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南海北部神狐峡谷区沉积相特征及BSR地质灾害指示

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神狐海底峡谷群是我国南海北部天然气水合物勘探的主要目标区,本文根据多道地震资料结合勘查试采成果,精细刻画了神狐峡谷区沉积相特征,并将海底峡谷沉积体系分为峡谷充填和峡谷边缘两个亚相,前者包括浊积水道、滞留沉积、侧向倾斜沉积和块体流沉积4个微相,后者含天然堤、浊积扇和块体流沉积3个微相.通过对神狐峡谷群的沉积单元和BSR整体分布特征的系统分析,明确提出了上新世以来的峡谷沉积体系中,天然堤沉积微相和块体流沉积微相是水合物富集的有利沉积相带.同时,根据沉积相带中BSR发育位置及特征差异,将该区BSR划分为3种类型:A型为脊部穹隆型、B型为脊部边缘平直型、C型为峡谷边缘坡变型.在此基础上,结合天然气水合物分解可能引起海底滑塌的致灾机理,强调指出C型BSR具有视倾角变大、上覆地层薄的特点,是水合物极易分解而发生滑塌的高风险区.本研究成果可为神狐峡谷海域新一轮天然气水合物试采,尤其是环境稳定性评价预测等提供重要依据和技术支撑.
Sedimentary facies characteristics and indication of geological hazard of BSR in Shenhu canyon area of northern South China Sea
The Shenhu submarine canyon group is the main target area for gas hydrate exploration in the northern South China Sea.This paper utilizes multi-channel seismic data from the region,along with results from gas hydrate exploration and trial production,to detail the sedimentary facies characteristics of the Shenhu canyon area.The submarine canyon sedimentary system is divided into two subfacies:canyon filling and canyon edge.The canyon filling subfacies comprises four microfacies:turbidity channel,lag deposit,laterally inclined deposit,and mass-flow transport deposit(MTD).The canyon edge subfacies includes three microfacies:natural levee deposit,turbidite fan,and MTD.Analysis of sedimentary units and BSR distribution in the Shenhu canyon group reveals that natural levee deposit and MTD microfacies are favorable for hydrate enrichment in the canyon sedimentary system since the Pliocene.Based on the position and characteristics of BSR in these facies belts,three BSR types are identified:A-type(ridge dome pattern),B-type(ridge edge straight pattern),and C-type(canyon edge gradient change pattern).Considering the geological hazard mechanism of potential submarine landslides caused by gas hydrate decomposition,C-type BSR is identified as a high-risk area for hydrate-induced collapse.This is due to its increasing apparent dip angle and thinning overlying strata.The research results provide important data and technological support for the next phase of gas hydrate pilot production,especially in evaluating and predicting environmental stability in the Shenhu area.

northern South China SeaShenhu canyongas hydratesedimentary systemBSRlandslide

聂鑫、杜文波、高红芳、胡小三、杨楚鹏、鞠东

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中国地质调查局广州海洋地质调查局,自然资源部海底矿产资源重点实验室,广东广州,511458

天然气水合物勘查开发国家工程研究中心,广东广州,511458

南海北部 神狐峡谷 天然气水合物 沉积体系 BSR 滑坡

国家自然科学基金项目国家自然科学基金项目中国地质调查局地质调查项目中国地质调查局地质调查项目中国地质调查局地质调查项目中国地质调查局地质调查项目

U190121491958212DD20240090DD20221712DD20221719GZH201100206

2024

10.19762/j.cnki.dizhixuebao.2024199

地质学报
中国地质学会

地质学报

CSTPCD北大核心
影响因子：2.17
ISSN：0001-5717
年,卷(期)：2024.98(9)
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