关键词: 天然气水合物, 叠前反演, 波阻抗属性, 坐标旋转, 储层预测

Abstract: Seabed sediments containing gas hydrate usually have high compressional and shear wave velocity and low density, while only wave impedance attributes can be acquired by conventional post-stack impedance inversion. Due to the low density of hydrates, the wave impedance of hydrate-bearing formation was superimposed with that of surrounding formation to a certain extent. Therefore, there was some error in identification of hydrate reservoirs by post-stack wave impedance. In order to improve the prediction accuracy of gas hydrate ore body, the pre-stack inversion technology was proposed to improve the low prediction accuracy of gas hydrate reservoirs. The sensitive elastic parameters of the gas hydrate reservoir were determined through the petrophysical analysis, and the gas hydrate and gaseous hydrocarbon reservoir were predicted with the pre-stack inversion technology on the basis of seismic trace set optimization, fine synthetic record calibration and initial model establishment. The results of the study show that The intersection of compressional and shear wave velocity was the most sensitive elastic parameter to identify the reservoir in the study area, and the identification factor of compressional and shear wave velocity was reconstructed based on the coordinate rotation technology and effective in identifying the reservoirs and characterizing the hydrate and gaseous hydrocarbon reservoirs clearly. The prediction results show that the natural gas hydrate ore body in the study area struck nearly from south to north, and the hydrate and gaseous hydrocarbon were relatively developed in the south of the ore body, which was in line with the drilling conditions. The prediction results can provide a reliable basis for hydrate reservoir calculation in terms of area and thickness.

Key words: natural gas hydrate, pre-stack inversion, wave impedance attribute, coordinate rotation, reservoir prediction