CN113970512B - Method for determining free hydrocarbon enrichment pore size range - Google Patents
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- 238000001179 sorption measurement Methods 0.000 claims description 27
- 229910052757 nitrogen Inorganic materials 0.000 claims description 24
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 22
- 229910052753 mercury Inorganic materials 0.000 claims description 22
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- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 10
- 239000005416 organic matter Substances 0.000 claims description 9
- 239000010779 crude oil Substances 0.000 claims description 5
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
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Abstract
The application discloses a method for determining a free hydrocarbon enrichment pore size range, and relates to the field of shale oil enrichment mechanisms. The method comprises the following steps: obtaining a shale sample, and preparing a core column; rock pyrolysis experiments are carried out on the core column, and an S1 value representing the free hydrocarbon content of the core column is obtained; acquiring accumulated pore volumes corresponding to different pore size ranges representing the core column; for any one of the pore size ranges, analyzing the correlation of the S1 value and the cumulative pore volume corresponding to the pore size range; the free hydrocarbon enriched pore size range is determined based on the correlation. According to the method provided by the embodiment of the application, the relation between the S1 value and the accumulated pore volume corresponding to different pore diameter ranges is established, and the free hydrocarbon enrichment pore diameter range is determined through correlation analysis, so that the free hydrocarbon enrichment pore diameter range is accurately obtained.
Description
Technical Field
The application relates to the field of shale oil enrichment mechanisms, in particular to a method for determining a free hydrocarbon enrichment pore size range.
Background
With the continuous and rapid development of economy, the demand for energy is growing, and unconventional energy sources represented by shale oil are important fields for the successor of future oil and gas resources.
Free hydrocarbons may be used to measure the content of mobile shale oil, and one key point in the research of shale oil enrichment mechanism is to determine the enrichment pore size range of the free hydrocarbons corresponding to the shale oil in free form due to the potential availability of the shale oil in free form.
How to determine the free hydrocarbon enrichment pore size range, the related art has not provided a better solution.
Disclosure of Invention
The embodiment of the application provides a method for determining a free hydrocarbon enrichment pore diameter range, which establishes a relation between an S1 value representing the content of free hydrocarbon and accumulated pore volumes corresponding to different pore diameter ranges, and determines the free hydrocarbon enrichment pore diameter range through correlation analysis, so that the free hydrocarbon enrichment pore diameter range is accurately obtained. The technical scheme is as follows:
According to one aspect of the present application there is provided a method of determining a free hydrocarbon enriched pore size range, the method comprising:
obtaining a shale sample, and preparing a core column;
Rock pyrolysis experiments are carried out on the core column, and an S1 value representing the free hydrocarbon content of the core column is obtained;
acquiring accumulated pore volumes corresponding to different pore size ranges representing the core column;
For any one of the pore size ranges, analyzing the correlation of the S1 value and the cumulative pore volume corresponding to the pore size range;
the free hydrocarbon enriched pore size range is determined based on the correlation.
Optionally, the acquiring represents cumulative pore volume over different pore size ranges of the core column, including:
Performing a low-temperature nitrogen adsorption experiment on the core column to obtain accumulated pore volumes corresponding to different pore size ranges within a first pore size range;
and carrying out a high-pressure mercury injection experiment on the core column to obtain accumulated pore volumes corresponding to different pore size ranges within a second pore size range.
Optionally, the correlation includes: positive correlation or negative correlation.
Optionally, the correlation is characterized by a decision coefficient, and the determining the free hydrocarbon enriched pore size range based on the correlation comprises:
determining that the correlation belongs to the positively correlated aperture range;
and determining the pore diameter range with the largest determining coefficient as the free hydrocarbon enrichment pore diameter range in the pore diameter range with the correlation belonging to the positive correlation.
Optionally, the first aperture range includes: pore size range of 2-50 nm.
Optionally, the second aperture range includes: pore size range of 5-10000 nm.
Optionally, the method further comprises: and extracting organic matters from the core column.
Optionally, the solvent used for extracting the organic matter is chloroform, and the duration of extracting the organic matter is not less than 72 hours.
Optionally, the method further comprises: and heating the core column after the organic matter extraction.
Optionally, the heating is performed under vacuum conditions at a temperature higher than 100 ℃, and the duration of the heating is not less than 12 hours.
The technical scheme provided by the embodiment of the application has the beneficial effects that at least:
S1 value representing free hydrocarbon content of the unextracted shale sample is obtained through rock pyrolysis experiments, the relation between the S1 value and accumulated pore volumes corresponding to different pore size ranges is established, and the free hydrocarbon enrichment pore size range is determined through correlation analysis, so that the free hydrocarbon enrichment pore size range is accurately obtained.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for determining a free hydrocarbon enrichment pore size range provided by an exemplary embodiment of the application;
FIG. 2 is a flow chart of a method for determining a free hydrocarbon enrichment pore size range provided by an exemplary embodiment of the application;
FIG. 3 is a flow chart of a method for determining a free hydrocarbon enrichment pore size range provided by an exemplary embodiment of the application;
FIG. 4 is a schematic representation of a correlation analysis of S1 values with cumulative pore volume provided by an exemplary embodiment of the present application;
FIG. 5 is a schematic representation of a correlation analysis of S1 values with cumulative pore volume provided by an exemplary embodiment of the present application;
FIG. 6 is a schematic representation of a correlation analysis of S1 values with cumulative pore volume provided by an exemplary embodiment of the present application;
FIG. 7 is a schematic representation of a correlation analysis of S1 values with cumulative pore volume provided by an exemplary embodiment of the present application;
FIG. 8 is a schematic representation of a correlation analysis of S1 values with cumulative pore volume provided by an exemplary embodiment of the present application;
FIG. 9 is a schematic diagram of a correlation analysis of S1 values and cumulative pore volume provided by an exemplary embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application will be described in further detail with reference to the accompanying drawings.
References herein to "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.
The world petroleum industry is crossing from regular oil and gas to unconventional oil and gas. Unconventional oil and gas mainly comprises dense oil and gas, shale oil and gas, natural gas hydrate, oil sand, oil shale and the like. Tight oil and gas are oil and gas that are stored in reservoirs such as tight sandstone or limestone, where the oil and gas undergoes short distance migration. Shale oil and gas refer to oil and gas enriched in organic-rich black shale formations, with the oil and gas undergoing substantially no migration process.
Shale oil refers to liquid hydrocarbon which is endowed in various modes such as a free state, an adsorption state, a dissolution state and the like in organic matter-rich shale stratum, and the shale stratum is a source rock for generating the liquid hydrocarbon and can be still in an oil production state, and belongs to a typical self-generated and self-stored in-situ aggregated oil gas type.
Free shale oil is potentially recoverable, while other shale oils in a rich state (e.g., adsorbed shale oil) are almost motionless and less recoverable.
The free hydrocarbon is a localization parameter, and the determination of the occurrence state of the free hydrocarbon and the enrichment pore size range of the free hydrocarbon is critical to the research on the shale oil enrichment mechanism. The present application aims to investigate the enriched pore size range of free hydrocarbons corresponding to shale oil in the free state.
Compared with the conventional reservoir, the shale oil has the characteristics of compact reservoir and extremely strong heterogeneity, and the shale oil reservoir mainly consists of nanoscale pores, so that the free hydrocarbon enrichment pore size range of the shale oil reservoir is difficult to determine.
In the related art, a method of determining the pore size range for enrichment of free hydrocarbons using a gas adsorption method (carbon dioxide and nitrogen) is proposed. And (3) carrying out a gas adsorption experiment by adopting a gas adsorption method to obtain the pore size distribution characteristics of shale before and after extraction, and analyzing the pore size distribution characteristics of shale before and after extraction to determine the free hydrocarbon enrichment pore size range. On the one hand, since extraction also extracts shale oil in dissolved and adsorbed states, the resulting pore size range does not correspond exactly to shale oil in free state. On the other hand, the gas adsorption experiment is only suitable for determining mesopores and micropores with the pore diameter range of less than 50nm, and the experimental study shows that shale oil is mainly enriched in macropores with the pore diameter of more than 50nm, so that a specific pore diameter distribution range is not given.
In the related art, a method for determining the pore size range of free hydrocarbon enrichment by using nuclear magnetic resonance experiments is also provided. And (3) measuring T2 spectrums of crude oil/water shale samples with different saturation degrees by adopting a nuclear magnetic resonance experiment, and obtaining the oil-containing pore size distribution characteristics by using a difference spectrum method. However, the method results in a pore size distribution range of the saturated oil, not the original oil-containing pore size distribution range. Under the condition that the experimental result corresponds to saturated water, the saturated water is easy to hydrate, the rock property is changed, and the accurate oil-containing pore size distribution cannot be obtained.
According to the application, an S1 value representing the free hydrocarbon content of an unextracted sample is obtained through a rock pyrolysis experiment, the accumulated pore volumes of different pore diameters of the shale sample are obtained through a low-temperature nitrogen adsorption experiment and a high-pressure mercury injection experiment, the correlation analysis is carried out on the S1 value and the accumulated pore volumes, and finally the free hydrocarbon enrichment pore diameter range is determined.
The method for determining the pore size range for enriching free hydrocarbons according to the present application will be exemplarily described.
FIG. 1 shows a flow chart of a method for determining a free hydrocarbon enrichment pore size range according to an exemplary embodiment of the application, the method comprising:
Step 110, obtaining a shale sample, and preparing a core column.
Shale is a product of the type of transitional rock between mudstone and shale, typically a semi-deep lake and deep lake sediments. The shale sample is a sample made of shale.
Optionally, the shale sample is a lake phase shale sample. The lake phase refers to sedimentary phases occurring in lake areas. The sedimentary phase is the sum of the formation environment, the formation condition and the characteristics of the sediments, and is mainly dependent on the formation environment of the shale.
The petroleum resources contained in shale may be referred to as shale oil. Shale oil can be classified into three categories depending on occurrence status: 1) Free state; 2) The adsorption state exists mainly in organic matter pores, flocculation inter-crystal pores and pyrite inter-crystal pores and is attached to the organic-clay compound and the metal-organic compound; 3) In a dissolved state, the dissolved state is present in the pore throat fluid. Because of the potential availability of shale oil in the free state, embodiments of the present application are directed to the investigation of shale oil in the free state.
The core column is a column body obtained by drilling a shale sample. Various properties of the shale samples can be determined by the core column. Illustratively, the core column has a diameter of 2.5cm.
And 120, performing rock pyrolysis experiments on the core column to obtain an S1 value representing the free hydrocarbon content of the core column.
The rock pyrolysis experiment is an experimental process for raising the temperature of the core column so as to discharge hydrocarbon substances, and then detecting the hydrocarbon substances by a detector so as to obtain rock pyrolysis analysis parameters.
The rock analysis pyrolysis parameters include an S1 value. The S1 value represents the free hydrocarbon content in the shale per unit mass. The unit of S1 value is mg/g.
Optionally, other rock pyrolysis analysis parameters such as an S0 value, an S2 value, an S4 value and the like may also be obtained through a rock pyrolysis experiment, which is not limited in the embodiment of the present application.
At step 130, cumulative pore volumes corresponding to different pore size ranges representing the core column are obtained.
And carrying out at least one experiment on the core column, determining a plurality of pore size ranges, and counting the accumulated pore volumes respectively corresponding to the pore size ranges. The unit of cumulative pore volume for the pore size range is cm 3/g.
The shale has complex pore structure and wide pore size distribution, and contains not only micron-sized cracks, but also a large number of nano-sized pores. In general, pore size structures are divided into 3 general categories: macropores (i.e., macropores), mesopores (i.e., mesopores), and micropores. Wherein the aperture of the macropores is more than 50 nanometers, the aperture of the mesopores is in the range of 2 nanometers to 50 nanometers, and the aperture of the micropores is less than 2 nanometers.
Alternatively, the pore size range studied may correspond to a partitioning criterion of the pore size structure when acquiring cumulative pore volumes corresponding to different pore size ranges representing the core column. That is to say: the different pore size ranges may include at least one of: a pore size range corresponding to Yu Hongkong, a pore size range corresponding to mesopores, and a pore size range corresponding to micropores. Optionally, the pore diameter range of the macro pore is larger, and the pore diameter range of the macro pore is larger than 50 nanometers and can be further divided into a plurality of sub-ranges which belong to the pore diameter range of the macro pore.
In the embodiment of the present application, the implementation sequence of step 120 and step 130 is not limited: step 120 may be performed first, step 130 may be performed first, or step 120 and step 130 may be performed simultaneously.
Optionally, the above steps 110 to 130 are repeated to obtain sufficient data.
Step 140, for any pore size range, analyzing the correlation of the S1 value and the cumulative pore volume corresponding to the pore size range.
Correlation analysis refers to analyzing two or more variable elements with correlation, so as to measure the correlation degree of the two variable elements. In the embodiment of the application, analysis is performed on two variable elements, namely an S1 value and an accumulated pore volume corresponding to a pore size range.
Step 150, determining a free hydrocarbon enriched pore size range based on the correlation.
After performing the correlation analysis, a free hydrocarbon enriched pore size range is determined based on at least two correlation analysis results of the cumulative pore volume of the S1 values corresponding to the different pore size ranges.
In summary, according to the method provided by the embodiment, the S1 value representing the free hydrocarbon content of the unextracted shale sample is obtained through the rock pyrolysis experiment, the relation between the S1 value and the cumulative pore volume corresponding to different pore size ranges is established, and the free hydrocarbon enrichment pore size range is determined through the correlation analysis, so that the free hydrocarbon enrichment pore size range is accurately obtained.
Meanwhile, according to the method provided by the embodiment, the free hydrocarbon enrichment pore size range is determined through correlation analysis, instead of analyzing the pore size distribution characteristics after extraction in advance to determine the free hydrocarbon enrichment pore size range, and the problem that extraction leads to inaccurate analysis of the free hydrocarbon content is avoided.
In an alternative embodiment based on fig. 1, cumulative pore volumes for different pore size ranges of shale samples were obtained by low temperature nitrogen adsorption experiments and high pressure mercury intrusion experiments.
FIG. 2 illustrates a flow chart of a method for determining a free hydrocarbon enrichment pore size range provided by an exemplary embodiment of the application. In this embodiment, step 130 is alternatively implemented as step 131 and step 132, and the method includes:
Step 110, obtaining a shale sample, and preparing a core column.
The implementation of this step may refer to the above-mentioned examples, and will not be described herein.
And 120, performing rock pyrolysis experiments on the core column to obtain an S1 value representing the free hydrocarbon content of the core column.
Alternatively, rock pyrolysis experiments were performed on the core column, and S1 values representing the free hydrocarbon content of the core column were obtained when heated to 300 ℃.
And 131, performing a low-temperature nitrogen adsorption experiment on the core column to obtain accumulated pore volumes corresponding to different pore size ranges within a first pore size range.
The low-temperature nitrogen adsorption experiment is an experiment process of using nitrogen as an adsorbate to enable nitrogen molecules to be adsorbed on the surface of a powder sample of a core column to be detected, and evaluating the specific surface of the core column to be detected and the adsorption size of pores according to the adsorption amount. Since adsorption is required at liquid nitrogen temperature, it is called a low temperature nitrogen adsorption experiment. Alternatively, "cryogenic" refers to a liquid nitrogen temperature below-196 degrees celsius. It will be appreciated that the liquid nitrogen temperature may also be Yu Lingxia degrees celsius higher under pressure.
Optionally, the first aperture range includes: pore size range of 2-50 nm. Namely: and obtaining the accumulated pore volume corresponding to different pore size ranges within the pore size range of 2-50nm by performing a low-temperature nitrogen adsorption experiment.
Illustratively, a low-temperature nitrogen adsorption experiment is performed on the core column to obtain a cumulative pore volume corresponding to 2-5nm and a cumulative pore volume corresponding to 5-20 nm. Wherein, 2-5nm and 5-20nm correspond to mesopores.
And 132, performing a high-pressure mercury injection experiment on the core column to obtain accumulated pore volumes corresponding to different pore size ranges within a second pore size range.
The high-pressure mercury injection experiment refers to an experimental process of measuring the quantity of mercury in the inlet holes under different external pressures to know the pore volume of the corresponding hole size based on the principle that mercury has non-wettability to the solid surface, the larger the external pressure is needed to be applied to the mercury inlet holes, and the smaller the pore radius into which the mercury can enter. Alternatively, "high pressure" refers to the presence of a maximum mercury intrusion pressure of about 200Mpa.
Optionally, the second aperture range includes: pore size range of 5-10000 nm. Namely: and obtaining the accumulated pore volume corresponding to different pore size ranges within the pore size range of 5-10000nm by performing a high-pressure mercury experiment.
Illustratively, a high-pressure mercury injection experiment is performed on the core column to obtain a cumulative pore volume corresponding to 5-50nm, a cumulative pore volume corresponding to 50-100nm, a cumulative pore volume corresponding to 100-1000nm, and a cumulative pore volume corresponding to 1000-10000 nm. Wherein 5-50nm corresponds to mesopores, 50-100nm, 100-1000nm and 1000-10000nm corresponds to Yu Hongkong.
Optionally, before step 131 or step 132, the method further includes the following steps: and extracting organic matters from the core column. The purpose of organic matter extraction is to ensure that crude oil in a sample is sufficiently removed, and the reliability of experimental results is ensured. Optionally, the solvent used for extracting the organic matters is chloroform, and the duration of extracting the organic matters is not less than 72 hours.
Optionally, after the organic matter extraction, the method further comprises the following steps: and heating the core column. The purpose of heating is to ensure that the moisture in the sample is sufficiently removed, and the reliability of the experimental result is ensured. Alternatively, the heating is performed at a temperature higher than 100deg.C under vacuum, and the heating duration is not less than 12 hours.
Step 140, for any pore size range, analyzing the correlation of the S1 value and the cumulative pore volume corresponding to the pore size range.
Optionally, the correlation includes: positive and negative correlations. Where positive correlation refers to the fact that two variable elements are proportional, if one variable element increases, the other variable element increases, and if one variable element decreases, the other variable element also decreases. Negative correlation refers to the fact that the two variable elements are inversely proportional. If one variable element increases, the other variable element decreases, and if one variable element decreases, the other variable element increases.
Step 150, determining a free hydrocarbon enriched pore size range based on the correlation.
The pore size range corresponding to the positive correlation of the S1 value and the cumulative pore volume is the free hydrocarbon enriched pore size range.
Optionally, step 150 includes: determining that the correlation belongs to a positively correlated aperture range; among the pore size ranges whose correlation belongs to the positive correlation, the pore size range in which the determination coefficient is largest is determined as the free hydrocarbon-enriched pore size range.
Where the decision coefficient (also called decision coefficient) refers to the ratio of the sum of squares of the regression interpretable dispersion to the sum of squares of the total dispersion in linear regression, the value of which is equal to the square of the correlation coefficient R. The value range of the decision coefficient is 0 to 1. When the correlation belongs to positive correlation, the larger the decision coefficient is, the stronger the correlation of the two variable elements is indicated. In the case where there are a plurality of pore size ranges in which the correlation belongs to the positive correlation, the determination coefficients between the two variable elements are compared, and the pore size range in which the determination coefficient is largest is determined as the free hydrocarbon enriched pore size range.
In summary, according to the method provided in this embodiment, since the experiment determines that the pore volumes of different apertures have a certain application range, for example, the low-temperature nitrogen adsorption experiment is applicable to mesopores of 2-50nm, the high-pressure mercury injection experiment is applicable to mesopores of nano-scale and macropores of micro-scale, so that an experimental means of combining low-temperature nitrogen adsorption and high-pressure mercury injection is provided, the total aperture represents the micron-scale and nano-scale accumulated pore volume of the lake-phase shale, the correlation analysis is performed on the S1 value and the accumulated pore volume, and the free hydrocarbon enrichment aperture range is finally determined.
According to the method provided by the embodiment, the core column is pretreated before the low-temperature nitrogen adsorption experiment and the high-pressure mercury injection experiment: and the core column is subjected to organic matter extraction and then heating so as to avoid the influence of crude oil and water on the experiment and ensure the accuracy of the experimental result.
An exemplary method of determining the pore size range for free hydrocarbon enrichment as shown in the present application is described below with reference to FIG. 3. The method comprises the following steps:
Step 301, obtaining a Hunan shale sample.
16 Samples of Hunan shale were obtained.
Step 302, preprocessing is performed.
Cleaning the surface of the lake phase shale samples, drilling and extracting the 16 lake phase shale samples to prepare 16 core columns. For any one of the 16 core columns, the core column is cut into 3 sections, each numbered A, B, C.
Alternatively, the core column has a diameter of 2.5cm.
In step 303, rock pyrolysis experiments are performed.
Sample A was ground to 80-100 mesh and rock pyrolysis experiments were performed on the ground sample A. Alternatively, rock pyrolysis experiments were performed using a Rock-Eval-6 Plus green oil Rock analyzer, according to the GB/T18602-2012 standard.
Step 304, a free hydrocarbon content S1 value is obtained.
Alternatively, the S1 value representing the free hydrocarbon content is obtained at 300 ℃.
In step 305, chloroform extraction is performed.
And extracting the organic matters from the sample B, C by using an organic solvent. The solvent adopted for extracting the organic matters is chloroform, the extraction mode is a Soxhlet extraction method, and the extraction time lasts for more than 72 hours, so that the crude oil in the sample is ensured to be sufficiently removed.
At step 306, a low temperature nitrogen adsorption experiment is performed.
Crushing the extracted sample B to 80-100 meshes, heating at 105 ℃ for more than 12 hours under a vacuum state to sufficiently remove water, and performing a low-temperature nitrogen adsorption experiment on the crushed sample B. Alternatively, the cryogenic nitrogen adsorption experiment was performed using an ASAP 2460 specific surface area/pore size analyzer, according to GB.T 19587-2004 standard.
Alternatively, the temperature of the low temperature nitrogen adsorption experiment is-195.70 ℃, and the relative pressure is 0.005-1.0Mpa (absolute pressure is 0.0006-0.1112 Mpa).
Step 307, obtaining the cumulative pore volume of the 2-50nm aperture.
The cumulative pore volume in the pore size range of 2-50nm was determined using the BJH (Barrett-Joyner-Halenda) model.
Step 308, performing a high pressure mercury injection experiment.
And heating the extracted sample C for more than 12 hours at 105 ℃ in a vacuum pumping state so as to sufficiently remove water, and carrying out a high-pressure mercury-pressing experiment on the crushed sample C. Alternatively, high pressure mercury experiments were performed using an AutoPore IV 9505 pore analyser, the experiments being performed according to GB/T29171-2012 standard.
Alternatively, the maximum mercury intrusion pressure is 200MPa and the minimum mercury intrusion pore radius is 3.7nm.
Alternatively, the temperature of the high pressure mercury intrusion test is 22.1-25.8 ℃ and the relative humidity is 18-22%.
Step 309, obtaining the cumulative pore volume of 5-10000nm aperture.
Step 310, a full pore size cumulative pore volume is obtained.
The results of the total pore size cumulative pore volume are shown in table 1 below.
Table 1: lake phase shale sample S1 value and cumulative pore volume statistics
In step 311, correlation analysis is performed.
Based on the data counted in table 1, a correlation analysis between the S1 value and the cumulative pore volume was performed.
Fig. 4 and 5 correspond to the low temperature nitrogen adsorption experiments. As shown in fig. 4 and 5, when the pore radius is between 2-5nm, the S1 value is significantly inversely related to the cumulative pore volume (R 2 = 0.8812); and when the pore radius is between 5 and 20nm, the S1 and the accumulated pore volume of the low-temperature nitrogen adsorption experiment are in a certain positive correlation (R 2 = 0.2914), which shows that free hydrocarbon is enriched in pores with the pore radius of more than 5 nm.
Fig. 6 to 9 correspond to high-pressure mercury injection experiments. As shown in fig. 6 to 9, when the pore radius is between 5-50nm, the S1 value has a significant positive correlation with the cumulative pore volume (R 2 = 0.8552); when the pore radius is between 50 and 100nm, the S1 value and the accumulated pore volume are in a certain positive correlation (R 2 = 0.6239); when the pore radius is between 100 and 1000nm, the S1 value and the accumulated pore volume are in a certain positive correlation (R 2 = 0.4292); when the pore radius is between 1000-10000nm, the S1 value is positively correlated with the cumulative pore volume (R 2 = 0.2976).
At step 312, a free hydrocarbon enriched pore size range is determined.
In the pore diameter range where a plurality of correlations belong to positive correlations, the pore diameter range where the determination coefficient is the largest is 5-50nm, namely: the pore size range for free hydrocarbon enrichment is 5-50nm.
In summary, according to the method provided by the embodiment, the S1 value representing the free hydrocarbon content of the unextracted shale sample is obtained through the rock pyrolysis experiment, the relation between the S1 value and the cumulative pore volume corresponding to different pore size ranges is established, and the free hydrocarbon enrichment pore size range is determined through the correlation analysis, so that the free hydrocarbon enrichment pore size range is accurately obtained.
The foregoing description of the preferred embodiments of the present application is not intended to limit the application, but rather, the application is to be construed as limited to the appended claims.
Claims (5)
1. A method of determining a free hydrocarbon enriched pore size range, the method comprising:
Obtaining a shale sample, and preparing a core column, wherein the core column is a column body obtained by drilling the shale sample;
Dividing the core column into a first core column, a second core column and a third core column;
rock pyrolysis experiments are carried out on the first core column, and an S1 value representing the free hydrocarbon content of the core column is obtained;
Extracting organic matters from the second core column and the third core column by using an organic solvent, and removing crude oil in the first core column and the second core column;
Performing a low-temperature nitrogen adsorption experiment on the second core column after the organic extraction to obtain an accumulated pore volume corresponding to 2-5nm and an accumulated pore volume corresponding to 5-20nm, wherein the 2-5nm and the 5-20nm correspond to a first pore diameter range, and the first pore diameter range comprises a pore diameter range of 2-50 nm;
Performing a high-pressure mercury injection experiment on the third core column after the organic extraction to obtain a cumulative pore volume corresponding to 5-50nm, a cumulative pore volume corresponding to 50-100nm, a cumulative pore volume corresponding to 100-1000nm and a cumulative pore volume corresponding to 1000-10000nm, wherein 5-50nm corresponds to the first pore diameter range, 50-100nm, 100-1000nm and 1000-10000nm corresponds to a second pore diameter range, the second pore diameter range comprises a pore diameter range of 5-10000nm, and the pore diameter range is determined by performing at least one experiment on the core column;
Acquiring a total pore diameter accumulated void volume, and analyzing the correlation of the S1 value and the accumulated void volume corresponding to the total pore diameter range;
determining that the correlation belongs to a positively correlated aperture range;
In the pore diameter range of which the correlation belongs to the positive correlation, determining the pore diameter range with the largest decision coefficient as the free hydrocarbon enrichment pore diameter range, wherein the decision coefficient is used for indicating the ratio of the regression interpretable dispersion square sum to the total dispersion square sum in linear regression, the numerical value of the decision coefficient is equal to the square of the correlation coefficient R, and the value range of the decision coefficient is 0 to 1.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises,
The correlation also includes a negative correlation.
3. The method of claim 1, wherein the step of determining the position of the substrate comprises,
The solvent adopted for extracting the organic matters is chloroform, and the duration of extracting the organic matters is not less than 72 hours.
4. The method according to claim 1, wherein the method further comprises:
And heating the core column after the organic matter extraction.
5. The method of claim 4, wherein the step of determining the position of the first electrode is performed,
The heating is performed under vacuum-pumping condition at a temperature higher than 100 ℃, and the duration of the heating is not less than 12 hours.
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