A Method for Minimizing Annulus Pressure Loss by means of Hole Cleaning and Hydraulics Coupling

Drill cuttings accumulate in the wellbore during drilling and form a cutting bed, which results in the increase of annulus pressure loss. To solve problem of large annular pressure loss from insufficient hole cleaning, a methodology in this study was developed to model the relationships between hole cleaning and annular pressure loss by coupling cuttings transport and annular pressure loss based on mass and momentum conservation. By using the developed model, the influence of parameters such as displacement, wellbore inclination, annulus size, rate of penetration (ROP) and rheological parameters of drilling fluid on annular pressure loss and degree of hole cleanliness were analyzed. The results show that annular pressure loss in extended-reach wells and horizontal wells does not increase with the increase of displacement due to cuttings in the well, but a critical value exists. When the displacement is below the critical value, the annular pressure loss decreases with the increase of displacement. However, pressure loss will increases with the increase of displacement when the displacement exceeds the critical value. Based on this result, a new calculation method is proposed to minimize annulus pressure loss by hole cleaning and annulus hydraulic coupling, which can be used in drilling parameters, control annulus pressure loss optimization and to guide drilling design and operation.