Browsing by Autor "Armando Monsalve"

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Cálculo de propiedades termodinámicas de mezclas vapor/salmuera
(1986) Héctor M. Núñez; Armando Monsalve
Calculation of thermodynamic properties of steam/brine mixtures A software package in both languages, FORTRAN and BASIC, has been created to calculate specific volume, enthalpy, entropy, heat capacity, internal energy, and Gibbs free energy of steam and brine, (separately or as a mixture). The required equations have been developed by application of fundamental thermodynamic relationships and empirical correlations for the vapor Gibbs free energy and the brine specific volume and heat capacity. The thermodynamic properties can be calculated in the range of 32 to 1200°F and pressures up to 3200 psia for the vapor, with deviations below 0.5% respect to values reported in the steam tables. For the liquid the error is less than 0.9% in the range of 32 to 500°F and up to 5000 psig in the absence of electrolyte. For brine solutions up to 25% W NaCl, the deviation from reported values is less than 1.7% in the range of temperatures going from 50 to 350°F.
The Effect of Trace Quantities of Surfactant on Nitrogen/Water Relative Permeabilities
(1986) J. M. Sánchez; R. S. Schlechter; Armando Monsalve
ABSTRACT This paper proposes a single capillary model incorporating the mechanisms of foam generation, propagation, and rupture. It includes new features not heretofore noted and results in predictions for the influence of variables such as the gas rate, pore geometry, liquid rate, and surfactant concentration on the relative permeability to gas. Since the model is a simple one, only qualitative trends are predicted. Nevertheless apparently contradictory results can be understood in terms of the qualitative trends and new phenomena associated with the behavior of foams generated in situ are predicted. The model is a steady-state one. The generation rate of lamellae which are subsequently displaced and move along the capillary tube is a constant. To conduct experiments which are intended to confirm the model predictions one must ensure that these experiments yield truly steady-state results. This is not simple and a protocol for achieving steady state is tested. It is recommended as one approach for performing meaningful steady-state experiments. Systematic steady-state experiments are reported to demonstrate two important model predictions. The first shows the remarkable effect of even very small surfactant concentrations on the relative permeability to gas and the second set of experiments is designed to verify the model prediction that the relative permeability to gas at a fixed liquid saturation may increase or decrease with increasing liquid rates. Both trends have been reported in the literature.1,2 The correspondence between the predicted trends and those observed confirms the value of the single capillary model in understanding the complexities of mobility control using foams which are generated in situ.