南海北部大陆架边缘盆地CO_2成因和运聚规律的分析与预测

THE ANALYSIS AND DISCUSSION TO THE CHARACTERS ON GENERATIVE CAUSE, MIGRATION AND DISTRIBUTION OF CO_2 IN YING-QIONG BASINS IN THE NORTH OF THE SOUTH CHINA SEA

在近期所获大量新的地质地化资料基础上,重点对南海北部大陆架边缘盆地CO2成因及运聚成藏的主控因素进行了研究,并对可能的高CO2风险区进行了初步预测。认为:莺歌海盆地壳源型及壳幔混合型CO2的形成及富集成藏,主要受控于泥底辟热流体晚期分层、分块和多期的局部上侵活动,和巨厚的上新统—中新统海相含钙砂泥岩的物理化学综合作用,且CO2运聚分布规律亦具多期和分层、分区的特点;琼东南盆地东部及珠江口盆地火山幔源成因型CO2则主要受控于幔源型火山活动和沟通深部气源的基底深大断裂的导气配置作用,CO2运聚富集规律与幔源型火山活动及深大断裂的发育展布密切相关,CO2主要来自地壳深部幔源火山活动所伴生的大量CO2;因此,根据壳源岩石化学成因型CO2与火山幔源成因型CO2不同成因机理及成藏条件,可以追踪CO2气源,可分析和预测天然气尤其是CO2的运聚分布规律,可为天然气勘探部署及决策提供依据,可减少和降低勘探风险。另外还指出,油气藏中CO2的充注驱油特征可作为判识油气成藏动态过程的示踪标志,也可作为分析油气运聚、预测和追踪油气分布的良好指示。

Based on the geologic and geochemical data, this paper focused on the genesis of CO_(2) and the key control factors of its migration and accumulation. The research shows that in the Yinggehai basin, the formation of CO_(2) reservoir which is crust-sourced and crust-mental-mixed-sourced, mainly controlled by local action of hot fluid in the mud diapir area which is multi terms and multi zones and by physical-chemical mechanism of very thick marine calcareous sandstone and mudstone of Pliocene-Miocene. The volcano- and mantle-sourced CO_(2) in the Qiongdongnan basin and Pearl River Mouth basin is mainly controlled by volcano's activities and by the exist of large faults which reached to base to connect the gas from the mantle. According to different mechanism ang formation of reservoir os the the crustal rock-chemical genesis and volcano-and mantle-sourced CO_(2), we can follow the source of it, analysis and predict the migration and accumulation and distribution model of gas and espacially CO_(2), so as to help to make the plan of petroleum exploration and reduce the risk of exploration. In addition, the driving feature of oil by CO_(2) can be a mark to realize the process of the formation of oil and gas reservoir, and can be used to analyse the migration and accumulation and follow the distribution of oil and gas.