Study of production of Class Ⅱ hydrate reservoir by hot water flooding

As a kind of new energy source, natural gas hydrates are widely distributed in both permafrost and deep ocean sediments. Among different types of hydrate reservoirs, the Class Ⅱ hydrate reservoir is the most prevalent production target. In order to study the behavior of the Class Ⅱ hydrate reservoir in production, this paper investigated the hydrate reservoir production using the hot water flooding method according to the parameters reported in literatures. The results are compared with those by the depressurization method. The results show: 1) when the Class Ⅱ hydrate reservoir is developed by hot water flooding, the gas production rate increases rapidly in the early stage, and then declines until it reaches a relatively stable level. The gas dissociation rate varies similarly to the gas production rate. The cumulative produced gas and dissociated gas increase rapidly at first, and then increase linearly. Both the gas recovery percent and hydrate dissociation percent remain on high levels (＞60%). 2) the hot water flooding method is suitable for the Class Ⅱ hydrate reservoir development. Compared with the depressurization method, the hot water flooding method can achieve higher gas recovery percent and hydrate dissociation percent. But the gas-water ratio is higher, indicating a larger amount of water production.