Method and system for evaluating movable hydrocarbon components

Abstract

The invention discloses a method and system for evaluating movable hydrocarbon components, and the method comprises the following steps: soaking a rock sample in a composite organic solvent, and fully grinding to obtain a total hydrocarbon extract; performing compound detection and analysis on the total hydrocarbon extract, and calculating the hydrocarbon loss rate of the rock sample in the process of transferring the rock sample from the underground to the laboratory condition according to the analysis result; and performing pyrolysis analysis on the dried total hydrocarbon extract to obtain the free hydrocarbon content and the pyrolysis hydrocarbon content, and based on the free hydrocarbon content and the pyrolysis hydrocarbon content, combining the hydrocarbon loss rate to obtain the movable hydrocarbon content. According to the invention, the loss caused by the experimental process in the evaluation of the movable hydrocarbon is reduced.

Description

Technical Field

[0001] This invention relates to the field of hydrocarbon source rock hydrocarbon generation potential evaluation technology, and in particular to a method and system for evaluating mobile hydrocarbon components. Background Technology

[0002] With continuous breakthroughs in the exploration and development of continental shale oil in China, the occurrence and preservation of shale oil have gradually become a research hotspot. In the conventional evaluation of the hydrocarbon generation potential of source rocks, the hydrocarbon composition in the source rocks undergoes irreversible changes due to changes in temperature and pressure after sampling. A large amount of light hydrocarbon components and volatile components are lost, and the contribution of mobile hydrocarbons (Sm, i.e., free hydrocarbons S1 that were not lost under the original formation conditions and possibly some adsorbed hydrocarbons) is inevitably underestimated, interfering with the evaluation of hydrocarbon generation potential. Although the loss of mobile hydrocarbons (Sm) and evaluation errors can be reduced by strengthening the rigor of core sampling methods (e.g., through online analysis using cryogenic freezing) or improving the constraints of analytical methods (e.g., multi-stage pyrolysis analysis), the procedures and costs are relatively increased. At the same time, the repeatability and stability of sampling and analysis are also uncertain, so the evaluation of mobile hydrocarbons (Sm) in rocks, especially oil shale, remains a challenge. Reasonable characterization of free hydrocarbons (S1') under experimental analysis conditions is key to the assessment of undissipated movable hydrocarbons (Sm) in rocks. This is also crucial for predicting the distribution of sweet spots in shale oil exploration and is a challenge in the exploration and development of continental shale oil.

[0003] Therefore, it is necessary to provide a highly repeatable identification and recovery technology and method for mobile hydrocarbons (Sm) based on geochemical principles, which is of great significance for the exploration and development of continental shale oil in my country and for maintaining the security of the national energy structure.

[0004] Current geochemical techniques often employ multi-stage fractionation analysis of source rocks or shale samples. While this increases the number of steps involved, improving the relative content of mobile hydrocarbons, it also affects the stability of analysis across different samples. From a laboratory perspective, due to differences in sample lithology, no fractionation method can fundamentally define which hydrocarbon components are absolutely mobile; the constraints on their relative content depend on different experimental procedures or detection instruments. Furthermore, some volatile components are unavoidably lost during rock sample experiments. Therefore, minimizing the number of rock treatments is crucial for accurately recovering the relative content of mobile hydrocarbons (Sm). Summary of the Invention

[0005] The purpose of this invention is to provide a movable hydrocarbon component evaluation scheme that can solve the problem of light hydrocarbon rate loss in rock laboratory powder processing.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for evaluating mobile hydrocarbon components, comprising: immersing a rock sample in a composite organic solvent for thorough grinding to obtain a total hydrocarbon extract; performing compound detection and analysis on the total hydrocarbon extract, and calculating the hydrocarbon loss rate of the rock sample during its transfer from downhole to laboratory conditions based on the analysis results; performing pyrolysis analysis on the dried total hydrocarbon extract to obtain the free hydrocarbon content and the pyrolysis hydrocarbon content, and based on this, combined with the hydrocarbon loss rate, obtaining the mobile hydrocarbon content.

[0007] Preferably, the step of performing compound detection and analysis on the whole hydrocarbon extract and calculating the hydrocarbon loss rate of the rock sample under laboratory conditions from downhole based on the analysis results includes: obtaining the distribution and relative abundance of n-alkanes in the sample based on the compound detection and analysis experiment; calculating the molar concentration of each n-alkane in the whole hydrocarbon component based on the distribution and relative abundance of the n-alkanes; establishing a first relational expression characterizing the relationship between the molar concentration of n-alkanes and the number of carbon atoms based on the molar concentration of each n-alkane; and inverting the theoretical mass fraction of unaffected ground-state light hydrocarbons based on the first relational expression to obtain the hydrocarbon loss rate.

[0008] Preferably, the step of establishing a first relational expression characterizing the relationship between the molar concentration and the number of carbon atoms of the n-alkane based on the molar concentration of each n-alkane includes: plotting a first curve representing the change of the natural logarithm of the molar concentration of the n-alkane with the number of carbon atoms based on the molar concentration of each n-alkane; extracting a stable segment from the first curve to form a second curve; and fitting the second curve to obtain the first relational expression.

[0009] Preferably, the step of calculating the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of the n-alkane includes: calculating the peak area of ​​the n-alkane using an integral method based on the distribution and relative abundance of the n-alkane; and calculating the relative mass fraction of all n-alkanes based on the peak area calculation results, thereby obtaining the molar concentration of each n-alkane.

[0010] Preferably, the content of mobile hydrocarbons is calculated using the following expression:

[0011]

[0012] Where Sm represents the content of mobile hydrocarbons, S1' represents the content of free hydrocarbons, S2' represents the content of pyrolytic hydrocarbons, and P represents the hydrocarbon loss rate.

[0013] Preferably, the composite organic solvent is a mixture of hexane, dichloromethane and methanol in a ratio of 40:10:1.

[0014] Preferably, the total hydrocarbon extract is subjected to compound detection and analysis using total hydrocarbon chromatography or chromatographic mass spectrometry.

[0015] On the other hand, embodiments of the present invention provide a system for evaluating mobile hydrocarbon components, comprising: a full hydrocarbon extract generation module configured to soak a rock sample in a composite organic solvent for thorough grinding to obtain a full hydrocarbon extract; a hydrocarbon loss rate calculation module configured to perform compound detection and analysis on the full hydrocarbon extract, and calculate the hydrocarbon loss rate of the rock sample under laboratory conditions during the transfer from downhole to laboratory conditions based on the analysis results; and a mobile hydrocarbon reduction module configured to perform pyrolysis analysis on the dried full hydrocarbon extract to obtain the free hydrocarbon content and the pyrolysis hydrocarbon content, and obtain the mobile hydrocarbon content based on this and the hydrocarbon loss rate.

[0016] Preferably, the movable hydrocarbon reduction module includes: a sample detection unit configured to obtain the distribution and relative abundance of n-alkanes in the sample based on compound detection and analysis experiments; a n-alkane analysis unit configured to calculate the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of the n-alkanes; a relational expression generation unit configured to establish a first relational expression characterizing the relationship between the molar concentration and carbon number of n-alkanes based on the molar concentration of each n-alkane; and a loss rate generation unit configured to invert the theoretical mass fraction of unaffected ground-state light hydrocarbons based on the first relational expression, thereby obtaining the hydrocarbon loss rate.

[0017] Preferably, the composite organic solvent is a mixture of hexane, dichloromethane and methanol in a ratio of 40:10:1.

[0018] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0019] This invention proposes a method and system for evaluating mobile hydrocarbon components. The method and system involve sequentially grinding and extracting rock samples under the protection of a composite organic solvent, identifying compounds, performing semi-quantitative analysis, and calculating the proportion of light hydrocarbons lost (P). Finally, pyrolysis analysis of the extracted and broken samples yields the lost free hydrocarbons (S1') and pyrolytic hydrocarbons (S2'), and the mobile hydrocarbons (Sm) are determined by combining the loss proportions. This invention provides a simple, scientific, accurate, and effective evaluation of mobile hydrocarbons in geological rock samples, reducing losses caused by the experimental process in mobile hydrocarbon evaluation.

[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 This is a schematic diagram of the steps of a method for evaluating mobile hydrocarbon components according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of the first curve of the first rock sample in the method for evaluating mobile hydrocarbon components according to an embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the first curve of a second rock sample in the method for evaluating mobile hydrocarbon components according to an embodiment of this application.

[0025] Figure 4 This diagram illustrates the results of mobile hydrocarbon component determination for two rock samples obtained using both the present invention and conventional pyrolysis tests, respectively, in an embodiment of the method for evaluating mobile hydrocarbon components according to this application.

[0026] Figure 5 This is a block diagram of a system for evaluating mobile hydrocarbon components according to an embodiment of this application. Detailed Implementation

[0027] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0028] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a” and “an” as used herein are also intended to include the plural. It should also be understood that the terms “comprising” and / or “including” as used herein specify the presence of the stated features, integers, steps, operations, units, and / or components, without excluding the presence or addition of one or more other features, integers, steps, operations, units, components, and / or combinations thereof.

[0030] With continuous breakthroughs in the exploration and development of continental shale oil in China, the occurrence and preservation of shale oil have gradually become a research hotspot. In the conventional evaluation of the hydrocarbon generation potential of source rocks, the hydrocarbon composition in the source rocks undergoes irreversible changes due to changes in temperature and pressure after sampling. A large amount of light hydrocarbon components and volatile components are lost, and the contribution of mobile hydrocarbons (Sm, i.e., free hydrocarbons S1 that were not lost under the original formation conditions and possibly some adsorbed hydrocarbons) is inevitably underestimated, interfering with the evaluation of hydrocarbon generation potential. Although the loss of mobile hydrocarbons (Sm) and evaluation errors can be reduced by strengthening the rigor of core sampling methods (e.g., through online analysis using cryogenic freezing) or improving the constraints of analytical methods (e.g., multi-stage pyrolysis analysis), the procedures and costs are relatively increased. At the same time, the repeatability and stability of sampling and analysis are also uncertain, so the evaluation of mobile hydrocarbons (Sm) in rocks, especially oil shale, remains a challenge. Reasonable characterization of free hydrocarbons (S1') under experimental analysis conditions is key to the assessment of undissipated movable hydrocarbons (Sm) in rocks. This is also crucial for predicting the distribution of sweet spots in shale oil exploration and is a challenge in the exploration and development of continental shale oil.

[0031] Therefore, it is necessary to provide a highly repeatable identification and recovery technology and method for mobile hydrocarbons (Sm) based on geochemical principles, which is of great significance for the exploration and development of continental shale oil in my country and for maintaining the security of the national energy structure.

[0032] Current geochemical techniques often employ multi-stage fractionation analysis of source rocks or shale samples. While this increases the number of steps involved, improving the relative content of mobile hydrocarbons, it also affects the stability of analysis across different samples. From a laboratory perspective, due to differences in sample lithology, no fractionation method can fundamentally define which hydrocarbon components are absolutely mobile; the constraints on their relative content depend on different experimental procedures or detection instruments. Furthermore, some volatile components are unavoidably lost during rock sample experiments. Therefore, minimizing the number of rock treatments is crucial for accurately recovering the relative content of mobile hydrocarbons (Sm).

[0033] To address the technical problems mentioned above, this application provides a method and system for evaluating mobile hydrocarbon components. Based on core sample processing methods and the principle of natural loss of light hydrocarbons during experiments, this method and system comprehensively recovers the loss ratio of hydrocarbons under experimental conditions through a combination of whole-hydrocarbon chromatography or chromatographic-mass spectrometry and rock pyrolysis. The aim is to fully understand the loss mechanism of mobile hydrocarbons during shale oil evaluation, establish relevant parameters and formulas, and achieve a simple and rapid evaluation of mobile hydrocarbons in rocks, especially oil shale, providing scientific support for the exploration and development of continental shale oil in my country.

[0034] Example 1

[0035] Figure 1 This is a schematic diagram illustrating the steps of a method for evaluating mobile hydrocarbon components according to an embodiment of this application. See below for reference. Figure 1 The specific steps of the method for evaluating mobile hydrocarbon components (also referred to as the "mobile hydrocarbon component evaluation method") described in the embodiments of the present invention will be explained.

[0036] Step S110: The rock sample is soaked in a composite organic solvent and then thoroughly ground to obtain a total hydrocarbon extract.

[0037] In this embodiment of the invention, the composite organic solvent is a mixed organic solvent composed of n-hexane, dichloromethane, and methanol. The ratio of n-hexane, dichloromethane, and methanol is 40:10:1.

[0038] In one embodiment, the rock sample to be tested is a massive shale sample.

[0039] Specifically, any blocky shale sample of a specific mass is immersed in a mortar containing a custom-ratio composite organic solvent (hexane / dichloromethane / methanol in a ratio of 40:10:1v / v / v), and then ground to the maximum extent in the mortar to obtain the total hydrocarbon extract H. This process avoids hydrocarbon loss during conventional pyrolysis laboratory powder processing and is more consistent with the simulation of underground fracturing.

[0040] After obtaining the total hydrocarbon extract, proceed to step S120.

[0041] Step S120: The total hydrocarbon extract obtained in step S110 is subjected to compound detection and analysis, and the hydrocarbon loss rate under laboratory conditions during the transfer of rock samples from downhole to laboratory conditions is calculated based on the analysis results.

[0042] In step S120, the first step is to obtain the distribution and relative abundance of n-alkanes in the sample based on compound detection and analysis experiments.

[0043] In the first step, the compounds in the total hydrocarbon extract obtained in step S110 can be detected and analyzed by total hydrocarbon chromatography or chromatography-mass spectrometry.

[0044] The whole hydrocarbon extract H is subjected to whole hydrocarbon chromatographic analysis or chromatographic-mass spectrometric analysis, for example, analysis and compound detection of whole hydrocarbon component H on a gas chromatograph-mass spectrometer. All n-alkanes are identified at characteristic ion m / z = 57 or 85 or in the total ion current (TIC) mass chromatogram, thereby determining the distribution and relative abundance of n-alkanes.

[0045] The second step is to calculate the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of n-alkane obtained in the first step.

[0046] In the second step, firstly, based on the distribution and relative abundance of n-alkanes, the peak area of ​​n-alkanes is calculated using the integration method. Then, based on the peak area calculation results, the relative mass fraction of all n-alkanes is calculated, thereby obtaining the molar concentration of each n-alkane.

[0047] The peak area of ​​the detected n-alkanes is semi-quantitatively calculated using an integral method. Then, the relative mass fraction of all n-alkanes is calculated based on the peak area. Finally, the molar concentration of each n-alkane in the total hydrocarbon component is calculated based on the relative molecular mass of each n-alkane (e.g., methane: 16.03; n-heptadecane: 240.28; etc.).

[0048] The third step is to establish a first relational expression based on the molar concentrations of each n-alkane obtained in the second step. In this embodiment of the invention, the first relational expression is used to characterize the relationship between the molar concentration and the number of carbon atoms of the n-alkane.

[0049] In the third step, firstly, based on the molar concentration of each n-alkane, a first curve representing the natural logarithm of the molar concentration of n-alkane as a function of the number of carbon atoms is plotted. Then, a stable segment of the curve is extracted from the first curve to form a second curve. Finally, the second curve is fitted to obtain the first relational expression.

[0050] First, the correlation between the natural logarithm of the molar concentration of each n-alkane and the number of carbon atoms is calculated to obtain the first curve. Then, data points in the stable segment of the curve (representing medium- to high-molecular-weight n-alkanes that are not easily affected) are selected to obtain the second curve. Finally, a stable slope formula is derived by fitting the second curve (e.g., ...). Figure 2 In the equation y = -0.1312x - 5.8713, the value of x is given by y = -0.1312x - 5.8713.

[0051] Figure 2 and Figure 3 The first curve diagrams of two rock samples A and B are shown respectively.

[0052] The fourth step is to invert the theoretical mass fraction of the unaffected ground-state light hydrocarbons according to the first relational expression, thereby obtaining the hydrocarbon loss rate.

[0053] Based on the first relational expression mentioned above, the relative molar concentration and theoretical mass fraction of the theoretically unaffected ground-state light hydrocarbons are first obtained through inversion. Then, the theoretical loss ratio P (%) of the n-alkanes is calculated based on the theoretical mass fraction of the light hydrocarbon components. Thus, in this embodiment of the invention, this ratio P can be used to represent the loss rate of mobile hydrocarbons in the rock from underground to laboratory conditions (before drilling, sampling, storage, transportation, and laboratory treatment), thereby proceeding to step S130.

[0054] Step S130: Perform pyrolysis analysis on the dried total hydrocarbon extract to obtain the free hydrocarbon content and pyrolysis hydrocarbon content. Based on the current free hydrocarbon content and pyrolysis hydrocarbon content data, combined with the hydrocarbon loss rate, obtain the mobile hydrocarbon content.

[0055] The broken sample after natural drying (i.e., the broken sample after natural drying of the total hydrocarbon extract H obtained in step S110) was subjected to pyrolysis analysis to obtain the S1' index and S2' index (pyrolytic hydrocarbons in the broken sample), so that the original rock sample would not be further ground and would not be affected by secondary grinding.

[0056] In one embodiment, the content of mobile hydrocarbons is calculated using the following expression:

[0057]

[0058] Where Sm represents the content of mobile hydrocarbons, S1' represents the content of free hydrocarbons, S2' represents the content of pyrolytic hydrocarbons, and P represents the hydrocarbon loss rate.

[0059] For example: based on the above Figure 2 and Figure 3 For the two rock samples, the P values ​​were calculated to be 55.3% and 20.3%, respectively. S1' values ​​were 0.2 mg / g and 1.93 mg / g, respectively; S2' values ​​were 2.14 mg / g and 10.24 mg / g, respectively. Based on the above formula for calculating mobile hydrocarbon content, the Sm values ​​for the two rock samples were estimated to be 3.09 mg / g and 5.03 mg / g, respectively.

[0060] The mobile hydrocarbon Sm index obtained using the mobile hydrocarbon component evaluation method described in this embodiment of the invention is compared with the free hydrocarbon S1 obtained from conventional laboratory powder sample pyrolysis testing (i.e., the ratio of free hydrocarbon Sm to free hydrocarbon S1). Figure 2 and Figure 3 Two rock samples were subjected to routine laboratory powder pyrolysis tests, yielding free hydrocarbon content of 1.24 mg / g and 2.45 mg / g, respectively. Comparison showed increases in free hydrocarbon content of approximately 149% and 105%, respectively. Figure 4 As shown.

[0061] Example 2

[0062] The following uses sample X as an example to evaluate the mobile hydrocarbon components according to the mobile hydrocarbon component evaluation method described in Example 1 above.

[0063] (1) Taking the shale sample X from well Feng 112 in the Dongying Depression of China as an example, 30g of the block sample was soaked in a mortar with a composite organic solvent (ratio of n-hexane / dichloromethane / methanol 40:10:1v / v / v) and ground to the maximum extent to obtain the total hydrocarbon extract H.

[0064] (2) Detection of the total hydrocarbon extract H was performed using gas chromatography-mass spectrometry (GCMS; Agilent 7890A). The test was conducted according to the following key technical parameters: injection was performed using a programmable temperature vaporization injector (PVT); the temperature program settings were: splitless; initial temperature: 20℃; initial time: 0.1 min; heating rate: 1250℃ / min; pressure: 159 kPa; flow rate: 500 mL / min. The chromatographic column was a J&W 122-5562 DB-5ms 60m × 0.25mm × 0.25μm column. The temperature program was 30℃ held for 0.2 min, then increased to 310℃ at a rate of 3℃ / min and held for 40 min. He was used as the carrier gas, with a flow rate set to 1.5 mL / min. Data collection was performed using relevant software.

[0065] (3) Identify all n-alkanes in the total ion current (TIC) mass chromatogram, and perform semi-quantitative calculation of the peak area of ​​the detected n-alkanes using an integration method, for example, those containing C3-C4. 35 The peak area M of the n-alkane chalk. Determine the relative abundance or mass fraction L of the n-alkane (e.g., C2). 17 n-Heptadecane = 4.5% (percentage). Based on the relative molecular mass of the n-alkane (e.g., C). 17 (e.g., n-heptadecane = 240.28) Calculate the molar concentration (i.e., molar concentration) K of each n-alkane in the total hydrocarbon component.

[0066] (4) The natural logarithm of the molar concentration K of each n-alkane was used to calculate the correlation with the number of carbon atoms. The stable slope formula was obtained by taking the data points of the stable segment of the curve (i.e., representing the medium and high molecular weight n-alkanes that are not easily affected). The theoretical mass fraction of the light hydrocarbon component and the theoretical loss ratio P (%) of the n-alkane were calculated.

[0067] (5) Pyrolysis analysis of the broken sample after it was dried in a ventilated area yielded S1' and S2'. The recovered mobile hydrocarbon Sm was calculated to be (S1' + S2') / (100 - P%) - S2'. For example: Figure 3 In this study, the P content of the sample was 20.3%. S1' was 1.93 mg / g, and S2' was 10.24 mg / g. Based on the formula, the Sm content of both samples can be calculated to be 5.03 mg / g. The content of mobile hydrocarbon Sm is approximately 105% higher than that of free hydrocarbon S1 (2.45 mg / g) in conventional laboratory powder sample pyrolysis tests.

[0068] Example 3

[0069] Based on the mobile hydrocarbon component evaluation methods of Embodiments 1 and 2 described above, this invention also provides a system for evaluating mobile hydrocarbon components (also referred to as a "mobile hydrocarbon component evaluation system"). This mobile hydrocarbon component evaluation system is used to implement the above-described mobile hydrocarbon component evaluation methods.

[0070] Figure 5 This is a block diagram of a system for evaluating mobile hydrocarbon components according to an embodiment of this application. Figure 5 As shown, the mobile hydrocarbon component evaluation system described in this embodiment of the invention includes: a total hydrocarbon extract generation module 51, a hydrocarbon loss rate calculation module 52, and a mobile hydrocarbon reduction module 53.

[0071] Specifically, the total hydrocarbon extract generation module 51 is implemented according to the method described in step S110 above, configured to soak the rock sample in a composite organic solvent and grind it thoroughly to obtain the total hydrocarbon extract; the hydrocarbon loss rate calculation module 52 is implemented according to the method described in step S120 above, configured to perform compound detection and analysis on the total hydrocarbon extract, and calculate the hydrocarbon loss rate of the rock sample under laboratory conditions during the transfer from downhole to laboratory conditions based on the analysis results; the movable hydrocarbon reduction module 53 is implemented according to the method described in step S130 above, configured to perform pyrolysis analysis on the dried total hydrocarbon extract to obtain the free hydrocarbon content and pyrolysis hydrocarbon content, and based on this, combined with the hydrocarbon loss rate, obtain the movable hydrocarbon content.

[0072] In one embodiment, the composite organic solvent described in this invention is a mixture of hexane, dichloromethane, and methanol, with the ratio of the three solvents being 40:10:1.

[0073] Furthermore, the movable hydrocarbon reduction module 52 includes: a sample detection unit 521, a n-alkane analysis unit 522, a relation generation unit 523, and a loss rate generation unit 524.

[0074] Specifically, the sample detection unit 521 is configured to obtain the distribution and relative abundance of n-alkanes in the sample based on compound detection and analysis experiments; the n-alkane analysis unit 522 is configured to calculate the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of n-alkanes; the relational expression generation unit 523 is configured to establish a first relational expression characterizing the relationship between the molar concentration of n-alkanes and the number of carbon atoms based on the molar concentration of each n-alkane; and the loss rate generation unit 524 is configured to invert the theoretical mass fraction of unaffected ground-state light hydrocarbons based on the first relational expression to obtain the hydrocarbon loss rate.

[0075] This invention discloses a method and system for evaluating mobile hydrocarbon components. The method and system involve sequentially performing grinding and extraction of rock samples under the protection of a composite organic solvent, identifying compounds, conducting semi-quantitative analysis, and calculating the proportion of light hydrocarbon loss (P). Finally, pyrolysis analysis of the extracted and broken samples yields the lost free hydrocarbons (S1') and pyrolytic hydrocarbons (S2'), and the mobile hydrocarbon (Sm) is determined by combining the loss proportion. This invention provides a simple, scientific, accurate, and effective evaluation of mobile hydrocarbons in geological rock samples, reducing losses caused by the experimental process in mobile hydrocarbon evaluation.

[0076] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0077] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0078] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0079] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0080] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0081] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for evaluating mobile hydrocarbon components, characterized in that, include: Rock samples were soaked in a composite organic solvent and then thoroughly ground to obtain a total hydrocarbon extract. The total hydrocarbon extract was subjected to compound detection and analysis, and the hydrocarbon loss rate under laboratory conditions during the transfer of rock samples from downhole to laboratory conditions was calculated based on the analysis results. The dried total hydrocarbon extract was subjected to pyrolysis analysis to obtain the free hydrocarbon content and the pyrolysis hydrocarbon content. Based on this, and combined with the hydrocarbon loss rate, the mobile hydrocarbon content was obtained.

2. The method according to claim 1, characterized in that, The steps of performing compound detection and analysis on the total hydrocarbon extract and calculating the hydrocarbon loss rate during the transfer of rock samples from downhole to laboratory conditions based on the analysis results include: Based on compound detection and analysis experiments, the distribution and relative abundance of n-alkanes in the samples were obtained; Based on the distribution and relative abundance of the n-alkanes, calculate the molar concentration of each n-alkane in the total hydrocarbon component; Based on the molar concentration of each n-alkane, a first relational expression characterizing the relationship between the molar concentration and the number of carbon atoms of the n-alkane is established. Based on the first relational expression, the theoretical mass fraction of the unaffected ground-state light hydrocarbons is inverted to obtain the hydrocarbon loss rate.

3. The method according to claim 2, characterized in that, The step of establishing a first relational expression characterizing the relationship between the molar concentration and the carbon number of a n-alkane based on the molar concentration of each n-alkane includes: Based on the molar concentration of each n-alkane, a first curve representing the natural logarithm of the molar concentration of the n-alkane as a function of the number of carbon atoms is plotted. The stable segment of the first curve is extracted to form the second curve; The second curve is fitted to obtain the first relational expression.

4. The method according to claim 2 or 3, characterized in that, The step of calculating the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of the n-alkane includes: Based on the distribution and relative abundance of the n-alkanes, the peak areas of the n-alkanes are calculated using the integration method. Based on the peak area calculation results, the relative mass fraction of all n-alkanes is calculated, thereby obtaining the molar concentration of each n-alkane.

5. The method according to any one of claims 1 to 4, characterized in that, The content of movable hydrocarbons is calculated using the following expression: Where Sm represents the content of mobile hydrocarbons, S1' represents the content of free hydrocarbons, S2' represents the content of pyrolytic hydrocarbons, and P represents the hydrocarbon loss rate.

6. The method according to any one of claims 1 to 5, characterized in that, The composite organic solvent is a mixture of n-hexane, dichloromethane, and methanol in a ratio of 40:10:

1.

7. The method according to any one of claims 1 to 6, characterized in that, The compounds in the total hydrocarbon extract are detected and analyzed using total hydrocarbon chromatography or chromatographic mass spectrometry.

8. A system for evaluating mobile hydrocarbon components, characterized in that, include: The whole hydrocarbon extract generation module is configured to soak the rock sample in a composite organic solvent and grind it thoroughly to obtain the whole hydrocarbon extract. The hydrocarbon loss rate calculation module is configured to perform compound detection and analysis on the total hydrocarbon extract, and calculate the hydrocarbon loss rate of the rock sample under laboratory conditions during the transfer from downhole to laboratory conditions based on the analysis results. The movable hydrocarbon reduction module is configured to perform pyrolysis analysis on the dried whole hydrocarbon extract to obtain the free hydrocarbon content and the pyrolysis hydrocarbon content, and based on this, combined with the hydrocarbon loss rate, to obtain the movable hydrocarbon content.

9. The system according to claim 8, characterized in that, The movable hydrocarbon reduction module includes: The sample detection unit is configured to obtain the distribution and relative abundance of n-alkanes in the sample based on compound detection and analysis experiments. The n-alkane analysis unit is configured to calculate the molar concentration of each n-alkane in the total hydrocarbon component based on the distribution and relative abundance of the n-alkane. The relation generation unit is configured to establish a first relational expression characterizing the relationship between the molar concentration and the number of carbon atoms of each n-alkane based on the molar concentration of each n-alkane. The loss rate generation unit is configured to invert the theoretical mass fraction of unaffected ground-state light hydrocarbons according to the first relational expression, thereby obtaining the hydrocarbon loss rate.

10. The system according to claim 8 or 9, characterized in that, The composite organic solvent is a mixture of n-hexane, dichloromethane, and methanol in a ratio of 40:10:1.

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