Method for determining asphalt maturity using infrared absorption characteristic peaks and application thereof

Abstract

This invention discloses a method for determining asphalt maturity using infrared absorption characteristic peaks and its application, relating to the field of oil and gas exploration technology. The infrared absorption characteristic peaks are located at 1000-1100 cm⁻¹. ‑1 The organic C-O stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. ‑1 The inorganic C-O stretching vibration peak is located at 1000-1100 cm⁻¹. The characteristic infrared absorption peak is observed at this location. ‑1 The organic C-O stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. ‑1 The asphalt reflectance was determined by measuring the area ratio of the inorganic C-O stretching vibration peaks at a given location to assess asphalt maturity. The asphalt reflectance was calculated using the following formula: RmcRo%=1.7714e 0.7649(AoC‑O / AiC‑O) In the formula, RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. ‑1 The organic C-O stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. ‑1 The area ratio of the inorganic C-O stretching vibration peaks at the specified location. Simultaneously, this invention also provides a method for determining asphalt maturity using infrared absorption characteristic peaks. The infrared absorption characteristic peaks provided by this invention exhibit outstanding performance in determining asphalt maturity, and the method for determining asphalt reflectance is simple, convenient, unaffected by region or sample, and highly accurate.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, specifically to a method for determining the maturity of asphalt using infrared absorption characteristic peaks and its application. Background Technology

[0002] Deep to ultra-deep marine carbonate formations are one of the most important areas for oil and gas exploration in my country. Of the nearly 200 oil and gas reservoirs discovered globally in ultra-deep basins, more than 50 are buried at depths greater than 6500m, indicating abundant oil and gas resources in these deep and ultra-deep formations. Therefore, exploring for oil and gas in deep carbonate formations is one of the main trends in China's future oil and gas exploration. However, the unique geological backgrounds of different regions determine the complexity of deep carbonate reservoirs.

[0003] Unlike conventional kerogen and crude oil, solid bitumen can affect the geochemical and petrological assessments of conventional source rocks. The presence of these bitumen in marine carbonate rocks can influence geochemical and petrographic analyses. In fact, we still know very little about the properties of solid bitumen. This is partly due to the unclear migration pathways of liquid bitumen in sedimentary rocks, and partly due to the fact that adjacent source rocks may produce different macromolecular components and bitumen compositions. Furthermore, variations in temperature, pressure, pH, and Eh conditions within the Earth's chemical environment can also lead to differences in macromolecular composition and properties between solid bitumen samples.

[0004] The presence of bitumen and residual solid hydrocarbon compounds directly demonstrates that the source rocks have reached an appropriate level of thermal maturity to produce liquid hydrocarbons, with bitumen being a byproduct of petroleum and natural gas. The properties, origins, and evolution mechanisms of solid bitumen are crucial for understanding the generation, migration, accumulation, and enrichment of hydrocarbons. Therefore, determining bitumen maturity, i.e., bitumen reflectivity, remains a key and challenging problem in petroleum geology and geochemistry.

[0005] Currently, there are two common methods for determining the reflectivity of asphalt:

[0006] Microscopic measurements: Asphalt reflectance has been confirmed to have a linear correlation with vitrinite reflectance, but due to the influence of different origins and geological backgrounds, various parameters of asphalt reflectance and vitrinite reflectance need to be redefined.

[0007] Raman spectroscopy determination: the peak spacing or peak height of the Raman shift of the G peak and the D peak in the Raman spectrum. However, due to geological conditions and sample factors, the G peak and D peak of some marine carbonate rocks are not well displayed, and the background peaks are too messy.

[0008] Infrared analysis is based on the principle that when the frequency of infrared light at certain wavelengths matches the vibrational frequency of a functional group in a molecule, the molecule absorbs energy and transitions from its ground state vibrational energy level to a higher energy level. The absorption of infrared light by the molecules is recorded by an instrument, resulting in an infrared absorption spectrum. Then, based on parameters such as the position, number, relative intensity, and shape (peak width) of the characteristic infrared absorption peaks of various substances, the presence of functional groups in the sample can be inferred.

[0009] In infrared spectroscopy studies of highly evolved bitumen, it is commonly used for the identification and quantification of multiple functional groups, including aliphatic CH, CH2, and CH3; aromatic CH and CC; and oxygen-containing functional groups such as carboxyl, quinone, aldehyde, ketone, and ester. The functional group composition and maturity of organic matter undergo significant changes during the conversion of kerogen to bitumen. Factor A represents aliphatic characteristics (aliphatic CH2 / [aliphatic CH3]). 2+ Aromatic C=C]), the C factor represents oxidation properties (C=O / [C=O+aromatic C=C]. It was found that the A factor in kerogen generally decreases with increasing maturity, but this index does not change significantly in pitch; the C factor in both kerogen and pitch decreases slowly with increasing maturity because heteroatoms are removed from both systems during pyrolysis. Aromaticity (aromatic CH / aliphatic CHx) increases with increasing maturity in both kerogen and pitch, but the increase in pitch is extremely low, making it difficult to study. The CH3 / CH2 ratio (inversely proportional to aliphatic chain length) increases with increasing maturity in kerogen, but decreases with increasing maturity in pitch, and this index often fails to show characteristic peaks of CH3 and CH2 due to excessively high pitch evolution. Figure 1 As shown.

[0010] Therefore, providing a new infrared characteristic peak as a geochemical parameter for determining the maturity of marine carbonate rock solid bitumen is a problem that this invention urgently needs to solve. Summary of the Invention

[0011] This invention provides a method for determining asphalt maturity using infrared absorption characteristic peaks and its application, aiming to solve the problems existing in the above-mentioned background technology.

[0012] To achieve the above-mentioned technical objectives, the present invention mainly adopts the following technical solutions:

[0013] In a first aspect, this invention discloses the application of infrared absorption characteristic peaks in determining asphalt maturity, wherein the infrared absorption characteristic peaks are 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The inorganic CO stretching vibration peak at that location.

[0014] In a preferred embodiment of the present invention, the infrared absorption characteristic peak is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The asphalt reflectivity is determined by measuring the area ratio of the inorganic CO stretching vibration peak at a given location, thus assessing the asphalt maturity.

[0015] Furthermore, the asphalt reflectivity is calculated using the following formula:

[0016] RmcRo%=1.7714e 0.7649(AoC-O / AiC-O)

[0017] In the formula, RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peak at that location.

[0018] Secondly, this invention discloses a method for determining asphalt maturity using infrared absorption characteristic peaks, comprising the following steps:

[0019] (1) Select marine carbonate rock solid bitumen samples, grind and crush them, sieve them, and store them separately according to geological conditions;

[0020] (2) Grind potassium bromide under an infrared lamp until it becomes powder, then mix the asphalt sample powder with the potassium bromide powder and press it into tablets in a tablet press.

[0021] (3) Place the compressed sample into an infrared spectrometer for measurement;

[0022] (4) The infrared absorption characteristic peak is calculated to be 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peaks at a given location is used to calculate the asphalt reflectivity using the following formula:

[0023] RmcRo%=1.7714e 0.7649(AoC-O / AiC-O)

[0024] In the formula, RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peak at that location.

[0025] In a preferred embodiment of the present invention, in step (1), the marine carbonate rock solid bitumen sample is selected from outcrop or downhole samples, and the sample strata include the Middle Paleozoic Jixian System, Cambrian System, and Ordovician System.

[0026] In a preferred embodiment of the present invention, in step (1), the ground and pulverized solid asphalt sample is passed through a 100-mesh sieve.

[0027] In a preferred embodiment of the present invention, in step (2), the mass ratio of the asphalt sample powder to the potassium bromide powder is 1:100.

[0028] In a preferred embodiment of the present invention, in step (2), the tableting step is as follows: the lower punch of the tablet press is placed in the slot with the smooth side facing upwards, the sample to be tested is laid flat, and the upper punch is placed on top; the tablet press is placed in the middle of the tableting table, the bottom knob is closed, and the air valve is turned upwards to pressurize to 20T / cm. 2 Maintain the above for at least 30 seconds; open the air valve and rotate the tablet press along with the base 180°, then repeat the same operation once more; after pressing, invert the base and remove it, then place the tablet press upside down on the tablet ejector, press it down, use tweezers to remove the lower punch, take out the sample, and place it on the sample clamping plate.

[0029] In a preferred embodiment of the present invention, step (3) includes an infrared spectroscopy pretreatment step before infrared spectroscopy measurement: before the experiment, dichloromethane is used to clean the medicine spoon, pressure core and agate mortar, and after cleaning, the surface is lightly covered with tin foil and placed at 50°C to dry for 24 hours.

[0030] In a preferred embodiment of the present invention, in step (3), the infrared spectrometer measurement parameters are as follows: a Bruker VERTEX 80 / 80V Fourier transform infrared spectrometer is used, with a DTGS KBr detector, 20 sample scans, 20 background scans, a resolution of 4.0, a gain of 1.0, a mirror rate of 0.6329, and a wavenumber range of 4000–500 cm⁻¹. -1 .

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The infrared absorption characteristic peaks provided by this invention are prominent in the process of determining asphalt maturity, and the method for determining asphalt reflectance is simple and convenient, unaffected by region or sample, and has high accuracy. Attached Figure Description

[0033] Figure 1 These are the characteristic peaks of CH3 and CH2 obtained by conventional infrared spectroscopy.

[0034] Figure 2 The image shows the results of measuring the asphalt reflectance using the infrared absorption characteristic peaks of this invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0036] The terms "comprising" and "having," and any variations thereof, appearing in this specification, claims, and drawings, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. Furthermore, the terms "first," "second," and "third," etc., are used to distinguish different objects and are not used to describe a specific order.

[0037] Example

[0038] A method for determining asphalt maturity using infrared absorption characteristic peaks includes the following steps:

[0039] 1. Select marine carbonate rock solid bitumen samples, which can be outcrop or well samples. This time, we take outcrop dolomite bitumen from the Ordos Basin as an example. The sample strata are the Middle Paleozoic Jixian System, Cambrian System, and Ordovician System, which include the current deep and ultra-deep geological history period and the main marine carbonate rock deposition period.

[0040] 2. Sample pretreatment: Grind and crush the selected asphalt, pass it through a 100-mesh sieve, and store it separately according to geological conditions;

[0041] 3. Pretreatment for infrared spectroscopy: Before the experiment, all instruments, including the spatula, pressure core, and agate mortar, were cleaned with dichloromethane. After cleaning, the surfaces were lightly covered with tin foil and dried at 50℃ for 24 hours to avoid errors.

[0042] 4. Infrared Spectroscopy Determination: Grind potassium bromide under an infrared lamp until it becomes powder. Use a small spatula to take a small amount (approximately 0.006g) of the processed solid asphalt sample and place it in a mortar. Take a large spatula and add 0.6g of the ground potassium bromide to the mortar, mixing it thoroughly with the powder sample. The ratio of powder sample to potassium bromide is 1:100. Then, press the mixed sample into a tablet. Place the tablet press with the smooth side of the lower punch facing upwards in the groove, spread the sample to be tested evenly, and place the upper punch on top. Place the tablet press in the center of the pressing table, tighten the bottom knob, and pressurize to 20 T / cm² by turning the air valve upwards. 2Maintain the pressure for at least 30 seconds; open the air valve, rotate the tablet press along with its base 180°, and then repeat the same operation; after pressing, invert the base and remove it, place the tablet press upside down on the tablet ejector, press it down, remove the lower punch with tweezers, take out the sample, and place it on the sample holder; place the prepared sample into the instrument, open the PC desktop infrared spectroscopy software, and click "Acquisition" - "Acquisition Sample" - "OK" in sequence; wait for the scan to complete for several tens of seconds, take out the sample, and click "OK" in the pop-up acquisition background dialog box. This paper uses a Bruker VERTEX 80 / 80V Fourier transform infrared spectrometer with a resolution better than 0.1 cm⁻¹. -1 There are two wavenumber modes, 13000–7000 cm⁻¹ -1 7400~400cm -1 The experimental parameters in this paper were set as follows: detector DTGS KBr, sample scan count 20, background scan count 20, resolution 4.0, gain 1.0, mirror rate 0.6329, and wavenumber range 4000–500 cm⁻¹. -1 .

[0043] 4. Peak processing and peak selection: Organic peaks should be selected at 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The inorganic CO stretching vibration peak at the location represents the degree of evolution of solid bitumen. Due to the stability of CO bonds, the CO stretching vibration peak provided by carbonate rocks as inorganic minerals is relatively stable and shows little difference in different samples. This is also an advantage of this method compared with other organic geochemical methods.

[0044] After determining the peak positions, the peak areas of the organic CO stretching vibration peak and the inorganic CO stretching vibration peak are integrated to determine the peak areas, and then calculated to obtain AoC-O / AiC-O. Here, AoC-O is the peak area of ​​the organic CO stretching vibration, and AiC-O is the peak area of ​​the inorganic CO stretching vibration.

[0045] 5. Asphalt reflectivity determination: The asphalt reflectivity of marine carbonate reservoirs from different strata was determined using the following formula:

[0046] RmcRo%=1.7714e 0.7649(AoC-O / AiC-O)

[0047] Where RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peak at that location.

[0048] To verify the accuracy and reliability of the asphalt reflectance calculation in this invention, a traditional method for measuring asphalt reflectance is also employed. Asphalt reflectance can be directly measured under a microscope or calculated using equivalent values ​​from the D and G peaks of the Raman spectrum. In this example, to avoid errors caused by manual measurement of asphalt reflectance, the equivalent Raman spectral calculation method is chosen. Taking the D and G peaks of the Raman spectrum as an example, the formula is:

[0049] RmcRo%=1.1659×h(Dh / Gh)+2.7588

[0050] In the formula: h(Dh / Gh) is the ratio of the peak heights of D and G.

[0051] The results are as follows Figure 2 As shown. The asphalt reflectance obtained by conventional Raman spectroscopy is highly correlated with the asphalt reflectance of this invention, R 2 =0.9914, indicating that using the ratio of the area of ​​the organic CO stretching vibration peak to that of the inorganic CO stretching vibration peak as the equivalent reflectance of the high evolution degree of marine carbonate rock solid bitumen is accurate and convenient.

[0052] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. The application of infrared absorption characteristic peaks in determining asphalt maturity, characterized by: The asphalt is marine carbonate rock solid asphalt, and the infrared absorption characteristic peak is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The inorganic CO stretching vibration peak at that location.

2. The application according to claim 1, characterized in that: The infrared absorption characteristic peak is 1000-1100 cm⁻¹ -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The asphalt reflectivity is determined by measuring the area ratio of the inorganic CO stretching vibration peak at a given location, thus assessing the asphalt maturity.

3. The application according to claim 2, characterized in that: The asphalt reflectivity is calculated using the following formula: RmcRo%=1.7714e 0.7649(AoC-O / AiC-O) In the formula, RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peak at that location.

4. A method for determining asphalt maturity using infrared absorption characteristic peaks, characterized in that, Includes the following steps: (1) Select marine carbonate rock solid bitumen samples, grind and crush them, sieve them, and store them separately according to geological conditions; (2) Grind potassium bromide under an infrared lamp until it becomes powder, then mix the asphalt sample powder with the potassium bromide powder and press it into tablets in a tablet press. (3) Place the compressed sample into an infrared spectrometer for measurement; (4) The infrared absorption characteristic peak is calculated to be 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peaks at a given location is used to calculate the asphalt reflectivity using the following formula: RmcRo%=1.7714e 0.7649(AoC-O / AiC-O) In the formula, RmcRo% ​​is the asphalt reflectance, and (AoC-O / AiC-O) is 1000-1100 cm⁻¹. -1 The organic CO stretching vibration peak at 1400-1500 cm⁻¹ is similar to that at 1400-1500 cm⁻¹. -1 The area ratio of the inorganic CO stretching vibration peak at that location.

5. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (1), the marine carbonate rock solid bitumen samples are selected from outcrop or downhole samples, and the sample strata include the Middle Paleozoic Jixian System, Cambrian System, and Ordovician System.

6. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (1), the ground and pulverized solid asphalt sample is passed through a 100-mesh sieve.

7. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (2), the mass ratio of the asphalt sample powder to the potassium bromide powder is 1:

100.

8. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (2), the tableting process is as follows: Place the tablet press with the smooth side of the lower punch facing upwards into the slot, flatten the sample to be tested, and place the upper punch on top; place the tablet press in the center of the tableting table, tighten the bottom knob, and pressurize to 20 T / cm using the upward air valve. 2 Maintain the above for at least 30 seconds; open the air valve and rotate the tablet press along with the base 180°, then repeat the same operation once more; after pressing, invert the base and remove it, then place the tablet press upside down on the tablet ejector, press it down, use tweezers to remove the lower punch, take out the sample, and place it on the sample clamping plate.

9. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (3), before the infrared spectroscopy measurement, an infrared spectroscopy pretreatment step is also included: before the experiment, the medicine spoon, pressure core and agate mortar are cleaned with dichloromethane, and after cleaning, the surface is lightly covered with tin foil and placed at 50℃ to dry for 24 hours.

10. The method for determining asphalt maturity using infrared absorption characteristic peaks according to claim 4, characterized in that: In step (3), the infrared spectrometer parameters are as follows: a Bruker VERTEX 80 / 80V Fourier transform infrared spectrometer is used, with a DTGS KBr detector, 20 sample scans, 20 background scans, a resolution of 4.0, a gain of 1.0, a mirror rate of 0.6329, and a wavenumber range of 4000–500 cm⁻¹. -1 .

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