Identification and saturation calculation of hydrate bearing gas layer in ultra-shallow loose sandstone in deep water

In the process of marine gas hydrate exploration, the electrical response characteristics of hydrate-bearing gas layers are extremely complex, which leads to great difficulties in the qualitative identification and quantitative evaluation of hydrate-bearing gas layers. Therefore, based on the logging response characteristics of deep-water ultra-shallow loose sandstone hydrate gas reservoirs in the South China Sea, combined with qualitative identification methods such as porosity difference method, neutron-density curve overlapping method, shear modulus method, etc., the saturation of hydrate gas layers was identified and the method of inverting longitudinal wave velocity and resistivity at the same time to find the minimum joint error was used to solve the saturation of hydrate gas layers. The results show that the method of joint inversion of acoustic wave and resistivity logging to calculate the saturation of hydrate gas layer is feasible and reliable, and the hydrate saturation and shallow gas saturation can be calculated at the same time, the calculation results of the joint inversion of Well Z in block L are in agreement with the core saturation of 81.25%, and the joint inversion results of Well Y in block L are in agreement with the calculation results of hydrate or shallow gas calculation model alone by nearly 85%, which can provide a reference for the identification of hydrate gas layers and the calculation of saturation in the field.