Determining Gravelpack Fluidization Flow Velocity
In a gravelpack completion, non-uniform reservoir inflow with very high velocity can fluidize the gravel and/or erode the sand screen. Previous works have addressed the risks of fluidizing the gravelpack in high flow rate deepwater wells and have quantified a critical velocity above which fluidization is at risk. However, no formal mathematical model has justified the value, and details of the failure mechanism are lacking.
The gravelpack screen is equipped with a basepipe with a pattern of holes through which fluid must pass after flowing through the gravelpack and screen. In a cased hole completion fluid reaches the pack through a pattern of perforation tunnels opening into the pack. The result is a complex flow pattern inside the pack involving both vertical and annular flow in addition to the expected radial flow. Alternatively, during high rate flow, alignment of a single perforation with a hole in the basepipe could produce a jet effect.
The aim of this thesis is to create a simulator that models gravelpack dynamics including fluidization and to determine the minimum fluidization velocity in a gravelpack completion with given casing, screen, and basepipe geometries. The ANSYS-FLUENT simulator enables modeling of flow through the gravelpack governed by the particle motion phenomena according to the Euler-Euler approach that treats each of two phases (inflowing hydrocarbon and the gravel) as a continuum.
Results of this study will be useful in designing gravelpack completions in ultra-high rate wells.