Rock porosity calculation method and system based on clastic rock slice identification data

Abstract

The invention relates to a rock porosity calculation method and system based on clastic rock slice identification data, and belongs to the technical field of oil-gas exploration and geological engineering. The method comprises the following steps: obtaining a first compaction rate according to carbonate content data in current clastic rock slice identification data and a fitting relationship between carbonate content and compaction rate in historical data; obtaining a second compaction rate according to the clay contribution rate obtained by the current clastic rock slice identification data and the fitting relationship between the clay contribution rate and the compaction rate obtained by the historical data, and carrying out weighted average on the first compaction rate and the second compaction rate to obtain a comprehensive compaction rate; correcting the comprehensive compaction rate according to the ratio of the clay to the initial porosity and the ratio of the carbonate to the initial porosity to obtain a corrected compaction rate, determining the calculated porosity by using the corrected compaction rate, and correcting the calculated porosity according to the corrosion and cementation conditions of the slice to obtain the rock porosity; the clay contribution rate is the ratio of the square root of the clay content to the sum of the clay content and the carbonate content.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration and geological engineering, and particularly relates to a rock porosity calculation method and system based on clastic rock thin section identification data. Background Art

[0002] In geological exploration and rock engineering, accurate assessment of rock properties is crucial. Currently, there are two common methods for obtaining rock porosity: direct and indirect methods. The direct method involves saturating different fluid media and determining the rock pore volume by calculating the volume of the medium. The vacuuming and pressurizing saturation process takes a long time, and the detection cycle is long. The article titled "Research on Improving the Efficiency and Accuracy of Helium Porosity Detection" published by Li Jianzhi in the October 2023 issue of "China Petroleum and Chemical Standards and Quality" adopted the indirect method. The indirect method calculates the rock pore volume by measuring the apparent volume and skeleton volume of the rock. It mainly uses the helium method. For some rocks, it is difficult to accurately measure their apparent volume, and the measurement error is large. These two methods are greatly affected by factors such as human and equipment. Especially when the sample is difficult to obtain again, it is even more difficult to start and the pore size cannot be obtained.

[0003] To address these issues, Zhang Chuang, Sun Wei, and Gao Hui, et al., published a paper titled "Quantitative Calculation of Porosity Evolution in Sandstone Reservoirs Based on Cast Thin Section Data: A Case Study of the Chang 8 Reservoir in the Huanjiang Area of the Ordos Basin" in 2014 in the Journal of Sedimentology. They calculated the porosity of clastic sandstones based on the effects of compaction, early cementation, dissolution, and late cementation along the diagenetic evolution path. Zeng Binxin, Xiao Hui, Hao Zimei, et al., published a paper titled "Reservoir Porosity Prediction Based on a VAE-BiGRU-Attention Model: A Case Study of Medium- and Low-Permeability Sandstone Reservoirs" in 2024 in Progress in Geophysics. Based on well log data, they explored the relationship between well log information and porosity, optimized the algorithm to enhance data representation, and estimated porosity. While these methods address existing techniques affected by factors such as human effort and equipment, they also suffer from the large amount of data involved in the calculation process, resulting in low computational efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a rock porosity calculation method and system based on clastic rock thin section identification data, so as to solve the problem in the prior art that the amount of calculation data is large and the calculation efficiency is low.

[0005] To solve the above technical problems, the present invention provides a rock porosity calculation method based on clastic rock thin section identification data, the method comprising: obtaining a first compaction ratio based on carbonate content data in current clastic rock thin section identification data and a fitting relationship between carbonate content and compaction ratio in historical clastic rock thin section identification data; obtaining a second compaction ratio based on a clay contribution ratio obtained from current clastic rock thin section identification data and a fitting relationship between clay contribution ratio and compaction ratio obtained from historical clastic rock thin section identification data; performing weighted averaging on the first and second compaction ratios to obtain a comprehensive compaction ratio; correcting the comprehensive compaction ratio based on the ratio of clay to initial porosity and the ratio of carbonate to initial porosity to obtain a corrected compaction ratio; determining and calculating porosity using the corrected compaction ratio; and correcting the calculated porosity based on the dissolution and cementation conditions of the thin section to obtain rock porosity; the clay contribution ratio is the contribution ratio of clay to resistance to compaction.

[0006] Furthermore, the method of correcting the comprehensive compaction rate according to the clay-to-initial porosity ratio and the carbonate-to-initial porosity ratio to obtain the corrected compaction rate includes: if the clay-to-initial porosity ratio is greater than or equal to the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value is reduced to a first setting ratio of the current value; if the clay-to-initial porosity ratio is less than the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value remains unchanged; if the carbonate-to-initial porosity ratio is greater than or equal to the first setting value of the carbonate-to-initial porosity ratio and less than the second setting value of the carbonate-to-initial porosity ratio ... The value of the comprehensive compaction rate is reduced to the second set proportion of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the second set value of the ratio of carbonate to initial porosity and less than the third set value of the ratio of carbonate to initial porosity, the value of the comprehensive compaction rate is reduced to the third set proportion of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the third set value of the ratio of carbonate to initial porosity, the value of the comprehensive compaction rate is reduced to the fourth set proportion of the current value; the second, third and fourth set proportions decrease in sequence; if the ratio of carbonate to initial porosity is less than the first set value of the ratio of carbonate to initial porosity, the comprehensive compaction rate remains unchanged.

[0007] Furthermore, the method of correcting the calculated porosity according to the dissolution and cementation conditions of the thin section to obtain the rock porosity includes: if there is dissolution in the clastic rock thin section, the calculated porosity value is increased to the fifth set ratio of the current value; if there is no dissolution in the clastic rock thin section, the calculated porosity value remains unchanged; if the ratio of carbonate to initial porosity is greater than or equal to the first set value of cementation correction and less than the second set value of cementation correction, the calculated porosity value is reduced to the sixth set ratio of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the second set value of cementation correction, the calculated porosity value is reduced to the seventh set ratio of the current value; the seventh set ratio is less than the sixth set ratio; if the ratio of carbonate to initial porosity is less than the first set value of cementation correction, the calculated porosity value remains unchanged.

[0008] Furthermore, the method of determining and calculating the porosity using the corrected compaction ratio includes: determining and calculating the porosity according to the initial porosity, carbonate content, clay content and the corrected compaction ratio.

[0009] Furthermore, the porosity can be calculated based on the initial porosity, carbonate content, clay content, and corrected compaction ratio by:

[0010] POR=OP-CC 粘 -COR*(OP-C 粘 )

[0011] Where: POR is the calculated porosity, OP is the initial porosity, C is the carbonate content, C 粘 is the clay content and COR is the corrected compaction ratio.

[0012] Furthermore, the clay contribution is determined by the clay content and the carbonate content.

[0013] Furthermore, methods for determining the clay contribution rate through clay content and carbonate content include:

[0014]

[0015] Where CCR is the clay contribution rate, C is the carbonate content, and C 粘 Clay content.

[0016] To solve the above technical problems, the present invention also provides a rock porosity calculation system based on clastic rock thin section identification data, including a processor, which is used to execute a computer program to implement the steps of the rock porosity calculation method based on clastic rock thin section identification data.

[0017] The beneficial effects of the above technical solution are as follows: the present invention provides a rock porosity calculation method based on clastic rock thin section identification data, by respectively calculating the corresponding first compaction rate and second compaction rate according to the carbonate content and clay contribution rate, and performing weighted average of the first compaction rate and the second compaction rate to obtain a comprehensive compaction rate, that is, the relationship between the two influencing factors with the best correlation with the compaction rate obtained by comprehensive analysis and the compaction rate obtained by fitting historical data, and the compaction rate is calculated to obtain a comprehensive compaction rate, so that the calculation result of the obtained comprehensive compaction rate is more in line with the actual situation, and then the comprehensive compaction rate is corrected. The geological basis for the correction is the clay and carbonate content that resist compaction, which can be used to calculate the comprehensive compaction rate. According to the degree to which the actual clay and carbonate content resists compaction, the compaction rate is adjusted accordingly for correction. The porosity is then determined and calculated using the corrected compaction rate. The calculated porosity is then corrected based on the dissolution and cementation conditions of the thin section to obtain the rock porosity. Thin section dissolution increases pores, while cementation reduces pores. The calculated porosity can be adjusted accordingly for correction based on the actual dissolution and cementation conditions of the thin section. It can be seen that the rock porosity calculation method can obtain the rock porosity by calculating and correcting the relevant parameters of the carbonate content and clay content in the clastic rock thin section identification data. On the basis of ensuring accuracy, it solves the problem of low calculation efficiency caused by the large amount of calculation data in the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic flow chart of a rock porosity calculation method based on clastic rock thin section identification data according to an embodiment of the present invention;

[0019] Figure 2 This is a fitting diagram of the coupled relationship between carbonate content and compaction rate in an embodiment of a rock porosity calculation method based on clastic rock thin section identification data of the present invention;

[0020] Figure 3 This is a fitting diagram of the coupled relationship between clay contribution rate and compaction rate in the rock porosity calculation method based on clastic rock thin section identification data according to an embodiment of the present invention;

[0021] Figure 4 This is a table of error determination between the predicted rock porosity and the measured rock porosity of the rock porosity calculation method based on clastic rock thin section identification data in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Example of a rock porosity calculation method based on clastic rock thin section identification data:

[0024] The present embodiment provides a rock porosity calculation method based on clastic rock thin section identification data. Fitting analysis is performed on the factors and compaction rate of the clastic rock thin section to obtain two influencing factors with the best correlation with the compaction rate. The two influencing factors are the carbonate content and the clay contribution rate. The corresponding compaction rates are calculated based on the carbonate content and the clay contribution rate of the current clastic rock thin section through their corresponding fitting relationships. The compaction rates are then adjusted accordingly based on the degree to which the actual clay and carbonate contents resist the compaction rate. The calculated porosity is then determined using the corrected compaction rate. Since thin section dissolution increases porosity and cementation reduces porosity, the calculated porosity is corrected based on the actual dissolution and cementation conditions of the thin section to obtain the rock porosity. This solves the problem of low calculation efficiency caused by the large amount of calculation data in the prior art while ensuring accuracy.

[0025] The rock porosity calculation method based on clastic rock thin section identification data is as follows: Figure 1 As shown, it mainly includes:

[0026] A first compaction ratio is obtained based on the carbonate content data from the current clastic rock thin section identification data and the fitting relationship between the carbonate content and compaction ratio from the historical clastic rock thin section identification data. A second compaction ratio is obtained based on the clay contribution ratio from the current clastic rock thin section identification data and the fitting relationship between the clay contribution ratio and compaction ratio from the historical clastic rock thin section identification data. The first and second compaction ratios are weighted averaged to obtain a comprehensive compaction ratio. The comprehensive compaction ratio is corrected according to the ratio of clay to initial porosity and the ratio of carbonate to initial porosity to obtain a corrected compaction ratio. The calculated porosity is determined using the corrected compaction ratio. The calculated porosity is corrected according to the dissolution and cementation conditions of the thin section to obtain the rock porosity. The clay contribution ratio is the contribution ratio of clay to resistance to compaction.

[0027] In this embodiment, the first compaction rate and the second compaction rate corresponding to the carbonate content and the clay contribution rate are calculated respectively, and the first compaction rate and the second compaction rate are weighted averaged to obtain the comprehensive compaction rate, that is, the relationship between the two influencing factors with the best correlation with the compaction rate obtained by comprehensive analysis and the compaction rate is obtained by fitting historical data respectively, and the compaction rate is calculated to obtain the comprehensive compaction rate, so that the calculation result of the comprehensive compaction rate is more in line with the actual situation, and then the comprehensive compaction rate is corrected. The geological basis for the correction is the clay and carbonate content that resists compaction, and the actual clay and carbonate content can resist compaction. The degree of thin section dissolution increases pores, while cementation reduces pores. The calculated porosity can be adjusted accordingly based on the degree of dissolution and cementation of the thin section. It can be seen that the rock porosity calculation method can obtain the rock porosity by calculating and correcting the relevant parameters of carbonate content and clay content in the clastic rock thin section identification data. On the basis of ensuring accuracy, it solves the problem of low calculation efficiency caused by the large amount of calculation data in the existing technology.

[0028] Specifically, the clastic rock thin section identification data and compaction rate were fitted, and parameters sensitive to the compaction rate were found through data fitting. The parameters sensitive to the compaction rate include carbonate content and clay contribution rate. The fitting relationship between carbonate content and compaction rate is shown in Figure 2 , correlation coefficient R 2 It reaches 0.8787, indicating that the two have a good coupling relationship. Multi-parameters can help eliminate the error of a sensitive parameter. The fitting relationship between clay contribution rate and compaction rate is shown in Figure 3 , correlation coefficient R 2 It reaches 0.7997, indicating that the two have a good coupling relationship.

[0029] In this embodiment, the clay contribution rate is determined by the clay content and the carbonate content.

[0030] Methods for determining clay contribution from clay and carbonate content include:

[0031]

[0032] Where CCR is the clay contribution rate, C is the carbonate content, and C 粘 Clay content.

[0033] Specifically, the clay contribution rate (CCR) refers to the fact that the clay matrix in sandstone reduces OP after deposition, but also contributes to the reduction of the compaction rate during later compaction. Clay and carbonates play a positive role in resisting compaction. Because clay's support role in resisting compaction is far less than that of carbonates, the square root of its content has a better correlation with the compaction rate. Therefore, the square root of the clay content is used here.

[0034] In this embodiment, the method of determining and calculating the porosity using the corrected compaction ratio includes: determining and calculating the porosity according to the initial porosity, carbonate content, clay content, and the corrected compaction ratio.

[0035] Methods for calculating porosity based on initial porosity, carbonate content, clay content, and corrected compaction ratio include:

[0036] POR=OP-CC 粘 -COR*(OP-C 粘 )

[0037] Where: POR is the calculated porosity, OP is the initial porosity, C is the carbonate content, C 粘 is the clay content and COR is the corrected compaction ratio.

[0038] Specifically, according to Figure 2 and Figure 3 The corresponding compaction ratios are calculated using the fitting relationship in

[15] . A weighted average is then taken based on their correlation coefficients (in this example, the weight of carbonate content is 0.8; the weight of clay contribution is 0.2). The weighted averaged comprehensive compaction ratio is then corrected, and the calculated porosity (POR) is calculated based on the corrected compaction ratio (COR). The calculated porosity (POR) is then corrected to obtain the rock porosity.

[0039] In this embodiment, the method of correcting the comprehensive compaction rate according to the clay-to-initial porosity ratio and the carbonate-to-initial porosity ratio to obtain the corrected compaction rate includes: if the clay-to-initial porosity ratio is greater than or equal to the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value is reduced to a first setting ratio of the current value; if the clay-to-initial porosity ratio is less than the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value remains unchanged; if the carbonate-to-initial porosity ratio is greater than or equal to the first setting value of the carbonate-to-initial porosity ratio and less than the second setting value of the carbonate-to-initial porosity ratio, then the comprehensive compaction rate value is increased. The value of the compaction rate is reduced to a second set ratio of the current value; if the carbonate ratio to the initial porosity is greater than or equal to the second set value of the carbonate ratio to the initial porosity and less than the third set value of the carbonate ratio to the initial porosity, the value of the comprehensive compaction rate is reduced to a third set ratio of the current value; if the carbonate ratio to the initial porosity is greater than or equal to the third set value of the carbonate ratio to the initial porosity, the value of the comprehensive compaction rate is reduced to a fourth set ratio of the current value; the second, third, and fourth set ratios decrease in sequence; if the carbonate ratio to the initial porosity is less than the first set value of the carbonate ratio to the initial porosity, the comprehensive compaction rate remains unchanged. In this embodiment, the clay ratio to the initial porosity is set to 0.2, the first set ratio is 0.99, the carbonate ratio to the initial porosity is set to 0.1, the carbonate ratio to the initial porosity is set to 0.2, the second set ratio is 0.995, the carbonate ratio to the initial porosity is set to 0.4, the third set ratio is 0.99, and the fourth set ratio is 0.98, as shown in Table 1.

[0040] The method of correcting the calculated porosity to obtain rock porosity based on the dissolution and cementation conditions of the thin section includes: if the clastic rock thin section exhibits dissolution, the calculated porosity value is increased to a fifth set ratio of the current value; if the clastic rock thin section does not exhibit dissolution, the calculated porosity value remains unchanged; if the carbonate ratio of the initial porosity is greater than or equal to the first set value of the cementation correction and less than the second set value of the cementation correction, the calculated porosity value is reduced to a sixth set ratio of the current value; if the carbonate ratio of the initial porosity is greater than or equal to the second set value of the cementation correction, the calculated porosity value is reduced to a seventh set ratio of the current value; the seventh set ratio is less than the sixth set ratio; if the carbonate ratio of the initial porosity is less than the first set value of the cementation correction, the calculated porosity value remains unchanged. In this embodiment, the fifth set ratio is 1.03, the first set value of the cementation correction is 0.2, the second set value of the cementation correction is 0.4, the sixth set ratio is 0.95, and the seventh set ratio is 0.9, as shown in Table 1.

[0041] Specifically, the first round of correction is for the weighted average of the comprehensive compaction rate COR. The geological basis for the correction is the clay and carbonate content that resists compaction. Of course, the higher the better, the better. While resisting compaction, it will also cement the sandstone, thereby reducing porosity. 粘 and the carbonate ratio of initial porosity R 碳 The correction factors are determined as shown in Table 1. The second round of correction is for the calculated porosity POR. After the calculated porosity POR is calculated using the corrected compaction ratio COR, dissolution correction and cementation correction are performed. Dissolution increases porosity while cementation reduces porosity. The dissolution correction factor is determined by observing the thin section of the clastic rock to determine whether there is dissolution; the cementation correction factor is based on the ratio of carbonate to initial porosity R 碳 value to determine.

[0042] Table 1

[0043]

[0044] Comparing the predicted rock porosity after two corrections with the actual porosity of clastic rock thin sections, the absolute error is -1.52% to 1.04%, with an average of -0.01%, and the maximum relative error is 0.15% to 21%, with an average of 10.28%, which has good accuracy. Figure 4 shown.

[0045] Example of a rock porosity calculation system based on clastic rock thin section identification data:

[0046] A rock porosity calculation system based on clastic rock thin section identification data includes a processor configured to execute a computer program to implement the steps of a rock porosity calculation method based on clastic rock thin section identification data. The specific process, principles, and effects of the rock porosity calculation system based on clastic rock thin section identification data have been described in detail in the embodiment of the rock porosity calculation method based on clastic rock thin section identification data and will not be repeated here.

[0047] While specific embodiments have been described above, the present invention is not limited to the described embodiments. The fundamental concept of the present invention lies in the aforementioned basic scheme. Based on the teachings of the present invention, those skilled in the art can devise various variations of models, formulas, and parameters without inventive effort. Changes, modifications, substitutions, and variations to the embodiments without departing from the principles and spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A rock porosity calculation method based on clastic rock thin section identification data, characterized in that: The method includes: obtaining a first compaction rate based on carbonate content data in current clastic rock thin section identification data and a fitting relationship between carbonate content and compaction rate in historical clastic rock thin section identification data; obtaining a second compaction rate based on a clay contribution rate obtained from current clastic rock thin section identification data and a fitting relationship between clay contribution rate and compaction rate obtained from historical clastic rock thin section identification data; performing weighted averaging on the first and second compaction rates to obtain a comprehensive compaction rate; correcting the comprehensive compaction rate based on a clay-to-initial porosity ratio and a carbonate-to-initial porosity ratio to obtain a corrected compaction rate; determining and calculating porosity using the corrected compaction rate; and correcting the calculated porosity based on the dissolution and cementation conditions of the thin section to obtain rock porosity; the clay contribution rate is a contribution rate of clay to resistance to compaction.

2. The rock porosity calculation method based on clastic rock thin section identification data according to claim 1 is characterized in that: The method of correcting the comprehensive compaction rate according to the clay-to-initial porosity ratio and the carbonate-to-initial porosity ratio to obtain the corrected compaction rate includes: if the clay-to-initial porosity ratio is greater than or equal to the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value is reduced to a first setting ratio of the current value; if the clay-to-initial porosity ratio is less than the clay-to-initial porosity ratio setting value, then the comprehensive compaction rate value remains unchanged; if the carbonate-to-initial porosity ratio is greater than or equal to the first setting value of the carbonate-to-initial porosity ratio and less than the second setting value of the carbonate-to-initial porosity ratio, then the comprehensive compaction rate value is increased. The value of the comprehensive compaction rate is reduced to the second set proportion of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the second set value of carbonate to initial porosity and less than the third set value of carbonate to initial porosity, the value of the comprehensive compaction rate is reduced to the third set proportion of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the third set value of carbonate to initial porosity, the value of the comprehensive compaction rate is reduced to the fourth set proportion of the current value; the second, third and fourth set proportions decrease in turn; if the ratio of carbonate to initial porosity is less than the first set value of carbonate to initial porosity, the comprehensive compaction rate remains unchanged.

3. The rock porosity calculation method based on clastic rock thin section identification data according to claim 1 or 2, characterized in that: The method of correcting the calculated porosity according to the dissolution and cementation conditions of the thin section to obtain the rock porosity includes: if there is dissolution in the clastic rock thin section, the calculated porosity value is increased to the fifth set ratio of the current value; if there is no dissolution in the clastic rock thin section, the calculated porosity value remains unchanged; if the ratio of carbonate to initial porosity is greater than or equal to the first set value of cementation correction and less than the second set value of cementation correction, the calculated porosity value is reduced to the sixth set ratio of the current value; if the ratio of carbonate to initial porosity is greater than or equal to the second set value of cementation correction, the calculated porosity value is reduced to the seventh set ratio of the current value; the seventh set ratio is less than the sixth set ratio; if the ratio of carbonate to initial porosity is less than the first set value of cementation correction, the calculated porosity value remains unchanged.

4. The rock porosity calculation method based on clastic rock thin section identification data according to claim 1 or 2, characterized in that: The method of determining and calculating the porosity using the modified compaction ratio includes: determining and calculating the porosity according to the initial porosity, carbonate content, clay content and the modified compaction ratio.

5. The rock porosity calculation method based on clastic rock thin section identification data according to claim 4 is characterized in that: Methods for calculating porosity based on initial porosity, carbonate content, clay content, and corrected compaction ratio include: POR=OP-CC 粘 -COR*(OP-C 粘 ) Where: POR is the calculated porosity, OP is the initial porosity, C is the carbonate content, C 粘 is the clay content and COR is the corrected compaction ratio.

6. The rock porosity calculation method based on clastic rock thin section identification data according to claim 1 or 2, characterized in that: The clay contribution rate is determined by the clay content and the carbonate content.

7. The rock porosity calculation method based on clastic rock thin section identification data according to claim 6 is characterized in that: Methods for determining the clay contribution rate by clay content and carbonate content include: Where CCR is the clay contribution rate, C is the carbonate content, and C 粘 Clay content.

8. A rock porosity calculation system based on clastic rock thin section identification data, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the rock porosity calculation method based on clastic rock thin section identification data as described in any one of claims 1 to 7.

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