Jeopardized by poor reservoir properties, gas wells in low permeability reservoirs with bottom water should be fractured in order to acquire industrial capacities. Therefore, a modified equation for predicting well's water breakthrough time is studied for effectively developing low permeability gas reservoirs with bottom water. Based on the characteristics of seepage flow in fractured wells, the seepage field is divided into two parts, the perforation interval and its lower section. With the aid of steady state seepage theory, productivity equations for all fields are derived respectively. Eventually, a modified prediction equation is established by means of utilizing the motion equation of water cone apex. Case study shows that fracturing will postpone the process of water breakthrough and the time calculated by this article has less error as compared with the value gained by practical production data. The analysis on sensitive factors reveals that each parameter has its optimal value. With the increase of perforation degree, water breakthrough time will increase at first and then decrease. And the larger the fracture half-length and conductivity are, the longer the water breakthrough time will be. However, the increasing rates tend to be reduced gradually.

low permeability  /  gas reservoir with bottom water  /  fractured well  /  finite conductivity  /  water breakthrough time