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In this paper a semianalytical model has been proposed to predict the rate at which oil components dissolve in water when an oil spill occurs in a marine environment. The model breaks the oil into a number of pseudocomponents proportional to the number of compounds originally present in the oil and calculates the rate of dissolution for each component. In addition, the components are divided into paraffinic, naphthenic, and aromatic hydrocarbon types and the amount of dissolution of each pseudocomponent is calculated versus time. In this method the concentration of most toxic components of oil (mainly monoaromatics) is determined. The model considers variable surface area and slick thickness and requires oil specifications (i.e., American Petroleum Institute [API] gravity and boiling point) in addition to air and water temperatures and speeds. The model has been applied to a Kuwaiti crude oil and its products naphtha and kerosene samples at 20 degrees C and 40 degrees C. The results could be useful in selection of an appropriate method for oil spill clean up as well as simulation of environmental impact of oil spill from toxicity points of view.

The precipitation of asphaltene and waxes occurs when crude oil characteristics change as a consequence of pressure, temperature variations, and/or chemical modifications, etc. The costs associated with the cleaning of deposition on the production equipment and the loss of profit opportunities can go beyond hundreds of millions of USD. Thus, there is a strong incentive to search for ways to mitigate deposit formation during the crude production process. A light crude bottom hole fluid sample from a deep well with an asphaltene deposition problem was analyzed in the laboratory. Basic data on density, viscosity, bubble point, GOR, and asphaltene onset pressure were measured at a PVT laboratory. Asphaltene characterization, as a prescreening for appropriate inhibitors, has been conducted using asphaltene phase diagrams (APD). The APD generated from two developed software programs in both Matlab and Excel codes were favorably compared with the phase behavior of other oil samples available in the literature and has shown to be an excellent match. Various test methods were used to demonstrate the asphaltene instability of the oil samples. Eleven chemical inhibitors from five global companies were screened for testing to inhibit the precipitation. The optimum concentration and the amount of reduction in precipitation were determined for all of these chemicals to identify the most suitable chemicals. Finally, some recommendations are given for the field application of chemicals. [ABSTRACT FROM AUTHOR]

In this article, difficulties in accurate estimation of thermophysical properties of heavy petroleum fluids and natural gas systems through conventional methods are discussed. Potential approaches in characterization of such systems that use direct measurable properties of mixtures are investigated. It is shown that properties such as velocities of sound and light and dipole moment might be appropriate properties to measure for characterization and property estimation of heavy petroleum fluids. [ABSTRACT FROM AUTHOR]

A new correlation is developed for predicting the Reid vapor pressure (RVP) of gasoline and naphtha based on a true vapor pressure (TVP) correlation. The input parameters for this correlation are the mid-boiling point, specific gravity, critical temperature, and critical pressure, where the critical properties may be estimated from the boiling point and specific gravity using available methods. The proposed correlation is evaluated with data collected on 50 gasoline samples from crude oils from around the world with API gravity ranges from 41 to 87, average boiling point ranges from 316 to 494 K and RVP of 0.007 to 1.15 bars (0.1–17 psia). The average error from the proposed correlation is about 0.06 bar (0.88 psia). Two other simple methods for prediction of RVP available in the literature have been evaluated with the same data bank and compared with the proposed method. [ABSTRACT FROM AUTHOR]

Asphaltene extracted from a crude oil covers a wide range of molecules that would similarly act in terms of solubility in general but they may differ in terms of precipitation behavior due to different molecular structures. For this reason, they are commonly represented as a solubility class, not a particular molecule though each sub-fraction of asphaltene may have its own precipitation tendency. In recent years, the impact of water presence on the precipitation of these molecules has attracted attention due to increased production of water, although the reported results are somewhat inconsistent. In this study, a systematic experimental study was performed to investigate the impact of aqueous phase, which composed of deionized water and ions of single, double, and three valence with net positive and negative charges on asphaltene precipitation from a synthetic oil composed of toluene and asphaltene. The aqueous phase was emulsified within this synthetic oil phase using ultrasonic mixer. Then, the oil phase was divided into three fractions named oil 1, 2, and 3, respectively depending on the degree of their desire to remain in the emulsion. The results showed that oils 1, 2, and 3 have different precipitation curves. The precipitation became more intensified even up to four fold from oil 1 to 3. Moreover, the presence of ions with higher valence in the aqueous phase drew extra asphaltene molecules from oil 1 to oil 2 and then oil 3 (i.e. from bulk to the interface) which, in turn, changed the precipitation curve. The experimental results also showed that the relative concentration of asphaltene sub-fractions in oils 1, 2 and 3 determines the shape of the final precipitation curve and the onset point of precipitation. Unlabelled Image • A new simple and robust approach to identify sub-fractions of asphaltene. • Impact of brines of different ions on precipitation of asphaltene. • Different classes of asphaltene were distributed in the presence of different brines. • Each class showed different propensity of asphaltene to precipitate. • Ions of higher valence increased asphaltene presence at the interface of oil and water. [ABSTRACT FROM AUTHOR]

As crude oil gets denser and heavier, the precipitation and deposition of asphaltene causes severe problems in various sectors of oil industry from oil reservoirs to refineries. Asphaltene deposition in some wellbores may cause a partial or total production loss depending on its severity. Several studies have attempted to model asphaltene deposition along the wellbore in which a fixed shape of deposited asphaltene profile is assumed over time. Having said though there exist field experiences which report evolutionary behavior of deposited asphaltene in terms of growth pattern and structure. In this study, a new model is proposed that considers the removal propensity of deposited asphaltene from the wall along with its deposition in another location of the same well. The structure of asphaltene deposits, their growth pattern and movement during production which is predicted in this model are consistent with the field data quantitatively. The proposed model also predicts that as production continues, the deposits in some locations of the well get thicker and the consequent increase in pressure drop lowers the location of bubble point which causes dissolution and removal of asphaltene in upper parts due to higher solubility of asphaltene and higher velocity of fluid in that region. Thus, the proposed model would more accurately simulate the wellbore deposition as compared with a field case-study. The finding of this study is hence a step forward for understanding of the behavior of asphaltene deposition in oil producing wells. • Prediction of asphaltene blockage in vertical wellbores during oil production • Model includes evolutionary behaviour of deposition, removal and dissolution. • Location of asphaltene blockage would be shifted given local pressure and velocity. • Consistency of the theoretical results with the field data. [ABSTRACT FROM AUTHOR]