| The prediction of pressure drop and water inflow rate at bottom hole of dewatering gas-producing wells is of particular interest to field engineers. With fringe water and bottom water invading gas reservoir, many wells produce gas and water at the same time, so they are usually equipped with artificial-lift systems such as gas lift. To design parameters for these systems, a model to predict two-phase flow pressure gradients and water inflow rate is required. Although extensive research in two-phase flow has been conducted, most of this research has concentrated on steady-state two-phase flow. But gas and water usually inflow under unsteady-state conditions, so they flow in tubing at unsteady-state. There is still a lot of work to do on unsteady-state two-phase flow.The phenomena of gas and water filering flow in fractured formation is described in this paper. A simple model of gas and water filering flow is established and the mechanism of gas and water filering flow based on energy and momentum in fractured formation is analysed, thus the understanding of gas and water filering flow law is improved.A new model for prediction of pressure drop and water inflow rate at bottom hole in gas producing wells is presented. The slippage effect of two phase and the transition mechanisms among different flow patterns are taken into consideration. The wellbore is divided into a number of segments whose pressure drop and space distribution of gas-liquid with time under unsteady-state flow conditions is calculated iteratively by using transient steady flow method. At last, the relationships of bottom-hole pressure and water inflow rate changing with time are established.The new model has been tested against several gas wells. The validity of the unsteady-state model is demonstrated by comparison with results of other steady models and it shows an outstanding performance for pressure drop prediction and water inflow rate prediction under unsteady-state two-phase flow conditions. |
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