摘要
全球多个海域钻探表明天然气水合物与游离气共存,不同共存层的地球物理异常特征与富集程度存在差异,形成识别共存层的方法有利于准确评价天然气水合物资源量。本文分析了南海与国际典型井位的多种测井与地震资料,总结了4种类型的天然气水合物与游离气共存层,包括细粒泥质储层稳定带附近共存、细粒泥质粉砂储层水合物稳定区底界(BSR)下方共存、细粒泥质储层冷泉发育区天然气水合物稳定带内共存和粗粒砂质储层快速沉积区天然气水合物与游离气共存。对比不同储层类型异常特征变化,通过多种属性联合与交会分析形成识别共存层天然气水合物赋存形态方法。结果表明,生物成因气与热成因气都能形成天然气水合物与游离气共存。在生物成因气发育区,由于快速沉积作用导致天然气水合物稳定带底界向上调整,天然气水合物发生分解。因分解需要时间,在一定时期内的局部区域会出现天然气水合物与游离气共存。而热成因气发育区,易形成Ⅱ型天然气水合物与游离气共存。利用孔隙度、电阻率与饱和水层的差异进行交会分析,根据曲线变化趋势能识别共存层天然气水合物的赋存形态,多种地球物理属性对比分析认为横波速度是识别共存层天然气水合物与游离气富集差异的关键参数。
Numerous drilling expeditions in the world's oceans have confirmed the coexistence of gas hydrate and free gas.The geophysical anomalies and enrichment patterns of these coexistence zones vary across different regions,making their identification crucial for accurately evaluating gas hydrate resources.This study analyzes a variety of logging and seismic data from typical drilling sites in the South China Sea and other global oceans to explore the geophysical characteristics of gas hydrate and free gas coexistence zones.Four distinct types of coexistence are identified:(1)coexistence near the base of the gas hydrate stability zone(BGHSZ)in fine-grained,clay-rich reservoirs;(2)coexistence below the bottom simulating reflector(BSR)in fine-grained,clayey silt reservoirs;(3)coexistence above the BGHSZ in cold seep systems;and(4)coexistence in coarse-grained sand reservoirs in high-sedimentation zones.Crossplot analysis and intersection analysis of multiple attributes are effective methods for identifying these coexistence zones.The results indicate that both biogenic and thermogenic gases contribute to the coexistence of gas hydrate and free gas.In gas hydrate systems formed by biogenic gas,high sedimentation rates cause the BGHSZ to shift upward,leading to gas hydrate dissociation.However,this dissociation process requires time,and localized coexistence of gas hydrate and free gas may occur during specific periods.In contrast,gas hydrate systems formed by thermogenic gas often display widespread coexistence of structure Ⅱ gas hydrate and free gas due to distinct controlling factors.The study highlights that crossplots of porosity and resistivity contrast versus water-saturated layers can be used to identify gas hydrate morphologies based on changing trends within coexistence zones.Additionally,geophysical property analysis reveals that S-wave velocity is a key parameter for distinguishing between gas hydrate and free gas enrichment in these zones.This research provides valuable insights into geophysical characteristics and identification methods for gas hydrate and free gas coexistence zones,contributing to the accurate evaluation of gas hydrate resources.
作者
王秀娟
韩磊
刘俊州
靳佳澎
匡增桂
周吉林
WANG Xiujuan;HAN Lei;LIU Junzhou;JIN Jiapeng;KUANG Zenggui;ZHOU Jilin(State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing 102206,China;Sinopec Key Laboratory of Seismic Elastic Wave Technology,Beijing 102206,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,Ocean University of China,Qingdao 266100,China;Sinopec Petroleum Exploration and Production Research Institute,Beijing 100083,China;Laboratory for Marine Mineral Resources,Laoshan Laboratory,Qingdao 266237,China;National Engineering Research Center of Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,Guangzhou 511458,China)
出处
《地学前缘》
北大核心
2025年第2期20-35,共16页
Earth Science Frontiers
基金
中国石化弹性波理论与探测技术重点实验室开放基金课题项目(3355000-22-ZC0613-0384)
国家自然科学基金项目(42376058,42206063)。
关键词
天然气水合物
游离气
共存
横波速度
交会分析
gas hydrate
free gas
coexistence
shear wave velocity
crossplot analysis
