FR2906481A1 - Hydrocarbon thermal cracking modeling by individualizing chemical classes of compounds, defining cracking reaction scheme, defining kinetic scheme, pyrolysis experimentation and determining kinetic parameters and stoichiometric coefficients - Google Patents

Abstract

Modeling thermal cracking of hydrocarbon, by individualizing the chemical classes of gaseous fraction containing sulfur dioxide and 1-4C hydrocarbons, fractions of saturated hydrocarbons with 6-14C and more than 14C, nitrogen, sulfur and oxygen compounds and solid fraction, defining cracking reaction scheme, defining a kinetic scheme by determining the kinetic parameters and stoichiometric coefficients, pyrolysis experimentation, determining the production and disappearances of chemical classes at simulated temperatures and determining kinetic parameters and stoichiometric coefficients. Modeling thermal cracking of hydrocarbon, comprises: (A) individualizing the chemical classes of gaseous fraction containing sulfur dioxide, hydrocarbons with 1 carbon atom (C1), hydrocarbons with 2 carbon atoms (C2), hydrocarbons with 3 carbon atoms (C3) and hydrocarbons with 4 carbon atoms (C4); fraction of saturated hydrocarbons with 6-14 carbon atoms (C14- fraction), alkylated, preferably methylated, and aromatic hydrocarbons of benzene, toluene, m-, p-, o-xylene and naphthalene; saturated hydrocarbons with more than 14 carbon atoms (C14+ fraction) containing saturated C14+, aromatic hydrocarbons having more than 14 carbon atoms (Aro 1) and aromatic hydrocabons having more than 14 carbon atoms and resulting from thermal cracking of different families of hydrocarbon (Aro 2 and Aro 3); nitrogen, sulfur and oxygen compounds (NSO); and solid fraction containing polyaromatic solid resulting from thermal cracking of the aromatic fraction, preferably thermally reactive and thermally inert polyaromatic solid (B) defining a pattern of cracking reaction of a hydrocarbon, by assessing the decomposing of each reagent into gaseous fraction, C14- fraction, C14+ fraction and solid fraction according to a table given in the specification (C) defining a kinetic scheme by determining the kinetic parameters and stoichiometric coefficients associated with the reaction scheme (D) conducting pyrolysis experiments in a closed environment to monitor production and disappearances of chemical classes at different temperatures and to ensure the quality of the mass balance (E) determining the production and disappearances of chemical classes at the temperatures with a simulation based on the reaction scheme (F) and determining the kinetic parameters and stoichiometric coefficients using a numerical inversion by minimizing the difference between the simulated productions and disappearances and productions and disappearances in pyrolyses.

Description

The invention relates to a method for modeling thermal cracking

  petroleum products, and in particular oils. Petroleum fluids are very complex mixtures of organic compounds.

  The main families of compounds are saturated hydrocarbons, aromatics, resins and asphaltenes.  Saturated hydrocarbons form the majority group except in degraded heavy oils.  This family includes n-alkanes, but also isoalkanes and cycloalkanes.  The aromatic hydrocarbon family contains compounds of 1 to 5 aromatic rings, substituted by methyl or alkyl groups.  The sulfur compounds of the oils include thiols, sulfides, thiophenes, benzothiophenes, dibenzothiophenes, naphthothiophenes, and bithiophenes.  Resins and asphaltenes are molecules of high molecular mass containing heteroatoms: N, S and O, hence the name NSO.  Crude oil may contain traces of metals.  Vanadium can account for up to 75% of the metal content followed by nickel.  The following nomenclature is used in the remainder of the description: The type of kerogen of type I, II, III, II is the geological types of kerogen known to those skilled in the art: type I kerogen, type II kerogen, kerogen of type III, Kerogen type They (containing sulfur).  For the definition of Type I, II and III kerogens, see Durand et al. 1972; Durand and Espitalié, 1973; and for Type II-S at Orr and Sinninghe Damsté 1986.  In the description which follows, kerogen 1, kerogen 2, kerogen 3 and kerogen 4 will be referred to as the various chemical classes of kerogen determined for the implementation of the present invention within each geological type.  The other chemical classes determined in the method according to the invention are: Cl: family of hydrocarbons with 1 carbon atom C2: family of hydrocarbons with 2 carbon atoms C3: family of hydrocarbons with 3 carbon atoms C4: 4-carbon hydrocarbon family C14-: saturated and unsaturated hydrocarbons having 6 to 14 carbon atoms aro BTXN: aromatic hydrocarbons of benzene, toluene, m-, p-, o-xylene, naphthalene aryl alkyl type: other alkylated aromatic hydrocarbons having 6 to 14 carbon atoms 2906481 2 aro-methyl: methylated aromatic hydrocarbons having 6 to 14 carbon atoms C14 + sat: saturated and unsaturated hydrocarbons having more than 14 carbon atoms Aro 1: aromatic hydrocarbons having more than 14 carbon atoms Aro 2 and aro 3: aromatic hydrocarbons having more than 14 carbon atoms and resulting in thermal cracking of different families of hydrocarbons.  Preload: polyaromatic solid resulting from the thermal cracking of the aromatic fraction, still hydrogenated, therefore still thermally reactive.  Char: thermally inert polyaromatic solid.  Resins and asphaltenes are high molecular weight molecules containing heteroatoms: nitrogen, sulfur and oxygen, and will be referred to as NSO.  NSOI: NSO compounds soluble in polar solvents.  NSO2: soluble NSO compounds in saturated solvents NSOS = NSO tot = NSO1 + NSO2 = resins + asphaltenes The invention can also be applied to the understanding of the processes of formation of oil and gas in sedimentary rocks, particularly the kinetics of thermal cracking of kerogen and associated petroleum products in source rocks: primary cracking and secondary cracking.  STATE OF THE ART The state of the art can be represented by the content of the bibliographic references below, to which the description refers.  - Behar, F. , Ungerer, P. , Kressmann, S. , Rudkiewicz, J.  L. , 1991.  Thermal evolution of crude oils in sedimentary basins: experimental simulation in a confined system and kinetic modeling.  Oil and Gas Science and Technology 46, 151-181.  - Behar, F. , Vandenbroucke, M. , Tang Y. , Marquis F. , Espitalie J. , 1997.  Thermal cracking of kerogen in open and closed systems: determination of kinetic parameters and stoichiometric coefficients for oil and gas generation.  Organic Geochemistry 26, 321-339.  - Durand B. , Espitalie J. , Nicaise N. , Combaz A. , 1972.  Study of the insoluble organic matter (kerogen) of the Toarcian clays of the Paris Basin.  I- Studies by optical methods, elementary analysis, study in microscopy and electron diffraction.  Oil and gas science and technology 27, 865-884.  2906481 3 - Durand B. , Espitalie J. , 1973.  Evolution of organic matter during the burial of sediments.  Proceedings of the Academy of Sciences, 276, 2253-2256.  Espitalie J. , Laporte J.  L. , Madec M. , Marquis F. , Leplat P. , Paulet J. , Boutefeu A. , 1977.  5 Rapid method for characterizing source rocks, their petroleum potential and their degree of evolution.  Oil and gas science and technology 32, 23-42.  - Horsfield, B. , Disko U. , Leibtner F. , 1989.  The micro scale simulation of maturation: outline of a new technique and its potential application.  Geologische Rundschau 78/1, 361-374.  10 - Khorasheh, F. , Gray, M. R. , 1993.  High-pressure thermal cracking of n-hexadecane.  Industrial Engineering and Chemical Research 32, 1853-1863.  - Luo, L. vs. , Michael, G. E. , 1994.  A multicomponent oilcracking model for modeling and composition of reservoir oil.  Organic Geochemistry 21, 911-925.  Lewan, M. , 1993.  Laboratory simulation of petroleum formation: Hydrous pyrolysis.  In: 15 Engel M. H. , Macko, S.  (Ed), Organic Geochemistry Principles and Applications, Plenum, New York, pp.  419-442.  - Lewan M.  D. , Winters J.  vs. , Mac Donald J.  H. , 1979.  Generation of oil-like pyrolysate from organic rich shales.  Science 203, 897-899.  - Lorant, F. , 1999.  Late genesis of hydrocarbon gases in sedimentary basins: kinetic and isotopic studies.  Thesis ENSPM-University of Strasbourg 1.  - Lorant F. , Behar F. , Vandenbroucke M. , Mc Kinney D.  E. , Tang Y. , 2000.  Methane Generation from Methylated Aromatics: Kinetic Study and Carbon Isotope Modeling.  Energy and Fuels 14, 1143-1155.  25 - Orr W.  L, Sinninghe Damsté J.  S.  (1990) Geochemistry of sulfur in petroleum systems.  In Geochemistry of sulfur in fossil fuels (Orr W.  L.  and White C.  Mr. ), pp.  3-29, ACS symposium series 429.  Tissot B. 1969.  First data on the mechanisms and kinetics of oil formation in sedimentary basins.  Simulation of a reaction scheme on a computer.  Oil and gas science and technology 24, 470-501.  - Ungerer P. , Pelet R. , 1987.  Extrapolation of the kinetics of oil and gas formation from laboratory experiments to sedimentary basins.  Nature 327, 52-54.  Ungerer, P. , Behar, F. , Villalba, M. , Heum, O. R. , 1988.  Kinetic modeling of oil cracking.  Organic Geochemistry 13, 857-868.  Cracking of Oils Thermal cracking is a radical mechanism that has been demonstrated by studying the cracking of hydrocarbons.  Studies have been conducted on some model compounds.  Thus work has been published on the cracking of n-hexane and n-hexadecane.  Studies have also been published on C25 n-alkane (n-pentacosane) as heavy paraffin model compounds (Behar and Vandenbroucke, 1996).  Finally, a theoretical model for calculating the overall cracking rates of n-alkanes from C3 to C32 has been proposed.  The family of cycloalkanes which represent an important chemical class of petroleum fluids has been studied very little in thermal kinetics.  Similarly, very little work has been published on the cracking of aromatic hydrocarbons.  Moreover, given the chemical complexity of this family, cracking mechanisms are far from known.  Information on apparent kinetic parameters was obtained from studies of ethylbenzene, n-butylbenzene, n-dodecylbenzene, alkylated polycyclic structures and 9-methylphenanthrene.  Tetralin (1,2,3,4-tetrahydronaphthalene) has also been studied as a representative model compound of the naphthenoaromatic family by many authors (Khorasheh and Gray, 1993).  A detailed kinetic scheme for the thermal cracking of tetralin has been proposed and the pyrolysis of 2-ethyltetralin has also been studied.  The pyrolysis of natural fractions of petroleum fluids has been the subject of some experimental studies (Ungerer et al. 1988; Kuo and Michael, 1994) in order to propose empirical global models of cracking.  An empirical model has been proposed for the cracking of oils from experimental data on 2 oils.  The kinetic scheme comprises 11 classes which includes 5 aliphatic classes (methane, ethane, (propane + butane), saturated C6-C14, saturated C14 +) and 6 aromatic classes (BTXN (Benzene + Toluene + Xylene + Naphthalene), C9-C14 aromatics, unstable aromatic C14 +, more stable aromatic C14 +, precoke and coke).  In this model, in order to reduce the number of classes, the same frequency factor was applied for all unstable chemical classes.  In addition, each reaction is mono energetic.  This highly simplified model is not very predictive and could not be used to account for the composition observations of petroleum fluids that have undergone intense thermal cracking in natural reservoirs.  A modified version has been published more recently, but it still has very large uncertainties; in particular, this model does not restore the respective quantities of gas and oil present in the natural reservoirs and the liquid fraction is too enriched in aromatic structures with respect to the natural fluids.  An attempt has been made to develop real kinetic patterns on a complex mixture of model compounds.  This scheme after lumping has 5000 reactions.  The model reports the cracking of a mixture of 52 paraffin-dominated molecules: linear alkanes (from CH4 to C30H62), branched alkanes (including pristane and phytane), naphthenes (propylcyclopentane and propylycyclohexane), tetralin , 1-methylindane, 4 aromatics (benzene, toluene, butylbenzene and decylbenzene), 3 heteroatom compounds (di-isopropyl disulfide, isopropyl mercaptan, and H2S) and naphthalene.  A globalization by the "Iumping" of species was carried out to reduce the size of the system of elementary reactions.  The "Iumping" method used consists of grouping all 10 isomers of function into a pseudo-compound.  The model thus comprises 5200 processes.  The model focuses mainly on the pyrolysis of alkanes whose cracking is presented in the model by reactions of order 1/2 with activation energies of about 70 kcal / mol.  The role of the alkylaromatic and naphthenoaromatic compounds in the model is the inhibition of pyrolysis of alkanes by formation of the radicals stabilized by resonance.  The aromatic compounds are under-represented in the model and their cracking is limited to average conversions.  Heavy compounds: resins and asphaltenes are not taken into account in the model.  On the other hand, the simple sulfur molecules used in the (disulfide, mercaptan) model are not representative of this class in real oils, which mainly comprise sulfur-containing aromatic compounds whose thermal behavior has not yet been elucidated (thiophene). benzothiophene, dibenzothiophene, naphthenothiophenes).  In conclusion, at the present time the available data are either precise studies on model compounds, or limited or poorly predictive studies on petroleum fluids or fractions of petroleum fluids.  Also an originality of the method according to the invention concerning the cracking of petroleum products, is to propose a scheme by a limited number of global chemical classes and to constrain the determination of global kinetic parameters with those obtained on model compounds.  Application to the Secondary Cracking of Products Derived from the Thermal Decomposition of Kerosene With particular reference to cracking of kerogen, it is recognized that the process of forming oil and gas in sedimentary basins is the result of thermal cracking. organic matter, called kerogen, found in parent rocks.  Thermal cracking reactions take place in natural systems at temperatures between 80 and 200 C for times up to several million years.  Since these reactions can not be reproduced under the same conditions in the laboratory, it is necessary to carry out experiments at higher temperatures (300-600 ° C.) and for reasonable times (a few minutes to a few hours).  For each of the reactions considered, the degradation rates observed at different temperatures in the laboratory make it possible to define laws of variation as a function of time and temperature, and by extrapolation to evaluate the rates of these same reactions in natural systems.  Kerogen is a complex mixture of very high molecular weight macromolecules and is insoluble in common organic solvents.  It is possible to study its thermal cracking either in open reactors (Rock Eval technique) or in closed reactors (Horsfield et al. , 1989, Behar et al. 1989) or in closed reactors in the presence of water (Lewan et al. 1979; Lewan 1993).  Although involving physicochemical mechanisms of extreme complexity, the thermal cracking of kerogen obeys globally the principles of chemical kinetics.  The combined effects of time and temperature on the rate of transformation of kerogen into hydrocarbons have been demonstrated for a long time.  Experimentally first, with the pioneering work of the 1930s showing that the formation of oil from kerogen is all the faster as the temperature is high.  These studies have also highlighted the existence of a first-order relationship between the amount of hydrocarbons formed and their production rate.  It was not until much later in the 1960s and 1970s that these principles, issued 30 years earlier, were validated by observations.  Inspired by both the reactivity models of polymers and the approaches developed by German coalmakers in the late 1940s, the first models of primary cracking in oil parent rocks appeared in the 1960s.  Several approaches for the thermal conversion of kerogen to oil and gas have been developed and described in the literature.  These models can be grouped according to two kinds of reaction schemes: - The models with consecutive reactions (a): the formation of hydrocarbons in the source rocks does not result from the direct decomposition of the kerogen, but from a series of successive transformations transforming the kerogen in a viscous, thermally labile phase (called, according to the authors, either mesophase, bitumen or NSO), 2906481 7 which in turn decomposes into oil and gas (Tissot, 1969).  Each reaction is assumed to be mono-reactive, of order 1, and the rate constants are given by the Arrhenius law.  - Models with parallel reactions (b): Here the petroleum potential of a source rock is described by means of independent competitive reactions of order 1, whose speed constants are provided by the law of Arrhenius.  The reactions are each characterized by a specific activation energy, fixed in advance, a pre-exponential factor (the same for all reactions), and a fraction of the petroleum potential.  These fractions, corresponding to the contribution of each reaction to the total petroleum potential, are defined according to the activation energies, either independently of each other by means of a discrete distribution (Ungerer and Pelet, 1987), or constrained by means of a continuous function.  In all cases, the kinetic and stoichiometric parameters associated with the cracking reactions are usually calibrated using pyrolysis experiments carried out at high temperature (300-700 C) for times ranging from a few minutes to a few weeks.  The empirical models thus obtained are only simplistic representations of the kerogen oil balance as a function of time and temperature.  Extrapolated at low temperature, they nonetheless make it possible to estimate the geological period during which hydrocarbons were formed in a source rock.  The application of these kinetic models in numerical simulation of sedimentary basins requires precise and geologically realistic parameterization.  However, it has been observed that depending on the manner in which the pyrolysis experiments are carried out in the laboratory (open medium, closed medium, with or without the addition of water), the kinetic parameter values obtained from the same kerogen are very variables.  This is true regardless of the model (a) or (b) assumed, that is to say that each kinetic model can only represent the dataset from which it was calibrated.  This finding leads to the conclusion that neither of the two approaches actually satisfactorily models the conversion of kerogen to hydrocarbons, the experimental differences not being elucidated by the proposed chemical mechanisms.  Irrespective of the pyrolysis system, the pyrolysis products obtained during thermal cracking of kerogen include both hydrocarbon and non-hydrocarbon gases, saturated and aromatic hydrocarbons and organic compounds soluble in organic solvents and which contain oxygen, nitrogen and sulfur.  All of these products are generally called "NSO compounds".  They are of high molecular weight.  The main difficulty in studying the thermal cracking of kerogen is that the chemical composition of the kerogen or reagent is not known.  Only global analyzes and chemical or thermal degradation techniques make it possible to obtain structural information without having access to the identification of the constituent molecules of the kerogen.  Thus, the most commonly used approach is to follow the nature of the products formed and to make a mass balance between the residual reagent and the mass of the products.  A second difficulty is to link the reaction links between the nature of the products formed and the starting reagent; some products in fact, which can in turn undergo thermal cracking and generate new constituents (secondary cracking).  Finally, a third difficulty is the implementation of various analytical protocols appropriate to the characterization of the products formed.  Thus, the method according to the invention proposes, on the one hand, a thermal cracking model of at least one hydrocarbon, in particular oils, which can be used as a secondary cracking model making it possible to solve the aforementioned problems. .  The invention thus provides a kinetic scheme of thermal cracking of petroleum products comprising a limited number of global chemical classes and wherein the determination of overall kinetic parameters is constrained by those obtained on model compounds.  The method according to the invention The invention relates to a method for modeling the thermal cracking of at least one hydrocarbon, in which: a- at least the following chemical classes are individualized: • Gas fraction: H2S, C1, C2, C3 , C4 • Fraction C14_: C14- sat, C14_alkyl, 014_methyl, BTXN 2906481 9 • Fraction C14 +: C14 + sat, C14 + Aro-1, 2, 3 • NSOs • Solid fraction: prechar, char 5 b- define a reaction scheme for the cracking of at least one hydrocarbon, in which it is required that each reagent be decomposed into gaseous fraction, fraction C14-, fraction C14 + and solid fraction according to the following table: class fractional gas fraction C14- fraction C14 + fraction solid chemical C14 - alkyl - * Cl C2 C3 C4 BTXN alkyl Aro-3 C14-methyl - + C1 BTXN Aro-3 C14- Sat Cl C2 C3 C4 methyl Aro-2 C14 + Sat -> C1 C2 C3 C4 Sat-alkyl methyl Aro-2 C14 + Aro1 -> H2S C1 C2 C3 C4 Sat- alkyl methyl Sat + Aro-2 prechar C14 + Aro-2 - + C1 Aro-3 prechar C14 + Aro-3 C1 prechar NSOs H2S C1 C2 C3 C4 Sat-alkyl methyl Sat + Aro-1 prechar prechar -> C1 char 10 and in which the fraction C14- contains hydrocarbons between 6 and 14 carbon atoms, saturated, denoted Sat-, aromatics of benzene type, toluene, m-, p-, o-xylene, naphthalene and denoted BTXN, alkylated aromatics, denoted alkyl, methylated aromatics, denoted methyl; and wherein the C14 + moiety comprises hydrocarbons having more than 14 saturated carbon atoms, denoted Sat +, and aromatics denoted Aro-1 to Aro-2.  Preferably, a kinetic scheme is defined by determining the kinetic parameters and stoichiometric coefficients associated with said reaction scheme, by carrying out the following steps: c- closed pyrolysis experiments are carried out in order to monitor the productions and the disappearances of the classes chemicals at different temperatures and to ensure the quality of mass balances; D) determining productions and disappearances of the chemical classes at said temperatures by means of a simulation based on said reaction scheme according to steps a) and b); and e) said kinetic parameters and said stoichiometric coefficients are determined by means of a numerical inversion in which the difference between said productions and said disappearances simulated in step d) and said productions and said disappearances resulting from the pyrolyses are minimized; in step c).  Advantageously, a numerical simulator solving speed laws 10 of said reactions of said kinetic scheme as a function of time and temperature is used.  Advantageously, said cracking reactions are characterized by activation energy distributions, EEa, EEb, EEf, EEg, and by activation energies, Ec, Ed, Ee, Eh, E, as well as by stoichiometric coefficients, A'1 to A'6, B'1 to B'6, C'1 to C'3, D'1 and D'2, E1 and E2, F1 to F3, G1 to G3, H1 at H3 and I1 to 13, according to the following reaction kinetic scheme: NSOs EEa C14 + Aro-1 EEb C14 + Aro-2 Ec Ed C14 + Aro-3 Ee prechar C14 + Sat EEf C14_ Sat EE9 • C14 alkyl aro Eh C14 + methyl aro E 'A '1 no HC gas + A'2 HC + A'3 C14.  + A'4 C14 + sat + A'5 C14 + Aro-1 + A'6 prechar B'1 no HC gas + B'2 HC + B'3 C14_ + B'4 C14 + sat + B'5 C14 + Aro-2 + B'6 prechar C'1 C1 + C'2 C14 + Aro-3 + C'3 prechar Of 1 C1 + Of 2 prechar E1 C1 + E2 F1 car HC + F2 C14.  + F3 C14 + Aro-2 G1 HC + G2 C14_ + G3 C14 + Aro-2 H1 HC + H2 C14.  + H3 C14 + Aro-3 I1 C1 + 12 C14_ + 13 C14 + Aro-3 and in which no HC gas represents non-hydrocarbon gases and HC represents hydrocarbon gases.  In a preferred embodiment, a reduction in the size of the reaction scheme is performed according to the conditions required by a field of application, by reducing the number of chemical classes by grouping said chemical classes.  Advantageously, the method according to the invention is applied to the modeling of the secondary cracking of the products resulting from the thermal decomposition of kerogen in the source rock.  Brief Description of Figures 10 - Figure 1 shows the approach taken to obtain the Iumpé reaction scheme for cracking oils or secondary cracking in the tank.  FIG. 2 represents the approach adopted to propose a reaction scheme for primary and secondary cracking of the kerogen according to the invention.  FIG. 3 represents the successive and parallel cracking reactions of the primary and secondary cracking reaction scheme according to the invention.  FIGS. 4A to 4C show kinetic TR and natural TR abacuses for the four initial kerogens studied.  FIG. 5 represents the successive and parallel cracking reactions of the hydrocarbon thermal cracking reaction scheme according to the invention.  Detailed Description of the Hydrocarbon Cracking Method The kinetic hydrocarbon cracking schemes developed from laboratory experiments under high temperature conditions (generally above 250 C in practice) allow kinetic parameters to be determined.  These are used to determine the thermal reactivities under natural conditions, that is to say below 250 C.  Thus, it is possible, according to the thermal reactivity found for the different chemical classes, to make groupings between certain classes and thus to reduce the complexity of the initial kinetic schemes.  This grouping technique is classically called Jumping.  This grouping makes it possible to regenerate a simpler kinetic model, which can be used particularly in models of sedimentary petroleum systems.  The number of chemical classes of the thermal cracking model is indeed a strongly limiting parameter for the calculation times of pond simulators.  However, lumping must meet two requirements: to limit precision losses on the prediction of overall hydrocarbon cracking rates (the grouped model must be equivalent to the complete model for the prediction of hydrocarbon cracking windows); - after grouping, to obtain chemical classes having a business interest: integrity of the calculation of the thermodynamic properties of the total hydrocarbon fluid, integrity of the notions of oil (liquid hydrocarbons) and gases (gaseous hydrocarbons).  This double constraint implies the preservation of certain classes and reactions, in particular the cracking of heavy products.  The other classes can be grouped either by bubble points (grouping preserving the calculation of the thermodynamic properties), or by chemical structure and thermal reactivity (grouping preserving the calculation of the cracking windows).  This kinetic cracking model comprises 15 classes whose elemental composition is given in Table 4: Fluid with sulfur Fluid without sulfur Class CHS Total CH Total H2S 5.88 94.12 100.00 C1 75.00 25.00 100 , 00 C2 80.00 20.00 100.00 C3 81.82 18.18 100.00 C4 82.76 17.24 100.00 C6-C14 sat 84.40 15.60 100.00 BTXN 91.03 8 , 97 100.00 C14_alkyl 89.45 10.55 100.00 C14_ methyl 90.43 9.57 100.00 C14 + Sat 85.07 14.93 100.00 C14 + Arc-1 84.37 9.94 5, 69 100.00 89.46 10.54 100.00 C14 + Aro-2 85.06 6.94 8.00 100.00 92.46 7.54 100.00 C14 + Aro-3 85.37 6.38 8, 25 100, 00 93.04 6.96 100.00 NSOs 84.00 9.50 6.50 100.00 89.84 10.16 100.00 prechar 86.15 4.98 8.87 100.00 94 54 5.46 100.00 tank 86.74 3.93 9.33 100.00 95, 67 4.33 100.00 Table 4: list and elemental composition of the classes included in the kinetic model 20 The kinetic scheme is given in Table 5: reactions can be represented by activation energy distributions with a factor single frequency be mono energetic.  The stable classes are H2S, C1, C2, C3, C4, BTXN and char.  2906481 13 Class Gas fraction Fraction C14- Fraction C14, solid fraction EP log A chemical H2S C, C, C3 C4 Sat BTXN alkylmethyl Sat Aro-1 Aro-2 Aro-3 prechar char Total% C14_ alkyl aro 10.5 4.7 1.7 1.6 10.0 25, 7 45.8 100.0 56.0 100.0 13.1 methyl aro 10.9 50.6 38.5 100.0 55.0 100.0 11, 7 C, 4 Sat 4.0 20.0 23.0 24.0 22.0 7.0 100.0 70.5 73.0 17.8 76.0 27.0 17.8 C14, Sat 4.0 7 , 0 9.0 9.0 50.0 4.0 6.0 11.0 100.0 67.5 60.0 17.8 70.5 40.0 17.8 C 14, Am-1 1.8 2.5 1.6 1.7 1.9 7.0 1.6 0.4 18.0 48.0 15.5 100.0 52.0 80.0 13.3 54.0 20.0 13, 3 C, 4, Aro-2 3.0 70.0 27.0 100.0 49.0 100.0 10.8 C14, Aro-3 7.1 92.9 100.0 54.3 100.0 12 , 0 NSOs 0.8 2.5 1.3 1.3 1.3 10.0 3.5 0.8 9.0 35.0 34.5 100.0 52.0 40.0 13.1 56, 0 55.0 13.1 58.0 5.0 13.1 prechar 5.0 95.0 100.0 56.0 100.0 12.4 Table 5: Kinetic diagram for thermal cracking of petroleum fluid 5 has been tested on laboratory experiments carried out on a natural petroleum fluid.  From this kinetic scheme, a second scheme has been proposed which groups together certain chemical families.  The corresponding kinetic reaction scheme is described in FIG.  The grouping of constituents and reactions in order to reduce the size of a reaction scheme is a common practice in reaction chemistry, more particularly in radical kinetics.  Various mathematical techniques have been developed for this purpose, depending on the degree of reduction and the nature of the desired clustering (generic, reactional grouping, etc.). ).  In general, the purpose of grouping is to simplify the implementation of the kinetic model.  Thus, usually the kinetic schemes are calibrated and grouped for thermal conditions and durations corresponding to the field of application.  In the specific case of predicting oil reactivity, it is not possible to calibrate and group the model at the temperatures and durations observed in nature.  An originality of the method proposed here for the cracking of hydrocarbons, and in particular oils, therefore consists in: calibrating a complex reaction scheme under laboratory conditions (high temperature, short duration); - Then perform a reduction of the scheme for a restricted area of application, 2906481 14 different from the calibration conditions: for example, in the case of an application in basin modeling, the chosen domain combines low temperature (geothermal gradient) and long term (several million years).  This strategy is carried out by means of a numerical simulator of reaction schemes, calculating the rates of cracking reactions at both high and low temperature.  The analysis of simulated data at low temperature, for each class of the complex scheme, makes it possible to select the classes to be grouped (according to their reactivities, and / or their molecular weight).  Then, the low temperature pooled compositions allow to rewrite a simplified kinetic scheme extracted from the reactions of the original kinetic complex model.  The overall strategy is summarized in Figure 1, in which: CD Experimental Domain AD Application Domain 15 ED Experimental Data CS Complex Kinetic Scheme (Experimental Domain) S Simulation under SD Application Domain Conditions Simulated Data in the application conditions L Grouping ("Lumping") 20 RS Reduced kinetic scheme (field of application) According to this approach, three examples of lumping according to the invention are described below: reduction 1, 2 and 3.  The new chemical classes thus obtained and the new cracking parameters are summarized in Tables 6 and 7.  Reduction 3 proposes a scheme with 8 classes, but we would not depart from the scope of the invention by performing a grouping of classes so as to obtain a lower class number.  2906481 15 Type of initial model reduction 1 reduction 2 reduction 3 List of classes H2S H2S H2S chemical H2S C1 C1 Cil C1-C4 C2 C2 C2-C4 C14-C3 C3-C4 C14-C14 + Sat C4 C14-C14 + Sat C14 + Aro C14_ Sat C14 + Sat C14 + Aro NSOs BTXN C14 + Aro NSOs prechar C14_ alkyl aro NSOs prechar tank C14_methyl aro prechar tank C14 + Sat tank C14 + Aro1 C14 + Aro-2 C14 + Aro-3 NSOs prechar tank Number of classes 16 10 9 8 Table 6: possibilities of reduced diagrams for cracking petroleum fluids.  This reduced scheme is given in Table 7 and the corresponding elementary compositions in Table 8.  Gas class C14_ C14 + Solid E P log A chemical H2S C1 C2 C3-C4 total Sat Aro NSOs prechar Total 0/0 C14_ 6. 0 20. 0 48. 0 26. 0 100. 0 70. 2 32. 0 17. 8 6. 0 20. 0 48. 0 26. 0 100. 0 72. 6 34. 0 17. 8 12. 0 5. 0 4. 5 78. 6,100. 0 56. 6 14. 0 13.  1 18. 4 81. 6,100. 0 53. 6 10. 0 10. 8,100. 0 --------------- 100. 0 75. 0 10. 0 10. 8 C14. 1.  Sat 4. 0 7. 0 18. 0 64. 0 7. 0 100. 0 67. 5 60. 0 17. 8 3. 0 7. 0 18. 0 66. 0 6. 0 100. 0 70. 4 40. 0 17. 8 C14 + Aro 5. 0 5. 8 4. 0 9. 0 21. 44. 5 10. 2,100. 0 52. 1 40. 0 13. 3 5. 5 94. 5,100. 0 48. 5 20. 0 10. 8 6. 0 94. 0 100. 0 51. 0 20. 0 10.  8 7. 1 92. 9,100. 0 55. 8 20. 0 12. 4 NSOs 2. 7 1. 4 2. 6 14. 3 9. 0 35. 0 35. 0 100. 0 52. 0 40. 0 13. 1 56. 0 55. 0 13. 1 58. 0 5. 0 13. 1 Prechar 5. 0 95. 0 100. 0 56. 0 100. 0 12. Table 7: Kinetic Parameters for Reduced Schemes.  10 2906481 16 'Sulfur petroleum fluids Sulfur petroleum fluids 1 Chemical class C H S Total C H Total C14-85. 26 14. 74 0. 00 100. 00 014+ Sat 85. 07 14. 93 0. 00 100. 00 C14 + Aro 84. 85 8. 03 7. 13,100. 00 91. 36 8. 64,100. 00 NSOs 84. 00 9. 50 6. 50 100. 00 89. 84 10. 16,100. 00 prechar 86. 4. 98 8. 87,100. 00 94. 54 5. 46,100. 00 tank 86. 74 3. 93 9. 33,100. 00 95. 67 4. 33,100. Table 8: Elemental Composition of Chemical Classes for Reduced Schemes.  Application as a model for secondary cracking of organic matter in parent rocks The invention can be applied also to the development of kinetic patterns of organic matter cracking in source rocks that include not only kerogen cracking (primary cracking). ), but also that of NSO compounds 10 generated from this kerogen (secondary cracking).  Thus the fluid expelled from the source rock is the result of the cracking of kerogen and that of NSO compounds.  This approach therefore corresponds to a coupling between the two concepts described above and schematized in FIG. 2 which describes the approach adopted to propose a reaction scheme for primary and secondary cracking of kerogen using the secondary cracking model according to the invention in which: K Kerogen (Type I, II, III, II) B Intermediate heavy product (Bitumen, Mesophase, NSO, etc.). ) HC ^ Hydrocarbons Xi Stoichiometric coefficients.  An original approach of the present invention is to: - establish mass balances and complete atomic balances on the elements present in the initial kerogen (type I, II, III and II kerogens), that is to say the carbon, hydrogen, oxygen and sulfur on all pyrolysis products (gas, liquid and solid).  - to give a detailed description of the pyrolysis products in: • non-hydrocarbon gases: CO2, H2S and H2O • hydrocarbons C, C2, C3 and C4i 2906481 17 • liquid hydrocarbons: 06-014 methyl aromatics, C6-014 alkyl aromatics , BTXN, C6-C14 saturated, C14 + saturated, C14 + aromatic 1, C14 + aromatic 2, C14 + aromatic 3.  • compounds NSOs 1 and NSOs 2 • solid residues: kerogen 1, kerogen 2, kerogen 3, kerogen 4 and prechar and char.  The choice of these classes and the determination of their proportion in the pyrolysis product mixture results from the parameter acquisition method described above.  - The detailed monitoring of these different classes according to the conversion of kerogen allows to develop a coherent kinetic scheme that includes parallel and successive reactions.  These reactions can be described by activation energy distributions and mono energetic reactions (Figure 3).  The nomenclature of the chemical compounds is described at the beginning of the description.  The overall kinetic scheme includes the secondary cracking reactions of kerogen cracking products such as NSO compounds 1 and 2.  Indeed, as previously mentioned, NSOs 1 and 2 are thermally unstable under laboratory conditions and in geological conditions: also a cracking reaction of these compounds has been introduced and can be modeled by the reaction kinetic cracking scheme of hydrocarbon according to the invention.  On the other hand, aromatic C14 + 1 are also thermally unstable and undergo secondary cracking and generate aromatic C14 + 2 which in turn will produce aromatic C14 + 3.  Two solid phases are indicated in this kinetic scheme: prechar and kerogen 2.  Kerogen 2 is the portion of kerogen 1 that has not been converted and the prechar is the solid residue formed during the cracking of NSO compounds.  An earlier study on the thermal cracking of kerogen 2 (Lorant, 1999, Lorant and Behar, 2000) has made it possible to propose a specific kinetic scheme in two successive reactions.  From this integrated scheme, it is possible to define relative proportions between mobile and immobile compounds for certain chemical families, in particular for the aromatic C14 + 1 and the NSOs 1 and NSOs 2 compounds.  Typically NSOs 1 compounds of very high molecular weight can be considered as predominantly immobile in source rocks.  For weight NSOs 2 compounds, a larger portion is mobile.  The relative proportions of immobile and mobile compounds for these 2 families can be adjusted on a case-by-case basis.  Thus the use of this new kinetic secondary cracking scheme allows, for the first time, to account not only for the nature of the liquid, gaseous and solid products generated during the cracking of kerogen under laboratory conditions and under the conditions but also the composition of the fluids effectively expelled from the source rocks.  An example of a kinetic scheme coupling a primary cracking model of kerogen and the secondary cracking model according to the invention is summarized in Table 1: initial reactive kinetic scheme mobile products products E immobile kcallmol primary cracking kerogen 1 H20, H2S , CO2 C14 + Aro- im distribution Cl, C2, C3, C4 NSOs ims C14_ sat, C14_ alkyl, C14_ methyl kerogen 2 C14 + sat, C14 + Arc-1m, NSOs m -------------- -------------------------------------------------- ------------------------------------- kerogen 2 kerogen 3 C1 kerogen 3 mono C1 kerogen 4 mono cracking NSOs im H20, H2S, CO2 precharging secondary distribution Cl, C2, C3, C4 C14_ sat, C14_ alkyl, C14_ methyl C14 + sat, C14 + Aro-1, NSOs m --------------- -------------------------------------------------- ------------------------------------ C14 + Aro-1 im H2S distribution Cl, C2, C3, C4 C14 + Aro-2 im C14_ sat, C14_alkyl, C14_methyl C14 + Aro-2 mono C14 + sat, C14 + Aro-2 C14 + A ro-3 C1 C14 + Aro-3 im C1 prechar prechar prechar C1 monocarbon Table 1: Kinetic scheme for the cracking of kerogen and description of the composition of the products formed as well as the secondary cracking reactions of immobile products.  The kinetic scheme obtained makes it possible to explain the experimental results obtained at the same time during simulations in an open environment, closed without water and closed with water.  In the particular case of simulations of thermal cracking in open medium, not all NSO compounds are removed from the pyrolysis chamber, given their high molecular weight.  Thus, some of them, once generated, remain in the pyrolysis chamber and undergo thermal cracking at the same time as the initial kerogen.  Consequently, the pyrolysis products recovered in an open medium are the sum of those from kerogen and from a part of the NSO compounds.  Under these conditions, the cracking reactions of kerogen 1 and those of compounds NSOs 1 can be combined into a single reaction.  2906481 20 Class Type Gas fraction C.  C, 4.  mobile C ,, immobile Solid fraction Total EP log A chemical kerogen H20 H2S CO2 C, C2 33-C4 sat aro sot aro nsos m aro 1 aro 2 aro 3 nso im kero 2 kero 3 kero 4 prechar% Type I kero 1 3 , 9 1.0 2.2 1.1 1.2 2.4 5.3 1.5 6.4 1.8 2.9 3496 39.9 100.0 48.0 0.9 14.75 Total 3 , 6 5.3 1.5 6.4 5.4 29.7 3.6 26.8 96.4 100.0 50.0 0, 8 14.75 kero 2 3.9 1.0 2.2 1 , 1 1.2 2.4 6.0 7.7 12.1 64.2 6 __-_ 100.0 52.0 6.0 14.75 kero 3 0.9 1.2 2.5 39.9 100.0 54.0 13.0 14.75 NSOs im 5.5 100.0

  56.0 74.2 14.75 Total__ 58.0 5.1 14.75 Aro 1 lm 100 0 Total 58.8 100 13.76 546 1001151 48.0 0.9 14.75 50.0 0.8 14 , 75 52.0 6.0 14.75 54.0 13.0 14.75 56.0 74.2 14.75 58.0 5.1 14.75 1000 48.0 6.0 13.28 50, 0 20.0 13.28 52.0 63.0 13.28 54.0 11.0 13.28 100.0 Type II kero 1 5.0 2.5 3.8 1, 1 0.6 1.2 2.2 0.9 2.5 2.0 2.1 4.2 19.7 52.2 100.0 44.0 1.4 13.13 Total 3.6 2.2 0.9 2.5 6 , 2 21.8 96.4 100.0 46.0 3.9 13.13 kero 2 34-Y-96.6 10010 48.0 20.1 13.13 kero3 5.0 2.5 3, 8 1.1 0.6 1.2 52.2 100.0 50.0 63.7 13.13 NSOs im 52.0 8.9 13.13 54.0 2.0 13.13 1000 58.8 100 13.76 5.46 _-_ 100 11, 51 44.0 1.4 13.13 46.0 3.9 13.13 48.0 20.1 13.13 50.0 63.7 13.13 52.0 8 , 9 13.13 54.0 2.0 13.13 Total ---- '-' '.

1000 Aro 1 lm 6.7 0.9 1.1 2.3 5.6 7.2 11.3 59.9 5.1 100.0 48.0 6.0 13.28 50.0 20.0 13 , 28 52.0 63.0 13.28 54.0 11.0 13.28 Total _ 100.0 Type III kero 1 16.0 11.0 1.1 0.4 0.5 0.8 0.6 1.7 0.4 0.5 0.9 4.2 61.9 100.0 44.0 0.3 13.61 46.0 5.5 13.61 48.0 14.0 13.61 50 0 27.3 13.61 52.0 36.9 13.61 54.0 12.0 13.61 56.0 4.0 13.13 Total 100 0 kero 2 2.8 97.2 100.0 62, 2 100 14.47 kernel 3 ----- 98.0 100_0 569100 10.74 NSOs lm 16.0 11.0 1.1 0 , 4 0.5 0.8 0.6 1.7 1.3 4.7 61.9 100.0 44.0 0.3 13.61 46.0 5.5 13.61 48.0 14.0 13.61 50.0 27.3 13.61 52.0 36.9 13.61 54.0 12.0 13.61 56.0 4.0 13.13 Total 1000 Aro 1 lm 0.9 1.2 2.5 6.0 7.7 12.1 64.2 5.5 100.0 48.0 6.0 13.28 50.0 20.0 13.28 52.0 63.0 13.28 54, 0 11.0 13.28 _ Total 100.0 Type II-S kero 1 5.4 5.0 2, 5 1.2 0.7 1.4 1.6 2.2 1.2 1.6 3, 2 25.2 48.8 100.0 44.0 3.8 13.64 46.0 13.1 13.64 48.0 25.3 13.64 50.0 29.5 13.64 52.0 17 , 1 13.64 54.0 8.3 13.64 56.0 2.9 13.64 Total 100.0 kero 2 3.6 96.4 100.0 58.8 100 13.76 kero 3 • 3r4 _ _ • ---- ~~~~~~ 96 6 -_- 100 54 6 100 11 51 NSOs im 5,4 5,0 2,5 1,2 0,7 1,4 1,6 2,2 1,2 4, 8 25.2 48.8 100.0 44.0 3.8 13.64 46.0 13.1 13.64 48.0 25.3 13.64 50.0 29.5 13.64 52.0 17 , 1 13.64 54.0 8.3 13.64 56.0 29 13.64 Aro 1 im 6.7 0.9 1.1 2.3 5.6 7.2 11.3 59.9 5, 1 100.0 48.0 6.0 13.28 50.0 20.0 13.28 52.0 63.0 13.28 54.0 11.0 13.28 Total _ 100.0 Type I NSOs 0, 8 2.5 1.3 2.6 10.0 4.3 9.0 35.0 34.5 100.0 52.0 50.0 13.50 Type II 54.0 40.0 13.50 Type III 56.0 7.0 13.50 Il-S type 58.0 3.0 13.50 Total 100.0 2906481 21 Table 2: Kinetic pattern and parameters for the 4 main types of organic matter in sedimentary basins Compositions The elemental classes of the various kerogens, NSOs and aromatic C14 + fractions are given in Table 3. Class type CHNOS Total 1 HIC OIC chemical kerogen Organic elemental composition (%) Atomic ratio kerogen 1 78.7 9.6 7.7 3.3 0.6 100.0 1.460 0.032 kerogen 2 85.5 4.4 7 .1 2.7 0.3 100.0 0.611 0.024 kerogen 3 85.7 3.3 7.7 3.0 0.4 100.0 0.459 0.026 kerogen 4 85.9 2.2 8.3 3.2 0.4 100.0 0.302 0.028 kerogen 1 76.1 7.7 10. 6 1.8 3.9 100.0 1.212 0.017 kerogen 2 84.7 4.6 5.8 1.6 3.2 100.0 0.658 0.014 kerogen 3 85.0 3.4 6.4 1.7 3.5 100.0 0.481 0.015 kerogen 4 85.2 2.1 7.0 1.9 3.9 100.0 0.297 0.017 III kerogen 1 66.0 5.8 26.0 1.3 0.9 100.0 1.047 0.015 kerogen 2 81.9 4.4 12.0 1.1 0.6 100.0 0.638 0.010 kerogen 3 81.8 3.7 12.7 1.2 0.6 100.0 0.540 0.011 kerogen 4 81.7 3.2 13.2 1.3 0.6 100.0 0.463 0.012 Il-S kerogen 1 69.8 7.3 9.4 2.7 10.8 100. 0 1.247 0.029 kerogen 2 80.9 4.5 4.8 4.1 5.7 100.0 0.666 0.038 kerogen 3 80.8 3.4 5.2 4.5 6.1 100.0 0.510 0.041 kerogen 4 80.6 2.3 5.6 4.8 6.6 100.0 0.348 0.045 NSO im 84.5 11.7 2.7 0.9 0.3 100.0 1.657 0.008 Aro 1 im 87.7 11.2 1.1 100.0 1.530 Aro 2 im 92.5 7.5 100.0 0.979 Aro 3 im 93.0 7.0 100.0 0.898 Il NSO im 79.1 8.4 4.8 1.4 6.2 100.0 1.276 0.013 Aro 1 im 84. 6 8.9 6.5 100.0 1.268 Aro 2 im 85.1 6.9 8.0 100.0 0.979 Aro 3 im 85.4 6.4 8.3 100.0 0.897 III NSO im 80.6 7.3 10.0 0.3 1.9 100.0 1.086 0.003 Aro 1 im 90.0 10.0 1.333 Aro 2 im 92.5 7.5 0.979 Aro 3 im 93.0 7.0 0.898 11-S NSO im 78.1 8.3 4.3 1.6 7.7 100.0 1.282 0.016 Aro 1 im 84.6 8.9 6.5 1.268 Aro 2 im 85.1 6.9 8.0 0.979 Aro 3 im 85.4 6.4 8.3 0.897 Table 3: Basic compositions of different kerogens and related products.

From the kinetic schemes proposed, it is possible to calculate a conversion rate identical to that defined by the Rock Eval technique (EP-0767375). From these calculations, charts for each type of kerogen can be proposed to determine the values of this rate of transformation on natural samples of varied thermal maturity. To do this, the following steps are carried out.

The transformation rate of the kerogen is determined on an immature sample by pyrolysis of Rock Eval type. The latter makes it possible to measure the rate of production of the hydrocarbons during thermal cracking of the kerogen. When the measurement of the peak of hydrocarbon production is made on an immature sample, its time integral represents the maximum value of the petroleum potential of the sample, denoted S20, since the sample has not yet undergone thermal maturation. The conversion rate (TR) of kerogen is therefore defined as follows: TR Kinetic = hydrocarbons generated / S2o In sedimentary basins, it is necessary to determine the rate of transformation of kerogens in order either to calibrate the thermal history or to predict whether petroleum fluids have actually been generated. For this it has been proposed by Espitalié et al. (1977), to use the following equation: TR Natural = (S2o ù S2) / S2o or, if one takes into account the carbon contents of the samples: TR = ((S2 / Co) ù (S2 / C)) / (S2JCa)) With: S2: residual petroleum potential of a sample (in mg per g of rock) 15 S2o: initial petroleum potential of an immature sample (in mg per g of immature rock) C: content in organic carbon of a sample (in g of C per g of rock) Co: organic carbon content of an immature sample (in g of C per g of immature rock) 20 When the samples have already undergone thermal maturation, kerogen 2 is produced as indicated in the kinetic scheme (Figure 3). Consequently, the measured S2 comes from the residual S2 in the initial kerogen and from the S2 generated from the kerogen 2. Also, thanks to the proposed kinetic scheme, it is possible to quantify for any transformation of the initial kerogen the respective amounts of residual initial kerogen and that of kerogen 2 generated. Knowing the amount of residual initial kerogen, it is possible to predict the value of the peak S2, namely: S2sample = S2o x% of residual initial kerogen From this equation, the natural TR can thus be determined, and it is then possible to to develop kinetic and natural TR TR charts for any immature sample. By measuring the Natural TR, the kinetic TR is deduced. By way of example, such charts are shown in FIGS. 4A to 4C for the four initial kerogens studied, kerogens of type I, II, III and II, respectively. NTR represents the natural TR and KTR represents the kinetic TR.

The cracking scheme of a kerogen can, for example, be used in the context of a basin simulation. It is indeed recognized that the process of formation of oil and gas in sedimentary basins is the result of a thermal cracking of organic matter (kerogen) present in the source rocks. To be perfectly predictive of the amount of hydrocarbons present in a reservoir rock as a result of the cracking started in a source rock, it is advantageous to associate with this scheme a kinetic scheme of the cracking of the oils as a secondary cracking model of the hydrocarbons. NSOS compounds.

Method of Parameter Acquisition This section describes the applicable methods for determining the parameters that may be used in the previously mentioned kinetic reaction schemes for cracking oils or for primary and secondary cracking of kerogen, as part of application of the method according to the invention to the modeling of the cracking of the organic matter of the source rock. Acquisition of Kinetic Parameters The kinetic patterns defined for studying and modeling the thermal cracking of petroleum fluids must be supplemented by the definition of their kinetic parameters and their stoichiometric coefficients. To date, the kinetic models used in digital simulators of sedimentary basins to represent the formation of oil in source rocks more or less correspond directly to a set of parallel, independent and first order thermal cracking reactions. kinetic parameters (activation energies, pre-exponential factors) and the stoichiometric coefficients associated with these reactions are calibrated using laboratory pyrolysis experiments on organic matter (kerogen) extracted from immature source rocks (Ungerer and Pelet, 1987).

The purpose of the pyrolysis experiments is to measure, under laboratory conditions, the formation rate of petroleum fluids as a function of temperature and time. Two kinds of experimental techniques can be used for this purpose: open-system pyrolysis and closed-system pyrolysis (with or without the addition of water). In the first case, the mobile effluents from the pyrolysis of kerogen are removed from the reaction medium as they are produced (either by means of a circulating gas or by vacuum suction). In the second case, the pyrolysis effluents accumulate in the reaction medium and can therefore undergo secondary cracking.

In general, the kinetic models for the thermal cracking of kerogen represent petroleum fluids (oil and gas) in a very simplistic way, in the form of a single constituent. In this case, non-compositional experimental techniques, which are quick to implement and only allow a partial mass balance (on the hydrocarbon products), are used to calibrate the kinetic parameters. Rock Eval and Pyromat open-system pyrolysers allow the acquisition of calibration data from non-compositional kerogen cracking models. Towards the end of the 1980s, so-called kinetic compositional models appeared, in which the oil and gas formed in the source rocks are represented by several constituents (classes of bubble points, structural classes, etc.).

To calibrate the speed parameters of these models, either open pyrolysis experiments or closed system pyrolyses are used. Whether compositional or not, the acquisition of pyrolysis data in the laboratory has at least the following two limitations. On the one hand, the compositional data obtained in an open system only allow a partial mass balance of kerogen cracking, based on the volatile hydrocarbon constituents only. For this reason, these data are applicable only to kinetic schemes whose reactions limit it to describe the conversion of kerogen to hydrocarbons, without taking into account the non-hydrocarbon components or the fate of the residual carbon solid mass. On the contrary, the experiments carried out in a closed system allow, in principle, a complete mass balance of the thermal conversion of the kerogen. Nevertheless, these experiments are expensive in terms of material, time and require a relatively large mass of kerogen. Consequently, these techniques are difficult to implement on a case-by-case basis, and the number of data produced from a kerogen sample generally makes it possible to develop only simple kinetic models, with a limited number of reactions and , therefore parameters to calibrate.

Thus, according to the invention, these parameters are calibrated by means of pyrolysis experiments coupled with digital inversion techniques. The experimental methodology according to the invention is a compromise between the open system approach and the closed system approach. Indeed, it makes it possible to fully calibrate the petroleum product cracking model, obtaining an equivalent result depending on whether the experimental data are obtained in an open system or in a closed system, or both at the same time. double mass balance and carbon, it allows to calibrate both the formation of hydrocarbon effluents, non-hydrocarbons, and the evolution of the solid fraction consists of a mixture of immature kerogen, mature kerogen and carbon residue.

Advantageously, the constraints associated with the following kinetic parameters are defined: the cracking reactions are assumed to be parallel, independent, of order 1 kinetics obeying the Arrhenius law: K = Ae R`T, where A is the kinetic constant (frequency factor), E the activation energy, T the temperature and R the perfect gas constant; - all reactions have the same frequency factor; the possible range of activation energies is chosen between 40 and 80 kcal / mole spaced 2 kcal / mole between 2 reactions. The method comprises the following steps: 1. Open and / or closed pyrolysis experiments are carried out; 2. the parameters are determined by digital inversion. Determination of parameters and coefficients of the kerogen cracking scheme -Determination of parameters E and A Open pyrolysis is carried out at different heating rates of the initial kerogen and only the production rate of peak S2 is measured which is defined as being the sum of all pyrolysis effluents with the exception of non-hydrocarbon gases (CO, CO2, H2, N2, H2S), water (H2O). By inversion we obtain the E and A by making the assumptions previously indicated. Cracking rates are obtained from open pyrolysis experiments carried out with a device called Rock Eval 6, described for example in EP-0-767-375. The kerogen charges used for each experiment are adjusted to obtain identical heights of the peak S2 between the different tests in order to ensure better reproducibility of the measurements and thus to obtain more accurate experimental results. The overall production rates of the pyrolysis effluents are measured at different heating rates: 2, 5, 10, 15 and 25 C / min from an isotherm at 200 C for 15 minutes and then a temperature rise to 700 C. Pyrolysis is carried out under a nitrogen flow of 100 ml / min. From the hypotheses described previously (cracking reactions assumed to be parallel, independent and of order 1, ...), each kinetic model can be calibrated by the adjustment of 23 parameters: a frequency factor, the 21 coefficients of activation energies, the petroleum potential of kerogen (S2p) [corresponding to the total amount of pyrolysis products generated by heating the sample to infinite temperature and time].

The overall kinetic parameters for describing the genesis rate of all the products contained in the peak S2 are adjusted by numerical inversion of the experimental data obtained with the Rock Eval 6. The numerical inversion consists of the determination of a set of values which locally minimize a quadratic error function (sum of squares of residuals between the hydrocarbon formation rates measured by the Rock Eval and those calculated by the kinetic model). Any constrained optimization algorithm (to ensure conservation of the mass) adapted to continuous quadratic functions can be used: Levenberg-Marquardt method, conjugate gradients, quasi-Newton, etc. Determination of Stoichiometric Coefficients A new pyrolysis is carried out for 100% conversion of the initial kerogen, and the pyrolysis effluents are recovered with an S 2 analyte to separate them into different chemical classes. The S2 analyzer is an apparatus derived from the Rock Eval 6 apparatus, also described in EP-0-767-375, which is equipped with a trap for recovering the liquid fraction of the previously defined peak S2. This gives us the stoichiometric coefficients for 100% conversion of kerogen. The resulting stoichiometric reaction is as follows: Kerogen = CO + CO2 + H2S + H2O + C1 + C2 + C3 + C4 + C6-C14 saturated + C6-C14 aromatic + C14 + saturated + C14 + aromatic + NSOs pentane + NSOs DCM + kerogen The stoichiometric coefficients are measured in several steps: 1) a pyrolysis at 25 ° C./min between 200 ° C. and 650 ° C. in order to draw up the following balance sheet: Mass of initial kerogen = x1 (CO) + x2 (CO2) + X3 (S2) + x4 (kerogen 2) The CO, CO2 and S2 peak gases are directly quantified by the Rock Eval 6 apparatus. The amount of kerogen 2 is determined from the carbon balance after determining the rate of carbon in the initial kerogen and knowing the estimated peak S2 carbon content of 83%. 2) a second pyrolysis at 25 ° C./min between 200 ° C. and 650 ° C. in order to draw up the following balance sheet: Fraction C6 + of the peak S2 = C6-C4 saturated + C6-C14 aromatic + C14 + saturated + C14 + aromatic + NSOs pentane + NSOs DCM 2906481 28 This pyrolysis is carried out with the S2 analyzer. 3) some closed pyrolysis points (annexed step) H2S from kerogen cracking alone, can not be determined during open pyrolysis due to the possible contribution of H2S from decomposition thermal pyrite often associated with kerogen. This pyrite indeed decomposes beyond 500 C under the conditions of pyrolysis performed with a Rock Eval type device. Also to measure this compound, pyrolyses in a closed environment are realized because it is possible to lower the temperature and increase the residence time. The conditions are chosen so as to obtain a degree of conversion, as determined in an open environment, of kerogen close to at least 90%. The H2S thus generated under these conditions is quantified as indicated previously. If in these experiments, mass balances are made, it is possible to calculate the amount of water for a conversion rate close to 100%. Otherwise it is possible to quantify the water yield by a pyrolysis experiment conducted between 200 and 650 C at 25 C / min with determination of water by a specific detector. 4) specific pyrolysis in an open medium for the compounds CI, C2, C3 and C4. These pyrolyses are carried out under vacuum at 25 C / min between 200 and 650 C with continuous drawing by a Toepler pump. The latter also makes it possible to recover quantitatively all the gases produced for molecular analysis by gas chromatography. However, methane can also be met by coupling the Rock Eval 6 with a specific infrared-type detector, for example. Finally, these hydrocarbon gases can also be quantified by a coupling between the Rock Eval 6 and a gas chromatograph. 25 - Verification of the balances It is verified that the sum of the hydrocarbon gases measured, added to the total quantity of the liquid fraction C6 + of the peak S2 is well coherent with the value of the peak S2 directly measured by the Rock Eval 6.

2906481 29 Determination of the parameters and coefficients of the oil cracking scheme For these parameters, it is necessary to carry out pyrolysis in a closed environment. The acquisition of kinetic parameters in a closed environment requires having a sufficient set of experiments to monitor the production and disappearance of the main chemical classes at different temperatures and to ensure the quality of the mass balances. For example, 25 experiments covering 3 temperatures are generally sufficient and the recovery rate of all the pyrolysis effluents is greater than or equal to 95%. This method was used for the acquisition of kinetic parameters for kerogens 2 and kerogens 3 and for all the kinetic parameters of the unstable liquid compounds in the temperature range selected for the experiments. Determination of E and A Parameters and Stoichiometric Coefficients Stoichiometric velocities and coefficients are determined numerically from the mass balances obtained in all experiments. By following the evolution of each class in terms of production and disappearance, it is possible to write a prior kinetic scheme that will serve as an initial step in the calculation of kinetic parameters. The calibration of the kinetic and stoichiometric parameters is carried out as follows. A numerical simulator is used to solve the speed laws of the chemical reactions of the kinetic pattern as a function of time and temperature. Simulations are made under experimental time and temperature conditions. The calculated data for all the chemical classes are compared with the corresponding measured data and the differences between the measured quantities and the predicted (residual) quantities are minimized by numerical inversion of a squared error function (defined as the sum of the square residuals). Any constrained optimization algorithm (to ensure conservation of the mass) adapted to continuous quadratic functions can be used: Levenberg-Marquardt method, conjugate gradients, quasi-Newton, etc. 2906481 - Balance Sheet Verification Knowing the elemental compositions of the starting petroleum products and of all the liquid and gaseous effluents, the mass of residual solid at 100% conversion and its elemental composition in C, H, O and S. In sum, the method according to the invention for determining kinetic parameters and stoichiometric coefficients associated with kinetic thermal cracking schemes of petroleum products makes it possible to determine such parameters consistent with both open system pyrolysis experiments. and in a closed system. In addition, based on a double mass and carbon balance, it allows to calibrate both the formation of hydrocarbon effluents, non-hydrocarbons, and the evolution of the solid fraction consisting of a mixture of immature kerogen, mature kerogen and residue. carbon.

A detailed example of an experimental protocol using the methodology is described below. For example, reference may be made to the following document: Behar, F., Leblond, C., St. Paul, C., 1989. Quantitative Analysis of Pyrolysis Effluents in Open and Closed Environments. Oil and gas science and technology 44, 387-411.

Example of an experimental protocol A - PYROLYSIS SYSTEMS A 1 - Closed Pyrolysis The samples are heated in a medium kept closed for the duration of the pyrolysis. The pyrolysis chamber is previously purged to remove all of the oxygen from the air. A first set of experiments is carried out in order to define the most appropriate temperature and time range to follow the conversion of the selected loads.

The experiments are carried out in closed reactors under an inert gas (for example: helium, nitrogen), with or without the addition of water. Two types of reactors are used: - isobaric reactors of low capacity (less than 5 ml): gold tubes of various sizes and welded at both ends are used in particular. Back pressure is imposed throughout the duration of the experiments in order to avoid the explosion of the tubes due to the internal pressure generated. The charge is generally between 30 mg and 1 gram. - Isochoric reactors of medium or large size (more than 5 ml): used for loads greater than one gram, these reactors consist of a hermetically sealed stainless steel capacity. Such pyrolysis systems are commercially available (Parr reactors). Gold tubes (isobaric reactors) are used to minimize interactions between reactors and the chemical reaction medium. Two tubes are heated at the same time: one will be devoted to the analysis of the gaseous compounds and the other to the balance of the liquid and solid compounds. The mass of the initial charge is determined by weighing between the empty tube and the solid tube before welding. The gold tubes are placed in an autoclave which contains a 2nd gold tube in which a thermocouple is placed in order to have the temperature closest to that which the charge to be pyrolyzed. The autoclaves are then placed in a chamber previously heated to the desired temperature. The pyrolysis times are chosen to minimize the influence of the rise in temperature. At the end of the pyrolysis, the autoclave containing the gold tube (s) is instantly immersed in water at ambient temperature in order to stop the cracking reactions as quickly as possible. In the case of isochoric reactors, an inert gas pressure is introduced at ambient temperature. The reactors are then placed in a chamber previously heated to the chosen temperature. At the end of the pyrolysis, they are cooled to ambient air. The pyrolysis conditions are isothermal conditions with varying residence times The heating conditions for kerogens depend on their chemical structure and their degree of maturity. For low-maturity kerogens, the temperature range is generally between 150 C and 375 C for durations of between 1 hour and 30 months. For more mature kerogens, the temperatures are between 350 and 550 C for equivalent residence times.

2906481 32 For all the experiments carried out on liquid products, the conditions are isothermal between 200 and 500 C: the choice is there also a function of the thermal reactivity of the studied products.

Open Pyrolysis The samples are heated in a pyrolysis chamber flushed with a gas stream such as Rock Eval pyrolysis. This pyrolysis makes it possible to determine the non-hydrocarbon gases CO and CO2 as well as all the gaseous or liquid products detected by a flame ionization detector or S2 peak (Patent No. EP-0-767-375 for the Rock Eval 6) . The tests are carried out in temperature programming between 2 and 25 C / minute under a nitrogen flow of 100 ml / minute. A second pyrolysis system is used to determine the composition of the liquid fraction of the S2 peak. This system is called S2 analyze. The liquid effluents are recovered in a trap cooled by liquid nitrogen.

The hydrocarbon gas fraction of the S2 peak can be assayed either by a Rock Eval coupling or by micro-gas chromatography or by other techniques such as the coupling between thermogravimetric analysis and infrared detection (TG / FTIR) or vacuum pyrolyses. open medium with quantitative recovery of the gases then analysis by gas chromatography.

20 B - ANALYTIC PROTOCOLS B - 1 Recovery and quantification of gases B - Quantification of gases in an open environment Pyrolysis Rock Eval is used to determine the non-hydrocarbon gases CO and CO2. The hydrocarbon gas fraction of the S2 peak can be assayed either by Rock Eval coupling or by micro-gas chromatography or by other techniques such as coupling between thermogravimetric analysis and infrared detection (TG / FTIR) or vacuum pyrolysis.

2906481 33 B û 1û b Quantification of gases in a closed environment For gold tube pyrolyses, the gold tube is pierced in a vacuum line equipped with a Toepler pump. The latter makes it possible to store in pre-calibrated volumes the gases generated, the total quantity of which can therefore be estimated. These gases are then completely transferred to an ampoule and then quantified by gas chromatography. Thus, the quantities recovered are expressed in absolute yield (%, mg / g or mg / gC) relative to the feedstock introduced for H2, CO, CO2, H2S, C1, C2, C3, n-C4 and i-C4. This quantitative assay makes it possible to calculate the C, H, O and S balance for the gaseous fraction. Depending on the type of closed reactor, the mode of recovery of the gases may be different. In the case of isochoric reactors (Parr type), a gas collection system by expansion in a previously evacuated container makes it possible to recover the gaseous fraction which is then analyzed by the same apparatus as that used for the gases recovered in the 15 gold tubes. B-2 Determination of the light fraction C6-014 B 2 - Open pyrolysis Using the S2 analyzer, the liquid effluents are trapped in the liquid nitrogen.

Once the liquid nitrogen has been removed, the trap is rinsed with n-pentane. All of the pentane stock solution is fractionated by liquid chromatography on a small column (Pasteur pipette size) filled with Florisil to retain the high molecular weight compounds. The eluate is then deposited on a second column filled with silica in order to separate 2 fractions: after a first elution with n-pentane, the solution contains all of the saturated hydrocarbons. The second elution using a npentane / dichloromethane mixture (85/15, v / v) makes it possible to recover the aromatic C6-C14 fraction. After adding an internal standard in each of the two solutions, the two solutions are injected into a gas chromatograph equipped with a capillary column. The total area (peaks + unresolved background) is integrated from the C6 hydrocarbon to C14 hydrocarbon. This surface expressed in pvolts is then converted into a mass knowing the concentration and the detected surface of the internal standard. It should be noted that in this protocol hydrocarbons containing 5 carbon atoms are not metered. The quantities are then reduced to the initial charge just like the gas dosage. As regards the elementary compositions, respective average values of 15.6% in H and 84.4% in C are attributed for the saturated fraction. For the aromatic fraction, average values of 9.0% in H and 91.0% in C. B 2/2 b Closed Pyrolysis The second gold tube is pierced in a piercer equipped with a needle and filled with n-pentane. The contents of the piercer are then transferred to a balloon. The gold tube is open at both ends and also placed in the balloon. The whole is then extracted for one hour under reflux with stirring. After one hour, all of the solution which contains the soluble and insoluble products in pentane is filtered under vacuum. A first aliquot of the mother solution is taken for fractionation by liquid chromatography then quantitative assay using the same protocol as for the effluents recovered in an open medium.

B-3 Assay of C14 + B fraction 3 - Pyrolysis in an open medium A second pyrolysis is carried out with the S2 analyzer. The stock solution of pentane is evaporated under an inert gas stream. The total soluble extract in pentane is then weighed after transfer to a previously tared container. The content is then fractionated by liquid chromatography, for example an automatic or manual system in order to recover 3 solutions: the first contains saturated hydrocarbons, the second aromatic hydrocarbons and the third organic compounds which may contain sulfur, nitrogen and / or or oxygen. This third fraction is called for example NSOs pentane. After removing the solvent for the three solutions, the 3 chemical fractions are quantitatively evaluated by weighing and their amount expressed relative to the initial charge. The fraction containing the saturated hydrocarbons is injected into a chromatograph in order to determine the residual C14 2 fraction. It can also be subjected to quantitative mass spectrometric analysis in order to assay the amount of mono aromatic structures that are present and to correct the actual amount of saturated hydrocarbons. Once weighed, the 2 fractions respectively containing the aromatics and the hetero atomic compounds are subjected to an elemental analysis to measure C, H and S in the aromatic fraction and C, H, O, N and S in the atomic hetero fraction. . This extract is called, for example, NSOs DCM. For the fraction of saturated hydrocarbons an average composition of 14.9% in H and 85.1% in C is taken. The trap is then rinsed with dichloromethane. The extract thus recovered is quantified by following the same protocol as that of the pentane extract, namely weighing after evaporation of the solvent. This fraction is subjected to elemental analysis for the determination of its C, H, O, N and S. B elements. Closed cell pyrolysis A second aliquot of the pentane stock solution is taken and undergoes the same protocol. only for effluents in an open environment.

The pentane-insoluble residue is dried to be ground to obtain a fine, homogeneous powder and to carry out a second extraction with dichloromethane. The stock solution of dichloromethane is totally evaporated and weighed. It contains almost all hetero atomic structures including the family of asphaltenes. This fraction is subjected to elemental analysis for the determination of its elements C, H, O, N and S.

2906481 B - 4 Dose of solid residues B 4 - Open pyrolysis The solid residue is estimated from Rock Eval pyrolysis. Indeed, knowing the carbon content contained in the S2 peak, and that of the initial charge, the mass of solid residue obtained during these pyrolyses is obtained from the carbon balance: Cinitial = X1 (CCO) + X2 ( CCO2) + X3 (CS2) + X4 (Cresidu) B4 4 b Closed pyrolysis The dichoromethane-insoluble residue is recovered on the filter with the gold tube cut into pieces. Knowing the weight of the empty tube, it is possible to have a first estimate of this residue. Nevertheless, this data is rather imprecise, the residue rate is estimated as that obtained in open environment from the carbon balance. Also, the solid residues are assayed for its constituent elements C, H, N, O, S. In the particular case where the pyrolyzer charges contain pyrite, iron assays are carried out. B - 5 Establishment of mass balances: The same mass balances are carried out in an open and closed environment, namely: load = H2 + CO + CO2 + H2S + H2O + C1 + C2 + C3 + C4 + saturated C6-C14 + C6- C14 aromatic + C14 + saturated + C14 + aromatic + NSOs pentane + NSOs DCM + residue.

Since the carbon and sulfur contents are known for each of the chemical families, it is possible to establish the two respective balances.

From the oxygen balance obtained and by difference with the oxygen content of the feed, it is possible to estimate the amount of water. Finally, once the amount of water is known, it is possible to draw up a hydrogen balance.

Thus, by using the same methods of quantification and fractionation of open and closed pyrolysis products, it is possible to make a direct comparison of the results in order to highlight differences and similarities between the two methods. Io Other chemical classes The aromatic C6-C14 fraction can be separated by subfamily liquid chromatography. Each of the subfamilies is then subjected to gas chromatography analysis coupled to a mass spectrometer for molecular identification. This analysis makes it possible to subdivide the global family into 5 sub-families: the BTXN fraction which comprises the mixture benzene, toluene, xylene and naphthalene. The aromatic sulfur-containing C6-C14 family that includes aromatic sulfur in the C6 to C14 carbon range. The aromatic methyl family contains the aromatic structures, the one containing the alkylated structures and finally the one containing the aromatic naphthenic structures. For the chemical class C74 + aromatics, 3 subfamilies are distinguished: aromatic C14 + 1 which are the most thermally unstable. They break down by producing new aromatic structures; aromatic C14 + 2 which themselves evolve under the effect of temperature by producing aromatic C14 + 3. 15

Claims (5)

claims   1) Method for modeling the thermal cracking of at least one hydrocarbon, characterized in that a) at least the following chemical classes are individualized: • Gaseous fraction: H2S, C1, C2, C3, C4 • Fraction C14_: C14 - sat, C14_alkyl, C14_methyl, BTXN • Fraction C14 +: C14 + sat, C14 + Aro-1, 2, 3 10 • NSOs • solid fraction: prechar, char b- defines a cracking reaction scheme of at least one hydrocarbon, in which it is required that each reagent be decomposed into a gaseous fraction, fraction C14-, fraction C14 + and solid fraction according to the following table: class fractional gas fraction C14_ fraction C14 + solid chemical fraction C14- alkyl -> Cl C2 C3 C4 BTXN alkyl Aro-3 C, 4-methyl -> C1 BTXN Aro-3 C14_Salt Cl C2 C3 C4 methyl Aro-2 C14 + Sat ù + C1 C2 C3 C4 Sat-alkyl methyl Aro-2 C14 + Aro-1 ù> H2S Cl C2 C3 C4 Sat-alkyl methyl Sat + Aro-2 prechar C14 + Aro-2 ù C1 C1ro prechar C14 + Aro-3 -> C1 prechar NSOs ù> H2S C1 C2 C3 C4 Satalkyl methyl S at + Aro-1 prechar prechar ù> C1 char and in which the C14- fraction contains hydrocarbons between 6 and 14 carbon atoms, saturated, denoted Sat-, aromatics of benzene type, toluene, m-, p-, o-xylene , naphthalene and denoted BTXN, alkylated aromatics, denoted alkyl, methylated aromatics, denoted methyl; and in which the C14 + fraction comprises hydrocarbons having more than 14 carbon atoms, saturated, denoted Sat +, and aromatics denoted Ara-1 to Aro-2. And in that a kinetic scheme is defined by determining the kinetic parameters and stoichiometric coefficients associated with said reaction scheme, by carrying out the following steps: c- closed pyrolysis experiments are carried out in order to monitor productions 5 and the disappearance of chemical classes at different temperatures and to ensure the quality of mass balances; d) determining productions and disappearances of the chemical classes at said temperatures by means of a simulation based on said reaction scheme according to step b); and e) said kinetic parameters and said stoichiometric coefficients are determined by means of a numerical inversion in which the difference between said productions and said disappearances simulated in step d) and said productions and said disappearances resulting from the pyrolyses are minimized; in step c).   2) method for modeling the thermal cracking of at least one hydrocarbon according to claim 1, in which a numerical simulator solving speed laws of said reactions of said kinetic scheme as a function of time and temperature is used to determine the kinetic parameters and the stoichiometric coefficients   3) Method for modeling the thermal cracking of at least one hydrocarbon according to one of the preceding claims, wherein said cracking reactions are characterized by activation energy distributions, EEa, EEb, EEf, EEg, and by activation energies, Ec, Ed, Ee, Eh, E; as well as by stoichiometric coefficients, A ', to A'6, B'l to B'6, C', to C'3, D and, 2, E, and E2, F, F3, G, G3, H, H3 and 11 to 13, according to the following kinetic reaction scheme: 2906481 40 EEa Ee NSOs C14 + Aro-1 C14 + Aro- 2 C14 + Aro-3 prechar C14 + Sat C14. Sat C14 alkyl aro C14 + methyl aro E 'A'1 no HC gas + A'2 HC + A'3 C14- + A'4 C14 + sat + A'5 C14 + Aro-1 + A'6 prechar B'1 no HC gas + B'2 HC + B'3 C14- + B'4 C14 + sat + B'5 C14 + Aro-2 + B'6 prechar C'1 Cl + C'2 C14 + Aro-3 + C'3 prechar D ' 1 C1 + From 2 prechar E1 C1 + E2 char F1 HC + F2 C14 + F3 C14 + Aro-2 G1 HC + G2 C14 + G3 C14 + Aro-2 H1 HC + H2 C14. + H3 C14 + Aro-3 I1 C1 + 12 C14- + 13 C14 + Aro-3 and in which no HC gas represents non-hydrocarbon gases and HC represents hydrocarbon gases.   4) Method for modeling the thermal cracking of at least one hydrocarbon according to one of the preceding claims, in which a reduction in the size of the reaction scheme is performed as a function of the conditions required by a field of application, by reducing the number chemical classes by grouping said chemical classes.   5) Application of the method according to one of the preceding claims to the modeling of the secondary cracking of the products resulting from the thermal decomposition of kerogen in the source rock.