WATER BREAKTHROUGH SIMULATION IN NATURALLY FRACTURED GAS RESERVOIRS WITH WATER DRIVE

In the fractured water drive reservoirs of China, because of the complex geological conditions, almost all the active water invasions appear to be water breakthrough along fractures, especially along macrofractures. These seal the path of gas flow, thus the remaining gas in the pores mixes into water, and leads 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 reservoir produces gas, or the same gas well produces water intermittently. It is very difficult to explain these phenomena using existing fracture models because of their simple handling macrofractures without considering nonlinear flowing in the macrofractures and the low permeability matrix. Therefore, a nonlinear combined-flowing multimedia simulation model was successfully developed in this paper by introducing the equations of macrofractures and considering nonlinear flow in the macrofractures and the matrix. This model was then applied to actual fractured bottom water gas fields. Sensitivity studies of gas production by water drainage in fractured gas reservoirs were completed and the effect of different water drainage intensity and ways on actual gas production using this model were calculated. This model has been extensively used to predict the production performance in various fractured gas fields and proven to be reliable.