Reservoir Characteristics of Fine-grained Sedimentary Rocks in Saline Lakes in the Cenozoic Upper Ganchaigou Formation,Southwestern Qaidam Basin,NW China

作     者：SHENG Jun LIU Jincheng LI Yunlong ZOU Haiyan LONG Anlin WANG Lin LI Jiyong QI Qingshan YANG Xiaojing LI Yanan SHENG Jun;LIU Jincheng;LI Yunlong;ZOU Haiyan;LONG Anlin;WANG Lin;LI Jiyong;QI Qingshan;YANG Xiaojing;LI Yanan

作者机构：Exploration&Development Research Institute of PetroChina Qinghai Oilfield CompanyDunhuangGansu 736200China No.2 Oil Production Plant of PetroChina Qinghai Oilfield CompanyDunhuangGansu 736200China No.1 Oil Production Plant of PetroChina Qinghai Oilfield CompanyDunhuangGansu 736200China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2022年第96卷第3期

页      面：1070-1081页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 0708[理学-地球物理学] 

基　　金：This work is supported by the Science and Technology Project(Grant No.2019k02)of CNPC Qinghai Oilfield Company. 

主　　题：energy resources unconventional reservoir sedimentary petrology organic geochemistry salinization lacustrine sediments Neogene 

摘      要：Cenozoic fine-grained sedimentary rocks in the southwestern Qaidam Basin,as typical salinized lacustrine sediments,are significantly different from those in other freshwater lakes under the impact of the high salinity in the lake.Many fine-grained sedimentary rock samples were selected from the lower member of Neogene(N_(1))in the Gaskule Oilfield,Qaidam Basin,northwest China,with the aim to analyze and test their petrology,pore structure,and organic geochemical characteristics and determine its genesis and geological significance.Based on previous results,a new genesis of mixed sedimentary rocks is proposed.The Cenozoic lacustrine fine-grained sedimentary rocks in SW Qaidam Basin belong to mixed sedimentary rocks,which can be divided into three types,including carbonate and terrigenous clastic-bearing mudstone,carbonate-bearing to terrigenous clastic mixed sedimentary rocks,and carbonate-terrigenous clastic mixed sedimentary rocks.The geneses of mixing are quite different from that of mixed marine rocks.According to the sedimentary characteristics of the salinized lakes,three new geneses of mixed deposits are proposed:syn-sedimentary mixing,varve interbedded mixing,and biogenic mixing.The reservoir spaces of the Cenozoic lacustrine fine-grained sedimentary rocks in SW Qaidam Basin include residual intergranular pores,intercrystalline pores,microfractures,and minor dissolved pores.The reservoirs have super-low porosity and ultra-low permeability,with a porosity of 1.82%-21.04%,averaging 7.71%,and permeability of(0.0028-254.86)×10^(−3)μm^(2),averaging 2.82×10^(−3)μm^(2).The test results of total organic carbon(TOC)content show that the highest content of organic carbon reached 1.41%,and those of vitrinite reflectance show that Ro ranges from 0.525%-0.824%,with an average of 0.806%.The organic geochemical characteristics show that the fine-grained mixed sedimentary rocks of SW Qaidam Basin have the potential for self-generation and self-storage.As an unconventional reservoir,it has potential industrial value.This is the first study of fine-grained sedimentary rocks in the Qaidam Basin,which offers certain theoretical and practical values.