Three crude oils were employed for precipitation of asphaltenes using two solvents, n-pentane and n-heptane. Crude oils were analyzed by API gravity, elemental composition and metals content. Asphaltenes were characterized by VPO molecular weight, liquid State 1H and 13C NMR, elemental composition, and metals content. Spectra were divided in three and two different regions for 1H and 13C NMR, respectively, to determine the most important structural parameters of asphaltenes. To avoid errors when determining asphaltene content and characterization, a solvent-to-oil (S/O) ratio of 60:1 was used. This optimal ratio was defined after conducting various experiments with different values of S/O in the range of 5:1 to 100:1. It was found that solvent type has a very important influence in composition of asphaltenes, which were also very different for the three crude oils studied. Aromaticity of asphaltenes was higher when n-heptane was employed.

No abstract

Villermaux & Pomeau (J. Fluid Mech., vol. 642, 2010, p. 147) analysed the motion of the interface of an inviscid liquid column released from rest in a vertical tube whose area expands gradually downwards, with application to an inverted conical container for which experimental measurements were carried out. An error in the analysis is found and corrected in the present investigation, which provides the new governing equation for the super-accelerated interface motion down gradually varying tubes in general, and integrated results for interface trajectories, velocities and accelerations down a conical tube in particular. Interestingly, the error does not affect any of the conclusions given in the 2010 paper. Further new results are reported here such as the equation governing the centre of mass and proof that the end point acceleration is exactly that of gravity.

We carry out experiments in which we have already measured, in a short period of time, the physical parameters that appear during the steam injection in a homogenous porous media (Woods and Fitzgerald 1993). For this work, we measured the distribution of displacement and temperature that occurred when steam is injected at different pressures (0.25-1 kg/cm 2 ) in a homogeneous porous media by the control of the injection pressure and flow rate.