摘要：
The Indo-Burmese Wedge is located in the subducting plate front between the Indian Plate and the Eurasian Plate.Reviewing the deep water petroleum exploration potential and understanding the hydrocarbon accumulation patterns and mechanism in the accretionary wedge area are the hot spots of current international petroleum expIoration,and the Indo Burmese Wedge provides a good example and opportunity.It is not only an oblique subduction accretionary wedge but also a gas chimney-enriched accretionary wedge.The target of this paper is to provide an analysis of gas chimney characteristics,distribution and relationship with hydrocarbon accumulation in the Indo Burmese Wedge by the technologies of seismic spectrum scanning,seismic attribute analysis and nonlinear neural network based on high-resolution seismic data.The results reveal that the distribution of gas chimneys varies in different structural units,and the development phases of gas chimneys reduced progressively,and the strata of gas chimneys become gradually younger seaward.In the accretionary wedge slope,the fault-type of gas chimneys developed during the Holocene and the Miocene,vertically across the Oligocene to Pleistocene strata;in the trench basin,the anticline-type of gas chimneys developed during the Holocene,vertically across the Miocene to Holocene strata.The formation conditions of gas chimney were analyzed in detail,including the power source of gas chimney coming from the overpressure formed by Oligocene and Miocene source rocks,gas source pathways formed by episodic tectonic activities and seal conditions formed by the mud and shale in Paleogene and Neogene strata.In addition,our results show that gas chimney has a close relationship with hydrocarbon accumulation in the Indo Burmese Wedge.The associated structures of gas chimney with the seismic reflection characterized by amplitude increasing,frequency decreasing and phase transforming accompanied by flat and bright spot are the favorable targets for hydrocarbon accumulation.Additionally,three models of gas chimney hydrocarbon accumulation,including mixed-source fault type,biogenic gas source faulted anticline type and biogenic gas source anticline type,are proposed based on the gas source characteristics of gas chimneys.The seismic anomaly bodies in or around gas chimneys have great shallow gas exploration potential,and the exploration for structures or lithlogic traps in source rocks is another favorable oil and gas field in the trench basin of the Indo-Burmese Wedge.%印缅俯冲增生楔位于印度板块与欧亚板块俯冲前缘,是深水油气勘探的重要地带.重新审视深水油气勘探潜力、认识增生楔地区油气成藏模式和机理是当前研究热点.印缅俯冲带增生楔提供了一个良好实例和研究契机,它不仅是一个斜向俯冲增生楔,而且是一个气烟囱发育的增生楔.本文基于高精度地震资料,应用地震波组和频谱扫描、地震属性检测以及基于多层感知器的非线性神经网络技术,识别出该区气烟囱具有分带性,且在增生楔斜坡和海沟盆地气烟囱发育.气烟囱总体表现出向海渐新、期次递减的特征,即增生楔斜坡以全新世和中新世两期发育的断层型气烟囱为主,纵向上横跨渐新统至更新统;海沟盆地以全新世发育的背斜型气烟囱为主,纵向上横跨中新统至全新统.气烟囱发育的动力来源为渐新统和中新统烃源岩持续生烃形成的超压,幕式构造活动产生气源通道,古近系和新近系中的泥页岩等提供封盖条件.气烟囱与油气成藏关系密切,具有振幅、频率、相位等地震异常并伴有亮点、平点等地震反射的相关伴生构造是油气运聚的有利目标.结合气烟囱的气源特征,本文提出混源断层型、生物气源断层-背斜型、生物气源背斜型等三种气烟囱成藏模式,指出海沟盆地气烟囱地震异常体具有较好的浅层天然气勘探前景,下覆烃源岩内幕构造、岩性圈闭是另一个有利的油气勘探领域.
