WATER BREAKTHROUGH SIMULATION IN NATURALLY FRACTURED GAS RESERVOIRS WITH WATER DRIVE

In the fractured water drive reservoirs of China, because of the comp lex geological conditions, almost all the active water invasions appear to be wa ter breakthrough along fractures, especially along macrofractures. These seal th e path of gas flow, thus the remaining gas in the pores mixes into water, and le ads to gas-water interactive distribution in the fractured gas reservoir. These complicated fractured systems usually generate some abnormal flowing phenomena such as the crestal well produces water while the downdip well in the same gas r eservoir produces gas, or the same gas well produces water intermittently. It is very difficult to explain these phenomena using existing fracture models becaus e of their simple handling macrofractures without considering nonlinear flowing in the macrofractures and the low permeability matrix. Therefore, a nonlinear co mbined-flowing multimedia simulation model was successfully developed in this p aper by introducing the equations of macrofractures and considering nonlinear fl ow in the macrofractures and the matrix. This model was then applied to actu al fractured bottom water gas fields. Sensitivity studies of gas production by water drainage in fractured gas reservoirs were completed and the effect of diff erent water drainage intensity and ways on actual gas production using this mode l were calculated. This model has been extensively used to predict the productio n performance in various fractured gas fields and proven to be reliable.