南海神狐海域天然气水合物饱和度的数值模拟分析  

Numerical modeling of gas hydrate saturation for the Shenhu area, South China Sea

作　　者：孙鲁一 张广旭[1] 王秀娟[1] 靳佳澎 何敏 朱振宇 SUN Luyi;ZHANG Guangxu;WANG Xiujuan;JIN Jiapeng;HE Min;ZHU Zhenyu(Key Laboratory of Marine and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049,China;CNOOC China Limited,Shenzhen Branch,Shenzhen 518054,China;Research Institute,CNOOC,Beijing 100027,China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,青岛266071 [2]中国科学院大学,北京100049 [3]中海石油(中国)有限公司深圳分公司,深圳518054 [4]中海油研究院,北京100027

出　　处：《海洋地质与第四纪地质》2021年第2期210-221,共12页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金“珠江口盆地高饱和度砂质天然气水合物储层的地震识别和钻前预测”(41676041);国家重点研发计划项目“南海多类型天然气水合物成藏地质过程与富集规律”(2017YFC0307301-1)。

摘　　要：珠江口盆地神狐海域是天然气水合物钻探和试验开采的重点区域,大量钻探取心、测井与地震等综合分析表明不同站位水合物的饱和度、厚度与气源条件存在差异。本文利用天然气水合物调查及深水油气勘探所采集的测井和地震资料建立地质模型,利用PetroMod软件模拟地层的温度场、有机质成熟度、烃源岩生烃量、流体运移路径以及不同烃源岩影响下的水合物饱和度,结果表明:生物成因气分布在海底以下1500 m范围内的有机质未成熟地层,而热成因气分布在深度超过2300 m的成熟、过成熟地层。水合物稳定带内生烃量难以形成水合物,形成水合物气源主要来自于稳定带下方向上运移的生物与热成因气。模拟结果与测井结果对比分析表明,稳定带下部生物成因气能形成的水合物饱和度约为10%,在峡谷脊部的局部区域饱和度较高;相对高饱和度(>40%)水合物形成与文昌组、恩平组的热成因气沿断裂、气烟囱等流体运移通道幕式释放密切相关,W19井形成较高饱和度水合物的甲烷气体中热成因气占比达80%,W17井热成因气占比为73%,而SH2井主要以生物成因为主,因此,不同站位甲烷气体来源占比不同。The Shenhu area is located in the Pearl River Mouth Basin.It is a critical testing area for gas hydrate drilling and pilot production.Comprehensive studies of core samples and logging and seismic data suggest that gas hydrate saturation,thickness of gas hydrate layer and gas source conditions are different from sites to sites.Based on the geological model established by integrating the well log and seismic data from both gas hydrate and deep-water oil and gas drilling sites,we simulated the temperature field,organic matter maturity,hydrocarbon generation of source rocks,fluid migration pathways and gas hydrate saturation related to different source rocks with the PetroMod software.The results suggest that biogenic gas is mainly distributed in the immature organic strata 1500 m below the seafloor,while thermogenic gas is distributed in the matured and over matured deposits over a depth of 2300 m.Gas hydrate cannot be formed by in-situ biogenic gas within the gas hydrate stability zone.Therefore,the gases,which may form gas hydrate are mainly the biogenic and thermogenic gases moving up from the deep strata.The comparison between the modeling results and the log-derived saturation data suggest that the simulated saturation is around 10%for biogenic gas to become gas hydrate in the lower part of stability zone,while the value is higher at some areas such as canyon ridges.Higher saturation(>40%)for hydrate formation is closely related to deep source thermogenic gas from the Wenchang and Enping Formations released in an episodic manner along the fluid migration channels such as sand layers,faults and gas chimneys.In addition,the methane contents from biogenic and thermogenic gases are calculated based on the modeling gas hydrate saturation.It shows that the thermogenic gas content is about 80%at Site W19 and 73%at Site W17,and nearly no thermogenic gas is found at Site SH2.

关 键 词：数值模拟 热成因气 流体运移 水合物饱和度 神狐海域 

分 类 号：P738[天文地球—海洋地质]