台湾海峡盆地九龙江凹陷火成岩发育特征及其油气地质意义

IGNEOUS ROCKS IN JIULONGJIANG SAG OF TAIWAN STRAIT BASIN AND IMPLICATIONS FOR PETROLEUM GEOLOGY

基于二维地震剖面的精细地质解释,并结合磁力和钻井资料分析,开展了九龙江凹陷火成岩发育特征、岩浆活动和区域构造与盆地演化关系及其油气地质意义的研究。分析认为,九龙江凹陷经历了始新世中晚期、中新世中晚期二期火山活动,火成岩在地震剖面上主要表现为板状、锥状及块状三种地震相类型,钻井主要揭示了喷发、侵入及火山碎屑三大类型火成岩,它们的发育与分布是区域性构造事件和盆地演化相作用的结果。始新世中晚期火山活动产生的高温有利于烃源岩在短期内经历高温的催化改造而生成油气,形成的火成岩体岩墙面可以增加和改善凹陷中央区油气向西部斜坡的运移,该火成岩附近区的一些圈闭在成岩期受热液蚀变的影响,储层孔、渗性得到改善的同时也会致使储层发生不同程度的变质,在今后的勘探开发中是一个值得关注的问题。

Based on the 2Dseismic,magnetic and well data,we studied in this paper the characteristics of the igneous rock in the Jiulongjiang Sag of the Taiwan Strait Basin,the relationships of the magmatic activity with the regional tectonics and the sag evolution,and their petroleum significance.The JiuLongJiang Sag has suffered from two times of volcanic activities.Three types of seismic facies of igneous rocks,the tabular,conical and massive igneous rocks,are recognized in seismic profiles.The well data reveals that there are three types of igneous rocks i.e.extrusive rock,intrusive rock and volcanoclastic rock.The development and the distribution of the igneous rocks are related to the regional tectonics and basin evolution.The magmatic activity in Late Eocene is supposed favorable for a large quantity of hydrocarbon to generate from source rocks,as the high thermal fluid brought by magmatism could increase ancient geothermal gradient and accelerate the evolution of source rocks towards maturity.The igneous rock walls could result in the formation of more conduits for oil and gas migration and accumulation.The porosity and permeability of reservoir could be improved and the metamorphism of the reservoirs maybe helpful to the improvement of reservoir properties.It is a matter of concern in the future oil exploration and development.