The present work demonstrates a case study in the Mahanadi offshore basin in the eastern margin of India, where gas hydrates have been delineated by seismic experiment, mainly by identifying a bottom simulating reflector or BSR on seismic section, based on its characteristic features. The BSR represents an acoustic impedance contrast between the high-velocity gas hydrates bearing sediments above and low-velocity gas-bearing or water-saturated sediments below. At some places along the continental margins of the world, the BSR has not been identified but gas hydrates were recovered by drilling, whereas at some other places BSR was identified but no gas hydrates were found. Thus, we need to find out an attribute that can be used to characterise gas hydrates and free gas reservoirs. The purpose of this work is to demonstrate this through spectral decomposition in the time–frequency domain. The study based on continuous wavelet transform (CWT) approach, which uses a mathematical mother wavelet, shows the illuminated zone with higher energy low-frequency anomaly, associated with free gas below the BSR. The study demonstrates that the CWT technique provides higher spectral-spatial resolution than that obtained by the short-term Fourier transform technique.

目前的工作以印度东部边缘的 Mahanadi 近海盆地为案例研究，该盆地已通过地震实验圈定天然气水合物，主要是根据其特征在地震剖面上识别底部模拟反射体或 BSR。BSR 代表了上面带有沉积物的高速气体水合物与下面的带有低速气体或水饱和沉积物之间的声阻抗对比。在世界大陆边缘的一些地方，BSR 尚未发现，但通过钻井开采了天然气水合物，而在其他一些地方，BSR 被发现但未发现天然气水合物。因此，我们需要找到一个可以用来表征天然气水合物和游离气藏的属性。这项工作的目的是通过时频域中的频谱分解来证明这一点。基于连续小波变换 (CWT) 方法的研究，使用数学母小波，显示了具有较高能量低频异常的照明区域，与 BSR 以下的游离气体相关。该研究表明，CWT 技术提供了比短期傅里叶变换技术更高的光谱空间分辨率。