US3027952A

US3027952A - Drill bit

Info

Publication number: US3027952A
Application number: US751936A
Authority: US
Inventors: Warren B Brooks
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1958-07-30
Filing date: 1958-07-30
Publication date: 1962-04-03
Anticipated expiration: 1979-04-03
Also published as: GB897832A

Description

W. B. BROOKS April 3, 1962 3,027,952

DRILL BIT Filed July 30, 1958 4 Sheets-Sheet 1 I Y L. L 4 X FIG. 6

WARREN B. BROOKS INVENTOR.

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ATTORNEY April 3, 1962 w. B. BROOKS DRILL BIT 4 Sheets-Sheet 2 Filed July 30, 1958 Y DIRECTION OF ROTATION MATRIX FIG. 7

WARREN B. BROOKS IN VENTOR. gwmlp ATTORNEY April 3, 1962 w. B. BROOKS 3,027,952

DRILL BIT Filed July 30, 1958 4 Sheets-Sheet 3 Rd W FIG. 9

WARREN B. BROOKS INVENTOR.

A T TORNEY April 1962 w. B. BROOKS 3,027,952

DRILL BIT Filed. July 30, 1958 4 Sheets-Sheet 4 MATRIX Q i I s I FIG. I O

WARREN B. BROOKS INVENTOR.

ATTORNEY 3,027,952 DRILL BIT Warren B. Brooks, Dallas, Tex., assignor, by mesne assignments, to Socony Mobil Oil Company, Inc., New York, N.Y., a corporation of New York Filed July 30, 1958, Ser. No. 751,936 Claims. (Cl. 175329) This invention relates to drill bits and relates more particularly to drill bits adapted to penetrate extremely hard earth formations such as are encountered while drilling boreholes during exploration for petroleum oil, gas, and mineral deposits.

Drill bits adapted to penetrate extremely hard earth formations are well-known. It has been customary to employ hard inserts in drill bits, such 2 inserts formed of hardened metal or diamonds. In those bits where diamonds are used as inserts, the diamonds are embedded in a matrix material which is formed around the sides and lower ends of the bits. The placement of the diamonds in the matrix has followed varying patterns. In some bits the diamonds have been set at random into the surface of the matrix with no consideration being given to special positioning or orientation of the diamonds. In other hits the diamonds have been placed in the matrix in concentric circles which emanate from the center of the bit. Some effort has been made to orient the diamonds in the matrix for the purposes of improving the life of the bit and increasing its cutting efficiency. In the latter case, most of the diamonds have been positioned at a particular angle with respect to the surface of the matrix and sloping in the direction-of rotation of the bit. Bits employing random-set diamonds and bits provided with diamonds oriented by previously known methods leave much to be desired with respect to both the depth of penetration obtainable before replacement is required and the diamond loss incurred per unit of penetration during drilling.

It is an object of this invention to provide a drill bit which employs diamond cutting elements. It is an object of this invention to provide a drill bit which employs diamonds which are oriented at uniform predetermined angles irrespective of the plane of the matrix of the bit. It is another object of this invention to provide a drill bit in which diamonds are oriented in the matrix of the bit with respect to both a direction of maximum hardness within each diamond and the forces exerted upon each diamond by the penetrated formation during drilling. It is another object of this invention to provide a method of orientation of diamonds in the matrix of drill bits. It is another object of this invention to provide a method of orientation of diamonds in drill bits wherein consideration is given to both the direc tions of maxim-um hardness in the diamonds and the forces exerted upon each of the diamonds during drilling.

In accordance with the invention each of the diamonds in a drill bit is set in the matrix of the bit at uniform, predetermined angles and in such a position that one of the directions of maximum hardness in each diamond is positioned so as to oppose the direction of greatest force exerted upon the diamond by the formation being drilled.

Referring to the drawings:

FIG. 1 is a perspective view of a cube form of diamond;

FIG. 2 is a top plan view of the cube form of diamond shown in FIG. 1;

FIG. 3 is a perspective view of an octahedron form of diamond;

FIG. 4 is a top plan view of the octahedron form of diamond shown in FIG. 3;

"nited States P2111611:

' of diamond;

2 FIG. 5 is a perspective view of a dodecahedron form FIG. 6 is a top plan view of the dodecahe'dron form of diamond shown in FIG. 5;

FIG. 7 is an enlarged fragmentary sectional view of a portion of a bit and a formation being drilled, illustrating the positioning of an octahedron form. of diamond in the matrix of a bit in accordance with the invention;

FIG. 8 is a diagrammatic perspective representation of an octahedron diamond set in a drill bit in accordance with the invention, illustrating the position of a single diamond relative to both the longitudinal axis of the bit and a radius line drawn from the longitudinal axis through the diamond;

FIG. 9 is a diagrammatic perspective view of only a cube face of the diamond of FIG. 8, showing its position relative to both the longitudinal axis of a bit and a radius line; and

FIG. 10 is a plan view of the lower portion of a coring-type drill bit, showing a plurality of diamonds set in the matrix of a drill bit in accordance with the invention.

Investigation has shown that among the diamonds most commonly employed in drill bits the internal crystallographic structure of the diamonds is identical even though their external shapes may differ. The term internal crystallographic structure as used herein refers to the arrangement of the atoms in a diamond crystal and the chemical bonds which tie the atoms together. The bonds between all the atoms of a diamond have equal strength; however, they are so distributed that there are more bonds in certain layers Or directions within a crystal than exist in other layers or directions. This unequal distribution of the bonds between the atoms creates planes of unequal strength and resistance to abrasion. With a knowledge of the distribution of the bonds between the atoms within a crystal, it is possible to as certain the directions of maximum hardness, that is, those directions which will be most resistant to abrasion, within the several basic crystal forms used.

Illustrated in FIGS. 1-6 are various single crystal forms of diamonds which are the ones most commonly found and employed as cutting elements in drill bits. These forms are the cube, FIGS. 1 and 2; the octahedron, FIGS. 3 and 4; and the dodecahedron, FIGS. 5 and 6. Though they clearly do not resemble each other in external shape, the internal structure of these three basic forms of diamonds possess extremely similar, if not identical, characteristics of distribution of atoms and chemical bonds between atoms. Each of these forms of diamonds possesses three axes which are perpendicular to each other. a

The cube form ofdiamond, as shown in FIGS. 1 and 2., possesses six square faces, eight corners, and twelve edges. The crystallographic axes of the cube, x, y, and 2, respectively, are found by connecting the center points of opposite faces. For example, the y axis may be located by connecting the center of face 20 with the center of face 21. Each of the faces of the cube is parallel to two axes of the cube. For example, face 20 is parallel to the x and z axes. For purposes of definition, the term cube face as used herein means not only the actual faces on the exterior of the cube but also any plane within the cube which is parallel to any two axes of the cube. It will be recognized that this definition will include any internal or external faces which are parallel to the x and y axes, the x and z axes, and the y and z axes.

One of the directions of maximum hardness in a diamond and, consequently, one most resistant to abrasion is the diagonal across a cube face. This direction is represented in FIGS. 1 and 2 by line 30 which lies in cube face Patented Apr. 3, 1962' 20. Line 30 is perpendicular to the y axis; it lies in a plane, cube face 20, which is parallel to the x and z axes; and it bisects the 90 angle between the x and z axes. It can be seen that any line which is perpendicular to one of the axes of the cube and bisects the angle between the other two axes will be a diagonal in a cube face and, consequently, will fulfill the qualifications of one of the directions of maximum hardness in the diamond, Whether the line be along an exterior surface of the diamond or along a plane within the diamond.

The above discussion of axes, cube faces, and directions of maximum hardness, though given with relation to the cube form, is equally applicable to the forms of diamonds represented in FIGS. 3-6.

FIGS. 3 and 4 show an octahedron form of diamond crystal which has eight equilateral triangular faces, twelve edges, and six rectangular pyramid points. The axes of the octahedron, the same as with the cube, are three lines which lie within the octahedron and are perpendicular to each other. The axes x y and Z1 of the octahedron are located by connecting opposite pyramid points. For example, the y axis lies along a line connecting point 40 with point 41. A cube face in the octahedron is any plane which is parallel to any two of the axes. For example, in FIG. 3, there is shown a cube face 50 which is parallel to the x and Z1 axes. The cube face 50 corresponds to cube face 20 shown in the cube in FIG. 1. If the cube of FIG. 1 and the octahedron of FIG. 3 were oriented such that their respective axes would be parallel, that is, with axis x parallel to axis x axis y parallel to 3 and axis z parallel to axis Z1, any direction in the octahedron would possess the same hardness characteristics as the same direction in the cube. The line 60 shown in FIG. 3 is along a direction in the octahedron which possesses the same hardness characteristics as will be found in the cube along the line 30. Though line 60 does not appear to be a diagonal line in a cube face, it is by definition a diagonal in a cube face inasmuch as it lies perpendicular to the y axis and bisects the angle between the x and Z axes. Any direction in the octahedron, such as that along the line 60, which fulfills the requirements of a diagonal in a cube face, will be one direction along which the diamond will possess maximum resistance to abrasion.

FIGS. 5 and 6 show a dodecahedron which possesses twelve equal rhombic faces, six rectangular pyramid points, eight triangular pyramid points, and twenty-four edges. The dodecahedron, like the cube and octahedron, has three crystallographic axes positioned perpendicular to each other. Those points which are referred to as rectangular pyramid points are points formed by the junction of four rhombic faces. Those points referred to as triangular pyramid points are the points which are formed by the junction of three rhombic faces. The axes of thedodecahedron are along lines drawn between opposite rectangular pyramid points. The axes, as shown in FIG. 5, are x y and Z2. Axis y for example, is located along a line drawn from rectangular pyramid point 70 to rectangular pyramid point 71, which lies opposite point 70. Since the dodecahedron possesses six rectangular pyramid points, connection of each pair of opposite pyramid points will provide the three crystallographic axes. A cube face in the dodecahedron and the diagonal in the cube face are located in the same manner as with the cube and octahedron. If the axes of the dodecahedron are oriented such that they will lie parallel to the axes of the octahedron and the cube, any direction in the dodecahedron will possess the same abrasion re sistance characteristics as the same direction in the octahedron and the cube. An example of one of the directions of maximum hardness in the dodecahedron is illustrated in FIG. 5 by line 8% which is the diagonal in cube face 81 which is parallel to the x and 2 axes. In accordance with the definition of a diagonal in a cube face, line 80 lies perpendicular to axis y in a direction which bisects the angle between axis x and axis Z Any line of direction through the dodecahedron which is perpendicular to one axis and bisects the angle between the other two axes will be one line of direction of maximum hardness and by definition a diagonal in a cube face.

With a knowledge of the relationship, as discussed above, between the cube, the octahedron, and the dodecahedron, these three basic shapes of diamonds may be oriented in the matrix of a drill 'bit such that one of the directions of maximum hardness in each diamond will lie in the desired position in accordance with the inven tion. The basic shapes of diamonds have been discussed in the light of their existing in the ideal, perfect shapes. It will be apparent to those skilled in the art of crystallography that such is not the case. It is probably rare that these ideal basic shapes will be found existing as such in nature. More likely the rule is that the basic shapes will be distorted to some degree or they may exist in combination with each other, such as, two' cubes joined, or a cube and an octahedron joined, so that only a portion of each basic shape Will be visible to the eye. Perhaps, only a face or two or a point of any one basic shape will be recognizable. A skilled diamond setter will not find such irregularities a problem. With the ability to recognize any of the points or faces of the basic shapes of diamonds and a knowledge of the positions of the axes of the basic shapes, the diamonds may be oriented in the desired positions in the matrixof a bit.

FIG. 7 illustrates the position of an octahedron form of diamond crystal 89 oriented in the matrix 90 of a drill bit, in accordance with the invention. Also shown in FIG. 7 is formation rock 91 being cut by the dia mond. Reference numeral 92 designates the rock cut as it builds up in the form of a chip along a face of the diamond; It is believed that the force primarily responsible for the wear of a diamond in a drill-bit is that force which is exerted upon the diamond by the rock in a formation as the diamond cuts through the rock.- Theforce ex' erted by the rock 91 upon the diamond at the time of cutting is equal and opposite to the resultant of both a vertical, downward force resulting from theweight of the bit and drill string upon the diamond and a horizontal force in the direction of cutting resulting from the tofque which must be exerted upon the drill string to efIect cutting. In FIG. 7, W is the force upon the diamond ex-' ert'ed by the weight of the bit and the drill string, and T is the force upon the diamond in the direction of cutting resulting from the torque applied to the drill string. In FIG. 7, reference numeral 93 represents the longi tudinal axis of the bit. W is parallel to axis 93, and T is perpendicular to axis 93 at *a point removed from the axis. R is the resultant of W and T, and R is the reaction force exerted by the rock upon the diamond. At the time cutting takes place, the force R- is equal in magnitude and opposite in direction to R A side view of a cube face 50 is illustrated. The diamond is so positioned that forces R and R lie in the plane of cube face 50. For any given set of conditions, the di-' rection and magnitude of R may be determined by laboratory experiment. For example, a cutting element, such as a diamond, may be positioned in the matrix of a drill bit, a given amount of weight placed on the bit with the bit resting on a sample of rock to be cut, and the bit rotated to effect cutting of the rock. The rotational force required to push the cutting element through the rock to effect cutting may be measured. Thus, knowing the weight W on the cutting element and the force T required for the cutting element to cut the rock, the magnitude and direction of the resultant R of T and W may be determined.

In connection with FIG. 7, it has been stated that force W is exerted in a direction parallel to axis 93 of of the bit and that force T is exerted in a direction perpendicular to axis 93. These relations between axis 93 and forces T and W are also illustrated in FIG. 8 which is a diagrammatic perspective view showing the relationship of the position of an octahedron diamond 89 to the axis 93 when the diamond is set in a bit in accordance with the invention. For purposes of clarity and simplicity, the body and matrix of the bit are not shown in FIG. 8. In FIG. 8, axis 93 is the longitudinal axis of a drill bit; or stated otherwise, it is the axis about which the bit rotates when drilling. Line 94 is a theoretical line which is perpendicular to axis 93 and extends from the axis through the diamond crystal 89. Line 94 will hereinafter be referred to as a radius. Since a large number of diamonds will be set in the matrix of a bit constructed in accordance with the invention, it will be readily understood that each of the diamonds will have its own respective radius extending from the axis to the particular diamond in question. The diamond crystal 89 is positioned such that the portion of radius 94 passing through the diamond crystal lies within cube face 50 as illustrated in FIG. 8. Thus, with the diamond crystal oriented in accordance with the invention, the diamond is so positioned that radius 94 lies within cube face 50 and force R is coincident with the diagonal in cube face. 50'. Stated in other words, each diamond crystal is so positioned that a radius drawn to the crystal from the axis will lie in a cube face of the crystal and the crystal is so tilted that the force R will also lie in the cube face of the crystal along the line which is the diagonal in the cube face.

In FIG. 9 for purposes of simplicity and clarity, only a cube face 50 is shown to further illustrate the geom- .etry of orienting a diamond crystal in accordance with rthe invention. FIG. 9 is similar to FIG. 8 in that the longitudinal axis 93 of a drill bit, radius line 94, and cube face 50 are in the same positions, respectively, as in FIG. 8. Reference numeral 95 refers to a hypothetical right circular cylinder generated about radius line 94 which serves as the axis of the cylinder. Cylinder 95, as shown, is divided in accordance with Well-known geometrical terminology into quadrants I, II, III, and IV. Quadrant I is the upper right quadrant of the cylinder, as shown, with the remaining quadrants being numbered in a counterclockwise direction. As in FIG. 8, FIG. 9 shows the direction of the forces W, T, and R with force R being perpendicular to radius line 94 and cube face 50 being so positioned that R is coincident with the diagonal in the cube face. The plane of cube face 50 lies within quadrants I and III of cylinder 95. It is to be understood that cylinder 95 is purely hypothetical and is shown for the purpose of better illustrating the orientation of a diamond in accordance with the invention and forms no part of the actual physical structure of a drill bit. Considering the orientation illustrated in the light of an actual bit containing diamonds set in accordance with the invention and assuming the end of the bit in which the diamonds are set as the downward end of the bit and that rotation while drilling is in a clockwise direction, it will be recognized that cube face 50 slopes downward and in the direction of rotation of the bit. This may also be observed by reference back to FIG. 7.

FIG. 10 illustrates the general arrangement of one row of diamond crystals embedded in the matrix of a drill bit which is employed in coring a well. Through for purposes of clarity only one row of diamonds is shown in FIG. 10, it will be readily apparent that a bit will employ a plurality of rows of diamonds distributed over the entire matrix of the bit. As previously stated, it will be recognized that though the bit possesses only one longitudinal axis 93, each of the diamonds 100 set in the matrix 90 will have its own radius line extending from the axis to the diamond as shown in FIGS. 8 and 9. Each diamond is set in the matrix of the bit relative to its own radius line and the longitudinal axis of the bit. The necessary weight W and the torque force T are determined experimentally for the particular rock formarlllOIl for which the bit is designed, and the direction of each diamond crystal will be cutting the same type of rock in the formation for which the bit is designed, the

necessary forces W and T required to effect cutting of the rock will be the same for all of the diamonds in the bit; and, consequently, all diamonds will be oriented in the same respective positions relative to longitudinal axis of the bit and the radius line for each of the diamonds. Thus, each diamond is oriented relative to both its own particular radius line, the longitudinal axis of the bit, and the direction of the force R as determined experimentally. This form of orientation, therefore, provides for diamond orientation which is based upon the hardness characteristics of the diamonds employed and the forces encountered While the bit is drilling. This form of orientation is consequently entirely independent of the plane of the surface of the matrix of the bit.

Though the physical structure of diamonds and their orientation in accordance with the invention have been discussed in terms of the preferred line of direction of maximum hardness being the diagonal in a cube face, it will be recognized by those skilled in the art that there are other directions within diamonds which possess a high degree of-hardness. These other directions may be oriented in a drilling bit in accordance with the invention. For example, in a dodecahedron of diamond, a direction which is considered to possess a high degree of hardness is along the long diagonal in a rhombic face or, stated in other words, along a line in a rhombic face between two rectangular pyramid points. In orienting the diagonal in a rhombic face of a dodecahedron, the diamond is placed ina matrix of a. bit such that the rhombic face will be in the position of a cube face as previously described and the diagonal in the rhombic face will be in the position of a diagonal in a cube face. The diagonal in the rhombic face lies perpendicular to a radius drawn to the diamond from the longitudinal axis and the rhombic face itself will be so positioned that the face will be coincident with a plane containing the radius. Considering FIGS. 7 and 9 in the orientation of the diagonal in the rhombic face of a dodecahedron, the rhombic face may be substituted for cube face 50. Thus, the rhombic face will lie in quadrants I and III of a hypothetical cylinder generated about radius line 94. Considering forces T and W, the diagonal in the rhombic face will be positioned coincident with the resultant force R While the invention has been described in connection with certain specific embodiments thereof, it will be understood that further modifications will suggest themselves to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

What is claimed is:

1. In a drill bit having a body portion provided with a matrix portion formed thereon, a plurality of diamond cutting elements embedded in said matrix portion and so oriented that a line of direct-ion of maximum hardness in each of said cutting elements is coincident with the resultant of the torque and weight forces on each of said cutting elements necessary to effect cutting of rock of predetermined hardness and the face of said cutting element containing said line of direction of maximum hardness is coincident with a plane containing a radius line from and perpendicular to the longitudinal axis of said bit to said ace.

2. In a drill bit having a body portion provided with a matrix portion formed thereon, a plurality of diamond cutting elements embedded in said matrix portion, each of said diamond cutting elements being oriented as follows: (a) a line of direction of maximum hardness in a face of said cutting element being perpendicular to and intersecting a radius line extending from and perpendicular to the longitudinal axis of said bit; (b) the face of said cutting element containing said line of direction of maximum hardness being coincident with a plane containing said radius line; and (c) said line of direction of maximum hardness being Coincident with the resultant of forces T and W, where W is a force on said cutting element parallel to the longitudinal axis of said bit due to the Weight impressed on said bit, and T is a force on said cutting element perpendicular to both said radius line andsaid longitudinal axis due to the torque impressed on said bit, and the magnitude of said forces W and T is suflicient to etfect cutting of rock of predetermined hardness by said cutting element.

3. In a drill bit having a body portion provided with a matrix portion formed thereon, a plurality of diamond cutting elements embedded in sm'd matrix portion and soriented that the diagonal in a cube face in each of said cutting elements is coincident with the resultant of the torque and weight forces on each of said cutting elements necessary to effect cutting of rock of predetermined hardness and said cube face is in alignment with a projection of a radius line from and perpendicular to the longitudinal axis of said bit to said cube face.

4. In a drill bit having a body portion provided with a matrix portion formed thereon, a plurality of diamond cutting elements embedded in said matrix portion, each of said diamond cutting elements being oriented as follows: (a) the diagonal in a cube face of said cutting element being perpendicular to and intersecting a radius line extending from and perpendicular to the longitudinal axis of said bit; (b) the plane of said cube face including said radius line; and (c) said diagonal being coincident with the resultant of forces T and W, where W is a force on said cutting element parallel to the longitudinal axis of said bit due to the weight on said bit and T is a force on said cutting element perpendicular to both said radius line and said longitudinal axis due to the torque impressed on said bit, and the magnitude of said forces W and T is sufiicient to effect cutting of rock of predetermined hardness by said cutting element.

5. In a drill bit having a body portion provided with a matrix portion formed thereon, a plurality of diamond cutting elements embedded in said matrix portion, each of said diamond cutting elements being so oriented that a line of direction of maximum hardness in each of said cutting elements is coincident with the resultant of forces T and W, where T is a force on said cutting element perpendicular to the longitudinal axis of said bit due to the torque impressed on said bit and W is a force on said cutting element parallel to said longitudinal axis due to the weight impressed-on said bit, and the magnitude of said resultant of said forces T and W is sufiicient to effect cutting of rock of predetermined hardness by said cutting element.

References Qited in the file of this patent 1. Diamond Orientation in Diamond Bits by A. E. Long and C. B. Slawson, Feb. 1952. Publication of US. Dept. of Interior, Bureau of Mines, Report of Investigations 4853.

ll. Maximum Hardness Vectors in the Diamond, by C. B. Slawson and J. A. Cohn. Industrial Diamond Review, vol. 10, June 1950, pps. 168-l72.

III. Orientation of Diamonds in Diamond Drill Bits, by A. E. Long. Industrial Diamond Review, vol. 12, Jan. 1952, pps. 1014.

IV. Diamond Orientation in Drill Bits, by E. P. Pfleider. Mining Engineering, vol. 4, Feb., 1952, pps. 177-186 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,027,952 April B 1962 Warren B. Brooks It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 62, for "Through" read Though -5 column 6, line 26, after "dodecahedron" insert form Signed and sealed this 21st. day of August 1962.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L LADD Attesting Officer Commissioner of Patents