Water-based
fracturing fluids are widely used in hydraulic fracturing
to stimulate reservoirs. However, a novel fracturing fluid system
needs to be developed for use in complex and challenging environments
due to the high temperature and pressure reservoir conditions. In
this study, the polymeric nanofluid hydrolyzed polyacrylamide (HPAM)/sodium
dodecyl sulfate (SDS)/nanoparticles (NPs) was prepared with a polymer
acrylamide (AM)-sodium acrylate (SA)-octadecyl dimethyl allyl ammonium
chloride (C18DMAAC) and amino modified multiwall carbon
nanotubes (CNT-NH2) by hybrid nanotechnology. It was found
that this polymeric nanofluid improved the viscosity of the basic
polymer solution and still exhibited excellent stability at 90 °C,
and the surfactant played an important role in the dispersion of nanoparticles
in polymer solution. The rheological studies showed that the synergistic
effect of surfactants and nanoparticles improved the viscoelasticity
and temperature and shear resistance of the polymeric nanofluids,
which showed an increased modulus at 1.0 Pa, and the shear viscosity
remained above 70 mPa s at 90 °C. In addition, the addition of
nanoparticles altered the wettability of the reservoir rock, thus
changing the distribution and flow of fluid in the reservoir. The
drag reduction rate of this polymeric nanofluid was up to 60.7%, and
the fluid loss coefficient decreased to 1.46 × 10–5 m/min1/2. Therefore, the polymeric nanofluids composed
of surfactants, nanoparticles, and polymers hold potential applications
in the oilfields to improve the hydraulic performance of fracturing
operations.
A cobalt-catalyzed enantioconvergent radical Negishi C(sp 3 )−C(sp 2 ) cross-coupling of racemic benzyl chlorides with arylzinc reagents has been developed in good yield with moderate enantioselectivities. This strategy provides an expedient access toward a range of enantioenriched 1,1-diarylmethanes. Key to this discovery is the utilization of a chiral multidentate anionic N,N,Pligand to strongly coordinate with the cobalt catalyst and tune its chiral environment, thus achieving the enantiocontrol over the highly reactive prochiral alkyl radical species.
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