RU2373368C2 - Thermal-friction rock-breaking tool - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention is related to rock-breaking tool used in tunneling of geological survey wells, and may be used in all combined methods for breaking of rocks, by heating that reduces strength of rock surface layer. Thermomechanical rock-breaking tool comprises body, friction elements, which heat and reduce strength of rock surface layer through friction, cutters and pressing element made of metal rubber. At the same time body is made of two welded parts, material of which has various limits of strength. Besides friction elements are connected to part of body made from material with low strength limit, and cutters are movably installed together with pressing element in cavity of material with high strength limit, moreover, cutters protrude above plane of friction elements. Material of pressing element is a microporous nanocomposite material with elasticity module of 10²-10³ MPa.

EFFECT: improved efficiency of well drilling.

2 cl, 3 dwg

Description

The invention relates to mining, and in particular to drilling equipment used for drilling exploration wells, and can also be used in all thermofriction methods of drilling, by the friction heat softening the surface layer of the rock.

A single thermomechanical combined crown is known in which cylindrical columns made of an alloy with shape memory with a diameter of 3.0-4.5 mm and a height of 5-10 mm, which are placed in the cylindrical channels of the housing, without causing a significant decrease in its reliability, are used as a drive for cutters [1]. To prevent the loss of incisors, a special locking device is used. During drilling, the alloy, heating up and remembering its predetermined shape, presses the cutter into the softened rock, which cuts this layer when the crown rotates. The advantage of this crown is force contact with the rock when it softens. This makes it possible to drill rocks of high strength, softened by heating. A significant drawback of this crown is the limited (0.2-0.4 mm) depth of indentation of the incisors into the rock, although the recovery rate of the alloy shape is 8-10%. This is explained by the fact that the more the specified size of the alloy is restored, the less the force of pressing in the cutter. An increase in the depth of indentation of incisors into the rock due to an increase in the length of a cylindrical column with a diameter of 3.0–4.5 mm to 15–20 mm leads to a loss of stability when compressed. Those. the alignment and parallelism of the planes of the end face of the drive of the cutters are violated, which leads to shapeless deformation and a decrease in the depth of indentation of the cutters into the rock. The increase in the diameter of the cylindrical drive to increase its stability is limited by the wall thickness of the single crown housing. When drilling hard rocks, a thin layer of rock removed by the cutter is normal, but when drilling medium hard formations it limits the drilling speed. An increase in the rotation speed of the crown to achieve the required drilling speed is unacceptable due to a decrease in the time of heating the rock with friction elements. Another disadvantage of this crown is the low strength of its body, weakened by axial channels. Because of this, the reliability of the crown decreases under abnormal drilling conditions, for example, when drilling core in a well or at the bottom.

Also known is a thermomechanical rock cutting tool for drilling exploration wells with a single pipe with constantly protruding cutters [2]. The crown consists of friction elements, softening the surface layer of rock, and protruding cutters, cutting off this softened layer by heat of friction. The advantage of this crown is the possibility of thermomechanical drilling with softening of the rock with simplicity of design, high reliability when drilling rocks of medium hardness. A significant drawback is the limited possibility of thermofriction drilling of hard rocks due to protruding cutters, which must be introduced into the unstressed rock layer at the beginning of drilling ahead of schedule. Only then will the friction elements come into contact with the face and soften the rock.

The closest in technical essence is a thermomechanical rock cutting tool, the body of which consists of two parts along the length, the material of which has different elastic moduli, and therefore, different tensile strengths. In this case, a part of the body made of a material with a large modulus of elasticity is connected to the cutter elements, and a part of the body made of a material with a lower modulus of elasticity is connected to abrasive friction elements [3]. In this crown, a material with a lower modulus of elasticity serves as a pressure member for the friction element. When an axial load acts on the crown, the cutter and friction elements simultaneously come into contact with the face. In this case, the cutter elements are introduced into the unstressed rock under the action of a part of the axial force, and the friction elements due to the elastic forces of the part of the crown ring with a lower elastic modulus (pressure element) by friction heat and soften the rock. Then, after some time, the upper layer, into which the cutter has penetrated, softens from the friction of the friction elements, is separated by the cutter and is removed by the washing liquid.

The advantage of this crown is the simplicity of design and the possibility of drilling with softening the surface layer of the rock.

A significant drawback of this crown is a significant decrease in the strength of part of the crown with a lower modulus of elasticity, which constitutes at least 80-85% in the section of the crown body. The moment of rotation is transmitted to the friction elements through metal rubber with an elastic modulus that is 10 ² -10 ³ times less than steel, whose elastic modulus is 2 · 10 ⁵ MPa. In isotropic materials, the shear modulus directly depends on the modulus of elasticity; therefore, it is also possible to transmit a rotational moment through metal rubber that is 10 ² -10 ³ less than through steel. This significantly reduces the reliability of the crown during dynamic torsional vibrations of drill pipes, when drilling with a large torsion moment, when lowering the projectile, when there is no core in the well, when reaching the bottom through the rubble and under other abnormal or forced drilling conditions.

Significant disadvantages should also include the limited possibility of thermofriction drilling of hard rocks due to the need for faster introduction of cutters into the unstressed rock layer. This requires at the beginning of drilling an axial load that is significantly higher than optimal, so that the cutters penetrate into the unstressed rock and the friction elements heat the rock before softening. Moreover, the more it is necessary to transmit the axial force to the friction elements, the more the cutters must penetrate into the rock. Only then, at the contact of the friction elements with the rock, sufficient friction forces will arise that will heat the rock. It should also be noted that when the tool elements are worn or broken due to the low technological soldering of the tools, their replacement with new tools is almost impossible. In addition, the rigidity of the metal rubber in the crown corresponds to the rocks of the same hardness, for other rocks another crown is selected, since the replacement of the pressure element is impossible.

Thus, the task can be set to safely transfer significant loads to the friction elements of the crown and equip the tool with removable cutters and pressure elements.

These problems can be solved if in the crown, the body of which consists of two welded parts along the length, the material of which has different strength limits, and at the same time the friction elements are connected to the part of the crown body made of the material of the crown body with a lower tensile strength, and cutter the elements based on the pressure elements to install movably in a recess made in part of a material with a high tensile strength, and the cutters should protrude above the plane of the friction elements.

To impart mobility to the cutters in the axial direction, the vertical walls of the recess in the part of the crown body with a large tensile strength have grooves, and the tool holder has reciprocal protrusions and mate along the slip fit. To prevent from falling out, the cutters have soldered or welded or galvanically connected locks. Moreover, the material of the locks should not be hardened after welding, which should be carried out by electrodes that do not strengthen the seam, and soldering can also be carried out by low-temperature solders, since the locks, like the cutters, are washed with water. To change the cutters or the pressure element, the locks are sawn off or unsoldered, then new locks are again soldered or welded in the same place.

In the proposed device, about 80% of the end face of the crown in the cross section is represented by material, albeit with a lower tensile strength, but by the material of the crown body itself, which accepts the greatest axial and torque loads under normal and abnormal conditions of drilling, lowering and raising the projectile. The protruding cutters mounted movably supported by an elastic pressing element, when loaded with axial force, are buried behind the plane of the friction elements and perceive loads only within the elasticity of the pressing element. Due to this, the main part of the shock and critical loads will be perceived by the crown body. However, when drilling is inevitable, various cases of complex loading of the cutters and their execution by moving implies special requirements for the strength of this connection. In this regard, the toolholder and part of the crown body with a large tensile strength (2500-3600 MPa) are made of maraging steel, which are well welded and brazed, and have a tensile strength 4-6 times higher than the strength of the crown body ( 400-500 MPa). For normal operation of the crown, it is necessary that when drilling rocks of X-XI categories for drillability, cutters should not be embedded in the rock. For this, the elastic modulus of the pressing element should not exceed 10 ³ MPa, and in order to ensure a corresponding depression in the softened rock with a force of at least 0.50-1.5 kN per cutter, the elastic modulus should be at least 10 ² MPa.

All this makes the crown more reliable in operation, while retaining all the advantages of the prototype. In the known crown [2], the incisors protrude constantly, which makes the crown applicable only in rocks of medium hardness. The proposed crown can work in thermobored rocks of any hardness.

All this suggests that the proposed device has a novelty and inventive level.

The proposed device has the following advantages compared to the prototype:

- it becomes possible to transfer significant loads to the friction elements, ensuring optimal softening of the rock;

- the ability to drill heat-drillable rocks of any strength;

- the ability to replace the cutters when they are worn or broken;

- the ability to replace the pressure elements depending on the properties of the drill;

- increases the impact resistance of the cutters when landing the crown on the face due to the damping properties of the elastic support;

- it is possible to use elbor, hexanite and dense boron nitride as cutters due to the damping properties of the elastic support.

The present invention can be implemented, in addition to the crown described above, in the form of a blade and diamond sector bits for drilling explosive and oil wells, respectively.

In figure 1. shows a general view of the crown; figure 2 is the same, bottom view; figure 3 is the same, a section along aa.

The crown has a housing 1, consisting of two parts 2 and 3, the material of which has different strengths, a pressure element 4 of metal rubber, friction elements 5, cutters 6 and locks 7. Part 3 of the housing 1, made of a material with a large tensile strength, is welded to part 2 and has a recess 8, the vertical walls of which have grooves 9, and the holder 10 of the cutter 6 has reciprocal protrusions 11. Moreover, the grooves 9 and protrusions 11 are conjugated along the sliding fit.

To prevent from falling out, the cutters have soldered or welded locks. It is possible to connect the locks to the case mechanically and galvanically. Moreover, depending on the temperature resistance of the pressing element, it can also be soldered with low-temperature solders, and parts 2 and 3 of the housing 1 should be welded with electrodes that do not reinforce the seam. To change the cutters or pressure element, the lock is sawn off or soldered. After installing another pressing element or cutter, another lock is soldered or welded to the friction element or to part 2 of the crown body. Flushing channels are formed due to reduced outer and inner diameters of the toolholder of the cutters, pressure elements 4 and a special cut-out in part 3 of the housing 1 in accordance with the diameters of the crown body.

The crown works as follows. After setting the necessary axial load, the pressing element 4 is compressed, the cutters 6 are axially displaced relative to the friction elements 5, as a result of which the latter also come into contact with the face. In this case, the cutters are not embedded in the rock, since the elastic force of the pressure elements is insufficient for the introduction of the cutters into the unstressed solid rock. When the axial force and the number of revolutions of the crown is reached optimal values, the surface layer of the rock from heating by friction elements 5 will soften. Then the cutters 6 under the action of the elastic forces of the pressing element 4 will be embedded in this layer until the elastic forces are balanced by the forces of the rock resistance to the introduction of the incisors. With further rotation of the crown, the cutters will cut off this softened layer, which is removed by the washing liquid.

When drilling rocks of medium and lower than average strength with crowns for drilling rocks of high hardness, the cutters under the action of the elastic forces of the pressing element 4 will slightly penetrate into the rock. At the same time, the friction elements will come into contact with the face and will soften the surface layer of the rock, and after softening, the cutters will even more penetrate the face and remove the more powerful layer of the rock. However, metal rubber with a large modulus of elasticity has a lower elastic deformation, so the cutters will cut a deliberately insignificant layer. Therefore, for drilling rocks of medium and lower than average strength should be drilled with a crown, in which the pressure element has a large elastic deformation. Then the elastic part of the crown body to press the cutter to a greater depth and the drilling speed will be higher. And for this, in the crown for hard rocks, it is necessary to replace the cutters and pressure elements intended for rocks of medium hardness.

Consider a concrete example of the possibility of placing at least two push and at least two friction elements on the crown body with a diameter of 76 mm with a perimeter of 210 mm, determined by the average diameter of the crown. According to the condition of heat generation, the length of the friction elements should be at least 60-70 mm, then the length of the pressure elements should be no more than 35 mm with a two-friction crown, and no more than 15 mm with a three-friction crown. We calculate the length of the pressure element that inscribes a crown with a diameter of 76 mm into the geometric parameters. The elastic modulus of the material of the pressure element is taken, as in the prototype, on average equal to E = 5 · 10 ² MPa. Let the elastically deformable crown pressing element have the form of a parallelepiped with the following linear dimensions: height h = 10 · 10 ^-3 m, length b to be calculated, width a = 6 · 10 ³ m, then the cross-sectional area of the pressing element S = a × b . When drilling rocks of category VI-VII for drillability with carbide crowns, the load on one cutter in the range 0.4-1.0 kN is accepted [4], we take the necessary axial force on the cutter equal to 2.0 kN, bearing in mind that the cutter blade must be with a preliminary blunt pad to increase its wear resistance. Then the elastic force P of the pressure element should also be equal to 2.0 kN. Take the preliminary release of the cutters Δh = 0.4 · 10 ^-3 m

We calculate from these data by the formula. It is known from the theory of elasticity that in an elastic body, the stress σ is directly proportional to the modulus of elasticity and relative deformation Δh / h, and σ is by definition equal to P / S. Then we have

P / S = E · Δh / h; substitute the value of S, we get P / a · b = E · Δh / h. From here we find the length of the pressure element that ensures the introduction of the cutter into the softened rock:

b = P · h / Δh · E · a.

We substitute the numerical values of the input symbols: b = 2 · 10 ³ × 10 · 10 ^-3 /0.4 · 10 ^-3 × 5 · 10 ⁸ × 6 · 10 ^-3 = 17 · 10 ^-3 m.

Thus, an approximate calculation with the above data shows that the required length of the pressing element is less than the maximum allowable for reasons of geometric placement on the crown ring of the crown body. It follows that the crown with a diameter of 76 mm can be made two-friction; for the manufacture of a three-friction crown, it is necessary to apply a pressure element with a large modulus of elasticity. A crown with a diameter of 59 mm has an average diameter of 158 mm, and it can also be made two-friction, since the sum of the lengths of all pressure and friction elements (154 mm) is less than the perimeter of the crown ring of the crown.

Information sources

1. Pat.2247216 C2 Russian Federation, IPC ⁷ ЕВВ 10/46, 7/14.

Thermomechanical rock cutting tool [Text] / Ermakov S.A., Fedorov L.N .; Applicant and patent holder Yakutsk, Institute of Mining of the North SB RAS (RU). - No. 2003108844/03; declared 03/31/2003; publ. 02/27/2005, Bull. No. 6. - 5 s: ill.

2. Pat. 2247217 C2 Russian Federation, IPC ⁷ Е21В 10/46, 7/14. Thermomechanical rock cutting tool [Text] / Brodov GS, Ermakov SA, Fedorov L.N .; Applicant and patent holder Yakutsk, Institute of Mining of the North SB RAS (RU). - No. 2003111120/03; declared 17.04.2003; publ. 02.27. 2005, Bull. No. 6. - 6 p.: Ill.

3. A.S. 505801 USSR, M. Cl. ² Е21С 21/00; E21C 13/02; E21C 37/16. Thermomechanical rock cutting tool [Text] / EF Epstein, AM Brazhenenko, A. A. Kozhevnikov, V. F. Sirik, P. P. Vyrvinsky, I. A. Baskilovich, F. M. Krasnovsky and M. E. Grenadier (THE USSR). - No. 1923704 / 22-3; declared 05/22/73; publ. 03/05/76, Bull. No. 9. - 2 s: ill.

4. Ganjumyan R.A. Practical calculations in exploratory drilling [Text] / R.A. Ganjumyan. - M .: Nedra, 1986.- 254 p.

Claims (2)

1. Thermofriction rock cutting tool, comprising a housing consisting of two welded parts along the length, the material of which has different tensile strengths, friction elements heating and softening the surface layer of rock by friction, cutters separating this layer, and a pressure member made of metal rubber, characterized the fact that the friction elements are connected to a part of the crown body made of material of the body of the crown with a lower tensile strength, and the cutting elements are movably mounted together with the pressure e element in the recess in parts of a material with a large tensile strength, and the cutters protrude above the plane of the friction elements. 2. The tool according to claim 1, characterized in that the microporous nanocomposite material with an elastic modulus of 10 ² -10 ³ MPa is used as the material of the pressing element.

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