Drill pipe eccentricity effects on horizontal wells cleaning process
Marcelo dos Santos Lídio1; Renato do Nascimento Siqueira1
1 Instituto Federal do Espírito Santo
doi:10.20906/CPS/COB-2015-1271
Resumo
The horizontal drilling process is attractive due to the increase of the contact area of the wellbore with the reservoir, causing an improvement on the production and process efficiency. The horizontal drilling process is characterized by fluid flow through an annulus and, due to gravitational effects, the drillstring is usually displaced, generating an eccentric configuration which changes the flow pattern and affects the wellbore cleaning process. This study uses computational fluid dynamics (CFD) in order to evaluate the eccentricity effects on the performance of the cleaning process. The geometry consists of two cylinders, and the inner cylinder rotates with a constant speed. The bulk axial velocity was also kept constant. The drilling fluid used was an aqueous solution of 0.1% xanthan-gum/0.1% carboxymethylcellulose and the non-Newtonian characteristics of the fluid was represented by the rheological Cross model. Five eccentricity values were evaluated. The study shows that the increase in eccentricity causes a decrease of 93% in the maximum axial velocity in the narrowest gap, which would induce negative effects on the cuttings suspension process. However, this effect is compensated by the tangential velocity, which increased in this sector, improving the wellbore cleaning process efficiency. The study also shows that the increase in eccentricity lead to a decrease of 32% in the pressure drop for the case of ε = 0.8, for small eccentricities (ε ≤ 0.4) the pressure drop reduction was small compared to the concentric case. Finally, an increase of eccentricity also reduces the viscosity at the narrowest gap, what could be prejudicial to the cleaning process.
Palavras-chave: CFD; Eccentric annuli; Non-Newtonian fluid; Horizontal well; Wellbore cleaning