Asphaltenes kinetics

An integrated basin modelling study applying asphaltene kinetics from reservoired petroleum in the Snorre Area, northern North Sea... 

Modelling of petroleum generation was performed using asphaltene kinetics determined on petroleum asphaltenes from Snorre oils. This approach was chosen in order to avoid problems associated with the kinetic variability encountered in the Draupne formation. The petroleum asphaltene kinetics was used to delineate the extent of the kitchen area, which reached the time/temperature conditions necessary for the generation of the analysed oil phase. The results thus differ from conventional oil window approximations as we utilize kinetic source rock parameters in the migrated oil for tracing out the generative basin. 

Basin modelling using asphaltene kinetics was performed to constrain where in the studied basins the required expulsion temperatures as defined by the asphaltene kinetic approach have been met. As discussed in Di Primio et al. (2000) a 5% TR was used as the threshold value for determination of the expulsion conditions of the petroleum phase. 

The concept of asphaltene as a tracer of maturity brings us to the concept of active kitchen determination . The asphaltene kinetics delineates the P T conditions which have been subjected to the source rock and contributed to the accumulation. From numerical modelling these areas are identified, compared to traditional SR kinetics and evaluated from the migration modelling. 

These results indicated that the Draupne formation in Kitchen 1 west and northwest of Snorre has not reached the level of transformation required by the asphaltene kinetic data from the Snorre field. Kitchen 1 was modelled to only have reached a transformation ratio of less than 5% (Fig. 6) at present. In addition the limited source rock volume in this area cannot account for the petroleum volumes in the Snorre field. Thus, we would suggest on the basis of our maturity modelling, that the proposed kitchen area west and northwest of the Snorre (Kitchen 1) is immature. Shows in the 33/6-2 well, classified as in situ generated, not representative of significant petroleum migration, support this hypothesis. Additionally the fact that the main intra-field maturity trend known in Snorre (Horstad et al. 1995) is the increase in biomarker and aromatic maturity parameters from south to north, suggests clearly that Kitchen 1 did not contribute to Snorre as any influx of lower maturity petroleum from... 

Fig. 6. Maturity evolution from asphaltene kinetics in Kitchen 1 defined in the 33/6-1 well, indicating that the area has not reached the required temperature as defined by the asphaltene kinetics.

Fig. 8. Maturity in the 34/4-3 well from asphaltene kinetics, indicating that the well is matching the required maturity compared with the reservoired Snorre oil.

Many studies on direct liquefaction of coal have been carried out since the 1910 s, and the effects of kinds of coal, pasting oil and catalyst, moisture, ash, temperature, hydrogen pressure, stirring and heating-up rate of paste on coal conversion, asphaltene and oil yields have been also investigated by many workers. However, few kinetic studies on their effects to reaction rate have been reported. 

Callejas, M. A., and Martmez, M. T., Hydroprocessing of a Maya Residue. 1. Intrinsic Kinetics of Asphaltene Removal Reactions. Energy Fuels, 2000. 14 pp. 1304—1308. 

Residuum desulfurization kinetics are generally not first order. Figure 5 illustrates this with a first-order plot for desulfurization of Arabian light residuum. On this type of plot a first-order reaction would yield a straight line with a slope corresponding to the reaction rate constant. The over-all desulfurization reaction is not therefore first order and can in fact be represented by second-order kinetics. However, the figure shows that it may also be considered as the sum of two competing first-order reactions. The rates of desulfurization of the oil and asphaltene fractions are reasonably well represented as first-order reactions whose... 

Feed source may also have a substantial effect on the distribution parameter (Tamm et al., 1981). Given the complexity of crude oil with reference to residuum properties, it is not surprising that differences in metal distribution parameters are observed. This finding suggests that optimal catalyst properties may vary with the residuum source. Galliasso et al. (1985) have compared the HDM kinetics of porphyrins and nonporphyrin compounds in both resins and asphaltenes. The individual... 

Nevertheless, the development of general kinetic data for the hydrodesulfurization of different feedstocks is complicated by the presence of a large number of sulfur compounds each of which may react at a different rate because of structural differences as well as differences in molecular weight. This may be reflected in the appearance of a complicated kinetic picture for hydrodesulfurization in which the kinetics is not, apparently, first order (Scott and Bridge, 1971). The overall desulfurization reaction may be satisfied by a second-order kinetic expression when it can, in fact, also be considered as two competing first-order reactions. These reactions are (1) the removal of nonasphaltene sulfur and (2) the removal of asphaltene sulfur. It is the sum of these reactions that gives the second-order kinetic relationship. 

The chemistry of coal liquefaction is not very well understood, even after more than two decades of research into the kinetics and mechanism of the process. There have been a number of models for conversion proposed, most of them focused on the several liquefaction products, including preasphaltenes, asphaltenes, oils, and gases. A survey of some of the models has been presented (1 ), and a common feature among them is the multiplicity of paths connecting all of the components. 

Figure 4. The effect of asphaltene source on the global kinetic rate parameters for the pathways illustrated in Figure 3 (7).

Neurock, M., A. Nigam, D.T. Trauth, and M.T. Klein, Asphaltene Pyrolysis Pathways and Kinetics Feedstock Dependence, in Tar Sand and Oil Upgrading Technology. S. Shih and M.C. Oballa, eds., AIChE Symposium Series, 72-79,1991. 

Nigam, A., M. Neurock, and M.T. Klein, Reconcilliationof Molecular Detail and Lumping An Asphaltene Thermolysis Example, in Kinetic and Thermodynamic Lumping of Multicomponent Mixtures. G. Astarita and S.I. Sandler, eds., Elsevier Science Publishers B.V., 1991. 

Application of this model to a residuum desulfurization gave a linear relationship. However, it is difficult to accept the desulfurization reaction as a reaction that requires the interaction of two sulfur-containing molecules (as dictated by the second-order kinetics). To accommodate this anomaly, it has been suggested that, as there are many different types of sulfur compounds in residua and each may react at a different rate, the differences in reaction rates offered a reasonable explanation for the apparent second-order behavior. For example, an investigation of the hydrodesulfurization of an Arabian light-atmospheric residuum showed that the overall reaction could not be adequately represented by a first-order relationship. However, the reaction could be represented as the sum of two competing first-order reactions and the rates of desulfurization of the two fractions (the oil fraction and the asphaltene fraction) could be well represented as an overall second-order reaction. 

Kodera, Y., Kondo, T., Isaito, S. Y., and Ukegawa, K., Continuous-distribution kinetic analysis for asphaltene hydrocracking, Energy Fuels 16, 291-296 (2000). 

Nigam, A., Neurock, M., and Klein, M., Reconciliation of molecular detail and lumping An asphaltene thermolysis example, in Kinetic and Thermodynamic Lumping of Multi-component Mixtures (G. Astarita, and S. I. Sandler Eds.), Elsevier, Amsterdam (1991). 

The thermal hydroconversion of Cold Lake asphaltenes was studied initially to provide a basis for evaluation of catalytic effectiveness in subsequent work. Series of thermal runs were made at 335°C, 365°C and 400°C and the reaction products were separated as described previously. Several kinetic models were tried, but after examining the variability of our data, we decided on the simple first-order asphaltene decomposition model shown below ... 

Equations (2) and (3) were fit to experimental data using nonlinear regression to obtain values of the first-order reaction rate constants and the stoichiometric coefficients at each temperature. The conversion data from the 400°C thermal run and the best fit of the kinetic model are shown in Figure 1. It is interesting to note that at the time of incipient coke formation ( 60 minutes) the asphaltene and maltene data deviate from predicted first-order behavior. From this we concluded that both asphaltenes and maltenes were participating in secondary coke-forming reactions. Further separation of the maltenes into resins (polar aromatics) and oils confirmed this to be true and showed that it was the resin fraction that was involved in coke formation. 

Table 2. Proponeil kinetic models for the Draupne formation, hosed on kerogen and asphaltenes...

Kinetic model Labile kerogen Stabile kerogen Kinetic from asphaltenes (34/4-7) MSSV-pyrolysis (Erdmann. 1999) ... 

Fig. 3. Kinetic signature of the Draupne Source Rock in the study area. The kinetic signature of the asphaltene fraction compared with measured extremes of bulk kerogen kinetic variability (labile and stable) as well as closed system compositional kinetics from Erdmann (1999).

Results from the modelling shows that the use of asphaltenes as a kinetic parameter is eligible, in particular if the source rock exhibits a... 

DI Primio, R., Horsfield, B. Guzman-Vega, M, A. 2000, Determining the temperature of petroleum formation from the kinetic properties of petroleum asphaltenes. Nature, 406, 173-176. 

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