天然气水合物和游离气层的弹性参数异常特征及其在饱和度估算中的应用

Anomalous feature of elastic parameters in sediments with gas-hydrate and free gas and application in estimation of saturation

与水饱和沉积层相比,天然气水合物和游离气储集层的地震波速度、泊松比、弹性模量及其比值等弹性参数具有明显的异常特征。对于接触胶结水合物层来说,对饱和度变化最为敏感的弹性参数是横波速度和横波波阻抗;对于非接触胶结水合物层来说,对饱和度变化最为敏感的参数是弹性模量比和纵波速度;对于游离气层来说,对饱和度变化最为敏感的弹性参数是弹性模量比和泊松比。当水合物与岩石骨架呈接触胶结时,水合物层在速度和波阻抗剖面上表现为近似平行于海底的高值异常带,而泊松比剖面却无明显异常。利用对饱和度变化敏感的弹性参数估算水合物和游离气饱和度的精度较高。依据对美国布莱克海台区USGS95-1测线的地震数据进行水合物分析研究,发现该地区的水合物是接触胶结类型,得到该地区的水合物饱和度最大可达20%;下伏游离气层的含量小于2%。

Comparing with water-saturated sediments, such elastic parameters as velocity of seismic waves, Poisson ratio, elastic module and ratio of elastic module in sediments with gas-hydrate and free gas have clearly anomalous feature. For contact-cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are S-wave velocity and wave impedance; For non-contact cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and P-w...