Abstarct: One of the most important problem of petroleum reservoirs is water entering to the reservoir as a result of coning phenomenon and its simultaneous flow with oil through the wellbore. Since this phenomenon declines ultimate oil recovery and increases in operation costs, understanding and prediction of petroleum reservoirs behavior in regard to this phenomenon is crucial. This study investigates water coning phenomenon in fractured reservoir. using ECLIPSE package by implementing dual porosity model. Firstly coning phenomenon was simulated then critical oil flow rate and water breakthrough time were estimated for one oil well. Also effect of carbonate reservoir rock properties like matrix and fracture permeability and porosity were investigated on water breakthrough time. Then by Spider plot, some of the effective parameters like density difference, viscosity, vertical to horizontal permeability ratio and production rate which affect on the amount of oil and water production were studied. Results of simulation specify 1400 day as a water breakthrough time and 1000 bbl/day as a critical oil flow rate for studied well. Also it has been found that increase of density difference any reduction of oil viscosity, permeability ratio and oil flow rate, decreases water production. The obtained results also indicate that oil flow rate and vertical permeability of fracture have most effect while any increase of rock wettability (in case of oil-wet rock) has the least effect on water coning phenomenon.