CFD SIMULATION OF SURGE AND SWAB PRESURES IN CONCENTRIC AND ECCENTRIC ANNULI USING POWER-LAW FLUID

In deepwater exploration, wellbore pressure stability must be maintained to avoid a catastrophic accident such as blowout. Accounting for the factors contributing to wellbore pressure is beneficial to ensuring the stability of the wellbore. In this study, a Computational Fluid Dynamic (CFD) is used to simulate the surge and swab pressure in concentric and eccentric annular geometry using Power-Law fluid. The study fully utilises the CFD software: ANSYS 15.0 and the Fluid Flow (CFX) model to analyse the major factors that affects surge/swab pressure. These include; tripping pipe velocity, wellbore geometry, fluid rheology, pipe eccentricity, flow regime and whether the pipe is closed or open. The model geometries were designed with ANSYS workbench and meshed with tetrahedron elements for concentric annulus and hexahedron elements for eccentric annulus. Grid independent study was performed to compute an optimum mesh size to reduce the computational time to run the simulations. The simulation results are compared with the experimental results both for concentric and eccentric annulus using four (4) different types of test fluids (1.00% PAC-A, 0.75% PAC-A, 1.00% PAC-B, and 0.75% PAC-B).