鄂尔多斯盆地东部奥陶系马家沟组四段神木-志丹低古隆起的发现及油气勘探意义  

Discovery and implications for hydrocarbon exploration of the Shenmu-Zhidan low paleo-uplift in the 4th member of the Ordovician Majiagou Formation,eastern Ordos Basin

作　　者：于洲 周进高 罗晓容 李永洲[4] 于小伟 谭秀成 吴东旭[3] YU Zhou;ZHOU Jingao;LUO Xiaorong;LI Yongzhou;YU Xiaowei;TAN Xiucheng;WU Dongxu(State Key Laboratory of Continental Dynamics,Northwest University,Xi’an,Shaanxi 710069,China;Department of Geology,Northwest University,Xi’an,Shaanxi 710069,China;Hangzhou Research Institute of Geology,PetroChina,Hangzhou,Zhejiang 310023,China;Coalbed Methane Company Limited,PetroChina,Beijing 100028,China;Changqing Branch of Geophysical Research Institute,BGP Inc.,CNPC,Xi’an,Shaanxi 710021,China;School of Geoscience and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China)

机构地区：[1]大陆动力学国家重点实验室西北大学,陕西西安710069 [2]西北大学地质学系,陕西西安710069 [3]中国石油杭州地质研究院,浙江杭州310023 [4]中国石油煤层气有限责任公司,北京100028 [5]中国石油东方地球物理公司研究院长庆分院,陕西西安710021 [6]西南石油大学地球科学与技术学院,四川成都610500

出　　处：《石油与天然气地质》2024年第5期1383-1399,共17页Oil & Gas Geology

基　　金：中国石油集团公司攻关性应用性科技专项(2023ZZ16YJ01);长庆油田公司重大科技专项(ZDZX2021)。

摘　　要：米探1井油气勘探突破展示出盆地东部奥陶系马四段具有良好的勘探前景,由于盆地东部奥陶系马四段时期古构造格局认识不清,制约了该层系的天然气勘探。根据磁力资料、地震剖面、钻井资料、野外露头和地球化学特征分析等资料,发现了鄂尔多斯盆地东部奥陶系马四段神木-志丹低古隆起,研究了古隆起形成机制及对马四段沉积和储层的控制作用。研究结果表明:①神木-志丹低古隆起呈北东向展布,宽约140 km,长约250 km,面积为3.8×10^(4)km^(2)。②神木-志丹低古隆起发育于奥陶系马四段沉积。古隆起的形成受古基底组成差异和同沉积正断层共同控制。同沉积正断层下盘的古基底在正断层作用下演变为地势相对较高的低古隆起,同沉积正断层上盘的古基底在同沉积正断层作用下向下沉降并转变为地势相对较低的坳陷或凹陷。③神木-志丹低古隆起地势相对较高,发育微生物丘、灰泥丘和砂屑滩,经准同生白云化作用后可形成优质白云岩储层。④神木-志丹低古隆起广泛沉积了一套厚度为1~12 m的硬石膏岩层,低古隆起带上的马四段白云岩储层在侧向致密灰岩和纵向硬石膏岩的封堵作用下,可形成封闭性能较好的岩性圈闭。⑤神木-志丹低古隆起马四段白云岩岩性圈闭位于现今构造高部位,断层发育,遮挡条件好,有利于天然气运移和富集。Breakthroughs in hydrocarbon exploration in well Mitan 1 demonstrate that the 4th member of the Ordovician Majiagou Formation(also referred to as the Ma 4 Member)in the eastern Ordos Basin has great potential for hydrocarbon exploration.However,the limited understanding of the paleotectonic framework of the Ma 4 Member in this region has restricted natural gas exploration in this member.Using aeromagnetic data,seismic sections,and drilling data,outcrop observation,and geochemical analysis,we identify the Shenmu-Zhidan low paleo-uplift within the Ma 4 Member in the eastern Ordos Basin,as well as the formation mechanisms of the paleo-uplift.The controlling effects of the paleo-uplift on the sedimentary reservoirs of the Ma 4 Member are thereby discussed.The results indicate that the Shenmu-Zhidan low paleo-uplift extends in the NE direction,with a width of approximately 140 km,a length of around 250 km,and an area of 3.8×10^(4)km^(2).This low paleo-uplift was formed during the deposition of the Ma 4 Member under the combined influence of the compositional differences of the paleobasement and syndepositional normal faults.Specifically,under the effects of syndepositional normal faulting,the paleobasement in the footwall of the normal faults evolves into relatively high-lying low paleo-uplifts,while that in their hanging wall underwent subsidence and evolves into relatively low-lying depressions or sags.The Shenmu-Zhidan low paleo-uplift is relatively high-lying,containing microbial mounds,mud mounds,and psammitic shoals,which can develop into high-quality dolomite reservoirs in the presence of penecontemporaneous dolomitization.Additionally,this paleo-uplift exhibits a sequence of widely developed anhydrite layers with thicknesses varying from 1 to 12 m.The dolomite reservoirs in the Ma 4 Member within the low paleo-uplift zone are sealed by tight limestones laterally and anhydrite layers vertically,allowing them to form lithologic traps with excellent sealing performance.The lithologic traps of dolomites in the Ma

关 键 词：沉积储层 断层 古基底 神木-志丹低古隆起 马四段 奥陶系 鄂尔多斯盆地 

分 类 号：TE121.2[石油与天然气工程—油气勘探]