Dead Oil Samples Research Articles

Asphaltene Adsorption onto Acidic/Basic Metal Oxide Nanoparticles toward in Situ Upgrading of Reservoir Oils by Nanotechnology

The effects of surface acidity and basicity of metal oxide nanoparticles on the thermodynamics of asphaltene adsorption were studied. Three different categories of metal oxides/salts with acidic (WO3 and NiO), amphoteric (Fe2O3 and ZrO2), and basic (MgO and CaCO3) surfaces were synthesized, and their textural, structural, and acid-base properties were characterized. Asphaltenes were extracted from a dead oil sample and characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The acid and base numbers of the asphaltenes were measured. The nanoparticles were added to the asphaltene-toluene solutions, and the amount of adsorbed asphaltene was obtained through centrifugation followed by UV-vis spectroscopy of the supernatant liquid and temperature-programmed oxidation analysis of the precipitated solid. The concentrations of organic acid and base groups in the asphaltenes are 2.75 and 12.34 mg of KOH/g, respectively, indicating that the asphaltenes are more basic in nature. Isotherms of the asphaltene adsorption onto the six metal oxides/salts fit the Langmuir model closely. The asphaltene adsorption capacity of the nanoparticles is 1.23-3.67 mg/m(2) and decreases in the order of NiO > Fe2O3 > WO3 > MgO > CaCO3 > ZrO2, concomitant with the synergetic effects of acidity and the net charge of the surfaces. High-resolution transmission electron microscopy illustrates that the asphaltenes are spread out over the surfaces with no short-range/long-range order. The adsorption of the asphaltenes onto the six samples is exothermic and spontaneous with the Gibbs energy change of -27.80 to -28.79 kJ/mol at 25 °C. The absolute value of the enthalpy change of the adsorption is calculated to be within the range of 5-20 kJ/mol. Acid-base interaction and electrostatic attraction seem to be the dominant forces contributing to the adsorption of the asphaltenes onto the metal oxide/salt surfaces.

An Improved CO2–Oil Minimum Miscibility Pressure Correlation for Live and Dead Crude Oils

An improved CO2–oil minimum miscibility pressure (MMP) correlation has been successfully developed to more accurately determine the CO2–oil MMP for a wide range of live and dead crude oils. Experimentally, slim-tube tests have been conducted to determine the CO2–oil MMPs for four crude oil samples with high molecular weights of C7+ fraction. Theoretically, the newly developed CO2–oil MMP correlation is originated from a CO2–oil MMP database from the literature that covers 51 CO2–oil MMP data for various live and dead oil samples, especially those with high C7+ molecular weights. The new CO2–oil MMP correlation is expressed as a function of reservoir temperature, C7+ molecular weight, and mole fraction ratio of volatile components (N2 and CH4) to intermediate components (CO2, H2S, and C2–C6). Compared to nine commonly used CO2–oil MMP correlations in the literature, it is found that the new CO2–oil MMP correlation provides the best reproduction of the literature CO2–oil MMP data with a percentage average a...

Inhibition of Asphaltene Precipitation by TiO2, SiO2, and ZrO2 Nanofluids

Asphaltene precipitation causes several problems during crude oil production, transportation, and refinery processes. Therefore, finding an inhibitor to prevent or delay asphaltene precipitation is of paramount importance. In this work, effects of TiO2, ZrO2, and SiO2 fine nanoparticles in organic-based nanofluids have been investigated to study their potential for stabilizing asphaltene particles in oil. To this end, polarized light microscopy has been applied to determine the onset of asphaltene precipitation by titration of dead oil samples from Iranian crude oil reservoirs with n-heptane in the presence of nanofluids. Results show that rutile (TiO2) fine nanoparticles can effectively enhance the asphaltene stability in acidic conditions and act inversely in basic conditions. It was found that the required amount of n-heptane for destabilizing the colloidal asphaltene is considerably higher in presence of TiO2 nanofluids at pH below 4. The FTIR spectroscopy indicates changes in n-heptane insoluble asph...

An Experimental Measurement and Modeling of Asphaltene Precipitation in Crude Oil

In this study, the amount of asphaltene precipitation produced by adding different ratios of n-alkanes (n-pentane, hexane, n-heptane, n-nonane) into two dead oil samples from Iranian oil fields has been measured. The obtained results were compatible with the results of other researchers. Meanwhile, the reversibility of asphaltene precipitation process has been investigated as an important subject in this phenomenon. Then, by using the experimental data and optimization, the scaling equation's coefficients were calculated and then the amount of asphaltene precipitation and the onset point have been obtained by the scaling approach. Finally, the obtained results have been compared with the experimental data and the model's accuracy was approved.

Shear and Electrical Property Measurements of Water-in-Oil Emulsions and Implications for Multiphase Flow Meters

We prepared water-in-oil emulsions by blending a synthetic brine representative of the formation water from a production well with dead oil samples from the same well. The composition of the oil was thoroughly characterized using an extended saturates−aromatics−resins−asphaltenes analysis, high-temperature gas chromatography, and two-dimensional gas chromatography with time-of-flight mass spectrometry. The relative dielectric permittivities of the emulsions (10−50% water volume fraction) were measured at 1 kHz using a coaxial capacitor and between 0.2 and 13.5 GHz using dielectric relaxation spectroscopy. The dielectric permittivity is one of the properties used by some multiphase flow meters to determine water volume fractions in production systems. The water volume fractions calculated from the measured oil, water, and emulsion permittivities using the Bruggeman equation were systematically above the measured water fraction by an average of 10% and a maximum of 20%. In contrast, one of Hanai’s equations systematically underpredicts the water fraction by an average of 6%, with a maximum of 12%. Importantly, the permittivities measured using a capacitor changed by 14% over 15 min before reaching its steady-state value. This result has significant implications on the required residence time of fluids in capacitance-based multiphase flow meters. The emulsion permittivities exhibited significant dispersion at frequencies between 0.2 and 1 GHz, a result of importance to multiphase flow meters operating at microwave frequencies. We also measured the shear properties of the emulsion samples and compared them to standard models for estimating emulsion viscosities. The results of the shear experiments have implications for total mass flow rates estimated from multiphase flow meters using differential pressure measurements.

Dispersion properties of NMR relaxation for crude oil

Special requirements for design of tools used for wireline NMR logging and NMR logging while drilling and for interpretation model are demanded due to the dispersion properties of NMR relaxation for crude oil. NMR longitudinal relaxation time (T 1) and transverse relaxation time (T 2) of the dead oil samples with different viscosities were measured by NMR spectrometers with a Larmor frequency of 2 MHz and 23 MHz at five different temperatures respectively. The results showed thatT 1 was obviously dependent on the Larmor frequency of NMR spectrometer. The degree ofT 1 dispersion became stronger with the increasing crude oil viscosity, Larmor frequency and the viscosity/temperature ratio.T 2 was independent of NMR spectrometer measuring frequency. It is suggested that the resonance frequency should be selected lower than 2 MHz when measuringT 1 in logging while-drilling and thatT 1 dispersion should be corrected when Larmor frequency is higher than 2 MHz.

Investigation of Asphaltene Precipitation Process for Kuwaiti Reservoir

As part of an Enhanced Oil Recovery (EOR) research program, Asphalting precipitation processes were investigated for a Kuwaiti dead oil sample using different hydrocarbons and carbon dioxide as precipitants at the ambient and high pressure of 3000 psig conditions. The hydrocarbons used as precipitants were ethane (C2), propane (C3), butane (C4), normal pentane (n-C5), normal hexane (n-C6), and normal heptane (n-C7). The equipment used for this investigation was a mercury-free, variable volume, fully visual JEFRI-DBR PVT system with laser light scattering. The minimum critical value of precipitants concentration for the oil sample has been identified at the ambient and high-pressure conditions for each precipitant. Our investigation has revealed that for this oil sample the most powerful asphaltene precipitant were CO2 followed by C2, C3, C4, n-C5, n-C6, and n-C7. Moreover, the effect of pressure and temperature on the asphaltene precipitation has been investigated experimentally for CO2, n-C5, n-C6, and n-C7. The precipitation and redissolution of asphaltene upon the addition and removal of CO2 and light alkanes (C2–C4), at 3000 psig and ambient temperatures, have shown evidence of reversibility of asphaltene precipitation. A comprehensive fluid characterization analysis for the oil sample has been performed including, physical properties of crude oil, compositional, molecular weight (Mw), and SARA analyses. Advanced analytical techniques such as 1H and 13C NMR and IR spectrometers have been utilized to investigate the molecular structure of the asphaltene for this sample. It was concluded that the asphaltene molecules for this oil contain 120 total aromatic carbons with 42 aromatic rings, 114 naphthenic rings, and 5–7 sets of condensed aromatic rings.

ORGANIC PRECIPITATES IN OIL PRODUCTION OF A VENEZUELAN OIL FIELD

A very light crude oil is being produced in an oil field in Venezuela. Such oils are susceptible to asphaltene precipitation as the reservoir pressure decreases during production. An asphaltene deposit has been found in the tubing of one of the wells and in the bottom sediment of the tanks on site. Dead oil samples from the well head of seven different producers in the field were analyzed by three different companies. The laboratory results covering the following aspects of different solvents show significant differences: asphaltene content, asphaltene/resin ratio, molecular mass of the precipitated asphaltenes, flocculation point, Vanadium/nickel ratio, precipitated asphaltenes, and the Hildebrand parameter. Using different consistency checks and establishing correlations among the results, the analysis of one lab is strongly favored against the others. The analytical results are discussed in detail, including the correlation between asphaltenes and the well situation regarding perforation depth and the phase behavior of the produced oil.

Modification of multisolid phase model for prediction of wax precipitation: a new and effective solution method

Problems related to precipitation and crystallization of waxes (solid paraffins) during production, transportation and processing of crude oil, cause major difficulties in these processes. This paper presents a modified multisolid phase model for predicting phase equilibria for oil mixtures taking into account the possible formation of a wax phase. This modified model is able to predict wax appearance point (WAP) and amount of precipitated wax in various oil samples. The vapor and liquid phases are described using the Peng–Robinson EOS. For the first three oil samples, heavy fraction properties are evaluated by use of the average properties method and for the second three oils PNA analysis is used. On the contrary to the original multisolid phase model which considers only liquid and solid(s) phases, this work considers vapor phase (in addition to liquid and solid(s) phases), and, therefore, because of this modification, prediction of pressure and composition effects on WAP will be possible. In this work, pressure effects on dead oil (stock-tank-oil, at above bubble point pressure, that there is not any gas) samples, have been studied and according to predictions suggested by previous works the WAP of oils raise as pressure increase. A second prediction based on the modified multisolid phase model refers to WAP decreases with increase of light component concentration. The calculation results obtained in this work, agree very well with experimental results and results obtained from other works.