Sayyadul Arafin

Specific heat ratio, Grüneisen parameter and Debye temperature of crude oil

There has been substantial interest in determining the thermo-physical properties of hydrocarbon fluids. We have used three different experimental techniques: ultrasonic interferometry to determine the velocity of compressional wave, differential scanning calorimetry to determine the specific heat and the Anton Paar density meter to determine the density of crude oil sample over a wide range of temperatures varying from 20 to 70 °C. These data are used in thermodynamic relations to evaluate the specific heat ratio, the Gruneisen parameter, the Debye temperature and the long wavelength limit of the structure factor. The packing fraction obtained for crude oil is found to be closer to the values of other dense liquid fluids.

A correlation between surface, transport and thermo-elastic properties of liquid hydrocarbon: an experimental investigation

The temperature dependence of surface tension and viscosity has been investigated in two multi-component liquid hydrocarbons, namely, crude oil samples with different API numbers. The surface tension is found to decrease linearly with temperature whereas viscosity exhibits Arrhenius type variation. These measured values along with the ultrasound velocity, density and the isothermal compressibility have been used to estimate a number of physical parameters such as the activation energy, attenuation factor and the shear wave velocity. Crude oil with larger API was found to have smaller activation energy. Shear velocity decreases exponentially with increasing temperature while the attenuation factor is found to increase linearly with temperature. The ratio of the surface tension to viscosity varies linearly as the square root of temperature. The product of the surface tension and the isothermal compressibility, often characterized as a fundamental or correlation length of the surface of the liquid, was found to yield a constant value for both samples.

Equation of State of Crude Oil Samples

Technological advancement in exploration, refinement and enhanced recovery of hydrocarbon fluids heavily depend upon the thermo-physical properties of these fluids under different temperature and pressure conditions. A direct measurement at in-situ conditions is quite difficult; therefore we have utilized thermodynamic equations to extrapolate these thermo-physical properties at ambient conditions. The basic ingredients are density and ultrasound velocity which we have measured in the laboratory as a function of temperature for light and heavy crude oils procured from different wells of Oman. The densities of the samples were measured as a function of temperature using a precision density meter and the sound velocity using an ultrasound interferometer. To understand the variation of physical properties on mixing we have studied a 50:50 mixture of light and heavy oils. These data, in turn, were used to develop the equation of state. Our computed equation of state conforms reasonably well to the in-situ reservoir conditions.

Relative Bouguer anomaly

Corrections to gravity data and the meaning of the term Bouguer anomaly still confuse many of us despite detailed discussions by such gravity practitioners as LaFehr (1991, 1998), Chapin (1996), and Talwani (1998). In his 1991 article, LaFehr pointed out that incomplete treatment of the subject by major exploration geophysics textbooks is a main reason for the misunderstanding of gravity data reductions. While the mathematical expression for absolute Bouguer anomaly is explicit and available in correct form in some textbooks, that is not true in the case of the relative Bouguer anomaly. The formula for relative Bouguer anomaly seems in conflict with the definition of gravity anomaly. Thus, I present here a mathematical expression for relative Bouguer anomaly that is consistent with the definition of gravity anomaly. The gravity anomaly, Δ g , represents variation of the earths gravity value due only to lateral density change. It is defined at a point on the physical surface of the Earth as the deviation of the Earths normal or theoretical gravity value, gϕ , at the point of latitude ϕ from the observed gravity value, gobs , at the same point: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\ {\Delta}g\ =\ g\_{obs}\ {-}\ g\_{{\phi}}\] \end{document}(1) The theoretical gravity value can be calculated from any International Gravity Formula (IGF) developed after 1967. The IGF formula of 1987 is: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\ g_{{\phi}}\ =\ 978032.68\ (1\ {+}\ 0.00193185138639\ \mathrm{sin}^{2}\ {\phi}/(1\ {-}\ 0.00669437999013\ \mathrm{sin}^{2}\ {\phi})^{0.5}\] \end{document}(2) The symbol g represents the absolute gravity value. The theoretical gravity formula is derived by taking into consideration the ellipsoidal shape, rotation around the geographical axis, and the massive equatorial bulge …

Transport properties and model-based dynamical properties of Omani crude oils

We have measured the density and viscosity of five crude oil samples, collected from various hydrocarbon reservoirs in Oman, as functions of temperature. The measured quantities are expressed in terms of fitted formulae allowing their easy usage for different computational and simulation works. As an application, these thermo-physical data have been utilized to investigate the flow dynamics of hydrocarbon films under gravity at various temperatures. We have modeled the flow of these crude oils to study the dynamics of falling films in an open-top rectangular pipe set at various angular alignments under the assumption of Newtonian fluid describing a laminar flow. The adopted model of the investigation is not entirely novel, but the calculations aim to apply the model to various Omani crude oil samples with various American Petroleum Institute (API) values; the calculated results shed light on the dynamics of these crude oil films, which might be correlated to crude oil purification mechanism and open-top transportation.

Equation of state of crude oil through temperature dependent ultrasonic measurements

Ultrasound interferometery has been used to determine the velocity of propagation of compressional waves in two different samples of crude oil over a wide range of temperatures. The corresponding bulk density of the samples at similar conditions has also been measured using an Anton Paar density meter. These experimentally measured quantities form the basis for the thermo-physical characterization of crude oil through thermodynamic relations. This facilitated the evaluation of the acoustic impedance, compressibility and the coefficient of thermal expansion as a function of temperature. Simple analytical relations are suggested to describe the temperature dependence of thermo-physical functions. The equation of state for the crude oil has been set up by using these data. Our study yields a very close agreement to the reservoir conditions of the respective oil fields and to other empirical relations.

Three-dimensional gravity modelling of a Trinidad mud volcano, West Indies

The violent eruption of the Piparo mud volcano, Trinidad, in February 1997 demonstrated its destructive capability by completely burying 16 houses and a number of livestock under a 5 m thick mud pile. Unlike magmatic volcanoes, mud volcanoes involve very low energy, making geophysical methods such as seismology unsuitable for monitoring. Three-dimensional gravity modelling over the Tabaquite mud volcano suggests the presence of a large density contrast (?0.70 t.m-3). The density contrast being large and dynamic (i.e., it is absent at recently active mud volcanoes like Piparo) makes the gravity method a potential tool for monitoring mud volcanoes.The violent eruption of the Piparo mud volcano, Trinidad, in February 1997 demonstrated its destructive capability by completely burying 16 houses and a number of livestock under a 5 m thick mud pile. Unlike magmatic volcanoes, mud volcanoes involve very low energy, making geophysical methods such as seismology unsuitable for monitoring. Three-dimensional gravity modelling over the Tabaquite mud volcano suggests the presence of a large density contrast (−0.70 t.m-3). The density contrast being large and dynamic (i.e., it is absent at recently active mud volcanoes like Piparo) makes the gravity method a potential tool for monitoring mud volcanoes.

Thermo-elastic and thermodynamic properties of light and heavy crude oil

Three different experiments, viz., ultrasound interferometry, differential scanning calorimetry, and density measurements were carried out over a wide range of temperature varying from 20°C to 70°C in light, heavy, and a mixture of light and heavy crude oil samples which differ considerably in its American Petroleum Institute gravity. The properties of the mixture have been discussed in terms of its deviation from the ideal values of mixing. The directly measured quantities such as the compression wave velocity, the specific heat at constant pressure, and the density were used to evaluate the temperature dependence of adiabatic compressibility, coefficient of volume expansion and the acoustic impedance. A correlation between thermo-elastic and thermodynamic functions of crude oils has been investigated. In particular, the ratio of the specific heats has been determined by making use of the thermo-elastic functions, which was further used to estimate the specific heat at constant volume. The values of the isothermal compressibility and the coefficient of volume expansion are used to evaluate the pressure–temperature dependence of crude oil conforming to in-situ reservoir conditions.

Pressure variation of melting temperatures of alkali halides

The melting temperatures of alkali halides (LiCl, LiF, NaBr, NaCl, NaF, NaI, KBr, KCl, KF, KI, RbBr, RbCl, RbI and CsI) have been evaluated over a wide range of pressures. The solid–liquid transition of alkali halides is of considerable significance due to their huge industrial applications. Our formalism requires a priori knowledge of the bulk modulus and the Gruneisen parameter at ambient conditions to compute Tm at high pressures. The computed values are in very good agreement with the available experimental results. The formalism can satisfactorily be used to compute Tm at high pressures where the experimental data are scanty. Most of the melting curves (Tm versus P) exhibit nonlinear variation with increasing pressure having curvatures downward and exhibit a maximum in some cases like NaCl, RbBr, RbCl and RbI. The values of Tmmax and Pmax corresponding to the maxima of the curves are given.

Chemical short range order in MgPb alloys

Magnesium and its alloys are the ideal materials for the automotive and aerospace applications due to their light weight, excellent physical and mechanical properties. In recent years, great effort is being made to synthesise Mg-alloys which are superior in corrosion performance and endowed with required thermal and mechanical properties. Despite of the growing interest in such alloys, very little studies exist which analyse the microscopic level bonding and the atomic order which are ultimately responsible for their thermal stability and synthesisation. In the present work, we have used the compound formation model (2Mg + Pb↔Mg2Pb) to establish the interconnection between the microscopic interactions to the observed thermodynamic properties. It has been used to compute the concentration and the temperature dependence of the excess free energy, concentration fluctuations and chemical short range order which suggests that a reasonable degree of chemical order exist in the alloys.