Method for acquiring Young modulus and Poisson's ratio while drilling based on fractal dimension of rock debris
Through the calculation of the dimensions of the fragment fractal dimensions and the establishment of the correlation model, the problem of poor timeliness and high cost of data acquisition of rock Young's modulus and Poisson's ratio in oil drilling and drilling is solved, and efficient and low-cost data acquisition is achieved, which is a reservoir. The evaluation of rock mechanics parameters provides support.
Patent Information
- Application Number
- CN202310971972.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-03
- Publication Date
- 2025-02-14
AI Technical Summary
The prior art has problems of poor aging and high cost when obtaining rock Young's modulus and Poisson's ratio during oil drilling and drilling.
Through the calculation of the fragment fractal dimension, a correlation model with Young's modulus and Poisson's ratio was established to achieve drilling-as-drilling acquisition of Young's modulus and Poisson's ratio.
It effectively improves the timeliness of obtaining data on rock Young's modulus and Poisson's ratio, reduces costs, and provides support for reservoir rock mechanical parameters evaluation and bottom-hole research.
Smart Images
Figure CN119437874A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of reservoir rock mechanics, and is a method for obtaining Young's modulus and Poisson's ratio while drilling based on rock fragment fractal dimension. Background Art
[0002] In the process of oil drilling and production, the Young's modulus and Poisson's ratio of rock are of great significance for optimizing drilling parameters and reservoir transformation. At present, indoor rock uniaxial compression experiments and logging data are generally used in China to obtain Young's modulus and Poisson's ratio. However, due to limitations such as timeliness and number of samples, it is difficult to meet the needs of on-site evaluation while drilling. Foreign countries have developed equipment RockSCAN and MaipSCAN for obtaining Young's modulus and Poisson's ratio of rock while drilling. Although the equipment can meet the needs of evaluation while drilling, the equipment cost is high and it is difficult to promote and apply. Summary of the invention
[0003] The present invention provides a method for obtaining Young's modulus and Poisson's ratio while drilling based on rock cuttings fractal dimension, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of poor timeliness and high cost in obtaining rock Young's modulus and Poisson's ratio data.
[0004] The technical solution of the present invention is achieved by the following measures: A method for obtaining Young's modulus and Poisson's ratio while drilling based on the fractal dimension of rock fragments, which is carried out according to the following steps:
[0005] S1, Young's modulus and Poisson's ratio of core samples are obtained through uniaxial compression test of rock;
[0006] S2, crushing the core sample to obtain crushed rock cuttings, and calculating the fractal dimension of the crushed rock cuttings;
[0007] S3, establish the correlation model between the fractal dimension of broken rock fragments and Young's modulus and Poisson's ratio;
[0008] S4, the Young's modulus and Poisson's ratio of the rock cuttings sample returned while drilling are obtained according to the established correlation model between the fractal dimension of the broken rock cuttings and Young's modulus and Poisson's ratio.
[0009] The following are further optimizations and / or improvements to the above technical solutions:
[0010] In the above step S1, the specific operation of the rock uniaxial compression test is as follows:
[0011] S11, experimental sample preparation, 3 to 5 samples of core samples of different lithology were taken, the total number of samples was 15 to 25 groups, the sample specifications were 25 mm in diameter and 50 mm in length, and the error was less than 1%;
[0012] S12, uniaxial compression test was carried out on the core sample;
[0013] S13, record the experimental data and Young's modulus and Poisson's ratio of the core sample.
[0014] In the above step S2, the specific operation of calculating the fractal dimension of the crushed rock cuttings is:
[0015] S21, use sieves with different apertures to screen the broken rock cuttings, and record the particle size of the broken rock cuttings as r i , i=1,2...k, k is the number of screen types with different apertures;
[0016] S22, weigh the crushed rock chips after screening, and take the particle size smaller than r i The mass of the crushed rock is denoted as M 下 (r i ), the corresponding broken rock debris remaining on the screen is recorded as M(r i ), the total number of particles of broken rock debris is recorded as N(r i ), the total mass is recorded as M;
[0017] S23, the fractal dimension of the broken rock fragments is calculated in the rectangular coordinate system with ln(r i ) is the horizontal axis, The Y value of the ordinate is taken as the linear regression, and the slope of the regression line n is obtained. The fractal dimension D of the cuttings is calculated. The expression of the fractal dimension of the cuttings is D = 3-n.
[0018] In the above step S21, the sieve is a square sieve with an aperture of 4 mesh, 8 mesh, 10 mesh, 20 mesh, 30 mesh, 40 mesh, 60 mesh, 80 mesh, 100 mesh or 120 mesh, and the sieve apertures used for screening are 5 to 11 types.
[0019] In the above step S3, the expression of the correlation model between the fractal dimension of rock fragments and Young's modulus and Poisson's ratio is:
[0020] YM=aD+b
[0021] UI=cD+d
[0022] Where, YM is Young's modulus, UI is Poisson's ratio, D is fractal dimension; a, b, c, d are coefficients respectively.
[0023] In the above step S4, the sampling of the rock cuttings samples returned while drilling meets the following requirements: the lithology of the sampling range of the vertical well section includes mudstone, siltstone, fine sandstone, gravel-containing fine sandstone and conglomerate, ensuring the diversity of lithology; the horizontal section sampling is the sampling of the entire horizontal section, and the sampling interval is 50m to 100m to ensure that the sample can reflect the lithology heterogeneity at different positions of the horizontal section; the sampling amount of the rock cuttings samples returned while drilling is 150g to 200g, and the samples are cleaned to a state without oil or mud and dried.
[0024] The present invention effectively solves the problems of poor timeliness and high cost in obtaining rock Young's modulus and Poisson's ratio data, and indirectly obtains rock Young's modulus and Poisson's ratio parameters through the fractal dimension of rock cuttings, providing support for reservoir rock mechanics parameter evaluation and bottom hole research. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Attached Figure 1 1 is the fractal characteristic curve of different crushed rock cuttings samples in Example 7 of the present invention.
[0026] Attached Figure 2 It is the correlation curve between Young's modulus and fractal dimension and the model verification diagram in Example 7 of the present invention.
[0027] Attached Figure 3 It is the correlation curve between Poisson's ratio and fractal dimension and the Poisson's ratio and model diagram in Example 7 of the present invention.
[0028] Attached Figure 4 The figure shows the calculation results and verification diagram of the fractal dimension, Young's modulus and Poisson's ratio of the returned rock cuttings in Example 7 of the present invention. DETAILED DESCRIPTION
[0029] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.
[0030] The present invention will be further described below in conjunction with embodiments:
[0031] Embodiment 1: The method for obtaining Young's modulus and Poisson's ratio while drilling based on rock fragment fractal dimension is carried out according to the following steps:
[0032] S1, Young's modulus and Poisson's ratio of core samples are obtained through uniaxial compression test of rock;
[0033] S2, crushing the core sample to obtain crushed rock cuttings, and calculating the fractal dimension of the crushed rock cuttings;
[0034] S3, establish the correlation model between the fractal dimension of broken rock fragments and Young's modulus and Poisson's ratio;
[0035] S4, the Young's modulus and Poisson's ratio of the rock cuttings sample returned while drilling are obtained according to the established correlation model between the fractal dimension of the broken rock cuttings and Young's modulus and Poisson's ratio.
[0036] Embodiment 2: As an optimization of the above embodiment, in step S1, the specific operation of the rock uniaxial compression test is as follows:
[0037] S11, experimental sample preparation, 3 to 5 samples of core samples of different lithologies are taken, and the total number of samples is 15 to 25 groups (the sample specifications are 25 mm in diameter and 50 mm in length, and the error is less than 1%);
[0038] S12, uniaxial compression test was carried out on the core sample;
[0039] S13, record the experimental data and Young's modulus and Poisson's ratio of the core sample.
[0040] The core lithology includes mudstone, silty mudstone, fine sandstone, gravelly fine sandstone and conglomerate. In order to ensure the accuracy of the experimental data, the core samples in the present invention should try to cover all lithology types. The uniaxial compression test can be tested according to the experimental specification DZ / T 0276.19-2015. When recording the experimental data, it should be noted that the samples after the experimental crushing should be numbered separately.
[0041] Embodiment 3: As an optimization of the above embodiment, in step S2, the specific operation of calculating the fractal dimension of the crushed rock cuttings is:
[0042] S21, use sieves with different apertures to screen the broken rock cuttings, and record the particle size of the broken rock cuttings as r i , i=1,2......k;
[0043] S22, weigh the crushed rock chips after screening, and take the particle size smaller than r i The mass of the crushed rock is denoted as M 下 (r i ), the corresponding broken rock debris remaining on the screen is recorded as M(r i ), the total number of particles of broken rock debris is recorded as N(r i ), the total mass is recorded as M; the recommended weighing balance range is 0g to 250g, and the accuracy is 0.001g;
[0044] S23, calculation of the fractal dimension of the broken rock fragments, in the rectangular coordinate system, ln(r i ) is the horizontal axis, The Y value of the ordinate is taken as the linear regression, and the slope of the regression line n is obtained. The fractal dimension D of the cuttings is calculated. The expression of the fractal dimension of the cuttings is D = 3-n.
[0045] Since the particle size distribution of the crushed rock cuttings samples follows the mass-frequency distribution and tends to be fine-grained, the Gaudin-Schuhmann distribution function is used for analysis, and the formula is: where r max is the maximum particle size of the cuttings, and the derivative of this formula is dM∝r n-1 dr, from the fractal concept, N (r) ∝r -D , considering the relationship between the mass, size and quantity of the crushed body as dM∝r 3 dN, we know r n-1 dr∝r 3 *r -D-1dr, we can get the expression of fractal dimension D as D=3-n.
[0046] In the present invention, the crushing process of the core sample can be carried out by a jaw crusher, and the equipment parameters of the jaw crusher are a rotor speed of 500r / min, a feed particle size of 1mm to 30mm, a discharge particle size of 0.1mm to 8mm, an adjustable discharge port size, an adjustment range of 2mm to 8mm, and an equipment working voltage of 220V. First, the samples crushed by the uniaxial compression test of the rock are artificially crushed to ensure that the maximum particle size is less than 30mm. After that, the jaw crusher is used for crushing one by one, and the discharge port size is adjusted to 8mm. After the crushing is completed, the crushed rock cuttings are numbered and recorded. When calculating the fractal dimension, the optimization principle of the screening mesh number is: the crushed rock cuttings sample is screened with 4 to 120 meshes, and the "head and tail removal" process is carried out, and at the same time, it is ensured that the mass of the screened rock cuttings is greater than 95% of the total mass of the crushed sample. If this condition is not met, a jaw crusher is further used, and the discharge port size is adjusted to 6mm, and secondary crushing is performed and then screened.
[0047] Embodiment 4: As an optimization of the above embodiment, in step S21, the sieve is a square sieve with an aperture of 4 mesh, 8 mesh, 10 mesh, 20 mesh, 30 mesh, 40 mesh, 60 mesh, 80 mesh, 100 mesh or 120 mesh, and the sieve apertures used for screening are 5 to 11. Using more than 5 apertures ensures that sufficient data is obtained for regression analysis.
[0048] Embodiment 5: As an optimization of the above embodiment, in step S3, the expression of the correlation model between the fractal dimension of rock fragments and Young's modulus and Poisson's ratio is:
[0049] YM=aD+b
[0050] UI=cD+d
[0051] Where, YM is Young's modulus, UI is Poisson's ratio, D is fractal dimension; a, b, c, d are coefficients respectively.
[0052] Example 6: As an optimization of the above example, in step S4, the sampling of the rock cuttings samples returned while drilling meets the following requirements: the lithology of the sampling range of the vertical well section includes multiple types of mudstone, siltstone, fine sandstone, gravel-containing fine sandstone and conglomerate to ensure lithology diversity (the lithology of the samples should include mudstone, siltstone, fine sandstone, gravel-containing fine sandstone and conglomerate as much as possible during sampling); the horizontal section sampling is the sampling of the entire horizontal section, and the sampling interval is 50m to 100m to ensure that the sample can reflect the lithology heterogeneity at different positions of the horizontal section; the sampling amount of the rock cuttings samples returned while drilling is 150g to 200g, and the samples are cleaned to a state without oil or mud and dried.
[0053] The present invention uses the fractal dimension of returned rock cuttings to obtain the Young's modulus and Poisson's ratio of rock. The Young's modulus and Poisson's ratio are measured by the rock core rock mechanics indoor experiment, the core sample is crushed and screened, the fractal dimension of the crushed rock cuttings is calculated, and a correlation model of the rock cuttings fractal dimension to obtain the Young's modulus and Poisson's ratio is established. Finally, the returned rock cuttings are dried, screened, and other treatments are performed to calculate the fractal dimension of the returned rock cuttings. The correlation model of the rock Young's modulus and Poisson's ratio can be obtained by using the rock cuttings fractal dimension to obtain the rock Young's modulus and Poisson's ratio data while drilling. This method can use the returned rock cuttings to obtain the rock Young's modulus and Poisson's ratio while drilling, which greatly improves the timeliness and convenience of data acquisition, and there is no need to carry out rock mechanics experiments in the entire well section, effectively reducing the cost of obtaining the rock Young's modulus and Poisson's ratio while drilling, making it more convenient for on-site promotion and application, and has good application prospects.
[0054] Example 7: The application of the method for obtaining Young's modulus and Poisson's ratio while drilling based on the fractal dimension of returned rock cuttings in 6 wells (MaH1 well, MaH 2 well, MaH 3 well, MaH4 well, MaH 5 well, MaH 6 well) in the Mahu X well block includes the following steps:
[0055] The first step is the uniaxial compression test in the core chamber.
[0056] A total of 16 core samples were collected from 6 wells in the Mahu X well block, including 4 samples each from Well MH1, Well MH2 and Well MH5, 2 samples from Well MH3, and 1 sample each from Well MH4 and Well MH6. The sample parameters and test data are shown in Table 1.
[0057] The second step is to calculate the fractal dimension of the broken rock fragments.
[0058] The 16 groups of core samples were crushed and processed respectively, and then each group of samples was screened with 4-mesh to 100-mesh sieves to obtain the cumulative mass of crushed rock chips with different particle sizes. The corresponding fractal curves were drawn based on the particle size distribution relationship of the crushed rock chip samples. Figure 1 (Part of the samples), the fractal dimension D was calculated by linear regression analysis. The calculation results of the fractal dimension of the broken cuttings of each well are shown in Table 2.
[0059] The third step is to establish a correlation model between the fractal dimension of broken rock fragments and Young's modulus and Poisson's ratio.
[0060] Eleven broken rock cuttings samples were randomly selected to establish a correlation model between the Young's modulus data measured by uniaxial compression test and the fractal dimension of broken rock cuttings.
[0061] The correlation model between rock fragment fractal dimension and Young's modulus is: YM = 26.651 × D-25.45, and the correlation coefficient R 2 =0.96(see Figure 2 ).
[0062] Correlation model between rock fragment fractal dimension and Poisson's ratio: UI = -0.1112 × D + 0.4924, correlation coefficient R 2 =0.93(see Figure 3 ).
[0063] The remaining five samples were used to verify the above model. The calculated results of the model were compared with the measured results, showing that the average error of Young's modulus was 4.36%, and the average error of Poisson's ratio was 5.87%.
[0064] The fourth step is to obtain two mechanical parameters of the returned rock cuttings using the correlation model between the fractal dimension of the crushed rock cuttings and Young's modulus and Poisson's ratio.
[0065] ① Calculation of fractal dimension of returned cuttings samples: A total of 9 returned cuttings were collected from two wells, MH101 and MaH102, in the Mahu X well block. The sampling interval was 2400.00 to 3250.00 m. The lithology mainly included mudstone, silty mudstone, argillaceous siltstone, silty-fine sandstone, etc. Each group of samples was cleaned and dried, with a mass of 150 g. They were sieved with 4 to 100 mesh sieves to ensure that the cumulative mass of the sieved cuttings accounted for more than 90% of the total mass. The coarse and fine grains were “cut off” to obtain the mass of cuttings with different particle sizes. The results are shown in Table 3.
[0066] ② Calculate the fractal dimension of the returned cuttings: Use the particle size distribution relationship of the cuttings sample to draw the corresponding fractal curve (consistent with the method of establishing the crushed cuttings), and calculate the fractal dimension D through linear regression analysis. The calculation results of the fractal dimension of the returned cuttings at different depths of Well MH101 and Well MH102 are shown in Table 4.
[0067] ③ Comparative analysis of Young's modulus and Poisson's ratio of returned cuttings with the calculation results of electrical measurement data: The fractal dimension of each sample was calculated by analyzing 9 groups of cuttings samples returned while drilling. Then, the Young's modulus and Poisson's ratio parameter values were calculated using the established correlation model between the fractal dimension of cuttings and Young's modulus and Poisson's ratio. The Young's modulus and Poisson's ratio calculated by electrical measurement data were compared with the results of model calculation. The results are shown in Figure 4 ,Depend on Figure 4 It can be concluded that the average error of the Young's modulus calculated by the model compared with the electrical measurement data is 6.44%, and the average error of Poisson's ratio is 5.94%.
[0068] This method is actually applied in the Mahu X well area of Xinjiang Oilfield. The correlation model between broken rock cuttings and Young's modulus and Poisson's ratio is used. The model correlation R 2The results of the present invention verify the reliability of the results of calculating the Young's modulus and Poisson's ratio of rock cuttings based on the fractal dimension of rock cuttings. The Young's modulus and Poisson's ratio of rock cuttings obtained by the method of the present invention are highly consistent with the results of electrical measurement calculation. The average error of the model calculation compared with the experimental test results is 4.36% and 5.87%. The method of the present invention can improve the timeliness of obtaining the Young's modulus and Poisson's ratio data of a single sample by more than 60%, and reduce the cost of a single sample by more than 50%.
[0069] In summary, the method for obtaining Young's modulus and Poisson's ratio while drilling based on the fractal dimension of returned rock cuttings of the present invention indirectly obtains the rock Young's modulus and Poisson's ratio parameters through the fractal dimension of rock cuttings, effectively improves the timeliness of obtaining rock Young's modulus and Poisson's ratio data, reduces production costs, and provides support for reservoir rock mechanics parameter evaluation and bottom hole research.
[0070] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.
[0071] Table 1
[0072]
[0073] Table 2
[0074]
[0075] Table 3
[0076]
[0077] Table 4
[0078] Sample No. 1 2 3 4 5 6 7 8 9 Fractal dimension D 2.220 2.239 2.263 2.344 2.371 2.391 2.406 2.302 2.388 <![CDATA[Correlation coefficient R 2 > 0.95 0.96 0.92 0.95 0.93 0.90 0.92 0.94 0.92
Claims
1. A method for obtaining Young's modulus and Poisson's ratio while drilling based on cuttings fractal dimension, characterized in that Follow these steps: S1, Young's modulus and Poisson's ratio of core samples are obtained through uniaxial compression test of rocks; S2, crushing the core sample to obtain crushed rock cuttings, and calculating the fractal dimension of the crushed rock cuttings; S3, establish the correlation model between the fractal dimension of broken rock fragments and Young's modulus and Poisson's ratio; S4, the Young's modulus and Poisson's ratio of the rock cuttings sample returned while drilling are obtained according to the established correlation model between the fractal dimension of the broken rock cuttings and Young's modulus and Poisson's ratio.
2. The method for obtaining Young's modulus and Poisson's ratio while drilling based on cuttings fractal dimension according to claim 1, characterized in that In step S1, the specific operation of the rock uniaxial compression test is as follows: S11, experimental sample preparation, 3 to 5 core samples of different lithology were taken, and the total number of samples was 15 to 25 groups; S12, uniaxial compression test was carried out on the core sample; S13, record the experimental data and Young's modulus and Poisson's ratio of the core sample.
3. The method for obtaining Young's modulus and Poisson's ratio while drilling based on cuttings fractal dimension according to claim 1 or 2, characterized in that In step S2, the specific operation of calculating the fractal dimension of the crushed rock cuttings is: S21, use sieves with different apertures to screen the broken rock cuttings, and record the particle size of the broken rock cuttings as r i , i=1,2......k, k is the number of screen types with different apertures; S22, weigh the crushed rock chips after screening, and take the particle size smaller than r i The mass of the crushed rock is denoted as M 下 (r i ), the corresponding broken rock debris remaining on the screen is recorded as M(r i ), the total number of particles of broken rock debris is recorded as N(r i ), the total mass is recorded as M; S23, calculation of the fractal dimension of the broken rock fragments, in the rectangular coordinate system, ln(r i ) is the horizontal axis, The Y value of the ordinate is taken as the linear regression, and the slope of the regression line n is obtained. The fractal dimension D of the cuttings is calculated. The expression of the fractal dimension of the cuttings is D = 3-n.
4. The method for obtaining Young's modulus and Poisson's ratio while drilling based on cuttings fractal dimension according to claim 3, characterized in that In step S21, the sieve is a square sieve with an aperture of 4 mesh, 8 mesh, 10 mesh, 20 mesh, 30 mesh, 40 mesh, 60 mesh, 80 mesh, 100 mesh or 120 mesh, and the sieve apertures used for screening are 5 to 11 types.
5. The method for obtaining Young's modulus and Poisson's ratio while drilling based on rock fragment fractal dimension according to any one of claims 1 to 4, characterized in that In step S3, the expression of the correlation model between the fractal dimension of rock fragments and Young's modulus and Poisson's ratio is: YM=aD+b UI=cD+d Where, YM is Young's modulus, UI is Poisson's ratio, D is fractal dimension; a, b, c, d are coefficients respectively.
6. The method for obtaining Young's modulus and Poisson's ratio while drilling based on rock fragment fractal dimension according to any one of claims 1 to 5, characterized in that In step S4, the sampling of the rock cuttings samples returned while drilling meets the following requirements: the lithology of the vertical well section sampling range includes mudstone, siltstone, fine sandstone, gravel-containing fine sandstone and conglomerate, ensuring lithology diversity; the horizontal section sampling is the entire horizontal section sampling, and the sampling interval is 50m to 100m to ensure that the sample can reflect the lithology heterogeneity at different positions of the horizontal section; the sampling amount of the rock cuttings samples returned while drilling is 150g to 200g, and the samples are cleaned to a state without oil or mud and dried.