Restoration and identification method of original hydrocarbon generation potential of source rock based on thermal simulation experiment

Abstract

The application discloses a kind of based on thermal simulation experiment's hydrocarbon source rock original hydrocarbon generation potential recovery and identification method, the method includes: selecting the dry residue type of sample, and setting initial parameter, sample is pulverized, and the TOC of parallel test sample after pulverization, Ro and rock pyrolysis parameter;Hydrocarbon source rock generation dynamic process is simulated by thermal simulation experiment, and residual sample data testing is carried out;According to residual sample test data, calculate the hydrocarbon generation potential index PHI of each stage of thermal evolution and PHI correction coefficient, and establish the relationship model of PHI and Ro;According to the relationship model established, PHI is taken as the horizontal axis, and Ro is taken as the vertical axis to construct chart, and the hydrocarbon generation potential grade is divided;The TOC of sample to be detected, Ro and PHI are tested, and the original PHI is recovered using PHI correction coefficient, and the hydrocarbon generation potential grade can be determined according to the chart.The application breaks through the limitation of traditional static parameters, can accurately evaluate the original hydrocarbon generation potential of low-maturity hydrocarbon source rock, and is suitable for resource evaluation of unbroken basin or new layer system.

Description

Technical Field

[0001] This invention relates to the field of oil and gas geological exploration technology, and in particular to a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments. Background Technology

[0002] Limitations of traditional methods: Traditional assessments of source rock hydrocarbon generation potential primarily rely on static organic geochemical parameters, including total organic carbon (TOC), rock pyrolysis parameters (S1+S2, Tmax), and maturity indices (Ro or Rb). However, this method is limited in that it can only reflect the organic matter abundance, hydrocarbon generation potential, and thermal evolution of the source rock in its current state, and cannot reconstruct the original hydrocarbon generation potential of the source rock, thus leading to misjudgments of the actual hydrocarbon generation capacity of the source rock.

[0003] Traditional methods for evaluating the hydrocarbon generation potential of source rocks mainly rely on static organic geochemical parameters (such as TOC, S1+S2, Ro), which have the following key drawbacks:

[0004] The model fails to accurately restore the original potential, as it only reflects the current state of the source rock and ignores the dynamic loss of hydrocarbon generation potential during thermal evolution, leading to an underestimation of the original hydrocarbon generation capacity. It also ignores differences in kerogen types, failing to distinguish the differences in hydrocarbon generation kinetics between Type I, II, and III kerogens, resulting in poor applicability of the general model. Furthermore, it has limitations in qualitative evaluation, relying on empirical grading (such as "good" or "poor") and lacking quantitative standards, making it difficult to guide exploration decisions. Finally, it has a narrow applicability range for maturity assessment, with insufficient accuracy in identifying the potential of medium-to-low maturity (Ro = 0.5%–1.6%) source rocks, easily leading to misjudgments of resource potential in unexploited areas.

[0005] Oil and gas exploration in my country is expanding from large basins to medium and small basins, and from basin centers to peripheries and high-altitude areas. Against this backdrop, rapidly identifying the primary hydrocarbon generation potential of medium- and low-maturity source rocks is crucial for reducing exploration risks, saving costs, and ensuring energy security. Current technologies are insufficient to meet this need, necessitating an urgent method for accurately and quantitatively evaluating primary hydrocarbon generation potential. Summary of the Invention

[0006] The purpose of this invention is to provide a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments. This method breaks through the limitations of traditional static parameters and can accurately evaluate the original hydrocarbon generation potential of medium- and low-maturity source rocks. It is applicable to resource evaluation in areas that have not broken through basins or new strata and has the characteristics of high scientific validity and strong operability.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments includes the following steps:

[0009] S1. Select the kerogen type of the sample and set the initial parameters. Crush the sample and then test the TOC, Ro and rock pyrolysis parameters of the sample in parallel.

[0010] S2. In a semi-open high-pressure reactor, a temperature gradient, hydrocarbon discharge pressure, heating rate and isothermal time are set. The dynamic process of hydrocarbon generation from source rocks is simulated through thermal simulation experiments, and residual sample data is tested.

[0011] S3. Calculate the hydrocarbon generation potential index PHI and PHI correction coefficient for each stage of thermal evolution based on the residual sample test data, and establish a relationship model between PHI and Ro.

[0012] S4. Based on the established relationship model, construct a graph with PHI as the horizontal axis and Ro as the vertical axis, label the experimental data points and fitting curves, and classify the hydrocarbon generation potential levels.

[0013] S5. Test the TOC, Ro and PHI of the sample to be tested, use the PHI correction coefficient to recover the original PHI, and plot the original PHI on the chart to determine the hydrocarbon generation potential level.

[0014] Preferably, in S1, the selected sample kerogen type is at least three types selected from type I, type II1, type II2, and type III; the initial parameters set include weight ≥ 1 kg, TOC ≥ 5%, and Ro ≤ 0.7%.

[0015] Preferably, the semi-open high-pressure reactor in S2 is equipped with a temperature control system and a pressure sensor, and the sample chamber is separated from the hydrocarbon discharge channel to simulate real formation hydrocarbon discharge conditions.

[0016] Preferably, the temperature gradient, hydrocarbon expulsion pressure, heating rate, and isothermal time set in S2 are as follows:

[0017] Set more than 10 temperature points to cover the main hydrocarbon generation stage; set the hydrocarbon discharge pressure to 25-70MPa to simulate the fluid pressure environment at different burial depths; set the heating rate to >=20℃ / min and the isothermal time to 72 hours.

[0018] Preferably, establishing the relationship model between PHI and Ro in S3 specifically includes: fitting the relationship curves between PHI and Ro using the least squares method, and finally obtaining the relationship model between PHI and Ro, as follows:

[0019] Ro = a·ln(PHI) + b

[0020] Where a and b are both fitting coefficients.

[0021] Preferably, in S3, the PHI correction coefficient Y is calculated using a piecewise interpolation method, as shown in the following formula:

[0022] (Y1-Y) / (Y1-Y2)=(Ro1-Ro) / (Ro1-Ro2)

[0023] Where Y and Ro are the hydrocarbon generation potential correction coefficient and maturity of the sample to be tested, respectively; Y1 and Y2 are the hydrocarbon generation potential coefficients of the two simulated points; and Ro1 and Ro2 are the hydrocarbon generation maturity values ​​of the two simulated points, respectively, with Ro1≤Ro≤Ro2.

[0024] Preferably, S4 also includes: evaluating the confidence level of the chart through Monte Carlo simulation and correcting outlier data points.

[0025] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments as described above.

[0026] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0027] (1) This invention realizes dynamic evolution simulation. Through multi-temperature point thermal simulation experiments, it reveals the nonlinear variation law of hydrocarbon generation potential of source rocks with maturity. Through piecewise interpolation, it calculates the hydrocarbon generation potential correction system of different types of kerogen, breaking through the time freeze effect of static parameters. This invention constructs a six-level classification standard based on PHI to realize rapid quantitative identification of original hydrocarbon generation potential.

[0028] (2) This invention is universal and scalable, applicable to hydrocarbon source rocks in various sedimentary environments such as terrestrial and marine facies; it can be combined with geophysical data (such as seismic inversion) to predict regional potential. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A flowchart of a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments provided by the present invention;

[0031] Figure 2 A graph showing the relationship between the Hydrocarbon Generation Potential Index (PHI) and maturity (Ro);

[0032] Figure 3 This is a graph showing the relationship between the correction coefficient (Y) for the hydrocarbon generation potential index and maturity (Ro). Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the present invention provides a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments, comprising the following steps:

[0036] S1. Select the kerogen type of the sample and set the initial parameters. Crush the sample and then test the TOC, Ro and rock pyrolysis parameters of the sample in parallel to ensure the accuracy of the data.

[0037] S2. In a semi-open high-pressure reactor, a temperature gradient, hydrocarbon discharge pressure, heating rate and isothermal time are set. The dynamic process of hydrocarbon generation from source rocks is simulated through thermal simulation experiments, and residual sample data is tested.

[0038] S3. Calculate the hydrocarbon generation potential index PHI and PHI correction coefficient for each stage of thermal evolution based on the residual sample test data, and establish a relationship model between PHI and Ro.

[0039] S4. Based on the established relationship model, construct a graph with PHI as the horizontal axis and Ro as the vertical axis, label the experimental data points and fitting curves, and classify the hydrocarbon generation potential levels.

[0040] S5. Test the TOC, Ro and PHI of the sample to be tested, use the PHI correction coefficient to recover the original PHI, and plot the original PHI on the chart to determine the hydrocarbon generation potential level.

[0041] This invention establishes a dynamic identification chart by coupling thermal simulation experiments with the hydrocarbon generation potential index. The specific steps are as follows:

[0042] Step 1: Sample selection and pretreatment

[0043] 1. Sample requirements:

[0044] Kerogen type: At least three types should be selected from Type I (saprophytic), Type II1, Type II2, and Type III (humic) to ensure coverage of the main source rock types.

[0045] Weight: ≥1kg, to prevent insufficient sample representativeness during the experiment.

[0046] Initial parameters: TOC ≥ 5%, Ro ≤ 0.7%.

[0047] 2. Pretreatment:

[0048] Crush into small particles.

[0049] Parallel tests of TOC (GB / T 19145), Ro (SY / T 5124), and rock pyrolysis (SY / T 5118) should be performed, with a relative deviation of less than 5%.

[0050] Step 2: Design of Thermal Simulation Experiments

[0051] 1. Experimental setup:

[0052] It adopts a semi-open high-pressure reactor, equipped with a temperature control system (accuracy ±1℃) and a pressure sensor (range 0-100MPa).

[0053] The sample chamber is separated from the hydrocarbon expulsion channel to simulate real formation hydrocarbon expulsion conditions.

[0054] 2. Experimental parameters:

[0055] Temperature gradient: Set more than 10 temperature points (250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃) to cover the main hydrocarbon generation stage (from liquid window to gas window).

[0056] Pressure conditions: The hydrocarbon discharge pressure is set to 25-70 MPa to simulate the fluid pressure environment at different burial depths.

[0057] Heating rate: >= 20℃ / min, isothermal time: 72 hours (to ensure complete reaction).

[0058] Step 3: Post-experimental parameter testing and index calculation

[0059] 1. Residual sample analysis:

[0060] Test TOC, Ro, S1, S2, etc., and calculate the hydrocarbon generation potential index (PHI = (S1 + S2) / TOC × 100) and the hydrocarbon generation potential index correction coefficient (Y = PHI / PHI) for each stage of thermal evolution. 原始 Based on this, Table 1 is created.

[0061] 2. Data Modeling:

[0062] The relationship curves between PHI and Ro were fitted using the least squares method, and mathematical models for types I, II, and III kerogen were established respectively.

[0063] Ro=a·ln(PHI)+b (1)

[0064] Where a and b are fitting coefficients, reflecting the differences in hydrocarbon generation kinetics among different kerogen types.

[0065] The formula for calculating the hydrocarbon generation potential correction coefficient Y is established using piecewise interpolation:

[0066] (Y1-Y) / (Y1-Y2)=(Ro1-Ro) / (Ro1-Ro2) (2)

[0067] Wherein, Ro1≤Ro≤Ro2, Y and Ro are the hydrocarbon generation potential correction coefficient and maturity of the natural sample to be evaluated, respectively, Y1 and Y2 are the hydrocarbon generation potential coefficients of the two simulated points, and Ro1 and Ro2 are the hydrocarbon generation maturity values ​​of the two simulated points, Ro1≤Ro≤Ro2; Y1, Y2, Ro1, and Ro2 can be found in Table 1 by the hydrocarbon generation potential index correction coefficient based on thermal simulation experiment.

[0068] Table 1

[0069]

[0070] Step 4: Identification, Plate Establishment, and Classification

[0071] 1. Diagram Construction:

[0072] A plate was constructed with PHI (0-600 mg / g TOC) on the horizontal axis and Ro (0-4.0%) on the vertical axis.

[0073] Label the experimental data points and fitted curves, and classify the hydrocarbon generation potential levels:

[0074] Class I (PHI>=600mg / g TOC): Possesses excellent hydrocarbon generation potential and is recommended for priority exploration;

[0075] Category II (400-600 mg / g TOC): Possesses good hydrocarbon generation potential; intensive evaluation is recommended.

[0076] Category III (300-400 mg / g TOC): Has good hydrocarbon generation potential, but needs to be comprehensively evaluated in conjunction with other parameters;

[0077] Category IV (200-300 mg / g TOC): Moderate hydrocarbon generation potential, high economic risk;

[0078] Class V (100-200 mg / g TOC): Poor hydrocarbon generation potential and high economic risk;

[0079] Category VI (PHI <= 100 mg / g TOC): No hydrocarbon generation potential; exploration is not recommended.

[0080] like Figure 2 As shown, the Type I fitting formula is: Y = -0.898ln(x) + 6.0144, R² = 0.966.

[0081] Type II fitting formula: Y = -0.411ln(x) + 3.212, R² = 0.9749

[0082] Type III fitting formula: Y = -0.683ln(x) + 4.6047, R² = 0.9709

[0083] 2. Verification and Optimization:

[0084] The identification chart uses piecewise interpolation to fit the relationship curve between the PHI correction coefficient (Y) and Ro, as shown below. Figure 3 As shown, the confidence level of the chart (95% confidence interval) was evaluated through Monte Carlo simulation, and outlier data points were corrected.

[0085] Step 5: Validation and Application of Natural Samples

[0086] 1. Sample collection:

[0087] Target layers: Selected at equal intervals or in deposition cycles, with ≥5 samples per layer.

[0088] Parameter requirements for natural samples: Ro = 0.5%-1.6%, TOC ≥ 1% (to ensure data validity).

[0089] 2. Experimental Testing and Data Processing:

[0090] For testing natural samples, the relative deviation of the TOC, Ro, rock pyrolysis, and kerogen type should be <5%.

[0091] To ensure the representativeness of the data and the accuracy of the results, data with Ro = 0.5%-1.6% and TOC ≥ 1% were selected, and the mean values ​​of TOC and PHI were calculated.

[0092] 3. Recovery of original hydrocarbon generation potential:

[0093] Based on Equation 2 and the examples of identifying the original hydrocarbon generation potential of some medium- and low-maturity source rocks in Southwest my country in Tables 2-3, correction coefficient (Y) formulas for hydrocarbon generation potential indices corresponding to different kerogen types are established segmentally. For example, the correction coefficient (Y) formulas for Type II kerogen are: Y = 0.88 - 0.8571 * (Ro - 0.70), 0.77 ≥ Ro ≥ 0.70; Y = 0.82 - 0.8947 * (Ro - 0.77), 0.96 ≥ Ro ≥ 0.77; Y = 0.65 - 0.8333 * (Ro - 0.96), 1.50 ≥ Ro ≥ 0.96. Substituting the maturity of the natural samples, the correction coefficients are obtained, thereby restoring the original hydrocarbon generation potential index (mean PHI / correction coefficient).

[0094] Table 2

[0095]

[0096] Table 3

[0097]

[0098]

[0099] 4. Data Plotting and Interpretation:

[0100] By plotting the original hydrocarbon generation potential index and its standard deviation onto the chart, the corresponding category to which the layer belongs can be determined.

[0101] Alternatively, a scatter plotting method can be used. If more than 75% of the samples are located in the same potential range, then the layer is determined to belong to the corresponding category.

[0102] Example 1: Evaluation of source rocks of the Lianggaoshan Formation in the Sichuan Basin

[0103] 1. Geological background: The Lianggaoshan Formation is a Jurassic lacustrine sedimentary formation with an average TOC of 2.18% and Ro = 0.96%, and the kerogen is mainly of type II.

[0104] 2. Results Analysis:

[0105] The correction coefficient calculated according to Equation 2 and Table 1 is 0.650, and the original average PHI value is 766.93 mg / gTOC. It is determined that this layer belongs to Class I with excellent hydrocarbon generation potential, which is consistent with the current exploration reality.

[0106] Example 2: Evaluation of source rocks of the Buqu Formation in the Shenglihe area of ​​the Qiangtang Basin

[0107] 1. Geological background: The Shenglihe area of ​​the Qiangtang Basin has high-quality black mudstone of the Buqu Formation with an average TOC of 4.10% and Ro = 1.07%. The kerogen is mainly of type II1.

[0108] 2. Results Analysis:

[0109] The correction coefficient calculated according to Equation 2 and Table 1 is 0.558, and the original average PHI value is 564.48 mg / g TOC. It is identified as a Class II high-quality source rock and is recommended as a key stratum for the next exploration.

[0110] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments as described above.

[0111] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0112] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments, characterized in that, Includes the following steps: S1. Select the kerogen type of the sample and set the initial parameters. Crush the sample and then test the TOC, Ro and rock pyrolysis parameters of the sample in parallel. S2. In a semi-open high-pressure reactor, a temperature gradient, hydrocarbon discharge pressure, heating rate and isothermal time are set. The dynamic process of hydrocarbon generation from source rocks is simulated through thermal simulation experiments, and residual sample data is tested. S3. Calculate the hydrocarbon generation potential index PHI and PHI correction coefficient for each stage of thermal evolution based on the residual sample test data, and establish a relationship model between PHI and Ro. S4. Based on the established relationship model, construct a graph with PHI as the horizontal axis and Ro as the vertical axis, label the experimental data points and fitting curves, and classify the hydrocarbon generation potential levels. S5. Test the TOC, Ro and PHI of the sample to be tested, use the PHI correction coefficient to recover the original PHI, and plot the original PHI on the chart to determine the hydrocarbon generation potential level. The establishment of the relationship model between PHI and Ro in S3 specifically includes: fitting the relationship curves between PHI and Ro using the least squares method, and finally obtaining the relationship model between PHI and Ro, as follows: Ro = a·ln(PHI) +b; Where a and b are both fitting coefficients; The PHI correction coefficient is calculated using piecewise interpolation in S3. Y The formula is as follows: ( Y1 - Y ) / ( Y1 - Y 2)=(Ro1-Ro) / (Ro1-Ro2) ; in, Y Ro and are the correction factor for the hydrocarbon generation potential and maturity of the sample to be tested, respectively. Y1 , Y2 Ro1 and Ro2 are the hydrocarbon generation potential coefficients of the two simulated sites, respectively, and Ro1 and Ro2 are the growth maturity values ​​of the two simulated sites, respectively, with Ro1≤Ro≤Ro2.

2. The method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments according to claim 1, characterized in that, In step S1, the selected sample kerogen type is at least three types selected from type I, type II1, type II2, and type III; the initial parameters set include weight ≥ 1 kg, TOC ≥ 5%, and Ro ≤ 0.7%.

3. The method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments according to claim 1, characterized in that, The semi-open high-pressure reactor in S2 is equipped with a temperature control system and a pressure sensor, and the sample chamber is separated from the hydrocarbon discharge channel to simulate real formation hydrocarbon discharge conditions.

4. The method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments according to claim 1, characterized in that, The temperature gradient, hydrocarbon expulsion pressure, heating rate, and isothermal time set in S2 are as follows: Set more than 10 temperature points to cover the main hydrocarbon generation stage; set the hydrocarbon discharge pressure to 25-70MPa to simulate the fluid pressure environment at different burial depths; set the heating rate to >=20℃ / min and the isothermal time to 72 hours.

5. The method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments according to claim 1, characterized in that, S4 also includes: evaluating the confidence level of the chart through Monte Carlo simulation and correcting outlier data points.

6. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements a method for restoring and identifying the original hydrocarbon generation potential of source rocks based on thermal simulation experiments, as described in any one of claims 1 to 5.

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