Investigation of Underground Gas Storage in a Partially Depleted Naturally Fractured Gas Reservoir

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In this work, studies of underground gas storage (UGS) were performed on a partially depleted, naturally fractured gas reservoir through compositional simulation. Reservoir dynamic model was calibrated by history matching of about 20 years of researvoir production. Effects of fracture parameters, i.e. fracture shape factor, fracture permeability and porosity were studied. Results showed that distribution of fracture density affects flow and production of water, but not that of gas, through porous medium. However, due to high mobility of gas, the gas production and reservoir average pressure are insensitive to fracture shape factor. Also, it was found that uniform fracture permeability distribution enhances communication within reservoir and consequently more pressure support is obtained by water bearing of aquifer. Effect of aquifer on the reservoir performance was studied, and it was found that an active aquifer can reduce condensate drop out around the well bore. On the other hand, water invasion is an important issue which may kill the well. Results showed that use of horizontal wells is superior to vertical wells in order to avoid detrimental effects of active aquifer.