RU2773749C1 - Pdc drill bit with rotating cutters - Google Patents

Abstract

FIELD: petroleum industry.

SUBSTANCE: invention relates to a tool for drilling petroleum and gas boreholes. PDC drill bit with rotating cutters includes a steel body with protruding blades, washing assembling located in grooves between the blades, a nipple part with a thread for attachment to the drill string, and holes on the surfaces of the blades with rotating diamond cutters placed therein. A joint annular cavity is made on the walls of the cutter holes and on the walls of the hard-alloy substrates of the cutters, at the same distance from the bottom of the hole and from the end of the incisor, wherein a locking elastic ring is installed. The joint annular cavity has an oval cross-sectional shape. The joint annular cavity is formed by the half-groove in the form of an annular cavity on the wall of the cutter hole and the half-groove in the form of an annular cavity on the wall of the hard-alloy cutter substrate. A chamfer is made at the end of the cutter, configured to compress the part of the elastic locking ring protruding from the annular cavity on the wall of the cutter hole when the cutter is installed. The locking elastic ring is made of rubber and has a cross-section matching the cross-section of the entire joint cavity. The weight of part of the ring enclosed in the annular cavity on the wall of the cutter hole is greater than the weight of part of the ring enclosed in the annular cavity on the wall of the hard-alloy cutter substrate. The cutting planes of cutter plates are inclined relative to the plane extending through the centre of the plate and the axis of the drill bit at an acute angle, configured for guaranteed formation of the moment of rotation of the cutters relative to the axes thereof and cutting of the rock at the bottom-hole consecutively using the entire length of the cutting edge.

EFFECT: increase in the durability of PDC cutters, headway per bit, and drilling rate.

1 cl, 5 dwg

Description

The present invention relates to a tool for drilling wells for oil and gas.

The 2000s are characterized by the beginning of widespread use in deep drilling both in our country and abroad of coneless bits of the PDC (Polycristalline Diamond Cutter) cutting type. These bits are equipped with a new type of round diamond cutting inserts. They consist of a single crystal of diamond, artificially grown from diamond powder, under truly extreme conditions - a pressure of 1 million pounds per square inch, created on a six-position press, at temperatures up to 3000 degrees Fahrenheit, over a period of time of about a day. This very complex technology was developed by General Electric (USA) for more than 50 years and became known in 1954.

Fine-grained diamond powders are used as the starting material for growing a single crystal. A single crystal grown from them has many times higher strength properties and heat resistance. This is due to the absence of intercrystalline boundaries in a single crystal and the composition cementing these boundaries, which are constantly present in natural and artificial diamonds. These unique properties of the crystals are used to make diamond cutters in PDC bits. Today, PDC bits equipped with such cutters are widely and successfully used in domestic and foreign drilling of deep wells, in rocks from the softest to hard, low-abrasive ones.

The above technology for growing individual diamond crystals provides for the production of relatively small plates with diameters from 8 to 24 mm. and 1.5 - 2.5 mm thick. Such plates with a flat cutting surface are welded or soldered onto carbide cylindrical bases - substrates of the same diameter as the plates. With the help of this substrate, finished PDC cutters are fixed in the holes on the body of blades of steel or matrix bit bodies. Possessing unique strength properties during abrasion, diamond plates are quite brittle and poorly absorb shock loads.

Therefore, the method of fastening carbide teeth into the cone holes, traditional for cone bits, by pressing with a multi-ton pressing force, is not applied to them. Fastening of the PDC cutters in the holes of the blades is ensured by soldering with gentle temperature heating (up to 650 degrees Celsius) with PSR solder on a silver base.

Known bit PDC with diamond cutters [1], adopted as an analogue in our application. The introduction of such bits made it possible to increase the average penetration per bit up to ten times compared to traditional cone bits, to bring their use in deep drilling to 70% of its volume and to obtain a very large economic effect. However, these high-performance bits also have their weaknesses. This is the fragility and relatively low resistance of diamond plates when they meet interlayers of hard and strong rocks. Replacing the rolling friction of cutters along the bottom with cutting during the destruction of the rock led to the need to purchase new, more powerful drilling equipment to provide many times more torque during drilling. There was a danger of overheating of the cutting edge during many hours of continuous operation of PDC bits at the bottom.

Known bit PDC [2], which links the depth of cut of the bit in one revolution with a controlled axial load on the bit, allowing to reduce the occurrence of overheating of the cutting edge of the cutters. This bit is taken as the second analogue in our application. The solutions proposed in this patent were not widely used in PDC bits, since they were valid only for rock samples determined by hardness and could not be universal for many rocks of different hardness that were passed by PDC bits in one run.

Another PDC bit [3] is known, taken as the next analogue in our application. In this analog, the increase in drilling performance is ensured due to the maintainability and reuse of the repaired bit after replacing the position of the worn or dull part of the cutting edge of the PDC cutter directly in drilling conditions, while eliminating the previously inevitable harmful effect on the decrease in the resistance of three-fold heating of the PDC cutters during the repair replacement of the position of their cutting edge. edges. In accordance with this patent, instead of soldering, the PDC cutters are fixed by mechanical fastening of the cutters in the desired position using a pair of locking bushes inserted into each other with conical reciprocal cones made of ductile steel. After lifting the bit and preparing it for repair, the PDC cutters are easily knocked out of their sockets with a special punch by blows from the non-working end of the cutter. After the cutter is knocked out of the socket, the working edge is turned to the desired position of its not yet working part, and the cutter is again fixed by driving a pair of conical bushings.

The maintainability of PDC bits, carried out both with and without soldering, allows you to repeatedly use these very expensive products, the cost of which is estimated at millions of rubles, dramatically increasing the efficiency of their use in drilling.

But, progress in the production of drilling tools is constantly moving forward, more and more new design solutions appear that provide even higher achievements in the field of deep drilling.

One of the world's leading manufacturers of drilling tools in the United States, Smith Beats, part of the Schlumberger Corporation, published a promotional presentation for Russian drillers in Russian, one of the sections of which is entitled "The new revolution in the durability of PDC cutters", in which reported on the creation of a rotating PDC cutter in the bits of this company ONYX 360. The number 360 in the designation of the bit corresponds to the possibility of continuous rotation of the cutting edge of the PDC cutter during drilling around its axis by 360 degrees [4]. This presentation contains little or no specific design features that allow circular rotation of the PDC cutter while drilling, but it does present a computer model of the contact loading of the rock under the cutting edge of the PDC cutter and mentions the significant benefits of rotating the cutter during operation, in which more than one individual is subjected to loading. a limited section, but the entire length of the cutting edge, instead of its separate section, which works in the case of a rigid fixing of the cutter. The use of samples of ONYX 360 bits provided an increase in average penetration by 57%.

The bit with a rotary cutter ONYX 360 is accepted in our application as a prototype.

The purpose of the present invention is to increase the durability of the cutters, the reliability and performance of PDC bits, as well as to simplify the technology of their manufacture.

This goal is achieved by the fact that the proposed bit includes a steel body with protruding blades, flushing units located in the grooves between the blades, a nipple part with a thread for attaching to the drill string, holes on the surfaces of the blades with PDC rotating diamond cutters placed in them, for which on the walls of the holes for the cutters and on the walls of the substrates of the cutters, at the same distance from the bottom of the hole and from the end of the cutter, a joint annular cavity is made, which has a curvilinear or rectilinear shape in cross section, for example, oval, in which a locking elastic ring with a cross section corresponding to the cross section is installed joint annular cavity. At the same time, the mass of the part of the ring enclosed in the annular cavities on the walls of the holes for the cutters is more than the mass of the part of the ring enclosed in the annular cavities on the walls of the substrates for the cutters, and the planes of the PDC cutter plates relating to the bottom by the cutting edges, to ensure their forced rotation during drilling, can be inclined relative to the plane passing through the center of the plate and the axis of the bit at an acute angle, with the possibility of guaranteed formation of the moment of rotation of the cutters relative to their axes and cutting the rock at the bottomhole consistently with the entire length of the cutting edge.

LIST OF DRAWINGS.

The invention is illustrated by drawings, in which FIG. 1 shows a general view of the PDC bit, FIG. 2 is a bottom view of the bit with a section A - A of the body with one of the cutters with a locking device, FIG. 3 - an enlarged node along the longitudinal section A - A and the place of the cross section of the cutter B - B along the retaining ring, Fig. 4 is a diagram of the location and installation of the locking device, FIG. 5 - section B - B along the retaining elastic ring and the joint annular cavity.

In FIG. 1 positions indicate: 1 - bit body, 2 - PDC cutters, destroying rock at the bottomhole, 3 - PDC cutters, protecting the bit body from loss of diameter when drilling a well, 4 - body blade, 5 - cavities to ensure bottomhole flushing from cuttings, 6 - grooves on the body for "screwing - unscrewing" the bit when it is fastened, 7 - conical thread for connecting the bit to the drill string.

In FIG. 2 the elements shown in FIG. 1, as well as the following positions are indicated: 8 - flushing units, 9 - diametrical surfaces of the bit, as well as the direction of the section A - A passing through the symmetry plane of the joint annular cavity for one of the PDC cutters.

In FIG. 3 the elements shown in FIG. 1 and FIG. 2, as well as the following positions are indicated: 10 - retaining elastic ring, 11 - annular half-groove on the wall of the hole 13 for installing the PDC cutter, 12 - annular half-groove on the wall of the carbide substrate of the cutter 2; 13 - wall of the hole for the installation of the cutter 2 in the blade 4; 14 - the bottom of the hole for the installation of the cutter 2. The letter "a" denotes the same distance from the bottom of the hole and from the end of the cutter to the joint annular cavity.

In FIG. 4, the same positions indicate the elements shown in the previous figures 1 - 3, and the distance "a" is also indicated.

In FIG. 5, which shows the section B - B, the same positions indicate the elements shown in the previous figures 1 - 4, as well as the letters D1 - the maximum diameter of the half-groove 11 in the wall of the hole and D2 - the minimum diameter of the half-groove 12 in the wall of the cutter substrate.

To eliminate obstacles to the constant rotation of the PDC cutter during drilling and reduce friction when the elements of the lock assembly come into contact with each other, the following conditions must be met. As a material for manufacturing, it is necessary to use an elastic and sufficiently resistant material, for example, special grades of rubber, which make it possible to assemble the locking assembly and its long-term abrasion resistance. To increase wear resistance, the elastic stop can be treated with any known anti-friction coatings, for example, those containing molybdenum disulfide. To ensure guaranteed forced rotation of the cutters around their axes during drilling, the cutting planes of the PDC cutter inserts that touch the bottom can be tilted relative to the plane passing through the center of the insert and the bit axis at an acute angle, within the recommended limits, for example, from 5 to 15 degrees clockwise arrow or against it. The friction forces arising from the slipping of the cutter edges along the bottomhole guarantee the formation of the necessary moment of cutter rotation relative to their axes and rock cutting at the bottomhole, consistently throughout the entire length of the cutting edge of the diamond plate.

Installation of an annular retaining elastic ring 10 in a joint annular cavity formed by half-grooves 11 and 12 is carried out as follows. As a starting material, as mentioned above, for the manufacture of a retaining elastic ring, rubber is selected, for example, a damper type. Depending on the dimensions of the cutter, for which the retaining ring is designed and manufactured by sintering, its dimensions are assigned, as well as the required dimensions for making half-grooves 11 and 12.

The finished retaining elastic ring is placed in the half-groove 11. Then the cutter 2 with a lead-in chamfer coated with anti-friction lubricant, made in the form of an acute angle and with an inlet diameter slightly smaller than the inner diameter of the hole partially protruding into the cavity for the cutter of the retaining elastic ring, is inserted with force into the hole for installation, as shown in Fig. 4. Since the mass of the retaining elastic ring protruding into the hole for installing the cutter is much less than its total elastic mass enclosed outside the wall of the hole, and therefore has a large margin of elasticity, the surface of the chamfer of the cutter body when it is installed gradually squeezes the protruding part of the elastic lock ring and temporarily pushes it outside the wall of the hole. As soon as the half-groove 12 on the substrate wall is equal to the half-groove 11 on the wall of the hole for the cutter, its cavity is filled with an elastic material due to the elastic properties of the ring material, which becomes a locking obstacle for the cutter from its axial movement, but cannot prevent its rotation.

When drilling, the entire axial load on each rock cutting cutter is taken from the end of the cutter by the bottom of the hole in the blade. This means that only the forces that push it deep into the hole act on the cutter, and there are practically no forces pulling it out of the nest, except for the force of its own weight, which occurs only when the bit is raised above the bottom. Therefore, the durability of the locking device directly depends only on the resistance of the material of the elastic retaining ring to abrasion and can be calculated in many tens of hours.

The present invention makes it possible to significantly improve the performance of PDC diamond bits and simplify their manufacturing technology.

SOURCES OF INFORMATION.

1. "Diamond Chisel", "FD Line". Catalog of drill bits of JSC "Volgaburmash", 2003. С 34-3.

2. "Drill bit with controlled depth of cut and load", US patent No. 6298930, class. E21B 10/46. 2001.

3. Bogomolov R.M., Grinev A.M., Krylov S.M. etc. "Diamond chisel with mechanical fastening of cutters", patent of the Russian Federation No. 2536901 class. E21B 10/573, F21C 35/197.2014.

4. Creation and application in various areas of drilling of rotating cutters. "The New Revolution in PDC Cutter Durability", Smith Beats (USA), Schlumberger Corporation, 2013.

Claims (1)

PDC drill bit with rotating cutters, including a steel body with protruding blades, flushing units located in the grooves between the blades, a nipple part with a thread for attaching to the drill string, holes on the surfaces of the blades with rotating diamond cutters placed in them, characterized in that on on the walls of the holes for the cutters and on the walls of the hard-alloy substrates of the cutters, at the same distance from the bottom of the hole and from the end of the cutter, a joint annular cavity is made, in which a locking elastic ring is installed, the joint annular cavity has an oval shape in cross section, while the joint annular cavity is formed by a half-groove in in the form of an annular cavity on the wall of the hole for the cutter and a half-groove in the form of an annular cavity on the wall of the carbide substrate of the cutter, a chamfer is made on the end of the cutter with the possibility of squeezing the part of the elastic locking ring protruding from the annular cavity on the wall of the hole for the cutter when installing the cutter, stopper The second elastic ring is made of rubber and has a cross section corresponding to the cross section of the entire joint cavity, while the mass of the part of the ring enclosed in the annular cavity on the wall of the hole for the cutter is greater than the mass of the part of the ring enclosed in the annular cavity on the wall of the carbide substrate of the cutter, with In this case, the cutting planes of the cutter plates are inclined relative to the plane passing through the center of the plate and the axis of the bit, at an acute angle with the possibility of guaranteed formation of the moment of rotation of the cutters relative to their axes and cutting the rock at the bottomhole consistently with the entire length of the cutting edge.

Images