Nuclear magnetic resonance experiments on the time-varying law of oil viscosity and wettability in high-multiple waterflooding sandstone cores

A simulated oil viscosity prediction model is established according to the relationship between simulated oil viscosity and geometric mean value of T2spectrum,and the time-varying law of simulated oil viscosity in porous media is quantitatively characterized by nuclear magnetic resonance(NMR)experiments of high multiple waterflooding.A new NMR wettability index formula is derived based on NMR relaxation theory to quantitatively characterize the time-varying law of rock wettability during waterflooding combined with high-multiple waterflooding experiment in sandstone cores.The remaining oil viscosity in the core is positively correlated with the displacing water multiple.The remaining oil viscosity increases rapidly when the displacing water multiple is low,and increases slowly when the displacing water multiple is high.The variation of remaining oil viscosity is related to the reservoir heterogeneity.The stronger the reservoir homogeneity,the higher the content of heavy components in the remaining oil and the higher the viscosity.The reservoir wettability changes after water injection:the oil-wet reservoir changes into water-wet reservoir,while the water-wet reservoir becomes more hydrophilic;the degree of change enhances with the increase of displacing water multiple.There is a high correlation between the time-varying oil viscosity and the time-varying wettability,and the change of oil viscosity cannot be ignored.The NMR wettability index calculated by considering the change of oil viscosity is more consistent with the tested Amott(spontaneous imbibition)wettability index,which agrees more with the time-varying law of reservoir wettability.

Jet modification in absence of QGP-medium:the role of multiparton interactions and color reconnection

Recent studies on high-multiplicity events in small collision systems(proton-proton and proton-lead)have drawn considerable research interest toward the possibility of the formation of partonic medium in such systems.One of the important consequences of the formation of dense partonic medium is the quenching of high-momentum final-state particles,resulting in several experimental observations such as suppression in nuclear modification factor RAA,modification of jet shape observableρ(r)and jet fragmentation(z^(ch))distributions,etc.In this work,we studyρ(r)and z^(ch)for inclusive charged-particle jets in proton-proton(pp)collisions at√s=13 TeV using the PYTHIA 8 Monash 2013 Monte Carlo simulation.We show that the color reconnection(CR)and multiparton interaction(MPI)mechanisms in PYTHIA 8 can lead to an increased rate of jet production.We also find that the mechanisms of MPI and CR and change in the gluonic contribution in high-multiplicity events result in significant modification ofρ(r)and z^(ch)compared to those in minimum bias events for 10<p_(T,jet)^(ch)<20 GeV/c.We notice a direct connection of<N_(MPI)>and gluonic contribution with the amount of modification inρ(r):the larger the number of MPIs and/or gluonic contribution,the larger the amount of modification ofρ(r).