The flow properties of Egyptian bentonite as a drilling mud were studied using anionic polyacrylamide as an additive (MW 1,000,000 g/mol). The rheological properties (plastic viscosity, yield point, thixotropy) of bentonitepolyacrylamide mud were investigated at different concentrations (5-20 mg/L). It was found that, as polyacrylamide concentration increases, rheological properties increase after 24-h aging time and up to 408C. By increasing temperature, rheological properties become nearly constant. Electrical properties (electrophoretic mobility and zeta potential) of Na bentonite/PAM mud were measured using zeta meter. The results showed that zeta potential of Egyptian bentonite/ PAM mud increased at low PAM concentrations up to 10 mg/L. At high polyacrylamide concentrations, these properties decreased. To investigate the relation between rheological and electrical properties, potential energy profiles were constructed. Potential energy profile at 10 mg/L polyacrylamide-clay showed a high repulsion potential energy between clay surfaces, i.e., suspension stability attained. The most reliable clay suspension to meet the desired properties could be reached using 6% clay suspension concentration, 10 mg/L polyacrylamide, and temperature 408C up to 24-h aging time.

The flow properties of Egyptian bentonite were studied using a combination of anionic polyacrylamide (MW ¼ 1,000,000 g mol À1) and cationic polyethylene imine (MW ¼ 700,000 g mol À1 ). This combination gave a significant effect on the clay suspensions to be qualified in the field of drilling mud depending on the sequence their addition. It was found that, by adding 50 mg/L cationic polyethylene imine followed by 10 mg/L anionic polyacrylamide, the rheological properties were improved using 6% Egyptian bentonite suspension, especially at 208C. But, by reversing this addition sequence, the rheological properties of bentonite suspension were declined. The zeta-potential value of bentonite suspension in the presence of 50 mg/L polyethylene imine was À47 mV, while at 10 mg/L polyacrylamide was À55 mV. But, on addition of 10 mg/L polyacrylamide to bentonite suspension followed by 50 mg/L polyethylene imine induced a reduction of the zeta-potential value to À51 mV when compared with that of polyacrylamide alone. By reversing the addition sequence, a very high stable suspension having zeta-potential values of À82 mV was obtained. Potential energy profiles were constructed to investigate the relation between rheological and electrical properties. Potential energy profile at 50 mg/L polyethylene imine followed by 10 mg/L polyacrylamide to bentonite suspension produced a high repulsion potential energy between clay surfaces, i.e. the suspension stability improved. By reversing that sequence, a significant decrease in the energy barrier was observed. The most reliable clay suspension as a drilling mud could be obtained by using 6% clay suspension concentration, with 50 mg/L polyethylene imine followed by 10 mg/L polyacrylamide, at 208C up to 24 h aging time.

ABSTRACT:The adsorption of polymer on clay particles has great importance in many industrial applications. This work aimed to study the adsorption of anionic polymer, poly (4-sodium styrene sulfonate), on kaolinite clay surfaces. Three different Egyptian kaolinite clay samples were used. The kaolinite clays were saturated with sodium or calcium cation. It was found that the Freundlich isotherm is applicable for this polymer adsorption on kaolinite. The parameters of the Freundlich equation are very close, indicating a comparable nature for the binding behavior between the different samples of kaolinite and the adsorbed polymer.The adsorption process was examined at different pH values (3, 6, and 9 Ϯ 0.1) to cover the range below and above the point of zero charge of kaolinite surfaces. It was found that, below this point, the polymer adsorption increased, while above it the polymer adsorption decreased. The polymer adsorption on calcium kaolinite was higher than that of sodium kaolinite at the same pH value.

The rheological properties of Egyptian bentonite suspensions in the presence of nonionic polymers were investigated. Two different types of nonionic polymers were studied: poly(ethylene glycol) (molecular weight 5 6000 g/mol) and poly(vinyl pyrrolidone) (molecular weight 5 40,000 g/mol). The rheological properties (plastic viscosity, apparent viscosity, and yield point) of concentrated clay suspensions (6-8% w/w) at different temperatures after 24 h were determined. As the nonionic polymer concentrations increased, the rheological properties of the bentonite suspensions showed a slight increase, especially at an 8% clay content. The electrical properties (electrophoretic mobility and f potential) of Egyptian bentonite in the presence of different nonionic polymers were measured with a f meter. The results showed that the f potential of this bentonite was higher with 200 mg/L poly (vinyl pyrrolidone) than with 1000 mg/L poly(ethylene glycol). Potential energy profiles for bentonite suspensions for these nonionic polymers were constructed to show that the net energy barrier for bentonite suspensions followed repulsion or attraction between particles. These profiles showed that the potential energy profile of a bentonite suspension with 200 mg/L poly(vinyl pyrrolidone) produced a high repulsion potential energy between clay surfaces; that is, the suspension stability improved.

The flow properties of bentonite were studied with a combination of anionic polystyrene sulfonate (molecular weight ¼ 70,000 g/mol) and nonionic poly(vinyl alcohol) (molecular weight ¼ 50,000 g/mol). This combination had a significant effect on clay suspensions depending on the sequence of the polymer addition. The addition of 50 mg/L anionic polystyrene sulfonate followed by 200 mg/L nonionic poly(vinyl alcohol) improved the rheological properties with a 7% bentonite suspension, especially at 208C and after 24 h of aging. However, by the reversal of this addition sequence, the rheological properties of bentonite suspensions were reduced. The z potential of bentonite suspensions of the individual polymers at the same concentration was À42 mV for polystyrene sulfonate and À63 mV for poly(vinyl alcohol). The combined effect of anionic polystyrene sulfonate followed by nonionic poly(vinyl alcohol) noticeably changed the z potential (À95 mV). With the reversal of the addition sequence, this parameter did not change. Potential energy profiles were constructed to investigate the suspension stability. Potential energy profiles of polystyrene sulfonate added to bentonite suspensions and followed by poly(vinyl alcohol) produced high repulsion potential energy between clay surfaces, reflecting high suspension stability. By the reversal of this sequence, a significant reduction of the energy barrier was observed. On the basis of the rheological and electrical properties of this system, the addition of polystyrene sulfonate followed by poly(vinyl alcohol) provides a promising tendency for a 7% clay concentration to meet desirable drilling mud properties.