Behaviour of Gas Production from Type III Hydrate Reservoirs

MEHRAN POOLADI-DARVISH*,**, OLGA ZATSEPINA**, HUIFANG HONG**, *UNIVERSITY OF CALGARY, **FEKETE ASSOCIATES INC.

Copyright 2008, International Conference on Gas Hydrates

Proceedings of the 6th International Conference on Gas Hydrates (ICGH 2008), Vancouver, British Columbia, CANADA, July 6-10, 2008.

A large number of studies are underway to evaluate the possible role of gas hydrates as a potential energy resource. One class of such studies involves development and use of mathematical models (i) to estimate the rate of gas production from hydrate reservoirs under different operating conditions and (ii) to better understand the role of different parameters on hydrate decomposition. A number of researchers1-4 have already studied gas production from those hydrate reservoirs that have an underlying free-gas phase (Type I). However the study of gas production from those hydrate-reservoirs that totally lie within the hydrate stability zone and are sandwiched by impermeable layers on top and bottom (Type III) have received less attention. Furthermore, while gas production rates from Type I hydrate reservoirs have been found to be significant, the results for Type III gas hydrate reservoirs are less promising. In this study, a gas hydrate reservoir simulator is used to study gas production from Type III hydrate reservoirs. A large number of mechanistic and sensitivity studies have been conducted to better understand the factors controlling rate of gas production. It is shown that the ability to decompose hydrate at a significant rate not only depends on the rate of heat transfer (as in Type I reservoirs) but also on the ability of the formation to allow fluid flow. (This is a much less important factor for Type I reservoirs). In this work, the interaction between fluid flow and heat transfer is explored, and conditions that would allow significant gas production rate are illustrated. The challenges in numerical modeling of Type III hydrate reservoirs have also been described.