A method for estimating rock material strength parameters based on measurement while drilling data

Abstract

The present invention provides a method for estimating rock material strength parameters based on while drilling measurement data, and relates to the field of rock mechanics and measurement technology. The method includes: analyzing the force in the process of cutting rock, determining the relationship between rock compressive strength and cutting force; performing force analysis based on the Mohr-Coulomb strength criterion, determining the relationship between cutting force and basic rock mechanical parameters cohesion and internal friction angle; determining the functional expression of rock cohesion and internal friction angle represented by rock compressive strength and cutting force; representing cutting force, compressive strength, and one-time drilling feed depth by while drilling measurement parameters drilling speed, rotation speed, and torque, determining the internal friction angle and cohesion represented by while drilling measurement parameters and drill blade parameters, and analyzing errors; the method can be applied to while drilling measurement of rock material strength parameters. The method can realize real-time monitoring, and also has the advantages of high precision and low cost.

Description

Technical Field

[0001] The invention relates to the field of rock mechanics and measurement technology, and in particular provides a method for estimating rock material strength parameters based on while-drilling measurement data. Background Art

[0002] Measurement while drilling (MWD) is an important technical means in engineering fields such as mining, tunneling, oil extraction and geological exploration. It is a technology that monitors drilling parameters such as drilling speed, rotation speed, torque and drilling pressure in real time during the drilling process of the drilling rig, and uploads the data to the terminal for processing and analysis. Lithology identification while drilling is a further development and application of measurement while drilling technology. Lithology identification while drilling is a specific process of distinguishing various rock properties in real time during the drilling process. Measurement while drilling technology generally monitors four parameters during rock drilling: drilling pressure, drilling speed, rotation speed and torque. These four drilling parameters are used to reflect the stress distribution of rocks or the distribution of rock layers.

[0003] The Mohr-Coulomb model is widely used in engineering practice, and its material parameters are usually obtained through indoor tests. At present, there are very few methods that can directly measure the material strength parameters required by the Mohr-Coulomb model through a downhole measurement device at the actual engineering site. Often, during construction, the acquisition of strength material parameters makes the construction steps complicated and cumbersome, which not only takes extra time, but also requires consideration of extra economic factors.

[0004] Compared with the traditional method of obtaining the strength parameters of rock materials based on the Mohr-Coulomb model, on-site measurement while drilling is real-time, fast, time-saving, and labor-saving, and saves construction costs. The parameters we need can be recorded through the on-site measurement while drilling device, and transmitted to the data collector through the sensor. The target data is then obtained through the data from the data collector. Even when conditions are sufficient, the sensor can be directly connected to an explosion-proof computer, and the sensor data can be directly processed by the computer. The target data can be obtained while drilling, and the curve trend of the target data can be analyzed, and judgment can be made based on the size of the target data value. Summary of the invention

[0005] In order to obtain the basic strength parameters of rock through the parameters collected by the while drilling measurement device, such as drilling speed, rotation speed, torque and drill bit related dimensional parameters, and realize the rapid estimation of rock strength parameters at the engineering site, the present invention provides a method for estimating rock material strength parameters based on while drilling measurement data, and the specific technical scheme is as follows.

[0006] A method for estimating strength parameters of rock materials based on measurement while drilling data, comprising:

[0007] S1. Conduct force analysis on rock cutting during drilling to determine the relationship between rock compressive strength and cutting force;

[0008] S2. Conduct force analysis based on the Mohr-Coulomb strength criterion as the failure condition to determine the relationship between cutting force and the basic mechanical parameters of rock, namely cohesion and internal friction angle;

[0009] S3. Functional expressions of rock cohesion and internal friction angle expressed in terms of rock compressive strength and cutting force;

[0010] S4. The cutting force, compressive strength, and one-time drilling feed depth are expressed by the drilling speed, rotation speed, and torque measured while drilling parameters, and the internal friction angle and cohesion expressed by the drilling measurement parameters and drill blade parameters are determined;

[0011] S5. Analyze errors and check the accuracy of calculations of internal friction angle and cohesion.

[0012] Preferably, the method is applied to measure the internal friction angle, cohesion and uniaxial compressive strength of rock during drilling.

[0013] It is also preferred that the functional expression of rock compressive strength is:

[0014]

[0015] Where F k,p is the cutting force, ξ2 is the dynamic load coefficient, ξ2=5, b is the width of the wedge drill bit, h is the depth of one drilling feed, μ is the friction coefficient between the cutting edge and the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, R c For compressive strength.

[0016] It is also preferred that the functional expression of the cutting force is:

[0017]

[0018] In the formula, F k,p is the cutting force, ξ1 is the dynamic load coefficient of the cutting force, ξ1=0.6, b is the width of the wedge drill bit, h is the depth of one drilling feed, C is the cohesive force of the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of rock.

[0019] It is also preferred that the functional expression of the internal friction angle is:

[0020]

[0021] In the formula, F k,p is the cutting force, R ccompressive strength, h is the depth of one drilling feed, b is the width of the wedge drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, ξ1 is the dynamic load coefficient of the cutting force, taking ξ1 = 0.6, β is the auxiliary angle, is the internal friction angle of rock.

[0022] It is also preferred that the calculation formula for the internal friction angle of rock is:

[0023]

[0024] Where M is the torque, m is the number of cutting edges, r is the radius of the drill bit, and θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle. is the internal friction angle of the rock, μ is the friction coefficient between the cutting edge and the rock, N is the rotational speed, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6, ξ2 is the dynamic load coefficient, and ξ2=5.

[0025] It is also preferred that the rock cohesion calculation formula is:

[0026]

[0027] Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of the rock, b is the width of the wedge drill bit, μ is the friction coefficient between the cutting edge and the rock, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6 is taken.

[0028] Further preferably, the rock compressive strength calculation formula is:

[0029]

[0030] Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of the rock, b is the width of the wedge drill bit, μ is the friction coefficient between the cutting edge and the rock, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6, ξ2 is the dynamic load coefficient, and ξ2=5.

[0031] It is further preferred that the maximum difference in the internal friction angle is 0.55% and the minimum difference is 0.16%; the maximum difference in the cohesion is 25.6% and the minimum difference is -3.5%; the maximum difference in the uniaxial compressive strength is 22% and the minimum difference is -0.04%.

[0032] The beneficial effect of the method for estimating rock material strength parameters based on downhole measurement data provided by the present invention is that the method can combine the torque, rotation speed and drilling speed measured while drilling to estimate the cohesion and internal friction angle, and use this method to directly determine the strength material parameters of the rock during the rock drilling process, thereby reducing costs and improving testing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The middle one is the force analysis diagram of the drilling process;

[0034] Figure 2 It is a force analysis diagram of a wedge drill bit with compressive strength as the failure condition during cutting;

[0035] Figure 3 It is the force analysis diagram of the wedge drill bit under the condition of Mohr-Coulomb failure criterion during cutting;

[0036] Figure 4 It is the force analysis diagram of the fracture surface during cutting;

[0037] Figure 5 It is a flow chart of acquisition of measurement while drilling data;

[0038] Figure 6 is a flow chart for the implementation of a method for estimating rock material strength parameters based on measurement while drilling data;

[0039] Figure 7 is a comparison chart of the experimental results and the calculated results of the internal friction angle embodiment;

[0040] Figure 8 This is a comparison chart between the rock cohesion test results and the calculation results of this method;

[0041] Fig. 9 This is a comparison chart between the rock compressive strength test results and the calculation results of this method. DETAILED DESCRIPTION

[0042] Combination Figures 1 to 9 As shown, a specific implementation method of a method for estimating rock material strength parameters based on while drilling measurement data provided by the present invention is described.

[0043] like Figure 1As shown in the figure, the force analysis of the drilling bit: the drill bit is divided into two parts when drilling into the rock, one is the pressing process perpendicular to the rock layer, and the other is the cutting process parallel to the rock layer. During the drilling process, it will be subjected to the pressing reaction force and the cutting reaction force. Then, through the force analysis of the fracture surface during the pressing process and the cutting process, the Mohr-Coulomb strength criterion can be used to calculate the magnitude of the cutting force and the pressing force at a certain drilling depth and the expression of the related formula. Without considering the pressing force and the pressing process, the specific cutting process and the force analysis of the cutting process are explained.

[0044] A method for estimating strength parameters of rock materials based on measurement while drilling data, comprising:

[0045] S1. Perform force analysis on rock cutting during drilling, and determine the relationship between rock compressive strength and cutting force using rock compressive strength as the failure condition;

[0046] The functional expression of rock compressive strength is:

[0047]

[0048] Where F k,p is the cutting force, ξ2 is the dynamic load coefficient, ξ2=5, b is the width of the wedge drill bit, h is the depth of one drilling feed, μ is the friction coefficient between the cutting edge and the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, R c For compressive strength.

[0049] In order to determine the relationship between rock compressive strength and cutting force, a stress analysis was conducted. Figure 2 As shown in the figure, during the drilling process of the wedge drill bit, the rock is subjected to a downward drilling pressure and a cutting force consistent with the cutting direction. Similarly, if the rock is broken during the drilling process, it must be that the stress of the drill bit in the process of cutting the rock has reached the compressive strength of the rock, causing the rock to be damaged. Taking the compressive strength of the rock as the damage condition, static force balance is performed in the cutting direction, and the friction between the cutting edge and the rock contact surface is considered. Mechanical calculations are performed to obtain the relationship between the compressive strength of the rock and the cutting force.

[0050] The functional expression of cutting force is:

[0051]

[0052] In the formula, F k,p is the cutting force, ξ1 is the dynamic load coefficient of the cutting force, ξ1=0.6, b is the width of the wedge drill bit, h is the depth of one drilling feed, C is the cohesive force of the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of rock.

[0053] In order to analyze the relationship between cutting force and rock internal friction angle and cohesion, a force analysis was conducted. Figure 3 , Figure 4 As shown in the figure, the rock will peel off layer by layer during the cutting process. Assuming that the inclination angle of the fracture surface is, since the cohesion and internal friction angle are considered, the force analysis is carried out on the fracture surface, and the cutting force is decomposed into the pressure perpendicular to the fracture surface and the shear force parallel to the fracture surface. The Mohr-Coulomb strength criterion is used as the condition for the failure of the fracture surface, and the compressive stress and shear stress of the fracture surface are used as the basic parameters. Substituting them into the Mohr-Coulomb failure condition formula, the relationship between the cutting force, cohesion and internal friction angle can be obtained.

[0054] S2. Conduct force analysis based on the Mohr-Coulomb strength criterion as the failure condition to determine the relationship between cutting force and the basic mechanical parameters of rock, namely cohesion and internal friction angle;

[0055] The function expression of internal friction angle is:

[0056]

[0057] In the formula, F k,p is the cutting force, R c compressive strength, h is the depth of one drilling feed, b is the width of the wedge drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, ξ1 is the dynamic load coefficient of the cutting force, taking ξ1 = 0.6, β is the auxiliary angle, is the internal friction angle of rock.

[0058] S3. Functional expressions of rock cohesion and internal friction angle expressed in terms of rock compressive strength and cutting force;

[0059] S4. The cutting force, compressive strength and feed depth of a single drilling are expressed by the drilling speed, rotation speed and torque of the drilling measurement parameters, and the internal friction angle and cohesion expressed by the drilling measurement parameters and drill edge parameters are determined; the cutting force, compressive strength and feed depth of a single drilling in the function expression are expressed by the drilling speed, rotation speed and torque of the drilling measurement parameters, and the internal friction angle and cohesion completely expressed by the drilling measurement parameters and drill edge parameters are obtained.

[0060] The calculation formula of the internal friction angle of rock is:

[0061]

[0062] Where M is the torque, m is the number of cutting edges, r is the radius of the drill bit, and θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle. is the internal friction angle of the rock, μ is the friction coefficient between the cutting edge and the rock, N is the rotational speed, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6, ξ2 is the dynamic load coefficient, and ξ2=5.

[0063] The formula for calculating the cohesion of rock is:

[0064]

[0065] Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of the rock, b is the width of the wedge drill bit, μ is the friction coefficient between the cutting edge and the rock, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6 is taken.

[0066] The formula for calculating the compressive strength of rock is:

[0067]

[0068] Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of the rock, b is the width of the wedge drill bit, μ is the friction coefficient between the cutting edge and the rock, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6, ξ2 is the dynamic load coefficient, and ξ2=5.

[0069] S5. Analyze errors and check the accuracy of calculation of internal friction angle and cohesion. This method is used to measure the internal friction angle, cohesion and uniaxial compressive strength of rock during drilling.

[0070] This method fully considers the significance of each parameter through the force analysis diagram of the cutting edge cutting rock, and has certain practical significance. However, due to the consideration of the drilling and cutting process, the drilling and pressing process is ignored. The relationship between the parameters is studied from the aspects of cutting force and rock compressive strength. In addition, there are modeling errors and only static analysis is performed, ignoring the dynamic influence. Therefore, there are certain errors.

[0071] Combining this method with rock mechanics experiments, the error of this method is verified. Table 1 shows the material parameters used in the calculation. The parameters come from the test. It is divided into five groups of tests using the same materials and different drilling parameters: drilling pressure, drilling speed, rotation speed, and torque. Substituting the material parameters in the table into the formula, the internal friction angle, cohesion, and compressive strength of the rock can be obtained. Table 2 is a comparison table of rock test results and calculation results of this method.

[0072] Table 1 Material parameters

[0073]

[0074] Table 2 Results comparison table

[0075]

[0076] The test results were compared with the theoretical formula results to verify the agreement between the theoretical results and the test results. The maximum difference in the internal friction angle was 0.55%, and the minimum difference was 0.16%; the maximum difference in cohesion was 25.6%, and the minimum difference was -3.5%; the maximum difference in uniaxial compressive strength was 22%, and the minimum difference was -0.04%.

[0077] The present method can be applied to the rock parameters obtained through the calculation formula on the basis of lithology measurement while drilling to intuitively reflect the lithology characteristics of the detected mine and distinguish different lithologies, such as the stratification of the lithology roof, the thickness of the interface, the thickness of the coal seam, etc., which can be characterized by different parameters.

[0078] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for estimating rock material strength parameters based on measurement while drilling data, characterized in that: include: S1. Conduct force analysis on rock cutting during drilling to determine the relationship between rock compressive strength and cutting force; S2. Conduct force analysis based on the Mohr-Coulomb strength criterion as the failure condition to determine the relationship between cutting force and the basic mechanical parameters of rock, namely cohesion and internal friction angle; S3. Determine the functional expressions of rock cohesion and internal friction angle expressed in terms of rock compressive strength and cutting force; S4. The cutting force, compressive strength, and one-time drilling feed depth are expressed by the drilling speed, rotation speed, and torque measured while drilling parameters, and the internal friction angle and cohesion expressed by the drilling measurement parameters and drill blade parameters are determined; S5. Analyze errors and check the accuracy of calculation of internal friction angle and cohesion; Applied to measure the internal friction angle, cohesion and uniaxial compressive strength of rocks during drilling; The functional expression of the rock compressive strength is: Where F k,p is the cutting force, ξ2 is the dynamic load coefficient, ξ2=5, b is the width of the wedge drill bit, h is the depth of one drilling feed, μ is the friction coefficient between the cutting edge and the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, R c is the compressive strength; The functional expression of the cutting force is: In the formula, F k,p is the cutting force, ξ1 is the dynamic load coefficient of the cutting force, ξ1=0.6, b is the width of the wedge drill bit, h is the depth of one drilling feed, C is the cohesive force of the rock, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of rock; The functional expression of the internal friction angle is: In the formula, F k,p is the cutting force, R c is the compressive strength, h is the depth of one drilling feed, b is the width of the wedge drill, θ is the 1 / 2 edge angle of the wedge drill, that is, the cutting edge angle, ξ1 is the cutting force dynamic load coefficient, taking ξ1 = 0.6, β is the auxiliary angle, is the internal friction angle of rock; The calculation formula of the internal friction angle of the rock is: Where M is the torque, m is the number of cutting edges, r is the radius of the drill, and θ is the 1 / 2 edge angle of the wedge drill, i.e. the cutting edge angle. is the internal friction angle of the rock, μ is the friction coefficient between the cutting edge and the rock, ξ1 is the dynamic load coefficient of the cutting force, ξ1=0.6, ξ2 is the dynamic load coefficient, ξ2=5; The calculation formula of the cohesion of the rock is: Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, is the internal friction angle of the rock, b is the width of the wedge drill bit, ξ1 is the dynamic load coefficient of the cutting force, and ξ1=0.6; The calculation formula of the compressive strength of the rock is: Where M is torque, N is speed, V d is the drilling speed, r is the radius of the drill bit, θ is the 1 / 2 edge angle of the wedge drill bit, that is, the cutting edge angle, b is the width of the wedge drill bit, μ is the friction coefficient between the cutting edge and the rock, ξ2 is the dynamic load coefficient, and ξ2=5 is taken.

2. A method for estimating rock material strength parameters based on measurement while drilling data according to claim 1, characterized in that: The maximum difference of the internal friction angle is 0.55%, and the minimum difference is 0.16%; the maximum difference of the cohesion is 25.6%, and the minimum difference is -3.5%; the maximum difference of the uniaxial compressive strength is 22%, and the minimum difference is -0.04%.

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