Numerical modelling of reverse circulation cementing with density unstable displacements in eccentric annulus

Abstract

This dissertation investigates the mechanics involved in reverse circulation cementing (RCC) with numerical modelling. Numerical simulations are done by utilising a computational fluid dynamics (CFD) software (OpenFOAM). Incompressible, immiscible multiphase solver (interIsoFoam) and LES turbulence model is used investigate the effects of buoyancy unstable displacement flows in eccentric and inclined annulus. Two annular meshes of varying degree of eccentricity (e=0.2 & e=0.7) is generated from geometry of a retrieved 9 5/8¨ and 13 3/8¨ cemented casing section which underwent RCC (Skadsem et al., 2020). Conditions during primary cementing operation is attempted recreated with smaller density differences of 5-10% between the slurry and spacer fluids. Both mesh cases show that interfacial mechanisms are highly sensitive to flow rates and observed displacement efficiency for higher eccentricity has substantial adverse effects on performance. Low Reynolds number regimes with Re=38 and Fr=0.379 result in substantial backflow of spacer fluid and largely stratified flows for highly inclined cases. Annular inclination is investigated at θ=15° & θ=45°. Flow rates and its effects on displacement efficiency is considerably affected by inclination where θ=15° cases indicate convergent displacement efficiency characteristics at Re > 1352. Higher inclination cases (θ=45°) show that optimal displacement efficiency lie in a much lower bulk velocity Re ≈ 190