南海北部大陆架西段新生代热演化历史及其特点的分析

在新生代各个历史阶段,莺琼盆地、珠三盆地和北部湾盆地的古地温依序降低,并和今地温分布特点相似。新生代以来,三大盆地的地温也都有一个逐渐降低并在近期有所回升的趋势,珠三盆地相对变幅不大,莺琼盆地早第三纪的地温比现代更高,北部湾盆地晚第三纪相对低温的特点明显。这些区域地温的差异及其历史的变化,主要不是由于深部地热背景的不同或变化,而是因古地温研究区间沉积物热特性不同的结果。

ANALYSES ON CENOZOIC THERMAL HISTORY AND ITS FEATURES IN WEST SECTOR SHELF OF NORTHERN SOUTH CHINA SEA

Geothermal history is one of the important contens in hydrocarbon research. Onthe basis of over one thousand vitrinite reflectance data from more than 50 boreholes,this paper studied summarily the Cenozoic geothermal history and its features ofthe west sector shelf of the northern South China Sea.In each historical stage of Cenozoic, the geotemperature of Yingqiong Basin,Zhushan Basin and Beibuwan Basin declined successively. This geotemperature distribution tendency is similar to the present one. Since Cenozoic era, the geotemperatures of three major basins all tended to decline progressively in the past and riseagain at present. The geotemperature fluctuates within a narrow range in ZhushanBasin. In Yingqiong Basin, the geothemperature of Eogene was even higher than present. In Beibuwan Basin, the features of relatively low temperature in Neogene areobvious.This geotemperature descrepancy in different regions and the change with timeare not primarily due to the difference or variety in deep geothermal background,but are the result in diversified sediment's thermophysical properties in the regionsof palaeogeotemperature survey. Nevertheless, these disscrepancy and change in geotemperature are real as well, actually they are significant in illustrating the generation of hydrocarbons and their evolution.