containing terrigenous clast,anhydrite and clay minerals,with the average mass fraction of 24.9%,9.0% and 12.8%,respectively.The lithologies of the reservoirs are mainly limestone,dolomite and algal limestone,with an average volume fraction of 49.0%,12.0% and 6.0% respectively.(2)The reservoir porosity in the study ranges from 1.0% to 13.3%,with an average of 4.9%,and 92% of the samples have permeability less than 0.02 mD,indicating low porosity and ultra-low permeability.The pores are mainly dissolved pores and intercrystalline pores,and microfractures are developed,but they are often filled with cements,and the connectivity is poor.According to the pore throat radius,the throat can be divided into three types:medium throat,fine-medium throat and fine-micro throat,and the average pore throat radii are 0.350μm,0.110μm and 0.030μm respectively,accounting for 15%,40% and 45% respectively.(3)The sedimentary subfacies in the study area is mainly shallow lacustrine to semi-deep lacustrine,which can be subdivided into four microfacies,namely,calcareous-dolomitic flat,algal mat,sand flat and mud flat.The development of reservoirs is closely related to sedimentary microfacies,of which the calcareous-dolomitic flat reservoir accounts for the largest proportion,accounting for 67% of the total thickness of the reservoir.High-quality reservoirs are developed in algal mat,and the thicker the algal limestone is,the better the physical properties of the reservoir are,while reservoir is hardly developed in mud flat.(4)The reservoirs in the study area are controlled by diagenesis and tec

关 键 词：混积岩 灰云坪 藻席 浅湖—半深湖亚相 准同生白云岩化作用 下干柴沟组上段 古近系 南翼山地区 柴达木盆地西北部 

分 类 号：TE122.2[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]