神狐海域高饱和度天然气水合物储层特征及其分布  

Characteristics and distribution of gas hydrate bearing sediments with high saturation in the Shenhu area,South China Sea

作　　者：梁劲 沙志彬[1,2] 孟苗苗 王笑雪 徐梦婕 方允鑫 LIANG Jin;SHA Zhibin;MENG Miaomiao;WANG Xiaoxue;XU Mengjie;FANG Yunxin(Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou,Guangdong 511458,China;National Engineering Research Center for Gas Hydrate Exploration and Developrment,Guangzhou,Guangdong 511458,China)

机构地区：[1]自然资源部海底矿产资源重点实验室,中国地质调查局广州海洋地质调查局,广东广州511458 [2]天然气水合物勘查开发国家工程研究中心,广东广州511458

出　　处：《地质学报》2024年第9期2641-2653,共13页Acta Geologica Sinica

基　　金：广东省基础与应用基础研究重大专项(编号2020b0301030003);中国地质调查项目(编号DD20230064);广东省海洋经济发展专项(编号GDNRC[2023]40)联合资助的成果。

摘　　要：2017年,中国地质调查局在南海北部神狐海域进行了水合物试验开采,累计产气30.9×10^(4)m^(3),平均日产超5000 m^(3),甲烷含量最高达99.5%,实现了水合物勘察领域的历史性跨越。在水合物试验开采前,精细剖析研究区的测井数据和地震资料,并通过对研究区的区域地质背景和钻井岩芯样品的分析研究,含水合物地层的沉积、断裂、气体成分、碳同位素等特征以及水合物饱和度数据分析,总结研究区高饱和度水合物的储层特征及分布规律。结果表明:①研究区中—高饱和度水合物主要分布在迁移峡谷群的峡谷脊部,而低饱和度水合物站位则主要分布在峡谷群的谷底位置;②海底峡谷水道是陆源物质向深海运移的重要通道,研究区浊积水道和天然堤发育,与水合物富集成藏密切相关;③研究区高饱和度水合物层对应的电阻率和声波速度值显著升高,而中子孔隙度、密度和自然伽马值则有所降低;④高饱和度水合物在地震反射剖面上具有似海底反射(BSR)、穹状反射和模糊杂乱反射特征,BSR之下气烟囱和断裂通道发育,碳氢气体容易运移到温度和压力稳定区域形成高饱和度水合物储集层;⑤研究区水合物聚集和赋存的地层沉积骨架主要为细粒沉积,水合物以均匀颗粒和扩散的形式分布于沉积物中;⑥研究区水合物气源主要为混合成因气,热成因气通过断裂、裂隙、气烟囱构造向浅层运移,降解并与原位生物气混合为水合物形成共同提供气源。In 2017,the China Geological Survey conducted a gas hydrate exploration test in the Shenhu area of the northern South China Sea.The test achieved a cumulative gas production of 30.9×10^(4)m^(3),with an average daily output exceeding 5000 m^(3)and a methane content of up to 99.5%.This successful test marked a historic breakthrough in the field of gas hydrate exploration.Prior to the gas hydrate exploitation test,detailed analyses were carried out on well logging data,seismic data,and drilling core samples from the study area.This analysis focused on characterizing the depositional environment,faults,gas composition,carbon isotopes,and gas hydrate saturation within the formation.The result revealed the following:①Middle-high saturation gas hydrate is mainly concentrated along the ridges of the migrating canyon groups,while low saturation gas hydrate is mainly found in the valley bottoms.②Submarine canyons serve as crucial pathways for transporting terrigenous materials to the deep sea.The development of turbidity channels and natural levees within these canyons is closely related to gas hydrate accumulation.③The resistivity and acoustic velocity of highly saturated gas hydrate layers increase significantly,whereas neutron porosity,density,and natural gamma values decrease.④Highly saturated gas hydrate displays characteristics of seismic reflections,including bottom simulating reflections(BSR),dome-like reflections,and chaotic reflections.Gas chimneys and fault pathways are often observed beneath the BSR,indicating the upward migration of hydrocarbon gas to shallower,stable temperature and pressure conditions favorable for formation.⑤Gas hydrate is mainly uniformly diffused in fine-grained sediments.⑥The gas source for hydrate formation is mainly a mixture of thermogenic and biogenic gas.Thermogenic gas migrates from deeper layers through fractures,fissures,and gas chimneys,where it degrades and mixes with in-situ biogas,which together provide a gas source for gas hydrate formation.

关 键 词：神狐海域 高饱和度 天然气水合物 浊积水道 天然堤 细粒沉积 

分 类 号：P618.13[天文地球—矿床学]