A method for analyzing the composition of population oil inclusions in calcite minerals

Abstract

The present invention discloses a method for analyzing the composition of population oil inclusions in calcite minerals, which includes washing oil from calcite particles; randomly dividing the oil-washed calcite particles into two parts, and subjecting the first part of the calcite particles to microscopic detection; grinding the second part of the calcite particles to release the organic components in the microcracks of the calcite particles; adding dilute hydrochloric acid to the calcite powder for acidolysis to release the organic components in the oil inclusions of the calcite powder. The beneficial effects of the present invention are as follows: Based on the microscopic observation of the morphological characteristics of intermediate cracks and oil inclusions in mineral particles, first, the components of oil inclusions in calcite microcracks are released by "mechanical crushing + extraction", and then the components of oil inclusions in the mineral matrix are released by "acid dissolution + extraction", realizing the batch extraction of different types of population oil inclusions in mineral microcracks and the mineral matrix, and improving the method for studying the properties of charged crude oil and the stages of hydrocarbon accumulation using population oil inclusions.

Description

Technical Field

[0001] The present invention relates to the technical field of oil inclusion analysis, and particularly to a method for analyzing the composition of population oil inclusions in calcite minerals. Background Art

[0002] Analyzing the hydrocarbon components in oil inclusions is the most direct means to understand important information such as the properties, sources, and formation environments of hydrocarbons therein. At present, oil inclusion composition analysis technology is widely used in oil-oil correlation, oil-source correlation, hydrocarbon accumulation stages and other aspects of research in oil and gas exploration. Oil inclusion composition analysis can be divided into single oil inclusion composition analysis and population oil inclusion composition analysis. Before analysis, both need to first open the inclusions sealed in mineral particles and release the components. For single oil inclusion composition analysis, laser ablation is generally used to open the sealed inclusions at present, while for population oil inclusion component analysis, mechanical crushing (grinding) of rock particles is generally used to open the oil inclusions.

[0003] For population oil inclusion component analysis, the general sample preparation process in the laboratory currently is: sample crushing, mineral selection, sample washing, grinding, and extraction, etc. First, through sample crushing and sample washing, the hydrocarbon contamination existing on the mineral surface is removed, and finally, the hydrocarbon components of population oil inclusions are released and collected by crushing rock particles.

[0004] The above process has the following problems: First, the oil inclusion-bearing minerals selected by this process only undergo 1 time of sample washing and grinding, without distinguishing the possible differences between the microcracks in the mineral aggregate and the oil inclusions inside the particle matrix, which may cause the mixing of oil inclusion components in different stages. The mixing effect may distort the final oil inclusion component information, resulting in incorrect understanding of oil sources and hydrocarbon accumulation stages; Second, since the mechanical crushing of samples generally reaches 60 - 100 mesh at present, and the diameter of inclusions in minerals is many less than 20 μm, many of the smaller oil inclusions in minerals still cannot be fully opened by mechanical crushing. Summary of the Invention

[0005] In view of this, it is necessary to provide a method for analyzing the composition of population oil inclusions in calcite minerals to solve the technical problems that the existing methods for analyzing the components of population oil inclusions cannot distinguish the organic components in the microcracks of mineral aggregates and the oil inclusions inside the particle matrix, which may lead to the distortion of the measured component information and the inability to fully open the smaller oil inclusions in minerals.

[0006] To achieve the above object, the present invention provides a method for analyzing the composition of population oil inclusions in calcite minerals, including the following steps:

[0007] S1. Crush the calcite sample to obtain a number of calcite particles, and wash the oil from the calcite particles to remove the organic matter adsorbed on the surface of the calcite particles;

[0008] S2. Randomly divide the calcite particles after oil washing into two parts. Conduct microscopic detection on the first part of calcite particles to obtain the length distribution of microcracks and the diameter distribution of oil inclusions in the calcite particles. According to the length distribution of microcracks and the diameter distribution of oil inclusions in the first part of calcite particles, determine the grinding mesh number when grinding the second part of calcite particles. At this grinding mesh number, the particle size of the ground powder is larger than the diameter of the oil inclusions in the calcite particles and smaller than the length of the microcracks in the calcite particles;

[0009] S3. After further cleaning the second part of calcite particles, grind them according to the grinding mesh number determined in step S2 to obtain calcite powder, so as to release the organic components in the microcracks of the calcite particles. Extract and concentrate the organic components in the calcite powder, and then conduct at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM to determine the composition of the organic components in the microcracks of the calcite particles;

[0010] S4. Wash the calcite powder in step S3 again. After the washing is completed, add dilute hydrochloric acid to the calcite powder for acidolysis to release the organic components in the oil inclusions in the calcite powder;

[0011] S5. Extract the acidolysis solution to extract the oil-based components, and then conduct at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM to determine the composition of the organic components in the oil inclusions in the calcite powder.

[0012] In some embodiments, in step S1, the calcite sample is broken to obtain a number of calcite particles with a particle size of 0.5 - 2 mm.

[0013] In some embodiments, in step S1, the specific method for washing the oil from the calcite particles to remove the organic matter adsorbed on the surface of the calcite particles is: adding the calcite particles to a mixed solution of dichloromethane and methanol for oil washing.

[0014] In some embodiments, in step S3, the specific method for further cleaning the second part of calcite particles is:

[0015] S31. Put the second part of calcite particles into a Soxhlet extractor, then add a mixed solvent of dichloromethane and methanol, and conduct water bath heating until it becomes colorless;

[0016] S32. Then, put the sample into an ultrasonic cleaner, add a mixed solvent of dichloromethane and methanol for ultrasonic extraction. The extract is subjected to GC-MS purity detection until no obvious organic components can be detected. If organic components are detected, ultrasonic extraction is repeated until the GC-MS purity detection meets the standard.

[0017] In some embodiments, in step S3, for the extraction and concentration of organic components in calcite powder, and then at least one of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM tests is performed to determine the composition of the organic components in the microcracks of calcite particles. The specific method is as follows: Add calcite powder to dichloromethane for cold soaking, then concentrate the cold soaking solution, and perform at least one of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM tests on the concentrated liquid to determine the composition of the organic components in the microcracks of calcite particles.

[0018] In some embodiments, in step S4, the specific method for washing the calcite powder in step S3 again is as follows: Subject the calcite powder sample after cold soaking to Soxhlet extraction and ultrasonic extraction again. The liquid sample after extraction is subjected to GC-MS purity detection until no obvious organic components can be detected. If organic components are detected, ultrasonic extraction is performed again until the GC-MS purity detection meets the standard.

[0019] In some embodiments, step S5 specifically includes:

[0020] S51. Add dilute hydrochloric acid to the calcite powder sample after cold soaking for acidolysis;

[0021] S52. Add dichloromethane for extraction to the sample solution after acidolysis, and separate with a separatory funnel to obtain the final hydrocarbon solution, and perform at least one of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM tests.

[0022] In some embodiments, in step S5, the concentration of the dilute hydrochloric acid is 10%.

[0023] Compared with the prior art, the beneficial effects of the technical solution proposed by the present invention are:

[0024] (1) Based on the microscopic observation of the intermediate cracks in mineral grains and the morphological characteristics of oil inclusions, first, the components of oil inclusions in calcite microcracks are released by "mechanical crushing + extraction", and then the components of oil inclusions in mineral matrix are released by "acid dissolution + extraction" to gradually open and extract the components of oil inclusions in calcite mineral microcracks and ore machine matrix. This pretreatment method for inclusion analysis can achieve the batch extraction of oil inclusions with different properties in mineral microcracks and mineral matrix, further enriching and improving the methods and connotations of studying the properties of injected crude oil and hydrocarbon accumulation periods using population oil inclusions;

[0025] (2) For the smaller-sized oil inclusions in minerals, the technical solution provided by the present invention uses "acid dissolution + extraction" to release the components of oil inclusions in mineral matrix, which can fully open the smaller-sized oil inclusions and improve the accuracy of detection results. Brief Description of the Drawings

[0026] Figure 1 is a schematic flow chart of an embodiment of the method for analyzing the composition of population oil inclusions in calcite minerals provided by the present invention;

[0027] Figure 2 is Figure 1 a schematic flow chart of step S3 in

[0028] Figure 3 is Figure 1 a schematic flow chart of step S5 in

[0029] Figure 4 is a schematic diagram of the specific operation steps of a specific embodiment of the method for analyzing the composition of population oil inclusions in calcite minerals provided by the present invention;

[0030] Figure 5 is the GC-MS analysis result of the organic matter washed off from the mineral surface;

[0031] Figure 6 is a schematic diagram of the process of microscopic observation of calcite particles;

[0032] Figure 7 is the GC-MS analysis result of the cold soak concentrate;

[0033] Figure 8 is the GC-MS analysis result of the organic matter components obtained by acid dissolution and extraction. Detailed Embodiment

[0034] The following will specifically describe the preferred embodiments of the present invention with reference to the drawings, wherein the drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0035] Please refer toFigure 1 , the present invention provides a method for analyzing the composition of population oil inclusions in calcite minerals, the steps are as follows:

[0036] S1. Crush the calcite sample to obtain a number of calcite particles, and wash the calcite particles with oil to remove the organic matter adsorbed on the surface of the calcite particles.

[0037] In the step S1, when crushing the calcite sample to obtain a number of calcite particles, the particle size is 0.5 - 2 mm.

[0038] In the step S1, the specific method for washing the calcite particles with oil to remove the organic matter adsorbed on the surface of the calcite particles is:

[0039] Add the calcite particles into a mixed solution of dichloromethane and methanol for oil washing.

[0040] S2. Randomly divide the oil-washed calcite particles into two parts. Microscopically detect the first part of the calcite particles to obtain the length distribution of microcracks and the diameter distribution of oil inclusions in the calcite particles. According to the length distribution of microcracks and the diameter distribution of oil inclusions in the first part of the calcite particles, determine the grinding mesh number when grinding the second part of the calcite particles. At this grinding mesh number, the particle size of the ground powder is larger than the diameter of the oil inclusions in the calcite particles and smaller than the length of the microcracks in the calcite particles.

[0041] S3. After further cleaning the second part of the calcite particles, grind them according to the grinding mesh number determined in step S2 to obtain calcite powder, so as to release the organic components in the microcracks of the calcite particles. Extract and concentrate the organic components in the calcite powder, and then perform GC (gas chromatography), GC-MS (gas chromatography - mass spectrometry), GC-MS-MS (new triple quadrupole gas chromatography - mass spectrometry), LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometer), IRSM (improved response surface method) tests to determine the composition of the organic components in the microcracks of the calcite particles.

[0042] Please refer to Figure 2 , in the step S3, the specific method for further cleaning the second part of the calcite particles is:

[0043] S31. Put the second part of the calcite particles into a Soxhlet extractor, then add a mixed solvent of dichloromethane and methanol, and perform water bath heating until it becomes colorless;

[0044] S32. Then, put the sample into an ultrasonic cleaner, add a mixed solvent of dichloromethane and methanol for ultrasonic extraction. The extract is subjected to GC-MS purity detection until no obvious organic components can be detected. If organic components are detected, ultrasonic extraction is repeated again until the GC-MS purity detection meets the standard.

[0045] In the said step S3, for the extraction and concentration of the organic components in the calcite powder, and then at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM is carried out to determine the specific method of the components of the organic components in the microcracks of the calcite particles is as follows:

[0046] Add the calcite powder to dichloromethane for cold soaking, then concentrate the cold soaking solution, and the concentrated liquid is subjected to at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM to determine the components of the organic components in the microcracks of the calcite particles.

[0047] S4. Clean the calcite powder in step S3 again. After the cleaning is completed, add dilute hydrochloric acid to the calcite powder for acidolysis to release the organic components in the oil inclusions of the calcite powder.

[0048] In the said step S4, the specific method for cleaning the calcite powder in step S3 again is as follows:

[0049] The calcite powder sample after cold soaking is subjected to Soxhlet extraction and ultrasonic extraction again. The liquid sample after extraction is subjected to GC-MS purity detection until no obvious organic components can be detected. If organic components are detected, ultrasonic extraction is carried out again until the GC-MS purity detection meets the standard.

[0050] S5. Extract the acidolysis solution to extract the oil-based components, and then at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM is carried out to determine the components of the organic components in the oil inclusions of the calcite powder.

[0051] Please refer to Figure 3 , the said step S5 specifically includes:.

[0052] S51. Add dilute hydrochloric acid to the calcite powder sample after cold soaking for acidolysis;

[0053] S52. Add dichloromethane for extraction to the sample solution after acidolysis, and separate with a separating funnel to obtain the final hydrocarbon solution, and carry out at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, IRSM.

[0054] In the step S5, the concentration of the dilute hydrochloric acid is 10%.

[0055] The present invention innovatively designs a method for analyzing and processing the components of population oil inclusions in calcite minerals. That is, based on the microscopic observation of the intermediate cracks and the morphological characteristics of oil inclusions in mineral particles, first, the components of oil inclusions in calcite microcracks are released through "mechanical crushing + extraction", and then the components of oil inclusions in the mineral matrix are released through "acid dissolution + extraction" to achieve the purpose of gradually opening and extracting the components of oil inclusions in calcite microcracks and the ore machine matrix. This pre-treatment method for inclusion analysis can realize the batch extraction of different types of population oil inclusions in mineral microcracks and the mineral matrix, further enriching and improving the methods and connotations of using population oil inclusions to study the properties of charged crude oil and the periods of hydrocarbon accumulation.

[0056] In addition, for the smaller oil inclusions in minerals, the technical solution provided by the present invention uses "acid dissolution + extraction" to release the components of oil inclusions in the mineral matrix, which can fully open the smaller oil inclusions and improve the accuracy of the detection results.

[0057] Specific implementation cases

[0058] Take a certain amount of calcite samples from the macroscopic fractures of the bedrock reservoir in Well BC-4 (1419m and 1565 - 1575m) in the Bongor Basin, Chad, Africa, and conduct an analysis of the components of population oil inclusions in calcite minerals. The specific operation process is as follows (as Figure 4 )

[0059] (1) Initially crush and select the samples to remove impurities. Crush the samples into particles with a cross-section of about 1mm × 1mm using a mortar, add a mixed solvent of dichloromethane (analytical pure, double-distilled) and methanol (V:V = 93:7) for oil washing to remove the organic matter adsorbed on the surface of the minerals, and conduct a group component separation on the washed organic matter. The saturated hydrocarbon and aromatic hydrocarbon components are analyzed by GC-MS, and the analysis results are as Figure 5 shown.

[0060] (2) Divide the oil-washed calcite mineral particles into two parts. First, perform Soxhlet extraction on one part. Add a mixed solvent of dichloromethane (analytical pure, double-distilled) and methanol (V:V = 93:7), and heat in a water bath at 55°C until it becomes colorless. Then perform ultrasonic extraction. Put the sample after Soxhlet extraction into an ultrasonic cleaner, add a mixed solvent of dichloromethane (analytical pure, double-distilled) and methanol (V:V = 93:7) for ultrasonic extraction, and conduct a GC-MS purity test on the ultrasonic extraction solution until no obvious organic components can be detected. If there are still trace components, repeat the ultrasonic extraction again until the GC-MS purity test reaches the standard.

[0061] (3) Another part of the calcite particles is dried and then subjected to microscopic observation. The main observations are the distribution and specifications of microcracks inside the calcite minerals, and the distribution of the long-axis lengths of the microcracks is statistically obtained. On the other hand, the morphology and optical characteristics of the inclusions are observed to determine the content and diameter distribution of the oil inclusions. The results of this observation show (as Figure 6 ), the long axes of the microcracks are generally greater than 200 μm, while the long-axis diameters of the inclusions are all less than 100 μm, and most are less than 40 μm. Based on this, the next grinding mesh number is determined to be 80 mesh (equivalent to a particle size of 0.18 mm after grinding).

[0062] (4) The qualified calcite particles obtained by extraction are further ground into 80-mesh powder using a mortar. Subsequently, 5 ml of dichloromethane is added and cold-soaked for 30 min, and the cold-soaked solution is concentrated to 10 μm for GC-MS component analysis. The analysis results are as Figure 7 shown.

[0063] (5) The powder after cold soaking is subjected to Soxhlet extraction and ultrasonic extraction in step (2) and subsequent GC-MS purity detection.

[0064] (6) 10% dilute hydrochloric acid is added to the qualified calcite powder for acidolysis. Dichloromethane is added to the acidolysis sample solution for extraction, and the final hydrocarbon solution is separated using a separating funnel for GC-MS component analysis. The analysis results are as Figure 8 shown.

[0065] From the GC-MS analysis results of the organic matter components obtained by rinsing the initial calcite particles ( Figure 5 ), the GC-MS analysis results of the organic matter components obtained by cold soaking the ground particles to 80 mesh ( Figure 7 ), and the GC-MS analysis results of the organic matter components obtained by finally acid dissolution and extraction ( Figure 8 ), it can be seen that there are significant differences in the compositions of the population oil inclusion components in the microcracks and the calcite mineral matrix of the reservoir calcite minerals obtained by this method, which are comparable ( Figure 3 ), indicating that this method is an effective method for analyzing the organic components of different stages of population oil inclusions in calcite.

[0066] It should be noted that:

[0067] In this specific embodiment, the composition of the oil inclusions was analyzed using a gas chromatography-mass spectrometry (GC-MS) analyzer. The instrument model is GC(7890B)-MS(5877B) from Agilent Technologies. The chromatographic conditions are as follows: the chromatographic column model is HP-5ms fused silica capillary column (30m × 0.25mm × 0.25μm). The temperature programming is as follows: hold at 50°C for 1 minute, with a heating rate of 20°C / min from 50°C to 100°C, a heating rate of 3°C / min from 100°C to 310°C, and hold at 315°C for 16 minutes. The injector temperature is 300°C, the carrier gas is He, the flow rate is 1.00ml / min, and the scanning range is 50 - 550amu. The detection methods are full scan and selected ion monitoring (SIM), the ionization energy is 70eV, and the ion source temperature is 230°C.

[0068] The instrument used for microscopic observation of microfractures and inclusions in calcite minerals is an oil and gas inclusion microscopic thermometry system, and the instrument model is AxioImager.A2 from Carl Zeiss.

[0069] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for analyzing the composition of population oil inclusions in calcite minerals, characterized in that, It includes the following steps: S1. Crush the calcite sample to obtain several calcite particles, and wash the calcite particles with oil to remove the organic matter adsorbed on the surface of the calcite particles; S2. Randomly divide the oil-washed calcite particles into two parts. Microscopically detect the first part of the calcite particles to obtain the length distribution of microcracks and the diameter distribution of oil inclusions in the calcite particles. According to the length distribution of microcracks and the diameter distribution of oil inclusions in the first part of the calcite particles, determine the grinding mesh number when grinding the second part of the calcite particles. At this grinding mesh number, the particle size of the ground powder is larger than the diameter of the oil inclusions in the calcite particles and smaller than the length of the microcracks in the calcite particles; S3. After further cleaning the second part of the calcite particles, grind them according to the grinding mesh number determined in step S2 to obtain calcite powder, so as to release the organic components in the microcracks of the calcite particles. Extract and concentrate the organic components in the calcite powder, and then perform at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM to determine the composition of the organic components in the microcracks of the calcite particles; S4. Wash the calcite powder in step S3 again. After the washing is completed, add dilute hydrochloric acid to the calcite powder for acidolysis to release the organic components in the oil inclusions of the calcite powder; S5. Extract the acidolysis solution to extract the oil-based components, and then perform at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM to determine the composition of the organic components in the oil inclusions of the calcite powder.

2. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S1, when crushing the calcite sample to obtain several calcite particles, the particle size is 0.5 - 2 mm.

3. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S1, the specific method for washing the calcite particles with oil to remove the organic matter adsorbed on the surface of the calcite particles is: Add the calcite particles to a mixed solution of dichloromethane and methanol for oil washing.

4. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S3, the specific method for further cleaning the second part of the calcite particles is: S31. Put the second part of the calcite particles into a Soxhlet extractor, add a mixed solvent of dichloromethane and methanol, and perform water bath heating until it becomes colorless; S32. Then put the sample into an ultrasonic cleaner, add a mixed solvent of dichloromethane and methanol for ultrasonic extraction, and perform GC-MS purity detection on the extraction solution until no obvious organic components are detected. If organic components are detected, repeat the ultrasonic extraction again until the GC-MS purity detection reaches the standard.

5. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S3, the specific method for extracting and concentrating the organic components in the calcite powder, and then performing at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM to determine the composition of the organic components in the microcracks of the calcite particles is: Add calcite powder to dichloromethane for cold soaking, then concentrate the cold soaking solution, and conduct at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM on the concentrated liquid to determine the composition of the organic components in the microcracks of the calcite particles.

6. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S4, the specific method for washing the calcite powder in the step S3 again is as follows: Perform Soxhlet extraction and ultrasonic extraction on the calcite powder sample after cold soaking again, and conduct GC-MS purity detection on the extracted liquid sample until no obvious organic components can be detected. If organic components are detected, perform ultrasonic extraction again until the GC-MS purity detection reaches the standard.

7. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, The step S5 specifically includes: S51. Add dilute hydrochloric acid to the calcite powder sample after cold soaking for acidolysis; S52. Add dichloromethane for extraction to the sample solution after acidolysis, and separate with a separating funnel to obtain the final hydrocarbon solution, and conduct at least one of the tests of GC, GC-MS, GC-MS-MS, LA-ICP-MS, and IRSM.

8. The method for analyzing the composition of population oil inclusions in calcite minerals according to claim 1, characterized in that, In the step S5, the concentration of the dilute hydrochloric acid is 10%.

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