Abstract: The key of using horizontal well to develop bottom water reservoir is to determine the critical production. Based on the analysis of water coning mechanism, the 3D percolation field of horizontal well is approximately divided into two parts including internal and external percolation fields. The two streamline distributions are analyzed. First, the Dupuit formula is used to get the formula of critical production for external field. Second, the horizontal length is taken as "reservoir thickness" and the distance between wellbore and reservoir top is taken as "drainage radius", and then the formula of critical production for internal field is given by using radial flow theory. Last, combining with the rule of equivalent filtrational resistance, a new method for calculation of the critical production of a horizontal well in bottom water reservoir is proposed. The case study is conducted and the comparisons among the different methods are presented. The effects of anisotropy, horizontal length and ratio of horizontal section's vertical distance and reservoir thickness on the critical production are analyzed.

Key words: bottom water reservior, horizontal well, bottom water coning, critical production