Performance of fiber-containing synthetic-based sweep fluids

Cuttings transport from the bit to the surface in horizontal or highly inclined wells is a critical component of overall drilling performance. The associated increase in bottomhole pressure and equivalent circulating density due to increased cuttings concentration and formation of cuttings bed in the wellbore can exceed the limits of the marginal operating pressure window that often exists in deepwater drilling. Fiber-containing sweeps, or fiber sweeps, have been shown to be effective in cleaning highly inclined wells by eliminating cuttings beds, thereby reducing the friction pressure loss. Incorporating fiber in a drilling sweep enhances its hole-cleaning performance and minimizes friction loss contributions from cuttings beds without significantly impacting flow properties of the fluid. This article presents the results of an experimental study conducted on the wellbore cleaning efficiency of fiber sweeps. Wellbore cleaning experiments were conducted with sweeps of synthetic-based drilling fluid (SBM) of density 1.27 g/mL treated with a monofilament synthetic fiber of density 0.9 g/mL, length 10 mm and diameter 100 pm. Fiber concentration was varied up to 0.06% w/w (0.54 g of fiber/L of fluid). The flow loop contained an annular test section and was fitted with a pipe viscometer. Cuttings bed heights in the flow loop annulus were measured at flow rates up to 300 L/min and pipe rotation speeds up to 50 rpm with the annulus configured horizontally (90 degrees) and inclined at 72 degrees. The results indicated that in the inclined configuration, addition of fiber to hole-cleaning sweeps substantially improves cuttings removal, but only when the pipe is rotated. When the annulus is horizontal or the pipe is not rotated, addition of fiber has only a small effect on cuttings bed removal. (C) 2014 Elsevier B.V. All rights reserved.