Thermodynamic Basis of Brine Density on Pressure, Temperature, and Chemical Composition in Ultrahigh Pressure/High Temperature Environments

Summary Temperature change and the pressure/volume/temperature (PVT) response of wellbore annular fluids are the primary variables that control annular pressure buildup in offshore wells. Though the physics of annular pressure buildup is well understood, there is some ambiguity in the PVT models of brines. While custom tests can be performed to determine the PVT response of brines, they are time-consuming and expensive. In this light, our paper presents a method to determine the density of brines from their chemical composition, as a function of pressure and temperature. It compares theoretical predictions with the results of tests on brines used in our industry and available test data from the oil and gas and other industries. In 1987, Kemp and Thomas used the principles of chemical thermodynamics to develop equations for the density of brines as a function of pressure and temperature and their electrolytic actions. However, their paper contained two (inadvertent, and probably typographical) errors. One of the errors lay in the set of the Debye-Hückel parameters, and the other was contained in the coefficients of the series expansion for the infinite dilution molal volume. Furthermore, they (inadvertently) did not mention the role of a crucial parameter that accounts for the interaction between the ionic constituents of the salt. As a result, nearly a generation of engineers in our industry has been unable to reproduce their valuable results or apply their technically rigorous results to other brine chemistries. In this paper, we return to the basic equations of chemical thermodynamics and the principles of stoichiometry and delineate the inadvertent errors that had crept into the Kemp and Thomas equations. We then present the rectified equations and reproduce their example with the corrected results. Further, we compare the predictions from the original Kemp and Thomas work with results from a leading chemical engineering model. Finally, we compare the results of theoretical models with test measurements from the laboratory and characterize the uncertainty inherent in each model. Thereby, we have rendered the Kemp and Thomas (1987) model useful to the well design community.

Studies on Apparent Molal Compressibility and Molal Volume of ZnSO4 in Aqueous Saccharides Mixed Solvent Systems: A Comparative Study

Different metal ions as well as carbohydrates play vital role in human metabolism. The present investigation emphasizes on zinc sulphate (ZnSO4) in galactose and its comparative study with lactose in aqueous medium at 303.15, 308.15, 313.15K temperature and at 1.0 atmospheric pressure. Different physical quantities such as density, viscosity and speed of sound have been measured as function of concentrations and temperatures for these multi-component solutions. These quantities were further used to evaluate various thermo-acoustic parameters like acoustic impedance, isentropic compressibility, partial molal compressibility, partial molal volume, internal pressure etc,. The results were analyzed to assess the type and extent of association among the components. Moreover, both Zn2+ and SO42- are in the Hofmeister series and there is a possibility of ion-macro molecule interactions in aqueous solution. The breaking of the structure and the solvation of the solute by changing the temperature in mixed solvents are the point of discussion in the present study. Interestingly, the ion-solvation of zinc ion is comparatively more favorable in galactose than in lactose-water mixed solvent systems. Resumen. Diferentes iones metálicos, así como carbohidratos juegan un papel vital en el metabolismo humano. La presente investigación centra su atención sobre el sulfato de zinc (ZnSO4) en galactosa y un estudio comparativo con lactosa en soluciones acuosas a las temperaturas 303.15, 308.15, 313.15K y 1 atm de presión. Se midieron diferentes cantidades físicas como densidad, viscosidad y velocidad del sonido como función de la concentración y la temperatura de las soluciones. Posteriormente, estas cantidades se utilizaron para evaluar distintos parámetros termoacústicos como impedancia acústica, compresibilidad isoentrópica, compresibilidad molal parcial, volumen molal parcial, presión interna, etc. Los resultados se analizaron para evaluar el tipo y grado de la asociación entre los componentes. Mas aún, tanto Zn2+ como SO42- están en las series de Hofmeister y hay una posibilidad de presencia de interacciones ión-macromolécula en la solución acuosa. Un punto de discusión en el presente estudio es el rompimiento de la estructura y la solvatación del soluto debidos al cambio de la temperatura de las soluciones. Es interesante hacer notar que la solvatación de los iones de zinc es comparativamente mas favorable en las soluciones acuosas de galactosa que de lactosa.

Composition dependent density of ternary aqueous solutions of ionic surfactants and salts

Surfactants exist in atmospheric aerosols mixed with inorganic salts and can significantly influence the formation of cloud droplets due to bulk–surface partitioning and surface tension depression. To model these processes, we need continuous parametrizations of the concentration dependent properties of aqueous surfactant–salt solutions for the full composition range from pure water to pure surfactant or salt. We have developed density functions based on the pseudo-separation method and Young’s mixing rule for apparent partial molal volumes for solutions that mimic atmospheric droplets of marine environments. The developed framework requires only model parameters from binary water–salt and water–surfactant systems and includes the effect of salinity on micellization with composition-dependent functions for the critical micelle concentration (CMC). We evaluate different models and data available in the literature to find the most suitable representations of the apparent partial molal volume of sodium chloride (NaCl) in aqueous solutions and the CMC of selected atmospheric and model surfactants in pure water and aqueous NaCl solutions. We compare model results to experimental density data, available in the literature and obtained from additional measurements, for aqueous solutions containing one of the ionic surfactants sodium octanoate, sodium decanoate, sodium dodecanoate or sodium dodecylsulfate mixed with NaCl in different relative ratios. Our model follows the experimental trends of increasing densities with increasing surfactant concentrations or increasing surfactant–salt mixing ratios both, below and above the CMC, capturing the effect of the inorganic salt on the surfactant micellization.

Volumetric Properties of Secondary Butanol and Tertiary Butanol in Water and Aqueous Micellar Systems of Sodium Dodecyl Sulphate

The apparent molal volumes of sec-butanol and t-butanol in water and in aqueous micellar system of sodium dodecyl sulphate have been determined from density measurements at different surfactant concentrations and temperatures. The partial molal volumes of the alcohols in aqueous micellar system at infinite dilution, V20 (mean, mic) were obtained from apparent molal volume data and compared with the corresponding values in aqueous solvent, V20 (mean, aq). The standard partial molal expansibilities, E20 (mean) of the alcohols were evaluated from V20 (mean) data at various temperatures. The transfer apparent molal volumes, ∆φtr0 for the alcohols from water to surfactant-water system are determined from apparent molal volume data. The sign and magnitude of these parameters are used to analyze the location of the solubilizate (alcohols) in the micellar system and the nature of interactions between alcohols and the micellar aggregates.

SOLUTE-SOLUTE AND SOLUTE-SOLVENT INTERACTIONS STUDIES OF SACCHARIDES IN AQUEOUS SODIUM BUTYRATE SOLUTION AT 308K TEMPERATURES

Density and viscosity of D (+) galactose and D (+) lactose mono hydrates in aqueous solution of sodium butyrate solutions have been determined experimentally at 308 K. The results obtained from density and viscosity measurement have been used to calculate the, apparent molal volume фv, partial molal volume ф0v, transfer volume ∆ф0tr at infinite dilution, A and B coefficient and Sv experimental slope. The results are interpreted in terms of solute-co- solute and solute-solvent interactions in these systems. It has been observed that there exist strong solute-solvent and solute-solute interactions and complex formation between in these ternary systems. The properties of the D (+) galactose and D (+) lactose mono hydrates in aqueous solution of sodium butyrate solutions are discussed in terms of the structure making and hydrogen bonding effect.

MOLECULAR INTERACTION STUDIES OF ZWITTER- ION IN AQUEOUS SUCROSE AND ASCORBIC ACID AT CONSTANT TEMPERATURE

Density and viscosity of L-Arginine in aqueous sucrose and ascorbic acid solutions have been determined experimentally at 298 K. The results obtained from density and viscosity measurement have been used to calculate the Hydration number Hn, apparent molar volume фv, partial molal volume ф0v , at infinite dilution, transfer volume ∆ф0tr and B- coefficient. It has been observed that there exist strong solute-solvent interaction and complex formation between in these ternary systems. The properties of this amino acid in water and aqueous sucrose and ascorbic acid systems are discussed in terms of the charge, size and hydrogen bonding effect.

INTERACTION STUDIES OF AMINO ACIDS IN AQUEOUS SODIUM BROMIDE SOLUTIONS AT DIFFERENT TEMPERATURE

Densities, ultrasonic velocities and viscosities of L- Valine and L- Phenylalanine in aqueous sodium bromide (0.00, 0.025 and 0.05) m solutions have been determined experimentally at 308 and 313 K. The results obtained from density ultrasonic velocity and viscosity measurement have been used to calculate the apparent molal volume, фv, apparent molal, adiabatic compressibility ф Ks, partial molal volume ф0v at infinite dilution, partial molal adiabatic compressibility ф0Ks at infinite dilution, transfer volume ∆ф(tr), experimental slopes Sv and SKs,Falkenhagen coefficient A and Jones-Dole B coefficient. The results are discussed in terms of the dehydration effect of the sodium bromide upon the amino acids and weak solute- solute and strong solute- solvent interactions. The properties of these amino acids in water and water + sodium bromide solution systems are discussed in terms of the charge, size and hydrogen bonding effect.