塔北地区鹰山组下段—蓬莱坝组白云岩成因及控储意义  

Genesis of Dolomite and Its Controls on Reservoir Spaces in Lower Yingshan Formation-Penglaiba Formation,Northern Tarim Basin

作　　者：田家奇 李国蓉[1] 刘永立[2] 李肖肖 何钊 何赛[1,4] TIAN Jiaqi;LI Guorong;LIU Yongli;LI Xiaoxiao;HE Zhao;HE Sai(School of Energy,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Northwest Oilfield Company,Sinopec,Urumqi,Xinjiang 830011,China;No.2 Gas Production Plant,Southwest Oil&Gas Company,Sinopec,Langzhong,Sichuan 637400,China;Geophysical Exploration Institute Co.,Ltd.,Sichuan Resources Group,Chengdu,Sichuan 610072,China)

机构地区：[1]成都理工大学能源学院,成都610059 [2]中国石化西北油田分公司,乌鲁木齐830011 [3]中国石化西南油气分公司采气二厂,四川阆中637400 [4]四川省自然资源投资集团物探勘查院有限公司,成都610072

出　　处：《新疆石油地质》2024年第3期306-316,共11页Xinjiang Petroleum Geology

基　　金：中国石化科技部项目(P21048-3)。

摘　　要：为确定塔北地区中—下奥陶统鹰山组下段—蓬莱坝组白云岩成因,通过岩心及岩石薄片观察,利用阴极发光、X射线衍射有序度、碳氧稳定同位素、锶同位素和稀土元素组成及配分模式分析,并将岩石学与地球化学特征结合,开展了塔北地区鹰山组下段—蓬莱坝组白云石化作用研究。粉—微晶白云石和粉—细晶他形脏白云石由同生期高盐度海水白云石化作用形成,流体主要源自地表低温蒸发条件下的高盐度海水;粉—细晶自形白云石由早成岩期浅埋藏白云石化作用形成,流体主要源自奥陶纪海水,流体温度因埋藏加深而升高;鞍形白云石由早成岩期热液白云石化作用形成,流体主要源自奥陶纪海水,且有后期深部岩浆热液加入。同生期高盐度海水白云石化作用不产生储集空间,但由于区域局限,蒸发强烈,可伴随石膏沉淀,石膏溶蚀后形成储集空间;早成岩期浅埋藏白云石化作用可形成自形白云石,促进晶间孔的发育,成岩后期溶蚀流体易进入,溶蚀形成晶间溶孔和溶蚀孔隙;早成岩期热液白云石化作用不利于储集空间的形成。To determine the genesis of dolomite in the lower Yingshan formation-Penglaiba formation of the Middle-Lower Ordovician in northern Tarim basin,this paper investigates the dolomitization in the target interval through the observations of core samples and thin sec⁃tions and the analysis of cathodoluminescence,X⁃ray diffraction order degree,stable carbon and oxygen isotopes,strontium isotopes,and rare earth element compositions and partition patterns,and by combining petrological characteristics with geochemical characteristics.The results show that silty to microcrystalline dolomites and silty to fine⁃grained anhedral dolomites were formed from syndepositional dolomiti⁃zation in high⁃salinity seawater which was primarily originated from the seawater under low⁃temperature surface evaporation;silty to fine⁃grained euhedral dolomites were formed from shallow⁃burial dolomitization in early diagenetic period,with fluids sourced from Ordovician seawater and an increasing temperature with the increase of burial depth;and saddle⁃like dolomites were formed from hydrothermal dolomi⁃tization in early diagenetic period,with fluids sourced from Ordovician seawater as well as later deep⁃seated magmatic hydrothermal fluid.Reservoir spaces can’t generate from syndepositional high⁃salinity seawater dolomitization,but may be formed after the dissolution of the precipitated gypsum due to regional constraints and intense evaporation.Eeuhedral dolomite can form under early diagenetic shallow⁃burial dolomitization,which promotes the development of intercrystalline pores where dissolution fluid may easily enter in late diagenetic stage,forming intercrystalline dissolution pores and dissolved pores.Early diagenetic hydrothermal dolomitization is unfavorable for the formation of reservoir spaces.

关 键 词：塔里木盆地 塔北地区 奥陶系 鹰山组 蓬莱坝组 白云岩 白云石化作用 储集空间 

分 类 号：TE112.221[石油与天然气工程—油气勘探]