Characteristics and origin of low-organicmatter carbonate source rocks in the Middle-Upper Ordovician, Tarim Basin, northwestern China  

作　　者：Jun-Qing Chen Fu-Jie Jiang Xiong-Qi Pang Hai-Jun Yang Kan-Yuan Shi Bo Pang Hong Pang Jian-Fa Chen Zhuo-Heng Chen Xin-Gang Zhang Song Wu 

机构地区：[1]State Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China [2]Basic Research Center for Energy Interdisciplinary,College of Science,China University of Petroleum(Beijing),Beijing 102249,China [3]Beijing Key Laboratory of Optical Detection Technology for Oil and Gas,China University of Petroleum(Beijing),Beijing 102249,China [4]College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China [5]Research Institute of Petroleum Exploration and Development,PetroChina Tarim Oilfield Company,Korla 841000,Xinjiang Uygur Autonomous Region,China [6]Geological Survey of Canada,Natural Resources Canada,Calgary T2L 2A7,Canada

出　　处：《Journal of Palaeogeography》2024年第3期594-619,共26页古地理学报（英文版）

基　　金：supported by the Joint Funds of National Natural Science Foundation of China(Grant number U19B6003-02-04);the CNPC Science and Technology Major Project of the Fourteenth Five-Year Plan(Grant number 2021DJ0101);the Science Foundation of China University of Petroleum(Beijing)(Grant number 2462022YXZZ007).

摘　　要：The continually-discovered large volumes of marine hydrocarbons indicate a huge exploration potential within the carbonate rocks of Ordovician in the Tarim Basin,northwestern China.The Middle-Upper Ordovician(O2+3)carbonate source rocks are at a highly mature stage.These rocks presently contain a low amount of total organic carbon(TOC_(pd)≤0.5%)(TOC_(pd) means the present-day TOC).A mass balance approach is used to identify the source rocks that have expelled hydrocarbons.The characteristics and origin of hydrocarbon expulsion from low-TOC_(pd) source rocks are studied,which are significant for oil exploration in the basin.The results showed that a low-TOC_(pd) O2+3 source rock having expelled hydrocarbons was type I and had a very narrow oil window.With a high rock maturity and a high original TOC(TOCo)value exceeding 1%,nearly 80%of the generated hydrocarbons were expelled.The content of gammacerane and C28 steranes in the oil and source rock extracts were relatively lean,with a V-shaped distribution of regular steranes,suggesting a possible genetic relation between the low-TOC_(pd) source rocks and the marine oil in the Tabei area.Hydrogenrich planktonic algae or acritarchs were the main hydrocarbon parent materials,distributed in the subsiding platform-slope facies.Organic matter was preserved under reducing conditions,and source rocks were formed with a favorable kerogen type and a moderate hydrocarbon generation potential.This study illustrates the hydrocarbon expulsion of low TOC_(pd) source rocks in northern Tarim Basin,which is greatly significant for analyzing the genesis of marine crude oil in Tarim Basin,and evaluating the distribution of marine source rocks.This research method is theoretically significant for oil and gas exploration in the same type of highlymature carbonate paleobasins.

关 键 词：Carbonate source rock Mass balance approach Present-day TOC Genesis mechanism Tarim Basin 

分 类 号：P618.13[天文地球—矿床学]