Density measurement crude oils

The density or relative density of crude oils is used for the conversion of measured volumes to volumes at the standard temperatures of 1S C or 60 F and for the conversion of crude mass measurements into volume units. 

In the present paper, interfacial tensions were measured for a number of heavy crude oils at temperatures up to 200°C using the spinning drop technique. However, reliable data cannot be obtained by this or any other drop shape method because of the small density difference between heavy crudes and water which, moreover, tends to decrease as the temperature increases. This problem was overcome by using aqueous D20 instead of H20 as has been previously described [5,8,211. The influence of surfactant type and concentration, mono- and divalent cation concentrations, and pH on the attainment of low interfacial tensions are reported and discussed. 

Densities were measured using a Paar DMA 60 meter equipped with DMA 512 and DMA 601 HP external cells. Values in the 50-150°C range were interpolated from measured data (3-5 points) values above 150°C were extrapolated and are less accurate. Interfacial tension measurements at the minimum density difference encountered (0.05 g/cm3) could be in error by as much as 10%, which is within the repeatability of measurements with heavy crude oil samples (see below). 

Methodology Various fraction of crude oil was distilled under different condition after being sonicated by an ultrasonic processor for different intervals of time. Density of these fractions was determined by dialatometer. Viscosities of these fractions were measured using Ubbelohde viscometer and the results given as under ... 

Figures 9 and 10 show phase-behavior diagrams for David Lloydminster crude oil and the surfactant Neodol 25-3S in the presence of 1 wt% sodium carbonate. Phase-behavior measurements were carried out according to the method of Nelson et al. (52). The David Lloydminster oil field is near the Alberta-Saskatchewan border directly east of Edmonton. The oil has a density of 0.922 g/mL and a viscosity of 144 MPa s at 23 °C. The region of optimal phase behavior is shown at a surfactant concentration of 0.1 wt% in Figure 9. The region of optimal phase behavior is shaded. Above this region, type II +) behavior occurs, and type II(-) behavior occurs below the region of optimal phase behavior. Volume percent oil refers to the amount of oil present in the phase-behavior tube used. For a given oil-to-water ratio, a transition from type II(-) to type III to type II(+) occurs as salinity increases. As the amount of oil increases relative to the amount of aqueous phase, the same trend in phase behavior is seen.

Crude oil pumped from a storage unit to a tanker is to be expressed in tons/hr, but the field variables of density and the volumetric flow rate are measured in Ib/ft and gal/min, respectively. Determine the units and the numerical value of the factor necessary to convert the field variables to the desired output. 

The industry standard for bulk measurement for both crude oil and liquid products was the petroleum industry barrel (abbreviated bbl) but now the metric tonne and the cubic meter are more commonly used, especially in international trade. The metric tonne may be converted to the barrel volume unit by dividing the mass unit by the density (specific gravity) of the... 

The density is measured by placing a hydrometer with the API calibrations into the crude oil. Temperature and pressure readings are recorded at the same time and the reading is converted to the standard at 60°F and 1 atmosphere. 

All the indirect methods that are based on the determination of the colloidal properties of crude oil measure macroscopic properties such as density, viscosity, and molecular weight. An example is that the molecular weight of asphaltene... 

Density is not only just one of the most important physical parameters of crude oil and its products, but it is also an important characteristic for measuring the quality for crude oil and its products. The density of a sample shows its mass in specific volume. The classical definition of density is presented in equation (2.39). 

The density that is calculated in equation 2.39 is known as absolute density. However, this density is rarely used by crude oil chemists and only in special cases. Relative density is the parameter that is usually used for the characterization of crude oil and its products. Usually, relative density is measured at a reference temperature of 20°C. Relative density is calculated by equation (2.40). 

C, an asphaltene weight fraction of 0.1411, and a viscosity at 20 °C of 8580 mPa s. The Lindbergh had a density of 992 kg/m3 at 15 °C, an asphaltene weight fraction of 0.2067, and a viscosity at 20° C of 10,500 mPa-s. Of the two crude oils used, the Lindbergh oil was more viscous (10,500 mPa.s), and contained about one and a half times higher asphaltene than the Lloydminster heavy oil. The asphaltene contents of the crude oils were measured by precipitation with pentane. 

The molality convention is followed because crude oil consists of various mixtures of different molecules that make the determination of the gas mole fraction almost impossible to determine. Unlike the studies of noble gas solubilities in water, there is no comprehensive study that has investigated the noble gas solubility in oil as a function of oil density and temperature. While a linear relationship between solubility based on the two oils measured can be assumed (e.g., Ballentine et al. 1996) and to a first order is supported by the empirical approximations (Zanker 1977 ASTM 1985), this remains a limiting factor in the application of noble gas solubility studies involving an oil phase. 

Producing horizons penetrated by the wells were at a depth of 500-550 m. Inrunediately prior to steam injection, the crude oil had a density ranging from 0.985 to 0.990 and a viscosity of not more than 2000 centipoise, measured at 30 C. 

The partition of mercury to sample bottle walls is a known complicating effect to measurement of THg in some crude oil samples based on published investigations [8]. It certainly may be the case that some oils demonstrate container wall adsorption to a much greater extent than that discovered in the small number of oils examined in these experiments. Likewise, it was suspected that any volatile mercury may have been lost or oxidized by the time the speciation experiments were performed. The samples used for the speciation experiments had been opened several times for analysis and density measurements prior to speciation experiments. 

The mass of the crude sample that was injected into the boat is determined by measuring a second aliquot of the crade oil sample. A capped 2-mL GC vial is tared on a balance. A 100-jnl aliquot of flie crude oil sample is slowly drawn into the same syringe that is used to inject the sample into a boat. Bubbles are carefully excluded from the syringe. The sample is then injected into flie tared GC vial and weighed again. This procedure allows the mass of an injection to be measured directly, rather than calculated based upon a separate density determination. 

The crudes span geographically over large areas North Sea, European continent, Afiica, Asia, etc. This is a necessity since if the crude oils in the test matrix are interrelated one cannot universalize the results. Table 1 lists the erude oils and their origin. To start with we determined the inversion point (or alternatively, the maximum eontent of water that can be introduced into the oil without a phase separation). We have ehosen to study emulsions that are 10% below the inversion point Exeeptions in this respeet are the two European erodes with 5% water stabilized. The erode oils were eharacterized by means of density, surfaee tension, and viseosity measurements. The results are summarized in Table 2. All experiments involving emulsions were carried out at 50°C. The reason for working at elevated temperature is to melt the wax in the oils and thereby prevent the influence of the wax on emulsion stability. The elevated temperature is also more elosely related to the real working temperature used in the proeesses in the field. 

The density of a fluid is defined as the mass of a substance per unit volume. Density measurements are used to determine heaviness. For example, one gallon of water weighs 8.33 lb, one gallon of crude oil weighs 7.20 lb, and one gallon of gasoline weighs 6.15 lb. 

This is the most common measurement performed on petroleum products density is expressed in terms of API gravity. This measurement determines the weight of a crude oil per imit volume at 60°F, normally measured by the Hydrometer method ASTM D 287. 

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