主动大陆边缘典型地区流体运移体系对天然气水合物成藏的影响研究

Study on the effect of fluid migration system on natural gas hydrate accumulation in typical areas along active continental margin

天然气水合物在主动大陆边缘普遍发育,其形成分布与流体运移体系密切相关,对深水油气勘探、海底灾害和全球气候变化研究等具有重要意义.本文选取主动大陆边缘典型地区(马克兰增生楔、郁陵盆地和卡斯卡迪亚增生楔),系统总结各地区流体运移体系特点,旨在探讨流体运移体系对天然气水合物成藏的影响.研究结果表明,同为主动大陆边缘,受制于局部构造环境和沉积条件的影响,不同地区流体运移体系发育模式、水合物成藏类型具有较大差异.马克兰增生楔流体运移体系以泥底辟、断层为主导,形成了“泥底辟型”、“阶梯式增生楔型”水合物藏;郁陵盆地流体运移体系以气烟囱为主导,形成了“扩散型”水合物藏;卡斯卡迪亚增生楔流体运移体系以泥底辟、气烟囱及断裂组合为主导,形成了“渗漏型”水合物藏.尽管前人对主动大陆边缘典型海域的天然气水合物进行了大量的地球物理调查,归纳了多种水合物成藏类型,但由于技术手段限制,缺乏不同运移体系下对流体通量的定量研究及不同运移体系的时空演化过程分析,因此建议将地球物理、地质和地球化学等多学科的研究方法和技术相结合,进行多尺度、多参数的综合研究.

The natural gas hydrates widely distribute alongthe active continental margin.The formation anddistribution of gas hydrates are intimately connected tofluid migration systems,holding significant implications fordeepwater oil and gas exploration,researches on submarinedisasters,and global climate change.This study focuseson selected active continental margin regions,namely theMakran accretion wedge,Ulleung Basin,and Cascadiaaccretion wedge,to provide a systematic summary of thedistinct characteristics exhibited by fluid migration systemson wedge,Ulleung Basin,and Cascadia accretion wedge,to provide a systematic summary of the distinctcharacteristics exhibited by fluid migration systems in eachregion,aiming to investigate the influence of fluidmigration systems on gas hydrate accumulation.Findingsreveal that variations in local tectonic environments andsedimentary conditions give rise to diverse developmentmodels for fluid migration systems and hydrateaccumulation types across different regions.The fluidmigration system within the Makran accretion wedge ispredominantly governed by mud diapirs and faults,resulting in the formation of “ mud diapir” and “ multi-stepped accretionary wedge” type hydrate reservoir.In theUlleung Basin,the fluid migration system is dominated bygas chimneys,leading to the formation of a diffusedhydrate reservoir.In the Cascadia accretion wedge,thefluid migration system is characterized by a combination ofmud diapirs,gas chimneys,and fractures,giving rise to a leaky hydrate reservoir.While extensive geophysicalsurveys have been conducted on gas hydrates in typical seaareas of active continental margins,and various hydrateaccumulation types have been identified,there remains adearth of quantitative studies on fluid flux under differentmigration systems and analyses of spatio-temporal evolutionprocesses associated with different migration systems.Therefore,it is recommended to integrate researchmethodologies and techniques from disciplines such asgeophysics,geology,and geochemistry to undertake acomprehensive,multi-scale,and multi-parameter study.