Fibers are extensively
used as a fluid additive in the oil and
gas industry to improve hole-cleaning performance, control fluid filtration
loss, and enhance hydraulic fracturing effectiveness. Generally, a
small amount of fiber is dispersed in the base fluid to achieve the
desired results without increasing the viscosity of the base fluid.
Nevertheless, sustaining a uniform fiber dispersion can be challenging
under wellbore conditions, which is essential for fibers’ functionality.
Consequently, a better understanding of fiber suspension or stability
in base fluids is necessary for their efficient utilization in drilling
and completion operations. In this study, response surface methodology
(RSM) and box–behnken design (BBD) are used to investigate
the stability of fiber in polymeric base suspensions, including carboxy
methyl cellulose (CMC), polyacrylamide (PAM), and xanthan gum (XG).
The BBD of three factors was selected to observe the influence of
polymer concentration, fiber concentration, and temperature on fibrous
suspension stability, with three levels of design factors (low, mid,
and high) and two fiber aspect ratios (3 and 12 mm fibers). The base
fluid polymer concentration ranged from 1 to 8 vol %, fiber concentration
ranged from 0.01 to 0.08 wt %, and the temperature was varied from
25 to 80 °C. The stability measurements were analyzed using Minitab,
subsequently, evaluating the factors’ impact and interactions
and determining the optimum conditions for the stability of the fibrous
suspensions. The results predicted by the developed model were in
good agreement with the experimental results R
2 ≥ 0.91–0.99. The sensitivity analysis showed
that base fluid polymer concentration is the most significant factor
affecting fibrous suspension stability. At high polymer concentrations,
fiber concentration and temperature effects are minimal, while the
temperature effect on the stability was observed at low concentrations
(e.g., low suspension viscosities). The fiber aspect ratio indirectly
affects system stability. Long fibers have a better tendency to entangle
and form a structured network, which in turn hinders the buoyancy
that induces individual fiber migration. On the contrary, short fibers
do not form a network, allowing them to easily migrate to the surface
and agglomerate at the top layer (unstable region). Optimization results
revealed that suspensions with viscosities above 50 mPa·s are
sufficient to maintain the stability of the suspensions at ambient
(25 °C) and elevated (80 °C) temperatures.