High energy dissipation-based process to improve the rheological properties of bentonite drilling muds by reducing the particle size.

Drilling mud is a multi-phase fluid that is used in the petroleum drilling process. Bentonite is the most important constituent of drilling mud; it endows the drilling mud with its rheological behaviors, such as viscosity, yield stress, and shear thinning. The process of manufacturing microscale bentonite at the nanoscale level is very promising for commercializing nano-based drilling mud. In contrast to the conventional method using the impeller, bentonite was manufactured in its nanoparticle state in the present work through ultrasonic and homogenizer processes in the solution state. In case of the ultrasonic process, the viscosity increase in the low shear rate region before and after processing of the 5 wt% bentonite-based mud and the rheological properties in the presence of polymer additive were compared. In case of the homogenizer process, the rheological properties of 3 wt% bentonite-based mud employed through the homogenizer process and 5 wt% mud prepared generally were compared. Both processes reported improvement of rheological properties, in which shear thinning behavior strongly occurred when particle size decreased through FE-SEM, TEM image analysis, and particle size analyzer. A regularized Herschel-Bulkley model suitable for rheological quantitative explanation of drilling mud including yield stress was selected. The homogenizer process has the potential to be applied in the petroleum drilling industry for large-scale production, and the mechanism was confirmed by numerical analyses. In conclusion, we presented a simple and easy-to-apply process to rapidly produce nano-based drilling mud.

Influence of MoS2 Nanosheet Size on Performance of Drilling Mud.

Water-based drilling mud (WBM) is a non-Newtonian fluid that has a variety of applications such as in transporting cuttings during drilling, protecting the borehole, and cooling the drill bit. With the development of nano-technology, various nanoparticles have been synthesized and have been added to WBM to improve its performance. Shear thinning is the most important factor in drilling mud and this attribute can be improved when two-dimensional particles are added. MoS2 nanoparticles, which represent a typical two-dimensional material, are easy to synthesize in large quantities and have a high thermal conductivity and low coefficient of friction. Since the two-dimensional structure, thermal conductivity, and low coefficient of friction of MoS2 would improve the performance of WBM, we experimented with MoS2 nanosheets as an additive, under optimal conditions, using various samples each with uniform sizes and thicknesses of nanosheets. A large amount of MoS2 nanosheets was synthesized, sorted by thickness and diameter, and added to drilling mud. The diameter of MoS2 was divided into a small diameter group (about 100⁻400 nm) and a big diameter group (about 300⁻650 nm), and the thickness was divided into 1⁻2 nm and 5⁻10 nm groups. Experimental results showed that when MoS2 is added to WBM, shear thinning occurs more strongly. In addition, the addition of MoS2 with a thickness of 1⁻2 nm and a diameter of 300⁻650 nm resulted in the highest increase in viscosity and thermal conductivity of WBM. As a result, we experimentally confirmed that MoS2 can be used as an additive to increase the thermal conductivity and viscosity of WBM and to make shear thinning phenomenon more.

Silver nanoparticles enhanced luminescence of terbium complex in solution for L-dopa determination.

Luminescent properties of a terbium (Tb3+)-L-3, 4-dihydroxyphenylalanine (L-dopa) complex by binding to colloidal silver nanoparticles (Ag NPs) have been presented. Luminescence intensity of the L-dopa complex was dramatically enhanced about 6-7 times by introducing Ag NPs. The Ag NPs concentration on the luminescent intensity was regarded as a main factor that balancing between an enhancing and a quenching effect of the Ag NPs. It was observed that changing the concentration of L-dopa causes the change in luminescence intensity. Under the optimized condition, the luminescence intensity of the system was linearly related to the concentration of L-dopa. Based on this observation, L-dopa-Tb3+ complex containing Ag NPs has been applied for the determination of L-dopa in pharmaceutical formulation. Linear responses of luminescence intensity were observed in the concentration range of 0.25 to 1.5 nM (r = 0.9934) of L-dopa with limit of detection 0.042 nM. The performance of the system was tested using 1.0 x 10(-9) M of L-dopa, yielding a precision of 1.21% RSD for nine replicate measurements. The present method has been successfully applied to determine L-dopa in pharmaceutical samples.