A Rigorous Composite-Inflow-Performance Relationship Model for Multilateral Wells

Abstract

Summary Use of multilateral wells for oil and gas production has gained strong momentum in the past 5 years. However, most of the multilateral wells do not deliver hydrocarbon fluids at expected production rates. One of the reasons for this is that the well planners overestimate the productivity of wells by using inaccurate methods for predicting composite-inflow-performance relationship (IPR) of well laterals. A more-accurate method for predicting composite IPR of multilateral wells is highly desirable. This paper fills the gap. Starting from terms familiar to petroleum engineers, a general well model was developed with consideration of reservoir-wellbore crossflow for lateral IPR and coupling of fluid flow from individual laterals to the main wellbore. The model allows different IPRs of laterals and permits crossflow between laterals. Pressure losses in the vertical-, curvic- and horizontal-hole sections are rigorously considered. Oil and gas wells are treated differently. The modified Hagedorn-Brown correlation is used for modeling the flow in the vertical sections, and the Beggs and Brill correlation is used for the curvic and horizontal sections for oil wells. The Cullender and Smith method was used for modeling the flow in gas wells. A computer simulator was developed based on the model for predicting multilateral-well production rate. Case studies have indicated excellent accuracy of the computer model. This work provides petroleum engineers a reliable and user-friendly tool for designing and evaluating multilateral wells.