Prediction of Water Breakthrough Time of Horizontal Wells in Gas Reservoirs with Bottom Water

Development of the horizontal well technology offers a new approach to exploitation of gas reservoirs with bottom water. The most important problem for a horizontal well in gas reservoir is water cresting which restricts the horizontal well to be developed effectively. Based on the imaging theory and potential energy superposition principle, a study on prediction of water breakthrough time of horizontal wells in gas reservoir with bottom water is presented. This paper derives the water breakthrough time formula and productivity of horizontal well in a reservoir with bottom water. In the process of derivation, factors, such as impermeable boundary on the top of the reservoir, equal pressure interface, anisotropy, height of water avoidance, all have influences on the potential distribution in the gas reservoirs with bottom water. The case study indicates that for a horizontal gas well with a constant production rate, the water breakthrough time is proportional to the height of water avoidance, and that the productivity of a horizontal well in gas reservoir with bottom water is affected by horizontal well location and formation anisotropy. The productivity of the horizontal well increases with the height of water avoidance but decreases with the vertical permeability. The results and the method are useful for gas reservoir engineering design and the theoretical study of horizontal well.