Episodic hydrothermal alteration on Middle Permian carbonate reservoirs and its geological significance in southwestern Sichuan Basin,SW China  

作　　者：FENG Mingyou SHANG Junxin SHEN Anjiang WEN Long WANG Xingzhi XU Liang LIANG Feng LIU Xiaohong 

机构地区：[1]School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China [2]PetroChina Hangzhou Institute of Petroleum Geology,Hangzhou 310023,China [3]Research Institute of Exploration and Development,PetroChina Southwest Oil&Gas filed Company,Chengdu 610041,China

出　　处：《Petroleum Exploration and Development》2024年第1期81-96,共16页石油勘探与开发（英文版）

基　　金：Supported by the National Science and Technology Major Project(2016ZX05007004-001);Innovation Fund Project of CNPC Carbonate Rock Key Laboratory(RIPED-HZDZY-2019-JS-695).

摘　　要：To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The fractures and vugs of Middle Permian Qixia–Maokou formations are filled with multi-stage medium-coarse saddle dolomites and associated hydrothermal minerals,which indicates that the early limestone/dolomite episodic alteration was caused by the large-scale,high-temperature,deep magnesium-rich brine along flowing channels such as basement faults or associated fractures under the tectonic compression and napping during the Indosinian.The time of magnesium-rich hydrothermal activity was from the Middle Triassic to the Late Triassic.The siliceous and calcite fillings were triggered by hydrothermal alteration in the Middle and Late Yanshanian Movement and Himalayan Movement.Hydrothermal dolomitization is controlled by fault,hydrothermal property,flowing channel and surrounding rock lithology,which occur as equilibrium effect of porosity and permeability.The thick massive grainstone/dolomites were mainly altered by modification such as hydrothermal dolomitization/recrystallization,brecciation and fracture-vugs filling.Early thin-medium packstones were mainly altered by dissolution and infilling of fracturing,bedding dolomitization,dissolution and associated mineral fillings.The dissolved vugs and fractures are the main reservoir space under hydrothermal conditions,and the connection of dissolved vugs and network fractures is favorable for forming high-quality dolomite reservoir.Hydrothermal dolomite reservoirs are developed within a range of 1 km near faults,with a thickness of 30–60 m.Hydrothermal dolomite reservoirs with local connected pore/vugs and fractures have exploration potential.

关 键 词：Sichuan Basin PERMIAN Middle Permian Qixia Formation Middle Permian Maokou Formation hydrothermal fluid hydrothermal dissolution DOLOMITE 

分 类 号：P618.13[天文地球—矿床学]