N. Kilincer et F. Gumrah, A numerical simulation study on mixing of inert cushion gas with working gas in an underground gas storage reservoir, ENERG SOURC, 22(10), 2000, pp. 869-879
The cushion gas, providing the pressure energy necessary for withdrawal of
working gas, makes up the largest part of the investment in underground gas
storage projects. The suggested method of reducing this cost is the replac
ement of some part of the cushion gas with less expensive inert gas, such a
s nitrogen. In the replacement, there might be some problems due to mixing
between natural gas and inert gas. Turkey has sharply increasing demand for
natural gas. The constant imported gas and varying demand throughout the y
ear due to the distinct seasons in the region are the reasons for severe ne
ed for gas storage in Turkey. There are no underground storage units in Tur
key but two gas reservoirs in the Thrace basin grant the potential for gas
storage. From this point of view, the gas mixing problem is investigated fo
r a typical gas reservoir by coupled use of a gas reservoir simulator and a
transport model. A two-dimensional (2-D), single-phase numerical gas reser
voir simulator is developed to obtain the pressure distribution during prod
uction and injection cycles. The velocity distribution is found by using th
ese pressures. Then the two-dimensional transport model is used to calculat
e nitrogen concentrations around the injection wells. Both models are used
effectively for controlling the mixing problem in an underground gas storag
e reservoir.