An integrated design method and system for a positive displacement motor and a PDC drill bit

Abstract

The present invention discloses an integrated design method and system for a volumetric motor and a PDC drill bit, including: obtaining the rock mechanical parameters of the target layer; establishing a three-dimensional cutting structure of the PDC drill bit; establishing a three-dimensional structure of the volumetric motor; calculating its output parameters according to the three-dimensional structure of the volumetric motor; establishing a drill bit-rock finite element model considering the volumetric motor; obtaining a drilling pressure torque time history curve based on the drill bit-rock finite element model; and establishing an integrated design scheme for the volumetric motor and the PDC drill bit based on the drilling pressure torque time history curve. By adopting the technical scheme of the present invention, the coupling influence mechanism of the cutting strategy, the number of volumetric motor heads, and the pitch of the volumetric motor on the rock breaking efficiency and stability of the PDC drill bit can be quantitatively obtained, avoiding high-cost engineering tests, and being able to improve the near-drilling stability under the premise of a small increase or minimum loss of the rock breaking efficiency of the PDC drill bit.

Description

Technical Field

[0001] The present invention belongs to the technical fields of oil field machinery, oil and gas well construction, and more particularly relates to an integrated design method and system for a positive displacement motor and a PDC drill bit. Background Art

[0002] At present, in practical engineering applications, it is often considered to add a positive displacement motor near the drill bit in composite drilling, which significantly improves the mechanical penetration rate. In engineering applications, the integrated design concept of positive displacement motor and PDC drill bit has gradually emerged. However, the cost of completing product iterative design through engineering experiments is too high, and the product manufacturing cycle is long. In existing theoretical studies, drill string dynamics has advantages in explaining the near-drill stick-slip phenomenon and drill string vibration characteristics of different drilling tool combinations, drilling parameters, and near-drill excitation (Liu W, Yang F, Zhu X, et al. Stick-slip vibration behaviors of BHA and its control method in highly-deviated wells [J]. Alexandria Engineering Journal, 2022 (No. 12): 9757-9767.), but there is little discussion on the improved design of near-drill rock breaking tools. For rock-breaking tools, the main considerations are the matching degree between the bit cutting structure and the formation (Kong L, Wang Z, Wang H, et al. Selection and Optimization Design of PDC Bits Based on FEMAnalysis for Drilling Long Horizontal Sections of Shale Formations [J]. Processes, 2023 (No. 2807): 2807.), the near-drilling parameters that the volumetric motor structure can output under certain hydraulic parameters and temperature environments (Li J, Tudor R, Ginzburg L, et al. Evaluation and Prediction of the Performance of Positive Displacement Motor (PDM) [J]. Journal of Canadian Petroleum Technology, 2001, 40 (05).) and the tolerance to the working environment. The above-mentioned practical and theoretical method studies have shown that the near-drilling mechanical characteristics will change due to the near-drilling end excitation and the bit structure, further affecting the rock-breaking efficiency and stability. This means that when implementing improved design research on rock breaking tools, it is necessary to consider the coupling effect between the drill bit and the screw. Studying the structure of the PDC drill bit or the volumetric motor alone is likely to lead to poor results in actual engineering applications. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an integrated design method and system for a volumetric motor and a PDC drill bit, which can quantitatively derive the coupling influence mechanism of the cutting strategy, the number of volumetric motor heads, and the volumetric motor pitch on the rock breaking efficiency and stability of the PDC drill bit, thereby avoiding high-cost engineering tests and improving the near-drilling stability under the premise of slightly improving or minimizing the rock breaking efficiency of the PDC drill bit.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method and system for integrated design of a positive displacement motor and a PDC drill bit, comprising the following steps:

[0006] Obtain the rock mechanical parameters of the target layer by conducting uniaxial and triaxial compressive strength tests on outcrops or underground cores;

[0007] Based on different cutting strategies, establish the three-dimensional cutting structure of PDC drill bit;

[0008] Establish the three-dimensional structure of the positive displacement motor based on different numbers of positive displacement motor heads and pitches of the positive displacement motor;

[0009] Calculate the output parameters of the positive displacement motor, including forward torque and forward speed, based on its three-dimensional structure;

[0010] Based on the rock mechanical parameters, the output parameters of the volumetric motor and the three-dimensional cutting structure of the PDC drill bit, a drill bit-rock finite element model considering the volumetric motor is established;

[0011] Based on the drill bit-rock finite element model, a time history curve of the bit pressure torque is obtained;

[0012] Based on the drilling pressure torque time history curve, an integrated design scheme of a positive displacement motor and a PDC drill bit is obtained.

[0013] Preferably, the rock mechanical parameters include: density ρ, elastic modulus E, Poisson's ratio μ, internal friction angle and cohesion c.

[0014] Preferably, establishing the three-dimensional cutting structure of the PDC drill bit comprises:

[0015] Select corresponding cutting teeth based on the drill bit cutting strategy, and assemble the cutting teeth in the circumferential direction according to the cutting strategy;

[0016] Based on the Archimedean spiral, the circumferential tooth arrangement benchmark of the spiral blade is controlled;

[0017] Based on the bit cutting strategy and the circumferential tooth arrangement reference of the spiral blade, the three-dimensional cutting structure of the PDC drill bit is established.

[0018] Preferably, establishing the three-dimensional structure of the positive displacement motor comprises:

[0019] Based on the number of positive displacement motor heads, the pitch of the positive displacement motor and the motor diameter, the assembly cross-section of the motor rotor and stator is obtained;

[0020] Based on the assembly cross-section of the rotor and the stator, the rotor and the stator with a predetermined lead are rotated and stretched to obtain a three-dimensional structure of the volumetric motor;

[0021] Preferably, the output parameters of the positive displacement motor are calculated according to its three-dimensional structure, including:

[0022] Based on the three-dimensional structure of the positive displacement motor, the flow area and the displacement per revolution are calculated;

[0023] Based on the flow area and the displacement per revolution, and according to the given working pressure difference and working displacement of the drilling project, the output forward speed and forward torque of the positive displacement motor are obtained.

[0024] Preferably, the boundary conditions of the drill bit-rock finite element model considering the volumetric motor include: mechanical rotation speed, near-drilling rotation speed, and positive torque output by the volumetric motor.

[0025] Preferably, based on the WOB torque time history curve, the integrated design scheme of the positive displacement motor and the PDC drill bit includes:

[0026] Performing statistical calculation on the stable cutting section of the WOB torque time history curve to obtain a WOB mean, a torque mean, a WOB standard deviation, and a torque standard deviation;

[0027] Obtaining mechanical specific energy based on the average drilling pressure and the average torque;

[0028] Based on the bit weight standard deviation and the torque standard deviation, obtaining the axial / circumferential vibration amplitude;

[0029] The triaxial compressive strength under the bottom hole liquid column pressure is used as the mechanical specific energy benchmark;

[0030] Based on the mechanical specific energy and the mechanical specific energy reference, obtaining a mechanical specific energy change rate;

[0031] Based on the axial / circumferential vibration amplitude and the mechanical specific energy change rate, an integrated design scheme of the volumetric motor and the PDC drill bit is obtained.

[0032] Preferably, the design parameters of the integrated design of the volumetric motor and PDC drill bit include: cutting tooth arrangement strategy, number of volumetric motor heads, and volumetric motor.

[0033] The present invention also provides an integrated design system of a volumetric motor and a PDC drill bit, comprising:

[0034] An acquisition module is used to obtain the rock mechanical parameters of the target layer by conducting a uniaxial and triaxial compressive strength test on the outcrop or downhole core;

[0035] PDC drill bit three-dimensional structure building module, used to build the three-dimensional cutting structure of the PDC drill bit based on the cutting strategy;

[0036] A three-dimensional structure building module for a positive displacement motor is used to build a three-dimensional structure of a positive displacement motor based on the number of positive displacement motor heads and the pitch of the positive displacement motor;

[0037] A volumetric motor output parameter module, used to obtain the positive speed and positive torque output by the volumetric motor based on the three-dimensional structure of the volumetric motor;

[0038] A model building module, for considering a drill bit-rock finite element model of a volumetric motor based on the rock mechanical parameters, the three-dimensional cutting structure of the PDC drill bit, and the forward speed and forward torque output by the volumetric motor;

[0039] A time history curve acquisition module, used for obtaining a time history curve of a bit pressure torque based on the drill bit-rock finite element model;

[0040] The design scheme establishing module is used to obtain an integrated design scheme of the volumetric motor and the PDC drill bit based on the drilling pressure torque time history curve.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention selects cutting teeth based on the cutting strategy to establish a three-dimensional cutting structure of the PDC drill bit, establishes a three-dimensional model of the volumetric motor based on the number of volumetric motor heads and the volumetric motor pitch, calculates the positive speed and positive torque output by the volumetric motor to the near-drill end based on the three-dimensional model of the volumetric motor, and establishes a drill bit-rock finite element model considering the volumetric motor based on the three-dimensional cutting structure of the PDC drill bit and the output parameters of the volumetric motor; obtains a drilling pressure torque time history curve based on the drill bit-rock finite element model; obtains an integrated design scheme of the volumetric motor and the PDC drill bit based on the drilling pressure torque time history curve. The problem of high cost of integrated design of positive displacement motor and PDC drill bit in engineering tests, lack of theoretical method for integrated design of positive displacement motor and PDC drill bit before drilling and insufficient understanding of the coupling influence of drill bit cutting strategy, number of motor rotor heads and motor pitch on rock breaking effect is solved. The present invention quantitatively obtains the coupling influence of cutting strategy, number of positive displacement motor heads and positive displacement motor pitch on rock breaking efficiency and stability, avoids high-cost and long-period engineering tests, and can improve near-drilling stability while maintaining or minimizing the loss of PDC drill bit rock breaking efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic flow chart of an integrated design method for a positive displacement motor and a PDC drill bit provided in an embodiment of the present invention;

[0044] Figure 2 A schematic diagram of the front and rear rows of teeth for a PDC drill bit;

[0045] Figure 3 Schematic diagram of the three-dimensional model of a positive displacement motor (taking the number of rotor heads N=3 as an example);

[0046] Figure 4 It is a schematic diagram of the positive torque and positive speed output of the positive displacement motor under different numbers of rotor heads and pitches of the positive displacement motor;

[0047] Figure 5 It is a stress cloud diagram of the drill bit-rock finite element model and a schematic diagram of the drilling pressure torque time history curve;

[0048] Figure 6 Schematic diagram of the influence of the number of positive displacement motors and the pitch of the positive displacement motor on the required drilling pressure WOB and ΔMSE of the drill bit;

[0049] Figure 7 It is a schematic diagram of the control effect of the number of positive displacement motor heads and the pitch of the positive displacement motor on the axial / circumferential vibration amplitude;

[0050] Figure 8 Schematic diagram of the influence of the number of positive displacement motor heads and the pitch of the positive displacement motor on the drill bit torque TOB;

[0051] Fig. 9 Schematic diagram of the influence of drill cutting strategy on ΔMSE;

[0052] Fig.10 Schematic diagram of the influence of the number of positive displacement motor heads and the pitch of the positive displacement motor on the required drilling pressure WOB, ΔMSE, drill torque TOB, SD WOB and SD TOB of the drill under a certain cutting strategy;

[0053] Fig.11 It is a schematic diagram of the design drawing of the PDC bit cutting structure and the volumetric motor when the cutting strategy is Type A;

[0054] Fig.12 It is a schematic diagram of the design drawing of the PDC bit cutting structure and the volumetric motor when the cutting strategy is Type B;

[0055] Fig.13 It is a schematic diagram of the design drawing of the PDC drill bit cutting structure and the volumetric motor when the cutting strategy is Type C;

[0056] Fig.14 It is a schematic diagram of the design drawing of the PDC bit cutting structure and the volumetric motor when the cutting strategy is Type D;

[0057] Description of the drawings: 1-front row teeth; 2-rear row teeth; 3-plane teeth; 4-V-shaped teeth; 5-ridge teeth; 6-conical teeth; 7-prismatic teeth. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] Embodiment 1:

[0061] like Figure 1 As shown, an embodiment of the present invention provides an integrated design method of a volumetric motor and a PDC drill bit, comprising the following steps:

[0062] Conduct uniaxial and triaxial compressive strength tests on the outcrops or downhole cores of the target strata to obtain rock mechanics parameters;

[0063] Furthermore, rock mechanical parameters include density ρ, elastic modulus E, Poisson's ratio μ, internal friction angle and cohesion c. The stress-equivalent plastic strain curve in the hardening stage is calculated and obtained according to the following formula;

[0064]

[0065] Where: true is the true stress; σ nom is the nominal stress; ε nom is the nominal strain; is the equivalent plastic strain; E is the elastic modulus;

[0066] Based on different cutting strategies, establish the three-dimensional cutting structure of PDC drill bit;

[0067] Further, the method for establishing the three-dimensional cutting structure of the PDC drill bit is:

[0068] Based on the proposed drill cutting strategy, the corresponding cutting teeth are selected. On the basis of completing the radial tooth arrangement, the cutting teeth are assembled in the circumferential direction according to the cutting strategy in combination with the Archimedean spiral. Figure 2 As shown in FIG. 1 , the assembled PDC bit cutting structure mainly includes front row teeth 1 and rear row teeth 2. The tooth shapes of the front row teeth 1 and rear row teeth 2 are adjusted according to the cutting strategy. Among them, the cutting strategy is classified according to the contact mode between the cutting tooth group and the target layer, which can be divided into "surface-to-surface" contact, "point-to-point" contact, plowing action, and a combination of various contact and action modes, such as a combination of "surface-to-surface" contact and "point-to-point" contact, and a combination of "surface-to-surface" contact and plowing action. Specific examples are shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] Establish the three-dimensional structure of the positive displacement motor based on different numbers of positive displacement motor heads and pitches of the positive displacement motor;

[0073] Specifically, based on the proposed number of positive displacement motor heads N and the positive displacement motor pitch h, the fixed motor diameter D PDM , according to the modified cycloid equations shown in equations (1)-(2), the assembly cross-section of the motor rotor and stator is given, and the rotor and stator with a certain lead are rotated and stretched based on the assembly cross-section of the rotor and stator. The lead length is calculated by equations (3)-(4). The rotor and stator are assembled with a certain eccentricity e. In this embodiment, e=98.85 / 2N (mm) and d=20mm are taken according to the actual engineering practice to complete the three-dimensional structure of the volumetric motor. Figure 3 shown.

[0074]

[0075] T s =(N+1)h (3)

[0076] T r =Nh (4)

[0077] Among them, x 2 is the horizontal coordinate value of any point on the cycloid; y 2 is the ordinate value of any point on the cycloid; r is the diameter of the rolling circle that forms the cycloid; θ is the angle between the x-axis and the line connecting the guide circle and the base circle required to form the cycloid; N is the number of positive displacement motor heads; T s is the stator lead; T r is the rotor lead; d is the normal offset of the original cycloid;

[0078] Calculate the output parameters of the positive displacement motor based on its three-dimensional structure;

[0079] Based on the three-dimensional structure of the volumetric motor, the flow area A is calculated by equations (5)-(6): F , displacement per revolution q;

[0080] A F =A N+1 -A N =2πe 2 (N-1)+4de (5)

[0081] q=A F ×N×T s =[2πe 2 (N-1)+4de]×N×(N+1)h×10 -6 (6)

[0082] Among them, A F A is the flow area of ​​the positive displacement motor; N+1 is the cross-sectional area of ​​the stator; A N is the cross-sectional area of ​​the rotor; q is the displacement per revolution of the positive displacement motor; e is the eccentricity of the rotor relative to the stator; N is the number of rotor heads; N+1 is the number of stator heads; Ts is the stator lead; d is the normal offset of the original cycloid;

[0083] Specifically, according to the law of conservation of volumetric mechanical energy, the mechanical energy J output by the motor per unit time is m Equal to the input hydraulic energy J w , the positive speed and positive torque output by the positive displacement motor can be derived, as shown in equations (7)-(8).

[0084]

[0085] M T =159.145×Δp×q (8)

[0086] Among them, J w is the hydraulic energy input to the positive displacement motor per unit time; J m is the mechanical energy output by the positive displacement motor per unit time; Δp is the screw working pressure difference; Q is the displacement of the drilling fluid pumped into the motor by the mud pump; ω T is the output angular velocity of the positive displacement motor; M T is the positive torque output by the positive displacement motor; n T is the forward speed output by the positive displacement motor; q is the displacement per revolution of the positive displacement motor;

[0087] In this embodiment, according to the engineering example, Q = 30L / s, Δp = 1.5MPa, the number of positive displacement motor heads N used in this study ranges from [3, 8] (dimensionless), the variable spacing is 1, the positive displacement pitch h ranges from [100, 200] (mm), the variable spacing is 20mm, and the calculation results are as follows Figure 4 shown.

[0088] Based on the rock mechanical parameters, the output parameters of the volumetric motor and the three-dimensional cutting structure of the PDC drill bit, a drill bit-rock finite element model considering the volumetric motor is established;

[0089] Furthermore, the boundary conditions of the drill bit-rock finite element model considering the volumetric motor are the mechanical penetration rate ROP, the near-drilling speed and the positive torque M output by the volumetric motor. T , the near-drilling speed is the superposition value of the top drive speed and the positive speed nT output by the positive displacement motor. The simulation scheme is an orthogonal design, as shown in Table 2 (Table 2 shows the cutting tooth combinations under different cutting strategies).

[0090] Table 2

[0091]

[0092] Based on the drill bit-rock finite element model, the drilling pressure torque time history curve is obtained, such as Figure 5 As shown;

[0093] Based on the drilling pressure torque time history curve, an integrated design scheme of a positive displacement motor and a PDC drill bit is established;

[0094] Further, based on the WOB torque time history curve, a method for establishing an integrated design scheme of a positive displacement motor and a PDC drill bit is as follows:

[0095] The stable cutting section of the WOB torque time history curve is statistically calculated to obtain the mean WOB, mean torque, standard deviation SD WOB and standard deviation SD TOB of the WOB;

[0096] Based on the mean WOB and the mean TOB, the mechanical specific energy (MSE) is obtained.

[0097] Based on the standard deviation of bit weight SD WOB and the standard deviation of torque SD TOB, the axial / circumferential vibration amplitude is obtained;

[0098] The triaxial compressive strength TCS under the bottom hole fluid column pressure bore , as a benchmark for mechanical specific energy;

[0099] Based on the mechanical specific energy and the mechanical specific energy benchmark, the mechanical specific energy change rate is obtained; the mechanical specific energy change rate ΔMSE is introduced to evaluate the rock breaking efficiency. When ΔMSE is positive, it means that the PDC drill bit under a certain design feature requires additional energy to break the rock. When ΔMSE is negative, it means that the PDC drill bit with a certain design feature reduces the energy required for rock breaking. As shown in equations (9)-(10).

[0100]

[0101] Wherein, MSE is mechanical specific energy; MeanWOB is the mean drilling pressure; RPM is the rotation speed per minute. The present invention combines engineering practice and the output forward rotation speed of the positive displacement motor to take (80+n T )r / min; Mean TOB is the mean torque; A b is the drill area, which can be taken as πD b 2 ;D b is the outer diameter of the drill bit. The actual diameter of the drill bit is 215.9 mm in this invention. ROP-mechanical rotation speed, m / h. The actual diameter of the drill bit is 11.25 m / h in this invention in combination with the actual project. b is the sliding friction coefficient of the drill bit; ΔMSE is the change ratio of mechanical specific energy; TCS bore is the triaxial compressive strength when the confining pressure is the bottom hole liquid column pressure, and the present invention takes 360.60 MPa according to experimental results.

[0102] Based on the axial / circumferential vibration amplitude and the mechanical specific energy change rate ΔMSE, combined with engineering practice, the integrated design scheme of the volumetric motor and PDC drill bit is obtained. (The mechanical specific energy change rate ΔMSE is used as the objective function)

[0103] As shown in Table 3 (Table 3 is the recommended design parameters for the integration of 215.9mm PDC drill bit and volumetric motor) and Fig.11 , Fig.12 , Fig.13 and Fig.14 As shown, the present invention provides a PDC drill bit cutting structure and a volumetric design scheme and design drawings with a mechanical specific energy change rate ΔMSE as the objective function according to different cutting strategies, which are obtained by the method in the above embodiment;

[0104] Table 3

[0105]

[0106] refer to Figure 6From the calculation and statistical results of WOB and ΔMSE, it can be seen that the larger the number of positive displacement motor heads, the required drilling pressure WOB and mechanical specific energy ΔMSE show a trend of first increasing and then decreasing-stabilizing. The value after the decrease is higher than and closest to the initial value N=3, but the larger the pitch of the positive displacement motor, the required drilling pressure and mechanical specific energy continue to increase. When the positive displacement motor outputs a higher forward torque (the lower the forward speed), in order to achieve a specific mechanical drilling speed, the increase in drilling pressure and energy required for rock breaking is certain.

[0107] refer to Figure 7 From the calculation and statistical results of SD WOB and SD TOB, it can be seen that when the number of positive displacement motor heads N ≥ 5 and the pitch of the positive displacement motor h ≥ 140 mm, the control ability of the positive displacement motor on vibration tends to be stable. Considering that the increase of the number of positive displacement motor heads and the pitch of the positive displacement motor (h>120 mm) may reduce the rock breaking efficiency, in order to take into account both the rock breaking efficiency and the life of the drill string, under general conditions, based on the vibration effect, N=5 and h=160 mm should be considered as the design parameters of the positive displacement motor.

[0108] refer to Figure 8 The calculation and statistical results of TOB show that when the pitch h of the positive displacement motor is adjusted with equal spacing, the output positive torque M T It may not be possible to completely overcome the increment of drill bit torque TOB caused by the change of volumetric motor output parameters; but when the number of heads is adjusted, the torque output by the screw can overcome part of the reverse torque increment. At this point, it is necessary to discuss: when h ≥ 140mm, the drill bit torque TOB decreases rapidly. Therefore, regardless of the number of heads N of the volumetric motor, based on the drill bit torque control effect, under general conditions, h ≥ 140mm should be considered as the volumetric motor pitch design parameter;

[0109] refer to Fig. 9 The calculation and statistical results of ΔMSE show that, compared with other cutting strategies, when the interaction mode between the cutting strategy and the rock is mainly in the special conditions of "surface-surface" contact and "point-point" contact (Type C), the PDC drill bit has higher rock breaking efficiency and better stability, so it should be considered when selecting the cutting strategy;

[0110] refer to Fig.10The calculation and statistical results of WOB, ΔMSE, TOB, SD WOB, and SD TOB show that when the cutting strategy is a combination of "face-to-face" contact and "point-to-point" contact (Type C), and when the interaction mode between the tooth layout strategy and the rock is mainly a combination of "face-to-face" contact and "point-to-point" contact (Type C), the drill bit has higher rock breaking efficiency and better stability. Therefore, it should be given priority consideration when selecting the cutting strategy. On this basis, when N=8 and h=140 / 200mm are used as the design parameters of the volumetric motor, the volumetric motor can minimize the loss of rock breaking efficiency while improving the axial / circumferential stability by 14.24-17.23% and 24.93-35.73% respectively. Therefore, N=8, h=140 / 200mm and cutting strategy Type C should be given priority consideration as the integrated design parameters of PDC drill bits and volumetric motors.

[0111] According to the above optimization principle, 3 and 4 in Table 3 are mainly used as reserve design solutions. The PDC bit cutting structure and volumetric motor are established with the help of computer 3D-aided modeling and the design drawings are output, such as Fig.13 As shown, the highly efficient and stable PDC drill bit and motor integrated design scheme (drill bit diameter 215.9 mm, volumetric motor diameter 197 mm) is obtained by optimizing the design method proposed in the present invention.

[0112] Embodiment 2:

[0113] The embodiment of the present invention further provides an integrated design system of a volumetric motor and a PDC drill bit, comprising:

[0114] An acquisition module is used to obtain the rock mechanical parameters of the target layer by conducting a uniaxial and triaxial compressive strength test on the outcrop or downhole core;

[0115] PDC drill bit three-dimensional structure building module, used to build the three-dimensional cutting structure of the PDC drill bit based on the cutting strategy;

[0116] A three-dimensional structure building module for a positive displacement motor is used to build a three-dimensional structure of a positive displacement motor based on the number of positive displacement motor heads and the pitch of the positive displacement motor;

[0117] A volumetric motor output parameter module, used to obtain the positive speed and positive torque output by the volumetric motor based on the three-dimensional structure of the volumetric motor;

[0118] A model building module, for considering a drill bit-rock finite element model of a volumetric motor based on the rock mechanical parameters, the three-dimensional cutting structure of the PDC drill bit, and the forward speed and forward torque output by the volumetric motor;

[0119] A time history curve acquisition module, used for obtaining a time history curve of a bit pressure torque based on the drill bit-rock finite element model;

[0120] The design scheme establishing module is used to obtain an integrated design scheme of the volumetric motor and the PDC drill bit based on the drilling pressure torque time history curve.

[0121] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An integrated design method for a volumetric motor and a PDC drill bit, characterized in that: The following steps are involved: Obtain rock mechanical parameters of target layer; Based on different cutting strategies, establish the three-dimensional cutting structure of PDC drill bit; Establish the three-dimensional structure of the positive displacement motor based on different numbers of positive displacement motor heads and pitches of the positive displacement motor; Calculate the output parameters of the positive displacement motor, including forward torque and forward speed, based on its three-dimensional structure; Based on the rock mechanical parameters, the output parameters of the volumetric motor and the three-dimensional cutting structure of the PDC drill bit, a drill bit-rock finite element model considering the volumetric motor is established; Based on the drill bit-rock finite element model, a time history curve of the bit pressure torque is obtained; Based on the drilling pressure torque time history curve, an integrated design scheme of a positive displacement motor and a PDC drill bit is obtained, which specifically includes: Performing statistical calculation on the stable cutting section of the WOB torque time history curve to obtain a WOB mean, a torque mean, a WOB standard deviation, and a torque standard deviation; Obtaining mechanical specific energy based on the average drilling pressure and the average torque; Based on the bit weight standard deviation and the torque standard deviation, obtaining the axial / circumferential vibration amplitude; The triaxial compressive strength under the bottom hole liquid column pressure is used as the mechanical specific energy benchmark; Based on the mechanical specific energy and the mechanical specific energy reference, obtaining a mechanical specific energy change rate; Based on the axial / circumferential vibration amplitude and the mechanical specific energy change rate, an integrated design scheme of the volumetric motor and the PDC drill bit is obtained.

2. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 1, characterized in that: The rock mechanics parameters include: density ρ, elastic modulus E, Poisson's ratio μ, internal friction angle φ and cohesion c.

3. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 2, characterized in that: Establishing the three-dimensional cutting structure of the PDC drill bit includes: Select corresponding cutting teeth based on the drill bit cutting strategy, and assemble the cutting teeth in the circumferential direction according to the cutting strategy; Based on the Archimedean spiral, the circumferential tooth arrangement benchmark of the spiral blade is controlled; Based on the bit cutting strategy and the circumferential tooth arrangement reference of the spiral blade, the three-dimensional cutting structure of the PDC drill bit is established.

4. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 3, characterized in that: Establishing the three-dimensional structure of the positive displacement motor includes: Based on the number of positive displacement motor heads, the pitch of the positive displacement motor and the motor diameter, the assembly cross-section of the motor rotor and stator is obtained; The rotor and the stator are rotated and stretched out based on the assembly cross-section of the rotor and the stator to obtain a three-dimensional structure of the volumetric motor.

5. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 4, characterized in that: The output parameters calculated based on the three-dimensional structure of the positive displacement motor include: Based on the three-dimensional structure of the positive displacement motor, the flow area and the displacement per revolution are calculated; Based on the flow area and the displacement per revolution, and according to the given working pressure difference and working displacement of the drilling project, the output forward speed and forward torque of the positive displacement motor are obtained.

6. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 5, characterized in that: The boundary conditions of the drill bit-rock finite element model considering the volumetric motor include: mechanical speed, near-drilling speed, and positive torque output by the volumetric motor.

7. The integrated design method of a positive displacement motor and a PDC drill bit according to claim 6, characterized in that: The design parameters of the integrated design of the volumetric motor and PDC drill bit include: cutting tooth arrangement strategy, the number of volumetric motor heads, and the volumetric motor.

8. An integrated design system for a volumetric motor and a PDC drill bit that implements the integrated design method for a volumetric motor and a PDC drill bit according to any one of claims 1 to 7, characterized in that: include: An acquisition module is used to obtain the rock mechanical parameters of the target layer; PDC drill bit three-dimensional structure building module, used to build the three-dimensional cutting structure of the PDC drill bit based on the cutting strategy; A three-dimensional structure building module for a positive displacement motor is used to build a three-dimensional structure of a positive displacement motor based on the number of positive displacement motor heads and the pitch of the positive displacement motor; A volumetric motor output parameter module, used to obtain the positive speed and positive torque output by the volumetric motor based on the three-dimensional structure of the volumetric motor; A model building module, for considering a drill bit-rock finite element model of a volumetric motor based on the rock mechanical parameters, the three-dimensional cutting structure of the PDC drill bit, and the forward speed and forward torque output by the volumetric motor; A time history curve acquisition module, used for obtaining a time history curve of a bit pressure torque based on the drill bit-rock finite element model; The design scheme establishing module is used to obtain an integrated design scheme of the volumetric motor and the PDC drill bit based on the drilling pressure torque time history curve.

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