Application of fractional flow equation in fracture—cave typed reservoir of Tahe oilfield

Based on the simplified double porous media of frac- ture-cave typed carbonate reservoir,the fractional flow equation of fracture system under effect of gravity is brought up to analyze the contributing factors of water cut.The result shows that the characteristics of under- ground oil and water seepage in fracture-cave reservoir is quite different from that in homogeneous pore system dur- ing production period because the water cut is under great effect of gravity in fracture-cave reservoir.When the production pressure difference is not larger than the criti- cal pressure difference too much,and the production pres- sure difference is decreased slightly,the water cut can be decreased much rapidly,which explains why the closure of well leads to mild increasing trend of water cut change.