【作者】 邓辉；

【导师】 阎贫；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 构造地质学， 2006， 博士

【摘要】 台湾西南海域位于新生代东亚聚敛边缘,也是天然气水合物发育的有利地区。为利用反射地震属性研究天然气水合物,本文在常规地震处理发现BSR的基础上开展了:(1) AVO分析及AVO反演,获得了多属性地震特征;(2) 多属性地震特征与水合物的关系研究,建立天然气水合物多属性地震识别标志;(3) 水合物的成藏模式探讨。 AVO反演结果表明在本区地震记录的强BSR振幅部位,纵波反射系数、梯度、泊松比变化率、纵波速度变化率、纵波波阻抗变化率、流体因子为相对高负值区,而横波反射系数、横波速度变化率及横波波阻抗变化率接近于零。根据上述地震特征,推断BSR上方可能存在水合物,其中在强BSR振幅部位,下方可能存在含气层,在相对弱振幅部位下方无含气层,或者为低含气饱和度的地层。 BSR分布于增生楔部位,受区域构造沉积条件控制明显。在增生楔部位,地层深部的流体(热液及甲烷气体等),在挤压构造应力及浮力的作用下,沿断层及地层孔隙运移至海底浅层,形成水合物。挤压构造应力的差异导致甲烷气供应量及热流值的差异,进而导致沿L973线增生楔由西向东水合物及其下方游离气饱和度的横向变化。 本文在台湾西南海域首次开展AVO反演技术的水合物应用研究,利用反射地震多信息识别天然气水合物,研究具有先导性及创新性。该区域首次获得的长排列地震资料也提供了更高的分析可靠性。更多还原

【Abstract】 Located in the Cenozoic convergent margin of East Asian, Southwest Taiwan is a favorable area of gas hydrate. To study gas hydrate over this area using reflection seismic methods, the following work is conducted on the basis of identifying BSR in the conventional migrated profile in this thesis: (1) AVO analysis and AVO inversion are carried out to obtain multiple seismic attributes;(2) the relationship of gas hydrate to the seismic attributes are researched to find the signatures for identifying gas hydrate;(3) the reservoir model of gas hydrate is primarily discussed. AVO inversion shows that the P-wave reflection coefficient, the gradient, the Poisson’s ratio reflectivity, the P-wave velocity reflectivity, the P-wave impedance reflectivity and the fluid factor are high negative where the BSRs are strong. However, the S-wave coefficient, the S-wave velocity reflectivity and the S-wave impedance reflectivity approximately equal zero in the same strong BSR section.The seismic attributes above imply that gas hydrate layer may exist above the strong BSR and free gas layer below it, and the sediment layer with no free gas or very low gas saturation may occur beneath the weaker BSR.The BSRs are distributed over the accretionary wedge, clearly controlled by tectonic and sedimentation conditions. Drived by tectonic compressional stress and buoyancy force, deep fluid(warm liquid, methane and so on) migrates up along faults and porosity in the sediments, and gas hydrate is formed in the shallow sediments of accretionary wedge. The lateral variations of methane supply and heat flow value are caused by the differential compression, thus constraining on the lateral variations of gas hydrate and free gas saturation in the sediments below it from west to east in the accretionary wedge of L973.AVO inversion techniques are firstly applied to identifying gas hydrate byseismic attributes offshore Southwest Taiwan in the thesis, which is of trial and innovation. And the larger streamer data collected for the first time supply more confidence for the analysis.更多还原