Study on the Swelling Characteristics of the Offshore Natural Gas Hydrate Reservoir

The swelling characteristics of porous media in the offshore natural gas hydrate reservoir have an important effect on the stability of the reservoir. In this work, the physical property and the swelling of porous media in the offshore natural gas hydrate reservoir were measured. The results show that the swelling characteristics of the offshore natural gas hydrate reservoir are influenced by the coupling of the montmorillonite content and the salt ion concentration. The swelling rate of porous media is directly proportionate to water content and the initial porosity, and inversely proportionate to salinity. Compared with water content and salinity, the initial porosity has much obvious influence on the swelling, which the swelling strain of porous media with the initial porosity of 30% is three times more than that of montmorillonite with the initial porosity of 60%. Salt ions mainly affect the swelling of water bound by porous media. Then, the influence mechanism of the swelling characteristics of porous media on the structural characteristics of reservoir was tentatively explored. It can provide a basic date and scientific basis for furthering the mechanical characteristics of the reservoir in the hydrate exploitation in the offshore gas hydrate reservoir.