Estimation of gas hydrate saturation at the slope in the northwest of South China Sea

Lack of drilling and inversion data is therefore difficult to calculate hydrate saturation in the region of interest. There remains no effective solution in the literature. This study combines the method of impedance index calculation and one-dimensional forward modeling to estimate the upper and lower limits of hydrate saturation. In the current work, the calculation of hydrate saturation includes three steps: (1) The relationship between hydrate saturation and P-wave impedance by equivalent medium theory is established and then is converted into the relationship between hydrate saturation and impedance index. (2) Impedance index of water-bearing and hydrate formation is obtained from the velocity model based on the forward modeling. (3) The upper and lower limits of hydrate saturation are obtained by plugging in the impedance index into the equation of hydrate saturation. This method is just apt for the situation with the range of porosity from 30% to 70%, velocity of matrix grains from 30% to 70%, and in-phase reflections. This study demonstrates that the upper and lower limits of hydrate saturation can be obtained in the region lack of drilling and inversion data.