海洋天然气水合物系统动态调整的异常特征及主控因素  

Anomalous features and controlling factors on the dynamic adjustment of marine gas hydrate system

作　　者：王秀娟 王文录 靳佳澎 周吉林 匡増桂 胡高伟 张正一 李三忠[1,2] WANG Xiujuan;WANG Wenlu;JIN Jiapeng;ZHOU Jilin;KUANG Zenggui;HU Gaowei;ZHANG Zhengyi;LI Sanzhong(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Laboratory of Submarine Geosciences and Prospecting Techniques,MOE and College of Marine Geosciences,Ocean University of China,Qingdao,Shandong 266100,China;Laboratory for Marine Mineral Resources,Laoshan Laboratory,Qingdao,Shandong 266237,China;National Engineering Research Center for Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou,Guangdong 511458,China;Key Laboratory of Gas Hydrate,Ministry of Natural Resources,Qingdao Institute of Marine Geology,China Geological Survey,Qingdao,Shandong 266237,China)

机构地区：[1]深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,山东青岛266100 [2]海洋矿产资源评价与探测技术功能实验室,崂山实验室,山东青岛266237 [3]天然气水合物勘查开发国家工程研究中心,中国地质调查局广州海洋地质调查局,广东广州511458 [4]自然资源部天然气水合物重点实验室,中国地质调查局青岛海洋地质研究所,山东青岛266237

出　　处：《地质学报》2024年第9期2541-2556,共16页Acta Geologica Sinica

基　　金：国家重点研发计划项目(编号2023YFE0119900);国家自然科学基金项目(编号42376058,42276229);中国海洋大学筑峰人才项目联合资助的成果。

摘　　要：似海底反射(bottom simulating reflectors,BSRs)是指示天然气水合物赋存深度的重要标识,已在全球多个海域研究中发现了千年时间尺度上天然气水合物系统的动态调整,地震剖面上的典型表征是存在多种类型BSR及埋深变化。本文对比分析全球典型海域BSR的地震反射特征及测井响应差异,提出BSR调整及发育的主控因素为:①冰期—间冰期旋回、快速沉积、逆冲-褶皱与基底隆升,导致稳定带底界或BSR发生调整;②构造活动释放的热流体导致BSR上移;③海底侵蚀作用、地层超压,导致BSR下移等;④重烃气体形成Ⅱ型水合物,甲烷水合物稳定带底界下部出现水合物与游离气共存层;⑤合适温度条件下细粒沉积物发生矿物相变,形成与水合物无关的双BSR;⑥局部热异常会导致同一水平地层从含天然气水合物向游离气变化,横向上出现极性反转,无BSR调整。不同因素导致的稳定带底界调整,会伴随着水合物的形成—分解—再形成的动态变化,导致地层内水合物-游离气-水的三相共存,同时伴随着多层游离气的复杂分布,在地震剖面上呈现出多种类型BSR,指示天然气水合物系统复杂性及其与游离气间的相互影响。Bottom simulating reflectors(BSRs)are crucial indicators of gas hydrate occurrences.Seismic profiles from oceans worldwide reveal diverse BSR types and depths,demonstrating the dynamic adjustment of gas hydrate systems on millennial timescales.This study compares and analyzes the seismic reflection characteristics and logging responses of different BSR types.Several key factors contribute to BSR shifts:①Fluctuations in sea level and seafloor temperature during glacial-interglacial cycles,coupled with rapid shallow sediment deposition,thrust folding,and basement uplift,can cause upward or downward BSR adjustments;②Thermal fluid release from late tectonic activity can drive BSRs upward shift;③Submarine erosion and formation overpressure can lead to BSR downward shift;④Due to active heavy gas leakage from deep strata,structure II hydrate readily forms.This results in the coexistence of hydrate and free gas at the base of the gas hydrate stability zone(BGHSZ)for methane;⑤Double BSRs formed by mineral phase transitions are unrelated to gas hydrate in fine-grained sediments;⑥Local thermal anomalies can cause the transition from gas hydrate to free gas layer within the same horizontal layer,showing a horizontal polarity reversal without BSR adjustment.Therefore,the dynamic adjustment of the BGHSZ reflects the continuous interplay of gas hydrate formation,decomposition,and reformation,which shows the three-phase coexistence of hydrate-free gas-water and the multiple shallow gas distributions.This results in various types of BSRs observed on seismic profiles,indicating the complexity of gas hydrate systems and their interplay with free gas.

关 键 词：天然气水合物 游离气 BSR 三相共存 动态调整 

分 类 号：P618.13[天文地球—矿床学]