Simulated Pressure Drop When Circulating Fluids Past Liner Hanger Equipment In An Annular Configuration: Computational Fluid Dynamics (CFD) Studies And Experimental Validation

Abstract

Abstract Simulation tools have been developed to predict the equivalent circulating density (ECD) induced in the wellbore annulus during cementing operations. However, little has been done to predict the velocity and pressure fields around complex geometries, such as liner hangers. This paper demonstrates the use of Computational Fluid Dynamics (CFD) to better identify opportunities for modifying the geometrical design of downhole tools to reduce pressure drop and improving the estimations of the annular pressure drop across this equipment. In order to estimate pressure drop across complex annular sections, engineers typically use an equivalent geometry of concentric pipes for the length of interest. CFD is an iterative numeric method that calculates the flow and pressure fields for a fluid confined within a region of interest. This region, identified normally as a volume, is further divided in smaller elements where the continuity and conservation equations are solved and it is limited by boundary conditions which are mathematical restrictions that impose a final physical solution. The CFD results were validated experimentally at scale. The equivalent geometry of concentric pipes approach can under estimate the pressure drop and resulting ECD because it assumes a fully developed laminar flow regime and overlooks the energy dissipation induced by changing the fluid flow patterns, expansions and contractions. When placing cement slurries in a well annulus, there is often a very “narrow window” of operation due to the ECD that is induced during cementing operations approaching the fracture pressure gradient in the annulus. In this work, CFD was used to evaluate the pressure drop across a liner hanger system for several typical operation flow rates: 1bbl/min up to 5bbl/min. The overall pressure drop across the liner hanger section ranged from ~80 psi to ~550 psi, respectively. Simple geometric changes were then tested using CFD resulting in up to 40% pressure drop decrease across the tool, for those flow rates. The existing simulation tools' ability to accurately estimate the equivalent circulating density (ECD) is challenged when complex geometries such as liner hangers are used. CFD proved to be a powerful tool to gain insight into flow fields and pressure maps developed on complex annular geometry systems.