A method for recovering light hydrocarbons from a shale rock pyrolysis experiment hydrocarbon content

Abstract

The present application belongs to the technical field of shale oil resource evaluation, and particularly relates to a light hydrocarbon recovery method for pyrolysis experiment of shale rock, which is based on the test results of the low mature shale sample of the outcrop formation, and a fitting function is constructed among the relative hydrocarbon expulsion efficiency of gaseous hydrocarbon, the gaseous hydrocarbon generation amount, the relative hydrocarbon expulsion efficiency of light hydrocarbon, the light hydrocarbon generation amount and the thermal maturity. Then, the relative hydrocarbon expulsion efficiency of gaseous hydrocarbon, the gaseous hydrocarbon generation amount, the relative hydrocarbon expulsion efficiency of light hydrocarbon, the light hydrocarbon generation amount, the light hydrocarbon loss amount and the light hydrocarbon recovery coefficient of the in-situ shale sample of the formation at the current thermal maturity are obtained. The product of the light hydrocarbon recovery coefficient of the in-situ shale sample of the formation at the current thermal maturity and the thermal release hydrocarbon content of the in-situ shale sample of the formation at the current thermal maturity is the thermal release hydrocarbon content of the in-situ shale sample of the formation under the formation condition. The method is suitable for the analysis and calculation of the light hydrocarbon loss amount of the in-situ shale sample of the formation in a large range, and has engineering application value.

Description

Technical Field

[0001] This invention belongs to the technical field of oil and gas geological exploration and shale oil resource evaluation. Specifically, it relates to a method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of mudstone and shale rocks, and more particularly to a method for recovering light hydrocarbon losses from in-situ mudstone and shale samples with long storage periods, taking into account hydrocarbon expulsion efficiency. Background Technology

[0002] The content of pyrolytic hydrocarbons is a key parameter characterizing the oil-bearing potential of shale oil reservoirs and is of great significance for evaluating shale oil resource potential and deploying shale oil exploration and development. The content of pyrolytic hydrocarbons is obtained by conducting rock pyrolysis experiments on formation mudstone and shale samples, at a pyrolysis temperature of 300℃ and a isothermal time of 3 minutes.

[0003] During the drilling, core storage, sample collection and preparation processes of shale samples, light components (C) from the original hydrocarbon components of the shale formation are present. 1-13 The loss of some or all of the core contents is a phenomenon that is related to various factors such as the core storage time and the sample collection and preparation process. This phenomenon is called light hydrocarbon loss in pyrolytic hydrocarbon content.

[0004] To accurately characterize the oil-bearing properties of mudstone and shale, it is necessary to recover the light hydrocarbon loss from thermally released hydrocarbons.

[0005] Previous researchers have done extensive work on the recovery of light hydrocarbon losses from pyrolysis. From the perspective of light hydrocarbon recovery principles, existing technologies can be broadly categorized into three types: First, by comparing the differences in hydrocarbon composition and content between low-mature samples from stratigraphic outcrops or low-mature samples from hydrocarbon generation kinetic simulations and in-situ mudstone and shale samples, light hydrocarbon recovery can be achieved. Secondly, techniques such as pressure-sealing, frozen sample preparation, and closed pyrolysis are used to minimize the loss of light hydrocarbons in in-situ mudstone and shale samples throughout the entire process of sampling, preservation, preparation, and testing. This allows for comparison with hydrocarbon composition and content obtained through conventional sampling, preservation, preparation, and testing processes, thus enabling the recovery of light hydrocarbons. Third, based on the light hydrocarbon loss pattern of mudstone and shale samples, that is, the relationship between the amount of light hydrocarbon loss of in-situ mudstone and shale samples and the time away from the ground, light hydrocarbon recovery can be achieved.

[0006] Overall, the existing technology analysis and testing process is complex and costly, making it difficult to promote and apply. Summary of the Invention

[0007] This scheme, from the perspective of the thermal evolution of source rocks, posits that during geological history, the thermal evolution of kerogen generates gaseous hydrocarbons, light hydrocarbons, and medium-heavy hydrocarbons. A portion of these hydrocarbons undergoes initial migration and is expelled from the shale, while the remainder remains within the shale. The loss of light hydrocarbons should be considered as the carbon residue remaining after the initial migration and expulsion of the generated hydrocarbons.1-14 Regarding the hydrocarbon component, it is believed that after the in-situ mudstone and shale samples from the local strata were conventionally preserved at the surface for 5 months, the retained C... 1-14 Since all hydrocarbons are lost, a method for obtaining the recovery coefficient of light hydrocarbon loss in pyrolysis experiments of shale and mudstone rocks, taking into account hydrocarbon expulsion efficiency, was constructed.

[0008] The technical solution of this invention is as follows: A method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rocks is as follows: Based on the results of the thermal simulation test of hydrocarbon generation and expulsion of low-mature mudstone and shale samples from the outcrops, a fitting function was constructed to be used to determine the relative expulsion efficiency of gaseous hydrocarbons, the amount of gaseous hydrocarbons generated, the relative expulsion efficiency of light hydrocarbons, the amount of light hydrocarbons generated, and the thermal maturity. Substituting the current thermal maturity of the in-situ mudstone and shale samples into the above fitting function, we obtain the relative hydrocarbon expulsion efficiency, gaseous hydrocarbon generation, relative hydrocarbon expulsion efficiency, and light hydrocarbon generation of the in-situ mudstone and shale samples at the current thermal maturity. The light hydrocarbon loss of in-situ mudstone and shale samples at the current thermal maturity is calculated using the following formula. : (3) The light hydrocarbon recovery coefficient of the in-situ mudstone and shale samples at the current thermal maturity is calculated using the following formula. : (4) The light hydrocarbon recovery coefficient of in-situ mudstone and shale samples at the current thermal maturity Compared with in-situ mudstone and shale samples at the current thermal maturity, the content of thermally released hydrocarbons is... The product of these values ​​represents the thermal hydrocarbon content of the in-situ mudstone and shale sample under formation conditions. In the formula: The light hydrocarbon loss of the in-situ mudstone and shale sample at the current thermal maturity is expressed in mg / g. The relative hydrocarbon expulsion efficiency of gaseous hydrocarbons in in-situ mudstone and shale samples at the current thermal maturity is given in percentages (%). The value represents the amount of gaseous hydrocarbons generated in the in-situ mudstone and shale sample at the current thermal maturity, in mg / g. The relative hydrocarbon expulsion efficiency of light hydrocarbons for in-situ mudstone and shale samples at the current thermal maturity is given in percentages (%). The light hydrocarbon generation of the in-situ mudstone and shale sample at the current thermal maturity is expressed in mg / g. The light hydrocarbon recovery coefficient for in-situ mudstone and shale samples at the current thermal maturity is given, dimensionless. The value represents the thermal hydrocarbon content (mg / g) of the in-situ mudstone and shale sample at its current thermal maturity.

[0009] The calculation process for the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons and the relative hydrocarbon expulsion efficiency of light hydrocarbons is as follows: (1) (2) In the formula: The relative hydrocarbon expulsion efficiency of gaseous hydrocarbons, % This represents the amount of gaseous hydrocarbon transported, in mg / g. The amount of gaseous hydrocarbons produced is expressed in mg / g. The relative hydrocarbon emission efficiency for light hydrocarbons is %; This represents the amount of light hydrocarbon transported, in mg / g. The value represents the amount of light hydrocarbons produced, in mg / g.

[0010] The amount of gaseous hydrocarbon transport Gaseous hydrocarbon generation Light hydrocarbon transport and light hydrocarbon generation The hydrocarbon generation and expulsion products were obtained by gas chromatography analysis of the hydrocarbon generation and expulsion products obtained from thermal simulation experiments on low-maturity mudstone and shale samples from outcrops.

[0011] The in-situ mudstone and shale samples were placed for more than 5 months and were not preserved under pressure, sealed and at low temperature. All gaseous hydrocarbons and light hydrocarbons in the residual hydrocarbons were lost, while medium and heavy hydrocarbons were not lost.

[0012] The thermal hydrocarbon content of the in-situ mudstone and shale samples at the current thermal maturity This was obtained through rock pyrolysis experiments conducted on in-situ mudstone and shale samples from the strata.

[0013] The fitting functions for the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons, the amount of gaseous hydrocarbons generated, the relative hydrocarbon expulsion efficiency of light hydrocarbons, the amount of light hydrocarbons generated, and the thermal maturity are all cubic polynomial fitting functions.

[0014] The technical advantages of this invention are as follows: This invention constructs a method for obtaining the light hydrocarbon loss recovery coefficient in pyrolysis experiments of shale and mudstone, taking into account hydrocarbon expulsion efficiency. It is applicable to the recovery of light hydrocarbon content from pyrolysis experiments of in-situ shale and mudstone samples with long storage periods (greater than 5 months). Compared with existing technologies, the methods significantly reduce the costs of acquisition, preservation, and analysis, simplify the experimental testing methods, and streamline the parameter calculation. This method is suitable for analyzing and calculating the light hydrocarbon loss of in-situ shale and mudstone samples over a wide range of geological formations and has engineering application value. Attached Figure Description

[0015] Figure 1 This is a flowchart of the present invention.

[0016] Figure 2This is a graph showing the fitted relationship between gaseous hydrocarbon production and thermal maturity.

[0017] Figure 3 This is a graph showing the fitting relationship between the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons and thermal maturity.

[0018] Figure 4 This is a graph showing the fitting relationship between the relative hydrocarbon expulsion efficiency of light hydrocarbons and thermal maturity.

[0019] Figure 5 This is a graph showing the fitted relationship between light hydrocarbon production and thermal maturity. Detailed Implementation

[0020] A method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rocks is as follows: Step 1: Conduct a hydrocarbon generation and expulsion thermal simulation experiment on low-maturity mudstone and shale samples from the outcrops of the formation, and use gas chromatography analysis to obtain the amount of gaseous hydrocarbon migration at different thermal maturity levels. Gaseous hydrocarbon generation Light hydrocarbon transport and light hydrocarbon generation ; Step 2: Calculate the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons according to formulas (1) and (2). and relative hydrocarbon expulsion efficiency of light hydrocarbons ; Step 3: Construct the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons Gaseous hydrocarbon generation Relative hydrocarbon expulsion efficiency of light hydrocarbons Light hydrocarbon generation With thermal maturity R o Fitting function between; Step 4: Analyze and test in-situ mudstone and shale samples (stored for more than 5 months without pressure sealing and low-temperature preservation) using rock pyrolysis experiments to determine the current thermal maturity R of the in-situ mudstone and shale samples. o and corresponding pyrolytic hydrocarbon content ; Step 5: Take the thermal maturity R o = Thermal maturity R of in-situ mudstone and shale samples from the stratigraphy o Substituting these values ​​sequentially into the above fitting function, the thermal maturity R of the in-situ mudstone and shale sample at the current stage is calculated. o 'Relative hydrocarbon expulsion efficiency of gaseous hydrocarbons In-situ mudstone and shale samples from the stratigraphy at the current thermal maturity R o 'Gaseous hydrocarbon generation In-situ mudstone and shale samples from the stratigraphy at the current thermal maturity R o 'Relative hydrocarbon emission efficiency of light hydrocarbons and in-situ mudstone and shale samples from the stratigraphy at the current thermal maturity R o Light hydrocarbon generation ; Step 6: Calculate the thermal maturity R of the in-situ mudstone and shale sample at the current stage according to formula (3). o light hydrocarbon loss ; Step 7: Calculate the thermal maturity R of the in-situ mudstone and shale sample at the current stage according to formula (4). o ' light hydrocarbon recovery coefficient ; Step 8: Using in-situ mudstone and shale samples from the strata at the current thermal maturity R o ' light hydrocarbon recovery coefficient Compared with in-situ mudstone and shale samples in the current thermal maturity R o 'pyrolytic hydrocarbon content The product of these values ​​represents the thermal hydrocarbon content of the in-situ mudstone and shale sample under the given formation conditions.

[0021] Specific experimental case – taking the Chang 7 shale in the Ordos Basin as an example, the sample is a low-maturity sample from the Chang 7 Member outcrop in the Tongchuan area.

[0022] Step 1: Conduct a hydrocarbon generation and expulsion thermal simulation experiment on low-maturity samples from the Chang 7 Member outcrops in the Tongchuan area, and use gas chromatography analysis to obtain the amount of gaseous hydrocarbon migration at different thermal maturity levels. Gaseous hydrocarbon generation Light hydrocarbon transport and light hydrocarbon generation The results are as follows: Table 1 Results of Hydrocarbon Generation and Exhaustion Thermal Simulation Experiment and Gas Chromatography Analysis .

[0023] Step 2: Assume that during the initial migration of shale, gaseous hydrocarbons, light hydrocarbons, and medium-heavy hydrocarbons are expelled in a non-equilibrium manner; the relative expulsion efficiency of gaseous hydrocarbons... For gaseous hydrocarbon transport With gaseous hydrocarbon production The ratio; relative hydrocarbon expulsion efficiency of light hydrocarbons Light hydrocarbon transport With light hydrocarbon generation The ratio; the calculation results are shown in Table 2 below: Table 2 Relative hydrocarbon expulsion efficiency of gaseous hydrocarbons and relative hydrocarbon expulsion efficiency of light hydrocarbons Calculation results .

[0024] Step 3: Construct the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons Gaseous hydrocarbon generation Relative hydrocarbon expulsion efficiency of light hydrocarbons Light hydrocarbon generation With thermal maturity R o The fitting functions between them are as follows: ; 98.44 198.56 ; ; .

[0025] Step 4: Define in-situ mudstone and shale samples that have been stored for more than 5 months without pressure-sealed cryopreservation as in-situ mudstone and shale samples; conduct rock pyrolysis experiments to analyze and test the in-situ mudstone and shale samples and determine their current thermal maturity R. o The value is 0.82, corresponding to a thermally released hydrocarbon content. It is 4.39 mg / g.

[0026] Step 5: Transfer R o =R o Substituting '=0.82 into the above fitting function, the thermal maturity R of the in-situ mudstone and shale sample at the current stage is calculated. o 'Relative hydrocarbon expulsion efficiency of gaseous hydrocarbons The percentage was 88.23%, indicating that the in-situ mudstone and shale samples from the strata had a current thermal maturity of R. o 'Gaseous hydrocarbon generation The concentration was 12.26 mg / g, indicating that the in-situ mudstone and shale sample from the formation was at the current thermal maturity R. o 'Relative hydrocarbon emission efficiency of light hydrocarbons The percentage was 47.97%, indicating that the in-situ mudstone and shale samples from the strata had a current thermal maturity of R. o Light hydrocarbon generation It is 20.78 mg / g.

[0027] Step 6: Assuming the in-situ mudstone and shale sample is removed from the ground and not pressurized and sealed at low temperature for 5 months, all gaseous hydrocarbons and light hydrocarbons in the residual hydrocarbons have been lost, while medium and heavy hydrocarbons in the residual hydrocarbons have not been lost. Calculate the thermal maturity R of the in-situ mudstone and shale sample at the current thermal maturity using formula (3). o light hydrocarbon loss It is 12.26 mg / g.

[0028] Step 7: Based on the in-situ mudstone and shale samples from the strata at the current thermal maturity R... o 'pyrolytic hydrocarbon content and in-situ mudstone and shale samples from the stratigraphy at the current thermal maturity R olight hydrocarbon loss Based on formula (4), the in-situ mudstone and shale samples at the current thermal maturity R were calculated. o ' light hydrocarbon recovery coefficient It is 3.79.

[0029] Step 8: Using in-situ mudstone and shale samples from the strata at the current thermal maturity R o ' light hydrocarbon recovery coefficient Compared with in-situ mudstone and shale samples in the current thermal maturity R o 'pyrolytic hydrocarbon content The content of thermally released hydrocarbons in the in-situ mudstone and shale sample under formation conditions was 16.6381 mg / g.

Claims

1. A method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rocks, characterized in that, The method is as follows: Based on the results of the thermal simulation test of hydrocarbon generation and expulsion of low-mature mudstone and shale samples from the outcrops, a fitting function was constructed to be used to determine the relative expulsion efficiency of gaseous hydrocarbons, the amount of gaseous hydrocarbons generated, the relative expulsion efficiency of light hydrocarbons, the amount of light hydrocarbons generated, and the thermal maturity. Substituting the current thermal maturity of the in-situ mudstone and shale samples into the above fitting function, we obtain the relative hydrocarbon expulsion efficiency, gaseous hydrocarbon generation, relative hydrocarbon expulsion efficiency, and light hydrocarbon generation of the in-situ mudstone and shale samples at the current thermal maturity. The light hydrocarbon loss of in-situ mudstone and shale samples at the current thermal maturity is calculated using the following formula. : （3） The light hydrocarbon recovery coefficient of the in-situ mudstone and shale samples at the current thermal maturity is calculated using the following formula. : （4） In the formula: This represents the amount of light hydrocarbons lost by in-situ mudstone and shale samples at the current thermal maturity. The relative hydrocarbon expulsion efficiency of gaseous hydrocarbons in in-situ mudstone and shale samples at the current thermal maturity; This represents the amount of gaseous hydrocarbons generated in in-situ mudstone and shale samples at the current thermal maturity. The relative hydrocarbon expulsion efficiency of light hydrocarbons for in-situ mudstone and shale samples at the current thermal maturity. The amount of light hydrocarbons generated in in-situ mudstone and shale samples at the current thermal maturity; The light hydrocarbon recovery coefficient of in-situ mudstone and shale samples at the current thermal maturity Compared with in-situ mudstone and shale samples at the current thermal maturity, the content of thermally released hydrocarbons is... The product of these values ​​represents the thermal hydrocarbon content of the in-situ mudstone and shale sample under formation conditions. The calculation process for the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons and the relative hydrocarbon expulsion efficiency of light hydrocarbons is as follows: （1） （2） In the formula: This refers to the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons. This refers to the amount of gaseous hydrocarbon transported. This represents the amount of gaseous hydrocarbons produced. The relative hydrocarbon expulsion efficiency for light hydrocarbons; This refers to the amount of light hydrocarbon transported. This represents the amount of light hydrocarbons produced. The in-situ mudstone and shale samples mentioned above are those that have been stored for more than 5 months without pressure-sealing and low-temperature preservation; all gaseous hydrocarbons and light hydrocarbons in their residual hydrocarbons have been lost, while medium and heavy hydrocarbons have not been lost.

2. The method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rock according to claim 1, characterized in that, The amount of gaseous hydrocarbon transport Gaseous hydrocarbon generation Light hydrocarbon transport and light hydrocarbon generation The hydrocarbon generation and expulsion products were obtained by gas chromatography analysis of the hydrocarbon generation and expulsion products obtained from thermal simulation experiments on low-maturity mudstone and shale samples from outcrops.

3. The method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rock according to claim 1, characterized in that, The thermal hydrocarbon content of the in-situ mudstone and shale samples at the current thermal maturity This was obtained through rock pyrolysis experiments conducted on in-situ mudstone and shale samples from the strata.

4. The method for recovering light hydrocarbons from the pyrolysis hydrocarbon content of shale rock according to claim 1, characterized in that, The fitting functions for the relative hydrocarbon expulsion efficiency of gaseous hydrocarbons, the amount of gaseous hydrocarbons generated, the relative hydrocarbon expulsion efficiency of light hydrocarbons, the amount of light hydrocarbons generated, and the thermal maturity are all cubic polynomial fitting functions.

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