Origin and distribution model of thin dolomite reservoirs in the lower sub-member of Mao 2 Member of Middle Permian Maokou Formation in Wusheng-Tongnan area,Sichuan Basin,SW China  

作　　者：TAN Xiucheng HE Ruyi YANG Wenjie LUO Bing SHI Jiangbo ZHANG Lianjin LI Minglong TANG Yuxin XIAO Di QIAO Zhanfeng 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China [2]CNPC Key Laboratory of Carbonate Reservoirs at Southwest Petroleum University,Chengdu 610500,China [3]Sinopec Exploration Company,Chengdu 610041,China [4]Exploration and Development Research Institute,PetroChina Southwest Oil&Gas Field Company,Chengdu 610041,China [5]Exploration and Development Research Institute,CNPC Daqing Oilfield Company Limited,Daqing 163712,China [6]PetroChina Hangzhou Research Institute of Geology,Hangzhou 310023,China

出　　处：《Petroleum Exploration and Development》2025年第1期125-142,共18页石油勘探与开发(英文版)

基　　金：Supported by the National Natural Science Foundation of China(42172166);National Natural Science Foundation and CNPC Joint Fund Project(U23B20154);CNPC-Southwest Petroleum University Science and Technology Cooperation Project(2020CX010000).

摘　　要：This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation(lower Mao 2 Member)in the Wusheng-Tongnan area of the Sichuan Basin,SW China,through comprehensive analysis of geological,geophysical and geochemical data.The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone,which have typical karst characteristics of early diagenetic stage.The dolomites at the edge of the karst system and in the fillings have dissolved estuaries,and the dolomite breccia has micrite envelope and rim cement at the edge,indicating that dolomitization is earlier than the early diagenetic karstification.The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater.The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage,which are locally reformed by fractures and hydrothermal processes.The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence,and mainly occurs in the late highstand of the fourth-order cycle.Moreover,the size of dolomite is closely related to formation thickness,and it is concentrated in the formation thickness conversion area,followed by the thinner area.According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle,it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes,and the reservoir-forming model with shoal,dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established.On this basis,the paleogeomorphology in the lower Mao 2 Member is restored

关 键 词：reservoir origin sedimentary paleogeomorphology granular shoal thin reservoir DOLOMITE vuggy reservoir KARST Middle Permian Maokou Formation Sichuan Basin 

分 类 号：P61[天文地球—矿床学]