Cuttings Transport with Foam in Horizontal & Highly-Inclined Wellbores

Abstract

fax 01-972-952-9435. AbstractFoams are of considerable interest for annular pressure management in many drilling applications. While foam rheology and hydraulics have been studied in the past, knowledge of cuttings transport with foam is very limited for vertical wells, and even less well understood for horizontal and inclined-well configurations. In this paper, cuttings transport with foam in horizontal and highly-inclined wells is analyzed.Using the principles of mass and linear momentum conservation, a model consisting of three layers (motionless bed -observed in most experiments, moving foam-cuttings mixture and foam free of cuttings) is presented. The model includes seven independent equations and seven unknowns. A computer simulator was developed to solve simultaneously the system of equations for flow velocities, cuttings bed height, slip velocity, the in-situ concentration of flowing cuttings and pressure drop.An extensive experimental program on cuttings transport was conducted using The University of Tulsa Drilling Research Projects' full-scale (8" by 4 ½") flow loop at 70° to 90° inclinations (from vertical). A broad range of annular velocities and cuttings injection rates was investigated using foam qualities of 70% to 90%. Results from the experiments are presented in the form of graphs showing the cuttings bed cross-sectional area and pressure losses vs. foam flow rate. In all experiments, the foam behaved as a pseudo-plastic fluid; foam qualities of 80% and 90% exhibited noticeable wall slip. At a given flow rate and rate of penetration, bed thickness increases with an increase in foam quality. There is little effect of inclination angles in the range of 70°-90°.The experimental data were used to verify results from the simulator. The simulator is capable of estimating bed thickness and pressure drop with an error of less than 20% in most cases.

Sensitivity Analysis of Major Drilling Parameters on Cuttings Transport during Drilling Highly-inclined Wells

“…The model results are verified with the data of cuttings transport experiments conducted at TUDRP-LPAT flow loop ( Figure 2) using different fluids, i.e., Newtonian and non-Newtonian fluids, for various flow rates and ROP's (Tomren, 1979;Larsen, 1990;Sapru, 2001;Ozbayoglu, 2002). The comparison of the experimental data and the model results for estimating the bed thickness in the wellbore is presented in Figure 3.…”

“…Most of these studies agreed on the major effective drilling parameter on cuttings transport in high-angle wells as the annular fluid velocity, which is one of the major functions of shear stress. Moreover, when the flow regime is turbulent in the annulus, a significant reduction is observed in cuttings bed development (Leising and Walton, 2002;Ozbayoglu, 2002). Therefore, better cuttings transport ability has been reported for lowviscosity fluids when compared with high-viscosity fluids, because turbulent flow can be more easily obtained if the fluid viscosity is low.…”

Using foam in horizontal well drilling: A cuttings transport modeling approach

“…(4) reduces to the flow through an annulus which is approximated as a narrow slot (Ozbayoglu, 2002). Generalized rheological parameters can be defined in terms of a and b, and rheological parameters of any rheological model.…”

“…If flow equations for circular pipe and concentric annuli are derived and compared, one can define the shear rate at the wall in a general form (Ozbayoglu, 2002) as…”

Prediction of Critical Foam Velocity for Effective Cuttings Transport with Foam in Horizontal Wells

“…Good cuttings transport ability of foam has been demonstrated in the field (Rojas et al, 2002), although formation of stationary cuttings beds has been reported by some experimental studies (Ozbayoglu et al, 2003;Martins et al, 2001).…”