Study of constant-pressure production characteristics of class 1 methane hydrate reservoirs

A three-dimensional, compositional, multiphase flow simulator for methane-hydrate reservoirs is developed in this study. It is used to study the production characteristics of class 1 methane-hydrate reservoirs. The effects of well-completion location, well spacing, and production schedule on gas production efficiency are also examined. All simulation studies in this work implement a constant bottom-hole pressure (at 14.7 psia) as a production scheme for exploring maximum production capacity from the reservoir. The simulation study shows that the presence of gas hydrate on top of a conventional gas reservoir can dramatically improve gas productivity. Unlike conventional gas reservoirs, the water production rate of gas-hydrate reservoirs increases with time (when a constant bottom-hole pressure is implemented as a production scheme). Moreover, it shows that moving well-completion location in free-gas zone (in relation to the movement of the interface between free-gas and hydrate zones) provides better production performance and the best completion location is in the middle of free gas zone. As expected, the results also show that smaller well spacing yields higher gas production. However, for a particular system used in this work, it does not show substantial improvement of production efficiency. For a multiple-well system, the simulation results indicate that production efficiency can be improved by putting the wells on production at different times.