Experimental Study on the Dissociation Behavior and Productivity of Gas Hydrate by Brine Injection Scheme in Porous Rock

摘要

This study presents the experimental apparatus to analyze the dissociating phenomena of gas hydrate in porous rock. The experiments by brine injection scheme have been carried out in a way that can allow for the analysis of dissociation characteristics and how various brine concentrations and permeabilities affect the gas productivity. With the experiments, the pressure and flow behavior have been investigated during the dissociation period, as well as the productivity of dissociated gas from gas hydrate. As a result, it has been observed that, if the brine concentration is excessively high, the gas production rate tends to reduce significantly. This means that excessive NaCl molecules disturb the fluid flow between pores and, thus, significantly reduce the permeability. In the experiment with varying permeability, an increase in the permeability caused an increase in the gas production and a decrease in the dissociation rate. A difference in the production rate was also observed up to 35%. Therefore, it is experimentally verified that the permeability of the rock, which describes the connectivity of pores, is one of the most important factors that influence production from gas hydrates. It suggests that, during gas production from a gas hydrate reservoir, the dissociation methods must be conducive to increase or at least maintain the reservoir permeability.