Genesis of ultra-deep dolostone and controlling factors of largescale reservoir:A case study of the Sinian Dengying Formation and the Cambrian Longwangmiao Formation in the Sichuan Basin  

作　　者：Xi LI Guangyou ZHU Zhiyao ZHANG 

机构地区：[1]PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China [2]School of Geosciences,Yangtze University,Wuhan 430100,China [3]School of Earth Resoures,China University of Geosciences,Wuhan 430074,China

出　　处：《Science China Earth Sciences》2024年第7期2352-2382,共31页中国科学（地球科学英文版）

基　　金：supported by the Scientific Research and Technological Development Project of China National Petroleum Corporation(Grant No.2021DJ05)。

摘　　要：This paper investigates the origin of ultra-deep dolostone and the factors influencing large-scale dolostone reservoirs,focusing on the Sinian Dengying Formation and the Cambrian Longwangmiao Formation in the Sichuan Basin.The study involves petrology,microscale X-ray diffraction,trace element analysis,and C-O-Sr-Mg isotope experiments to provide a detailed analysis.The research findings indicate that the Dengying and Longwangmiao formations comprise six types of matrix dolostone and four types of cement.The Dengying Formation,which developed under a sedimentary background of a restricted platform,contains special microbial and microcrystalline dolostones.The dolomite grains are small(<30μm)and have a low order degree(Min=0.55),with large unit cell parameters and an extremely high Na content(Max=788 ppm).The^(87)Sr/^(86)Sr value of the dolostone is consistent with contemporaneous seawater,while the δ^(13)C andδ^(18)O values are lower than those of the contemporaneous seawater.The δ^(26)Mg value is small(Min=-2.31‰).Powder crystal,fine-crystalline,and calcite dolostones with coarser and more ordered crystals exhibit similar δ^(13)C and^(87)Sr/^(86)Sr values to microbial and microcrystalline dolostone.During the sedimentary period of the Dengying Formation,ancient marine conditions were favorable for microbial survival.Microorganisms induced the direct precipitation of primary dolomite in seawater,forming microbial and microcrystalline dolostones during the seawater diagenesis period.During the subsequent diagenesis period,dolostones underwent the effects of dissolution-recrystallization,structures,and hydrothermal fluids.This resulted in the formation of dolostone with coarser crystals,a higher degree of order,and various types of cement.The Longwangmiao Formation was developed in an interplatform beach characterized by special particle dolostone.The particle dolostone has a large grain size(>30μm),high order degree(Min=0.7),small unit cell parameters,high Na content(Max=432 ppm),and low Fe and Mn content.

关 键 词：Ultra-deep layers DOLOSTONE Supercontinent evolution Microscale geochemistry Dengying Formation Longwangmiao Formation Sichuan Basin 

分 类 号：P618.13[天文地球—矿床学]