Formation borehole wall stability evaluation method and device based on mineral logging technology

Abstract

The present application relates to the technical field of oil reservoir engineering, and is a formation borehole wall stability evaluation method and device based on mineral logging technology, which comprises the following steps: obtaining the volume content of water-sensitive minerals in a mudstone sample of a formation to be evaluated; determining the water absorption rate of each water-sensitive mineral; calculating the plastic water-sensitive strength of the mudstone mineral based on the volume content and water absorption rate of the water-sensitive mineral; and evaluating the formation borehole wall stability based on the plastic water-sensitive strength of the mudstone mineral. The present application is based on the water sensitivity mechanism of minerals, combines X-ray diffraction mineral logging technology with well diameter curves, establishes a wellbore instability grade standard for water-sensitive formations, and is verified by well diameter logging, which is highly reliable, has the characteristics of timely and efficient data acquisition while drilling, and is highly applicable in the field. The present application is not only suitable for mud shale, but also can be extended to other water-sensitive tight sand-shale formations, and has a wide application range.

Description

Technical Field

[0001] This invention relates to the field of reservoir engineering technology, and is a method and apparatus for evaluating formation wellbore stability based on mineral logging technology. Background Technology

[0002] Wellbore stability in water-sensitive formations is a complex and important research area, particularly significant in oil and gas drilling and engineering. Water-sensitive formations typically refer to those formations that are prone to expansion, disintegration, or instability upon contact with water or drilling fluid, such as shale and sandstone. Wellbore stability issues in these formations are primarily caused by a combination of physicochemical and mechanical factors.

[0003] As drilling speeds up and drilling depths continue to increase, the stability of conventional engineering parameters becomes increasingly difficult to predict, especially under complex geological conditions where multiple factors influence wellbore stability. This results in a lack of effective wellbore stability assessment methods in water-sensitive formations.

[0004] Chinese patent document CN119221874A discloses a method and system for maintaining wellbore stability in shale oil under hydration. The method includes: determining the mineral composition, pore distribution, and permeability anisotropy of shale in a shale oil experimental block to obtain relevant shale parameters; conducting mechanical experiments on shale samples based on these parameters to test the mechanical properties of dry shale cores under different confining pressures and clarify the upper and lower limit angles of shale bedding plane failure; correcting the strength data of shale samples under different drilling fluid systems to improve the shale strength criteria; determining the drilling fluid safety density window for the target formation based on measured data from the shale in the shale oil experimental block; and controlling wellbore stability under engineering conditions based on the drilling fluid safety density window. This patent primarily targets shale formations, limiting its applicability; furthermore, the description of the collaborative mechanism of each functional module is vague, and there are no effective verification methods.

[0005] Chinese patent document CN116539655A discloses a method for predicting shale oil wellbore collapse pressure, including the preparation of tight sandstone cores; testing the T2 spectrum of the core under saturated water state using nuclear magnetic resonance (NMR); water sensitivity experiments and calculation of the water sensitivity index; establishing a graph showing the relationship between the geometric mean of NMR T2 and the water sensitivity index; testing the T2 spectrum of the core after water sensitivity using NMR; analysis of the water sensitivity damage mechanism; and analysis of water sensitivity in different production layers of the target block. However, this method relies on high-precision experiments such as XRD, NMR, and triaxial stress measurement, resulting in high on-site implementation costs and long core sampling and experimental cycles, making it difficult to meet the needs of real-time drilling decision-making. Furthermore, the iterative trial algorithm requires multiple simulations of force-chemical-thermal-stratification coupling effects, resulting in a large computational load and high requirements for hardware and algorithms, making it difficult to embed into a real-time drilling control system.

[0006] In summary, existing methods for calculating formation water sensitivity suffer from high testing costs and limited applicability, necessitating the development of a convenient and accurate method for evaluating formation water sensitivity. Summary of the Invention

[0007] This invention provides a formation wellbore stability evaluation method based on mineral logging technology, which overcomes the shortcomings of the prior art. It can effectively solve the problems of the lack of quantitative evaluation methods for the wellbore stability of water-sensitive formations and the inaccuracy of the methods for determining instability levels in the existing technologies.

[0008] One of the technical solutions of this invention is achieved through the following measures: a method for evaluating formation wellbore stability based on mineral logging technology, comprising the following steps:

[0009] Obtain the volumetric content of water-sensitive minerals in the mudstone sample of the formation to be evaluated;

[0010] Determine the water absorption rate of each water-sensitive mineral;

[0011] The plastic water-sensitive strength of mudstone minerals is calculated based on the volume content and water absorption rate of water-sensitive minerals.

[0012] Evaluation of formation wellbore stability based on the plastic water-sensitive strength of mudstone minerals;

[0013] The water-sensitive minerals include montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite;

[0014] The plastic water-sensitive strength of the mudstone minerals is calculated using the following formula:

[0015]

[0016] In the formula, The plastic water-sensitive strength of mudstone minerals is dimensionless. The values ​​represent the volume contents (%) of montmorillonite, illite, illite-montmorillonite mixed-layer, and kaolinite in the mudstone samples. The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; The weighting coefficients are montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite, respectively.

[0017] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0018] The water absorption rate of each water-sensitive mineral was obtained according to the following steps:

[0019] Weigh 100g of each water-sensitive mineral standard and place them in 1000cm³ of water. Vacuum saturate at -0.10MPa for 24 hours. After filtration, measure the volume of the filtrate and calculate the water absorption rate using the following formula:

[0020]

[0021] In the formula, The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; The volumes (cm³) of the filtrate after water absorption by the standard minerals montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite. ρ is the density of water, in g / cm³.

[0022] The weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite mentioned above were determined according to the following steps:

[0023] Calculate the comprehensive identification index of the strata where the mudstone sample is located;

[0024] Based on the comprehensive judgment index, the strata are divided into brittle strata and highly water-sensitive strata;

[0025] The weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite are determined based on brittle strata and highly water-sensitive strata.

[0026] The above comprehensive judgment index is calculated using the following formula:

[0027]

[0028] In the formula, The index is dimensionless and is used for comprehensive judgment. The brittleness index is dimensionless. The water sensitivity index is dimensionless.

[0029] The above-mentioned brittleness index is calculated using the following formula:

[0030]

[0031] In the formula, The brittleness index is dimensionless. The quartz mineral content in the mudstone sample, % The content of feldspar minerals in the mudstone sample, % The calcite mineral content in the mudstone sample is %; The dolomite mineral content in the mudstone sample, % The content of montmorillonite minerals in the mudstone sample, % The illite mineral content in the mudstone sample is %; The content of illite-montmorillonite mixed-layer minerals in the mudstone sample, % The percentage represents the kaolinite mineral content in the mudstone sample.

[0032] The above water sensitivity index is calculated using the following formula:

[0033]

[0034] In the formula, The water sensitivity index is dimensionless. The quartz mineral content in the mudstone sample, % The content of feldspar minerals in the mudstone sample, % The calcite mineral content in the mudstone sample is %; The dolomite mineral content in the mudstone sample is represented by (%).

[0035] The above-mentioned strata are classified into brittle strata and highly water-sensitive strata based on the comprehensive judgment index, including:

[0036] when When the value is greater than or equal to 90, the rock strata are judged to be brittle strata;

[0037] when When the value is less than 90, the rock strata are judged to be highly water-sensitive strata.

[0038] When the aforementioned rock strata are brittle strata, the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed strata, and kaolinite are 40%, 25%, 25%, and 10%, respectively.

[0039] When the aforementioned rock strata are highly water-sensitive strata, the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed strata, and kaolinite are 45%, 20%, 30%, and 5%, respectively.

[0040] The above-mentioned evaluation of formation wellbore stability based on the plasticity and water sensitivity of mudstone minerals includes:

[0041] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 30, the formation wellbore stability instability level is Class I, and there is a risk of wellbore collapse.

[0042] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 25 and less than 30, the formation wellbore stability instability level is Class II, and there is a risk of shrinkage and rockfall.

[0043] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 20 and less than 25, the formation wellbore stability instability level is III, and there is a slight risk of diameter reduction.

[0044] When the plasticity water sensitivity of mudstone minerals is less than 20, the formation wellbore stability instability level is IV, which is risk-free.

[0045] The second technical solution of the present invention is achieved through the following measures: a formation wellbore stability evaluation device based on mineral logging technology, comprising:

[0046] The data acquisition module obtains the volumetric content of water-sensitive minerals in the mudstone sample of the formation to be evaluated;

[0047] The water absorption rate calculation module determines the water absorption rate of each water-sensitive mineral.

[0048] The water-sensitive strength calculation module calculates the plastic water-sensitive strength of mudstone minerals based on the volume content and water absorption rate of water-sensitive minerals.

[0049] The evaluation module assesses formation wellbore stability based on the plasticity and water sensitivity of mudstone minerals.

[0050] The water-sensitive minerals include montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite;

[0051] The plastic water-sensitive strength of the mudstone minerals is calculated using the following formula:

[0052]

[0053] In the formula, The plastic water-sensitive strength of mudstone minerals is dimensionless. The values ​​represent the volume contents (%) of montmorillonite, illite, illite-montmorillonite mixed-layer, and kaolinite in the mudstone samples. The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; These are the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite, respectively.

[0054] This invention provides a formation wellbore stability evaluation method based on mineral logging technology. Based on the mineral water sensitivity mechanism, it combines X-ray diffraction mineral logging technology with well logging caliper curves to establish a wellbore instability level standard for water-sensitive formations, which is verified by well logging caliper. It has high reliability, timely and efficient data acquisition while drilling, and strong field applicability. It is not only applicable to mudstone and shale, but can also be extended to other water-sensitive tight sandstone and mudstone formations, with a wide range of applications. Attached Figure Description

[0055] Appendix Figure 1 This is a schematic diagram of the formation wellbore stability evaluation device based on mineral logging technology of the present invention.

[0056] Appendix Figure 2 This is a graph showing the intersection of water-sensitive minerals and well logging diameter curve data in Example 13 of the present invention.

[0057] Appendix Figure 3 This is a cross-plot of the plasticity water sensitivity of mudstone minerals and the logging diameter in Example 13 of the present invention. Detailed Implementation

[0058] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0059] The present invention will be further described below with reference to embodiments:

[0060] Example 1: The formation wellbore stability evaluation method based on mineral logging technology includes the following steps:

[0061] Obtain the volumetric content of water-sensitive minerals in the mudstone sample of the formation to be evaluated;

[0062] Determine the water absorption rate of each water-sensitive mineral;

[0063] The plastic water-sensitive strength of mudstone minerals is calculated based on the volume content and water absorption rate of water-sensitive minerals.

[0064] Evaluation of formation wellbore stability based on the plastic water-sensitive strength of mudstone minerals;

[0065] The water-sensitive minerals include montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite;

[0066] The plastic water-sensitive strength of the mudstone minerals is calculated using the following formula:

[0067]

[0068] In the formula, The plastic water-sensitive strength of mudstone minerals is dimensionless. The values ​​represent the volume contents (%) of montmorillonite, illite, illite-montmorillonite mixed-layer, and kaolinite in the mudstone samples. The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; These are the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite, respectively.

[0069] Example 2: As an optimization of the above example, the water absorption rate of each water-sensitive mineral is obtained according to the following steps:

[0070] Weigh 100g of each water-sensitive mineral standard and place them in 1000cm³ of water. Vacuum saturate at -0.10MPa for 24 hours. After filtration, measure the volume of the filtrate and calculate the water absorption rate using the following formula:

[0071]

[0072] In the formula, The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; The volumes (cm³) of the filtrate after water absorption by the standard minerals montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite. ρ is the density of water, in g / cm³.

[0073] Example 3: As an optimization of the above examples, the weighting coefficients of montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite are determined according to the following steps:

[0074] Calculate the comprehensive identification index of the strata where the mudstone sample is located;

[0075] Based on the comprehensive judgment index, the strata are divided into brittle strata and highly water-sensitive strata;

[0076] The weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite are determined based on brittle strata and highly water-sensitive strata.

[0077] Example 4: As an optimization of the above examples, the comprehensive judgment index is calculated using the following formula:

[0078]

[0079] In the formula, The index is dimensionless and is used for comprehensive judgment. The brittleness index is dimensionless. The water sensitivity index is dimensionless.

[0080] Example 5: As an optimization of the above examples, the brittleness index is calculated using the following formula:

[0081]

[0082] In the formula, The brittleness index is dimensionless. The quartz mineral content in the mudstone sample, % The content of feldspar minerals in the mudstone sample, % The calcite mineral content in the mudstone sample is %; The dolomite mineral content in the mudstone sample, % The content of montmorillonite minerals in the mudstone sample, % The illite mineral content in the mudstone sample is %; The content of illite-montmorillonite mixed-layer minerals in the mudstone sample, % The percentage represents the kaolinite mineral content in the mudstone sample.

[0083] Example 6: As an optimization of the above examples, the water sensitivity index is calculated using the following formula:

[0084]

[0085] In the formula, The water sensitivity index is dimensionless. The quartz mineral content in the mudstone sample, % The content of feldspar minerals in the mudstone sample, % The calcite mineral content in the mudstone sample is %; The dolomite mineral content in the mudstone sample is represented by (%).

[0086] Example 7: As an optimization of the above examples, the strata are divided into brittle strata and highly water-sensitive strata according to the comprehensive judgment index, including:

[0087] when When the value is greater than or equal to 90, the rock strata are judged to be brittle strata;

[0088] when When the value is less than 90, the rock strata are judged to be highly water-sensitive strata.

[0089] Example 8: As an optimization of the above example, when the rock strata are brittle strata, the weighting coefficients of montmorillonite, illite, illite-montmorillonite mixed strata, and kaolinite are 40%, 25%, 25%, and 10%, respectively.

[0090] Example 9: As an optimization of the above example, when the rock strata are highly water-sensitive strata, the weighting coefficients of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are 45%, 20%, 30%, and 5%, respectively.

[0091] Example 10: As an optimization of the above examples, evaluating formation wellbore stability based on the plasticity and water sensitivity of mudstone minerals includes:

[0092] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 30, the formation wellbore stability instability level is Class I, and there is a risk of wellbore collapse.

[0093] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 25 and less than 30, the formation wellbore stability instability level is Class II, and there is a risk of shrinkage and rockfall.

[0094] When the plastic water-sensitive strength of mudstone minerals is greater than or equal to 20 and less than 25, the formation wellbore stability instability level is III, and there is a slight risk of diameter reduction.

[0095] When the plasticity water sensitivity of mudstone minerals is less than 20, the formation wellbore stability instability level is IV, which is risk-free.

[0096] Example 11: The formation wellbore stability evaluation device based on mineral logging technology includes:

[0097] The data acquisition module obtains the volumetric content of water-sensitive minerals in the mudstone sample of the formation to be evaluated;

[0098] The water absorption rate calculation module determines the water absorption rate of each water-sensitive mineral.

[0099] The water-sensitive strength calculation module calculates the plastic water-sensitive strength of mudstone minerals based on the volume content and water absorption rate of water-sensitive minerals.

[0100] The evaluation module assesses formation wellbore stability based on the plasticity and water sensitivity of mudstone minerals.

[0101] The water-sensitive minerals include montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite;

[0102] The plastic water-sensitive strength of the mudstone minerals is calculated using the following formula:

[0103]

[0104] In the formula, The plastic water-sensitive strength of mudstone minerals is dimensionless. The values ​​represent the volume contents (%) of montmorillonite, illite, illite-montmorillonite mixed-layer, and kaolinite in the mudstone samples. The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; These are the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite, respectively.

[0105] Example 12: The establishment and implementation process of this formation wellbore stability evaluation method based on mineral logging technology is as follows:

[0106] Step 1: Obtain X-ray diffraction whole-rock mineral data:

[0107] Given that the water-sensitive strata are mainly composed of plastic mudstone, the XRD analysis should be performed according to the following steps: First, screen the mudstone samples, removing non-representative parts such as pseudo-rock fragments and flaking pieces; then grind the samples into powder using a mortar and pestle, and pass them through a 200-mesh (0.074 mm) sieve, taking the sieved powder and placing it in the instrument; during analysis, the sample amount should be controlled at about 0.1 g, occupying about 2 / 3 of the analysis cell, and the number of exposures should be set to 64; to improve accuracy, the above process should be repeated 3 times; finally, decode the spectrum and read the data using XRD analysis software, and take the average of the 3 results as the final analysis data for that sample point to obtain X-ray diffraction whole-rock mineral data.

[0108] Step 2, identify water-sensitive minerals:

[0109] Currently, the primary standard for evaluating the wellbore stability of water-sensitive formations is the well logging caliper curve. Therefore, this invention uses well logging caliper data to select X-ray diffraction minerals based on their correlation with the wellbore. From whole-rock X-ray diffraction mineral data, the contents of 10 minerals—quartz, plagioclase, calcite, montmorillonite, illite-montmorillonite mixed layer, illite, kaolinite, anhydrite, dolomite, and analcime—can be obtained from mudstone samples. By applying well logging caliper data and whole-rock X-ray diffraction mineral data, and through data processing, mineral combinations with high correlation to well logging caliper data are identified as water-sensitive minerals. In this invention, through data analysis, the water-sensitive minerals are determined to be montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite, which are used for wellbore stability evaluation.

[0110] Step 3: Determine the water absorption rate of water-sensitive minerals:

[0111] Weigh 100g of each water-sensitive mineral standard and place them in a 1000cm³ aqueous solution. Vacuum saturate the solution at -0.10MPa for 24 hours. After filtration, measure the volume of the filtrate and calculate the water absorption rate using the following formula.

[0112]

[0113] In the formula, The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; The volumes (cm³) of the filtrate after water absorption by the standard minerals montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite. ρ is the density of water, in g / cm³.

[0114] In this embodiment, the water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite were tested and calculated, as shown in Table 1.

[0115] Table 1 .

[0116] Step 4: Construct a comprehensive judgment index based on the water sensitivity index and the brittleness index:

[0117] Brittle strata are characterized by being rich in rigid, chemically stable minerals such as quartz, feldspar, and carbonate rocks (calcite, dolomite). Highly water-sensitive strata are characterized by being rich in montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite clay minerals; these minerals exhibit swelling, dispersion, and migration properties, undergoing plastic deformation under stress and absorbing large amounts of water. Brittleness index (BCI) ) and water sensitivity index ( These two indices describe rocks from two different dimensions, but they are essentially negatively correlated. This invention combines the water sensitivity index and the brittleness index to construct a comprehensive judgment index for stratigraphic classification:

[0118]

[0119]

[0120]

[0121] In equations 6 to 8, The index is dimensionless and is used for comprehensive judgment. The brittleness index is dimensionless. The water sensitivity index is dimensionless. The quartz mineral content in the mudstone sample, % The content of feldspar minerals in the mudstone sample, % The calcite mineral content in the mudstone sample is %; The dolomite mineral content in the mudstone sample, % The content of montmorillonite minerals in the mudstone sample, % The illite mineral content in the mudstone sample is %; The content of illite-montmorillonite mixed-layer minerals in the mudstone sample, % The percentage represents the kaolinite mineral content in the mudstone sample.

[0122] in, It can measure the fragility potential of the underlying layers. It can measure the formation's "water resistance" ability. The higher the water sensitivity, the stronger the sensitivity. The lower the value, the worse the formation stability, while an ideal fracturing formation (with higher stability) is considered to be... The formation must simultaneously meet both the conditions of high brittleness and low water sensitivity. Based on this, the present invention classifies strata into brittle strata and highly water-sensitive strata according to a comprehensive judgment index, as shown in Table 2.

[0123] Table 2

[0124] .

[0125] Step 5: Determine the weights of water-sensitive minerals:

[0126] in accordance with The stratigraphic type is determined by summarizing the stratigraphic types and mineral content characteristics reflected in a large amount of experimental data and literature research. Montmorillonite: has the highest weight because its high expansibility and strong water sensitivity significantly reduce rock strength; Kaolinite: has no expansibility but is prone to brittle fracture and migration, affecting permeability and brittleness; Illite-montmorillonite mixed layer: its behavior depends on the mixed layer ratio, and when the montmorillonite layer has a high proportion, it behaves similarly to montmorillonite; Illite: has weak cementation, and may block pores after migration, but has little impact on strength (Mitchell & Soga, 2005; Zhang et al., 2019). Based on the above research, the weight coefficients of sensitive minerals for different stratigraphic types in this invention are determined, as shown in Table 3.

[0127] Table 3

[0128] .

[0129] Step 6, Calculation of the plasticity and water sensitivity of mudstone minerals:

[0130] The water absorption rate of minerals reflects the strength of water sensitivity, which is basically consistent with the theoretical water sensitivity. Therefore, by using the water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite, combined with the percentage content of minerals obtained from X-ray diffraction, and determining the weighting coefficients through stratigraphic type, the plastic water sensitivity of mudstone minerals can be calculated using the following formula:

[0131]

[0132] In the formula, The plastic water-sensitive strength of mudstone minerals is dimensionless. The values ​​represent the volume contents (%) of montmorillonite, illite, illite-montmorillonite mixed-layer, and kaolinite in the mudstone samples. The water absorption rates of montmorillonite, illite, illite-montmorillonite mixed layer, and kaolinite are respectively, dimensionless; These are the weighting coefficients for montmorillonite, illite, illite-montmorillonite mixed layers, and kaolinite, respectively.

[0133] Step 7, Water-sensitive formation wellbore instability level:

[0134] The wellbore instability rating of water-sensitive formations was established based on the well logging curve data of drilled wells and the water-sensitive plasticity of mudstone minerals, as shown in Table 4.

[0135] Table 4 .

[0136] In summary, this invention identifies water-sensitive minerals by screening characteristic minerals in water-sensitive formations within the evaluation area. Combined with experimental research on the water absorption parameters of these minerals, a calculation model for the plastic water-sensitive strength of mudstone minerals is established. Comparison with well logging diameter curve data shows a strong correlation between the two. Furthermore, a classification standard for wellbore instability levels in water-sensitive formations is established, enabling timely early warning. This invention effectively avoids risks and analyzes the causes of past incidents. Moreover, the X-ray diffraction whole-rock mineral logging technology is low-cost, reducing drilling costs and possessing significant practical value.

[0137] Example 13: The specific implementation of this formation wellbore stability evaluation method based on mineral logging technology in the Manas anticline area of ​​the Junggar Basin in Xinjiang Oilfield is as follows:

[0138] (1) Obtain X-ray diffraction whole-rock mineral and well logging caliper curve data:

[0139] Mudstone samples from 10 test points in the FT1 well of the Manas anticline were obtained and subjected to X-ray whole-rock mineral analysis. The analysis revealed the contents of 10 minerals in the mudstone samples: quartz, plagioclase, calcite, montmorillonite, illite-montmorillonite mixed layer, illite, kaolinite, anhydrite, dolomite, and analcime. Correlation analysis was established between the contents of these 10 minerals and the well logging caliper data (Table 5). Minerals with moderate to strong correlations between 0.6 and 1 were selected, including montmorillonite R... 2 =0.712, illite R 2 =0.7371, Emmermann mixed layer R 2 =0.6576, Kaolin R 2 =0.4935 ( Figure 2 ).

[0140] Table 5

[0141] .

[0142] (2) Calculation of plastic water-sensitive strength values ​​of mudstone minerals:

[0143] Calculate the water content of water-sensitive minerals, and calculate the water sensitivity index, brittleness index and comprehensive judgment index according to Equations 6 to 8 (Table 6). Determine the stratigraphic type based on the comprehensive judgment index, select the weight coefficient corresponding to the stratigraphic type, and calculate the plastic water sensitivity intensity of mudstone minerals at the test point (Table 7).

[0144] Table 6

[0145] .

[0146] Table 7

[0147] .

[0148] The plastic water sensitivity values ​​of mudstone minerals at 10 test points in the FT1 well of the Manas anticline in this area were calculated according to Equation 1. Correlation analysis was performed with the well logging diameter. A cross-plot was plotted with the calculated plastic water sensitivity values ​​of mudstone minerals as the ordinate and the well logging diameter as the abscissa, yielding y = 2.7033x - 27.133, and a correlation R. 2 =0.7785 (see) Figure 3 This demonstrates that the plastic water-sensitive strength of mudstone minerals in this invention can accurately reflect the wellbore stability of water-sensitive formations and can meet the needs of field analysis.

[0149] (3) Determination of wellbore instability level

[0150] Based on the water-sensitive plasticity values ​​of mudstone minerals at 10 test points in the FT1 well of the Manas anticline, the wellbore stability was classified (Table 7). Two items were classified as Class I wellbore instability risk, two as Class II, three as Class III, and the remaining four had no wellbore instability risk. Based on the evaluation results, timely adjustments to the drilling fluid were made during drilling of the easily collapsible section of the Anjihaihe Formation in well MN007, effectively suppressing water absorption and expansion of the wellbore and preventing complex accidents.

[0151] Example 14: The implementation of this formation wellbore stability evaluation method based on mineral logging technology in the Fengcheng Formation area of ​​the Mabei Block in the Junggar Basin of Xinjiang Oilfield is as follows:

[0152] (1) Mudstone samples were obtained from five water-sensitive formation sampling points of a shale oil well in the Mabei Block of the Junggar Basin in Xinjiang Oilfield. X-ray diffraction analysis was performed to obtain data on water-sensitive minerals. The results are shown in Table 8.

[0153] Table 8

[0154] .

[0155] (2) Calculate the water content of water-sensitive minerals, calculate the water sensitivity index and brittleness index to determine the comprehensive judgment index. If the comprehensive judgment index of each sampling point is less than 90, it is considered a brittle stratum (Table 9). The brittle stratum weight is used for calculation. The plastic water sensitivity intensity value of mudstone minerals at each sampling point is calculated according to Equation 1 (Table 10).

[0156] Table 9

[0157] .

[0158] Table 10

[0159] .

[0160] (3) Wellbore instability determination

[0161] Based on the wellbore instability level standard, the wellbore stability was determined (Table 10). During drilling, a drilling analysis was conducted on the Anfengcheng Formation cloudy mudstone section of well MY1003. The prediction conclusion was consistent with the drilling analysis results, indicating that the wellbore instability risk level was not reached and there was no risk of wellbore instability. Drilling can continue safely with normal parameters.

[0162] In summary, this invention provides a formation wellbore stability evaluation method based on mineral logging technology. By combining X-ray diffraction mineral logging technology with well logging caliper curves, a wellbore instability level standard for water-sensitive formations is established. This method can evaluate the water sensitivity of tight sandstone reservoirs while drilling without coring, provide timely warnings of wellbore instability risks, avoid risks from occurring, and greatly save measurement time and costs.

[0163] The above technical features constitute the preferred embodiment of the present invention, which has strong adaptability and optimal implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A method for evaluating formation borehole stability based on mineral logging technology, characterized in that The method comprises the following steps: obtaining the volume content of water-sensitive minerals in a mudstone sample of a formation to be evaluated; determining the water absorption rate of each water-sensitive mineral; calculating the plastic water sensitivity strength of the mudstone minerals according to the volume content and the water absorption rate of the water-sensitive minerals; evaluating the wellbore stability of the formation based on the plastic water sensitivity strength of the mudstone minerals; the water-sensitive minerals include montmorillonite, illite, illite-smectite mixed layer, and kaolinite; the plastic water sensitivity strength of the mudstone minerals is calculated according to the following formula: In the formula, KWSM is the plastic water sensitivity intensity of mudstone mineral, dimensionless; respectively, the volume content of montmorillonite, illite, illite-smectite mixed layer and kaolinite in the mudstone sample; respectively, the water absorption rate of montmorillonite, illite, illite-smectite mixed layer and kaolinite, dimensionless; respectively, the weight coefficient of montmorillonite, illite, illite-smectite mixed layer and kaolinite; the weight coefficients of the montmorillonite, illite, illite-smectite mixed layer, and kaolinite are determined according to the following steps: calculating a comprehensive determination index of the formation where the mudstone sample is located; dividing the formation into a brittle formation and a strong water-sensitive formation according to the comprehensive determination index; determining the weight coefficients of the montmorillonite, illite, illite-smectite mixed layer, and kaolinite according to the brittle formation and the strong water-sensitive formation; the comprehensive determination index is calculated according to the following formula: in the formula, BSI is the comprehensive determination index, which is dimensionless; BI is a brittleness index, which is dimensionless; SSI is a water sensitivity index, which is dimensionless; the brittleness index is calculated according to the following formula: where BI is the brittleness index, dimensionless; is the content of quartz mineral in the mudstone sample, %; is the content of feldspar mineral in the mudstone sample, %; is the content of calcite mineral in the mudstone sample, %; is the content of dolomite mineral in the mudstone sample, %; is the content of montmorillonite mineral in the mudstone sample, %; is the content of illite mineral in the mudstone sample, %; is the content of illite-smectite mixed layer mineral in the mudstone sample, %; is the content of kaolinite mineral in the mudstone sample, %. the water sensitivity index is calculated according to the following formula: where SSI is the water sensitivity index, dimensionless; is the content of quartz mineral in the mudstone sample, %; is the content of feldspar mineral in the mudstone sample, %; is the content of calcite mineral in the mudstone sample, %; is the content of dolomite mineral in the mudstone sample, %.

2. The method for evaluating the wellbore stability of a formation based on the mineral logging technology according to claim 1, characterized in that the water absorption rate of each water-sensitive mineral is obtained according to the following steps: 100 g of a standard mineral of each water-sensitive mineral is weighed and placed in 1000 cm³ of water, and vacuum saturated at -0.10 MPa for 24 hours; after filtration, the volume of the filtrate is measured, and the water absorption rate is calculated according to the following formula: wherein respectively the water absorption of montmorillonite, illite, illite-smectite mixed layer, kaolinite, dimensionless; respectively the volume of the filtrate after the standard mineral water absorption of montmorillonite, illite, illite-smectite mixed layer, kaolinite, cm3; is the density of water, g / cm3.

3. The method for evaluating the wellbore stability of a formation based on the mineral logging technology according to claim 1 or 2, characterized in that dividing the formation into a brittle formation and a strong water-sensitive formation according to the comprehensive determination index comprises: when the BSI value is greater than or equal to 90, the rock formation is determined to be a brittle formation; when the BSI value is less than 90, the rock formation is determined to be a strong water-sensitive formation.

4. The method according to claim 3, characterized in that when the rock formation is a brittle formation, the weight coefficients of the montmorillonite, illite, illite-smectite mixed layer, and kaolinite are 40%, 25%, 25%, and 10%, respectively.

5. The method according to claim 4, characterized in that when the rock formation is a strong water-sensitive formation, the weight coefficients of the montmorillonite, illite, illite-smectite mixed layer, and kaolinite are 45%, 20%, 30%, and 5%, respectively.

6. The method for formation borehole stability evaluation based on mineral logging technology according to claim 1, characterized in that evaluating the wellbore stability of the formation based on the plastic water sensitivity strength of the mudstone minerals comprises: when the plastic water sensitivity strength of the mudstone minerals is greater than or equal to 30, the wellbore stability of the formation is in a grade I instability level, and there is a risk of wellbore collapse; when the plastic water sensitivity strength of the mudstone minerals is greater than or equal to 25 and less than 30, the wellbore stability of the formation is in a grade II instability level, and there is a risk of diameter shrinkage and blockage; when the plastic water sensitivity strength of the mudstone minerals is greater than or equal to 20 and less than 25, the wellbore stability of the formation is in a grade III instability level, and there is a risk of slight diameter shrinkage; when the plastic water sensitivity strength of the mudstone minerals is less than 20, the wellbore stability of the formation is in a grade IV instability level, and there is no risk.

7. A device for evaluating the stability of a well wall in a formation based on a mineral logging technique, which uses the method for evaluating the stability of a well wall in a formation based on a mineral logging technique according to any one of claims 1 to 6, characterized by comprise: a data acquisition module that obtains the volume content of water-sensitive minerals in a mudstone sample of a formation to be evaluated; a water absorption rate calculation module that determines the water absorption rate of each water-sensitive mineral; a water sensitivity strength calculation module that calculates the plastic water sensitivity strength of the mudstone minerals according to the volume content and the water absorption rate of the water-sensitive minerals; an evaluation module that evaluates the wellbore stability of the formation based on the plastic water sensitivity strength of the mudstone minerals; the water-sensitive minerals include montmorillonite, illite, illite-smectite mixed layer, and kaolinite; the plastic water sensitivity strength of the mudstone minerals is calculated according to the following formula: In the formula, KWSM is the plastic water sensitivity intensity of mudstone mineral, dimensionless; respectively, the volume content of montmorillonite, illite, illite-smectite mixed layer and kaolinite in the mudstone sample; respectively, the water absorption rate of montmorillonite, illite, illite-smectite mixed layer and kaolinite, dimensionless; respectively, the weight coefficient of montmorillonite, illite, illite-smectite mixed layer and kaolinite; the weight coefficients of the montmorillonite, illite, illite-smectite mixed layer, and kaolinite are determined according to the following steps: calculating a comprehensive determination index of the formation where the mudstone sample is located; classifying the formation into a brittle formation and a strong water-sensitive formation according to the comprehensive determination index; determining weight coefficients of montmorillonite, illite, illite-smectite mixed layer and kaolinite according to the brittle formation and the strong water-sensitive formation; the comprehensive determination index is calculated according to the following formula: in the formula, BSI is the comprehensive determination index, dimensionless; BI is a brittle index, dimensionless; SSI is a water sensitivity index, dimensionless; the brittle index is calculated according to the following formula: wherein BI is a brittleness index, dimensionless; is the quartz mineral content in the mudstone sample, %; is the feldspar mineral content in the mudstone sample, %; is the calcite mineral content in the mudstone sample, %; is the dolomite mineral content in the mudstone sample, %; is the smectite mineral content in the mudstone sample, %; is the illite mineral content in the mudstone sample, %; is the illite-smectite mixed-layer mineral content in the mudstone sample, %; is the kaolinite mineral content in the mudstone sample, %. the water sensitivity index is calculated according to the following formula: where SSI is the water sensitivity index, dimensionless; is the content of quartz mineral in the mudstone sample, %; is the content of feldspar mineral in the mudstone sample, %; is the content of calcite mineral in the mudstone sample, %; is the content of dolomite mineral in the mudstone sample, %.

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