A novel autonomous inflow control device design and its performance prediction

In long horizontal wells, premature water or gas breakthrough is usually encountered due to the imbalanced production profile. This imbalanced phenomenon could be caused by the heel-toe effect, reservoir anisotropy, reservoir heterogeneity or natural fractures. Once coning occurs, water/gas fast track will be generated, leading to the reduction in oil production. Inflow control devices (ICDs) are usually installed in the completion sections to maintain a uniform inflow by generating an additional pressure loss. However, none of current ICDs are perfect enough to meet all the ideal requirements throughout the well's life. In this paper, a novel autonomous inflow control device (AICD) design is proposed based on the combination of two fluid dynamic components, with the splitter directing the flow, and the restrictor restricting the flow. Based on the combination of the flow pattern transformation criterion, homogenous model, two-fluid model, and pipe serial-parallel theory, a unified model of oil-water two-phase flow is developed to predict both the flow distributions and pressure drops through the splitter, which is then compared with the computational fluid dynamics (CFD) results. Also the rules of oil-water two-phase flow through the disk-shaped restrictor are studied by numerical simulation. The results show that the unified model compares well with the CFD results. The average error percentage between the model and CFD results for flow distribution is 10.02%, while that for pressure drop is 11.25%. Both the model and CFD results show that the flow distributions in different paths of the splitter will be adjusted automatically according to the fluid's specific property, thus different fluids will enter the restrictor differently, and result in varying flow resistances. Specifically, oil, being more viscous, tends to take the restrictive path, enter the restrictor radially, and result in minimal flow restriction; while water, being less viscous, tends to take the frictional path, enter the restrictor tangentially, begin spinning rapidly near the exit, and result in obvious flow restriction. This autonomous function enables the well to continue producing oil for a longer time while limiting the water production: hence the total oil production is maximized. The investigation conducted in this study also further enriches the theory of hydrodynamic calculation for oil-water two-phase flow in complex pipelines. (C) 2014 Elsevier B.V. All rights reserved.