RU2515358C2 - Multi-row crown bit - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to rock crushing tool. Proposed crown bit comprises several rows of cutters located at different spacing from well work face. Top fixed row is arranged at their holders composed by ledges made at bit body end alternating with holders of several bottom moving rows of cutters. Note here that cylindrical shanks of said holders have a flat groove making upper and lower ledges and rigidly engaged with said holders fit, along with compression spring packs, in blind holes at bit body end, parallel with its axis. Compression force of springs in every row complies with axial load of rock crushing for given row to be crushed thereby. Note here that every next superlying row is intended for higher-hardness rocks compared with previous underlying row while first row cutters stay in permanent contact therewith in drilling. Cutter holders of moving rows along with pre-contracted packs of springs are retained in place due to thrust of cylinder shank flat groove top ledge against top face of thrust ring welded of two halves, fitted in ring groove made at bit body outer surface.

EFFECT: longer life, higher mechanical rate, lower power input, fast round-trip.

5 dwg

Description

The invention relates to a rock cutting tool designed for exploration drilling in often alternating physical and mechanical properties of rocks, mainly using double core pipes, including with a removable core receiver.

In such difficult drilling conditions, it is difficult to ensure the efficiency of the drill bit, since a significant difference in rock hardness, abrasiveness and fracture, and their frequent intermittency require appropriate and fundamentally different weapons, which cannot be combined in one standard drill bit. This leads to a significant investment of time in tripping operations in order to replace the drill bit with the corresponding physical and mechanical properties of the rock.

In addition, the desire to maximize the crown resource gradually led to excessive saturation of its end with rock-breaking elements to the detriment of the washing elements and, accordingly, to an increase in energy consumption and a decrease in the mechanical drilling speed.

Recent studies have established (see Superhard materials in a geological exploration tool / Collective of authors: R.K. Bogdanov, A.P. Zakora, AMIsonkin et al. Yekaterinburg: Publishing House of the Ural State Geological Administration, 2003, 138 pp.), Which, upon optimization structures of drill bits, it is necessary to strive to reduce the length of the diamond sectors and the number of carbide cutters, while maintaining a uniform load on their end. So, in diamond crowns with a diameter of 76 mm, with a decrease in the length of the end sector from 13 to 8 mm, their resource increased by 64%, and a decrease in the number of cutters of carbide crowns of the same diameter from 8 to 3 led to a twofold increase in mechanical speed

A well-known diamond drill bit (AS No. 1689581, authors Belov AM and others) with an additional body bearing its own set of cutters and connected to the main one through rivets that are cut by axial force after operation of the cutters located on the additional case, due to which the cutters of the main body of the crown enter the work.

Also known as a closer analogue, a two-tiered drill bit (AS No. 161008, authors L. Lachinyan and others), adopted as a prototype, the cutters of the upper fixed tier of which are mounted directly on the crown body, and the lower (temporarily fixed ), are also installed on the crown body, but on temporary supports with shock absorbing filler. First, the lower tier cutters work on this crown, upon which, after the blunting of the cutters, they create an excessive axial force, as a result of which the cutters of this tier cut the temporary support and, pressing into the crown body through the shock-absorbing filler, provide drilling with the upper tier cutters.

Such a crown, like the one mentioned above, has a higher resource in comparison with the usual one, which can significantly reduce the energy consumption of the drilling process and increase its mechanical speed. However, the possibility of linking the armament of such a crown with the frequently changing physicomechanical properties of the rocks encountered is limited, since after the triggering of the first tier of the incisors, it is not restored to meet the newly changed rock, i.e. has a single use.

The objective of the invention is to increase the efficiency of the drill bit by supplying it with a universal set of weapons and to ensure prompt inclusion in the work of the group of minimum necessary weapons that most fully corresponds to the physicomechanical properties of rocks passing at a given time with an unlimited frequency of their alternation.

To solve this problem, in the drill bit, which includes several tiers of cutters located at different distances from the bottom of the well, the upper fixed tier of cutters is mounted on their holders, which are protrusions at the end face of the crown body, interspersed with a minimum clearance with holders of several lower movable tiers of cutters, moreover, the cylindrical shanks of the holders having a flat groove forming the upper and lower ledges and firmly connected with the holders, together with the compression spring packs resting on them, also come with a minimum nym clearance into the blind holes made from the end crowns of the body parallel to its axis.

The compression force of the spring pack of each tier corresponds to the axial load of rock destruction, for drilling of which this tier of cutters is intended. Moreover, each subsequent upstream tier of the cutters, counting from the bottom, is intended for rocks of greater hardness than for rocks of the previous lower tier, and the cutters of the first tier from the bottom are in constant contact with the latter during drilling.

At the same time, the tool holders of the movable tiers, together with the pre-preloaded spring packages, are kept from falling out of their holes due to the stop of the flat groove of the tool shanks in the upper face of the support ring welded from two halves with the upper step, with a minimum diameter gap installed in the corresponding annular a groove made on the outer surface of the crown body.

When creating an axial load on the face that exceeds the limit for the cutters of the first tier from the bottom, the spring package of this tier is compressed and simultaneously the cutters of the second tier come into operation with its cutters.

With a further increase in the load on the face to a value exceeding the total maximum load of the first and second tier of the incisors, the shanks of the holders of the first from the bottom of the tier of the incisors, resting their lower ledge on the flat groove in the lower face of the mentioned support ring, raise and lower the incisors of the second the bottom of the tier, thereby ensuring the work of the incisors of the subsequent third from the bottom of the tier along with the incisors of the first. And, on the contrary, in the case of reducing the load on the face in the reverse sequence, they enter into the work, also in the reverse sequence, first together the cutters of the second and first tier and then only the cutters of the first.

The presence of shock absorbers in the form of compression springs in the cutters reduces the effect of shock loads resulting from longitudinal and transverse vibrations of the drill string and, consequently, leading to chipping of the cutters, especially diamond ones, as the most fragile ones, and, therefore, shock-absorbing springs contribute to increasing the durability of the drill crowns.

The invention is illustrated by drawings, where Figures 1, 2 and 3 schematically depict end views of two variants of a three-tier and one variant of a four-tier diamond drill bit. To simplify the drawings and their greater visibility, washing windows, slurry grooves and sealing elements are not shown. Tier numbering begins with the one closest to the face. The last number indicates the upper fixed tier of the incisors. Shown here:

figure 1 - three-tiered drill bit with three tool holders on each of two moving tiers and six tool holders on a fixed tier;

figure 2 - four-tiered drill bit with three tool holders on each of the three moving tiers and nine tool holders on a fixed tier;

figure 3 - three-tiered drill bit with two tool holders on each of two movable tiers and four tool holders cutters fixed tier;

figure 4 presents a view along aa (see figure 1) of the first embodiment of a three-tier drill bit, and figure 5 its scan (view of the outer diameter) with a local section along its average diameter.

The three-tiered drill bit (see Figs. 4 and 5) consists of an upper fixed tier of cutters 3 mounted on holders 4, which are protrusions at the end of the body of crown 5, interspersed with a minimum clearance with two lower movable tiers of cutters 1 and 2, respectively mounted on the holders 6 and 7, and the cylindrical shanks 8 of the holders, having a flat groove forming the upper 9 and lower 10 ledge and firmly connected with the holders, together with the packs of compression springs 11 resting on them, also enter the blind holes with a minimum clearance Rostia 12, made from the end face of the crown body parallel to its axis.

The compression force of the spring pack of each tier corresponds to the axial load of rock destruction, for drilling of which this tier of cutters is intended. Moreover, each subsequent upstream tier of the cutters, counting from the bottom, is intended for rocks of greater hardness than for rocks of the previous lower tier, and the cutters of the first tier from the bottom are in constant contact with the latter during drilling.

At the same time, the tool holders of the movable tiers, together with the pre-preloaded spring packs 11, are prevented from falling out of their holes due to the stop by the upper step 9 of the flat groove of the tool shanks into the upper face 13 of the support ring 14 welded from two halves, with a minimum clearance of the diameter set in the corresponding annular groove 15, made on the outer surface of the body of the crown.

The annular groove together with the support ring is protected from external influences by a metal or plastic casing 17 (not shown in Fig. 5).

When creating an axial load on the face that exceeds the limit for the cutters of the first tier from the bottom, the spring package of this tier is compressed, and simultaneously the cutters of the second tier come into operation, and with a further increase in the load on the face to a value exceeding the total maximum load of the first and the second tier of the incisors, the cylindrical shanks of the holders of the first from the bottom of the tier of the incisors, abutting with their lower ledge 10 a flat groove in the lower face 16 of the aforementioned support ring 14, raise and recess into the body of the end face of the crown p the cutters of the second tier from the bottom of the bottom, thereby ensuring the operation of the cutters of the subsequent, third from the bottom, tier along with the cutters of the first, and, conversely, in the case of a decrease in the load on the bottom in the reverse sequence, they also enter the work in the reverse sequence, first together and the first tier and then only the incisors of the first tier.

The inventive design of a multi-tiered drill bit allows you to solve the problem.

Indeed, the cutters of the first tier from the bottom face destroy the rock, provided that the axial load on the face corresponds to the compressive force of the spring package of this tier. When a harder rock is encountered and, as a result, an axial load on the face is exceeded that exceeds the limit for the cutters of this tier, the packs of its springs are compressed and the cutters of the second tier come along with the cutters of the first tier. In this case, the cutters are destroyed by the incisors of the second tier, and the incisors of the first work in self-sharpening mode. Upon encountering even harder rock and a further increase in the load on the face to a value exceeding the total ultimate load of the first and second tier of the incisors, the cylindrical shanks of the holders of the first from the bottom of the tier of the incisors, abutting their lower ledge of the flat groove 10 against the lower face 16 of the support ring 13 (Fig. .4 and 5), the incisors of the second tier from the bottom of the tier are lifted and recessed into the body of the crown end, thereby ensuring the operation of the incisors of the next, third from the bottom, tier along with the incisors of the first.

In this case, the cutters are destroyed by the incisors of the third tier, and the incisors of the first are also in the self-sharpening mode. When changing the hardness of the rocks and, accordingly, the load on the face in the reverse sequence, they also enter the work, in the reverse sequence, first together the incisors of the second and first tier and then only the incisors of the first. Thus, the use of the proposed multi-tiered drill bit, due to the versatility of the weapon kit and the possibility of including the minimum necessary weapon group that most closely matches the physicomechanical properties of the rocks passed at any given time at an unlimited frequency of their alternation, can significantly increase the efficiency of the process drilling by reducing the energy intensity of the process, increasing the mechanical speed, resource of the crown and saving time on its deputy well, particularly when drilling with a removable inner barrel

An example implementation of the proposed multi-tiered drill bit. As an example, we take a three-tiered diamond drill bit with a diameter of 75.31 mm with a wall thickness of 12.8 mm, i.e. corresponding to overall dimensions, a crown size WLN according to ISO 10097-1: 1999 (E). In these overall parameters are placed all the structural elements of a three-tier diamond crown, shown in figures 1, 4 and 5.

Drilling is carried out using a shell with a removable core receiver in rocks of the VII-XII drillability categories, including longline cutters: the first mobile - VII-IX, the second mobile - IX-XI, the third stationary - XI-XII drillability categories. Rotational speed - up to 1500 rpm.

The specific axial load is taken in accordance with the recommendations for diamond drilling (see Exploratory well drilling. Textbook for universities / N.V. Soloviev and others; under the general editorship of N.V. Soloviev. - M.: Higher school, 2007. - 2007, 904 s .; ill.), Depending on the category of rocks according to drillability, respectively, for cutters of 3 tiers (kN / cm ² ): VII-IX - 0.6-0.9; IX-XI - 0.9-1.2 and XI-XII - 1.2-1.5. Altogether, there are 12 incisors, including 3 incisors in two moving tiers and 6 incisors in a fixed one. Accordingly, the area of the working surface of the cutters, taking into account the washing windows and slurry grooves, is 4.5 cm ² in each moving tier and 9 cm ² in the fixed. According to these parameters, the axial loads on the cutters of each tier will be (kN): 1st tier - 2.7-4.05 (0.9-1.35 for one cutter); 2nd tier - 4.05-5.40 (for one cutter 1.35-1.80) and 3rd tier - 10.8-13.5 (for one cutter 1.8-2.25).

Crown incisors are represented by diamond-bearing pads soldered to the holders of all tiers of incisors, and, as conventionally shown in the schematic drawings, the higher the hardness of the rocks, the finer the diamonds. Moreover, the maximum deformation (stroke) of the spring package of the incisors of the first tier is h ₁ = 9 mm, of the second - h ₂ = 6 mm (see figure 5). As the axial load increases, the cutters of the first tier, choosing the first 2 mm of their stroke, destroy the rocks of categories VII-VIII and then, within the course of the spring course of 1 mm, the latter, together with the cutters of the second tier that come into operation, destroy the breed of the IX category . With a further increase in axial load, the cutters of the 2nd tier, within the range of their springs of 3 mm, first destroy the rock X and then, together with the cutters of the 3rd fixed tier, the rock of the XI category.

Further, the cylindrical shanks of the holders of the cutters of the 1st tier, which entered the self-sharpening mode, after a stroke of 6 mm, under the action of the increased axial force, abutting their lower ledge 9 of the flat groove in the lower face 16 of the support ring 14, tear off the cutters of the 2nd tier from and slaughter them into the crown body, making it possible for the incisors of the 3rd fixed tier to continue working to destroy rocks of the XI-XII drillability categories with a cutter load of 1.8-2.25 kN or with a total crown load of 10.8-13, 5 kN.

Thus, when the axial load on the crown changes in one direction or another, in any sequence and at any value within the specified boundaries, cutters are designed to break the rock corresponding to the given load. Obviously, this basic scheme of the crown can be used with rocks that are not only hard, but also fractured or abrasive. In this case, the armament of the crown cutters should correspond to these physical and mechanical properties of the rocks according to the purpose of each tier of the cutters.

To ensure the regime of self-sharpening and to avoid polishing diamonds of the cutters of the 1st tier of the crown, the hardness of the material of the matrix of their beads is selected in accordance with the abrasiveness of the rocks intended for destruction by the cutters of the 2nd and 3rd tier, i.e., in this case XI- XII categories of drillability.

In addition, since the cutters of the first tier are in constant contact with the bottom of the well, they can be reinforced with scoring inserts made of composite material of the type weighed, which are located directly in the diamond-bearing head with overlapping end layer, so that the complete wear of the latter can occur only after wear of the inserts of the weighed .

Taking into account the significant axial loads acting on the cutters of the moving tiers, we choose packages of Belleville springs according to GOST 3057-90 for their perception. Given the thickness of the body wall of the crown body (12.8 mm), we take spring No. 020 with an outer diameter of 8 mm, the force of which at maximum deformation is F ₃ = 400 H. The nominal diameter of the holes and cylindrical shanks of the holders is 8.3 mm

We calculate the number of springs for the first tier of the incisors. It is represented by two groups of springs: parallel and sequential assembly. With a working strain of 0.8 F ₃ = 341 N and in accordance with the maximum axial load on the cutter of the first tier (1350 H), the required number of springs of parallel assembly will be

n ₁ = 1350: 341 = 3.95,

accept n ₁ = 4 pcs.

The maximum deformation of a group of springs of parallel assembly will be

S _par. S = s ₃ = 0.17 mm,

where s ₁ - the maximum deformation of the spring No. 020.

Since the total stroke of the spring pack of the cutter of the first tier is taken equal to h ₁ = 9 mm (see figure 5), the maximum deformation of the group of springs of sequential assembly will be

S _{settlement c} = 9-0.17 = 8.83 mm.

The number of sequential assembly springs in the package is

n = 8.83: 0.17 = 51.94,

accept n = 52 pcs.

Height of a group of springs of parallel assembly in a package in a free state

$$L_{P\mathrm{but}R.\mathrm{from}}=I_o+\left(n_{\mathrm{one}}-\mathrm{one}\right)t,\left(\mathrm{one}\right)$$

where I ₀ is the height of the spring, mm;

t is the thickness of the spring, mm;

L _par . _S = 0.67 + (4-1) 0.5 = 2.17 mm.

Free spring group height

L _{settlement c} = I ₀ × n = 0.67 × 52 = 34.84 mm.

Total height of the spring pack in the free state

2.17 + 34.84 = 37.00 mm.

The total height of the spring pack of the cutter of the first tier with a preliminary deformation of 0.2 F ₃ (with preload during installation) will be

37-37 × 0.2 = 29.60 mm.

Similarly for the cutter of the second tier we get: the required number of a group of springs of parallel assembly n ₁ = 1800: 341 = 5.2; accept n ₁ = 5 pcs.; S _par. S = 0.17 mm; since the maximum deformation of the spring package is taken equal to h ₂ = 6 mm (see Fig. 5), the total stroke of the group of springs of sequential assembly will be equal to S _pos = 6-0.17 = 5.83 mm; then n = 5.83: 0.17 = 34.29, take n = 34 pcs.;

L _par.s = 0.67 + (5-1) 0.5 = 2.67 mm; L _pos.s = 0.67 × 34 = 22.78 mm; the total height of the spring pack of the cutter of the second tier in the free state is 22.78 + 2.67 = 25.45 mm; the same with preliminary deformation of 0.2 F ₃ will be 25.45-25.45 × 0.2 = 20.36 mm.

We check the strength of the body of the crown, which, at the junctions of the cylindrical shank of the holder of the movable cutter with the wall of the hole, experiences shear stress from the action of the peripheral rotation force when the rock is destroyed at the bottom. As the material for the body of the crown we take steel 35 with a yield strength of 294 N / mm ² .

The maximum stresses occur in the holes of the second tier of the cutters, in which the maximum axial force at the bottom is 5.4 kN. First, we determine the power consumption for the rotation of a conventional diamond core from the following relationship (see the Reference Manual of an Exploration Drilling Engineer: In 2 Volumes / Edited by Prof. EA Kozlovsky. - Volume 2-M .: Nedra, 1984, 437 p.):

$$N=0.81\times {10}^{-8}P\times n_{\mathrm{at}R}\left(D_n+D_{\mathrm{at}}\right),\left(2\right)$$

where P is the axial load on the crown, H;

n _BP - crown rotation frequency, rpm;

D _n - the outer diameter of the crown, mm;

D _in - the inner diameter of the crown, mm

Since P = 5400 P; n _BP = 1500 rpm; D _n = 75.31 mm; D _in = 47.62 mm, we have

N = 0.81 × 10 ⁻⁸ × 5400 × 1500 (75.31 + 47.62) = 8.1 kW.

Of the 12 incisors, only 3 are involved in the work, i.e. 25% of the total area of the end face of a conventional crown, and, therefore, the cost of power, respectively, will be

8.1 × 0.25 = 2.0 kW.

Then the torque on the crown

M _cr = 9552 × 2.0: 1500 = 12.7 Nm.

Given that the radius of the drill bit is

R = 75.31: 2: 1000 = 0.0376 m,

and that 3 cutters work simultaneously, we find the calculated circumferential force per one cutter

q _res.r = M _cr : R: 3 = 12.7: 0.0376: 3 = 112.5 H.

The area S _{from the} inner surface of the hole with a diameter of d = 8.3 mm, perceiving the lateral load of collapse will be equal to:

$$S_{\mathrm{about}t}=3.14\times d\times n:2\left(3\right)$$

where h is the mating height of the cylindrical shank with the lower edge of the inner surface of the hole associated with its bias, the value of which depends on the gap between the hole and the cylindrical shaft of the holder. Given that the cylindrical shank enters the hole with a minimum clearance (for example, along a sliding fit), we take the value h = 0.2 mm. Then:

S _from = 3.14 × 8.3 × 0.2: 2 = 2.60 mm ² ,

and the crushing stress will be equal

112.5: 2.60 = 43.25 N / mm ² .

With a shear load, the permissible stress for steel 35 will be 294 × 2.25 = 662 N / mm ² , where 294 is the yield strength of steel 35, N / mm ² , and the margin of safety of the body of the crown body for shearing will be equal to

662: 43.25 = 15.3,

which is enough.

We check for crushing the material of the support ring and the ledge of the flat groove of the cylindrical shank of the toolholder of the first tier cutter from the action of the axial load on the face. The maximum load occurs in the conjugation of these two elements of the crown during the joint work of the first and third tier of the incisors, when the load on the incisor of the first tier is the total load of the incisor of the first and second tier, i.e.:

1.35 + 1.8 = 3.15 kN = 3150 H.

The reference area of the ledge of the flat groove of the cylindrical shaft at the contact with the face of the support ring (see Fig. 4) is 40% of the total cross-sectional area of the shaft:

S _op = 0.785 × 8.3 ² × 0.4 = 21.6 mm ² .

The shear stress of the ledge of the flat groove of the cylindrical shank and the mating surface of the support ring will be

3150: 21.6 = 146 N / mm ² ,

and the margin of safety, taking into account the permissible stress for steel 35, will be equal to

662: 146 = 4.5,

which is enough.

The given example of the implementation of the proposed design of a multi-tiered drill bit with optimal parameters of the drilling mode and taking into account the real loads perceived by the most critical structural elements during the destruction of the face showed its performance and high strength according to its purpose.

The use of such a drill bit will significantly increase its resource and mechanical speed, reduce the energy consumption of the drilling process and significantly reduce the time required for tripping to replace it.

Claims (1)

A multi-tiered drill bit, including several tiers of cutters located at different distances from the bottom of the well, characterized in that the upper fixed tier of the cutters is mounted on their holders, which are protrusions at the end face of the crown body, interspersed with a minimum clearance with holders of several lower movable tiers of the cutters, moreover, the cylindrical shanks of the holders, having a flat groove forming the upper and lower ledge, and firmly connected with the holders, together with the packages of compression springs resting on them, also enter with a minimum clearance, into blind holes made from the end face of the crown body parallel to its axis, and the compression force of the spring pack of each tier corresponds to the axial load of rock destruction for drilling of which this tier of cutters is intended, and each subsequent upstream tier of cutters, counting from the bottom , is intended for rocks of greater hardness than for rocks of the previous lower tier, and the cutters of the first tier from the bottom are in constant contact with the latter during drilling, at the same time, the holders of the cutters of moving tiers together with pre-pressed spring packs are kept from falling out of their holes due to the stop of the flat groove of the cylindrical shanks of the holders against the upper edge of the support ring welded from two halves, with a minimum gap in diameter installed in the corresponding annular groove made on the outer surface of the crown body, moreover, when creating an axial load on the face that exceeds the limit for the cutters of the first tier from the bottom, the spring pack of this tier is compressed, and simultaneously with its cutters in p cutters of the second tier start working, and with a further increase in the load on the face to a value exceeding the total ultimate load of the first and second tier of the cutters, the cylindrical shanks of the holders of the first from the bottom of the tier of cutters, resting with their lower ledge on a flat groove in the lower face of the mentioned support ring, raise and the incisors of the second from the bottom of the tier are recessed into the body of the end face of the crown, thereby ensuring the operation of the incisors of the next, third from the bottom, tier along with the incisors of the first, and, conversely, in the case of reduced load and the slaughter in the reverse sequence, they enter into the work, also in the reverse sequence, first together the incisors of the second and first tier, and, then, only the incisors of the first.

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