北黄海东部次盆地构造热机制与成烃效应  

Tectono-thermal mechanism and hydrocarbon generation action in the North Yellow Sea Eastern Sub-basin

作　　者：刘金萍 王改云[1,2] 简晓玲 朱传庆[3] 胡小强 袁晓蔷[1,2] 王超[1,2] LIU Jinping;WANG Gaiyun;JIAN Xiaoling;ZHU Chuanqing;HU Xiaoqiang;YUAN Xiaoqiang;WANG Chao(Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou 511458,China;Guangzhou Marine Geological Survey,Guangzhou 511458,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]自然资源部海底矿产资源重点实验室,广东广州511458 [2]广州海洋地质调查局,广东广州511458 [3]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249

出　　处：《地学前缘》2024年第4期206-218,共13页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(DD20211362,DD20221708,DD20242406)。

摘　　要：北黄海东部次盆地属于中新生代小型叠合断陷盆地,是我国海域勘探程度较低的一个盆地,对其经历的复杂构造-热演化史尚未有相关研究。本文利用镜质体反射率(R_o)和磷灰石裂变径迹(AFT)两种古温标进行多方法的热史模拟,获得了盆地中新生界的热流史及地温梯度的变化,并恢复了盆地的剥蚀量及抬升剥蚀过程,在此基础上研究了盆地内烃源岩的热演化历史。结果表明,东部次盆地从中侏罗世至今,经历了古热流由高(75~90 mW/m^(2),120~100 Ma)到低(60 mW/m^(2),40 Ma),然后再升高至现今(70 mW/m^(2))的过程,且早期(100~70 Ma)降温缓慢,后期(70~40 Ma)降温快速。古地温梯度相应地呈现由高(34~36℃/km)到低(23℃/km),再升高(28℃/km)的变化趋势。东部次盆地晚白垩世之前的古地温梯度和古热流高于现今的地温梯度和热流,这与盆地由断陷阶段-坳陷阶段的演化过程一致。东部次盆地晚白垩世—始新世经历了较强的抬升剥蚀,地层的剥蚀厚度为1.0~1.5 km,在100~90 Ma地层沉积开始缓慢或停止,明显的剥蚀过程发生在85~40 Ma,其中70~40 Ma为快速剥蚀阶段。东部次盆地的构造热演化史影响了盆地内烃源岩的生烃过程。中上侏罗统两套烃源岩都存在早期(晚侏罗世—早白垩世)生烃过程,在中部坳陷内的主体生烃坳陷,晚白垩世—始新世地层剥蚀厚度较小,且渐新世之后地层沉积厚度较大,现今能够达到的地温也越高,有利于烃源岩晚期生烃,证实了该盆地具有一定的勘探潜力,应围绕主体生烃坳陷寻找有利成藏区。The North Yellow Sea Eastern Sub-basin is a typical Meso-Cenozoic small superimposed faulted basin,currently in its early exploration phase.Comprehensive studies on the complex tectonic-thermal evolution in this region are lacking.By integrating vitrinite reflectance(Ro)and apatite fission track(AFT)analysis,the thermal history and geothermal gradient of the Meso-Cenozoic era have been reconstructed in this basin,alongside assessments of erosion thickness and processes.These investigations have enabled an analysis of the thermal evolution history of Middle-Upper Jurassic source rocks.Results indicate that paleoheat flow peaked at 7590mW/m^(2)during 120100 Ma,decreased to 60 mW/m^(2)at 40 Ma,and then rose to 70 mW/m^(2)at present.Correspondingly,temperatures declined gradually from 10070 Ma but rapidly dropped during 7040 Ma,with the geothermal gradient shifting from 3436℃/km to 23℃/km before rising to 28℃/km.Overall,paleo-geothermal gradient and heat flow were higher before the Late Cretaceous,aligning with the transition from a faulted basin to a depression basin.Intense uplift and erosion occurred during the Late Cretaceous-Eocene,resulting in an erosion thickness of approximately 1.01.5 km.Deposition slowed or ceased during 10090 Ma,with significant uplift occurring during 8540 Ma,especially rapid during 7040 Ma.The tectonic-thermal history has influenced hydrocarbon generation,with both Middle and Upper Jurassic source rocks experiencing early hydrocarbon generation during the Late Jurassic-Early Cretaceous.In the central depression,erosion thickness was thinner in the Lower Cretaceous-Eocene,while deposition thickness was thicker in the Oligocene-Quaternary,leading to higher present-day strata temperatures and favoring late hydrocarbon generation.Exploration efforts for potential accumulation should focus on areas surrounding hydrocarbon generation depressions.

关 键 词：东部次盆地 磷灰石裂变径迹 镜质体反射率 构造热演化史 成烃效应 

分 类 号：P544.4[天文地球—构造地质学] P618.130.2[天文地球—地质学]