加蓬海岸盆地海底麻坑的成因机制及对油气勘探的指示
EVOLUTION AND GENESIS OF SEABED POCKMARKS IN GABON COASTAL BASIN
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摘要: 海底麻坑是由于地下流体在高压下喷发而在海底形成的凹陷坑,可作为地下油气的直接指示。加蓬海岸盆地发现大量的海底麻坑,其地震反射同相轴表现为下拉特征,且地震反射振幅和相干属性均出现异常。该盆地海底麻坑的平面分布规律与下伏盐岩活动及盐岩展布有很大的相关性。通过对三维地震资料的解释,初步研究了加蓬海岸盆地海底麻坑的成因和形成模式。通过分析发现,该地区海底麻坑形成与下伏盐岩活动有关,盐底辟运动造成附近油气泄露产生相关气烟囱、亮点和海底麻坑等现象。海底麻坑可以成为下伏油气系统的直接指示,该地区的麻坑可以有效指示油气系统的展布范围和盐岩分布规律,预测断裂发育和有效圈闭带。对海底麻坑的深入研究有利于我们更好地优选勘探区带和区块,更好地了解研究区地下油气的分布规律。Abstract: Seabed pockmarks are the records of escaping gas or liquid through the sediment.They could be the direct indication of hydrocarbons.A lot of seabed pockmarks have been found in the Gabon Coastal Basin. The seabed pockmarks appear as pulling-down seismic reflection characters in seismic profiles with anomaly attributes.The distribution of seabed pockmarks in this area is closely related with the activity of salt.Fault and gas chimney can be the channel for gas escape.The evolution and genesis of seabed pockmarks in the basin are researched with 3Dseismics and it is proved that the information is useful for petroleum exploration in the basin.