The Effect of Biopolymer Chitosan on the Rheology and Stability of Na-Bentonite Drilling Mud

Abstract

The utilization of greens resources is a grand challenge for this century. A lot of efforts are paid to substitute toxic ingredients of the conventional drilling mud system with nontoxic natural materials. In this paper, the effect of the natural polymer chitosan on the rheology and stability of sodium-bentonite drilling mud was investigated in the polymer concentration range of 0.1–3.0 wt.%. Both the shear and time dependent rheological properties of pure chitosan, pure bentonite and bentonite–chitosan dispersions were studied. Moreover, zeta potential measurements were used to evaluate the stability of bentonite-chitosan suspension. Adding chitosan improved the natural properties of drilling mud, namely: yield stress, shear thinning, and thixotropy. The viscosity of bentonite suspension increased significantly upon the addition of chitosan in the concentration range of 0.5 to 3.0 wt.% forming network structure, which can be attributed to the interactions of hydrogen bonding between -OH clusters on the bentonite surface with the NH group in the chitosan structure. On the other hand, dispersed chitosan–bentonite suspension was observed at low chitosan concentration (less than 0.5 wt.%). Increasing both bentonite and chitosan concentrations led to the flocculation of the bentonite suspension, forming a continuous gel structure that was characterized by noteworthy yield stress. The desired drilling mud rheological behavior can be obtained with less bentonite by adding chitosan polymer and the undesirable effects of high solid clay concentration can be avoided.

Rheological and Viscoelastic Properties of Chitosan Solutions Prepared with Different Chitosan or Acetic Acid Concentrations

“…Indeed, the solution less diluted (0.5% of Ch) behaves as Newtonian fluids, meaning that interactions with biopolymer–water prevailed [ 28 ]. Similarly, Abu-Jdayil et al [ 14 ], working on the effect of Ch (0.1–3%), observed a non-Newtonian behavior overall, except for Ch ≤ 0.5%.…”

“…Benoso et al [ 12 ] prepared Ch solutions with different pH using Ac solutions and verified that their ξ-potential, which measures the net charge of the macromolecule in the solution, was always positive, decreasing linearly from 70 to 38 mV when the pH increased from 3.5 to 6.0 and confirming that the protonation was dependent on pH. Abu-Jdayil et al [ 14 ] observed that the ξ-potential for the Ch solution slightly decreased to almost zero mV by increasing the Ch, as a consequence of the Ch effect on the final pH of solutions prepared with constant Ac.…”

“…Similar pseudoplastic behavior was reported by El-Hefian et al [ 21 ], analyzing Ch solutions with different Ch (2–10 g/L) and T (20–50 °C); by Hwang and Shin [ 27 ], for Ch solutions with different Ch (1–2.5%) at 25 °C; by Torres et al [ 24 ], testing Ch solutions with 0.025, 0.03, and 0.035 g/mL at 30 °C; and by Abu-Jdayil et al [ 14 ], for Ch solutions with 0.1–3% of Ch, among others. This same behavior was also observed in works on blends of Ch and starch [ 16 ] or gelatin [ 12 ] solutions and in FFS based on Ch/gelatin blends [ 15 ].…”

“…These differences must be explained by the fact that a low viscosity Ch was used in this work. For Abu-Jdayil et al [ 14 ], the relation between K and Ch followed a power law model, with K increasing as a function of Ch. In addition, Tovar et al [ 22 ] observed that K and n values increased and decreased, respectively, with the increasing of Ch, at 20 °C, similar to that observed by Torres et al [ 24 ].…”

“…There are several works on rheological properties of FFS based on Ch, pure or blended with other biopolymers [ 12 , 14 , 18 , 19 ], but few papers on Ch solutions. El-Hefian et al [ 21 ] studied the effect of the temperature (20–50 °C) and Ch (2–10 g/L) on the viscosity of Ch solutions ( Table 1 ) and observed that these solutions behaved like pseudoplastic fluids and that viscosity decreased as a function of the temperature and increased as a function of Ch.…”