利用岩石圈瞬态热流模型重建渤海湾盆地新生代热历史

Reconstruction of Cenozoic thermal history of Bohai Bay Basin with a transient heat flow model

以孔隙度、热导率、地层温度及镜质体反射率数据作为校准，利用BasinMod软件建立了一维岩石圈瞬态热流模型，挑选渤海湾盆地内资料相对齐全且靠近沉积一沉降中心的9口深钻孔，对新生界地层热历史进行了重建。模型中考虑了沉积压实、非均一热导率结构、沉积层和地壳的放射性生热以及沉积充填和剥蚀作用的热效应。作为检验和对比，模拟了双层伸展裂谷模型热流和不变的现今热流两种情形，结果表明：除了东营末期剥蚀地层厚度较大的局部地区以外，渤海湾盆地大部分地区新生界沉积层的现今地层温度皆因深埋作用而处于其所经历的最高温度，但现今热流却不是其经历的最大热流；最大热流出现在东营组地层遭受剥蚀的末期，距今约16-20Ma，最高地表热流值高于现今9％～23％。简单裂谷热流模型不能反映由古温标和井底温度所记录的热流史，而瞬态模型包含了更多的地质信息，考虑了更多的影响因素，由此所预测的热历史可能与渤海湾盆地岩石圈和沉积层在新生代期间所经历的实际热演化史更加吻合。

A model of one-dimensional transient heat flow was established by using the BasinMod software. Calibrated by the porosity, thermal conductivity, temperature of borehole and vitrinite reflectance, the thermal history of the Cenozoic sediments of nine deep wells in Bohai Bay Basin was reconstructed with the transient heat flow model, which considered the compaction of sediments, heterogeneous conductivity structure, radioactive heat production in the upper crust and sediments, and thermal effects of sedimentary fillings and erosion. The simulation results of the heat flow history predicted by two-layer rift model and the constant current heat flow indicate that the present subsurface temperature of the Cenozoic sediments is the highest temperature attributed to deep burial, except local areas where the eroded thickness of Dongying Formation is large. However, the present heat flow value is not the highest ever experienced. The highest heat flow is 9%-23% higher than the current value and occurred at the end of erosion of Dongying Formation before present 16-20 Ma. The radioactive heat generation is neglected in the rift heat flow model, which cannot refleet the thermal history by recorded temperature at the paleothermometry and present bottom hole. The transient heat flow model contains more geological information and influential factors than the rift heat flow model. The thermal history predicted by the transient heat flow model is likely the actual thermal evolution process experienced by the lithosphere and sediments in Bohai Bay Basin during the Cenozoic period.