四川盆地东南缘有机质演化异常与古地温场特征  

Evolution Anomaly of Organic Matter and Characteristics of Palaeogeothermal Field in the Southeast Edge of Sichuan Basin

作　　者：杨平 印峰[2] 余谦 汪正江 刘家洪 张娣 张道光[1,3] 

机构地区：[1]成都地质调查中心,四川成都610081 [2]中国石化勘探分公司,四川成都610041 [3]成都理工大学,四川成都610059

出　　处：《天然气地球科学》2015年第7期1299-1309,共11页Natural Gas Geoscience

基　　金：中国地质调查局项目(编号:12120114071401)资助

摘　　要：以四川盆地东南缘武隆地区为例，系统采集下古生界一中生界层系样品并进行镜质体反射率测试，在区域构造沉积演化史分析的基础上，对镜质体反射率异常带进行划分与成因分析，分别利用镜质体反射率梯度法及最大埋藏温度法恢复各层系地质历史过程中地温梯度及最大埋藏温度。四川盆地东南缘下古生界中生界存在4个镜质体反射率异常带，从上至下分别为上三叠统须家河组底部异常高值带、中二叠统栖霞组顶部一上二叠统龙潭组异常高值带、五峰组一龙马溪组底部页岩段异常高值带及其以下层系异常低值带，形成机制分别为油气运移带来的热流体活动、晚海西期峨眉玄武岩喷发、热液流体屏蔽层底部增温及地质流体高压封存箱。利用最大埋藏温度法恢复的古地温具有更高的可信度，恢复结果显示：受地质流体封存箱控制，下古生界地温梯度变化较大，寒武系地温梯度总体较低，志留系平均地温梯度可达41．47℃／km，上古生界一中生界古地温梯度为25．10～28．01℃／km，平均为26．18℃／km，大地热流背景值为66．78mW／m2。Taking Wulong region in the southeast edge of Sichuan Basin as an example,we have systemly collected Lower Paleozoic-Mesozoic samples and carried out measurement of vitrinite reflectance. Based on the analysis of deposition and evolution history of regional structure, research of division and origin of abnormal vitrinite reflec- tance zones has been carried out to reconstruct the geothermal gradient and maximum burial temperature of each stratum in the process of earth history by vitrinite reflectance gradient method and maximum burial temperature method. The four zones with abnormal vitrinite reflectance in Lower Paleozoic-Mesozoic in the southeast edge of Si- chuan Basin are high-value anomaly zone at the bottom of Upper Triassic Xujiahe Formation, high-value anomaly zone in Middle Permian Qixia Formation,Top-Upper Permian Longtan Formation,high-value anomaly zone in the shale section at the bottom of Wufeng Formation-Longmaxi Formation and low-value anomaly zone of other strata below respectively from top to bottom, which are respectively formed by the thermal fluid movement caused by oil- gas migration,the eruption of Emei basalt in Hercynian period,the increase of temperature at the bottom of shiel- ding layer of hydrothermal fluid and the high pressure compartment of geological fluid. The maximum burial tem- perature method is more reliable to reconstruct the paleogeotemperature. As shown by the reconstruction results, controlled by geological fluid compartment, the geothermal gradient at Lower Paleozoic is relatively large; the geothermal gradient in Cambrian is relatively low; the average geothermal gradient in Silurian can reach 41.47℃/km; the paleogeothermal gradient in Upper Paleozoic-Mesozoic is 25.10-28.01℃/km,with an av- erage value of 26.18℃/kin,and the background of terrestrial heat flow value is 66.78mW/m2.

关 键 词：四川盆地东南缘 镜质体反射率 最大埋藏温度 地温梯度 大地热流值 

分 类 号：TE122.1[石油与天然气工程—油气勘探]