A method for recovering and evaluating original total organic carbon parameters of source rock based on hydrocarbon generation kinetics

Abstract

The application provides a kind of based on hydrocarbon generation kinetics of source rock original total organic carbon parameter recovery and evaluation method.The method realizes the recovery of residual oil amount by light and heavy hydrocarbon correction, and with the kinetic parameters such as dry kerogen hydrocarbon conversion rate, oil cracking conversion rate and coke generation proportion calibrated by thermal simulation experiment as the constraint, builds the evaluation model of intra-source cracking oil and its material balance formula, restores and evaluates the original S2, intra-source cracking oil amount, coke carbon content and original total organic carbon, and further reveals the mechanism of total organic carbon evolution of first decrease and then increase.This application provides a complete closed-loop framework from experimental calibration to geological parameter recovery, which significantly improves the geological reliability of hydrocarbon source rock resource evaluation.The method overcomes the limitations of traditional methods in the interpretation of total organic carbon evolution in high mature area, improves the accuracy of residual oil amount recovery, and provides a scientific, repeatable and reviewable technical path for hydrocarbon source rock resource evaluation.

Description

Technical Field

[0001] This invention belongs to the field of petroleum geological exploration and geochemical evaluation technology, specifically relating to a method for evaluating geochemical parameters of source rocks. This method uses thermal simulation experiments to calibrate kinetic parameters and combines them with material balance constraints to recover and evaluate the original total organic carbon content, original hydrocarbon generation potential, and residual oil content. This method is particularly suitable for source rocks in the mature to highly mature stages, aiming to solve the technical problems of misunderstanding the evolution mechanism of total organic carbon and systematically underestimating residual hydrocarbon content in traditional exploration and evaluation methods at this stage, providing a complete technical system from experimental calibration to geological parameter evaluation. This method can be widely applied to oil and gas resource exploration and evaluation in marine and continental basins. Background Technology

[0002] In oil and gas resource exploration and source rock geochemical characterization in marine and terrestrial basins, the original total organic carbon (TOC) content and original hydrocarbon generation potential are core parameters determining the accuracy of resource calculations and exploration decisions. This is particularly crucial in deep-water exploration (such as the Pearl River Estuary Basin), where high drilling costs and difficulty in obtaining samples make accurate evaluation of source rock quality paramount. Current techniques generally interpret the evolution of TOC with maturity as a monotonically decreasing, unidirectional consumption process. However, a closed-system gold tube hydrocarbon generation thermal simulation experiment reveals an important phenomenon: when maturity exceeds a certain critical value, TOC content exhibits a significant "rebound" trend. The physical essence of this phenomenon lies in the loss of organic carbon during the initial cracking of kerogen, while the solid coke produced during the secondary cracking of residual crude oil compensates for the carbon conservation, leading to a rebound in TOC at high maturity stages.

[0003] Traditional exploration and evaluation methods often overlook the compensatory contribution of coke formation to total organic carbon (TOC), resulting in generally low recovery values ​​for original TOC in areas with high maturity, severely impacting the accuracy of resource assessment. Furthermore, the S1 parameter in conventional rock pyrolysis analysis only covers volatile components below 300℃. This technical limitation leads to two significant problems: firstly, it ignores the loss of light hydrocarbons, primarily C, during sample storage and pulverization. 1-13 The first issue is the composition of the hydrocarbons. Secondly, it failed to identify high-boiling-point heavy hydrocarbons that only crack at temperatures above 300℃. These heavy hydrocarbons were mistakenly included in the S2 parameter due to the adsorption and swelling of organic matter and the excessively high boiling points of some liquid hydrocarbons. These technical deficiencies lead to a systematic underestimation of residual oil levels, causing significant errors in both geochemical analysis of source rocks and resource assessment, thus impacting geological exploration deployment.

[0004] More importantly, existing technologies lack a complete material balance constraint from "residual oil to cracked oil to raw coke and finally to total organic carbon compensation," making it impossible to establish a correlation between crude oil cracking conversion rate and coke generation. Consequently, the recovery of original parameters lacks sufficient geological reliability. Existing recovery methods are mostly based on empirical formulas derived from laboratory thermal simulation experimental data, neglecting the differences in organic matter kinetic behavior and the impact of hydrocarbon expulsion efficiency on the evolution of total organic carbon.

[0005] Therefore, there is an urgent need for a comprehensive evaluation method based on the principle of material balance and combined with multiple experimental calibrations, which can reveal the true mechanism of total organic carbon evolution and accurately recover the original total organic carbon and residual oil in source rocks of different maturity levels, providing reliable technical support for oil and gas resource exploration and evaluation. Summary of the Invention

[0006] To address the problems in the background art, this invention provides a method for restoring and evaluating the original total organic carbon (TOC) parameters of source rocks based on hydrocarbon generation kinetics. By calibrating the kinetic parameters through conventional pyrolysis, extractive pyrolysis, and gold tube thermal simulation experiments, an evaluation model for source cracked oil is constructed. The amount of coke generated by crude oil cracking and its compensating contribution to TOC are evaluated, thereby achieving accurate restoration and evaluation of the original TOC and revealing the evolution mechanism of TOC shifting from decline to recovery in the high maturity stage.

[0007] The innovation of this invention lies in establishing an evaluation model for in-source cracked oil constrained by material balance, and calibrating key parameters such as crude oil cracking conversion rate and coke generation ratio through thermal simulation experiments, thereby achieving accurate recovery and evaluation of the total organic carbon evolution process.

[0008] The accuracy of residual oil recovery is significantly improved by correcting for light and heavy hydrocarbons; the crude oil cracking conversion rate and coke generation ratio calibrated by the gold tube thermal simulation experiment are introduced to achieve recovery under kinetic constraints; a complete evaluation chain is formed from experimental calibration to residual oil recovery, to cracked oil and coke carbon content calculation, and finally to the recovery of original total organic carbon. The logic is rigorous and the geological applicability is strong.

[0009] The technical solution provided by this invention is:

[0010] A method for restoring and evaluating the original total organic carbon parameters of source rocks based on hydrocarbon generation kinetics includes the following six steps:

[0011] Step 1, Experimental parameter calibration and basic data collection: including five types of experiments: conventional pyrolysis, vitrinite reflectance, extraction pyrolysis, gold tube thermal simulation and solid residue extraction pyrolysis.

[0012] Step 2, Residual Oil Recovery Based on Light and Heavy Hydrocarbon Correction: This step addresses the problem of underestimating residual oil by using light and heavy hydrocarbon correction to restore the original free hydrocarbon S1.

[0013] Step 3: Recovery of the original S2 based on hydrocarbon generation kinetics:

[0014] Step 4, Calculation of carbon content in source-cracked oil and coke: This step constructs and implements a material balance evaluation model for source-cracked oil to determine the material sources of total organic carbon rebound in the high-maturity stage;

[0015] Step 5, Evolution Mechanism and Recovery of Original Total Organic Carbon: Based on the closed-system gold tube hydrocarbon generation thermal simulation experiment, the evolution law of total organic carbon content with Ro during the evolution process was observed, and the original total organic carbon recovery scheme was constructed.

[0016] Step 6: Recovery and comprehensive evaluation of the original hydrogen index.

[0017] The five types of experiments described in step 1 above provide key kinetic parameters and correction coefficients for subsequent parameter recovery:

[0018] (1) Conventional pyrolysis experiments obtain the parameters S1, S2, Tmax, and TOC by analyzing the pyrolysis of rock samples;

[0019] (2) The vitrinite reflectance experiment is to measure Ro of rock samples and establish the relationship between depth and Ro;

[0020] (3) The extraction pyrolysis experiment is to perform pyrolysis analysis on the rock sample before and after chloroform extraction to obtain the parameter values ​​of S1, S2 and S2' after extraction, which are used to calculate the heavy hydrocarbon correction coefficient.

[0021] (4) The gold tube thermal simulation experiment simulated the cleavage of kerogen to generate various components, including C. 1-5 C 6-13 C 14+ The kinetic parameters were calibrated to obtain the activation energy distribution and pre-exponential factor of the reaction of each component. Key parameters such as kerogen hydrocarbon conversion rate, crude oil cracking conversion rate and crude oil cracking coke ratio were calibrated. By setting different temperature-time conditions, the evolution process of different maturity stages was simulated to obtain the values ​​at different evolution stages, and the kinetic constraint relationship of different maturity evolution stages was established accordingly.

[0022] (5) The solid residue extraction and pyrolysis experiment is used to extract and pyrolyze the residue after the gold tube thermal simulation experiment, and further calibrate the correspondence between the residual hydrocarbon generation potential and the total organic carbon at different evolution stages.

[0023] In step 2 above:

[0024] (1) First, heavy hydrocarbon correction is performed: the amount of heavy hydrocarbon correction is the high carbon number alkane and aromatic components of pyrolysis free hydrocarbon S1 that are only cracked after 300℃ and are mistakenly identified as cracked hydrocarbon S2; the amount of heavy hydrocarbon correction S not captured by free hydrocarbon S1 is characterized by comparing the difference of cracked hydrocarbon S2 values ​​obtained by pyrolysis before and after extraction of the same rock sample. 1H ,Right now:

[0025] ;

[0026] (2) Next, light hydrocarbon correction is performed. Based on the hydrocarbon generation component kinetic parameters calibrated in the first step, the evolution process of different maturity stages is simulated by setting different temperature-time conditions, and the proportional relationship of hydrocarbon components generated at different maturity stages is established. In the initial pyrolysis process of the source rock, kerogen is directly pyrolyzed into C 1-5 C 6-13 C 14+ In a closed system, the hydrocarbons generated by kerogen cracking will undergo secondary cracking, C 14+ Crack into C 6-13 and C 1-5 C generated by primary and secondary pyrolysis 6-13 Continue to cleave into C 1-5 During kerogen pyrolysis, the yields of each product change with increasing maturity. Assuming the proportions of hydrocarbons remaining in the source rock are the same as those at formation (i.e., the assumption of equal-proportional hydrocarbon expulsion), the ratios of residual hydrocarbons at different maturity levels are obtained, establishing the Cg... 6-13 / C 14+ The relationship with Easy%Ro can be used to further determine the light hydrocarbon correction amount S. 1L The residual oil content S1 was eventually recovered. 0 :

[0027] .

[0028] In step 3 above, the solid residue after thermal simulation of the gold tube was extracted and analyzed for TOC to determine the content of S2' of the extracted cracked hydrocarbons. Based on the previously calibrated kinetic parameters, the hydrocarbon conversion rate of kerogen was calculated. According to the principle of material balance, i.e., the conservation of total hydrocarbon generation potential, the following relationship was established:

[0029] ;

[0030] ;

[0031] S2 0 S2' represents the original hydrocarbon generation potential, and S2' represents the residual cracking potential after extraction. ken The hydrocarbon conversion rate of kerogen.

[0032] In step 4 above: Based on the principle of material balance, after kerogen in the source rock generates oil, it is divided into two parts: one part is discharged from the source rock, and the other part remains in the source rock. The discharged oil will not continue to participate in the hydrocarbon generation evolution within the source rock, while the residual oil within the source rock continues to evolve and is divided into two parts: one part of the oil is cracked within the source rock, and the other part is not yet cracked. The amount of oil cracked within the source rock is defined as Oil. C Uncracked oil is the residual oil content S1 after correction for light and heavy hydrocarbons. 0 Simultaneously, coke generation was observed during crude oil cracking in the gold tube thermal simulation experiment. Based on hydrocarbon generation kinetics calibration parameters, the crude oil cracking conversion rate X was calculated. OC Coke formation conversion rate X C That is, the following equation holds:

[0033] ;

[0034] ;

[0035] ;

[0036] In the formula, C is the carbon content of coke produced by crude oil cracking; K is the hydrocarbon-to-carbon coefficient, which is used to convert the carbon content of hydrocarbons into the carbon content of coke, and is generally taken as 0.083.

[0037] In step 5 above, the carbon content of coke is deducted as a compensation item for the current value of total organic carbon. Furthermore, there is a corresponding relationship between organic carbon in the source rock organic matter and pyrolysis parameters. Based on the recovered original S2, an original total organic carbon recovery scheme is established, specifically expressed as follows:

[0038] ;

[0039] ;

[0040] The first equation's left side represents the currently measured total organic carbon, and the right side's TOC' represents the total organic carbon after extraction. "S1 + S2 - S2'" represents the total residual oil currently present in the rock that can be identified by pyrolysis or extraction. From the perspective of carbon conservation, this equation holds true. The second equation's left side represents the original total organic carbon, and the right side's "TOC' - C" represents the remaining carbon from the initial kerogen after deducting the carbon content from the coke produced by crude oil cracking. "S2" represents the remaining carbon content from the initial cracking of kerogen. 0 - S2'” represents the amount of hydrocarbon consumed from the initial state to the extraction, and K is the hydrocarbon-to-carbon coefficient, with a value of 0.083.

[0041] In step 6 above: after restoring the original total organic carbon in step 5 above, the original hydrogen index HI is further calculated by comparing the original S2 with the original total organic carbon. 0 The expression is:

[0042]

[0043] By examining the original TOC, S2, and HI recovery coefficients, and comparing and analyzing the types of organic matter before and after recovery, the rationality of the recovered original TOC and original S2 is comprehensively evaluated.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] First, this invention reveals the evolution mechanism of total organic carbon (TOC). Through a material balance model, it clarifies that the rise in TOC during the high maturity stage is caused by the generation of coke from crude oil cracking, thus solving the problem that traditional methods cannot explain the non-monotonic evolution of TOC.

[0046] Secondly, it restored the true residual oil content and, through correction of light and heavy hydrocarbons, overcame the underestimation defect of conventional S1 parameters caused by the volatilization of light hydrocarbons and the adsorption of heavy hydrocarbons.

[0047] Third, the accuracy of recovery was improved by introducing the kerogen hydrocarbon conversion rate, crude oil cracking conversion rate and raw coke ratio calibrated by the gold tube thermal simulation experiment, thus realizing recovery and evaluation under kinetic constraints.

[0048] Fourth, a complete evaluation process for original total organic carbon was established, realizing a closed loop from experimental calibration to residual oil recovery, then to calculation of cracked oil and coke content, and finally to the recovery of original total organic carbon. The process is logically rigorous, geologically applicable, and provides reliable technical support for the assessment of hydrocarbon source rock resources.

[0049] Finally, this method possesses strong geological interpretability, high repeatability, and significantly improves the assessment of source rock resources. Its applicability includes, but is not limited to, geochemical evaluation of highly mature source rocks, thermal history reconstruction, resource calculation, and the study of organic matter evolution processes in geological models. Furthermore, it can be widely applied in different geological zones and bodies by recalibrating relevant parameters. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the method for calculating the original total organic carbon content of the source rock in the embodiments;

[0051] Figure 2 This is a graph showing the relationship between source rock depth and Ro in the examples;

[0052] Figure 3 The diagram shows the relationship between the solid residue S2' and TOC and Ro after thermal simulation of the source rock gold tube in the example.

[0053] Figure 4 This is a chart showing the heavy hydrocarbon correction coefficients for the source rock in the examples;

[0054] Figure 5 This is a chart showing the light hydrocarbon recovery coefficient of the source rock in the examples;

[0055] Figure 6 This is a diagram showing the relationship between source rock S1 and Ro before and after recovery, as illustrated in the example.

[0056] Figure 7 This is a diagram showing the relationship between source rock S2 and Ro before and after recovery, as illustrated in the example.

[0057] Figure 8 This is a diagram of the evaluation model for cracked oil within the source rock in the embodiments;

[0058] Figure 9 This is a graph showing the relationship between the amount of cracked oil and Ro within the source rock in the examples;

[0059] Figure 10 This is a graph showing the relationship between the carbon content of coke produced from the cracking of crude oil in the source rock and Ro in the examples;

[0060] Figure 11 This is a diagram showing the relationship between total organic carbon and pyrolysis parameters of the source rock in the examples;

[0061] Figure 12 The diagram shows the relationship between TOC and Ro in the source rock before and after recovery, as illustrated in the example.

[0062] Figure 13 The diagram shows the relationship between Tmax and HI recovery of the source rock in the example. Detailed Implementation

[0063] The technical solution of this invention is described below with reference to the accompanying drawings. This embodiment uses a source rock sample from the Wenchang Formation in the Pearl River Estuary Depression as an example for data support. This embodiment uses conventional pyrolysis, extractive pyrolysis, and gold tube thermal simulation experiments to calibrate kinetic parameters. Based on the principle of material balance, an evaluation model for in-source cracked oil is constructed to evaluate the amount of coke generated by crude oil cracking and its contribution to total organic carbon (TOC). This achieves accurate recovery and evaluation of the TOC evolution process, demonstrating the recovery effect of parameters such as the original S1, S2, TOC, and hydrogen index. Figure 1 This is a flowchart illustrating the calculation of the original total organic carbon content of the source rock in this embodiment. The specific implementation process includes the following six steps:

[0064] Step 1: Experimental Parameter Calibration and Basic Data Acquisition: Five types of experiments were conducted: conventional pyrolysis, vitrinite reflectance, extraction pyrolysis, gold tube thermal simulation, and solid residue extraction pyrolysis. Through these combined experiments, a set of key parameters for each evolution stage can be obtained, providing accurate input data for subsequent calculations of residual oil, cracked oil, and total organic carbon. Details are as follows:

[0065] (1) The vitrinite reflectance experiment measures Ro in rock samples and establishes the relationship between depth and Ro. Based on the vitrinite reflectance experiment data (see Table 1), the relationship between depth and Ro is established as follows: Results are shown in... Figure 2 .

[0066] Ro = 0.25554 - 0.00000255452 × H + 0.0000000405162 × H 2 .

[0067] In the formula, H is the sample depth, in meters (m). Ro can then be calculated based on the sample depth.

[0068] Table 1. Experimental data on the reflectance of vitrinite

[0069]

[0070] (2) Extraction pyrolysis experiments were conducted on the rock samples, and the data of S1, S2, Tmax, S1', and S2' are shown in Table 2. Among them, Tmax is the temperature corresponding to the peak of the cracked hydrocarbon S2, which reflects the degree of thermal evolution of kerogen, in °C. A correction coefficient for heavy hydrocarbons K was established. H The results are shown in Table 2, which allows for the calculation of heavy hydrocarbon correction amounts for samples not extracted in conventional pyrolysis experiments; the results are shown in Table 2.

[0071] Table 2. Data from the extraction pyrolysis experiment

[0072]

[0073] (3) Select typical kerogen samples, pack them into gold tubes, and simulate pressurization and heating in a closed system. Collect products at different temperature points (corresponding to different Easy%Ro), and analyze C using chromatography-mass spectrometry. 1-5 C 6-13 C 14+ The yields of each component, the results of gold tube thermal simulation, extraction pyrolysis of solid residue, and TOC analysis are shown in Table 3. The curves showing the changes in S2' and TOC with maturity are also shown. Figure 3 As shown, the critical point for TOC recovery is confirmed. It can be seen that TOC drops to its lowest point when EASY%Ro is close to 1, and then total organic carbon begins to recover, providing a basis for subsequent recovery of total organic carbon. Among them, TOC is the total organic carbon content, which is the percentage of the mass of organic carbon in the rock to the total mass of the rock.

[0074] Table 3. Data from closed-system gold tube thermal simulation experiments, solid residue pyrolysis, and TOC experiments.

[0075]

[0076] (4) The hydrocarbon conversion rate of kerogen was obtained by calibration using kinetic analysis software (X). ken ), crude oil cracking conversion rate (X) OC ) and crude oil cracking coke production conversion rate (X C The results are shown in Table 4. (For the specific calibration process, please refer to the Chinese Patent Publication Announcement (CNIPA), [CN121659603A].)

[0077] Table 4 Results of Hydrocarbon Generation Kinetic Calibration Conversion Rate

[0078]

[0079] Step 2: Residual oil recovery based on light and heavy hydrocarbon correction:

[0080] Using the experimental data obtained in step 1, calculate the heavy hydrocarbon correction amount S of the rock sample before extraction. 1H And plot the heavy hydrocarbon correction coefficient chart as follows Figure 4 As shown, this is to calculate the heavy hydrocarbon correction amount for the unextracted sample:

[0081]

[0082]

[0083] In the formula, S1 represents free hydrocarbons, characterizing the content of liquid hydrocarbons generated but not expelled in the rock, in mg / g; S1' represents free hydrocarbons after extraction, characterizing the extremely low volatile heavy hydrocarbons remaining in the residue after chloroform and bitumen extraction, in mg / g; S2 represents the content of cracked hydrocarbons measured by pyrolysis before extraction, in mg / g; S2' represents the content of cracked hydrocarbons measured by pyrolysis after extraction, in mg / g; ∆S2 is the difference in cracked hydrocarbon content between the rock sample before and after extraction, characterizing the heavy hydrocarbon correction amount S. 1H mg / g; K H This is the correction factor for heavy hydrocarbons.

[0084] Simultaneously, based on the gold tube thermal simulation experimental data from step 1, the Ck generated by kerogen pyrolysis at each maturity stage was calculated. 1-5 C 6-13 C 14+ The proportions of hydrocarbons in the source rock are assumed to be the same as those at the time of formation (equal proportion hydrocarbon expulsion assumption), and C is established. 6-13 / C 14+ The relationship between Easy%Ro and the light hydrocarbon correction factor is plotted on a graph as follows. Figure 5 As shown.

[0085] K L = 0.8191 × Ro 2 - 0.3477 × Ro - 0.1184

[0086] In the formula K L Ro is the correction factor for light hydrocarbons, and Ro is the Easy%Ro value corresponding to different temperature points measured in the gold tube thermal simulation experiment. That is, the light hydrocarbon correction factor value corresponding to different Ro values ​​is obtained by fitting the experimental data.

[0087] It should also be noted that the light hydrocarbon correction is performed based on the correction of heavy hydrocarbons after pyrolysis S1, therefore:

[0088]

[0089]

[0090] In the formula, S 1L This is the correction amount for pyrolysis S1 light hydrocarbons.

[0091] Then, the residual oil content S1 is obtained. 0 :

[0092]

[0093] The data used in the S1 light and heavy hydrocarbon correction process are shown in Tables 2 and 3. The established light and heavy hydrocarbon correction scheme can restore the residual oil content in conventional pyrolysis experimental data; see details below. Figure 6 Due to the large amount of conventional pyrolysis data, only the correction results of light and heavy hydrocarbons in the S1 pyrolysis of a single well are shown here, as shown in Table 5.

[0094] Table 5. Correction results of light and heavy hydrocarbons from pyrolysis S1 in Well G.

[0095]

[0096] Step 3: Recovery of the original S2 based on hydrocarbon generation kinetics:

[0097] This step involves extracting and analyzing the solid residue after thermal simulation of the gold tube to determine the extracted cracked hydrocarbon content (S2'). Based on previously calibrated kinetic parameters, the hydrocarbon conversion rate of kerogen is calculated. According to the principle of mass balance, i.e., the conservation of total hydrocarbon generation potential, the following relationship is established:

[0098]

[0099]

[0100] In the formula S2 0 S2' represents the original hydrocarbon generation potential, and S2' represents the cracked hydrocarbons after extraction, characterizing the residual crackable potential. This can be obtained by correcting for the heavy hydrocarbons in S1 through pyrolysis in step 2. X ken The hydrocarbon conversion rate from kerogen is obtained through step 1. That is, the original S2 can be calculated for each conventional pyrolysis data point; a comparison before and after recovery is shown in [link to relevant documentation]. Figure 7This section only shows the original S2 recovery results of a single well, as shown in Table 6.

[0101] Table 6 G well S2 0 TOC 0 HI 0 Recovery Result Data Table

[0102]

[0103] Step 4: Calculation of Carbon Content in Intra-Source Cracking Oil and Coke: Constructing an Intra-Source Cracking Oil Evaluation Model: This step involves constructing an intra-source cracking oil evaluation model, as follows... Figure 8 As shown.

[0104] After kerogen in a source rock generates oil, it splits into two parts: one part is expelled from the source rock, while the other part remains in the source rock without being expelled.

[0105] Oil production = Oil discharge + Oil not discharged;

[0106] The discharged oil will not continue to participate in hydrocarbon generation within the source, while the residual oil within the source continues to undergo hydrocarbon generation, which is divided into two parts: one part of the oil is cracked within the source, and the other part is not yet cracked. The amount of oil cracked within the source is defined as Oil. C Uncracked oil is the residual oil content S1 after correction for light and heavy hydrocarbons. 0 :

[0107] Undischarged oil volume = Source cracked oil volume + Residual oil volume; that is, undischarged oil volume = Oil C + S1 0 ;

[0108] Therefore, the amount of oil cracked within the source can also be expressed as: ;

[0109] The right side of the equation represents the unremoved oil that undergoes crude oil cracking. This unremoved oil continues to evolve within the source; this portion of the cracked oil is defined as in-source cracked oil. In the equation, X... OC The crude oil cracking conversion rate was obtained through gold tube thermal simulation experimental data. Based on the crude oil cracking conversion rate X calibrated in step 1... OC Calculate the amount of oil cracked within the source. C :

[0110] Similarly, the equation can be obtained by rearranging terms:

[0111] ;

[0112] Furthermore, based on the coke formation conversion rate X determined in step 1... C Calculate the carbon content C of the coke produced by crude oil cracking:

[0113]

[0114] Where K is the hydrocarbon-to-carbon conversion factor, with a value of 0.083, used to convert the amount of hydrocarbons in coke production into the amount of carbon. The unit of coke carbon content C is converted to carbon content (%) consistent with TOC. The calculation results are shown below. Figures 9-10 The calculation results of cracked oil volume and coke carbon content in a single well are shown in Table 6.

[0115] Step 5: Evolution mechanism and recovery of original total organic carbon:

[0116] Based on the correspondence between total organic carbon (TOC) and pyrolysis parameters (S1, S2) in source rock organic matter, as follows: Figure 11 As shown, combining S2' obtained in step 2 and S2 calculated in step 3 0 The original TOC recovery scheme is constructed using the carbon content C of coke produced from crude oil cracking calculated in step 4:

[0117]

[0118] In the formula, (TOC'-C) represents the residual carbon content of the kerogen after deducting the carbon content of the coke generated from crude oil cracking, %; (S2) 0 -S2') represents the amount of hydrocarbons consumed from the initial state to the extraction time, in mg / g; TOC' is the total organic carbon content after extraction, which can be calculated using the following formula:

[0119]

[0120] In the formula, TOC is the measured TOC data, %; (S1+S2-S2') represents the total amount of residual oil actually present in the rock, mg / g.

[0121] That is, the original TOC can be obtained for each conventional pyrolysis data point; see the comparison before and after recovery. Figure 12 The original TOC recovery results for a single well are shown in Table 6. The experimental results indicate that the evolution of total organic carbon has clear stage characteristics and is not a single consumption process, but rather the result of the superposition of two continuous processes: primary kerogen cracking and secondary crude oil cracking. Among them, primary cracking dominates the carbon loss in the low to medium maturity stage, while the coke generated by secondary cracking plays a compensatory role in the high maturity stage, causing the total organic carbon to rebound.

[0122] Step 6: Recovery and comprehensive assessment of the original hydrogen index:

[0123] Based on the definition of the hydrogen index, the original hydrogen index HI is calculated using the original S2 calculated in step 3 and the original TOC calculated in step 5. 0 The expression is:

[0124]

[0125] By comparing and analyzing the types of organic matter before and after hydrogen index restoration, the rationality of restoring the original TOC and original S2 can be comprehensively evaluated. Figure 13 As shown, the evaluation results of organic matter types before and after hydrogen index recovery are similar, indicating that the original hydrogen index recovery scheme is credible and the recovery of the original TOC and S2 is reasonable. The original hydrogen index recovery results for a single well are shown in Table 6.

Claims

1. A method for recovering and evaluating the original total organic carbon parameters of source rocks based on hydrocarbon generation kinetics, characterized in that: It includes the following six steps: Step 1, Experimental parameter calibration and basic data collection: including five types of experiments: conventional pyrolysis, vitrinite reflectance, extraction pyrolysis, gold tube thermal simulation and solid residue extraction pyrolysis. Step 2, Residual Oil Recovery Based on Light and Heavy Hydrocarbon Correction: This step addresses the problem of underestimating residual oil by adjusting for light and heavy hydrocarbons. It restores the original free hydrocarbon S1 by adjusting for light and heavy hydrocarbons. Step 3: Recovery of the original cracked hydrocarbon S2 based on hydrocarbon generation kinetics: Step 4, Calculation of carbon content in source-cracked oil and coke: This step constructs and implements a material balance evaluation model for source-cracked oil to determine the material sources of total organic carbon rebound in the high-maturity stage; Step 5, Evolution Mechanism and Recovery of Original Total Organic Carbon: Based on the closed-system gold tube hydrocarbon generation thermal simulation experiment, the evolution law of total organic carbon content with Ro during the evolution process was observed, and the original total organic carbon recovery scheme was constructed. Step 6: Recovery and comprehensive evaluation of the original hydrogen index; In step 2: (1) First, heavy hydrocarbon correction is performed: the amount of heavy hydrocarbon correction is the high carbon number alkane and aromatic components of free hydrocarbon S1 that are only cracked after 300℃ and are mistakenly identified as cracked hydrocarbon S2; the amount of heavy hydrocarbon correction S not captured by free hydrocarbon S1 is characterized by comparing the difference of cracked hydrocarbon S2 values ​​obtained by pyrolysis before and after extraction of the same rock sample. 1H ,Right now: ； Where: S2' represents the residual pyrolysis potential after extraction; (2) Next, light hydrocarbon correction is performed. Based on the hydrocarbon generation component kinetic parameters calibrated in the first step, the evolution process of different maturity stages is simulated by setting different temperature-time conditions, and the proportional relationship of hydrocarbon components generated at different maturity stages is established. In the initial pyrolysis process of the source rock, kerogen is directly pyrolyzed into C 1-5 C 6-13 C 14+ In a closed system, the hydrocarbons generated by kerogen cracking will undergo secondary cracking, C 14+ Crack into C 6-13 and C 1-5 C generated by primary and secondary pyrolysis 6-13 Continue to cleave into C 1-5 During kerogen pyrolysis, the yields of each product change with increasing maturity. Assuming the proportions of hydrocarbons remaining in the source rock are the same as those at formation (i.e., the assumption of equal-proportional hydrocarbon expulsion), the ratios of residual hydrocarbons at different maturity levels are obtained, establishing the Cg... 6-13 / C 14+ The relationship with Easy%Ro can be used to further determine the light hydrocarbon correction amount S. 1L The residual oil content S1 was eventually recovered. 0 : ; In step 4, based on the principle of material balance, after kerogen in the source rock generates oil, it is divided into two parts: one part is discharged from the source rock, and the other part remains in the source rock. The discharged oil will not continue to participate in the hydrocarbon generation evolution within the source rock, while the residual oil within the source rock continues to generate hydrocarbons and is divided into two parts: one part of the oil is cracked within the source rock, and the other part is not yet cracked. The amount of oil cracked within the source rock is defined as Oil. C Uncracked oil is the residual oil content S1 after correction for light and heavy hydrocarbons. 0 Simultaneously, coke generation was observed during crude oil cracking in the gold tube thermal simulation experiment. Based on hydrocarbon generation kinetics calibration parameters, the crude oil cracking conversion rate X was calculated. OC Coke formation conversion rate X C That is, the following equation holds: ； ； ； In the formula, C represents the carbon content of coke produced by crude oil cracking; K is the hydrocarbon-to-carbon conversion coefficient, used to convert the carbon content of hydrocarbons into the carbon content of coke, and is generally taken as 0.083; In step 5, the carbon content of coke is deducted as a compensation item for the current value of total organic carbon. Furthermore, there is a corresponding relationship between organic carbon in the source rock organic matter and pyrolysis parameters. Based on the recovered original S2, an original total organic carbon recovery scheme is established, specifically expressed as follows: ； ； The first equation's left side represents the currently measured total organic carbon, and the right side's TOC' represents the total organic carbon after extraction. "S1+S2-S2'" represents the total amount of residual oil actually existing in the rock that can be identified by pyrolysis or extraction. From the perspective of carbon conservation, this equation holds true. The second equation's left side represents the original total organic carbon, and the right side's "TOC'-C" represents the amount of carbon remaining after the initial pyrolysis of kerogen after deducting the carbon content of coke generated from crude oil cracking. "S2 0 "-S2'" indicates the amount of hydrocarbon consumed from the initial state to the extraction time, and K is the hydrocarbon-to-carbon coefficient, with a value of 0.

083.

2. The restoration and evaluation method according to claim 1, characterized in that: The five types of experiments described in step 1 provide key kinetic parameters and correction coefficients for subsequent parameter recovery: (1) Conventional pyrolysis experiments obtain the parameters S1, S2, Tmax, and TOC by analyzing the pyrolysis of rock samples; (2) The vitrinite reflectance experiment is to measure Ro of the rock sample and establish the relationship between depth and Ro; (3) The extraction pyrolysis experiment is to perform pyrolysis analysis on the rock sample before and after chloroform extraction to obtain the parameter values ​​of S1, S2 and S2' after extraction, which are used to calculate the heavy hydrocarbon correction coefficient. (4) The gold tube thermal simulation experiment was conducted by analyzing the cleavage of kerogen to generate various components, including C. 1-5 C 6-13 C 14+ The kinetic parameters were calibrated to obtain the activation energy distribution and pre-exponential factor of the reaction of each component. Key parameters such as kerogen hydrocarbon conversion rate, crude oil cracking conversion rate and crude oil cracking coke ratio were calibrated. By setting different temperature-time conditions, the evolution process of different maturity stages was simulated to obtain the values ​​at different evolution stages, and the kinetic constraint relationship of different maturity evolution stages was established accordingly. (5) The solid residue extraction and pyrolysis experiment is used to extract and pyrolyze the residue after the gold tube thermal simulation experiment, and further calibrate the correspondence between the residual hydrocarbon generation potential and the total organic carbon at different evolution stages.

3. The restoration and evaluation method according to claim 1, characterized in that: In step 3, the solid residue after thermal simulation of the gold tube was extracted and subjected to TOC analysis to determine the content of S2' of the extracted cracked hydrocarbons. Based on the previously calibrated kinetic parameters, the hydrocarbon generation conversion rate of kerogen was calculated. According to the principle of material balance, i.e., the conservation of total hydrocarbon generation potential, the following relationship was established: ； ； S2 0 X represents the initial hydrocarbon generation potential. ken The hydrocarbon conversion rate of kerogen.

4. The restoration and evaluation method according to claim 1, characterized in that: In step 6: after restoring the original total organic carbon in step 5, the original hydrogen index HI is further calculated using the original hydrocarbon generation potential and the original total organic carbon. 0 The expression is: ； By examining the original TOC, S2, and HI recovery coefficients, and comparing and analyzing the types of organic matter before and after recovery, the rationality of the recovered original TOC and original S2 is comprehensively evaluated.

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