There have been several field tests
around the world to recover
natural gas from gas hydrate reservoirs. A most recent trial took
place in the South China Sea, breaking the records of cumulative and
daily gas yield from marine hydrate deposits. However, significant
challenges still remain while approaching commercial gas production.
These may involve but are not limited to the ultralow permeability
of the reservoir, insufficient heat supply, unstable gas yield fluctuations,
sand problem upon water production from the silty sediments, and secondary
hydrate formation or ice generation blocking the pore spaces. Consequently,
intensive efforts have been made to understand and, thereby, manipulate
the complicated gas production process. Of special interest are the
studies on the determination and optimization of the depressurization
scheme, because depressurization is recognized to be most promising
toward an economically efficient gas recovery. Therefore, in this
work, we elaborated on the effects of pressure regulation on the behavior
of gas and water yield and characteristics of the reservoir during
the gas production process through depressurization-based approaches.
Particular attention was paid on the enhancement of the gas production
rate and energy efficiency under various scenarios. The advantages
and limitations of the current investigation were also discussed to
present preliminary suggestions and perspectives for future studies.
This work could provide a brief view of the current efforts on improving
the gas production efficiency at a laboratory scale; further investigations
are still required to scale-up these findings to provide guidance
to the field test in the future.