塔里木盆地北部的地温特征

GEOTHERMAL CHARACTERISTICS IN NORTHERN TARIM BASIN,NORTHWESTERN CHINA

在收集、分析了大量的现场测温、镜质体反射率和包体测温等资料的基础上,主要探讨了3个问题:(1)今地温梯度在平面上和纵向(层位)上的分布规律以及形成这种分布的原因;(2)用地壳厚度法估算主力生油岩系的几个主要地史时期的古地温梯度;(3)中生界镜质体反射率与对应最大地温的特殊关系和解释。

Based on a large amount of collected data,such as geotemperature ,vitrinite reflectance and fluid inclusion,this study is focused on geothermal characteristics in Northern Tarim Basin. (l)The present thermal gradients are very different in various tectonic units. Generally, depressions are lower gradient, while uplifts and huge gas fields accumulating on Cenozoic are higher. High gradient anomalies on the gas fields may be generated by an upward migration and accumulation of the heat flow from the deep. The results demonstrate that the present gradient in northern Tarim Basin is low ,and increases obviously from the lower to the upper levels in the vertical section,due to different thermal conductivities of the rocks and depositional rates of the sediments. (2)Estimates are made for the palaeo-geothermal gradient of the major source rocks in several significant periods by using the crust thickness method. (3)The specific relationship between the Mesozoic low vitrinite reflectance and high geotemperature is attributed to the very fast deposition of the overlying Cenozoic, which causes the great burial depth and shortens effective heating time of the Mesozoic.