Tectono-sedimentary evolution and oil-gas geological significance of first to third member of Ordovician Majiagou Formation in Ordos Basin,NW China  

作　　者：ZHONG Shoukang TAN Xiucheng WEI Liubin XU Jie WANG Qianping XIONG Ying WU Chunying DU Jiansheng 

机构地区：[1]Sichuan Key Laboratory of Natural Gas Geology,Southwest Petroleum University,Chengdu 610500,China [2]CNPC Key Laboratory of Carbonate Reservoirs Southwest Petroleum University Division,Chengdu 610500,China [3]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China [4]Exploration and Development Research Institute,PetroChina Changqing Oilfield Company,Xi’an 710018,China [5]The Fourth Gas Production Plant,PetroChina Changqing Oilfield Company,Xi’an 710016,China

出　　处：《Petroleum Exploration and Development》2024年第5期1202-1216,共15页石油勘探与开发（英文版）

基　　金：Supported by the National Natural Science Foundation of China(NSFC)Youth Science Fund Project(42302139);Graduate Research Innovation Fund Project of Southwest Petroleum University(2022KYCX032)。

摘　　要：Based on logging,core,thin section and geochemical analysis,the tectonic-lithofacies paleogeographic pattern of first member to third member of Ordovician Majiagou Formation(O_(1)m_(1)–O_(1)m_(3)for short)in Ordos Basin is reconstructed,and the tectono-sedimentary evolution characteristics and oil-gas geological significance are discussed.The results are obtained in four aspects.First,a set of marginal argillaceous dolomites with high gamma ray value developed steadily and diachronously at the bottom of Majiagou Formation,which distributed over the Huaiyuan Movement unconformity,with δ^(13)C values positive drift characteristics comparable to global transgression of the Early Ordovician Floplian.Second,the global sea level rose and the ancient land was submerged into the underwater uplift in O_(1)m_(1)to O_(1)m_(2),and the central uplift was deposited for the first time in the Ordovician,forming a tectonic pattern of“one uplift and two depressions”.Subsequently,the subduction and extrusion outside the basin and the differentiation of uplift and depression in the basin of O_(1)m_(3)resulted in the activation of the Wushenqi–Jingbian bulge.Third,the evolution of the tectonic pattern had a significant impact on the sedimentary paleoenvironment.The O_(1)m_(1)overlaps westward,and saline lagoon is formed in eastern depression and influenced by the transgression.The transgression continued in O_(1)m_(2)and resulted in communication with the wide sea,and the large-scale grain shoal developed around eastern depression,and the late dry shrinkage formed a small scale evaporite lagoon in upper part.Under the influence of highland sealing in O_(1)m_(3),the water body gradually differentiated into dolomitic gypsum and saline lagoons to the east,and the grain shoal spread along the highs around sag.Fourth,the source rocks developed diachronously at the bottom of Majiagou Formation form a favorable source-reservoir assemblage with the shoal facies reservoir distributed around the slope of O_(1)m_(2)–O_(1)m_(3),and th

关 键 词：Ordos Basin ORDOVICIAN Majiagou Formation tectonic evolution tectonic pattern PALAEOGEOMORPHOLOGY tectono-sedimentary differentiation lithofacies paleogeography source-reservoir assemblage 

分 类 号：P618.13[天文地球—矿床学] TE14[天文地球—地质学]