南海北部琼东南盆地砂质天然气水合物储层沉积特征及成藏模式  

Sedimentary characteristics and accumulation model of sand-rich gas hydrate reservoir in the Qiongdongnan Basin,northern South China Sea

作　　者：任金锋[1] 陈雨核 徐梦婕 李廷微 王笑雪 赖洪飞 谢莹锋 匡增桂[1] REN Jinfeng;CHEN Yuhe;XU Mengjie;LI Tingwei;WANG Xiaoxue;LAI Hongfei;XIE Yingfeng;KUANG Zenggui(National Engineering Research Center of Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,Guangzhou 511458,China;College of Marine Science and Technology,China University of Geosciences(Wuhan),Wuhan 430074,China)

机构地区：[1]广州海洋地质调查局天然气水合物勘查开发国家工程研究中心,广东广州511458 [2]中国地质大学(武汉)海洋学院,湖北武汉430074

出　　处：《地学前缘》2025年第2期94-112,共19页Earth Science Frontiers

基　　金：国家重点研发计划项目(2024YFC2814701,2021YFC2800901);国家自然科学基金项目(42376221,42276083);广州海洋地质调查局局长科研基金项目(2023GMGSJZJJ00030);广州市科技计划项目(2023A04J0241);广东省基础与应用基础研究重大项目(2020B0301030003);中国地质调查局二级项目(DD20230064)。

摘　　要：砂质水合物储层是国际上水合物勘查试采的首选目标,我国在南海北部琼东南盆地钻探发现了高饱和度砂质水合物。通过三维地震、测井、岩心及测试分析资料,证实了规模化成藏的砂质水合物藏。砂质水合物储层表现为低自然伽马、低西格玛、高电阻率、高声波速度和T_(2)谱信号幅度急剧降低等测井响应特征,同时纵波及横波信号均明显衰减。砂层呈楔形近水平席状分布。岩性为粗粉砂细砂为主,属于深水浊积体系末端的朵体沉积。剖面上,水合物和游离气具有同层分布、横向过渡的特点。平面上,水合物藏呈现椭圆形分布,中部发育伴生游离气,外围发育水合物。与世界其他海域钻探发现的倾斜砂质水合物储层不同的是,该水合物藏是在稳定域底界附近的水平砂层,在下伏气烟囱背景下局部高热流驱动和上覆细粒沉积地层的封盖下,充足游离气由中部向外横向长运移而形成大面积高饱和度水合物。Sand-rich gas hydrate reservoirs are prime targets for hydrate exploration and test production worldwide.Concentrated hydrate in sand-rich reservoirs has been drilled in the Qiongdongnan Basin,northern South China Sea.Based on 3D seismic data,well logging,core samples,and test analysis,the large-scale accumulation of sand-rich gas hydrate has been confirmed.The sand-rich hydrate reservoir is characterized by low gamma ray,low sigma,high resistivity,increased P-wave and S-wave velocities,and a sharp reduction in T_(2) spectrum signal amplitude.Additionally,high attenuation of P-and S-waves is observed in hydrate-bearing zones.The sand layer is distributed in a wedge-shaped horizontal sheet.The lithology is mainly coarse silt to fine sand,developed in the terminal lobe of deep-water turbidite systems.In vertical sections,gas hydrate and free gas exhibit co-layered distribution and lateral transition characteristics.In map view,the gas hydrate reservoir shows an elliptical distribution,with free gas concentrated in the center and gas hydrate developed in the periphery.Unlike gas hydrate reservoirs in dipping sands of other regions worldwide,the gas hydrate reservoir in the Qiongdongnan Basin was formed in a horizontal sand layer near the base of the hydrate stability zone.The formation of highly saturated hydrate was driven by locally high heat flow at the top of the underlying gas chimney and capped by overlying fine-grained sediments.A large area of hydrate was formed through radially lateral,long-distance migration of sufficient free gas from the center to the periphery.

关 键 词：砂质水合物 气烟囱 深水朵体沉积 横向接触成藏 琼东南盆地 

分 类 号：P618.13[天文地球—矿床学]