木里地区天然气水合物地震属性分析

摘要

Seismic exploration of natural gas hydrate in permafrost regions in land field is a new field of energy exploration by seismic methods.In order to study the seismic attributes of natural gas hydrate in land field,the authors used the methods of seismic reflection and synthetic seismogram analysis with high precision,and then analyzed the seismic recordings for seismic attributes.The results of experimental research show that the seismic reflection wave group formed by formation of natural gas hydrate has the characteristics of higher frequency and weaker amplitude,and the synthetic seismogram and measured seismic profile are consistent well with each other.In the fluid model,the slope of the curve is positive with the amplitude of reflected waves from the top interface of the reservoir varying with the incident angle,and the slope of the curve is negative in the bottom interface.In contrast,the curve characteristics of the consolidation skeleton model are just the opposite.On the sections of instantaneous amplitude and instantaneous frequency,the amplitudes of frequency properties of reflected waves from the hydrate formation are consistent with those of seismic profiles.On the instantaneous phase section,the phase of reflected waves in hydrate formation has no obvious change,which indicates that the instantaneous phase properties do not reflect hydrate.The corresponding frequency of reflected waves in the high value regions of the energy half-time section is relatively high,which indicates that the energy attenuation is relatively strong when the reflected waves pass through the hydrate formation with a high degree of fragmentation.In conclusion,the results of this study will provide technical support for the seismic exploration of natural gas hydrate in China's permafrost area.%陆域冻土区天然气水合物地震勘探是应用地震方法进行能源勘探的新领域.为研究陆域天然气水合物的地震属性,开展了高精度反射地震、合成地震记录分析等方法技术研究,并对地震记录进行了有关地震属性分析.试验研究结果表明:含天然气水合物地层形成的地震反射波组具有主频较高、振幅较弱的特征,合成地震记录及实测地震剖面对应较好;在制作的流体模型中,储层顶界面反射波振幅随入射角的变化曲线斜率为正,底界面曲线斜率为负,固结骨架模型的曲线特征则刚好相反.在瞬时振幅、瞬时频率剖面上,含水合物地层反射波的振幅和频率属性与地震剖面一致,在瞬时相位剖面上,含水合物地层反射波的相位没有明显变化,表明瞬时相位属性对水合物反映不敏感;高值区的能量半衰时对应的反射波频率相对较高,表明反射波通过破碎程度较高的含水合物地层时,能量衰减相对较强.该研究结果将为我国陆域开展天然气水合物地震勘探提供技术支持.