Two-phase correlation for multilateral well deliverability
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To predict well performance for multilateral wells, an inflow performance relationship (IPR) model is needed to calculate the flow rate and pressure distribution in the horizontal laterals. Several analytical models have been developed over the last 20 years to generate inflow performance relationships (IPR) for single-phase horizontal wells. Similar to vertical wells, analytical solutions for two-phase flow horizontal wells are unavailable because of the complexity of relative permeability and the variable phase distribution in the reservoir. Correlations, leading by Vogel's equation, have been used for two-phase IPR calculations for vertical wells, and the method can be adopted for multilateral/horizontal well applications. This paper presents a two-phase multilateral well model using a modified Vogel's equation to generate IPR curves for two-phase horizontal laterals and deliverability curves for multilateral wells. The modified two-phase inflow model uses Babu and Odeh's model3 to calculate the absolute open flow potential, q o,max, for a horizontal lateral, and then use the original Vogel's correlation to generate the relationship between flow rate and pressure. The reservoir anisotropy is considered in Babu and Odeh's model for horizontal well flow, and the wellbore pressure drop was considered interactively with the inflow performance along the wellbore. The overall performance then is presented as wellhead pressure versus total flow rate, flow rate from each lateral, and flow rate distribution along each lateral. The results of the deliverability model with the modified Vogel's correlation are compared with the results by a single phase analytical model for multilateral wells. Since the overall flow condition and the performance of a multilateral well is very sensitive to the pressure distribution in the well system, a two-phase inflow model provides a better estimate of the pressure and flow rate distribution, and therefore identifies production problems such as cross flow more accurately. The multilateral well model is used to study the effects of fluid properties on flow rate redistribution in the laterals for two phase flow wells, and on overall well performance. Copyright 2005, Society of Petroleum Engineers.
