An anti-vortex PDC drill bit for dolomite formations

Abstract

The present invention discloses an anti-vortex PDC drill bit for dolomite formations, which belongs to the technical field of oil exploration drilling bits. It includes a main body and a plurality of auxiliary blades and main blades connected to the main body, and a plurality of nozzles are provided between the auxiliary blades and the main blades. It is characterized in that the outer side of the shoulder and the gauge portion of the auxiliary blades and the main blades are provided with a plurality of conical teeth, and the other cutting parts of the auxiliary blades and the main blades are provided with a plurality of multi-edge teeth; in the direction of travel of the drill bit, the tooth arrangement height of the conical teeth is higher than that of the adjacent multi-edge teeth. Based on the lithologic characteristics and rock mechanics parameters of the dolomite formation, the present invention adopts a mixed tooth arrangement method of conical teeth and multi-edge teeth. The sum of the force vectors of the cutting teeth is close to zero, and the drill bit runs in a stable state, thereby improving the drill bit's anti-vortex ability and stability.

Description

Technical Field

[0001] The invention belongs to the technical field of oil exploration drilling bits, and in particular relates to an anti-vortex PDC drill bit for dolomite formations. Background Art

[0002] Polycrystalline Diamond Compact (PDC) drill bits, also known as PDC drill bits, are made of small cutting segments made of polycrystalline diamond (thin discs) embedded or sintered into the drill bit body. Diamond drill bits used in oil exploration drilling consist of a drill body made of machined and heat-treated raw steel and diamond compact cutting teeth brazed to the front of the drill blade cutting face. During the drilling process, while the PDC drill bit rotates regularly with the drill string, it can also lose stability due to unbalanced dynamic forces, causing the center of rotation to shift momentarily on the drill bit's working surface. This phenomenon is known as bit vortex.

[0003] During drilling in the carbonate reservoirs of the Tarim Oilfield platform basin, large sections of dolomite were encountered. Due to its extremely high uniaxial compressive strength and large internal friction angle, the triaxial compressive strength in the deep strata is extremely high, resulting in poor drillability. Conventional PDC drill bits struggle to achieve effective cutting depth during rock shearing, which in turn increases horizontal vibration. This, coupled with the actual drill bit speed and unbalanced forces, further develops into vortex motion, causing fracture damage to the diamond cutters from the high-frequency impact, reducing rock breaking efficiency and drill bit footage. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a vortex-resistant PDC drill bit for dolomite formations, which can reduce the load impact from the formation, improve the drill bit's vortex-resistant ability for different dolomite formations, and effectively improve the rock breaking efficiency of dolomite formations.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention discloses an anti-vortex PDC drill bit for dolomite formations, comprising a main body and a plurality of auxiliary blades and a main blade connected to the main body, a plurality of nozzles being arranged between the auxiliary blades and the main blade, a plurality of conical teeth being arranged on the outer sides of the shoulders and the gauge parts of the auxiliary blades and the main blade, and a plurality of multi-ribbed teeth being arranged on other cutting parts of the auxiliary blades and the main blade; in the direction of travel of the drill bit, the tooth arrangement height of the conical teeth is higher than that of the adjacent multi-ribbed teeth.

[0007] Preferably, the outer sides of the gauge-guarding parts of the auxiliary blade and the main blade are connected with gauge-guarding wear-resistant blocks, and a plurality of gauge-guarding teeth are provided on the gauge-guarding wear-resistant blocks.

[0008] Further preferably, a plurality of inverted eye teeth are provided on the outer side of the gauge wear-resistant block.

[0009] Preferably, the anti-vortex PDC drill bit is a seven-blade drill bit.

[0010] Preferably, the nozzles are evenly distributed along the cutting surface.

[0011] Preferably, the multi-ribbed teeth are arranged in a staggered manner.

[0012] Preferably, the multi-ribbed teeth are tri-ribbed teeth.

[0013] Preferably, the diamond layer of the tapered teeth is sintered from diamond powder with an average grain size greater than 25 μm.

[0014] Preferably, the height difference between the conical tooth and its adjacent multi-ribbed tooth is:

[0015]

[0016] Among them, r is the distance between the tooth and the drill core axis, R is the drill radius, d is the tooth diameter, and a is an empirical coefficient determined according to the burial depth and strength of dolomite.

[0017] More preferably, a is -0.25 to 0.25.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The present invention discloses an anti-vortex PDC drill bit for dolomite formations, which adopts a mixed tooth arrangement of conical teeth and multi-edge teeth. The conical teeth are placed on the outside of the shoulder and the gauge portion of the blade, and the multi-edge teeth are placed in other positions of the blade, and the tooth arrangement height of the conical teeth is higher than that of the multi-edge teeth. The cutting unit of the conical teeth is conical. When contacting the dolomite formation, the top of the cone makes point contact with the rock, thereby forming a local stress concentration, causing early rock breaking, reducing the impact load on the drill bit, and improving the drill bit's anti-vortex ability and stability. The multi-edge teeth are special-shaped teeth with convex ridges. The cutting unit is a convex ridge. The convex ridge forms a line contact with the rock, causing stress concentration on the rock surface. Under the same impact energy, more impact energy is absorbed by the rock. At the same time, the diamond parts on both sides of the convex ridge still cause shear damage to the formation, thereby enhancing the impact resistance and cutting efficiency. When a drill bit's blades cut, they experience reaction forces from the formation. The drill bit's tooth layout determines the magnitude and direction of the sum of these reaction forces. Based on the lithologic characteristics and rock mechanics parameters of dolomite formations, this invention utilizes a mixed tooth layout of tapered and multi-edge teeth. This approach minimizes the sum of the force vectors on the cutting teeth, ensuring stable drill bit operation and improving the drill bit's vortex resistance and stability.

[0020] Furthermore, the gauge-guard wear-resistant block can protect the drill bit from damage during the drilling process, thereby improving the drill bit's ability to resist impact and wear; the gauge-guard teeth further improve wear resistance.

[0021] Furthermore, a plurality of undercut teeth are provided on the outer side of the gauge wear-resistant block to prevent the drill bit from getting stuck.

[0022] Furthermore, the seven-blade drill bit is more suitable for drilling and mining in dolomite formations.

[0023] Furthermore, the nozzles are evenly distributed along the cutting surface, which can take away the debris in time and prevent the drill bit from getting stuck.

[0024] Furthermore, the multi-edge teeth are arranged in a staggered manner, thereby improving cutting efficiency.

[0025] Furthermore, the diamond layer of the conical teeth is sintered from diamond micropowder with an average grain size greater than 25 μm, which enhances the fracture toughness of the diamond material and the corresponding impact resistance.

[0026] Furthermore, through tooth arrangement software simulation, the optimal rule for the height difference between conical teeth and multi-edge teeth was obtained, which can ensure the maximum efficiency of the drill bit; at the same time, empirical coefficients were used for correction according to the different dolomite burial depths and strengths to improve the scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the overall structure of the anti-vortex PDC drill bit for dolomite formations of the present invention;

[0028] Figure 2 This is a performance comparison chart of the drill bit of the present invention.

[0029] In the figure: 1- auxiliary blade, 2- multi-edge teeth, 3- gauge teeth, 4- inverted eye teeth, 5- body, 6- gauge wear-resistant block, 7- nozzle, 8- tapered teeth, 9- main blade. DETAILED DESCRIPTION

[0030] The present invention will be described in further detail below with reference to the accompanying drawings, which are intended to explain rather than limit the present invention:

[0031] like Figure 1 , is an anti-vortex PDC drill bit for dolomite formations according to the present invention, comprising a main body 5 and a plurality of auxiliary blades 1 and a main blade 9 connected to the main body 5, a plurality of nozzles 7 being arranged between the auxiliary blades 1 and the main blade 9, and characterized in that a plurality of conical teeth 8 are arranged on the outer side of the shoulder and the gauge portion of the auxiliary blade 1 and the main blade 9, and a plurality of multi-ribbed teeth 2 are arranged on other cutting parts of the auxiliary blade 1 and the main blade 9; in the direction of travel of the drill bit, the tooth arrangement height of the conical teeth 8 is higher than that of the adjacent multi-ribbed teeth 2.

[0032] The cutting unit of the conical tooth 8 is conical. When it contacts gravel, the top of the cone makes point contact with the rock, thereby forming local stress concentration, breaking the rock in advance, reducing the impact load on the drill bit, and improving the drill bit's anti-vortex ability and stability.

[0033] In a preferred embodiment of the present invention, the outer side of the gauge portion of the secondary blade 1 and the primary blade 9 is connected to a gauge wear block 6, which is provided with a plurality of gauge teeth 3. Preferably, the outer side of the gauge wear block 6 is provided with a plurality of undercut teeth 4.

[0034] In a preferred embodiment of the present invention, the anti-vortex PDC drill bit is a seven-blade drill bit, each having three main blades 9 and four auxiliary blades 1. The three main blades 9 are evenly distributed, and one, one, and two auxiliary blades 1 are respectively arranged between the three main blades 9.

[0035] In a preferred embodiment of the present invention, the nozzles 7 are evenly distributed along the cutting surface. They can be located at the junction of adjacent blades in order to promptly flush away gravel during drilling and avoid getting stuck in various gaps in the drill bit, which would affect drilling.

[0036] In a preferred embodiment of the present invention, the multi-ribbed teeth 2 are arranged in a staggered manner, with the acting forces directed in different directions, resulting in high cutting efficiency.

[0037] In a preferred embodiment of the present invention, the multi-ribbed teeth 2 are triangular teeth, each with three raised edges, the central protrusion forming a triangle. This creates a ridge on the edge of the cutting edge, serving as its cutting element. When the multi-ribbed teeth 2 come into contact with the formation, this ridge forms a line contact with the rock, causing stress concentration on the rock surface. At the same impact energy, more impact energy is absorbed by the rock. At the same time, the PDC diamonds on either side of the ridge still shear the formation, thereby enhancing impact resistance and cutting efficiency.

[0038] In a preferred embodiment of the present invention, the diamond layer of the tapered teeth is sintered from diamond micropowder with an average grain size greater than 25 μm.

[0039] In a preferred embodiment of the present invention, the height difference between the conical tooth 8 and its adjacent multi-ribbed tooth 2 (height of the conical tooth 8 - height of the multi-ribbed tooth 2) is:

[0040]

[0041] Where r is the distance between the teeth and the drill bit core axis, R is the drill bit radius, d is the tooth diameter, and a is an empirical coefficient determined based on the depth and strength of the dolomite. Preferably, a is between -0.25 and 0.25. For an 8000m well depth and a stratum with a compressive strength of 200 MPa, a value of 0.2 is most appropriate in actual design.

[0042] like Figure 2The upper part of the figure is the simulation result of a conventional drill bit, and the lower part is the simulation result of the anti-vortex PDC drill bit of the present invention. It can be seen that the vibration range of the conventional PDC drill bit is -50 to 50g, and the vibration range of the anti-vortex PDC drill bit of the present invention is -150 to 150g. The anti-vortex ability of the vortex PDC drill bit of the present invention is about 2 times higher than that of the conventional drill bit.

[0043] The above description is only part of the embodiments of the present invention. Although some terms are used in the present invention, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the present invention. Interpreting them as any additional limitations is contrary to the spirit of the present invention. The above description is only to further illustrate the content of the present invention with examples to facilitate easier understanding, but it does not mean that the embodiments of the present invention are limited to these. Any technical extension or re-creation made according to the present invention is protected by the present invention.

Claims

1. An anti-vortex PDC drill bit for dolomite formations, comprising a body (5) and a plurality of auxiliary blades (1) and main blades (9) connected to the body (5), wherein a plurality of nozzles (7) are provided between the auxiliary blades (1) and the main blades (9), and characterized in that: A plurality of conical teeth (8) are provided on the outer sides of the shoulders and the gauge portions of the auxiliary blade (1) and the main blade (9), and a plurality of multi-ribbed teeth (2) are provided on other cutting portions of the auxiliary blade (1) and the main blade (9); in the direction of travel of the drill bit, the tooth arrangement height of the conical teeth (8) is higher than that of the adjacent multi-ribbed teeth (2); The outer sides of the gauge-guarding parts of the auxiliary blade (1) and the main blade (9) are connected with gauge-guarding wear-resistant blocks (6), and a plurality of gauge-guarding teeth (3) are provided on the gauge-guarding wear-resistant blocks (6); The multi-ribbed teeth (2) are triangular teeth; The diamond layer of the conical teeth is sintered from diamond powder with an average grain size greater than 25um; The height difference between the conical tooth (8) and its adjacent multi-edge tooth (2): Among them, r is the distance between the tooth and the drill core axis, R is the drill radius, d is the tooth diameter, and a is an empirical coefficient determined according to the burial depth and strength of dolomite.

2. The anti-vortex PDC drill bit for dolomite formation according to claim 1, characterized in that: A plurality of inverted eye teeth (4) are provided on the outer side of the gauge wear-resistant block (6).

3. The anti-vortex PDC drill bit for dolomite formation according to claim 1, characterized in that: The anti-vortex PDC drill bit is a seven-blade drill bit.

4. The anti-vortex PDC drill bit for dolomite formation according to claim 1, characterized in that: The nozzles (7) are evenly distributed along the cutting surface.

5. The anti-vortex PDC drill bit for dolomite formation according to claim 1, characterized in that: The multi-ribbed teeth (2) are arranged in a staggered manner.

6. The anti-vortex PDC drill bit for dolomite formation according to claim 1, characterized in that: a is -0.25~0.25.

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