CN1452685A - Drill bit - Google Patents

Abstract

The invention relates to a rotary drill bit for drilling a borehole in an earth formation, the drill bit comprising a first and a second disc cutter, each disc cutter being arranged to roll along the borehole bottom during rotation of the drill bit and thereby to cut respective first and second substantially circular, radially spaced cuts in the borehole bottom so that a body of rock material is defined between said cuts. The second disc cutter is arranged to cut into the bottom of the borehole at a selected rotational interval of the drill bit behind the first disc cutter and to shear-off said body of rock material in the direction of the first cut. Each disc cutter includes a set of mutually spaced cutting members arranged to create, during a turn of the drill bit, a corresponding set of cut sections of the cut created by the disc cutter, and wherein the cutting members are arranged so that the sets of cut sections created during subsequent drill bit turns are staggered relative to each other.

Description

drill

The present invention relates to a rotary drill bit for drilling holes in earth formations. There are many types of drills used in the prior art, such as gear drills or jet cutting drills. These drill bits are generally provided with wear-resistant cutting elements made of a material with high wear resistance, such as diamond or tungsten carbide. The cutting action of these cutting elements is mainly produced by the grinding of these elements along the bottom of the borehole. The progress of the drill bit in the borehole depends on many factors, for example, the amount of wear on the cutting parts, the hardness of the rock and the weight of the drill bit. Since the cost of drilling accounts for most of the cost of the entire wellbore, it is necessary to reduce the drilling time, that is, to increase the drilling speed.

WO 99/11900 discloses a rotary drill comprising a plurality of disc cutters mounted on tapered rollers capable of cutting a plurality of substantially circular and radially Slots spaced at a certain distance. The set of cutting elements on each roller moves radially relative to the set of cutting elements on the other roller such that for each radially adjacent pair of cutting elements, the second The cutting elements all cut into the bottom of the borehole at a position behind the first cutting element. A body of rock material is defined between each cutting groove, and the rock material body will be sheared off by the second cutting member along the direction of the cutting groove formed by the first cutting member.

It has been found that the rate of penetration (ROP) of known drill bits into the formation is relatively low in certain rock formations, especially hard rock formations, due to the shearing of the body of rock material along the upper end of the trough formed by the first cutter. more difficult. Therefore, there is a need to provide an improved drill bit capable of increasing the rate of penetration ROP in these types of rocks.

According to the present invention, there is provided a rotary drill bit for drilling a hole in an earth formation, the drill bit comprising: a first disc cutter and a second disc cutter, each disc cutter capable of Rolling along the bottom of the borehole during rotation, thereby cutting substantially circular and radially spaced cut grooves at the bottom of the borehole, so that the body of rock material is confined between the cut grooves, and the second disc shape The cutting member is configured to cut into the bottom of the borehole at a selected bit rotation interval behind the first disc-shaped cutting member and to cut said body of rock material in the direction of the first cutting groove, wherein each disc Shaped cutting parts all comprise a group of cutting parts that are spaced apart from each other, and this group of cutting parts can form a group of cutting groove parts corresponding to the cutting groove that disc cutting part forms in the rotation process of drill bit; And, cutting parts It is arranged in a structural form that can make the group of groove-cutting parts relatively staggered during the continuous rotation of the drill bit.

By the following features: each disc-shaped cutting element is composed of a set of discontinuous cutting elements, which replace the continuous disc-shaped cutting elements of the prior art, thus reducing the number of cutting elements. Instantaneous surface contact with the bottom of the borehole, allowing the bit to penetrate deeper into the rock formation for a given weight. Like this, the cutting groove that is formed by cutting member is also just deeper, therefore, compared with prior art, just make the rock material body that is sheared off on the lower end direction of the first cutting groove be more than the first cutting groove. A body of rock material that has been sheared upward.

Be aware that since the disc-shaped cutout is no longer continuous, a complete circumferential groove must take several revolutions of the drill to form. This can be accomplished by dimensioning the drill bit in such a way that the rock material interposed between the grooving portions formed by the cutting members during the previous revolution of the drill bit can be removed during the latter revolution of the drill bit. The cutting part cuts in.

Below with reference to accompanying drawing, the present invention is described by example, and accompanying drawing wherein:

Figure 1 schematically shows a bottom view of a drill bit according to the invention;

Fig. 2 schematically shows a partial side view of the drill bit shown in Fig. 1;

Fig. 3 schematically shows a bottom view of the tapered roller of the drill bit shown in Fig. 1;

FIG. 4 schematically shows various stages of drilling with the drill bit shown in FIG. 1 , and a transverse cross-sectional view of the bottom of the drilled hole.

In the drawings, the same reference numerals denote the same components.

In FIG. 1 , a bottom view of a drill bit 1 is shown, which is provided with a drill bit body 3 and three tapered rollers 4, 5, 6 arranged at an angle relative to the axis of rotation 7 of the drill bit. Arranged at 120° angle intervals. The tapered roller is rotatably connected with the drill body 3 . Tapered roller 4 is provided with a group of disc-shaped cutting parts 4a, 4b and 4c, tapered roller 5 is provided with a group of disc-shaped cutting parts 5a, 5b and 5c, and tapered roller 6 is provided with a group of disc-shaped cutting parts. Parts 6a, 6b and 6c, each disc cutting part 4a, 4b, 4c, 5a, 5b, 5c, 6a, 6b and 6c are all along the respective tapered rollers in a plane substantially perpendicular to the axis of rotation of the tapered rollers. Circumferential extension of the column. Each of the disc cutting members 4a, 4b, 4c, 5a, 5b, 5c, 6a, 6b and 6c is designed to be able to rotate during the rotation of the drill bit 1 when the respective rollers 4, 5 and 6 roll along the bottom of the borehole. The formation of a substantially circular slot is cut into the bottom of the borehole.

Referring to FIG. 2 , a partial side view of the drill bit 1 and the tapered roller 4 is shown. For the sake of clarity, the tapered rollers 5 and 6 are not shown in the figure, but the parts of the cutting members 5b, 5c, 6b and 6c which are in contact with the bottom of the borehole at various contact points are shown in dotted lines. . The radially outermost cutting elements 4a, 5a and 6a are designed to cut into the bottom of the borehole with equal radii relative to the axis 7, i.e. these cutting elements are arranged on the respective conical rollers at the same axial position. On columns 4, 5 and 6. The inner cutting elements 4b, 4c, 5b, 5c, 6b and 6c are arranged on the tapered rollers 4, 5 and 6 in a mutually offset manner in the axial direction (relative to the rotation axis of the tapered rollers). In other words, cutting member 5b cuts into the bottom of the borehole with a radius that is between the radii at which cutting members 4a and 4b cut into the bottom of the borehole; cutting member 5c cuts into the bottom of the borehole with a radius that is between the radii of the cutting members 4b and 4c cut into the bottom of the borehole at a radius between; cutting member 6b also cuts into the bottom of the borehole at a radius between the radii at which cutting members 4b and 5c cut into the bottom of the borehole.

Each disc cutting member is provided with two side walls 10, 12, only the respective sides 10, 12 of the cutting members 4a, 4b and 4c are shown in Fig. 2 for the sake of clarity. Each pair of sides 10 , 12 defines a wedge-shaped cutting edge 14 . Furthermore, each side 12 extends perpendicularly to the axis of rotation of the respective tapered roller 4, 5 and 6 (indicated by the reference numeral 16 on the tapered roller 4), so that during drilling, the side 12 is aligned along the axis of rotation. The direction of 16 is pressed against the rock. The side surface 20 extends parallel to the axis of rotation 7 of the drill head 1 at a point in contact with the bottom of the borehole.

As shown in Figure 2, each disc cutting member 4a, 4b, 4c, 5a, 5b, 5c, 6a, 6b, 6c is formed by a set of mutually spaced apart grooves 20, such that the rest of the disc cutting member A set of mutually spaced cutting members 22 is accordingly defined. For each tapered roller 4, 5 and 6, groups of cutting elements 22 on adjacent cutting elements are arranged in a staggered manner relative to each other.

The size of each tapered roller 4, 5, 6 is all designed so that the cutting member 22 of each disc cutting member on the tapered roller can be cut at the bottom of the borehole during one revolution of the drill bit 1. A set of grooving portions (not shown) is formed and the formed sets of grooving portions are allowed to rotate relative to each other as the drill bit continues to rotate. In other words, during the next revolution of the drill head 1 , the cutting element 22 of the disc cutting element cuts into the bottom of the borehole at a position not cut by the preceding cutting element 22 . This just shows: the complete circular groove is formed by the disc cutting part after the drill bit 1 rotates multiple turns.

The cutting elements 22 are spaced apart from each other at the same pitch along the circumference of the corresponding disc cutting elements, that is, in the case of the illustrated embodiment, if necessary to prevent the cutting elements 22 from being precisely positioned during the next revolution of the drill bit. Cut into the same groove formed in the previous turn, then you can get the desired size design. One method is achieved by avoiding the occurrence of the following condition: L=i×T, where L=perimeter of the slot, i=integer 1, 2, 3, . . . , etc., T=cutting element the intercept.

Since T=π×d/n, and L=π×D, wherein d is the rolling diameter of the disc cutting member, n is the number of cutting pieces of the disc cutting member, and D is the number of cut grooves formed by the cutting member. Diameter, so that: if D/d=(i+f)/n, then the size can be designed correctly.

Preferably, 0.3 < f < 0.7. For example, f may be about 0.5, which will allow for about two full revolutions of the drill bit to form a full flute.

The values of D and d can be selected in such a way that 1.5<D/d<2.0 can be satisfied.

The bottom view of the tapered roller 4 is shown in Fig. 3, and the numerical values of the angular range of the cutting part and the groove are also shown in the figure (the angular range of the cutting part is 32 °, and the angular range of the groove is 28°). The figure also shows the situation that the cutting parts of the disc cutting part 4a and the disc cutting part 4b overlap each other by 2°. There is also a similar angular overlap of the cutting elements at the respective cutting elements 4b, 4c.

Furthermore, the tapered rollers 4, 5, 6 are also provided with conventional cutting hard inserts 26 on the outermost cutting parts 4a, 4b, 4c and on the inner part of the tapered rollers.

During normal operation, the drill bit 1 is rotated within the borehole, thus causing the tapered rollers 4, 5, 6 to roll and cut along the bottom of the borehole. The cutting operation will be described below only for the cutting members 4b, 5b and 6b, since the other cutting members operate similarly to the cutting members described above.

Referring to FIG. 4, the cutting members 4b, 5b and 5c form slots 32, 34 and 36 adjacent to each other at the bottom of the borehole. These slots are represented by straight lines but, in practice, their shape corresponds to varying degrees to the shape of the portion of the cutting element which penetrates the bottom of the borehole. Lines f, g, h, I, j represent the envelope of the lower end of the disc-shaped cutting elements 4b, 5b and 5c as a function of the angle of rotation of the drill bit. In this way, the drill starts to rotate in the borehole from 0° at the depth f, the straight line g represents the height level of the drill bit when it rotates 120°, the straight line h represents the height level of the drill bit when it rotates 240°, and the straight line I represents the drill bit The height level when turning 360°, the straight line j represents the height level when the drill bit turns 480°.

At a turning angle of 120°, the cutting portion 4b already has the slot 36 at the height g. At a swivel angle of 240°, the cutting element 5b places the slot 34 at a height h. In this way, the rock material body 38a is limited between the cutting groove 36 with a height level of h and the cutting groove 34 with a height level of g, and the rock material body 38a is the side surface 12 of the cut part 5b along a line in the cutting groove 36. The straight line s1 extending between and 34 is cut down.

At a turning angle of 360°, the cutting member 6b has formed a kerf 32 at height i, thereby confining the body of rock material 38b between the kerf 34 of height level g and the kerf of height level i, while the rock material Body 38b is cut from side 12 of cut part 6b along a line s2 extending between slots 34 and 32 .

At a turning angle of 480°, the cutting member 5b has formed a groove 34 at a height j, thereby confining a body of rock material 38c between a groove 36 at a height level i and a groove 34 at a height level j, the rock material The body 38c is cut from the side of the cut part 5b along a straight line s3 extending between the slits 36 and 34 .

Similarly, after continuing to rotate 120°, the rock material body 38d will be limited between the cutting groove 34 whose height level is j and the deeper cutting groove 32, and this rock material body 38d is the part of the cut part 6b. The sides are cut along a line s4 extending between the slots 36 and 34 .

The outer cutting members 4a, 5a and 6a will cut and shear the rock material between the grooves (not shown) formed by the above cutting members and the grooves 32 similarly formed by the cutting portion 5b. . The cutting action of the cutting elements 4c, 5c, 6c is similar to that of the cutting elements 4b, 5b, 6b.

The discontinuous cutting member 32 formed by the cutting member 32 will extend deeper into the bottom of the borehole than a kerf formed by a continuous disc cutting member of the same weight on the drill bit (i.e., a cutting member without grooves). position. Therefore, the size of the body of rock material between adjacent grooves in the drilling direction of the drill bit is larger, so that it is possible to avoid only superficial cutting of the surface layer when performing drilling operations in hard formations, and thus to Improve drilling efficiency.

Claims (11)

1. A rotary drill bit for drilling a hole in an earth formation, the drill bit comprising: a first disc-shaped cutting element and a second disc-shaped cutting element, each disc-shaped cutting element being designed to rotate during the rotation of the drill bit A form of construction capable of rolling along the bottom of a borehole such that first and second generally circular slots are cut in the bottom of the borehole spaced apart such that a body of rock material is confined between said slots the second disc-shaped cutting element is designed to cut into the bottom of the borehole at a selected drill bit rotation distance behind the first disc-shaped cutting element and to cut off the body of rock material in the direction of the first groove The structural form is characterized in that: each disc-shaped cutting part includes a group of cutting parts spaced apart from each other at a certain distance, and the cutting parts are designed so that during the rotation of the drill bit, the disc-shaped cutting part can A group of corresponding notch parts is formed; the cutting part is also designed to make the plurality of groups of notch parts formed during the continuous rotation of the drill bit relatively staggered. 2. The rotary drill bit according to claim 1, characterized in that: the cutting parts are distributed on the cutting parts at substantially the same intervals; the size of the drill bit is designed in such a way as to satisfy the following formula: D/d=(i +f)/n, in, D = diameter of the cut groove formed by the cutting part; n = the number of cut pieces of the cutting part; d = rolling parts of cutting parts; i = integer 1, 2, 3, ... etc.; 0<f<1. 3. A rotary drill bit according to claim 2, characterized in that 0.3<f<0.7. 4. A rotary drill bit according to claim 2 or 3, characterized in that f is about 0.5. 5. Rotary drill bit according to one of claims 2 to 4, characterized in that 1.5<D/d<2. 6. A rotary drill according to any one of claims 1 to 5, characterized in that the drill comprises a drill body and a plurality of tapered rollers, the tapered rollers being interconnected with the drill body so that it can be The drill bit rolls within the borehole substantially along the bottom of the borehole during rotation and can be positioned in different radial orientations, wherein the first tapered roller is provided with a first disc-shaped cutting member and the second tapered roller is provided with a second Two disc-shaped cutting parts. 7. The rotary drill bit according to claim 6, characterized in that: each of said tapered rollers is provided with a plurality of disc-shaped cutting parts positioned at intervals along the axial direction of the tapered roller; Multiple sets of cutting parts of adjacent cutting parts are arranged in a staggered manner. 8. A rotary drill bit according to any one of claims 1 to 7, characterized in that, for each disc-shaped cutting element, each cutting element of the disc-shaped cutting element is along a portion of the disc-shaped cutting element at an angle α Extending, the distance between two adjacent cutting pieces of the disc-shaped cutting member extends along the portion of the disc-shaped cutting member with angle β, and α=β+δ, and 0°<δ<4°. 9. Rotary drill bit according to claim 8, characterized in that 1° < δ < 3°, and δ is preferably about 2°. 10. A rotary drill bit according to any one of claims 1 to 9, characterized in that each set of cutting members is defined by a set of grooves arranged at intervals on the disc-shaped cutting member, and in that the disc-shaped cutting member There are multiple groups of cutting parts installed on it. 11. The rotary drill bit described above with reference to the accompanying drawings.

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