银额盆地苏红图坳陷西部中生界烃源岩热演化史恢复  

Thermal History Reconstruction of Mesozoic Source Rocks in Western of Suhongtu Depression,Inner Mongolia,Northern China

作　　者：祁凯[1] 任战利[1,2] 崔军平[1,2] 陈志鹏 任文波[1] Qi Kai;Ren Zhanli;Cui Junping;Chen Zhipeng;Ren Wenbo(Department of Geology, Northwest University, Xi＇an 710069, China;State Key Laboratory of Continental Dynamics, Northwest University, Xi＇an 710069, China)

机构地区：[1]西北大学地质学系,陕西西安710069 [2]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《地球科学》2018年第6期1957-1971,共15页Earth Science

基　　金：国家自然科学基金重点项目(No.41630312);国家自然科学基金面上项目(No.41772121);国家科技重大专项(No.2017ZX05005002-008)

摘　　要：苏红图坳陷是位于银额盆地东北部的中生代断陷盆地,含油气资源勘探潜力较大.利用研究区7口井的75个镜质体反射率资料,分析了研究区中生界烃源岩热演化程度及分布特点,银根组烃源岩处于未成熟-低成熟阶段,苏红图组底部Ro分布在0.6%~1.2%,凹陷中心巴音戈壁组底部Ro普遍大于1.1%.苏红图坳陷西部中生代以来的热历史恢复表明,研究区现今地温梯度为34℃/km,晚白垩世地温梯度约为40.6~46.7℃/km,地温梯度从40~42℃/km(135~110 Ma)增加到46~50℃/km(110~103Ma),银根组沉积期(100~95Ma)地温梯度达到最大,为48~53℃/km;从乌兰苏海组沉积开始到现今,地温梯度先增大到40~46℃/km(92~80Ma),后逐渐降低为34℃/km(80~0Ma).研究区早白垩世以来较高的地温场对油气生成、成藏起着重要的控制作用,烃源岩均在乌兰苏海组沉积末期达到最大热演化阶段.Suhongtu depression,located in the northeastern of Yin＇e basin（Yingen-Ejinaqi basin）,is a Mesozoic faultingsubsiding basin with large oil and gas resources.75 vitrinite reflectance data from 7 wells in the study area are used to analyze the degree of thermal evolution of Mesozoic source rocks.The thermal evolution degree of source rocks in Yingen Formation is in immature to low mature stage.The vitrinite reflectance（Ro）data distribute in 0.6%-1.2%at the bottom of Suhongtu Formation,and they are generally greater than 1.1% at the bottom of Bayingebi Formation in the center of the sag.The results of Mesozoic and Cenozoic thermal history show that the present-day geothermal gradient is 34℃/km,and approximately 40.6-46.7℃/km in Late Cretaceous.The temperature gradient was 40-42℃/km（135-110 Ma）and increased to 46-50℃/km（110-103 Ma）.Especially,during the deposition period of Yingen Formation（100-95 Ma）,the geothermal gradient reached the maximum at about 48-53 ℃/km.From the beginning of Wulansuhai Formation,the geothermal gradient gradually increased to 40-46℃/km（92-80 Ma）and decreased to a present-day value of 34℃/km（80-0 Ma）ultimately.The higher geothermal field has played an important role in controlling oil and gas generation and accumulation since the Early Cretaceous,and the source rocks have reached the maximum thermal evolution stage at the end of the sedimentary period of the Wulansuhai Formation.

关 键 词：热史恢复 烃源岩热演化 镜质体反射率 中-新生代 银额盆地 石油地质 构造 

分 类 号：P624[天文地球—地质矿产勘探]