Crude oil Re-Os dating sample screening method based on quantitative fluorescence spectrum

Abstract

The invention discloses a crude oil Re-Os dating sample screening method based on a quantitative fluorescence spectrum, and belongs to the technical field of oil and gas accumulation process characterization of deep petroliferous basins in petroleum and natural gas geological exploration. According to the technical scheme, the method comprises the following steps: comparing quantitative fluorescence main peak wavelength lambda max data of the oil inclusion in a crude oil sample and a reservoir rock sample of the same well, and if the fluorescence main peak wavelength lambda max of the crude oil sample can be matched with a certain peak value in a statistical histogram of the fluorescence main peak wavelength lambda max of the oil inclusion of the reservoir rock sample, keeping the fluorescence main peak wavelength lambda max; if the main fluorescence peak wavelength lambda max of the crude oil sample cannot be matched with any peak value in the statistical histogram of the main fluorescence peak wavelength lambda max of the oil inclusion of the reservoir rock sample, the crude oil sample is screened out, and the crude oil sample subjected to secondary screening is obtained. The method is applied to the aspect of crude oil Re-Os dating sample screening, and the problem that in the prior art, systems of Re-Os isotope dating sample screening methods suitable for the multi-stage filling mixed background are not enough is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas reservoir forming process characterization in deep oil and gas bearing basin in oil and gas geological exploration, and particularly relates to a crude oil Re-Os dating sample screening method based on quantitative fluorescence spectrum. BACKGROUND

[0002] Oil and gas reservoir forming history determination is an important research field of petroleum geology, is a key problem that needs to be solved in oil and gas reservoir forming and distribution research of oil and gas bearing basin, and has important significance for exploration target optimization and evaluation and improvement of oil and gas reservoir exploration success rate. For a long time, determination of oil and gas reservoir forming period mainly relies on indirect methods such as fluid inclusion and basin simulation, and the conclusion has great uncertainty and many disputes. Re-Os isotope dating as a new and challenging oil and gas reservoir dating method in recent years can directly study the geological bodies (hydrocarbon source rock, asphalt, crude oil, etc.) involved in oil and gas reservoir forming, obtain absolute age information related to oil and gas reservoir forming, and has great potential in the field of oil and gas reservoir forming. However, deep oil and gas bearing basins such as Tarim Basin have experienced a long geological evolution history from the Paleozoic to the Cenozoic, and have complex hydrocarbon generation, migration, charging and secondary modification history. Previous research results show that fluid disturbance, deep hydrothermal fluid intrusion and multi-stage oil and gas charging and mixing will disturb the Re-Os isotope system of crude oil, making it difficult to study the Re-Os isotope dating of oil and gas samples in a complex geological background, and the age result error is large. Therefore, sample screening work is very important.

[0003] At present, scholars have proposed that black shale can be screened by CT scanning and XRF scanning and other methods to select samples with stable geochemical composition, good sedimentary lamina and no geological event modification such as hydrothermal intrusion, and high-precision Re-Os isotope age has been obtained. For crude oil samples, scholars have proposed to select crude oil from oil wells far from deep faults to avoid deep hydrothermal fluid intrusion, and to ensure that the selected crude oil samples have the same source through organic geochemical methods.

[0004] However, under the background of multi-stage oil and gas charging, the mixing of crude oil also has a great influence on the Re-Os isotope dating result, but there is no method to screen crude oil samples with high mixing degree at present. Therefore, it is urgent to establish a screening method for Re-Os isotope dating of crude oil samples suitable for the background of multi-stage oil and gas charging. SUMMARY

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is the lack of a sample screening method suitable for Re-Os isotope dating of samples in the multi-stage charging mixed background of the prior art, and a Re-Os dating sample screening method for crude oil based on quantitative fluorescence spectrum is provided to realize the screening of crude oil samples suitable for Re-Os dating in the multi-stage charging background.

[0006] To solve the technical problem, the technical scheme adopted by the present application is: The present application provides a Re-Os dating sample screening method for crude oil based on quantitative fluorescence spectrum, comprising: Quantitative fluorescence spectrum testing is performed on the inclusion thin sections corresponding to the representative reservoir rock samples of each block in the study area, and a histogram of the main peak wavelength frequency distribution is drawn; Separate the group components of all crude oil samples in the study area, and perform organic geochemical analysis to screen out outlier samples of different sources to obtain the crude oil samples after the first screening; Quantitative spectral determination is performed on the crude oil samples after the first screening, and the fluorescence main peak wavelength λmax of the crude oil samples is recorded; The fluorescence main peak wavelength λmax data of the oil inclusions in the reservoir rock samples and the crude oil samples from the same well are compared, if the fluorescence main peak wavelength λmax of the crude oil sample can match a certain peak value in the histogram of the fluorescence main peak wavelength λmax of the oil inclusions in the reservoir rock samples, it is retained, if the fluorescence main peak wavelength λmax of the crude oil sample cannot match any peak value in the histogram of the fluorescence main peak wavelength λmax of the oil inclusions in the reservoir rock samples, it is screened out, and the crude oil samples after the second screening are obtained; Re-Os isotope dating is performed on the crude oil samples after the second screening to obtain the absolute age information of the crude oil generated in the study area.

[0007] Preferably, quantitative fluorescence spectrum testing is performed on the inclusion thin sections corresponding to the representative reservoir rock samples of each block in the study area, and the fluorescence main peak wavelength λmax of the oil inclusions of the reservoir rock samples covering different observed fluorescence colors is obtained, and the fluorescence main peak wavelength λmax data of the oil inclusions of the reservoir rock samples is drawn into a histogram of the main peak wavelength frequency distribution with an interval of 10 nm.

[0008] Preferably, the group components of all crude oil samples in the study area are separated according to the provisions of the industry standard SY / T 5119-2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks.

[0009] Preferably, the group components of all crude oil samples in the study area are separated, and organic geochemical analysis is performed to screen out outlier samples of different sources, including: gas chromatography-mass spectrometry testing analysis is performed on the saturated hydrocarbon and aromatic hydrocarbon components, C 22 TT / C21 TT and C 24 TT / C 23 TT cross plot, Ph / nC 18 and Pr / nC 17 cross plot and C 27 -C 29 The ααα20R sterane ternary plot is used to screen the source of the crude oil sample, and the crude oil sample after the initial screening is obtained.

[0010] Preferably, the C 22 TT / C 21 TT and C 24 TT / C 23 TT cross plot, Ph / nC 18 and Pr / nC 17 cross plot and C 27 -C 29 The ααα20R sterane ternary plot is used to screen the source of the crude oil sample, and the crude oil sample after the initial screening is obtained.

[0011] Preferably, the quantitative spectral determination of the crude oil sample after the initial screening includes: using a rubber dropper to take 1-2 drops of the crude oil sample after the initial screening on a new glass slide, then covering it with a cover glass, and placing the slide under a microscope to determine the fluorescence peak wavelength λmax of the crude oil sample after the initial screening.

[0012] Preferably, it also includes: obtaining reservoir rock samples and crude oil samples representing high-yield oil-bearing wells in each block of the study area in deep oil and gas basins, and marking the sample well location and reservoir rock sample and crude oil sample depth and stratigraphic information.

[0013] Preferably, the ground reservoir rock sample inclusion piece is placed under the Nikon LV100N microscope equipped with a quantitative fluorescence spectrometer for fluid inclusion observation, and the fluorescence of the inclusion is observed by switching different magnification views to accurately position the oil inclusion. Under 10-20 times view, select the area of the slice where the inclusions are concentrated and take pictures for preservation, then use the quantitative fluorescence spectrometer to determine the fluorescence peak wavelength λmax of the oil inclusions in the selected view, while ensuring that the measurement object covers different colored oil inclusions observed, and the number of test oil inclusions is not less than 10. The data obtained is statistically analyzed by Origin and Excel data plotting software, and the oil inclusion fluorescence peak wavelength λmax data is plotted into a main peak wavelength frequency distribution histogram with an interval of 10 nm.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy. This method, combined with organic geochemical methods, utilizes quantitative fluorescence spectroscopy analysis of oil inclusions and reservoir crude oil in deep oil and gas basins to screen crude oil samples with the same origin and low mixing degree, suitable for Re-Os isotope dating, even in the presence of multiple crude oil charging events. This method demonstrates strong feasibility and applicability. This invention solves the problem of difficult sample screening for Re-Os isotope dating in oil reservoirs under complex charging and accumulation backgrounds, contributing to high-precision Re-Os isotope dating of oil reservoirs, providing important absolute age information for the study of deep oil and gas accumulation history, and further guiding oil and gas exploration. Attached Figure Description

[0015] Figure 1 This is a flowchart of the crude oil Re-Os dating sample screening method based on quantitative fluorescence spectroscopy provided in an embodiment of the present invention; Figure 2 The S1 step provided in this embodiment of the invention is to obtain representative drilled reservoir core samples from different blocks in the study area; Figure 3 This invention provides the S3 step for observing oil inclusions and determining the main peak wavelength of quantitative fluorescence spectroscopy. Figure 4 To illustrate step S3 of this invention, a histogram of the main peak wavelength frequency distribution is plotted. Figure 5 C provided for the embodiments of the present invention 22 TT / C 21 TT and C 24 TT / C 23 TT intersection chart; Figure 6 Ph / nC provided in the embodiments of the present invention 18 With Pr / nC 17 Intersection diagram; Figure 7 C provided for the embodiments of the present invention 27 –C 29 ααα20R sterane ternary graph; Figure 8 This is the comparison result of the main fluorescence wavelength of crude oil and fluid inclusions in region A of step S6 provided in the embodiment of the present invention; Figure 9 This is the comparison result of the main peak wavelength of quantitative fluorescence of crude oil and fluid inclusions in region B of step S6 provided in the embodiment of the present invention; Figure 10This is the comparison result of the main fluorescence wavelength of crude oil and fluid inclusions in region C of step S6 provided in the embodiment of the present invention; Figure 11 The Re-Os isotope dating results of crude oil samples in the study area after screening in step S7 of this invention are provided in an embodiment of the present invention. Detailed Implementation

[0016] The technical solutions in specific embodiments of the present invention will now be described in detail and completely with reference to the accompanying drawings. Obviously, the described embodiments are merely some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0017] This invention provides a method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy, such as... Figure 1 As shown, it includes: Step S1: Obtain reservoir rock and crude oil samples from high-yield oil-bearing wells in representative blocks of the study area in deep oil and gas basins, and mark the well locations, rock and crude oil sample burial depths and stratigraphic information. Step S2: For representative rock samples from each block of the study area, prepare thin sections of inclusions corresponding to the representative rock samples for reservoir fluid inclusion observation and quantitative fluorescence spectroscopy testing. Step S3: The ground inclusion slides were placed under a Nikon LV100N microscope equipped with a quantitative fluorescence spectrometer for fluid inclusion observation. Different magnification fields were used to observe the fluorescence of the inclusions to accurately locate the oil inclusions. Thin sections with concentrated inclusion development were selected at 10-20x magnification and photographed for preservation. Subsequently, quantitative fluorescence spectrometry was used to measure the fluorescence wavelength λmax of each oil inclusion within the selected field of view, recording its main fluorescence peak wavelength. It was ensured that the measurement included oil inclusions of different colors observed, and that at least 10 oil inclusions were tested. The obtained data were statistically analyzed using data plotting software such as Origin and Excel. Frequency histograms of the main fluorescence peak wavelength λmax of the oil inclusions were plotted at 10nm intervals to clarify the range of the main fluorescence peak wavelength of the oil inclusions. Step S4: All crude oil samples from the study area were subjected to group component separation according to the industry standard "SY / T 5119—2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks". Saturated hydrocarbons and aromatic hydrocarbons were subjected to gas chromatography. Mass spectrometry analysis, using C 22 TT / C 21 TT and C 24 TT / C 23 TT intersection chart, Ph / nC 18 With Pr / nC17 Intersection diagram and C 27 -C 29 The ααα20Rsterane ternary plot is used to screen the source of crude oil samples. Samples from the same source should be located in the same area on the plot. If some samples are located in a different area than the majority of samples on the plot, it indicates that these samples have different sources and should be screened out. Step S5: For the remaining crude oil samples in the study area, use a dropper to take 1-2 drops of crude oil and place them on a new glass slide. Then cover with a coverslip and place the slide under a microscope to perform quantitative spectral analysis on each crude oil sample using a quantitative fluorescence spectrometer. Record the wavelength λmax of the main fluorescence peak.

[0018] Step S6: Compare the quantitative fluorescence peak wavelength λmax data of oil inclusions in the crude oil and reservoir rock samples from the same well. If the quantitative fluorescence peak wavelength λmax of the crude oil matches a peak value in the statistical histogram of the quantitative fluorescence peak wavelength λmax of the reservoir inclusions, it indicates that the current crude oil in the well is mainly composed of crude oil charged by oil inclusions from that period, with weak contributions from crude oil charging corresponding to oil inclusions from other periods and a low degree of mixing. This sample can be used for Re-Os isotope dating. If the quantitative fluorescence peak wavelength λmax of the crude oil does not match any peak value in the statistical histogram of the quantitative fluorescence peak wavelength λmax of the reservoir inclusions, it indicates that crude oil charging corresponding to oil inclusions from each period contributes significantly to the current crude oil and has a high degree of mixing. In this case, the sample is not suitable for Re-Os isotope dating and should be screened out. Step S7: Finally, Re-Os isotope dating is performed on the screened crude oil samples to obtain the absolute age information of crude oil formation in the study area.

[0019] This invention addresses the need for Re-Os isotope dating of oil reservoirs in deep oil and gas basins with complex accumulation backgrounds. It tackles the lack of existing methods suitable for screening Re-Os isotope dating samples under mixed multi-stage charging conditions. This invention provides a complete, reliable, and easily operable method specifically for screening Re-Os dating samples under multi-stage crude oil charging conditions in deep oil and gas basins. Based on reservoir fluid inclusions and current quantitative fluorescence spectroscopy of crude oil, combined with organic geochemical methods, this method enables the screening of crude oil samples suitable for Re-Os dating under multi-stage crude oil charging conditions, providing reliable and direct age evidence for the study of oil and gas accumulation history.

[0020] To provide a clearer and more detailed description of the crude oil Re-Os dating sample screening method based on quantitative fluorescence spectroscopy provided in the embodiments of the present invention, specific embodiments will be described below.

[0021] Example In this embodiment, the samples are rock samples from three high-yield oil wells and crude oil samples from 18 high-yield oil wells in different blocks (areas A, B, and C) of the Tarim Basin's Tahe Oilfield. All samples are buried at depths exceeding 6000 m, representing typical examples of deep oil and gas basins rich in oil and gas reservoirs. Figure 2 ; According to step S1, 15 core samples were collected from 3 representative wells in different areas of the Tahe Oilfield in the Tarim Basin. According to step S2, thin sections of inclusions are ground for each rock sample for fluid inclusion observation and quantitative fluorescence spectroscopy determination. According to step S3, for the inclusion sections ground from the Ordovician samples of the three wells, thin sections containing inclusions of different developmental stages were selected and photographed under a 10-20x field of view for preservation. Using quantitative fluorescence spectrometry, the fluorescence spectra of each oil inclusion were measured under a 50x microscope, and the main peak wavelength λmax was recorded. Figure 3 Subsequently, Origin software was used to statistically analyze the fluorescence main peak wavelength λmax data from the three wells and plot the frequency distribution histogram, as shown below. Figure 4 ; According to step S4, the crude oil samples from the study area were subjected to group component separation in accordance with the industry standard "SY / T 5119—2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks". Saturated hydrocarbons and aromatic hydrocarbons were analyzed by gas chromatography. Mass spectrometry analysis, in C 22 TT / C 21 TT and C 24 TT / C 23 All samples on the TT cross-section are located within the marine shale region, Ph / nC 18 With Pr / nC 17 All samples on the cross-sectional diagram are within the range of marine type II kerogen, C 27 -C 29 The clustering of all samples on the ααα20R sterane ternary plot indicates that all crude oil samples in the study area originate from the same source: marine shale in a reducing environment. Figures 5-7 As shown.

[0022] According to step S5, take 1-2 drops of crude oil samples from 3 representative wells in different blocks and put them on a glass slide, cover with a coverslip, place under a microscope and use a quantitative fluorescence spectrometer to measure the fluorescence spectrum and record the main peak wavelength λmax. According to step S6, the wavelength λmax of the main peak of quantitative fluorescence in crude oil is compared with the wavelength λmax of the main peak of oil inclusions in the reservoir. Figures 8-10 As shown.

[0023] The representative well in Area A has a crude oil peak wavelength λmax of 527 nm. The statistical histogram of the peak wavelength λmax of the reservoir oil inclusions in this well shows two peak ranges: 520-535 nm and 545-555 nm. The peak wavelength λmax value of the crude oil corresponds to the 520-535 nm peak range of the reservoir oil inclusions, indicating that the crude oil in this well is mainly charged by the crude oil corresponding to the oil inclusions in this period. The crude oil charging corresponding to other oil inclusions has a weak contribution to the current crude oil and a low degree of mixing. It can be used for Re-Os dating.

[0024] Similarly, the main peak wavelength λmax of the crude oil in the representative well in Zone B is 538nm. The statistical histogram of the main peak wavelength λmax of the reservoir oil inclusions in this well shows three peak ranges: 490-510nm, 510-530nm, and 530-550nm. The main peak wavelength λmax of the crude oil can correspond to the 530-550nm peak range of the reservoir oil inclusions, indicating that the crude oil in this well is mainly charged by the crude oil corresponding to the oil inclusions in this period. The crude oil charging corresponding to other oil inclusions has a weak contribution to the current crude oil and a low degree of mixing. It can be used for Re-Os dating.

[0025] The representative well in Zone C has a peak wavelength λmax of 520 nm. The statistical histogram of the peak wavelength λmax of the reservoir oil inclusions in this well shows two peak ranges: 480-490 nm and 540-550 nm. The peak wavelength λmax value of the crude oil does not correspond to any peak range of the reservoir oil inclusions. It is clearly located in the middle of the two oil inclusion phases, indicating that the crude oil charging corresponding to the two oil inclusion phases has a strong contribution to the current crude oil. The crude oil in this well is a typical mixed crude oil and is not suitable for Re-Os dating. It should be screened out.

[0026] According to step S7, Re-Os isotope dating was performed on the screened crude oil samples from regions A and B, yielding a Re-Os isochron age of 292±33 Ma, indicating that the crude oil was mainly formed during the Late Hercynian period. Figure 11 As shown, this age information provides crucial evidence for determining the main accumulation period of crude oil in the current oil reservoirs within the study area.

Claims

1. A method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy, characterized in that, include: Quantitative fluorescence spectroscopy was performed on thin sections of inclusions corresponding to representative reservoir rock samples from each block in the study area, and histograms of the main peak wavelength frequency distribution were plotted. All crude oil samples from the study area were separated into group components, and organic geochemical analysis was performed to screen out outliers from different sources, resulting in crude oil samples after initial screening. Quantitative spectral analysis was performed on the crude oil samples after the initial screening, and the wavelength λmax of the main fluorescence peak of the crude oil samples was recorded. The quantitative fluorescence peak wavelength λmax data of oil inclusions in crude oil samples and reservoir rock samples from the same well are compared. If the fluorescence peak wavelength λmax of the crude oil sample matches a peak value in the statistical histogram of the fluorescence peak wavelength λmax of the oil inclusions in the reservoir rock sample, it is retained; if the fluorescence peak wavelength λmax of the crude oil sample does not match any peak value in the statistical histogram of the fluorescence peak wavelength λmax of the oil inclusions in the reservoir rock sample, it is rejected, resulting in crude oil samples after secondary screening. Re-Os isotope dating was performed on the crude oil samples after secondary screening to obtain the absolute age information of crude oil formation in the study area.

2. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, Quantitative fluorescence spectroscopy was performed on thin sections of inclusions corresponding to representative reservoir rock samples from each block of the study area to obtain the main fluorescence peak wavelength λmax of oil inclusions in reservoir rock samples covering the different fluorescence colors observed. The main fluorescence peak wavelength λmax data of oil inclusions in reservoir rock samples were plotted as a histogram of the main peak wavelength frequency distribution at 10 nm intervals.

3. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, All crude oil samples from the study area were subjected to group component separation in accordance with the industry standard "SY / T 5119—2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks".

4. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, All crude oil samples from the study area were subjected to group component separation and organic geochemical analysis to screen out outliers from different sources. This included gas chromatography-mass spectrometry (GC-MS) analysis of saturated hydrocarbons and aromatics, using C2... 22 TT / C 21 TT and C 24 TT / C 23 TT intersection chart, Ph / nC 18 With Pr / nC 17 Intersection diagram and C 27 -C 29 The ααα20R sterane ternary plot is used to screen the source of crude oil samples, resulting in crude oil samples after initial screening.

5. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, Using C 22 TT / C 21 TT and C 24 TT / C 23 TT intersection chart, Ph / nC 18 With Pr / nC 17 Intersection diagram and C 27 -C 29 The ααα20Rsterane ternary plot screens crude oil sample sources by: samples from the same source should be located in the same area on the plot; if an individual sample is located in a different area than the majority of samples on the plot, that individual sample is removed, resulting in crude oil samples after initial screening.

6. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, The quantitative spectral determination of crude oil samples after the initial screening includes: using a dropper to take 1-2 drops of the crude oil sample after the initial screening and drop them onto a new glass slide, then covering it with a coverslip, placing the slide under a microscope, and using a quantitative fluorescence spectrometer to perform quantitative spectral determination on each of the crude oil samples after the initial screening, and recording the wavelength λmax of the main fluorescence peak.

7. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, Also includes: In deep oil and gas basins, reservoir rock samples and crude oil samples from high-yield oil-bearing wells in representative blocks of the study area were obtained, and the well locations, burial depths, and stratigraphic information of the sample rock and crude oil samples were marked.

8. The method for screening crude oil Re-Os dating samples based on quantitative fluorescence spectroscopy according to claim 1, characterized in that, The polished reservoir rock sample inclusion sections were placed under a Nikon LV100N microscope equipped with a quantitative fluorescence spectrometer for fluid inclusion observation. By switching between different magnification fields of view to observe the fluorescence of the inclusions, oil inclusions were accurately located. Thin sections with concentrated inclusion development were selected at 10-20x magnification and photographed for preservation. Subsequently, quantitative fluorescence spectrometry was used to measure the fluorescence wavelength λmax of each oil inclusion in the selected field of view, and the main peak wavelength λmax was recorded. At the same time, it was ensured that the measurement objects included oil inclusions of different colors observed, and the number of oil inclusions tested was not less than 10. The obtained data were statistically analyzed using Origin and Excel data plotting software. The main peak wavelength λmax data of oil inclusion fluorescence were plotted as a histogram of the main peak wavelength frequency distribution at 10nm intervals.

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