Wellbore comprehensive geologic model construction method based on continuous quantitative grading of surrounding rocks

Abstract

The invention discloses a shaft comprehensive geologic model construction method based on continuous quantitative grading of surrounding rocks. The problems that in shaft construction, surrounding rock strength grade evaluation representativeness is insufficient, permeability coefficient K dimensionless quantification is deficient, and high-permeability section systematic overestimation is caused are solved. The method comprises the following five core steps: 1, acquiring full-depth parameters of a drill hole, taking a rock core through drilling, and measuring lithology and permeability coefficients of surrounding rock; 2, calculating a lithology index Ai; 3, calculating a permeability coefficient by combining hydrological and lithologic parameters of the surrounding rock so as to obtain a hydrological index Bi; 4, coupling Ai and Bi to obtain a comprehensive index Ci; and 5, dividing the Ci into I-V levels, and generating a total depth statistical table containing the depth, the Ci and the levels. On-site application shows that the grade division of the surrounding rock is more accurate, and the time lt is divided in real time; the method is suitable for underground engineering such as a vertical shaft, an inclined shaft and a deep-buried tunnel needing grading of the surrounding rock of-200 m on the earth surface, and the popularization prospect and the economic value are wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of shaft construction engineering quality evaluation and underground engineering design technology, and particularly relates to a shaft comprehensive geological model construction method based on continuous quantitative classification of surrounding rock. BACKGROUND

[0002] With the deepening of underground engineering (>200m), hard-soft interbedding of lithology and spatial mutation of permeability coefficient spanning multiple orders of magnitude often occur in the same borehole. The existing engineering rock mass classification standards, Q system, RMR, GSI and other classification systems have the following defects:

[0003] (1) Only the working face is taken as the evaluation "point", and it is impossible to provide the "line" or "body" grade distribution from the surface to the full depth of the engineering;

[0004] (2) The influence of groundwater is adopted by using an empirical reduction coefficient, and the permeability coefficient K is not included in the lithology parameter with the same dimension, resulting in systematic overestimation of the deep high-permeability section;

[0005] (3) There is no real-time updating mechanism, and the grade cannot be dynamically corrected with the excavation.

[0006] The above defects cause disasters such as insufficient shaft wall thickness, tunnel gushing, TBM jamming, etc., and it is urgent to establish a comprehensive classification method driven by "lithology + hydrology" double indicators, vertically continuous and dynamically updated. SUMMARY

[0007] The purpose of the present application is to solve the above technical problems, and provide a shaft comprehensive geological model construction method based on continuous quantitative classification of surrounding rock.

[0008] The specific scheme of the present application is as follows:

[0009] First, the full-depth parameter collection of the borehole. A vertical exploration hole is constructed on the ground, the hole depth is greater than or equal to 200m, and the following parameters are synchronously obtained every 10m: RQDi (%) - rock quality index, σci (MPa) - uniaxial compressive strength, Vpmi (m / s) - rock mass longitudinal wave velocity, Vpri (m / s) - rock longitudinal wave velocity, Ki (cm / s) - permeability coefficient, to generate a shaft surrounding rock lithology (classification, RQD index, KV index) depth change diagram.

[0010] Further, the lithology index Ai is calculated. Wherein, , , BQi, RQDi, σci, KVi, Vpmi, Vpri are the basic mass index of rock mass, rock mass quality index, uniaxial compressive strength, rock mass integrity coefficient, longitudinal wave velocity of rock mass, longitudinal wave velocity of rock, and a schematic diagram of the change of the lithology index Ai of the wellbore surrounding rock with depth is generated.

[0011] Further, the permeability coefficient Ki of each point is calculated. In addition to the measured permeability coefficient K1 of the measuring point, the calculation formula of the permeability coefficient Ki of the remaining point is: , , wherein Ki, RQDi, Kvi are the permeability coefficient of each point, the rock mass quality index, and the rock mass integrity coefficient; K1, RQD1, Kv1 are the measured permeability coefficient (obtained by borehole water pressure test), rock mass quality index, and rock mass integrity coefficient at a certain measuring point; , the attenuation index is 2.5 by default, the range is 1.5-3.0, and is determined by water pressure test inversion; β is the proportional coefficient.

[0012] Further, the hydrological index Bi is calculated. , wherein Ki is the permeability coefficient at point i, Kmax=1×10⁻1cm / s, Kmin=1×10⁻7cm / s, it is assumed that when Ki=Kmax, Bi=0, at this time it is a strong water permeable state, when Ki=Kmin, Bi=1, at this time it is a relative water-resisting state, and a schematic diagram of the change of the hydrology (permeability coefficient) and the hydrological index Bi with depth is generated.

[0013] Further, the comprehensive index Ci is calculated. The Ai and Bi are linearly coupled by using different weight functions to obtain the comprehensive index Ci, and the calculation formula is: when the wellbore supporting engineering operation is carried out, , ; when the wellbore water control engineering operation is carried out, , .

[0014] Further, the grade threshold is unified. Ci>0.60 is grade I, the surrounding rock is stable; 0.40-0.60 is grade II, the surrounding rock is basically stable; 0.20-0.40 is grade III, the surrounding rock is locally stable; 0.10-0.20 is grade IV, the surrounding rock is unstable; and Ci<0.10 is grade V, the surrounding rock is extremely unstable.

[0015] Further, the full-depth statistical table is generated. The depth, Ci, and grade three results are imported into the platform, and a 200m full-depth statistical graph is output, and a schematic diagram of the change of the comprehensive index Ci of the wellbore surrounding rock with depth is generated.

[0016] The present application has the following beneficial effects:

[0017] 1. Full column continuity: For the first time, the grade distribution of the entire hole surrounding rock is realized from the ground to 200m underground with 10m resolution, avoiding the lack of representation of "point evaluation".

[0018] 2. Permeability quantification: The permeability coefficient K is included in the dimensionless index system with the same dimension as the lithology, and the field misjudgment rate is reduced from 30% to 7%.

[0019] 3. Unified threshold: A Ci grade threshold independent of depth is proposed to avoid design confusion caused by "one hole with multiple marks". BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of the change of wellbore surrounding rock lithology (classification, RQD index, KV index) with depth according to the present application;

[0021] Figure 2 is a schematic diagram of the change of wellbore surrounding rock lithology index Ai with depth according to the present application;

[0022] Figure 3 is a schematic diagram of the change of wellbore surrounding rock permeability coefficient and hydrological index Bi with depth according to the present application;

[0023] Figure 4 is a schematic diagram of the change of wellbore surrounding rock comprehensive index Ci with depth according to the present application; DETAILED DESCRIPTION

[0024] REFERENCE Figures 1-4 A wellbore comprehensive geological model construction method based on continuous and quantitative classification of surrounding rock, comprising the following steps:

[0025] S1: A vertical exploration hole is constructed on the ground surface in the wellbore construction area, the hole depth of the exploration hole is set to 200-500m, and surrounding rock geological parameters and surrounding rock hydrological parameters are collected along the vertical depth direction of the exploration hole;

[0026] S2: Based on the surrounding rock geological parameters collected in step S1, the lithology index Ai at the corresponding vertical depth position is calculated by a pre-designed calculation formula;

[0027] S3: Based on the surrounding rock hydrological parameters collected in step S1, the hydrological index Bi at the corresponding vertical depth position is calculated by a pre-designed calculation formula;

[0028] S4: According to the actual application scene of the wellbore project, different weight functions are used to linearly couple and calculate the lithology index Ai obtained in step S2 and the hydrological index Bi obtained in step S3, to obtain a comprehensive index Ci;

[0029] S5: Set a unified grade classification threshold for all exploration boreholes, and classify the surrounding rock grades into five categories: Grade I, Grade II, Grade III, Grade IV, and Grade V based on the comprehensive index Ci. Generate a statistical table of surrounding rock grades for the entire depth range of the exploration boreholes, and complete the construction of the comprehensive geological model of the wellbore.

[0030] Furthermore, in step S1, geological and hydrological parameters of the surrounding rock are collected synchronously every 10m along the vertical depth direction of the exploration hole;

[0031] The surrounding rock geological parameters include rock mass quality index RQDi, uniaxial compressive strength σci, rock mass longitudinal wave velocity Vpmi, and rock longitudinal wave velocity Vpri.

[0032] The surrounding rock hydrological parameters include the hydrological permeability coefficient K1 at a fixed measuring point in the wellbore, which is obtained through borehole pressure water test.

[0033] Furthermore, the formula for calculating the lithological index Ai in step S2 is: Ai = (BQi + RQDi×0.01 +σci×0.001 + KVi) / 4, where:

[0034] BQi is the basic quality index of the rock mass at point i, and its calculation is based on the "Engineering Rock Mass Classification Standard" (GB / T50218-2014).

[0035] KVi is the rock mass integrity coefficient at point i, and KVi = (Vpmi / Vpri)²;

[0036] RQDi is the rock mass quality index at point i, σci is the uniaxial compressive strength at point i, Vpmi is the longitudinal wave velocity of the rock mass at point i, and Vpri is the longitudinal wave velocity of the rock at point i.

[0037] When core fragmentation prevents direct measurement of Vpri, the empirical value of Vpri is adopted from similar rocks.

[0038] The above calculation formula restricts the range of lithological index Ai to the interval (0, 1).

[0039] Furthermore, in step S3, in addition to the permeability coefficient K1 measured at the fixed measuring point in step S1, the permeability coefficient Ki at the other vertical depth points is calculated using the following formula:

[0040] Ki = K1×(RQDi / RQD1)^α × (KVi / Kv1)^β;

[0041] Where: Ki is the permeability coefficient of the point to be calculated, RQDi is the rock mass quality index of the point to be calculated, and KVi is the rock mass integrity coefficient of the point to be calculated.

[0042] K1 is the measured permeability coefficient at the fixed measuring point, RQD1 is the rock mass quality index at the fixed measuring point, and Kv1 is the rock mass integrity coefficient at the fixed measuring point.

[0043] α is the attenuation index, with a default value of 2.5 and a range of 1.5 to 3.0. It is determined by inversion through borehole water pressure test.

[0044] β is a proportionality coefficient, which is determined by testing based on the geological conditions of the surveyed area.

[0045] Furthermore, the formula for calculating the hydrological index Bi in step S3 is as follows: Ki is the permeability coefficient at point i, Kmax and Kmin are fixed boundaries and do not change with pore depth, Kmax=1×10⁻1cm / s, Kmin=1×10⁻7cm / s;

[0046] When Ki=Kmax, Bi=0, which is a highly permeable state. When Ki=Kmin, Bi=1, which is a relatively impermeable state. The above calculation formula restricts the value range of the hydrological index Bi to the interval (0,1).

[0047] Furthermore, combining the permeability coefficient characteristics of water in rock and the permeability classification standard, the hydrological index Bi is divided into 5 specific levels for rock mass stability:

[0048] When Bi>0.833, it is level 1, corresponding to the surrounding rock's relative water-tightness level;

[0049] When 0.667≤Bi≤0.833, it is level 2, corresponding to a slightly permeable surrounding rock.

[0050] When 0.333≤Bi<0.667, it is level 3, corresponding to a weakly permeable surrounding rock.

[0051] When 0.167≤Bi<0.333, it is level 4, corresponding to a medium permeability level of the surrounding rock;

[0052] When Bi < 0.167, it is level 5, corresponding to a highly permeable surrounding rock.

[0053] Furthermore, the linear coupling calculation methods for different application scenarios in step S4 are as follows:

[0054] When the application scenario is wellbore support engineering, the formula for calculating the comprehensive index Ci is: Where Ai is a lithological index and Bi is a hydrological index. ,and ;

[0055] When the application scenario is well casing water control engineering operations, the formula for calculating the comprehensive index Ci is: Where Ai is a lithological index and Bi is a hydrological index. ,and ;

[0056] By using the linear coupling with different weights, the weights of lithological and hydrological indicators can be dynamically adjusted under different engineering scenarios, highlighting the penalizing effect on the quality of surrounding rock under different engineering conditions.

[0057] Furthermore, the unified threshold for classifying the surrounding rock grade in step S5 is independent of the borehole depth and applies to the entire borehole. The specific classification criteria are as follows:

[0058] When Ci > 0.60, the surrounding rock grade is Class I, corresponding to a stable surrounding rock state;

[0059] When 0.40≤Ci≤0.60, the surrounding rock grade is Class II, corresponding to a basically stable state of the surrounding rock;

[0060] When 0.20≤Ci<0.40, the surrounding rock grade is Class III, corresponding to a locally stable state of the surrounding rock;

[0061] When 0.10≤Ci<0.20, the surrounding rock grade is IV, corresponding to an unstable state of the surrounding rock;

[0062] When Ci < 0.10, the surrounding rock grade is V, which corresponds to an extremely unstable state of the surrounding rock.

[0063] Specifically, the implementation steps of the wellbore integrated geological model construction method based on continuous quantitative grading of surrounding rock according to the present invention are as follows:

[0064] Step 1: Drill one vertical exploration borehole at a depth of 250m on the surface. Obtain rock cores through geological drilling. Every 10m, simultaneously acquire the following parameters using equipment such as a rock pressure testing machine and sonic logging tool: RQDi (%) – rock quality index, σci (MPa) – uniaxial compressive strength, Vpmi (m / s) – longitudinal wave velocity of the rock mass, Vpri (m / s) – longitudinal wave velocity of the rock mass, and K1 (cm / s) at a depth of 80m – permeability coefficient. The acquired data are shown in Table 1. Generate a schematic diagram of the variation of surrounding rock lithology (classification, RQD index, KV index) with depth, as shown below. Figure 1 As shown.

[0065] Step 2: Calculate the lithological index Ai every 10 meters of vertical depth. ,in, , The calculation results are shown in Table 2. A schematic diagram illustrating the variation of the wellbore surrounding rock lithology index Ai with depth is also provided. Figure 2 As shown.

[0066] Step 3: Calculate the permeability coefficient Ki for every 10 meters of vertical depth using the permeability coefficients K1, RQD1, and Kv1 at a depth of 80 meters, and RQDi and Kvi at other points. , This embodiment describes a well casing water control project. Taking 2.5, the calculation results are shown in Table 1.

[0067] Step 4: Calculate the hydrological index Bi every 10 meters based on vertical depth. The calculation results are shown in Table 2. A schematic diagram of the changes in surrounding rock hydrology (permeability coefficient) and hydrological index Bi with depth is generated, as shown below. Figure 3 As shown.

[0068] Step 5: Calculate the comprehensive index Ci every 10 meters of vertical depth. The comprehensive index Ci uses different weighting functions to linearly couple Ai and Bi in different application scenarios. In this embodiment, which is a well casing water control project, α1 is set to 0.2 and α2 to 0.8 in the Ci calculation formula. The calculation results are shown in Table 2.

[0069] Step 6: According to the unified grade threshold, Ci>0.60 is Grade I, the surrounding rock is stable; 0.40–0.60 is Grade II, the surrounding rock is basically stable; 0.20–0.40 is Grade III, the surrounding rock is locally stable; 0.10–0.20 is Grade IV, the surrounding rock is unstable; Ci<0.10 is Grade V, the surrounding rock is extremely unstable. The grades are classified accordingly.

[0070] Step 7: Import the (Depth, Ci, Grade) three-list into the platform, output a statistical table for the entire 250m depth, as shown in Table 2, and generate a schematic diagram of the variation of the wellbore surrounding rock comprehensive index Ci with depth, as shown in Table 2. Figure 4 As shown.

[0071] Table 1 Statistical Table of Parameters at Different Depths

[0072]

[0073] Table 2 Statistical Table of Three Indicators at Different Depths

[0074]

Claims

1. A method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock, characterized in that, Includes the following steps: S1: Construct a vertical exploration borehole on the surface of the well construction area. The depth of the exploration borehole is set to 200~500m. Collect geological and hydrological parameters of the surrounding rock in segments along the vertical depth direction of the exploration borehole. S2: Based on the geological parameters of the surrounding rock collected in step S1, the lithological index Ai at the corresponding vertical depth position is calculated using a preset calculation formula; S3: Based on the surrounding rock hydrological parameters collected in step S1, the hydrological index Bi at the corresponding vertical depth position is calculated using a preset calculation formula. S4: Based on the actual application scenario of well shaft engineering, different weighting functions are used to linearly couple the lithological index Ai obtained in step S2 and the hydrological index Bi obtained in step S3 to obtain the comprehensive index Ci; S5: Set a unified grade classification threshold for all exploration boreholes, and classify the surrounding rock grades into five categories: Grade I, Grade II, Grade III, Grade IV, and Grade V based on the comprehensive index Ci. Generate a statistical table of surrounding rock grades for the entire depth range of the exploration boreholes, and complete the construction of the comprehensive geological model of the wellbore.

2. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock as described in claim 1, characterized in that, In step S1, geological and hydrological parameters of the surrounding rock are collected synchronously every 10m along the vertical depth direction of the exploration hole. The surrounding rock geological parameters include rock mass quality index RQDi, uniaxial compressive strength σci, rock mass longitudinal wave velocity Vpmi, and rock longitudinal wave velocity Vpri. The surrounding rock hydrological parameters include the hydrological permeability coefficient K1 at a fixed measuring point in the wellbore, which is obtained through borehole pressure water test.

3. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock as described in claim 1, characterized in that, The formula for calculating the lithological index Ai in step S2 is: Ai = (BQi + RQDi×0.01 + σci×0.001 + KVi) / 4, where: BQi is the basic quality index of the rock mass at point i, and its calculation is based on the "Engineering Rock Mass Classification Standard" (GB / T 50218-2014). KVi is the rock mass integrity coefficient at point i, and KVi = (Vpmi / Vpri)²; RQDi is the rock mass quality index at point i, σci is the uniaxial compressive strength at point i, Vpmi is the longitudinal wave velocity of the rock mass at point i, and Vpri is the longitudinal wave velocity of the rock at point i. When core fragmentation prevents direct measurement of Vpri, the empirical value of Vpri is adopted from similar rocks. The above calculation formula restricts the range of lithological index Ai to the interval (0, 1).

4. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock as described in claim 1, characterized in that, In step S3, except for the permeability coefficient K1 measured at the fixed measuring point in step S1, the permeability coefficient Ki at the other vertical depth points is calculated using the following formula: Ki = K1×(RQDi / RQD1)^α × (KVi / Kv1)^β; Where: Ki is the permeability coefficient of the point to be calculated, RQDi is the rock mass quality index of the point to be calculated, and KVi is the rock mass integrity coefficient of the point to be calculated. K1 is the measured permeability coefficient at the fixed measuring point, RQD1 is the rock mass quality index at the fixed measuring point, and Kv1 is the rock mass integrity coefficient at the fixed measuring point. α is the attenuation index, with a default value of 2.5 and a range of 1.5 to 3.

0. It is determined by inversion through borehole water pressure test. β is a proportionality coefficient, which is determined by testing based on the geological conditions of the surveyed area.

5. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock according to claim 1, characterized in that, The formula for calculating the hydrological index Bi in step S3 is as follows: ; K i Let K be the permeability coefficient at point i. max With K min To ensure a fixed boundary that does not change with hole depth, K max =1×10⁻ 1 cm / s, K min =1×10⁻ 7 cm / s; When K i =K max At that time, B i =0, indicating a highly permeable state. When K = 0, the water permeability is reduced. i =K min At that time, B i =1, at which point it is in a relatively watertight state; the above calculation formula restricts the value range of the hydrological index Bi to the interval (0,1).

6. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock as described in claim 5, characterized in that, Based on the permeability coefficient characteristics of water in rock and the permeability classification standard, the hydrological index Bi is divided into 5 specific levels for rock mass stability: When Bi>0.833, it is level 1, corresponding to the surrounding rock's relative water-tightness level; When 0.667≤Bi≤0.833, it is level 2, corresponding to a slightly permeable surrounding rock. When 0.333≤Bi<0.667, it is level 3, corresponding to a weakly permeable surrounding rock. When 0.167≤Bi<0.333, it is level 4, corresponding to a medium permeability level of the surrounding rock; When Bi < 0.167, it is level 5, corresponding to a highly permeable surrounding rock.

7. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock according to claim 1, characterized in that, The linear coupling calculation methods for different application scenarios in step S4 are as follows: When the application scenario is wellbore support engineering, the formula for calculating the comprehensive index Ci is: Where Ai is a lithological index and Bi is a hydrological index. ,and ; When the application scenario is well casing water control engineering operations, the formula for calculating the comprehensive index Ci is: Where Ai is a lithological index and Bi is a hydrological index. ,and ; By using the linear coupling with different weights, the weights of lithological and hydrological indicators can be dynamically adjusted under different engineering scenarios, highlighting the penalizing effect on the quality of surrounding rock under different engineering conditions.

8. The method for constructing a comprehensive geological model of a wellbore based on continuous quantitative grading of surrounding rock according to claim 1, characterized in that, The unified threshold for classifying the surrounding rock grade in step S5 is independent of the borehole depth and applies to the entire borehole. The specific classification criteria are as follows: When Ci > 0.60, the surrounding rock grade is Class I, corresponding to a stable surrounding rock state; When 0.40≤Ci≤0.60, the surrounding rock grade is Class II, corresponding to a basically stable state of the surrounding rock; When 0.20≤Ci<0.40, the surrounding rock grade is Class III, corresponding to a locally stable state of the surrounding rock; When 0.10≤Ci<0.20, the surrounding rock grade is IV, corresponding to an unstable state of the surrounding rock; When Ci < 0.10, the surrounding rock grade is V, which corresponds to an extremely unstable state of the surrounding rock.

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