Experimental Investigation on the Imbibition Capacity and Its Influencing Factors in Hydrate Sediments.

The water generated after the dissociation of gas hydrates is spontaneously imbibed into the matrix pores. It hinders the gas-water flow and decreases the pore pressure, which is not conducive to the continuous depressurization of hydrate sediments. However, there are few research studies on the imbibition capacity and the influencing factors of hydrate sediments. In this paper, spontaneous imbibition experiments are carried out on the samples of hydrate sediments. The imbibition capacity and its influencing factors are analyzed. The results show that as the spontaneous imbibition time increases, the peak of the T2 spectra also shifts to the right, indicating the formation of new larger-sized pores. When the imbibition time exceeds the critical point, the hydrate sediments instantly disperse and reach the maximum imbibition capacity status. The influencing factors of the imbibition capacity include the moisture content, dry-wet cycle, clay minerals content, solution salinity, permeability, and porosity. With the increase of the clay mineral content, the imbibition capacity increases rapidly, and the I/S mixed layer can significantly improve the imbibition capacity. As the number of dry-wet cycles increases, the imbibition capacity gradually increases. In addition, the imbibition capacity is inversely related to the moisture content and the solution salinity. Porosity and permeability have little effect on the imbibition capacity. This study is of great significance for understanding dissociation water retention and optimizing hydrate exploitation systems.