摘要:

Petroleum asphaltenes are defined as material insoluble in pentane or heptane and the nature of the molecular species that constitute asphaltenes has been a well researched subject over the past three decades. These investigations have led to a general consensus of the majority of researchers that asphaltenes contain condensed aromatic systems carrying alkyl, cycloalkyl, and heteroatom substituents. A variety of molecular models has been developed which have been used to explain the behavior of asphaltenes in feedstocks during recovery and processing operations

ISSN:0884-3759    

DOI:10.1080/08843759608947559

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Asphaltene and wax phase behavior is quite different than the conventional “PVT” phase behavior. Asphaltenes exhibit a behavior at some thermodynamic states calledflocculation. That is, asphaltene particles or micelles aggregate or flocculate into larger aggregates or flocs. The locus of all thermodynamic points in a P-T-x phase diagram at which flocculation occurs is called the Asphaltene Deposition Envelope (ADE). Paraffin waxes, on the other hand, at some thermodynamic states, exhibit the phenomenon ofcrystallization. The locus of all thermodynamic points in a P-T-x phase diagram at which wax crystallization occurs is called the Wax Deposition Envelope (WDE). Asphaltene flocculation can be both reversible and irreversible (as expected from the asphaltene colloidal nature). Wax crystallization is generally a reversible process. However, paraffin waxes more than often precipitate together with resins and asphaltenes (which are said to be responsible for the observed irreversible thermodynamic phenomena). Hence, some wax precipitation is occasionally reported as irreversible. Measurement of the ADE and WDE boundaries, at in-situ conditions, is a challenging task. Measurement of asphaltene and wax solubility at in-situ conditions inside the ADE and WDE is even more challenging. The ADE and WDE data have practical significance and are very useful for modeling of reservoir fluid behavior. Asphaltene and wax data for a number of oils are presented and analyzed. This paper introduces and compares two powerful thermodynamic diagrams that summarize the phase behavior of asphaltenes and waxes, the ADE and WDE.

ISSN:0884-3759    

DOI:10.1080/08843759608947560

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The mechanism of formation of carbonaceous deposits from hydrocracked Athabaca bitumen is shown to result in both isotropic and anisotropic solids. The formation of mesophase spheres present as a separate liquid phase has been observed in the laboratory High severity results in the formation of an increased amount of anisotropic solid which is observed in both laboratory and commercial samples. The formation of these deposits in the downstream separators of a commercial plant has occurred and is a hindrance to reliable operation. A strategy to reduce the formation of these deposits in a commercial plant was evaluated in a series of laboratory experiments. The use of process-derived gas oils can be used as quench oil to lower the temperature of the commercial separators. There was no increase in the rate of toluene insoluble formation as a result of the use of quench oils, which allowed the full advantage of the temperature decrease to be achieved. A qualitative comparison of the build-up of deposits in the commercial separators is provided from separator vessel monitoring.

ISSN:0884-3759    

DOI:10.1080/08843759608947561

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A microscopic study of the onset of asphaltene precipitation is reported. The onset conditions can be quantified by measurement of mixture refractive index, together with microscopic observations of particulate formation in mixtures of oil and precipitant, with or without added solvents. For isooctane mixtures with a variety of hydrocarbon solvents and a crude oil from Alaska, the onset of precipitation occurs over a narrow range of solution refractive index. Addition of polar solvents or different precipitating agents can shift the refractive index at which precipitation begins. Refractive index decreases when a crude oil is diluted by precipitant, as in this study, or when changes in temperature and pressure alter the relative molar volumes of species in the oil. If it falls below some critical value, resin/asphaltene aggregates that had been in stable dispersion become unstable and precipitate. These observations provide a method of screening solvents to differentiate between those that prevent precipitation mainly by maintaining a higher mixture refractive index and others that may participate in or disrupt asphaltene/resin interactions.

ISSN:0884-3759    

DOI:10.1080/08843759608947562

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The asphaltene fraction of crude oil contains a variety of acidic and basic functional groups. During oil production and transportation, changes in temperature, pressure or oil composition can cause asphaltenes to precipitate out crude oil through the flocculation among these polar functional groups. In this study, two types of oil-soluble polymers, dodecylphenolic resin and poly (octadecene maleic anhydride), were synthesized and used to prevent asphaltenes from flocculating in heptane media through the acid-base interactions with asphaltenes. The experimental results indicate that these polymers can associate with asphaltenes to either inhibit or delay the growth of asphaltene aggregates in alkane media. However, multiple polar groups on a polymer molecule make it possible to associate with more than one asphaltene molecule, resulting in the hetero-coagulation between asphaltenes and polymers. It was found that the size of the asphaltene-polymer aggregates was strongly affected by the polymer-to-asphaltene weight (or number) ratio. At low polymer-to-asphaltene weight ratios, asphaltenes keep flocculating with themselves and with polymers until the floes precipitate out of solution. On the other hand, at high polymer-to-asphaltene weight ratios, asphaltene-polymer aggregates peptized by the extra polymer molecules can remain fairly stable in the solution.

ISSN:0884-3759    

DOI:10.1080/08843759608947563

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Conductivities of asphaltenes were measured as a function of concentration in solvents of varying permittivity. The molar conductivity was calculated assuming the molecular weight of asphaltenes to be 1000 g/mol

ISSN:0884-3759    

DOI:10.1080/08843759608947564

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Presently, no definitive technique has been reported that measures the onset-of-precipitation of asphaltenes from a hydrocracker product at process conditions. In the present paper, a detection technique utilizing heat transfer analysis is presented. The method is suitable for the high temperature and pressure conditions in upgrading and is based on a heat transfer analysis of the precipitated layer. The modeling of the technique is provided, as well as details of the heat transfer vessel. Results from glycerol and corn oil model fluid experiments and simulations demonstrate the validity of the method Preliminary experimental results for Cold Lake bitumen are presented along with recommendations on how the method will be further improved.

ISSN:0884-3759    

DOI:10.1080/08843759608947565

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Interactions among asphalt components have significant effects on the performance of asphalt binder. To understand those interactions, four asphalts, SHRP AAA-I, AAD-I, AAF-I, and AAG-I, were fractionated into three generic fractions according to Corbett's procedure and reblended into asphaltenes/aromatics/saturates ternary mixtures in various ratios. Mixtures were oxidatively aged with atmospheric air at temperatures of 87.7, 93.3, and 98.8°C for 5 to 33 days. The changes in chemical composition and physical properties were monitored using fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical rheometry

ISSN:0884-3759    

DOI:10.1080/08843759608947566

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The phase behaviour of heavy oil mixtures was studied using an X-ray imaging system. Batch phase experiments were performed at temperatures and pressures up to 725 K and 7 MPa. Complex phase behaviour such as liquid-liquid-vapour and solid-liquid-liquid-vapour were observed and preliminary experimental phase diagrams were constructed. This observed complex phase behaviour is consistent with thermodynamic theory and such phase behaviour can be modelled using the Peng-Robinson equation of state and the tangent plane criterion. These latter points are illustrated through the phase diagram for a model reservoir fluid (ethane + propane + n-butane + phenanthrene) which exhibits solid-liquid-liquid-vapour phase behaviour. Example predicted and experimental phase diagrams are presented for this model system.

ISSN:0884-3759    

DOI:10.1080/08843759608947567

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

For compositional simulation purposes, a new method has been developed for estimating the specific gravities of pseudo-components that are required to characterize the heavy components of crude oils. This method makes use of the always available data for the heavy components of crude oils: average molecular weight and specific gravity of the heptanes-plus (C7+) fraction

ISSN:0884-3759    

DOI:10.1080/08843759608947568

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor