In the attached paper, the authors assumed that hydrate is part of the pore, which can be illustrated by equation (6), Sg+Sw+Sh=1, in their paper. However, the authors described Fig.5 as "The figure indicates the porosity increases with time during the process of gas hydrate dissociation due to the increment of the pore space".

In my view, if hydrate is viewed as a part of pore, then the pore space is independent of hydrate saturation. The pore space will increase only if the pore pressure is increasing, which will result in the compression of rock particles, thus increasing the pore space.

Do I have a wrong understanding of this point?