Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
CFD Analysis of Eccentricity Effects on Horizontal Wells Cleaning Process
Submission Author:
Marcelo dos Santos Lídio , ES
Co-Authors:
Renato Siqueira
Presenter: Marcelo dos Santos Lídio
doi://10.26678/ABCM.ENCIT2016.CIT2016-0104
Abstract
On the drilling process, drill pipe rotation and the weight applied to the bit is what promotes the rock fragmentation. The drilling fluid injected into the column removes these cuttings and return to the surface through the annular space. For horizontal wells, the drill string is usually displaced, due to gravitational effects, generating an eccentric configuration that changes the flow pattern and creates a sedimentation bed, which affects the wellbore cleaning process. This study uses computational fluid dynamics (CFD) in order to evaluate the eccentricity effects on the cleaning process performance. The drilling fluid is a standard fluid, used by a big petroleum company, with non-Newtonian characteristics represented by the Herschel-Bulkley rheological model. The geometry consists of two cylinders. The outer cylinder is static and the inner cylinder rotates, with rotational speed varying from ω = 0 to ω = 400 rpm. The axial flow is characterized by the Reynolds number, which varies from 200 to 1000. Two diameters ratio were evaluated (k = 0.5 and k = 0.9). For all the configurations specified above, five eccentricity values were analysed, varying from ϵ = 0 (concentric case) to ϵ = 0.8. The study shows a reduction of the axial velocity in the narrow gap with an increase of eccentricity, which would difficult the cuttings transport and form a cuttings bed at the bottom of the annular. This negative effect is compensated by an increase of the tangential velocity in this sector, which improves the cleaning process efficiency. In the wider gap, the eccentricity increase led to an increase of the axial velocity and a plug flow in this region, which is good for the cuttings transport. The study also shows that the increase in eccentricity induces a viscosity decrease in the narrow gap, demanding less energy to remove the cuttings.
Keywords
CFD, Eccentric annuli, Non-Newtonian fluid, Horizontal Wells, Wellbore cleaning
