ABSTRACT
There are many advantages in the underground gas
storage, such as system optimization for the gas-
supply, skeleton line and the compressed air station
investment reduction, the seasonal peak regulation,
the accident emergency and strategic reserves and so
on. The numbers and capacities of underground gas
storage keep increasing year by year. At present,
there are more than 600 underground gas storages
worldwide, and more than 76% of them are rebuilt
from the depleted single-porosity oil/gas reservoir.
The alternated gas injection and production of un-
derground gas storage operation in the depleted frac-
tured oil/gas reservoir, which causes repeated in-
crease and decrease of the reservoir pressure creates
the elastic-plastic deformation of underground gas
storage rock. The fractures are the main storage
space and the seepage channel for the injected gas in
the depleted fractured oil reservoirs. From gas con-
centration there is difference in fracture system and
in matrix system, which induces molecule diffusion.
The crude oil dissolves natural gas in the matrix
blocks which causes the inflation of the matrix, and
gas flow back into the fractures. As a result, oil re-
covery is enhanced.
