METHOD FOR THE ANALYSIS OF THE COMPOSITION OF HYDROCARBONS USING A PYROLYZER WITHOUT A SEPARATION DEVICE

Abstract

The invention relates to a method for the continuous characterization and quantification of C1-C120 hydrocarbons present in a single sample taken from a sedimentary basin, said method comprising pyrolysis of the sample under a non-oxidizing atmosphere, entrainment of the pyrolysis gaseous effluents by means of an inert gas stream and then analysis of said effluents in order to obtain their profiles as a function of pyrolysis temperature, characterized in that said profiles are deconvolved into sub-areas corresponding to each class of isomer via a reference nomogram established for each of said classes and obtained using the empirical Antoine equation resulting from the integration of the Clausius-Clapeyron law for an assumed constant enthalpy of vaporization; Figure of the abstract: [FIG. 9]

Description

Title of the invention: METHOD FOR ANALYZING THE COMPOSITION OF HYDROCARBONS USING A PYROLYZER WITHOUT A SEPARATION DEVICE

[0001] The present invention relates to a method for the continuous characterization of a composition of oils and crude petroleum that can be analyzed in the free state or when contained in a sedimentary rock.

[0002] The parameters sought by the process of the invention include: the composition in terms of hydrocarbons, the average molecular weight of the sample and the boiling point (called "True boiling point").

[0003] The applications targeted by the invention are located mainly in the fields of the petroleum industry, in particular, during the exploration and refining phases. More specifically, the invention relates to the determination, during the first exploration studies at the sedimentary basin scale, of the composition of hydrocarbons contained in source rocks or reservoir rocks, from rock debris (or "cuttings") torn from the drilling tool and brought to the surface by the drilling fluid.

[0004] Indeed, the geological nature of these debris, their physical characteristics, and their content of various fluids (in particular, water, hydrocarbons, and other gases) can provide valuable information on the drilled rocks without the need to extract these fluids from the samples taken, in a short time and automatically. However, the invention may also relate to other fields of application, such as the analysis of sites and soils that have been polluted by hydrocarbons.

[0005] Petroleum originates from kerogen contained in source rocks and derived from organic matter present in the environment at the time of sedimentation of said source rock (SR). Depending on the depositional environment of this source rock, the resulting kerogen can be of three different types. Type I corresponds to a lacustrine environment in which the organic matter produced is enriched in lipids. Type II corresponds to a marine depositional environment in which the precursor organic matter is composed of both lipids and cellulose. Type III organic matter corresponds to a continental depositional environment with organic matter of origin enriched in cellulose and lignin. Depending on the type of kerogen, the composition of the petroleum created by thermal cracking of the kerogen during the burial of the source rock over geological time will vary. The quality of the petroleum is therefore directly affected.

[0006] The rate of advancement of the thermal cracking of the kerogen in question is also a fundamental parameter to consider when studying the composition of a petroleum product. Indeed, at the beginning of the thermal cracking of the kerogen, the petroleum obtained is heavy (i.e., composed of numerous long-chain hydrocarbons), which corresponds to the entry of the source rock into the oil window (the temperature window corresponding to the generation of liquid hydrocarbons from the kerogen). Then, as the depth of the source rock increases due to the subsidence phenomenon, the thermal cracking produces increasingly shorter-chain hydrocarbons from the kerogen until reaching the dry gas window, in which the only hydrocarbon produced is the smallest of all, namely methane.In a second stage, heavy hydrocarbons, whether or not they have migrated from the source rock, can undergo a second thermal cracking called secondary cracking if the surrounding temperature is sufficiently high.

[0007] The final important factor explaining the quality of the oil in question is its preservation over geological time. Indeed, if hydrocarbons are brought to near the surface, their quality can be diminished by archaea-type organisms that can live at temperatures exceeding 100°C and feed on n-alkanes. The direct consequence is a drastic decrease in the oil's API gravity (increase in its density) as well as an enrichment in molecules possessing heteroatoms containing nitrogen, sulfur, and oxygen (NSO).

[0008] All of these parameters help explain the wide variability in the composition of petroleum found on Earth. Thus, the invention will provide users with essential data from the outset of exploratory drilling on the composition of the oil present at the prospected site.

[0009] The Rock-Eval technique (registered trademark - IFP Energies nouvelles) is known and is described in particular in patents FR2472754 and EP0691540B1. This analytical technique, which is rapid and virtually automatic, was developed for the characterization of organic matter and hydrocarbons contained in a rock sample from a geological formation. More specifically, this technique makes it possible to determine the presence, nature, and degree of maturity of the organic matter contained in a rock sample.

[0010] The Rock-Eval method also provides precise information on the quantification of hydrocarbons, the total organic carbon (TOC) content, and the mineral carbon (MinC) content of a rock sample. In particular, the Rock-Eval technique allows for the measurement of the quantity of hydrocarbon compounds released throughout pyrolysis. A pyrogram can then be established; this is a curve representing the evolution of the quantity of hydrocarbon compounds released relative to the weight of the sample considered, as a function of time. A pyrogram It generally presents several peaks. The peaks are well differentiated, and the area of ​​each peak is calculated. This yields, for each peak, a quantity representative of the amount of hydrocarbon compounds released over a temperature range surrounding the peak in question.

[0011] Two main methods implementing two different temperature sequences have been developed. The "Basic" method (also known as the "Bulk Rock method"), dedicated more specifically to source rock samples, is described, for example, in Lafargue et al. (1998) and Behar et al. (2001). The "Reservoir" method (also known as the "Reservoir method"), dedicated more specifically to reservoir rock samples, is described, for example, in patent EP0691540B1.

[0012] Patent EP3918321 describes a method for analyzing C1-C6 gaseous hydrocarbons using a multi-gas analyzer that allows for the quantification of said gaseous hydrocarbons. However, this method does not allow for the quantification of hydrocarbons containing more than six carbon atoms because the transport of these hydrocarbons to the infrared analyzer occurs only in the gaseous state under atmospheric pressure and temperature conditions, which does not correspond to the physical state of hydrocarbons containing more than six carbon atoms.

[0013] Furthermore, it has become necessary to improve the accuracy of the results obtained with the Rock-Eval® process and to optimize their interpretation so that economic and technical decisions relating to oil exploration are based on a more solid foundation. Indeed, since the beginning of the implementation of the Rock-Eval process, numerous methods for characterizing thermo-vaporizable hydrocarbons contained in rocks have been developed, but none has made it possible to precisely describe the composition of these hydrocarbons. Existing methods (described above as well as others developed more recently) at best allow for estimating the relative molecular weights of each fraction of hydrocarbons analyzed by attempting to segment the signal from flame ionization detectors (FIDs) via arbitrarily determined temperature steps without any real physical consistency.

[0014] It is in this context that the invention sought to develop a new process to solve the technical problems posed by previous methods in order to quantify these liquid and solid hydrocarbons under atmospheric conditions by means of a simple and rapid process allowing, in a few steps and from a small quantity sample of various natures, to obtain reliable and unprecedented results.

[0015] The physical principle underlying the characterization method of the invention is based on Antoine's law (a simplification of the Clausius-Clapeyron thermodynamic law), which describes the evolution of the saturated vapor pressure with increasing temperature. when liquid-vapor equilibrium is reached. This physical law is the main factor involved in the temperature rise during the pyrolysis of a rock sample containing free hydrocarbons.

[0016] Indeed, the analysis of a very small quantity of hydrocarbons (a few microliters at most) contained in rocks requires the use of Antoine's law to relate the mass of hydrocarbon evaporated (i.e., having passed from the liquid phase to the gaseous phase) to the temperature of this phase change. For example, if pure n-decane (whose boiling point is 174.1°C) is analyzed by pyrolysis via a constant-rate temperature increase, the temperature of maximum evaporation of n-decane will be lower than the theoretical boiling point (between 70 and 130°C depending on the quantity produced analyzed). This observation is also accentuated by a second phenomenon occurring during the evaporation of a hydrocarbon compound, namely the diffusion of matter, which is governed by Fick's law, through an interface whose flux is directed in the opposite direction to the concentration gradient (in the direction of decreasing concentration values).

[0017] For each n-paraffin (hydrocarbons between C1 and C12O), the evaporation curves relating the mass of the distilled hydrocarbons to the temperature of the pyrolysis furnace were modeled using Antoine's thermodynamic law. This approach then made it possible to create a nomogram giving the position of each hydrocarbon according to its molecular weight.

[0018] Thus, the object of the invention is a process for the continuous characterization and quantification of C1-C120 hydrocarbons comprising pyrolysis under a non-oxidizing atmosphere of the sample, the entrainment of the pyrolysis gaseous effluents by means of an inert gas stream and then the analysis of said effluents in order to obtain their profiles as a function of the pyrolysis temperature, characterized in that said profiles are superimposed on the reference nomogram created from the Clausius Clapeyron physical law to determine the composition of hydrocarbons in the analyzed sample.

[0019] More specifically, the experimental method of the invention consists of raising the temperature of said sample under an inert atmosphere at a constant rate, from the lowest possible temperature T1 (i.e., at ambient temperature, see below if the technical means permit) to a final temperature T2 necessarily higher than the highest boiling point of the mixture to be analyzed by said method. The temperature T1 is therefore necessarily lower than the temperature T2.

[0020] According to an advantageous feature of the process of the invention, the pyrolysis temperature is raised with a single temperature gradient of between 0.1 and 50°C / min. Preferably, this temperature gradient is between 10 and 30°C / min.

[0021] According to another feature of the process of the invention, pyrolysis is carried out with a constant heating rate of between 0.5°C / min and 50°C / min to reach a final temperature of between 30°C and 900°C.

[0022] The implementation of said process makes it possible to obtain the composition of the mixture of hydrocarbons contained in said rock sample as well as the average molar mass and the API degree via the processing of the data by the nomogram of which each of the curves composing it (ranging from n-Cl to n-C120) is theoretically calculated by the following formula (F).

[0023] mi= (DvxMiXt) / (RxT)xl0AB / (T+C)

[0024] With x;(-) : the mole fraction of the hydrocarbon considered m (kg): mass of the hydrocarbon considered; Dv (m³ / s): volumetric flow rate of the carrier gas; Mi (kg / mol): molar mass of the hydrocarbon considered; T (K): temperature; t (s): time R (J.mol*.K*): the ideal gas constant A (Pa), B (-) and C (K): the parameters of the Antoine equation; Pi (Pa): the partial pressure Ptot (Pa): the total pressure of the system.

[0025] The abscissa axis of said nomogram represents temperature, while the ordinate axis represents mass. Thus, in summary, the process according to the invention for the analysis of free petroleum or petroleum contained in a rock sample comprises a pyrolysis phase of the sample carried out under an inert atmosphere within a range of increasing temperatures between an initial temperature T1 and a final temperature T2, with a linear temperature increase at a rate between 0.1°C / min and 50°C / min. The vaporized hydrocarbons resulting from the pyrolysis of the sample are quantified and characterized by their vaporization temperatures. Since the evolution of these temperatures is theoretically predicted by Antoine's law, the hydrocarbon signal obtained can then be segmented into different classes of Cl to C12O isomers.

[0026] Said process may optionally be followed by an oxidizing phase in order to determine the TOC (total organic carbon percentage) in the case of the analysis of heavy oils.

[0027] The process of the invention can integrate high-performance software that performs the plotting of curves corresponding to the profiles of hydrocarbons, quantitative calculations, determination of the distributions of these hydrocarbons and that makes it possible to obtain information on the quantities of hydrocarbons obtained by pyrolysis, as well as new data on their genesis.

[0028] The implementation of the method of the invention complements and extends the detection of gaseous hydrocarbons in C1-C6 which can be carried out via, for example, the method described in patent EP3918321. Indeed, the minimum analysis start temperature of 30°C provided for in the method of the invention is not suitable for obtaining analysis results for hydrocarbons below C7.

[0029] Other features and advantages of the process according to the invention will become apparent from the following description of non-limiting examples of implementation, with reference to the figures attached and described below.

[0030] [Fig. 1] is a schematic view of a preferred embodiment of the device intended for implementing the method of the invention.

[0031] [Fig.2] illustrates the temperature variation sequence according to the process of the invention.

[0032] [Fig.3] is a graph / abacus created from Antoine's equation applied to Rock-Eval pyrolysis furnace, according to a particular implementation of the process of the invention, allowing the quantity of alkane to be predicted for the isomers of Cl to C40.

[0033] [Fig.4] represents a superposition of the nomogram and a hydrocarbon curve obtained via the temperature sequence on a petroleum sample according to an implementation method of the process of the invention.

[0034] [Fig.5] is a superposition of the experimental curves obtained via analysis by Rock-Eval of n-CIO, n-C20, n-C30 and n-C40 at different masses with theoretical simulated distillation curves of these same paraffins obtained via Antoine's equation.

[0035] [Fig.6] represents a distribution of isomers of a crude oil and two oils of Reference in percentages. The black bars are the proportions obtained from the Rock-Eval simulation distillation while the hatched bars were obtained via gas chromatography analysis.

[0036] [Fig. 7] shows another distribution of the isomers of a crude oil and two reference oils in percentages. The black bars are the proportions obtained from the Rock-Eval simulation distillation, while the hatched bars were obtained via gas chromatography analysis.

[0037] [Fig.8] represents yet another distribution of isomers of crude oil and of Two reference oils in percentages. The black bars are the proportions obtained from the Rock-Eval simulation distillation, while the hatched bars were obtained via gas chromatography analysis.

[0038] [Fig.9] represents the Rock-Eval simulated distillation curves (curves shown solid black) for a crude oil and for two reference oils as well as the simulated distillation curves by gas chromatography (dotted curves).

[0039] The invention relates, in general, to a method for characterization hydrocarbons contained in a rock sample. This process is characterized by a linear temperature rise under an inert atmosphere according to a slope chosen by the user and between 0.1 °C and 50 °C per minute.

[0040] In particular, the invention relates to the analysis of thermo-vaporizable hydrocarbon fractions and, specifically, to their identification by temperature. Indeed, it is well known that lighter hydrocarbons vaporize before heavier ones. However, since the quantities of hydrocarbons analyzed are very small with the Rock-Eval method, the temperatures at which these hydrocarbons are detected do not correspond to the theoretical boiling points of the sample components. Since the advent of the Rock-Eval method, which has made it possible to quantify the hydrocarbons contained in petroleum source rocks in a remarkable time, determining the composition of the thermo-vaporizable hydrocarbons contained in these rocks has become essential because this composition constitutes a primary quality criterion for the petroleum contained in these rocks.Indeed, estimates of the financial investment required to bring the prospective oil field into production will differ depending on whether the hydrocarbons present are light or heavy.

[0041] The main problem posed by determining the composition of hydrocarbon mixtures using the Rock-Eval method and related pyrolyzers lay in the absence of a separation device, such as, for example, in chromatographic analysis. Furthermore, although the temperatures read by the Rock-Eval device are accurate, they do not correspond to the actual boiling points of the compounds analyzed because the latter are present in insufficient quantities.

[0042] The invention and its implementation method described below make it possible to overcome this problem through the application of the Clausius-Clapeyron law and, in particular, Antoine's law describing the transition of hydrocarbons from the liquid phase to the vapor phase during a temperature increase. This method can advantageously, but not exclusively, be implemented using the Rock-Eval device described in patent EP2342557.

[0043] The process of the invention is applied primarily to petroleum rock samples such as reservoir rocks, source rocks, and crude oils, but can also be used for hydrocarbon-contaminated soils or for catalysts from refining processes. More generally, the invention can be applied to any sample containing hydrocarbons whose composition needs to be determined. Until now, determining the composition of these hydrocarbons in a sample required extraction using various solvents followed by chromatographic analysis. The invention is an advancement in that it allows for automatic, rapid, and in-situ characterization of hydrocarbon composition.

[0044] Figure 1 schematically represents one embodiment of the device for implementing the process. This device comprises a pyrolysis furnace 4 with a temperature range from 0°C to 900°C. A rock sample contained in a basket 3 is introduced into the furnace via a piston 2. The inert carrier gas 1, circulating continuously at a constant flow rate in the system, carries the pyrolysis product towards the flame ionization detector 6 (FID), thus enabling the quantification of hydrocarbons. According to an alternative embodiment, the device can be equipped with a heating divider 5, allowing the gas flow to be redirected to other detectors.

[0045] Figure 2 represents the temperature rise from T1 to T2 with a single temperature gradient between 0.1 and 50°C / min. Therefore, this temperature rise does not include any plateaus.

[0046] The flow of pyrolyzed hydrocarbons is carried and directed by the inert gas stream, the flow rate of which can be between 20ml / min and 70ml / min, towards a flame ionization detector (FID) type 6 ([Fig.l]).

[0047] The thermo-vaporization phenomenon occurring during the pyrolysis of organic matter with thermal cracking is divided into two phases. The first phase is predominant from 0°C to 400°C and mainly concerns relatively light hydrocarbons (below C40), while the second phase only becomes predominant above 400°C and concerns, in particular, heavy hydrocarbons, resins, asphaltenes, and kerogen.

[0048] Once the pyrolysis step is complete, the thermo-vaporization curve of the hydrocarbons is obtained. This curve may include one or more peaks depending on the homogeneity of the distribution of boiling points of its compounds.

[0049] According to an advantageous illustration method, this curve can be represented by a graph of the type m = f(T) where m is the mass in mg and T is the temperature in (°K).

[0050] The hydrocarbon curve can then be superimposed on the theoretical vaporization chart of aliphatic n-hydrocarbons as in [Fig.4].

[0051] The curves comprising the nomogram were determined by applying Antoine's equations to pyrolysis using the Rock-Eval method. During the Rock-Eval analysis, the signal obtained via the FID (Flame Ionization Detector) allows us to determine the quantity of hydrocarbons generated during pyrolysis as a function of temperature. Antoine's law provides a relationship between the partial pressure (Pp) of a gas and the temperature (T) within the framework of a liquid-vapor equilibrium.

[0052] Log(Pi) = A - (B / (T+C) where Pi = Psat / Ptot.

[0053] During the Rock-Eval analysis, equilibrium is never reached because the gaseous phase is constantly renewed, which is the main cause of error or of approximation of this method. In order to take into account the mass of hydrocarbons which is measured by the Rock-Eval method, the partial pressure P; is then expressed according to Raoult's law.

[0054] Pj = XjX Ptot

[0055] After applying the ideal gas law, the following relation (F) is obtained.

[0056] mi= (DvxMiXt) / (RxT)xl0AB / (T+C)

[0057] with Xj(-) : the mole fraction of the hydrocarbon considered m; (kg): the mass of the hydrocarbon considered Dv (m³.s'): the volumetric flow rate of the carrier gas Mi (kg.mol'): the molar mass of the hydrocarbon considered T (K): the temperature t (s): time R (J.mol*.K*): the ideal gas constant A (Pa), B (-) and C (K): the parameters of the Antoine equation; Pi (Pa): the partial pressure Ptot (Pa): the total pressure of the system.

[0058] Thus, for each n-paraffin from Cl to C12O, it is possible to determine the curves shown in [Fig. 3], representing the mass of liquid hydrocarbons transitioning to gaseous form as a function of temperature. The tip of each curve corresponds to the theoretical boiling point of each compound. The relative position of each curve depends on the molar mass of the n-alkane and its specific parameters (ABC) of the Antoine equation.

[0059] The general shape of the curves is determined by the temperature ramp and the volumetric flow rate used in the device. Thus, each curve on the nomogram corresponds to the evaporation of the mass of n-alkanes as a function of the temperature increase in the pyrolysis furnace. By superimposing the hydrocarbon curve onto this nomogram, the following approximations are therefore assumed. - Antoine's law is used when equilibrium between the gaseous and liquid phases is not reached. - Each isomer behaves thermally like the corresponding n-alkane. - Each n-alkane behaves independently of the other n-alkanes within a mixture.

[0060] The hydrocarbon curve derived from the FID signal is then segmented according to an algorithm that allows for the estimation of the proportion of each class of isomers within the mixture. The algorithm used may vary depending on the application and the specific case studies encountered.

[0061] The proportions of each class of isomer obtained by the Rock-Eval RE method The proportions of isomers obtained from oils were correlated with those obtained via gas chromatography (GC) (examples in Figures 6 to 8). The differences between the results of the two methods are very small. Although biases related to the Rock-Eval characterization method remain, these are known and controlled. Indeed, they are closely linked to the approximations stated during the derivation of the curve equations.

[0062] The proportions of each class of isomers then allow for the plotting of simulated distillation curves. This time, the temperatures used to reconstruct these curves are the theoretical boiling points of the n-alkane of the class of isomers considered. These Rock-Eval simulated distillation curves (solid line) are then compared to the simulated distillation curves obtained by gas chromatography (dashed line) ([Fig. 9]).

[0063] The invention is primarily intended for the analysis of free and contained oils in reservoir rocks (porous and permeable). The invention can also be used for the analysis of source rocks but may, in this case, prove less precise due to matrix effects inherent in the clay lithology of the latter.

[0064] In the following section, three oil samples (one crude oil and two reference oils with known boiling points) were analyzed using the Rock-Eval simulated distillation method and then by gas chromatography in order to compare the results.

[0065] The first oil (reference 775199) is a so-called "light" oil because it has a significant fraction of short-chain hydrocarbons. The second (reference 770350) is a "heavy" oil because it has a significant fraction of long-chain hydrocarbons. Finally, "Arabian Light" oil is a light crude oil from Saudi Arabia.

[0066] First, samples comprising micro-volumes of oils of approximately 5 pL are taken using a micro-syringe for gas chromatography and injected into the capsule. Finally, the mass of the samples is weighed using a precision balance. Inert silica may be added if necessary.

[0067] The gondola 3 containing the sample is then made available to the automatic changer which allows the introduction of the latter into the pyrolysis oven 4 via the piston 2 (cf [Fig.l]).

[0068] The oven temperature evolution is programmed in advance following a cycle going from a temperature T1 preferably between 25°C and 35°C to a final temperature T2 preferably, but not exclusively, between 640°C and 660°C. The temperature variation ramp used is preferably between 15 and 25°C / min (see [Fig.2]).

[0069] During the temperature increase in the pyrolytic oven, the signal hydrocarbons detected by the FID 6 are recorded.

[0070] The results obtained for oils and petroleum are then processed using specific software that allows visualization and processing of the analysis results from the Rock-Eval. The acquired data are then imported into the Rock-Eval simulated distillation module. Depending on the relative position of the hydrocarbon curve on the mass / temperature graph (f(T)=m), the curve is segmented into sub-areas or deconvolved according to a mathematical method chosen by the user based on Antoine's experimental laws.

[0071] Each of the areas obtained then corresponds to a class of hydrocarbons having the same number of carbon atoms and thus allows us to obtain an estimate of the distribution of these hydrocarbons according to their number of carbon atoms (Cf[Fig.4]).

[0072] Finally, knowing the boiling points of the corresponding n-alkanes, it is possible to reconstruct the simulated distillation curves for each of the three oils analyzed (see [Fig. 5]). The average molar mass of the entire oil can also be estimated.

[0073] The composition of the three oils determined using the simulated Rock-Eval distillation method and that obtained via gas chromatography analysis is represented by the diagrams in [Fig.6] to 8.

[0074] Comparing these three oils, we observe that each has its own "pattern" in terms of hydrocarbon class distribution, which results directly from its composition. Indeed, reference oil 775199 has a bimodal composition with approximately two-thirds light hydrocarbons and one-third heavier hydrocarbons, resulting in a specific "pattern" in the hydrocarbon distribution diagram and its simulated distillation curve. Reference oil 770350, on the other hand, is more homogeneous, resulting in a Gaussian distribution of its hydrocarbon proportions. The corresponding simulated distillation curve is sigmoidal. Finally, Arabian Light has an asymmetric Gaussian distribution centered on the C13 hydrocarbon, but with varying proportions of heavy hydrocarbons that decrease as the hydrocarbon chains lengthen.

[0075] In order to compare the simulated distillation results obtained by Rock-Eval and gas chromatography, respectively, normalization is necessary over the C1-C40 range (the characterization limit of the chromatography used) with respect to the Rock-Eval data. This is because Rock-Eval analysis allows the temperature to be increased up to 650°C in the pyrolysis furnace, thus quantifying the entire quantity of oil, unlike conventional chromatographic analyses.

[0076] When comparing simulated distillation data obtained by Rock-Eval and chromatography, it is observed that the "fingerprint" of the analyzed oil, as represented by its hydrocarbon distribution diagram and simulated distillation curve, is largely preserved. However, some differences remain, all related to the specific characteristics of the two methods used.

[0077] Indeed, since the device is not equipped with a separation column, a mixing phenomenon occurs among the analyzed hydrocarbons. Therefore, isomers located far from the "average" isomer of the mixture (i.e., the most abundant isomer in the mixture) have affected boiling points and are shifted towards the average temperatures of the mixture. This phenomenon is particularly evident on the Rock-Eval distribution histogram of reference oil 775199, and especially on the second peak centered around the C21 hydrocarbon, whereas the latter is centered around the C26 isomers on the chromatography distribution diagram.

[0078] Another limitation of the method of the invention arises from the minimum starting temperature of the analysis cycle, which corresponds to the ambient laboratory temperature plus approximately 10°C, i.e., 30°C. This temperature does not allow for the characterization of hydrocarbons with fewer than 7 carbon atoms. However, the method for characterizing C1-C6 hydrocarbons described previously in patent EP3918321 can complement the characterization of light hydrocarbons.

Claims

Claims

1. Method for the continuous characterization and quantification of Cl-Cl 20 hydrocarbons present in a single sample taken from a sedimentary basin, said method comprising pyrolysis of the sample under a non-oxidizing atmosphere, entrainment of the pyrolysis gaseous effluents by means of a stream of inert gas and then analysis of said effluents in order to obtain their profiles as a function of the pyrolysis temperature, characterized in that the deconvolution of said profiles into sub-areas corresponding to each isomer class is carried out via a reference chart established via equation (F) below for each of said classes and obtained using the empirical equation of Antoine resulting from the integration of the physical law of Clausius Clapeyron for an enthalpy of vaporization assumed to be constant; mi= (DvxMjXt) / (RxT)xlOawo with: m; (kg): the mass of the hydrocarbon considered Dv(m3.s *): the volume flow rate of the vector gas Mi (kg.mol *): the molar mass of the hydrocarbon considered T (K): the temperature t (s): the time R (J.mol *.K *): the perfect gas constant A (Pa), B (-) and C (K): the parameters of the Antoine equation Pi (Pa): the partial pressure.

2. Method according to claim 1, characterized in that the pyrolysis is carried out with a constant heating rate of between 0.5°C / min and 50°C / min to reach a final temperature of between 30°C and 900°C.

3. Method according to claim 2, characterized in that the pyrolysis is carried out at a heating rate of between 15°C / min and 25°C / min to reach a final temperature of between 640°C and 660°C.

4. Method according to one of the preceding claims, characterized in that the deconvolution of the profiles measured by the Antoine equation is carried out so as to obtain the proportions of the isomer classes and the simulated distillation curves of the analyzed sample as well as the distribution diagram of said isomer classes.

5. Method according to one of the preceding claims, characterized in that that the pyrolysis gaseous effluents are entrained and directed by the inert gas stream with a flow rate between 20ml / min and 70ml / min.

6. Method according to one of the preceding claims, characterized in that the analysis of the effluents is carried out by means of a flame ionization detector.

7. Method according to one of the preceding claims, characterized in that said sample is chosen from the group comprising source rocks, kerogens, coals, reservoir rocks, crude oils and heavy petroleum fractions, resins, asphaltenes, catalysts and soil samples.

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