A reciprocating rotary bidirectional drill bit and method for drilling in soft clay formations

Abstract

The reciprocating rotary bidirectional drill bit suitable for soft mudstone layer drilling of the application uniformly sets three wing groove on the drill bit body, and designs the cutting wing as a crown structure, which forms a bidirectional drill bit with both ends being tapered when combined together, so as to ensure the stability and accuracy of the guidance in the drilling process and prevent the drill bit from deviating from the preset drilling track. The cutting teeth on the cutting wing can effectively cut the rock layer when the drill bit is pulled out in the reverse direction, thereby reducing the risk of drill bit burying caused by soft rock layer hole collapse. Meanwhile, the waist hole design is adopted for the drainage groove, which has the advantages of large water discharge, small water pressure shot to the hole wall, large flushing area and the like, so that the powder discharge is more smooth, and the risk of drill bit sticking is reduced.

Description

Technical Field

[0001] This invention belongs to the field of drilling equipment and tools, and specifically relates to a reciprocating rotary bidirectional drill bit and method suitable for drilling soft mud rock formations. Background Technology

[0002] Soft mudstone is a type of mudstone with plastic creep characteristics. This type of rock formation is characterized by low strength, environmental sensitivity, and high hydration swelling, making it highly susceptible to hole shrinkage, collapse, and stuck drill bits. The creep properties of soft mudstone further increase the difficulty of maintaining borehole stability and maintenance during drilling. Soft mudstone formations often have high clay content and strong water dispersion capabilities. As drilling fluid continuously flows in, the viscosity and shear stress of the drilling fluid increase. Simultaneously, the hydration of soft mudstone easily leads to the adsorption of large amounts of mud solids onto the drill bit surface, forming mud pockets. This mud pockets can cause stuck drill bits, affecting drilling fluid flow and borehole cleaning operations, and making geological exploration and tunneling work more difficult and complex.

[0003] Mudstone formations have low strength and hardness, allowing for rock cutting with relatively low axial pressure. However, at greater depths and faster drilling speeds, while the rock cuttings are large, they easily disperse into smaller particles, necessitating careful consideration of cutting efficiency during drilling. These formations also exhibit high cohesion, leading to problems such as drill bit jamming or swelling upon contact with water. Existing drill bits for this type of mudstone formation cannot achieve bidirectional rotary cutting; furthermore, poor cutting efficiency easily causes the drill bit to become stuck. Summary of the Invention

[0004] The purpose of this invention is to provide a reciprocating rotary bidirectional drill bit and method suitable for drilling soft mudstone formations, in order to solve the problems in the prior art where drill bits cannot achieve bidirectional rotary cutting and poor powder removal leads to stuck drill bits when dealing with soft mudstone formations.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A reciprocating rotary bidirectional drill bit for drilling soft mudstone formations includes a cylindrical drill bit body, the head of which serves as the connection end with an external device; the tail of the drill bit body is the drainage end, and the tail is provided with a rounded chamfer.

[0007] The sidewall of the drainage end is uniformly provided with multiple through waist-shaped drainage grooves along the circumference; the drill body is provided with three through blade grooves along the circumference, and the blade grooves extend along the drill axis; the starting point of all the blade grooves is on the same plane as the starting point of the chamfer arc of the drainage end of the drill body; a cutting blade is fixedly installed in each blade groove, and the tail end of the cutting blade extends out of the drainage end of the drill body and does not contact the drainage groove.

[0008] The cutting blade has a crown-shaped structure, and the inclination angle of the head of the cutting blade is smaller than the inclination angle of the tail side; multiple mounting slots are arranged sequentially along the axial direction of the drill body on the end face of the cutting blade away from the drill body, and a square columnar cutting tooth is installed in each mounting slot.

[0009] The present invention also has the following features:

[0010] Furthermore, a central column is coaxially arranged inside the drill bit body, and the lower ends of all the cutting blades enter the drill bit body and are fixedly connected to the central column.

[0011] The inclination angle of the head of the cutting blade is 18° to 20°; the inclination angle of the tail of the cutting blade is 0° to 38°.

[0012] Furthermore, the number of drainage grooves is 6, with two drainage grooves provided between each pair of adjacent cutting blades.

[0013] Furthermore, the connecting end of the drill bit body is coaxially provided with a threaded groove with an internal thread.

[0014] The minimum distance between the threaded groove and the cutting blade is not less than 15mm, and the maximum distance is not greater than 25mm.

[0015] Furthermore, the drill bit body is made of 42CrMoA high-quality medium carbon alloy steel; the cutting teeth are made of YG8 cemented carbide; and the cutting teeth have a size of 4mm*10mm*2mm.

[0016] A design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations, the method comprising the following steps:

[0017] Step a: Design the drill bit body specifications according to actual usage requirements;

[0018] Step b: Design three wing grooves evenly along the circumference on the drill bit body; design a threaded groove with internal threads on the connecting end of the drill bit body that is coaxially connected to the drill bit body.

[0019] Step c: Determine the geometric parameters of each cutting tooth, and determine the normal angle, rake angle and yaw angle of the corresponding cutting tooth based on the geometric parameters of each cutting tooth; establish a CAD model of the cutting tooth arrangement based on the normal angle, rake angle and yaw angle of each cutting tooth.

[0020] Step d: Design the specifications of the cutting blade and, based on the CAD model of the cutting tooth arrangement, design mounting slots on the cutting blade that correspond one-to-one with each cutting tooth.

[0021] Step e: Design multiple through-holes evenly along the circumference at the drainage end of the drill bit body.

[0022] Step f: Establish a three-dimensional model of the reciprocating rotary bidirectional drill bit for drilling soft mudstone strata, and complete the manufacturing and assembly based on the three-dimensional model.

[0023] Furthermore, in step a,

[0024] The drainage trough meets the following conditions:

[0025] Let the diameter of the drill bit body be D, the width of the drainage groove be H = 1 / 4D, and the length of the drainage groove be L = 3 / 4H.

[0026] Furthermore, step c includes the following sub-steps:

[0027] Step c0: Randomly select a cutting tooth as the current cutting tooth.

[0028] Step c1: Determine the geometric parameters of the initial working plane of the current cutting tooth.

[0029] The cutting surfaces of all cutting teeth on the rock are taken as the initial working plane, and this plane is used as the original starting plane for orthogonal transformation.

[0030] Assume that the normal angle, roll angle, and backslope angle of the initial working plane are all zero degrees, and establish the rotation axes of these three directions: the normal axis, the roll axis, and the backslope axis, respectively.

[0031] The intersection of one corner of the current cutting tooth and the cutting blade is taken as the center coordinate O.

[0032] Let the normal axis direction vector of the current cutting tooth be... Lateral axis direction vector is The direction vector of the backslope axis is The external normal vector of the working plane is

[0033] The initial working plane vector parameters are as follows:

[0034] O(0, 0, 0).

[0035] The normal axis direction vector is (0, 1, 0).

[0036] Lateral axis direction vector is (1, 0, 0).

[0037] The direction vector of the backslope axis is (0, 0, 1).

[0038] The outer normal vector is (0, 1, 0).

[0039] Step c2: Determine the orthogonal transformation matrices for the current cutting teeth to rotate around the standard X, Y, and Z axes;

[0040] The orthogonal transformation matrix for the rotation of the cutting teeth about the positive X-axis is:

[0041]

[0042] Where, θ X The angle of rotation of the cutting teeth around the X-axis.

[0043] The orthogonal transformation matrix of the cutting teeth about the Y-axis is:

[0044]

[0045] Where, θ y The angle at which the cutting teeth rotate around the Y-axis.

[0046] The orthogonal transformation matrix of the cutting teeth about the Z-axis is:

[0047]

[0048] Where, θ z The angle at which the cutting teeth rotate around the Z-axis.

[0049] Step c3: Determine the geometric parameter expression for the rotation of the current cutting tooth around the actual axis;

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] in:

[0056] This represents the rotation matrix.

[0057] T represents a rotation transformation of a point or vector in space.

[0058] This represents the rotation vector.

[0059] This indicates the angle of rotation about the axis of rotation.

[0060] (x,y,z) represents a point or vector in space.

[0061] (x',y',z') represents the coordinates or vectors of a point after the rotation transformation.

[0062] It represents the coordinates or vectors of a point on the cutting tooth that rotates around a standard coordinate axis.

[0063] This represents the coordinates or vector of the cutting tooth after it has been rotated around any axis.

[0064] Γ represents the rotating unit vector.

[0065] and The formula for the rotation angle is given.

[0066] Step c4: Obtain the geometric parameter expression of the normal axis of the current cutting tooth.

[0067] The normal axis vector of the cutting teeth, after n orthogonal transformations, can be expressed in linear form as follows:

[0068]

[0069] n represents the number of orthogonal transformations.

[0070] This represents the initial vector in the normal axis direction of the cutting teeth.

[0071] This represents the vector of the normal axis of the cutting teeth after n transformations.

[0072] T n Indicates to Perform n orthogonal transformations.

[0073] Step c5: Determine the geometric parameter expressions for the current cutting tooth's back tilt axis and side tilt axis.

[0074] After the initial working plane center coordinates O are translated by d from the origin (0, 0, 0), the center coordinates become O(0, 0, d). The coordinates of the cutting teeth change after the initial working plane translation, but the axis of rotation remains unchanged. Taking the origin as the reference point, d = 0. The linear transformation forms of points Q and O after the transformation are as follows:

[0075]

[0076] The initial working surface is rotated about the Y-axis, and the rotation angle is γ1. The normal vector of the working surface after rotation is... and the corresponding roll axis Expressed using linear transformation and transformation matrices respectively:

[0077]

[0078]

[0079] Initial working face around the tilt axis Rotation, assuming the rotation angle is γ2, the normal vector of the corresponding working plane is... Similarly, the lean angle at this time is Its linear transformation form is as follows:

[0080]

[0081] Initial working face around the back tilt axis Rotation, assuming the rotation angle is γ3, the normal vector of the corresponding working plane is... Its linear transformation form is as follows:

[0082]

[0083] The initial working surface is rotated about the Z-axis, and the axial azimuth angle is rotated by γ. The corresponding external normal vector of the working plane is... The corresponding O and Q points are Q4 and O4, respectively, and their linear transformation forms are as follows:

[0084]

[0085] T1 represents an orthogonal transformation, where the initial working surface is rotated around the Y-axis, and the normal vector coordinates are the values ​​corresponding to the rotation angle γ1.

[0086] T2 represents a second orthogonal transformation, where the initial working face is rotated around the tilt axis. Rotation, the coordinates of the normal vector when the rotation angle is γ2.

[0087] T3 represents a third orthogonal transformation, with the initial working face revolving around the backslope axis. Rotation, the coordinates of the normal vector when the rotation angle is γ3.

[0088] T4 represents the fourth orthogonal transformation, the coordinate value of the normal vector when the initial working surface is rotated around the Z-axis and the axial azimuth angle is rotated by γ.

[0089] Step c6: Determine the normal angle, back rake angle, and side rake angle of the cutting tooth;

[0090] The results of steps c1 to c5—the geometric parameters of the initial working plane of the current cutting tooth, the orthogonal transformation matrix of the current cutting tooth rotating around the standard X, Y, and Z axes, the geometric parameter expression of the current cutting tooth rotating around the actual axis, the geometric parameter expression of the normal axis of the current cutting tooth, and the geometric parameter expressions of the back tilt axis and side tilt axis of the current cutting tooth—are all input into Matlab. Matlab will then automatically calculate and obtain the normal angle, back tilt angle, and side tilt angle of the cutting tooth.

[0091] Step c7: Select a cutting tooth that has not yet been calculated, and repeat steps c1 to c6.

[0092] Step c8, repeat step c7, until all cutting teeth have been traversed.

[0093] Step c9: Create a CAD model of all cutting teeth arrangement.

[0094] Further, step d includes:

[0095] Step d1: Select the guiding capability level, outer cone height, and inner cone height of the reciprocating rotary bidirectional drill bit for drilling soft mudstone strata according to the drill bit crown profile classification.

[0096] For drilling in soft mudstone formations, select level 3 for the guiding capability of the reciprocating rotary bidirectional drill bit, and select level 2 for the crown profile grading of the cutting blades.

[0097] The outer cone height of the cutting blade is 3 / 4 of the drill bit body, and the inner cone height of the cutting blade is 1 / 10 of the drill bit body diameter.

[0098] Step d2: Based on the CAD model of the cutting tooth arrangement, design mounting slots on the cutting blade that correspond one-to-one with each cutting tooth.

[0099] Further, step f includes:

[0100] Step f1: Establish a three-dimensional model of the entire reciprocating rotary bidirectional drill bit for drilling soft mudstone strata.

[0101] Step f2 involves using a laser cutting machine and a DMG five-axis machining center to process each component, and then using brazing and MIG welding to weld the components together to complete the overall processing.

[0102] Compared with the prior art, the present invention has the following technical effects:

[0103] (I) The present invention relates to a reciprocating rotary bidirectional drill bit suitable for drilling soft mud rock formations. Three blade grooves are evenly arranged on the drill bit body, and the cutting blades are designed with a crown-like structure. When combined, they form a bidirectional drill bit with conical ends, ensuring the stability and accuracy of guidance during drilling and preventing deviation from the preset drilling trajectory. The cutting teeth on the cutting blades can effectively cut the rock formation when the drill is pulled back in the opposite direction, reducing the risk of borehole collapse and burying in soft rock formations. Simultaneously, the drainage groove adopts a waist-shaped hole design, which has advantages such as large water output, low water pressure hitting the borehole wall, and a large scouring area, making powder removal smoother and reducing the risk of stuck drill.

[0104] (II) The present invention relates to a manufacturing method for a reciprocating rotary bidirectional drill bit applicable to drilling in soft mud rock formations. In the established coordinate system, the working plane of each cutting tooth is set as the result of a certain rigid movement from a specific position. The arrangement of the cutting teeth is determined by orthogonal exchange method. Matlab software is used to complete the calculation, and the spatial angle of each cutting tooth is calculated by iterative calculation and optimization method. The center coordinates of the working plane of the cutting tooth, the axial azimuth angle and the cutting tooth model are obtained. An interaction model between the bidirectional drill bit and the rock is established. A CAD model of the cutting tooth arrangement is established in UG. Finally, the cutting and assembly are carried out according to the model. It has high reliability and is suitable for large-scale industrial use and promotion. Attached Figure Description

[0105] Figure 1 This is a schematic diagram of the overall structure of the reciprocating rotary bidirectional drill bit for drilling soft mudstone formations according to the present invention;

[0106] Figure 2 This is a schematic diagram of the reciprocating rotary bidirectional drill bit for drilling soft mudstone formations of the present invention from another angle;

[0107] Figure 3 This is a schematic diagram of the drill bit body structure of the present invention;

[0108] Figure 4 This is a schematic diagram of the drainage channel structure of the present invention;

[0109] Figure 5 It is the cutting blade of the present invention;

[0110] Figure 6 This is a schematic diagram of the initial working plane of the cutting teeth of the present invention;

[0111] Figure 7 This is the trajectory model of the cutting teeth during the drilling process of the present invention;

[0112] Figure 8 This is a schematic diagram of the reciprocating rotary bidirectional drill bit drilling operation in soft mudstone formations according to the present invention;

[0113] Figure 9 This is a schematic diagram of the reciprocating rotary bidirectional drill bit retraction operation for drilling soft mudstone formations according to the present invention;

[0114] Figure 10 This is a schematic diagram of the on-site operation of the reciprocating rotary bidirectional drill bit for drilling soft mudstone formations according to the present invention.

[0115] The meanings of the labels in the diagram are as follows:

[0116] 1. Drill body; 2. Drainage groove; 3. Blade groove; 4. Cutting blade; 5. Cutting teeth; 6. Center post; 7. Thread groove. Detailed Implementation

[0117] It should be noted that, unless otherwise specified, all components in this invention are known in the prior art. For example, the central column is a commonly used central column.

[0118] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0119] like Figures 1 to 4 As shown, a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations includes a cylindrical drill bit body 1, the head of the drill bit body 1 serving as the connection end with an external device; the tail of the drill bit body 1 is the drainage end, and the tail is provided with a rounded chamfer.

[0120] Multiple through waist-shaped drainage grooves 2 are evenly provided on the side wall of the drainage end along the circumference; three through blade grooves 3 are provided on the drill body 1 along the circumference, and the blade grooves 3 extend along the axial direction of the drill body 1; the starting point of all blade grooves 3 is on the same plane as the starting point of the chamfer arc of the drainage end of the drill body 1; a cutting blade 4 is fixedly installed in each blade groove 3, and the tail end of the cutting blade 4 extends out of the drainage end of the drill body 1 and does not contact the drainage groove 2.

[0121] The cutting blade 4 has a crown-shaped structure, and the inclination angle of the head of the cutting blade 4 is smaller than the inclination angle of the tail side. Multiple mounting slots are arranged sequentially along the axial direction of the drill body 1 on the end face of the cutting blade 4 away from the drill body 1, and a square columnar cutting tooth 5 is installed in each mounting slot.

[0122] like Figure 5 As shown, the cutting blade 4 has a crown-shaped structure, and the inclination angle of the head of the cutting blade 4 is smaller than the inclination angle on one side of the tail. Multiple square columnar cutting teeth 5 are arranged sequentially on the upper end face of the cutting blade 4 along the axial direction of the drill body 2.

[0123] Three blade grooves 3 are evenly arranged on the drill bit body 2, and the cutting blades 4 are designed with a crown-shaped structure. When combined, they form a bidirectional drill bit with tapered ends, ensuring the stability and accuracy of guidance during drilling and preventing deviation from the preset drilling trajectory. The cutting teeth 5 on the cutting blades 4 can effectively cut the rock strata when the drill is pulled back in the opposite direction, reducing the risk of the drill getting stuck in soft rock formations. At the same time, the drainage groove 4 adopts a waist-shaped hole design, which has advantages such as large water output, low water pressure hitting the hole wall, and large scouring area, making powder removal smoother and reducing the risk of the drill getting stuck.

[0124] Specifically, there are 6 drainage grooves 2, with two drainage grooves 2 provided between each pair of adjacent cutting blades 4.

[0125] The drill body 2 is made of 42CrMoA high-quality medium carbon alloy steel; the cutting teeth 5 are made of YG8 cemented carbide; the cutting teeth 5 have a size of 4mm*10mm*2mm.

[0126] As a preferred embodiment, a central column 6 is coaxially arranged inside the drill bit body 2, and the lower ends of all cutting blades 4 enter the drill bit body 2 and are fixedly connected to the central column 6.

[0127] The tilt angle of the head of the cutting blade 4 is 18° to 20°; the tilt angle of the tail of the cutting blade 4 is 0° to 38°.

[0128] The central column 6 acts as a buffer for the water flow and also strengthens the connection of the cutting blades 4.

[0129] As a preferred embodiment, the connecting end of the drill bit body 2 is coaxially provided with a threaded groove 7 with an internal thread, and is connected to an external device through the threaded groove 7.

[0130] The minimum distance between the threaded groove 7 and the cutting blade 4 is not less than 15mm and the maximum distance is not greater than 25mm, which facilitates subsequent welding operations.

[0131] It should be noted that the three cutting blades 4 are evenly welded to the machined drill body 2 in the circumferential direction. At the same time, a central column 6 is set at the center of the drill body 2 and the welding point of the cutting blades 4 to prevent high-pressure water from directly impacting the borehole wall and damaging the stability of the borehole wall.

[0132] Considering the tendency of soft rock layers to form mud pockets, a blade-type tooth arrangement is adopted. This facilitates the cleaning of the cutting teeth and chip removal by the drilling fluid during drilling. Therefore, carbide sheets are brazed to the forward rotating cutting side of the blades. At the same time, considering the need for efficient and effective powder removal, six waist-shaped drainage grooves 2 are now machined at the top of the drill bit body 2. The number and size of the drainage grooves 2 can be adjusted according to actual needs.

[0133] A design method for a reciprocating rotary bidirectional drill bit suitable for drilling in soft mudstone formations, the method being used in the aforementioned reciprocating rotary bidirectional drill bit for drilling in soft mudstone formations, characterized by comprising the following steps:

[0134] Step a, design the specifications of drill body 1 according to actual usage requirements;

[0135] Step b: Design three blade grooves 3 evenly along the circumference on the drill body 1; design a threaded groove 7 with internal threads on the connecting end of the drill body 1, which is coaxially connected to the drill body 1.

[0136] Step c: Determine the geometric parameters of each cutting tooth 5, and determine the normal angle, back rake angle and side rake angle of the corresponding cutting tooth 5 based on the geometric parameters of each cutting tooth 5; establish a CAD model of the arrangement of cutting teeth 5 based on the normal angle, back rake angle and side rake angle of each cutting tooth 5.

[0137] Step d: Design the specifications for the cutting blade 4;

[0138] Step e: Design multiple through drainage grooves 2 evenly along the circumference at the drainage end of the drill bit body 1.

[0139] Step f: Output the 3D model of the drill bit, and complete the manufacturing and assembly of the components based on the 3D model.

[0140] Specifically, in step a, the drainage trough 2 satisfies the following conditions:

[0141] Let the outer diameter of the drill bit body 2 be D, the width of the drainage groove 2 be H = 1 / 4D, and the length of the drainage groove 2 be L = 3 / 4H; the included angle between the centers of two adjacent drainage grooves 2 is 25°.

[0142] Furthermore, step c includes the following sub-steps:

[0143] Since the spatial orientation parameters are determined by the degrees of freedom of the bidirectional drill bit, they mainly include three parameters: backslope angle, normal angle, and sideslope angle. First, a drilling coordinate system is established, with the assumed drill bit center axis as the central axis Z-axis. A global coordinate system OXYZ is established according to the right-hand rule. When the drill bit speed is zero, the drill bit rotates around the central axis Z-axis once, and the intersection line of the cutting edge of each cutting tooth with the XOZ plane is taken as the axial profile line of the cutting tooth.

[0144] In the established coordinate system, the working plane of each cutting tooth 5 is assumed to be obtained after a certain rigid movement from a specific position. The actual working surface is obtained by each cutting tooth 5 through orthogonal transformation of the same initial working plane.

[0145] Step c0: Select a cutting tooth 5 as the current cutting tooth;

[0146] Step c1: Determine the geometric parameters of the initial working plane of the current cutting tooth 5;

[0147] Take the cutting surfaces of all five cutting teeth on the rock as the initial working plane, and use this plane as the original starting plane for orthogonal transformation;

[0148] Assume that the normal angle, roll angle, and backslope angle of the initial working plane are all zero degrees, and establish the rotation axes for these three directions: the normal axis, the roll axis, and the backslope axis, respectively.

[0149] The intersection of one corner of the current cutting tooth 5 and the cutting blade 4 is taken as the center coordinate O;

[0150] Let the normal axis direction vector of the current cutting tooth 5 be... Lateral axis direction vector is The direction vector of the backslope axis is The external normal vector of the working plane is

[0151] The initial working plane vector parameters are as follows:

[0152] O(0, 0, 0);

[0153] The normal axis direction vector is (0, 1, 0);

[0154] Lateral axis direction vector is (1, 0, 0);

[0155] The direction vector of the backslope axis is (0, 0, 1);

[0156] The outer normal vector is (0, 1, 0);

[0157] Step c2: Determine the orthogonal transformation matrix of the current cutting tooth 5 rotating around the standard X, Y, and Z axes;

[0158] The orthogonal transformation matrix for the rotation of cutting tooth 5 around the positive X-axis is:

[0159]

[0160] Where, θ X The angle by which cutting tooth 5 rotates around the X-axis;

[0161] The orthogonal transformation matrix of cutting tooth 5 about the Y-axis is:

[0162]

[0163] Where, θ y The angle by which cutting tooth 5 rotates around the Y-axis;

[0164] The orthogonal transformation matrix of cutting tooth 5 around the Z-axis is:

[0165]

[0166] Where, θ z The angle of rotation of cutting tooth 5 around the Z-axis;

[0167] Step c3: Determine the geometric parameter expression for the rotation of the current cutting tooth 5 around the actual axis;

[0168] When calculating the rotation transformation of cutting tooth 5 around the actual axis, the actual axis is first transformed by translation, and then rotated around the corresponding standard coordinate axis until it coincides with the corresponding standard coordinate axis.

[0169] The rotation vector is obtained by multiplying the unit vector by the rotation angle, as shown in the following formula:

[0170]

[0171]

[0172]

[0173]

[0174]

[0175] Represents the rotation matrix;

[0176] T represents a rotational transformation of a point or vector in space;

[0177] Represents the rotation vector;

[0178] Indicates the angle of rotation about the axis of rotation;

[0179] (x,y,z) represents a point or vector in space;

[0180] (x',y',z') represents the coordinates or vector of a point after the rotation transformation;

[0181] This represents the coordinates or vectors of a point on the cutting tooth 5 that rotates around a standard coordinate axis.

[0182] This represents the coordinates or vector of the cutting tooth 5 after it has been rotated around any axis;

[0183] Γ represents the rotating unit vector;

[0184] and Formula for rotation angle;

[0185] Step c4: Obtain the geometric parameter expression of the normal axis of the current cutting tooth 5;

[0186] The normal axis vector of cutting tooth 5, after n orthogonal transformations, can be expressed in linear form as follows:

[0187]

[0188] n represents the number of orthogonal transformations;

[0189] This represents the initial vector of the cutting tooth 5 along its normal axis.

[0190] This represents the vector of the normal axis of cutting tooth 5 after n transformations.

[0191] T n Indicates to Perform n orthogonal transformations;

[0192] Step c5: Determine the geometric parameter expressions for the tilt axis and lateral tilt axis of the current cutting tooth 5;

[0193] After the initial working plane center coordinates O are translated by d from the origin (0, 0, 0), the center coordinates become O(0, 0, d). The coordinates of the cutting tooth 5 change after the initial working plane translation, but the axis of rotation remains unchanged. Taking the origin as the reference point, d = 0. The linear transformation forms of the transformed points Q and O are as follows:

[0194]

[0195] The initial working surface is rotated about the Y-axis, and the rotation angle is γ1. The normal vector of the working surface after rotation is... and the corresponding roll axis Expressed using linear transformation and transformation matrices respectively:

[0196]

[0197]

[0198] Initial working face around the tilt axis Rotation, assuming the rotation angle is γ2, the normal vector of the corresponding working plane is... Similarly, the lean angle at this time is Its linear transformation form is as follows:

[0199]

[0200] Initial working face around the back tilt axis Rotation, assuming the rotation angle is γ3, the normal vector of the corresponding working plane is... Its variations are as follows:

[0201]

[0202] The initial working surface is rotated about the Z-axis, and the axial azimuth angle is rotated by γ. The corresponding external normal vector of the working plane is:

[0203]

[0204] T1 represents the first orthogonal transformation, the initial working surface rotates around the Y-axis, and the normal vector coordinate value is the corresponding normal vector coordinate value when the rotation angle is γ1.

[0205] T2 represents the second orthogonal transformation, where the initial working face is rotated around the tilt axis. Rotation, the coordinates of the normal vector when the rotation angle is γ2;

[0206] T3 represents the third orthogonal transformation, where the initial working face is rotated around the backslope axis. Rotation, the coordinates of the normal vector when the rotation angle is γ3;

[0207] T4 represents the fourth orthogonal transformation, the coordinate value of the normal vector when the initial working surface is rotated around the Z-axis and the axial azimuth angle is rotated by γ.

[0208] Step c6: Determine the normal angle, back rake angle, and side rake angle of the cutting tooth 5;

[0209] Input the results of steps c1 to c5 into Matlab in sequence. Matlab will automatically calculate and obtain the normal angle, back rake angle and side rake angle of the cutting tooth 5.

[0210] Step c7: Select a cutting tooth 5 that has not yet been calculated, and repeat steps c1 to c6.

[0211] Step c8, repeat step c7, until all cutting teeth 5 have been traversed;

[0212] Step c9: Create a CAD model of all cutting teeth arranged in 5 rows in UGNX.

[0213] Further, step d includes the following steps:

[0214] The selection of the outer and inner cone values ​​of the bidirectional drill bit is related to the diameter D of the drill bit. In order to ensure a certain guiding effect during drilling, according to the drill bit crown profile classification table in Table 1, the guiding capacity of the reciprocating rotary bidirectional drill bit for drilling soft mud rock is selected. In order to ensure a good guiding effect during drilling, the corresponding relationship table between the drill bit crown profile classification and the guiding capacity classification is shown in the table. The guiding capacity of the reciprocating rotary bidirectional drill bit for drilling soft mud rock is level 3.

[0215] Table 1. Drill Bit Crown Profile Classification

[0216]

[0217] Table 2. Correspondence between contour grading and guidance capability grading

[0218]

[0219]

[0220] Based on Table 2 and data simulation analysis, the outer cone height is 3 / 4 of the diameter of the bidirectional drill bit, and the inner cone height is 1 / 10 of the diameter of the bidirectional drill bit.

[0221] Furthermore, during the drilling process, in order to improve the free cutting surface of the rock strata and reduce drilling resistance, the cutting blade 4 is designed as a bidirectional cone. Its length is determined according to the total length of the drill bit body 2. That is, the cutting operation point of the bidirectional drill bit is the highest point of the cutting blade 4 in each dimension. The vertical distance from the highest point of the cutting blade 4 to the central axis of the same plane as the drill bit axis is the working radius of the drill bit. The height of the cutting blade 4 can be obtained by combining the distance from the point of the cutting blade 4 to the projection point of the drill bit body 2 to the top of the drill bit body with the blade's forward tilt angle using the Pythagorean theorem. The vertical distance from the front end and the rear end of the cutting blade 4 to the drill bit body 2 is equal to the bidirectional drill bit radius.

[0222] After calculation, the back tilt angle of cutting tooth 5 was designed to be 18° to 20°. The function of the front tilt angle is to generate a lateral force on the rock layer when cutting the formation, so that the rock cuttings move to the two sides of the drill bit edge. It is also a key factor in preventing mud packing. The front tilt angle is usually designed to be in the range of 0° to 38°. In order to improve the chip removal capacity, the side tilt angle was finally selected to be 35°.

[0223] Further, step f includes:

[0224] Step f1: Establish a three-dimensional model of the entire bidirectional drill bit;

[0225] Step f2 involves using a laser cutting machine and a DMG five-axis machining center to process the parts, and then using brazing and MIG welding to weld the parts together to complete the overall processing.

[0226] To verify the safety and reliability of the present invention, a strength check was performed on the reciprocating rotary bidirectional drill bit applicable to drilling soft mud rock formations according to the present invention:

[0227] First, a two-way interaction model between the drill bit and the rock is established.

[0228] The model consists of two parts: a geometric analysis based on kinematics and a force analysis of the cutting teeth. The forces acting on the drill bit during actual drilling are extremely complex, and fully simulating the real motion of the drill bit is a very large and complex calculation process. Considering that the model aims to determine the general laws governing the drilling effect of the drill bit, the operational model can be simplified.

[0229] Assuming the central axis of the bidirectional drill bit coincides with the center line of the borehole at the bottom of the well during drilling, this is equivalent to establishing the average motion value of the bidirectional drill bit during drilling. Based on the helical drilling path, the equation of motion can be expressed as:

[0230]

[0231] (R0, θ0, Z0) are the initial coordinates of the cutting drill.

[0232] (R t θ t Z t ) represents the position coordinates of the point in the drill bit coordinate system after time t, and ω is the angular velocity;

[0233] l is the depth drilled in one revolution of the drill bit.

[0234] By utilizing the interference phenomenon between the bottom-of-well model and the cutting model, the position of the cutting tooth 5 in the axial plane is calculated for each revolution of the bidirectional drill bit.

[0235] like Figure 6 As shown in the image, the drilling process of the three cutting teeth 5 is illustrated. To facilitate understanding of the model's working principle and simplify the drilling process and axial surface contour, the cutting teeth 5 are numbered as: P, P... n+1 P n-1 .

[0236] The solid line K is part of the contour line of the cutting tooth 5 passing through the plane of the axis in real time;

[0237] solid line K n+1 K n-1 They correspond to P respectively n+1 P n-1 Historical position of cutting tooth 5 across the same axial plane;

[0238] The dashed line in the figure represents the position curve traversed by the drill bit in the previous revolution. The shaded area in the figure can be considered as the actual cutting area of ​​cutting tooth 5. In the actual calculation process, the axial profile of the rotating cutting tooth 5 is discrete.

[0239] Therefore, the cutting area can be calculated using the kinematic equations. The area calculation is then transformed into calculating the area of ​​a polygon composed of N discrete points, as follows:

[0240]

[0241] The volume of rock layer cut by the cutting teeth in one revolution of the drill bit is:

[0242] V = 2πRS

[0243] Applying calculus to the calculation of the cutting arc length K

[0244] Assuming the cutting arc length is composed of n points, and the distance between any two points is dl, the total cutting arc length is:

[0245] K = (n-1)dl

[0246] The force analysis of the cutting edge of cutting tooth 5 during drilling is as follows:

[0247]

[0248] In the formula, F1 represents the tangential force of the cutting edge;

[0249] F2 represents the axial force at the cutting edge;

[0250] C1 represents the correlation coefficient with caster and roll angles;

[0251] C2 represents a constant coefficient;

[0252] The coefficients C1 and C2 were obtained based on cutting experiments of a single cutting tooth 5;

[0253] δ represents the back rake angle of cutting tooth 5;

[0254] Indicates the internal friction angle related to rock properties;

[0255] σ represents the uniaxial compressive strength of the rock;

[0256] ξ represents a coefficient related to the size and shape of the cutting area;

[0257] K represents the effective cutting arc length of the cutting edge;

[0258] H represents the equivalent cutting height of the cutting area;

[0259] Complete the three-dimensional modeling and mesh generation of the cutting blade (4) in ANSYS, and add the forces F1 and F2 of the cutting edge (5) during the drilling process to ANSYS for stress intensity simulation. If the maximum equivalent stress intensity on the cutting blade (4) unit mesh is less than the yield limit of the material selected for the blade, then the blade is safe during the drilling process.

[0260] Assuming the rotational speed of the bidirectional drill bit is n r / min, and an axial force is applied in the drilling direction, then the depth of rock cut by each cutting blade 4 per rotation is:

[0261]

[0262] In the formula: H represents the cutting depth, in cm;

[0263] V represents the drill bit speed, in cm / min;

[0264] n represents the drill bit rotation speed, r / min;

[0265] 'a' represents the number of winglets.

[0266] During drilling, the V value is usually 45-50 cm / min, the rotation speed n is 100-150 r / min, and the number of drill bit blades a = 3. Therefore, the cutting depth range of the drill bit is 0.1-0.166 mm.

[0267] It can be seen that the maximum cutting depth of rock strata is 24.9 cm per minute, thus improving cutting efficiency.

[0268] The drill bit is suitable for soft rock formations with a strength coefficient of K = 2-4. Since sedimentary soft rock and fractured tectonic rocks are easily broken and prone to forming drill bit encasement, the axial force design takes metamorphic soft rock as the consideration. The limit value is 10MPa = 10kg / cm2.

[0269] Axial pressure on the drill bit:

[0270]

[0271] In the formula: P represents the compressive strength of soft rock, kg / cm2;

[0272] k represents the ratio of the cutting resistance strength to the compressive strength of soft rock, k = 0.82;

[0273] β represents the coefficient of friction between the cutting edge and the rock layer. For cutting edges inlaid with cemented carbide, u = 0.5 to 0.7.

[0274] H1 represents the wear thickness at the edge of the main cutting edge, in cm;

[0275] D represents the drill bit diameter, in cm.

[0276] The wear at the cutting edge of the drill bit is relatively small during drilling in soft rock formations, so H1 can be taken as 8mm. Before drilling, the axial pressure of the drill bit needs to be calculated based on the actual drilling conditions. According to the calculation formula, the axial pressure borne by the compound rotary bidirectional drill bit during drilling increases with the increase of the ratio coefficient between cutting strength and compressive strength.

[0277] Example 1:

[0278] In the first step of this embodiment, the bidirectional drill bit modeling and corresponding component manufacturing are completed using the design method of the reciprocating rotary bidirectional drill bit applicable to drilling in soft mudstone formations according to the present invention.

[0279] The second step is to select high-quality carbon steel and machine the drill body 2. During the machining process, pay attention to evenly distributing 2mm deep blade grooves 3 in the circumferential direction.

[0280] The third step involves using a laser cutting machine to cut the high-quality carbon steel blade 4.

[0281] The fourth step involves machining the alloy groove and weld bevel on the forward rotation side of the cutting blade 4, according to the selected cemented carbide dimensions.

[0282] The fifth step is to weld the machined cutting blade 4 and drill body 2 using gas shielded welding. During welding, pay attention to adding a pre-weld heat treatment step to avoid deformation of the cutting blade 4.

[0283] The welded blades and drill body are subjected to post-weld heat treatment to eliminate welding stress; the cutting blades 4 and drill body 2, which have been heat-treated to 320℃, are taken out; the cutting teeth 5 are arranged in a straight line and the composite pieces are brazed to the cutting blades 4 in sequence, while ensuring the brazing quality. The welded cutting teeth should be 2-3.5mm higher than the step surface to ensure that the cutting teeth 5 are sharp.

[0284] The sixth step is to use a DMG five-axis machining center to process the drainage groove 2 and the external dimensions of the welded drill bit body 2.

[0285] The seventh step is to finally complete the machining of the thread groove 7 according to the thread specifications of the selected drill rod, and fix the thread groove 7 to the drill body 2.

[0286] This completes the fabrication of the reciprocating rotary bidirectional drill bit suitable for drilling soft mudstone formations according to the present invention.

Claims

1. A design method for a reciprocating rotary bidirectional drill bit for drilling in soft mudstone formations, characterized in that, The drill bit body (1) is cylindrical, with its head serving as the connection end to an external device and its tail serving as the drainage end, which is provided with a rounded chamfer. Multiple through waist-shaped drainage grooves (2) are evenly provided on the side wall of the drainage end along the circumference; three through blade grooves (3) are provided on the drill body (1) along the circumference, and the blade grooves (3) extend along the axial direction of the drill body (1); the starting point of all the blade grooves (3) is on the same plane as the starting point of the chamfered arc of the drainage end of the drill body (1); a cutting blade (4) is fixedly installed in each blade groove (3), and the tail end of the cutting blade (4) extends out of the drainage end of the drill body (1) and does not contact the drainage groove (2); The cutting blade (4) has a crown-shaped structure. The inclination angle of the head of the cutting blade (4) is smaller than the inclination angle of the tail side. Multiple mounting slots are arranged sequentially along the axial direction of the drill body (1) on the end face of the cutting blade (4) away from the drill body (1). A square columnar cutting tooth (5) is installed in each mounting slot. The aforementioned design method for a reciprocating rotary bidirectional drill bit for drilling in soft mudstone formations includes the following steps: Step a, design the drill bit body (1) specifications according to actual usage requirements; Step b: Design three blade grooves (3) evenly along the circumference on the drill body (1); design a threaded groove (7) with internal thread that is coaxially connected to the drill body (1) on the connecting end of the drill body (1). Step c: Determine the geometric parameters of each cutting tooth (5), and determine the normal angle, back rake angle and side rake angle of the corresponding cutting tooth (5) based on the geometric parameters of each cutting tooth (5); establish a CAD model of the cutting tooth (5) arrangement based on the normal angle, back rake angle and side rake angle of each cutting tooth (5); Step d: Design the specifications of the cutting blade (4), and design a mounting groove on the cutting blade (4) corresponding to each cutting tooth (5) according to the CAD model of the cutting tooth (5) arrangement; Step e: Design multiple through drainage grooves (2) uniformly along the circumference at the drainage end of the drill bit body (1). Step f: Establish a three-dimensional model of the reciprocating rotary bidirectional drill bit for drilling soft mudstone formations, and complete the manufacturing and assembly based on the three-dimensional model; Step c includes the following sub-steps: Step c0: Randomly select a cutting tooth (5) as the current cutting tooth; Step c1: Determine the geometric parameters of the initial working plane of the current cutting tooth (5); Take the cutting surface of all cutting teeth (5) on the rock as the initial working plane, and take this plane as the original starting plane of the orthogonal transformation; Assume that the normal angle, roll angle, and backslope angle of the initial working plane are all zero degrees, and establish the rotation axes for these three directions: the normal axis, the roll axis, and the backslope axis, respectively. The intersection of one corner of the current cutting tooth (5) and the cutting blade (4) is taken as the center coordinate. O ; Let the normal axis direction vector of the current cutting tooth (5) be... The lateral axis direction vector is The direction vector of the backslope axis is The external normal vector of the working plane is ; The initial working plane vector parameters are as follows: O （0，0，0）； The normal axis direction vector is (0, 1, 0); Lateral axis direction vector is (1, 0, 0); The direction vector of the backslope axis is (0, 0, 1); The outer normal vector is (0, 1, 0); Step c2, determine the orthogonal transformation matrix of the current cutting tooth (5) rotating around the standard X, Y and Z axes; The orthogonal transformation matrix of the cutting tooth (5) rotating about the positive X-axis is: in, The angle of rotation of the cutting tooth (5) around the X-axis; The orthogonal transformation matrix of the cutting tooth (5) around the Y-axis is: in, The angle of rotation of the cutting tooth (5) around the Y-axis; The orthogonal transformation matrix of the cutting tooth (5) around the Z-axis is: in, The angle of rotation of the cutting tooth (5) around the Z-axis; Step c3: Determine the geometric parameter expression for the rotation of the current cutting tooth (5) around the actual axis; in: Represents the rotation matrix; T This indicates a rotational transformation performed on a point or vector in space. Represents the rotation vector; Indicates the angle of rotation about the axis of rotation; Represents a point or vector in space; Represents the coordinates or vector of a point after rotation transformation; The coordinates or vectors representing the rotation of a point on the cutting tooth (5) around a standard coordinate axis; This represents the coordinates or vector of the cutting tooth (5) after it has rotated around any axis; Represents a rotating unit vector; and Formula for rotation angle; Step c4: Obtain the geometric parameter expression of the normal axis of the current cutting tooth (5); The normal axis vector of the cutting tooth (5) passes through n After the orthogonal transformation, it can be expressed in the form of a linear transformation as follows: n Indicates the degree of orthogonal transformation; This represents the initial vector of the normal axis of the cutting tooth (5); This indicates that the normal axis of the cutting tooth (5) passes through... n The vector after the transformation; Indicates to conduct n Orthogonal transformation; Step c5, determine the geometric parameter expressions for the back tilt axis and side tilt axis of the current cutting tooth (5); Initial working plane center coordinates O After translating by d from the origin (0, 0, 0), the center coordinates are O (0, 0, d), after the initial working plane is translated, the self-coordinate of the cutting tooth (5) changes, but the axis of rotation remains unchanged. Taking the origin of the coordinate system as the reference point, then d = 0; after the transformation Q Dot and O The linear transformation of the point is as follows: The initial working surface is rotated about the Y-axis, and the rotation angle is set to θ. The normal vector of the working surface after rotation and the corresponding roll axis Expressed using linear transformation and transformation matrices respectively: Initial working face around the tilt axis Rotation, assuming the rotation angle is... The normal vector of the corresponding working plane is Similarly, the lean angle at this time is Its linear transformation form is as follows: Initial working face around the back tilt axis Rotation, assuming the rotation angle is... The normal vector of the corresponding working plane is Its linear transformation form is as follows: The initial working surface is rotated about the Z-axis, and the axial azimuth angle is rotated by γ. The corresponding external normal vector of the working plane is... Its corresponding O Dot and Q At this point and Their linear transformation forms are as follows: This represents an orthogonal transformation, where the initial working surface is rotated about the Y-axis by an angle of θ. The corresponding normal vector coordinates at that time; This represents a quadratic orthogonal transformation, where the initial working face is about the tilt axis. Rotate, rotation angle is The corresponding normal vector coordinates at that time; This represents a three-way orthogonal transformation, with the initial working surface revolving around the backslope axis. Rotate, rotation angle is The corresponding normal vector coordinates at that time; This represents the coordinates of the normal vector when the initial working surface is rotated around the Z-axis after a fourth orthogonal transformation, with the axial azimuth angle rotation angle being γ. Step c6: Determine the normal angle, back rake angle, and side rake angle of the cutting tooth (5); The results of steps c1 to c5: the geometric parameters of the initial working plane of the current cutting tooth (5), the orthogonal transformation matrix of the current cutting tooth (5) rotating around the standard X, Y and Z axes, the geometric parameter expression of the current cutting tooth (5) rotating around the actual axis, the geometric parameter expression of the normal axis of the current cutting tooth (5), and the geometric parameter expressions of the back tilt axis and side tilt axis of the current cutting tooth (5) are input into Matlab, and Matlab automatically calculates and obtains the normal angle, back tilt angle and side tilt angle of the cutting tooth (5); Step c7: Select a cutting tooth (5) that has not yet been calculated, and repeat steps c1 to c6; Step c8, repeat step c7, until all cutting teeth (5) have been traversed; Step c9: Create a CAD model of the arrangement of all cutting teeth (5).

2. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 1, characterized in that, The drill bit body (1) is coaxially provided with a central column (6), and the lower ends of all the cutting blades (4) enter the drill bit body (1) and are fixedly connected to the central column (6). The tilt angle of the head of the cutting blade (4) is 18°~20°; the tilt angle of the tail of the cutting blade (4) is 0°~38°.

3. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 2, characterized in that, The number of drainage grooves (2) is 6, and two drainage grooves (2) are provided between each two adjacent cutting blades (4).

4. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 3, characterized in that, The drill bit body (1) has a threaded groove (7) with an internal thread coaxially provided on the connecting end; The minimum distance between the threaded groove (7) and the cutting blade (4) is not less than 15mm and the maximum distance is not greater than 25mm.

5. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 4, characterized in that, The drill bit body (1) is made of 42CrMoA high-quality medium carbon alloy steel; the cutting teeth (5) are made of YG8 cemented carbide; the cutting teeth (5) have a specification of 4mm. 10mm 2mm.

6. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 5, characterized in that, In step a, The drainage trough (2) meets the following conditions: Let the outer diameter of the drill bit body (1) be D, the width of the drainage groove (2) be H = 1 / 4D, and the length of the drainage groove (2) be L = 3 / 4H.

7. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 6, characterized in that, Step d includes: Step d1: Select the guiding capability level, outer cone height and inner cone height of the reciprocating rotary bidirectional drill bit for drilling soft mud rock strata according to the classification of the drill bit crown profile; For drilling in soft mudstone formations, the guiding capability of the reciprocating rotary bidirectional drill bit is selected as level 3, and the crown profile of the cutting blade (4) is selected as level 2. The outer cone height of the cutting blade (4) is 3 / 4 of the drill body (1), and the inner cone height of the cutting blade (4) is 1 / 10 of the diameter of the drill body (1). Step d2: Based on the CAD model of the arrangement of the cutting teeth (5), design mounting slots on the cutting blade (4) that correspond one-to-one with each cutting tooth (5).

8. The design method for a reciprocating rotary bidirectional drill bit for drilling soft mudstone formations as described in claim 7, characterized in that, Step f includes: Step f1: Establish a three-dimensional model of the entire reciprocating rotary bidirectional drill bit for drilling soft mudstone strata. Step f2 involves using a laser cutting machine and a DMG five-axis machining center to process each component, and then using brazing and MIG welding to weld the components together to complete the overall processing.

Images