Determination method for multiple interactions between PDC drill bit and rock

Abstract

The invention belongs to the field of testing of physical and mechanical properties of rocks, and provides a method for measuring multiple interactions between a PDC (Polycrystalline Diamond Compact) drill bit and rocks, which comprises the following steps of: performing drilling experiments under different drilling settings to obtain drilling data; based on the cutting, friction and press-in processes between the drill bit and the rock, a drill bit-rock interaction mechanical model is established; processing the drilling data based on a drill bit-rock interaction mechanical model to obtain the cutting depth d of a drill bit, the normal force w of the drill bit in unit length and the tangential force t of the drill bit in unit length of different drilling settings, drawing a d-w graph, a d-t graph and a t-w graph, and performing linear fitting; and interpreting the intercept and slope of each fitted curve based on a drill bit-rock interaction mechanical model to obtain parameters of various interactions between the PDC drill bit and the rock. The characteristic of press-in force is considered, and the method is closer to the real rock drilling process of the drill bit.

Description

Technical Field

[0001] The invention belongs to the field of rock physical and mechanical property testing, and specifically discloses a method for measuring multiple interactions between a PDC drill bit and a rock. Background Art

[0002] The interaction between the drill bit and the rock includes the difficulty of the rock to resist the penetration of the drill bit, the difficulty of the drill bit to break the rock, the friction between the drill bit and the rock, and other aspects. These interactions can be quantitatively evaluated using parameters such as drillability, specific energy, and friction coefficient. These parameters play a key role in optimizing drilling performance and estimating rock properties. At present, the prior art discloses evaluation methods for specific interactions, some technologies disclose evaluation methods for rock drillability, and some technologies disclose evaluation methods for the friction coefficient between the drill bit and the rock. However, there is a method that can obtain multiple interaction parameters through a single experiment. In addition, it should be noted that the interaction parameters are not only related to the rock properties, but also to the performance of the drill bit. For example, the friction coefficient between the same rock and different drill bits is different, and the ability of the same rock to resist the penetration of different drill bits is also different. However, some methods only focus on the properties of the rock itself, while ignoring the interaction between the drill bit and the rock. Therefore, the interaction parameters obtained from real drilling experiments using a specific drill bit are more instructive for field engineering, but this depends on reliable methods to interpret drilling data and obtain specific information on the interaction between the drill bit and the rock.

[0003] The drill bit-rock interface law, also known as the drilling response model, describes the relationship between the drill bit dynamic parameters and is the theoretical basis for interpreting drilling data. Many studies have focused on developing drilling response models specifically for PDC drill bits, because PDC drill bits are widely used in petroleum engineering and geological exploration, and can achieve large diameter and deep drilling in almost all formations. The interaction between PDC drill bits and rocks is usually regarded as the sum of all single-cutter-rock interactions. Therefore, the drilling process is usually simplified to a single-cutter cutting experiment for research. The process of a single-cutter cutting experiment is: the cutter head is set at a specific cutting depth, moves parallel to the rock surface, and measures the force acting on the cutter head and the characteristics of the rock cuttings. Many scholars have proposed various drill bit-rock interaction interface laws based on the understanding of the phenomena and results of single-cutter cutting experiments. Among them, the phenomenological model proposed by Detournay and Defourny for PDC drill bits is the most representative. This model has been verified, applied and developed by a large number of single-cutter cutting experiments. However, these models usually assume that there are two processes in the interaction between the drill bit and the rock: cutting and friction contact, and ignore the process of the drill bit pressing into the rock. This makes it difficult for these models to interpret full-scale drilling data from actual projects.

[0004] In summary, a model suitable for interpreting drilling data of full-size PDC drill bits is urgently needed to obtain multi-faceted information on the interaction between drill bits and rocks from a single drilling experiment. Therefore, it is very necessary to study and design a new method for measuring multiple interactions between PDC drill bits and rocks to solve the problems existing in the existing evaluation of the interaction between drill bits and rocks. Summary of the invention

[0005] The present invention proposes a method for measuring multiple interactions between a PDC drill bit and rock to solve the problems that the existing methods for evaluating the interaction between a drill bit and rock only focus on the properties of the rock itself and ignore the interaction between the drill bit and the rock, a single experiment cannot obtain multiple interaction parameters, and the process of the drill bit pressing into the rock is ignored, resulting in inaccurate data.

[0006] The present invention provides a method for determining multiple interactions between a PDC drill bit and a rock, comprising the following steps: S1. Performing drilling experiments under different drilling settings to obtain drilling data under different drilling settings; S2. Based on the cutting, friction and indentation process between the drill bit and the rock, a mechanical model of drill bit-rock interaction is established; S3. Based on the drill bit-rock interaction mechanical model obtained in step S2, the drilling data obtained in step S1 are processed to obtain the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit under different drilling settings, and the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit are plotted in a dw diagram, a dt diagram, and a tw diagram. After the plotting is completed, linear fitting is performed on the data in the dw diagram, the dt diagram, and the tw diagram, respectively, to obtain the intercept and slope of each fitting curve; S4. Based on the drill bit-rock interaction mechanical model obtained in step S2, the intercept and slope of each fitting curve obtained in step S3 are interpreted to obtain various interaction parameters between the PDC drill bit and the rock.

[0007] According to a method for determining multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, step S1 comprises: S101. Equipment and sample preparation: Check that the drilling rig, pressure control system and data logger are functioning properly, prepare rock samples, and ensure that the size and shape of the rock samples are suitable for the experimental requirements; S102. Initial setting: install the PDC drill bit on the drilling rig and ensure that the PDC drill bit is firmly fixed, place the PDC drill bit on the rock surface, start the pressure control system, set the feed pressure to the initial value, and ensure that the feed pressure is stable; S103. Start drilling: When the PDC drill bit stabilizes at the initial feed pressure value, the drilling process begins, and the PDC drill bit drills the rock sample at a constant speed; during the drilling process, the data recorder records the drilling data; S104. Pressure increase and drilling: After drilling for a period of time, the feed pressure value is increased and the drilling continues at a new stable feed pressure value, and the data recorder records the drilling data; S105 repeat the experiment: repeat step S104 until the maximum feed pressure value of the experimental design or the predetermined test time is reached to end the experiment, the data recorder records the drilling data at each stage; S106. Equipment shutdown and cleaning: shut down the drilling rig, pressure control system and data recorder, clean up the experimental site, and remove the PDC drill bit and rock samples.

[0008] According to a method for measuring multiple interactions between a PDC drill bit and rock in some embodiments of the present application, in step S1, the drilling data includes the thrust of the drill bit, the radius of the drill bit, the torque of the drill bit, the drilling speed of the drill bit and the rotation speed of the drill bit.

[0009] According to a method for determining multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, in step S2, the cutting, friction and pressing process between the drill bit and the rock includes stage I and stage II; In the first stage, the normal force w per unit length of the drill bit is less than the critical contact force, and the drill bit rubs against the rock surface, and no obvious cutting depth d of the drill bit is generated; The relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in the first stage is shown in formula (1): (1) in, Indicates the friction angle between the bottom of the drill bit and the rock, Indicates the coefficient of friction between the bottom of the drill bit and the rock; The second stage is an effective drilling process. In the second stage, the normal force w per unit length of the drill bit is greater than the critical contact force, radial cracks of the rock begin to form, cracks propagating along a linear path are generated between the rock cuttings and the intact rock, the friction between the drill bit and the rock surface reaches a maximum value, and the contact force between the drill bit and the rock surface is equal to the sum of the pressing force and the critical contact force. The increase in the pressing force causes the drill bit to be further pressed into the rock, and the cutting depth d of the drill bit is increased without increasing the friction between the drill bit and the rock surface. The relationship between the normal force w per unit length of the drill bit and the cutting depth d of the drill bit in the second stage is shown in formula (2): (2) in, It indicates the contact force required to increase the unit cutting depth and is used to characterize the drillability of rock. It represents the ratio of normal cutting force to tangential cutting force on the cutting surface. Represents the specific energy of rock, used to characterize the difficulty of cutting and crushing rock. It represents the critical contact force, which is used to characterize the ease with which the drill bit penetrates the rock surface; The relationship between the tangential force t per unit length of the drill bit and the cutting depth d of the drill bit in the second stage is shown in formula (3): (3) The relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in the second stage is shown in formula (4): (4) in, The resistance coefficient of the effective drilling process is shown in formula (5): (5) The normal force w per unit length of the drill bit is as shown in formula (6): (6) in, Indicates the thrust of the drill bit, Indicates the radius of the drill bit; The tangential force t per unit length of the drill bit is as shown in formula (7): (7) in, Indicates the torque of the drill bit; The cutting depth d of the drill bit is as shown in formula (8): (8) in, Indicates the drilling speed of the drill bit. Indicates the speed of the drill bit.

[0010] According to a method for measuring multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, in step S3, the drill bit thrust, drill bit radius, drill bit torque, drill bit drilling speed and drill bit rotation speed of the drilling data are input into the drill bit-rock interaction mechanical model obtained in step S2, and the cutting depth d of the drill bit, the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit are obtained by formulas (6) to (8).

[0011] According to a method for determining multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, the linear fitting of the data in the dw diagram, dt diagram and tw diagram respectively in step S3 includes fitting the data in stage I in the tw diagram and the data in stage II in the dw diagram, dt diagram and tw diagram respectively, to obtain a fitting curve of stage I in the tw diagram, a fitting curve of stage II in the dw diagram, a fitting curve of stage II in the dt diagram and a fitting curve of stage II in the tw diagram.

[0012] According to a method for measuring multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, the step S3 of obtaining the intercept and slope of each fitting curve includes respectively obtaining the slope of the tw graph stage I fitting curve, the intercept of the dw graph stage II fitting curve, the slope of the dw graph stage II fitting curve, the intercept of the dt graph stage II fitting curve, the slope of the dt graph stage II fitting curve, the intercept of the tw graph stage II fitting curve and the slope of the tw graph stage II fitting curve.

[0013] According to a method for measuring multiple interactions between a PDC drill bit and a rock in some embodiments of the present application, the parameters of the multiple interactions between the PDC drill bit and the rock in step S4 include the difficulty of the drill bit penetrating the rock surface, the friction coefficient between the bottom of the drill bit and the rock, the drillability of the rock, the specific energy of the rock and the resistance coefficient of the effective drilling process.

[0014] According to some embodiments of the present application, a method for measuring multiple interactions between a PDC drill bit and a rock is provided. In step S4, the friction coefficient between the bottom of the drill bit and the rock is determined by the inverse of the slope of the fitting curve of the first stage of the tw diagram or by dividing the intercept of the fitting curve of the second stage of the dt diagram by the intercept of the fitting curve of the second stage of the dw diagram. The difficulty of the drill bit penetrating the rock surface is determined by the intercept of the fitting curve of the second stage of the dw diagram. The specific energy of the rock is determined by the slope of the fitting curve of the second stage of the dt diagram. The resistance coefficient of the effective drilling process is determined by the inverse of the slope of the fitting curve of the second stage of the tw diagram. The drillability of the rock is determined by subtracting the ratio of the normal cutting force to the tangential cutting force on the cutting surface and the specific energy of the rock from the slope of the fitting curve of the second stage of the dw diagram.

[0015] The present invention proposes a method for measuring multiple interactions between a PDC drill bit and a rock, which divides the process of interaction between the drill bit and the rock into cutting, friction and pressing processes, and considers the characteristic of the pressing force to divide the contact force between the drill bit and the rock into critical contact force and pressing force, so that the mathematical model of the present invention that describes the interface law between the drill bit and the rock is closer to the actual process of the drill bit drilling into the rock, and the obtained data is more accurate. In addition, the present method can effectively interpret full-size PDC drilling data, and obtain a comprehensive variety of information parameters of the interaction between the drill bit and the rock from a single drilling experiment, and these parameters are of great significance for evaluating the performance of the drill bit and the mechanical properties of the rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of a method for determining multiple interactions between a PDC drill bit and a rock according to the present invention; Figure 2 Schematic diagram of feed pressure setting in a drilling experiment according to an embodiment of the present invention; Figure 3 Schematic diagram of the mechanical model of the interaction between the drill bit and the rock according to the embodiment of the present invention, (a) schematic diagram of the mechanical model of stage I, (b) schematic diagram of the mechanical model of stage II; Figure 4 dw diagram, dt diagram and tw diagram of white granite according to an embodiment of the present invention, (a) is the dw diagram of white granite, (b) is the dt diagram of white granite, and (c) is the tw diagram of white granite; Figure 5 dw diagram, dt diagram and tw diagram of yellow granite according to an embodiment of the present invention, (a) is the dw diagram of yellow granite, (b) is the dt diagram of yellow granite, and (c) is the tw diagram of yellow granite; Figure 6These are the dw diagrams, dt diagrams and tw diagrams of white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite in the embodiments of the present invention. (a) is the dw diagram of white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite, (b) is the dt diagram of white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite, and (c) is the tw diagram of white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite. DETAILED DESCRIPTION

[0017] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0018] Example 1, this example provides a method for determining multiple interactions between a PDC drill bit and a rock, such as Figure 1 As shown, the following steps are included: S1. Performing drilling experiments under different drilling settings to obtain drilling data under different drilling settings; S2. Based on the cutting, friction and indentation process between the drill bit and the rock, a mechanical model of drill bit-rock interaction is established; S3. Based on the drill bit-rock interaction mechanical model obtained in step S2, the drilling data obtained in step S1 are processed to obtain the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit under different drilling settings, and the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit are plotted in a dw diagram, a dt diagram, and a tw diagram. After the plotting is completed, linear fitting is performed on the data in the dw diagram, the dt diagram, and the tw diagram, respectively, to obtain the intercept and slope of each fitting curve; S4. Based on the drill bit-rock interaction mechanical model obtained in step S2, the intercept and slope of each fitting curve obtained in step S3 are interpreted to obtain parameters of various interactions between the PDC drill bit and the rock.

[0019] Example 2: This example provides a method for determining multiple interactions between a PDC drill bit and a rock, comprising the following steps: S1. Performing drilling experiments under different drilling settings to obtain drilling data under different drilling settings; Specifically, step S1 includes: S101. Equipment and sample preparation: Check that the drilling rig, pressure control system and data logger are functioning properly, prepare rock samples, and ensure that the size and shape of rock samples are suitable for the experimental requirements; S102. Initial setting: install the PDC drill bit on the drilling rig and ensure that the PDC drill bit is firmly fixed, place the PDC drill bit on the rock surface, start the pressure control system, set the feed pressure to the initial value, and ensure that the feed pressure is stable; S103. Start drilling: When the PDC drill bit stabilizes at the initial feed pressure value, the drilling process begins, and the PDC drill bit drills the rock sample at a constant rotation speed; during the drilling process, the data recorder records the drilling data; S104. Pressure increase and drilling: After drilling for a period of time, the feed pressure value is increased and drilling continues at the new stable feed pressure value, and the data recorder records the drilling data; S105 repeat the experiment: repeat step S104 until the maximum feed pressure value of the experimental design is reached or the predetermined test time is reached, and the experiment is ended, and the data recorder records the drilling data at each stage; S106. Equipment shutdown and cleanup: shut down the drilling rig, pressure control system and data recorder, clean up the experimental site, and remove the PDC drill bit and rock samples; The drilling data includes the thrust of the drill bit, the radius of the drill bit, the torque of the drill bit, the drilling speed of the drill bit and the rotation speed of the drill bit. More preferably, for each stable drilling stage, the average value of the drilling data of the stage is calculated as a set of drilling data, so that a series of drilling response data under different drilling settings can be obtained from one drilling experiment; As a preferred embodiment of the present invention, the experiment of the present invention uses a two-wing PDC drill bit with a diameter of 50 mm and a back rake angle of 15°. Drilling experiments are carried out on nine kinds of rock samples, including white granite, yellow granite, white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite. In the present embodiment, different drilling settings set different feed pressures. The feed pressure changes during the experiment as shown in FIG. Figure 2 As shown, for Figure 2 In each stage i , calculate the average value of the drilling data of this stage as a set of drilling data, so that a series of drilling data under different feed pressure levels can be obtained from one drilling experiment. In this embodiment, the PDC drill bits in all experiments are operated at a constant speed of 130 revolutions per minute.

[0020] S2. Based on the cutting, friction and indentation process between the drill bit and the rock, a mechanical model of drill bit-rock interaction is established; The equivalent cutter head concept is introduced in this embodiment to simplify the description of the interaction between the drill bit and the rock. The equivalent cutter head concept is that the force acting on the equivalent cutter head is considered to be equivalent to the force acting on the drill bit. Under this theoretical framework, the drilling response can be characterized by three basic quantities: the normal force w per unit length of the drill bit, the tangential force t per unit length of the drill bit, and the cutting depth d of the drill bit. The normal force w per unit length of the drill bit is shown in formula (1): (1) in, Indicates the thrust of the drill bit, Indicates the radius of the drill bit; The tangential force t per unit length of the drill bit is as shown in formula (2): (2) in, Indicates the torque of the drill bit; The cutting depth d of the drill bit is shown in formula (3): (3) in, Indicates the drilling speed of the drill bit. Indicates the speed of the drill bit.

[0021] The concept of equivalent cutter head is based on the following assumptions: the force is evenly distributed over the entire drill bit, and the interface between the drill bit and the rock is independent of the velocity. Then, the dynamic variables of the drill bit can be expressed by the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit, and the kinematic variables of the drill bit can be expressed by a single variable, the cutting depth d of the drill bit; The proposed drill bit-rock interaction mechanical model assumes that there will be two different drilling response stages, including stage I and stage II, as the normal force w per unit length of the drill bit increases. Controls the transition between these two phases. Figure 3 The physical processes of these two stages and the forces acting on the drill bit are shown in detail as follows: In Phase I, if Figure 3 (a) The normal force w per unit length of the drill bit is less than the critical contact force. The friction between the drill bit and the rock surface does not produce a significant cutting depth d of the drill bit. The friction force t f Follow contact force The actual contact area between the drill bit and the rock also increases with the increase of the contact force. The contact force and friction force t f The relationship between the bottom of the drill bit and the rock depends on the friction angle between ,It should be noted that a smaller cutting depth d of the drill bit may be produced at this stage due to the elastic deformation and damage accumulation caused by repeated friction contact between the drill bit and the rock. ,At this stage, the interaction between the drill bit and the rock only involves the friction contact process; The relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in stage I is shown in formula (4): (4) in, Indicates the friction angle between the bottom of the drill bit and the rock, Indicates the coefficient of friction between the bottom of the drill bit and the rock; Phase II is the effective drilling process. In Phase II, Figure 3 (b) The normal force w per unit length of the drill bit is greater than the critical contact force, radial cracks in the rock begin to form, and cracks propagate along a linear path between the cuttings and the intact rock. At the bottom of the drill bit, since the actual contact area between the drill bit and the rock has reached its maximum value, the friction force The component reaches the limit value of critical contact force , the friction between the drill bit and the rock surface reaches its maximum value , and the friction between the drill bit and the rock surface will not change with Then, the remaining contact force, that is, the contact force and critical contact force The difference between , the contact force between the drill bit and the rock surface Equal to the pressure and critical contact force The sum of the pressure The increase in the friction between the drill bit and the rock will cause the drill bit to be further pressed into the rock, thereby increasing the cutting depth d of the drill bit without increasing the friction between the drill bit and the rock surface; on the cutting surface between the drill bit and the rock, there is a tangential cutting force and normal cutting force , tangential cutting force and normal cutting force The relationship between the drill bit back rake angle θ and the friction angle between the drill bit cutting surface and the rock Among them, the friction angle between the cutting surface of the drill bit and the rock It is related to the drill bit back rake angle θ and a constant.

[0022] Phase II is the effective drilling process, which involves three independent processes: cutting, pressing and friction contact. The tangential force t per unit length of the drill bit can be divided into the tangential cutting force acting on the cutting surface and the maximum friction between the drill bit and the rock surface acting on the contact surface , as shown in formula (5): (5) The normal force w per unit length of the drill bit can be divided into the normal cutting force acting on the cutting surface , and the critical contact force acting on the contact surface and pressing force , as shown in formula (6): (6) On the cutting surface between the drill bit and the rock, the tangential cutting force and normal cutting force The cutting depth d of the drill bit increases linearly, and the rate of increase is related to the properties of the rock, as shown in formulas (7) and (8): (7) (8) in, It represents the specific energy of rock, which means the energy required to break a unit volume of rock under given drilling rig and drill bit conditions. Indicates the normal cutting force on the cutting surface Tangential cutting force The ratio is as shown in formula (9): (9) Due to the friction angle between the cutting surface of the drill bit and the rock It is only related to the drill bit back rake angle θ and has nothing to do with the rock, so ζ can be regarded as a constant. The parameter ζ can be determined based on the drill bit back rake angle and rock cutting experiments, or based on the data of relevant papers; At the contact surface between the drill bit and the rock, the critical contact force and the maximum friction between the drill bit and the rock surface acting on the contact surface The relationship between follows the friction law, as shown in formula (10): (10) At the contact surface between the drill bit and the rock, the pressure It increases linearly with the cutting depth d of the drill bit, as shown in formula (11): (11) in, It indicates the contact force required to increase the unit cutting depth and is used to characterize the drillability of rock. It reflects the resistance of the rock to the drilling bit and is related to the rock properties; According to formulas (6), (8), (9), and (11), the relationship between the normal force w per unit length of the drill bit and the cutting depth d of the drill bit in stage II can be obtained as shown in formula (12): (12) in, It indicates the contact force required to increase the unit cutting depth and is used to characterize the drillability of rock. It represents the ratio of normal cutting force to tangential cutting force on the cutting surface. Represents the specific energy of rock, used to characterize the difficulty of cutting and crushing rock. It represents the critical contact force, which is used to characterize the ease with which the drill bit penetrates the rock surface; According to formulas (5), (7), and (10), the relationship between the tangential force t per unit length of the drill bit and the cutting depth d of the drill bit in stage II is shown in formula (13): (13) According to formulas (12) and (13), the relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in stage II is shown in formula (14): (14) in, The resistance coefficient of the effective drilling process represents the ratio of the tangential force to the normal force in the effective drilling process of rock without considering the friction effect, as shown in formula (15): (15) Obviously, formulas (4), (12)-(14) describe a series of linear relationships between the normal force w per unit length of the drill bit, the tangential force t per unit length of the drill bit, and the cutting depth d of the drill bit. The intercepts and slopes of these relationships quantitatively reflect the interaction characteristics between the drill bit and the rock.

[0023] S3. Based on the drill bit-rock interaction mechanical model obtained in step S2, the drilling data obtained in step S1 are processed to obtain the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit under different drilling settings, and the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit are plotted in a dw diagram, a dt diagram, and a tw diagram. After the plotting is completed, linear fitting is performed on the data in the dw diagram, the dt diagram, and the tw diagram, respectively, to obtain the intercept and slope of each fitting curve; Specifically, in step S3, the drill bit thrust, drill bit radius, drill bit torque, drill bit drilling speed and drill bit rotation speed of the drilling data are input into the drill bit-rock interaction mechanical model obtained in step S2, and the drill bit cutting depth d, the drill bit normal force w per unit length and the drill bit tangential force t per unit length are obtained by formula (1) to formula (3).

[0024] The average value of the drilling data in each stable stage is calculated as a set of drilling response data, and each set of response data is plotted into a dw graph, a dt graph, and a tw graph. The linear fitting of the data in the dw graph, the dt graph, and the tw graph includes fitting the data in the first stage of the tw graph and the data in the second stage of the dw graph, the dt graph, and the tw graph, respectively, to obtain the fitting curve of the first stage of the tw graph, the fitting curve of the second stage of the dw graph, the fitting curve of the second stage of the dt graph, and the fitting curve of the second stage of the tw graph. In this embodiment, the dw graph of the white granite is as follows: Figure 4 (a) shows that the dt diagram is Figure 4 (b) and tw diagram as shown Figure 4 (c) shows the dw diagram of yellow granite. Figure 5 (a) shows that the dt diagram is Figure 5 (b) and tw diagram as shown Figure 5 (c) shows the dw diagrams of white sandstone, black sandstone, green sandstone, red granite, basalt, red sandstone and gray granite. Figure 6 (a) shows that the dt diagram is Figure 6 (b) and tw diagram as shown Figure 6 (c) The data of stage II is characterized in that the cutting depth d of the drill bit increases linearly with the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit, while the data of stage I is characterized in that the cutting depth d of the drill bit does not change with the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit.

[0025] Obtaining the intercept and slope of each fitting curve in step S3 includes respectively obtaining the slope of the fitting curve of the first stage of the tw graph, the intercept of the fitting curve of the second stage of the dw graph, the slope of the fitting curve of the second stage of the dw graph, the intercept of the fitting curve of the second stage of the dt graph, the slope of the fitting curve of the second stage of the dt graph, the intercept of the fitting curve of the second stage of the tw graph, and the slope of the fitting curve of the second stage of the tw graph.

[0026] S4. Based on the drill bit-rock interaction mechanical model obtained in step S2, the intercept and slope of each fitting curve obtained in step S3 are interpreted to obtain parameters of various interactions between the PDC drill bit and the rock; Specifically, the parameters of the various interactions between the PDC drill bit and the rock in step S4 include the difficulty of the drill bit penetrating the rock surface, the friction coefficient between the bottom of the drill bit and the rock, the drillability of the rock, the specific energy of the rock and the resistance coefficient of the effective drilling process. These parameters quantitatively characterize the interaction between the drill bit and the rock; In step S4, the friction coefficient between the bottom of the drill bit and the rock is determined by the inverse of the slope of the fitting curve of the first stage of the tw diagram. Or the coefficient of friction between the bottom of the drill bit and the rock can be determined by dividing the intercept of the fitted curve in the second stage of the dt graph by the intercept of the fitted curve in the second stage of the dw graph. The difficulty of the drill bit penetrating the rock surface, i.e. the critical contact force, is determined by the intercept of the fitting curve in the second stage of the dw diagram. The specific energy of the rock is determined by the slope of the fitting curve in the second stage of the dt diagram. The resistance coefficient of the effective drilling process is determined by the inverse of the slope of the fitting curve in stage II of the tw diagram , the ratio of the normal cutting force to the tangential cutting force on the cutting surface is subtracted from the slope of the fitting curve in stage II of the dw diagram Energy ratio to rock Determine the drillability of the rock, that is, the contact force required to increase the unit cutting depth These parameters are of great significance for evaluating the performance of the drill bit and the mechanical properties of the rock. In this embodiment, the drill bit back rake angle used in the experiment is 15°, and the corresponding parameter is the ratio of the normal cutting force to the tangential cutting force on the cutting surface. is 0.60. The data identified in the model in this embodiment are shown in Table 1: Table 1 In the experimental data of this embodiment, the experimental results of white granite and yellow granite show the characteristics of stage I and stage II. The friction coefficient between the bottom of the drill bit and the rock can be identified by the slope of their tw curves in stage I. , denoted as According to the intercept of the dw and dt curves in stage II, the friction coefficient between the bottom of the drill bit and the rock can also be identified. , denoted as The identification results show that the white granite and Both are 1.01, yellow granite and This shows that the parameters identified based on the data of both Phase I and Phase II are For other types of rocks, since the feed pressure set in the experiment is always higher than the intercept of these rocks in stage I, only the data of stage II are obtained, but this does not affect the identification of parameters. This method can comprehensively evaluate the various interactions between the drill bit and the rock through a single drilling experiment.

[0027] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A method for determining multiple interactions between a PDC drill bit and a rock, characterized in that: The steps include: S1. Performing drilling experiments under different drilling settings to obtain drilling data under different drilling settings; S2. Based on the cutting, friction and indentation process between the drill bit and the rock, a mechanical model of drill bit-rock interaction is established; S3. Based on the drill bit-rock interaction mechanical model obtained in step S2, the drilling data obtained in step S1 are processed to obtain the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit under different drilling settings, and the cutting depth d, the normal force w per unit length of the drill bit, and the tangential force t per unit length of the drill bit are plotted in a dw diagram, a dt diagram, and a tw diagram. After the plotting is completed, linear fitting is performed on the data in the dw diagram, the dt diagram, and the tw diagram, respectively, to obtain the intercept and slope of each fitting curve; S4. Based on the drill bit-rock interaction mechanical model obtained in step S2, the intercept and slope of each fitting curve obtained in step S3 are interpreted to obtain various interaction parameters between the PDC drill bit and the rock.

2. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 1, characterized in that: The step S1 comprises: S101. Equipment and sample preparation: Check that the drilling rig, pressure control system and data logger are functioning properly, prepare rock samples, and ensure that the size and shape of the rock samples are suitable for the experimental requirements; S102. Initial setting: install the PDC drill bit on the drilling rig and ensure that the PDC drill bit is firmly fixed, place the PDC drill bit on the rock surface, start the pressure control system, set the feed pressure to the initial value, and ensure that the feed pressure is stable; S103. Start drilling: When the PDC drill bit stabilizes at the initial feed pressure value, the drilling process begins, and the PDC drill bit drills the rock sample at a constant speed; during the drilling process, the data recorder records the drilling data; S104. Pressure increase and drilling: After drilling for a period of time, the feed pressure value is increased and the drilling continues at a new stable feed pressure value, and the data recorder records the drilling data; S105 repeat the experiment: repeat step S104 until the maximum feed pressure value of the experimental design or the predetermined test time is reached to end the experiment, the data recorder records the drilling data at each stage; S106. Equipment shutdown and cleaning: shut down the drilling rig, pressure control system and data recorder, clean up the experimental site, and remove the PDC drill bit and rock samples.

3. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 2, characterized in that: In the step S1, the drilling data includes the thrust of the drill bit, the radius of the drill bit, the torque of the drill bit, the drilling speed of the drill bit and the rotation speed of the drill bit.

4. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 3, characterized in that: In step S2, the cutting, friction and pressing process between the drill bit and the rock includes stage I and stage II; In the first stage, the normal force w per unit length of the drill bit is less than the critical contact force. The relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in the first stage is shown in formula (1): （1） in, Indicates the friction angle between the bottom of the drill bit and the rock, Indicates the coefficient of friction between the bottom of the drill bit and the rock; The second stage is an effective drilling process. In the second stage, the normal force w per unit length of the drill bit is greater than the critical contact force, radial cracks in the rock begin to form, cracks propagating along a linear path are generated between the rock cuttings and the intact rock, the friction between the drill bit and the rock surface reaches the maximum value, and the contact force between the drill bit and the rock surface is equal to the sum of the pressing force and the critical contact force. The relationship between the normal force w per unit length of the drill bit and the cutting depth d of the drill bit in the second stage is shown in formula (2): （2） in, It indicates the contact force required to increase the unit cutting depth and is used to characterize the drillability of rock. It represents the ratio of normal cutting force to tangential cutting force on the cutting surface. Indicates the specific energy of rock, used to characterize the difficulty of cutting and crushing rock. represents the critical contact force, which is used to characterize the difficulty of the drill bit penetrating the rock surface. The relationship between the tangential force t per unit length of the drill bit and the cutting depth d of the drill bit in the second stage is shown in formula (3): （3） The relationship between the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit in the second stage is shown in formula (4): （4） in, The resistance coefficient of the effective drilling process is shown in formula (5): （5） The normal force w per unit length of the drill bit is as shown in formula (6): （6） in, Indicates the thrust of the drill bit, The radius of the drill bit, The tangential force t per unit length of the drill bit is as shown in formula (7): （7） in, Indicates the torque of the drill bit, The cutting depth d of the drill bit is as shown in formula (8): （8） in, Indicates the drilling speed of the drill bit. Indicates the speed of the drill bit.

5. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 4, characterized in that: In step S3, the drill bit thrust, drill bit radius, drill bit torque, drill bit drilling speed and drill bit rotation speed of the drilling data are input into the drill bit-rock interaction mechanical model obtained in step S2, and the cutting depth d of the drill bit, the normal force w per unit length of the drill bit and the tangential force t per unit length of the drill bit are obtained by formula (6) to formula (8).

6. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 4, characterized in that: The linear fitting of the data in the dw graph, dt graph and tw graph respectively in step S3 includes fitting the data in stage I in the tw graph and the data in stage II in the dw graph, dt graph and tw graph respectively, to obtain the fitting curve of stage I in the tw graph, the fitting curve of stage II in the dw graph, the fitting curve of stage II in the dt graph and the fitting curve of stage II in the tw graph.

7. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 6, characterized in that: The step S3 of obtaining the intercept and slope of each fitting curve includes respectively obtaining the slope of the fitting curve of the tw graph stage I, the intercept of the fitting curve of the dw graph stage II, the slope of the fitting curve of the dw graph stage II, the intercept of the fitting curve of the dt graph stage II, the slope of the fitting curve of the dt graph stage II, the intercept of the fitting curve of the tw graph stage II and the slope of the fitting curve of the tw graph stage II.

8. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 7, characterized in that: The various interaction parameters between the PDC drill bit and the rock in step S4 include the difficulty of the drill bit penetrating the rock surface, the friction coefficient between the bottom of the drill bit and the rock, the drillability of the rock, the specific energy of the rock and the resistance coefficient of the effective drilling process.

9. A method for determining multiple interactions between a PDC drill bit and a rock according to claim 8, characterized in that: In step S4, the friction coefficient between the bottom of the drill bit and the rock is determined by the inverse of the slope of the fitting curve of the stage I of the tw diagram or by dividing the intercept of the fitting curve of the stage II of the dt diagram by the intercept of the fitting curve of the stage II of the dw diagram, the difficulty of the drill bit penetrating the rock surface is determined by the intercept of the fitting curve of the stage II of the dw diagram, the specific energy of the rock is determined by the slope of the fitting curve of the stage II of the dt diagram, the resistance coefficient of the effective drilling process is determined by the inverse of the slope of the fitting curve of the stage II of the tw diagram, and the drillability of the rock is determined by subtracting the ratio of the normal cutting force to the tangential cutting force on the cutting surface and the specific energy of the rock from the slope of the fitting curve of the stage II of the dw diagram.

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