RU2377384C1 - Drilling bit with polycrystalline diamond elements - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: invention refers to drilling bit cutting structure, and namely to rock destruction diamond elements, the so-called PDC elements. Installation scheme of side reinforcing diamond cutters on blades of drilling bit is of great importance. Polycrystalline diamond elements located in cylindrical portion of blades and intended for protection of drilling bit against wear diametrically has an inclination to reinforcing surface at an acute angle of 2° to 6° in bit rotation direction, and their highest parts are located at maximum diametre of the bit flush with surface of body thus excluding full sinking of diamond layer in the bit body, and serve for protecting diametre of bit against wear from the very beginning till the end of drilling process. Facing tools with flat edge surface perpendicular to their axis are installed and fixed in holes the axes of which are inclined at an acute angle of 2° to 6° relative to reinforcing surface of body in bit rotation direction. As per the second version, reinforcing facing tools of PDC, which are provided with edge diamond surface inclined at an acute angle of 2° to 6° to their axis, are installed in holes the axes of which are made along radii of body with constant orientation of the above inclination in bit rotation direction.

EFFECT: improvement of operating characteristics.

3 cl, 8 dwg

Description

The invention relates to the arming of drill bits with polycrystalline diamond elements (PDC).

Known drill bit with polycrystalline diamond elements [1], taken as an analogue. This bit includes a threaded nipple welded to the body of the bit for attachment to the drill pipe string and blades extending down from the body, equipped with PDC elements (cutters) for rock destruction, internal cavities and channels for supplying flushing fluid to the bottom of the well, carbide tips installed at the exit of these channels. The cutters located in the cylindrical part of the blades of the body are mounted flush with the surface of the blade and serve to protect against wear of the diameter of the body of the bit, and can be either carbide or with a polycrystalline diamond layer (PDC). The end surface of PDC cutters wears out during drilling much slower than a steel body reinforced simply with carbide cutters, and contributes to a significant reduction in the bit wear rate, since diameter wear of the bit is one of the main criteria in determining the suitability of the bit before it is lowered into the well. A new bit made at the lower limit of the diameter tolerance field (for example, for ⌀215.9 mm-0.51 mm) will have a minimum resource. In diametrical terms, the resource of a diamond bit that is lowered to the bottom of a well for the first or second time, as a rule, does not exceed 2 values of the established tolerance for the production of a bit from the lower limit (in our example, it is 1.02 mm). A bit having a diameter of 214.37 mm after wear will be considered to have fully exhausted its resource, i.e. worn out. Therefore, it is preferable that the new bit is performed to the maximum allowable size (⌀215.9 mm). According to the above criterion, a bit has a maximum resource, ceteris paribus.

However, given the designated tolerances on the elements of the bit, it is practically impossible to produce a bit of exactly the maximum size. In the manufacturing process, cases of drowning and protrusions of the cutters beyond the maximum allowable diameter are possible (in our example 215.9 mm). If the bit with carbide teeth protruding above the body is relatively easy to grind to the desired size, then the bit reinforced with PDC cutters is practically impossible to grind. If, nevertheless, low-performance grinding of the superhard PDC material is carried out with diamond grinding wheels, then, as a rule, the strength properties of the PDC element are violated - cracks in the diamond layer occur, it may peel off during grinding or, even worse, during the operation of the bit.

In the case when the PDC elements are buried in the body of the bit, even if the body itself is polished to the maximum size, there is a rapid wear of the body by the amount of drowning, and only then the reinforcing PDC elements begin to work.

When making the hole with the deepest tolerance for the diamond cutter (with a tolerance of +0.13 mm) and using the shortest cutter with a tolerance of -0.1 mm in length, the depth of drowning it from the surface of the maximum allowable diameter of the bit can immediately be 0.23 mm (the sum of the tolerances is 0.13 + 0.1 mm), and this is an almost completely established tolerance on its diameter (on the side) during manufacture (0.51 / 2 = 0.255 mm).

In this case, the new bit is already approximately one third as long as the resource is worn out in diameter (0.46 mm from the allowable nominal wear of 1.53 mm).

Another diamond bit is known [2], taken as a prototype. In this bit, as well as in the analogue, a threaded cylindrical body is used to attach to the drill pipe string, the body is reinforced with PDC side inserts in diameter, there are also blades extending downward with PDC cutting elements for rock destruction, internal blades and channels for supplying flushing fluid to the bottom, carbide nozzles installed at the outlet of these channels.

The disadvantage of the prototype can be fully attributed to the lack of analogue, which consists in the difficulty of setting the level of the relative nominal diameter and fastening of the side reinforcing cutters (inserts) that are complete in terms of their wear life. In addition, the side inserts protruding beyond the dimensions of the body experience significant impacts that cut off the end part of the loads from the reaction of the rock on the walls of the well during rotation of the bit, contributing to the separation of PDC plates (tablets) from the lower base of the insert.

The technical result of the present invention is to increase the durability and stability of the drill bits with polycrystalline diamond cutters.

The technical result is achieved in that in a drill bit with polycrystalline diamond elements, including a cylindrical body with a thread for connection to the drill pipe string and with PDC lateral reinforcing elements in diameter, blades extending downward with PDC cutters for rock destruction, internal cavities and channels for supply of flushing fluid to the bottom, carbide nozzles installed at the outlet of these channels, the outer surface of the side polycrystalline diamond elements is inclined to be reinforced by Surfaces at an acute angle ranging from 2 ° to 6 ° in the direction of rotation of the bit, and their highest parts are located on the maximum diameter of the bit flush with the surface of the body, thereby eliminating the option of drowning the diamond layer in the body of the bit, and serve to protect the diameter of the bit from wear from the very beginning of the use of the bit to the full development of the set resource of the bit according to this parameter.

The specified inclination of the side reinforcing elements of the PDC at an acute angle can be carried out in two ways.

In the first embodiment, lateral reinforcing elements with a flat end surface perpendicular to their axis are installed in holes whose axes are inclined to the reinforced surface at an acute angle from 2 ° to 6 ° in the direction of rotation of the bit.

In the second embodiment, the PDC lateral reinforcing elements themselves, made with a slope of the end outer surfaces at an acute angle from 2 ° to 6 ° to their axis, are installed in holes whose axes are made along the body radii with a constant orientation of the indicated inclination towards the bit rotation.

Such schemes for installing lateral reinforcing elements allow us to solve two problems at once - technological and strength.

The technological challenge lies in the possibility of installing the raised edge of each diamond element on the above full-fledged maximum bit diameter (in our example, it is 215.9 mm). If the raised edges of the part of the diamond element are higher than the dimensions of the maximum allowable diameter of the bit, their sharp small peaks can be removed using a diamond grinding wheel, which is incomparably faster and easier than with the traditional installation of elements with a polycrystalline diamond layer in the considered analogue and prototype.

The strength task is to install the outer surface of the side reinforcing diamond elements in such a way as to change and significantly reduce part of the shearing-tearing forces from the reaction of the rock to the top of the cutter, replacing them with shear-pressing. This ensures a smooth meeting of the cutter with the rock, reduces the required moment of rotation attached to the bit.

Thus, the increase in the efficiency of the lateral reinforcing elements occurs due to the features of the structural scheme of their installation in the holes on the housing, as well as due to the redistribution of external forces acting on polycrystalline diamond elements.

For illustrative purposes, the invention is described by the example of cylindrical cutters, it should be understood that the cutters may have other modifications in the form of non-circular variants.

The list of drawings. According to established practice, various parameters of the drawings are not given to scale.

Figure 1 shows a vertical section of a diamond bit with the location of all its elements. Figure 2 shows a fragment of a transverse section of the body of the bit along AA with examples of drowning of the diamond element in the body and protruding above the body of the bit in accordance with the analogue and prototype, as well as its location flush with the surface of the body of the bit.

Figures 3 and 4 show fragments on an enlarged scale of the transverse section of the body of the bit along AA in accordance with the analogue and prototype. Figures 5 and 6 show a diagram with an example of the proposed options for the angle of inclination for the side elements of the PDC. Figure 6 in a top view conventionally shows the grinding area of the edge of the element (tablets PDC) for this option. 7 shows a second variant with the proposed angle α of inclination of the side elements of the PDC. On Fig shows a modified diagram of the loads arising from the meeting of the side elements with the drilled rock.

1 and 2 are marked by the positions: the nipple part of the bit 1 with thread 2 for attachment to the drill pipe string, the casing of the bit 3, the reinforcing side elements of the PDC 4, the blades 5 of the body of the bit with cutting PDC 6 cutters, the central cavity of the bit 7, channels 8 for supplying flushing fluid to the bottom of the well, carbide nozzles 9. Item 10 - line of the maximum diameter of the bit (in our example 215.9 mm), item 11 - line of the minimum allowable diameter of the new bit (in our example, corresponds to the size of 215.9- 0.51 mm), pos. 12 - line of maximum allowable wear diameter of the worked bit (corresponds to a diameter of 215.9-0.51-1.02 = 214.37 mm), pos. 13 - insert with a minimum protrusion, pos. 14 - insert with a nominal protrusion, pos. 15 - insert with a maximum grinding to be performed. Figure 3 shows a fragment of figure 2 on an enlarged scale. This is an option for installing PDC elements in the case, when the element 13 has a minimum height dimension, and the hole is made at the upper limit of the depth tolerance field.

Figure 4 shows another fragment of figure 2 on an enlarged scale. This is a possible installation of the cutter 15, when the hole in depth is made to a minimum, and the polycrystalline diamond element has a maximum height. In this case, the end surface of the element must be ground for a very long time along the diamond peak to obtain the maximum allowable diameter (in our case, 215.9 mm). In this case, during grinding, the appearance of cracks and delamination of the diamond layer is not excluded.

Figure 5 and figure 6 shows a diagram of the proposed installation of the PDC element with the slope of its top in the direction of rotation of the bit. 5 is a diagram of the installation at the nominal hole depth and maximum height of the protrusion of the diamond element. The protruding part of the element 16 lies above the line 10 of the maximum diameter, and the opposite inclined part of the surface of the element overlaps the line 12 of the maximum allowable wear of the bit. In this case, the maximum protruding part of the diamond element, extending beyond the line of maximum diameter, requires minor grinding, without processing the bulk on the end plane of the diamond element. At the same time, the part of the diamond element recessed into the body, due to the selected inclination (from 2 ° to 6 °), covers almost the entire line of allowable wear, and the PDC tablet participates in the work of the bit from the beginning to its rise from the bottom of the well to the surface.

6, reference numeral 17 shows the surface of the PDC element not to be machined when installed in the hole. Figure 7 shows the preferred case when, when installing the cutter, its highest part coincides with line 10, and the recessed part is at a level not lower than line 12. Figure 8 shows a modified diagram of the loading of the PDC tablet from the reaction of the rock wall wells due to the inclination of the surface of the cutter. Position 18 in Fig.7 and 8 indicate the proposed element PDC with an inclination in the direction of rotation of the bit.

In figure 4, the arrow shows the direction and magnitude of the vector F of the tablet loading on the PDC element according to the analogue and prototype. In Fig. 8, a vector F of the same magnitude changes its direction and the nature of the effect on the PDC tablet. In this case, the shear force (Fig. 4), which tends to tear the PDC tablet out of the hole, changes according to the parallelogram rule to shear-and-hold (vectors K and G).

The minimum angle of inclination α of the outer surface of the PDC element in the direction of rotation of the drill bit, which allows to ensure a full maximum working size by the diameter of the bit, is determined from the ratio

(a + b) ≥d

where a is the value of half the tolerance on the diameter of the bit (tolerance on the side), mm;

b - half of the tolerance for the maximum allowable wear during operation, after which it is not recommended to re-lower the bit to the bottom of the well (side tolerance), mm;

d is the diameter of the PDC element, mm.

For example, for a bit ⌀215.9 mm at a = 0.251 mm; b = 0.51 mm and d = 12 mm, the angle of inclination α of the outer surface of the PDC element in the direction of rotation will be: (0.251 + 0.51) ≥12 · sin α; sin α = 0.761 / 12 = 0.063; α≈4 °.

As noted above, a positive effect from the use of the proposed bit is achieved by changing the structural form of the side reinforcing inserts, changing the technological scheme of their installation, ensuring the replacement of the end shear and tearing force in contact with the drilled rock by a shear-pressing force, while reducing the required torque chisels.

The results of field tests of samples of the proposed bits with polycrystalline diamond elements confirmed an increase in their durability and performance indicators compared to existing similar designs.

Information sources

1. US patent No. 4544441 from 08/10/1985, CL. ЕВВ 10/46 (analogue).

2. US patent No. 4794994 from 01/03/1989, CL. ЕВВ 10/60 (prototype).

Claims (3)

1. A drill bit with polycrystalline diamond elements, including a cylindrical body with a thread for connecting to the drill pipe string and with PDC lateral reinforcing elements along its diameter, blades extending downward with PDC cutters for rock destruction, internal cavities and channels for supplying flushing fluid to the bottom , carbide nozzles installed at the outlet of these channels, characterized in that the outer surface of the side polycrystalline diamond elements is inclined to the reinforced surface under a sharp glom in the range from 2 to 6 ° in the direction of rotation of the bit, and their highest parts are located on the maximum diameter of the bit flush with the surface of the body. 2. The drill bit according to claim 1, characterized in that the lateral reinforcing elements with a flat end surface perpendicular to their axis are installed in holes whose axes are inclined to the reinforced surface at an acute angle from 2 to 6 ° in the direction of rotation of the bit. 3. The drill bit according to claim 1, characterized in that the lateral reinforcing elements themselves, made with a slope of the end outer surfaces at an acute angle from 2 to 6 ° to their axis, are installed in holes whose axes are made along the radii of the body, with a constant orientation the indicated inclination in the direction of rotation of the bit.

Images