Strong mineral interference and unconventional oily reservoir quantitative fluorescence experiment method

Abstract

The invention discloses a strong mineral interference and unconventional oily reservoir quantitative fluorescence experiment method which comprises the following steps: selecting a cleaned sample reservoir particle quantitative fluorescence analysis test, and taking a result as an original blank sample QGF index value; repeatedly grinding and thoroughly crushing the cleaned sample until the particle size is less than 30 microns; the standing time of spectroscopically pure dichloromethane is optimized to ensure that hydrocarbons released by the inclusion are fully extracted; a standard slice is manufactured, inclusion retention is observed under a fluorescence microscope, if the inclusion is observed under the microscope, further grinding and soaking are needed, if no inclusion exists, reservoir particle quantitative fluorescence analysis testing is conducted, and the testing result is the mineral QGF index value; and calculating the QGF index value of the inclusion, wherein the QGF index value is the difference value between the QGF index value of the original blank sample and the QGF index value of the mineral. According to the method, interference caused by the fact that mineral fluorescence and calculation errors are not considered in a traditional reservoir particle quantitative fluorescence experiment method is corrected.

Description

Technical Field

[0001] The invention relates to the field of geochemical experiments, and in particular to a quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties. Background Art

[0002] Oil and gas inclusions are the most important objects in the study of oil and gas reservoir history, providing information such as fluid temperature, pressure, composition and intensity during oil and gas migration and filling. Oil and gas inclusions mainly contain alkanes (methane, ethane, propane, etc.), aromatic compounds, crude oil and asphalt. It preserves information about the formation of oil and gas reservoirs such as the composition and properties of the trapped fluid. Reservoir particle fluorescence technology detects ancient oil layers by measuring the fluorescence intensity of hydrocarbon substances in quartz and feldspar particles excited by ultraviolet light. Different hydrocarbons have different spectral characteristics. This technology can help identify the presence of oil inclusions in samples. It can also be used to identify the oil and gas content of reservoirs, judge current oil layers and ancient oil layers, analyze oil and gas properties, track oil and gas migration paths, etc. It has been widely used in domestic oil and gas reservoir research.

[0003] However, in practical applications, due to the interference of mineral fluorescence, when the quantitative fluorescence test of reservoirs is combined with logging and mud logging data to identify the properties of reservoir fluids, the analysis results are uncertain and have multiple solutions. In addition, the interpretation results of ancient oil layers, water layers, dry layers and ancient oil-water interfaces are inconsistent with geological research, which has hindered technological development and production needs. Summary of the invention

[0004] In order to solve the problem that it is difficult to determine the properties of reservoir fluids and that the analysis results are multi-solutions when identifying ancient oil layers, water layers, dry layers and ancient oil-water interfaces, the present invention provides a quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties to assist in oil and gas reservoir evaluation research and related production needs.

[0005] The present invention is achieved by adopting the following technical solutions.

[0006] A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties, comprising the following steps:

[0007] S1. Select the cleaned experimental sample, add spectrally pure dichloromethane, and directly perform the reservoir particle quantitative fluorescence analysis test after the free and adsorbed hydrocarbons are extracted. The test result is used as the QGF index value of the original blank sample; select another sample that has been cleaned before pretreatment and continue to the next step;

[0008] S2. Grind the sample repeatedly and thoroughly crush it to a particle size less than 30 μm to ensure that the inclusions in the sample particles are completely destroyed;

[0009] S3. The sample and spectrally pure dichloromethane are prepared in a mass ratio of 1:40 to 1:50, and then ultrasonicated for 10 to 20 minutes and then allowed to stand for 10 to 20 minutes to extract free hydrocarbons on the particle surface and hydrocarbons released after the inclusions are destroyed;

[0010] S4. Dry the sample, make a standard sheet, and observe the inclusions under a fluorescence microscope. If oil inclusions can be observed, repeat steps S2 and S3, and reduce the sample particle size by 10 μm until no inclusions are present inside.

[0011] S5. Select a powder sample without internal inclusions and conduct a quantitative fluorescence analysis test of reservoir particles. The test result is the mineral QGF index value;

[0012] S6. The QGF index value of the inclusions inside the sample is the difference between the QGF index value of the original blank sample measured in step S1 and the QGF index value of the mineral measured in step S5, that is, the QGF index value of the inclusions = the QGF index value of the original blank sample - the QGFindex value.

[0013] Furthermore, in step S1, the experimental sample is one or more of rock cuttings, wall cores and rock cores, preferably rock cores; the coring cost in the Bohai Sea area is high and clean rock cuttings can be used instead.

[0014] Furthermore, in step S1, the experimental sample is pre-treated and cleaned with multiple reagents and multiple stages.

[0015] Specifically, the pretreatment operation includes the following steps: washing with distilled water, sampling, extracting free hydrocarbons on the particle surface with spectrally pure dichloromethane; washing clay and adsorbed hydrocarbons on the particle surface with hydrogen peroxide, and repeatedly washing with distilled water; washing carbonate cement with dilute hydrochloric acid (this step is omitted for carbonate rock samples), and repeatedly washing with distilled water.

[0016] Further, in step S1, the mass volume ratio of the experimental sample to the spectrally pure dichloromethane is 1 / 20 g / ml-1 / 30 g / ml. Preferably, the mass volume ratio of the experimental sample to the spectrally pure dichloromethane is 1 / 20 g / ml.

[0017] Furthermore, in step S1, the extraction time of free and adsorbed hydrocarbons is 5 minutes.

[0018] Further, in step S3, the method for determining the standing soaking time of spectrally pure dichloromethane is as follows:

[0019] Add multiple samples to spectrally pure dichloromethane and ultrasonicate for 10 to 20 minutes, then let them soak for 0.5h, 1h, 2h, 4h, 8h, 16h, 24h, and 30h respectively. After soaking, wash them repeatedly with distilled water, dry them, and conduct quantitative fluorescence analysis test of reservoir particles. Calculate the reduction of QGF index based on the QGF index value corresponding to the large soaking time and the adjacent small soaking time, and determine the final soaking time with the large soaking time corresponding to the 1% reduction of QGF index. The large soaking time and small soaking time described in this application refer to the two adjacent soaking times, the longer time is the large soaking time, and the shorter time is the small soaking time. Taking the two adjacent soaking times of 0.5h and 1h as examples, 0.5h is the small soaking time and 1h is the large soaking time; taking the two adjacent soaking times of 1h and 2h as examples, 1h is the small soaking time and 2h is the large soaking time.

[0020] Furthermore, in step S3, the spectrally pure dichloromethane is allowed to stand and soak for 30 hours.

[0021] Furthermore, in step S4, the specific method for making a standard slice and observing it under a microscope is as follows: flatten the soaked sample, fix it into shape with non-fluorescent 502 strong glue, further coarsely grind, finely grind, and finely grind it to a slice thickness of 0.05mm-0.1mm, and finally double-sided polish it until it is as bright as a mirror without scratches; observe the polished slice interactively under a microscope using fluorescent transmitted light, analyze the inclusions retained, and confirm whether the particles should be further ground and crushed.

[0022] Furthermore, after testing each parameter, observe the spectrum before calculation. For normal oil, calculate directly. For light oil and heavy oil shown in the ancient reservoir spectrum, the QGF intensity (QGF intensity) should be calculated as the average of the spectral intensity in the 50nm interval before and after λmax. For samples with QGF intensity less than 2 and 300nm spectral intensity less than 0.1, it is not recommended to use the QGFindex parameter for geological evaluation. The QGF index is calculated as the ratio of the QGF intensity value to the fluorescence intensity value at a wavelength of 300nm.

[0023] This application has the following beneficial effects.

[0024] The method of the present invention removes the interference of mineral fluorescence by grinding and crushing the inclusions of the cleaned sample, fully extracting the inclusions with spectrally pure dichloromethane to release hydrocarbons, and calculating the difference to obtain the mineral fluorescence intensity, thereby correcting the test results of the traditional reservoir quantitative fluorescence experiment to a large extent and improving the credibility of the analysis results. The test results can be combined with the well logging and oil test results in the study area to more accurately identify the oil-water interface and restore the oil and gas filling history. The method of the present invention has been applied in the Bohai Oilfield, greatly improving the value of the experimental method in geochemical experimental research and providing auxiliary technical support for oil and gas reservoir evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the experimental method of the present invention;

[0026] Figure 2 This is a test data diagram of the quantitative fluorescence experiment of the Bohai Oilfield reservoir in an embodiment of the present invention;

[0027] Figure 3 This is the original total fluorescence test graph of sample BZ-A (2085-2090m) in the embodiment of the present invention;

[0028] Figure 4 It is the QGF test spectrum of the oil and gas two-stage filling of the ancient oil reservoir of the well CFD-23 of the embodiment of the present invention;

[0029] Figure 5 This is the QGF test diagram of the ancient oil reservoir of Well BZ-22 of the present invention. DETAILED DESCRIPTION

[0030] The present patent application is further described below in conjunction with embodiments.

[0031] Unless otherwise specified, the experimental methods used in the following preparation examples and examples are all conventional methods; the materials, reagents, etc. used in the following preparation examples and examples are all commercially available unless otherwise specified.

[0032] The present invention corrects the inclusion QGF index value by fully crushing the reservoir particle inclusions that have been cleaned by standard pretreatment, preferably standing for a period of time with spectrally pure dichloromethane, completely extracting the hydrocarbons in the inclusion powder, cleaning and making standard thin slices, observing the inclusion retention under a microscope, and calculating the mineral QGF index value. Compared with the traditional reservoir particle quantitative fluorescence experimental method (standard pretreatment cleaning, direct testing of inclusion QGF index value), the present invention fully considers and reduces the impact of mineral interference on inclusion testing, which is conducive to the promotion and application of reservoir particle quantitative fluorescence technology in oil and gas resource evaluation and exploration in complex oil and gas blocks.

[0033] In Example 1 of the present invention, 9 clean cuttings were taken from the Bohai Oilfield for comparative evaluation, including the well sections 1640-1645m, 1935-1940m, and 2085-2090m in the BZ-A block; the well sections 1485-1490m, 1620-1625m, and 2505-2510m in the KL-B block; and the well sections 3360-3370m, 3470-3480m, and 3500-3510m in the QHD-C block.

[0034] The experimental method of reducing mineral fluorescence interference is used to process experimental samples and conduct quantitative fluorescence analysis and evaluation of reservoirs, including the following steps:

[0035] Step 1: Pre-treatment and cleaning of experimental samples

[0036] First, prepare the experimental reagents, including analytical pure dichloromethane, analytical pure hydrochloric acid, analytical pure hydrogen peroxide and distilled water. Distill the analytical pure dichloromethane and test QGF-E with Cary Eclipse fluorescence spectrophotometer. The purity is no more than 10pc, which meets the requirements.

[0037] Then, the samples are crushed. For clastic reservoir samples, they need to be crushed into particles with a size of 0.063mm to 1mm, and then washed with distilled water for multiple times to clean the suspended sediment. After drying, they are screened again to ensure that the particle size is in the range of 0.063mm to 1mm. For carbonate rock samples, the same grinding and washing operation is performed, but the particle size is 0.1mm to 0.3mm.

[0038] After that, use a magnetic separator or manually select under a microscope to retain pure quartz or feldspar particles. Weigh about 2g of the sample and add 20mL of distilled and purified dichloromethane to extract free hydrocarbons on the surface of the particles. Dry naturally and add 40mL of 10% hydrogen peroxide. Ultrasonicate for 10min, let stand for 40min and then ultrasonicate for 10min. After completion, wash with distilled water three times or more until the residue dissolved by the hydrogen peroxide is washed clean. Then add 40mL of 3.6% dilute hydrochloric acid, ultrasonicate for 10min, pour out the hydrochloric acid solution in the beaker, add distilled water to wash the sample three times, and dry it in a constant temperature box with a temperature not higher than 60℃.

[0039] Finally, all samples after cleaning were subjected to QGF test, and the test results were taken as the original total fluorescence intensity.

[0040] Step 2: Sample grinding and inclusion crushing

[0041] First, select the well sections 1640-1645m, 1935-1940m, 2085-2090m of the BZ-A block that have been cleaned in step 1; the well sections 1485-1490m, 1620-1625m, 2505-2510m of the KL-B block; and the well sections 3360-3370m, 3470-3480m, 3500-3510m of the QHD-C block, each weighing 2g.

[0042] Then, use The three-head grinder grinds the samples into powder for 20 minutes. The minimum D50 of the 9 samples tested is 3.18 μm, and the minimum D50 is 25.62 μm.

[0043] Step 3: Optimal extraction time of dichloromethane

[0044] Add 40 mL of spectrally pure dichloromethane to the powder sample obtained in step 2 and soak for 0.5 h, 1 h, 2 h, 4 h, 8 h, 16 h, 24 h, and 30 h. As the soaking and extraction time of spectrally pure dichloromethane increases, the QGF index value of the sample decreases by 0.56% to 24.50% after 24 hours of extraction, with an average decrease of 9.46%; and after 30 hours of extraction, the QGF index value decreases by 0.37% to 0.52%, with an average decrease of 0.25%. Obviously, the QGFindex value of the sample soaked and extracted for 30 hours can reach the lower limit, at which time the hydrocarbons released by the destruction of the inclusions are fully extracted by dichloromethane.

[0045] Step 4: Observe the inclusions under the microscope

[0046] The samples in step 3 were washed and dried with distilled water for many times. They were fixed with non-fluorescent 502 strong glue, and further coarsely ground, finely ground, and finely ground to a slice thickness of 0.05mm-0.1mm. Finally, double-sided polishing was performed until it was as bright as a mirror without scratches. The polished slices were observed under a microscope with fluorescence transmission light to analyze the inclusions to confirm whether the particles should be further ground and crushed. In the experiment, 9 samples were observed under a microscope with partial mineral fluorescence but no inclusion fluorescence.

[0047] Step 5: Reservoir particle quantitative fluorescence analysis test

[0048] 1 g of powder sample without internal inclusions was selected for quantitative fluorescence analysis test of reservoir particles, and the test result was the mineral QGF index value; the QGF index value of the inclusions inside the sample was the difference between the QGF index value of the original blank sample measured in step 1 and the mineral QGF index value measured in step 5, that is, the inclusion QGF index value = the original blank sample QGF index value - QGFindex value.

[0049] The experimental sample test calculation data is shown in Table 1. Figure 2 .

[0050] Table 1 Quantitative fluorescence experimental test data of Bohai Oilfield reservoir

[0051]

[0052] From Table 1, Figure 2 It can be seen that the inclusion fluorescence intensity tested by the traditional reservoir quantitative fluorescence experimental method is the original total fluorescence in the chart, and the QGF index is in the range of 4.2-9.9, which indicates the ancient oil layer, and can further infer the existence of the ancient oil reservoir. The inclusion fluorescence tested by the sample treated by the experimental method of reducing mineral fluorescence interference of the present invention is the actual inclusion fluorescence, and the inclusion QGF index is in the range of 0.4-6.2. The results show that the actual inclusion QGF index value of sample KL-B (2505-2510m) is only 0.4, which is difficult to be judged as an ancient oil reservoir. However, due to the influence of mineral fluorescence, the inclusion QGF index value tested by the traditional method reaches 4.2, which will be misjudged as an ancient oil layer. For example, samples BZ-A (1640-1645m) and BZ-A (2085-2090m) are also misjudged due to high mineral fluorescence values. The mineral intensity of 7 out of 9 experimental samples is greater than or approximately equal to the inclusion fluorescence, which shows that the mineral fluorescence intensity greatly interferes with the quantitative fluorescence application of reservoirs that uses the original total fluorescence as the inclusion fluorescence. In practical applications, it is necessary to remove the mineral fluorescence and only focus on the inclusion fluorescence itself.

[0053] Example 2 of the present invention carries out QGF index parameter optimization calculation, and analyzes the CFD-23 well and the BZ-22 well:

[0054] According to the analysis of a large number of quantitative fluorescence experiments on reservoirs, the distortion of QGF index geological application is mainly reflected in three aspects. First, the secondary filling of oil and gas in the ancient oil reservoir is strong, and the late light oil and gas filling is the main one. The test shows that the fluorescence intensity between 375 and 475nm is low, and λmax is less than 375nm; second, the oil quality of the ancient oil reservoir is heavy, and the fluorescence peak is relatively late; third, the fluorescence intensity of the entire wavelength range (300-600nm) is weak, but the QGF index calculation has a large calculation error due to the lower spectral intensity at the starting point of 300nm (<0.1), showing a high pseudo-QGF value. Quantitative fluorescence analysis results of the ancient oil reservoir in CFD-23 well ( Figure 4) It can be seen that the QGFintensity is 6.7, the sample inclusion fluorescence abundance is high, and the test results show obvious oil and gas, but the QGF index is only 1.2. This is because the late light oil filling causes the spectrum peak to move forward, the fluorescence intensity value at 300nm is high, and the fluorescence intensity between 375 and 475nm is weak, resulting in a low QGF index calculation value, which is inconsistent with the high abundance of oil and gas in the ancient oil reservoir. Quantitative fluorescence analysis results of the ancient oil reservoir in Well BZ-22 ( Figure 5 ) It can be seen that the overall fluorescence intensity of the ancient oil reservoir is low and the oil and gas display is weak, but the QGFindex is greater than 5 as a whole. According to the discrimination criteria, it is judged to be an ancient oil reservoir, which is inconsistent with the low QGF intensity and low fluorescence intensity of each wavelength. The main reason is the calculation distortion caused by the low fluorescence intensity value at 300nm.

[0055] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties. It is characterized in that The following steps are involved: S1. Select the cleaned experimental sample, add spectrally pure dichloromethane, and directly perform the reservoir particle quantitative fluorescence analysis test after the free and adsorbed hydrocarbons are extracted. The test result is used as the QGF index value of the original blank sample; select another sample that has been cleaned before pretreatment and continue to the next step; S2. Grind the sample repeatedly until the particle size is less than 30 μm; S3. The sample and spectrally pure dichloromethane are prepared in a mass ratio of 1:40 to 1:50, and then ultrasonicated for 10 to 20 minutes and then allowed to stand for 10 to 20 minutes to extract free hydrocarbons on the particle surface and hydrocarbons released after the inclusions are destroyed; S4. Dry the sample, make a standard sheet, and observe the inclusions under a fluorescence microscope. If oil inclusions can be observed, repeat steps S2 and S3, and reduce the sample particle size by 10 μm until no inclusions are present inside. S5. Select a powder sample without internal inclusions and conduct a quantitative fluorescence analysis test of reservoir particles. The test result is the mineral QGF index value; S6. The QGF index value of the inclusions inside the sample is the difference between the QGF index value of the original blank sample measured in step S1 and the QGF index value of the mineral measured in step S5.

2. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties according to claim 1, It is characterized in that In step S1, the experimental sample is pre-treated and cleaned with multiple reagents and multiple stages.

3. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties according to claim 1, It is characterized in that In step S1, the mass volume ratio of the experimental sample to spectrally pure dichloromethane is 1 / 20 g / ml-1 / 30 g / ml.

4. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties according to claim 1, It is characterized in that In step S3, the method for determining the standing soaking time of spectrally pure dichloromethane is as follows: Multiple samples were added to spectrally pure dichloromethane and ultrasonically treated for 10-20 minutes, then allowed to soak for 0.5h, 1h, 2h, 4h, 8h, 16h, 24h and 30h respectively. After soaking, they were repeatedly washed with distilled water and dried for quantitative fluorescence analysis of reservoir particles. The QGF index reduction was calculated based on the QGF index values ​​corresponding to the maximum soaking time and the adjacent small soaking time, and the maximum soaking time corresponding to a 1% reduction in QGF index was determined as the final soaking time.

5. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties according to claim 1, It is characterized in that In step S3, the spectrally pure dichloromethane is allowed to stand and soak for 30 hours.

6. A quantitative fluorescence experimental method for reservoirs with strong mineral interference and unconventional oil properties according to claim 1, It is characterized in that After testing each parameter, observe the spectrum before calculation. For normal oil, calculate directly. For light oil and heavy oil shown in the ancient oil reservoir spectrum, the QGF intensity should be calculated as the average value of the spectral intensity in the 50nm interval before and after λmax. The QGFindex is calculated as the ratio of the QGF intensity value to the fluorescence intensity value at a wavelength of 300nm.

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