Drill bit having improved hydraulic action for directing drilling fluid

~ 2017~33 ~ROSS-REFEREN~E TO OTHER PATENTS The sub~ect matter of this appllcatlon ls related to the sub~ect matter of U.S.

Patent No. 4,848,476 lssued July 18, 198g, and U.S.

Patent No. 4,741,406 lssued May 3, 1988.

Backqround of the Inventlon Thls lnventlon relates to rotary drlll blts for drllllng oll wells and the like, and more partlcularly to an improved hydraulic action of drilling fluid against the roller cutters of the drlll bit and the formation being drilled.

While conventional drill bits have been satisfactory for drilling relatively brittle formations, they do not provide satisfactory rates of penetration when drllllng relatlvely plastlcally deformable formations.

Many commonly encountered formations such as salts, shales, limestones, sandstones and chalks, become plastically deformable under socalled differential pressure conditions, when the 76152-1 , ~ 2017533 .

hydrostatic pressure of the column of drilling fluid bearing on the bottom of the well bore exceeds the pressure of the formation surrounding the bore, as often occurs in deep hole drilling. Whereas, brittle formations tent to crack or fracture when engaged by the cutting elements of a drill bit, these plastic formations tend to deform and thus remain intact under such loads. In addition, certain of these plastic formations tend to form a relatively thick coating of drilling debris on the roller cutter which can result in so-called "bit-balling" and limited penetration of the formation by the cutting elements.

Attempts have been made to increase the rate of penetration in plastic formations by using extended nozzles for improving the cleaning action of the hydraulic system. While this nozzle arrangement may offer some measure of improved cleaning action, this action is still not satisfactory for many types of plastic formations. Moreover, in this arrangement, the nozzles extend down to points closely adjacent to the bottom of the well bore, and thus are subject to damage by irregularities, such as projections or ridges, on the bottom of the well bore, which may form from time to time during drilling operations.

One area of the formation, particularly in so-called "sticky" formations, tends to adhere abnormally to the gage row of cutting elements on the roller cutter which is the outermost row that determines the diameter or gage of the bore hole. The cutting elements of the gage row normally engages the bore hole bottom at the juncture of the horizontal bottom 76152-1 2017533 portion and the cylindrical side portion. Thus, the cutting elements of the gage row are normally engaging the portion of the formation defined by two separate formation surfaces generally at right angles to each other. As a result it has been found that oftentimes an increased amount of so-called sticky formations tends to adhere to the gage row of cutting elements.

S~J~qM~Y OF THE INVENTION The present invention is particularly directed to a rotary drill bit having three roller cutters with a plurality of concentric rows of cutting elements on each cutter, and an improved cleaning action for the gage row of cutting elements and the adjacent bore hole formation generally at the juncture of the horizontal bottom portion and cylindrical side portion of the bore hole.

It is noted that the gage row of each roller cutter is the row that most affects the rate of penetration of the rotary drill bit. The gage row normally has more cutting elements therein than the remaining rows. Also, the formation is stronger at the annular corner of the bore hole formed at the juncture of the horizontal bottom surface and the vertically extending cylindrical side surface of the bore hole formation.

Thus, the gage row of cutting elements is the critical row in determining the rate of penetration.

Additionally, in a rotary drill bit having three roller cutters, a so-called "interlocking" row of cutting elements is provided immediately adjacent the gage row normally on two of the three roller cutters.

The interlocking row ~r~ 76152-1 ' ~S, 2017533 includes cutting elements which are staggered and fit between the cutting elements of the gage row in radially offset relation. The interlocking row of cutting elements along with the gage row are thus provided for cutting the formation at its strongest area. It is desirable that maximum cleaning action by the pressurized drilling fluid be provided particularly for the cutting elements in such gage and interlocking rows, and the present invention is directed to such a cleaning action in combination with a subsequent scouring action of the drilling fluid against the adjacent formation in the area of the corner of the bore hole.

A high velocity liquid stream of drilling fluid is provided for each of the roller cutters and the liquid stream for each roller cutter is directed against at least the cutting elements in the gage row on the leading side of the cutter with the cutting elements entering the stream for being cleaned thereby and then exiting the stream prior to engaging the formation at the bottom of the bore hole so that the cutting elements and formation impinged by the stream are subjec ted to separate and sequential cleaning actions by the streamof drilling fluid immediately prior to their engagement.

As indicated, the cutting elements in the gage row engage the bore hole bottom at or closely adjacent the juncture of the horizontal bottom portion and cylindrical side portion of the bore hole bottom. Thus, two separate bore hole surfaces generally at right angles to each other are engaged by the cutting elements in the gage row and oftentimes, particularly for soft sticky formations, more of such 76152-1 2017533 formation materials tends to stick or collect between the cutting elements on the gage row than between the cutting elements on the other rows. It is desirable, therefore, in order to have a balanced washing action by the drilling fluid, that more hydraulic energy be directed against the cutting elements in the gage row than the cutting elements in the rem~; n;ng rows. For that purpose, the nozzle orifice for the high velocity drilling fluid directed against the cutting elements of the gage row is constructed and arranged to provide increased hydraulic energy first against the cutting elements in the gage row and then sequentially against the bore hole bottom formation at or closely adjacent the juncture of the horizontal bottom portion with the vertical side portion.

It is an object of the present invention to provide a rotary drill bit having conically shaped roller cutters thereon with an improved hydraulic action of drilling fluid against the cutting elements on the roller cutter and sequentially against the formation being drilled immediately prior to the engagement of the cutting elements with the bore hole bottom.

A further object of the present invention is to provide such a rotary drill bit in which an improved hydraulic action of the drilling fluid is directed against the cutting elements in the gage row to provide more hydraulic energy against the cutting elements in the gage row than the cutting elements in the remaining rows.

An additional object of the present invention is to provide such a rotary drill bit in which the orifice for 76152-1 X~ 2017533 directing drilling fluid against the cutting elements of each roller cutter is constructed and arranged to provide more hydraulic energy against the cutting elements of the gage row than the remaining cutting elements.

Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective of one embodiment of the rotary drill bit of this invention including three cones or roller cutters of a generally conical shape thereon and discharge nozzles along the outer periphery of the bit body;

Figure 2 is an axial plan view of the rotary drill bit of Figure 1 showing the three roller cutters with annular rows of cutting elements thereon;

Figure 3 is an elevation of a portion of the rotary drill bit of Figures 1 and 2 taken generally along line 3-3 of Figure 2 and showing a stream of drilling fluid directed against the gage row of cutting elements of a roller cutter and the adjacent formation at the bottom of the bore hole;

Figure 4 is a schematic view of a portion of the rotary drill bit shown in Figure 3 taken generally along line 4-4 of Figure 3 and illustrating the stream of drilling fluid directed against the gage row and interlocking row at the juncture of the horizontal bottom portion and vertical side portion of the bore hole;

Figure 5 is a perspective of a modified rotary drill bit having a more central discharge nozzle for each roller 76152-1 ~ q~ 2017533 cutter and arranged to provide increased hydraulic energy against the cutting elements of the gage row of the roller cutters and the adjacent bore hole formation;

Figure 6 is a bottom plan of the modified rotary drill bit shown in Figure 5;

Figure 7 is a generally schematic view of the stream of drilling fluid taken generally along line 7-7 of Figure 6 and showing the drilling fluid directed against the gage row of cutting elements and the adjacent formation; and Figure 8 is a generally schematic view taken generally along the line 8-8 of Figure 7 and showing the stream of drilling fluid against the gage and adjacent row of cutting elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings for a better understanding of this invention, and more particularly to the embodiment shown in Figures 1-4, a rotary drill bit 10 is shown in Figure 1 comprising a central main body or shank 12 with an upwardly extended threaded pin 14. Threaded pin 14 comprises a tapered pin connection adapted for threadedly engaging the female end of a drill string (not shown) and to receive drilling fluid which is connected to a source of drilling fluid at a surface location.

Main body or shank 12 is formed from three integral connected lugs to define upper body portion below pin 14 and three downwardly extending legs 16. Each leg 16 has an inwardly and downwardly extending, generally cylindrical bearing journal 18 at its lower end. Roller cutters 20A, 20B, and 20C 6a 76152-1 X 2017533 are mounted on journal 18 for rotation and each roller cutter is formed of a generally conical shape. Each roller cutter 20A, 20B and 20C comprises a generally conical body 22 having a recess therein receiving an associated bearing journal 18.

A plurality of generally elongate cutting elements 26 have cylindrical bodies mounted in sockets within body 22 and outer tips extending from the outer surface of body 22.

Cutting elements or inserts 26 may be made of a suitable powder metallurgy composite material having good abrasion and erosion re sistant properties, such as sintered tungsten carbide in asuitable matrix. A hardness from about 85 Rockwell A to about 90 Rockwell A has been found to be satisfactory.

The cutting elements 26 are arranged on body 22 in concentric annular rows 28A, 28B, 28C and 28D.

Row 28D is the outermost row and comprises the gage row of cutting elements 26 that determines the final diameter or gage of the formation bore hole which is generally indicated at 30.

Row 28C is adjacent to row 28D and comprises an interlocking row on cutter 20A.

Cutting elements 26 on row 28C are staggered circum 20 ferentially with respect to cutting elements 6`b .

X 76152-1 2017533 26 on row 28D and a Portlon of cuttlng elements 26 on row 28C pro~ects wlthln the clrcular cuttlng path of row 28D.

Thus, the cuttlng paths of the cuttlng elements 26 on rows 28C and 28D of roller cutter 20A overlap.

It ls noted that row 28C for cutters 20B and 20C ls not an lnterlocklng row as spaced substantlally lnward of row 28D and cuttlng elements 26 on row 28C do not pro~ect wlthln the cuttlng path of row 28D.

In some lnstances, lt may be deslrable to provlde two cutters or poRslbly all of the cutters wlth lnterlocklng rows of cuttlng elements.

The bottom of bore hole 30 lncludes a horlzontal bottom portlon 32 and an ad~acent cyllndrlcal slde wall portlon 34 extendlng vertically generally at rlght angles to horlzontal bottom portlon 32.

The ~uncture of horlzontal bottom portlon 32 and cyllndrlcal slde wall portlon 34 ls shown at 35.

The cuttlng elements 26 on gage row 28D engage the formatlon ln cuttlng relatlon generally at the ~uncture 35 formed by horlzontal bottom portlon 32 and the vertlcal slde wall portlon 34.

To provlde hlgh veloclty drllllng fluld for the lmproved cleanlng actlon, partlcularly for the gage row 28D and ad~acent row 28C of cuttlng elements 26, a dlrected nozzle fluld system ls provlded.

The fluld system lncludes a nozzle generally lndlcated at 36 posltloned between each ad~acent palr of legs 16 on the outer clrcumference of blt body 12 at a locatlon above the rotatlonal axls of roller cutter 20A at the ~uncture or connectlon of assoclated ~ournal 18 and leg 16 as shown ln flgure 3.

Each nozzle 36 has a drllllng fluld 76152-1 ~ ~ 2017533 ~assage 38 thereto from the drlll strlng whlch provides hlgh velocity drllllng fluld for dlscharge. Nozzles 36B and 36C for respectlve roller cutters 20B and 20C each have a large dlameter orlflce 40 and a small dlameter orlflce 42 provlded thereln for the dlscharge of hlgh veloclty drllllng fluld.

Large dlameter orlflce 40 has a stream 44 dlrected therefrom prlrnarlly agalnst the gage row 28D and the ad~acent row 28C.

Small dlameter orlflce 42 has a stream 45 dlrected therefrom primarlly agalnst the cuttlng elements 26 ln the remalnlng rows lncludlng row 28B. Thus, as a result of the large dlameter orlflces 40 dlrectlng a stream of drllllng fluld radlally outwardly of the stream of drllllng fluld dlscharged from small dlameter orlflces 42, an lncreased - 7a 76152-1 2017533 flow of drilling fluid therefrom provides increased hydraulic action for the gage row of cutting elements.

Referring to nozzle 36A and particularly Figure 4 thereof, which relates particularly to roller cutter 20A including the interlocking row 28C of cutting elements 36, a nozzle body is shown at 48 having a split ring 50 for mounting body 48. An orifice 52 in nozzle body 48 is elongated in a radial direction and increased progressively in crosssectional area in a radially outwardly direction thereby to direct a stream of drilling fluid having increased energy at the radially outermost area of bit 10 at gage row 28D. In this manner, an increased amount of drilling fluid and increased hydraulic energy is provided progressively in a radial direction thereby to provide the gage row 28D of cutting elements 26 with increased hydraulic action.

As shown particularly in Figures 3 and 4, drilling fluid stream 54 from orifice 52 is shown striking bore hole bottom 30 on the leading side of the ahead of roller cutter 20A. A direction arrow 56 indicates the direction of movement of leg 16 in the bore hole as bit 10 is rotated. A rotation arrow 58 indicates the simultaneous rotation of cutter 20A with the movement of drill bit 10 in the bore hole. Thus, the high pressure drilling fluid stream 54 is directed toward the leading surface of the roller cutter body. Such a placement of stream 54 allows effective cleaning of inserts 26 as the inserts move through stream 54. After fluid stream 54 passes inserts 26, it strikes the bore hole bottom 30 generally at the juncture 35 of horizontal portion 32 and vertical side 76152-1 X., 2017533 portion 34 as shown particularly in Figure 4. Then, the drilling fluid along with cuttings that are chipped or gouged from the formation by inserts 26 move in an upward direction outside drill bit 10 through the bore hole in a conventional manner for return to the surface. Streams 44 and 45 of drilling fluid for roller cutters 20B and 20C are directed against the leading sides of roller cutters 20B and 20C in a manner similar to that of stream 54 against roller cutter 20A.

Thus, the formation and the cutting elements 26 impinged by stream 54 are subjected to separate or sequential cleaning actions immediately prior to their engagement thereby to provide relatively clean engagement surfaces. Such a separate or sequential cleaning action has been found to result in improved drill bit cutting action and increased rates of drilling penetration, particularly in drilling sticky formations.

It is to be understood that various sizes, shapes, and types of nozzles and orifices may be provided and located in various positions on the bit body to provide more hydraulic energy against the cutting elements in the gage row than the cutting elements in the remaining rows thereby to provide a more efficient use of hydraulic energy from the drilling fluid. For example, separate nozzles could be provided for orifices 40 and 42 if desired. As pointed out previously, the gage row and interlocking row of cutting elements are provided for cutting the bore hole formation at its strongest area generally at the juncture of the horizontal bottom portion with the vertical side portion.

It is desirable that maximum cleaning action by the pressurized drilling fluid be provided y l 76152-1 2017533 particularly for the drilling elements in such gage and adjacent interlocking rows and the present invention is directed to a nozzle fluid system in which more hydraulic energy is directed against the cutting elements in the gage row and the adjacent row than in the remaining rows.

As an example of such orifices for directing fluid streams in such manner, elongated orifices may be provided as illustrated by orifice 52 with the orifice being elongated in a radial direction and increasing in area in a radially outward direction.

Therefore, a more efficient utilization of hydraulic energy is provided by the present invention as an increased amount of hydraulic energy is provided at the area of maximum need, i.e., in the area at or closely adjacent the juncture of the horizontal bottom portion with the vertical side wall portion of the bore hole where the formation is the strongest.

Referring now to Figures 5-8, a modified drill bit 110 is shown having a bit body 112 with legs 116 extending therefrom.

Roller cutters 120A, 120B and 120C are mounted on legs 116 thereon for rotation.

Cutting elements 126 are arranged in concentric annular rows on roller cutters 120A, 120B, and 120C with each cutter having a gage row 128D of cutting element 126 and an adjacent row 128C.

Row 128C of roller cutter 120A provides an interlocking row of cutting elements.

Formed at the juncture of each pair of legs 116 iS a recessed portion indicated generally at 127 which interrupts the generally smooth outer circumference of bit body 112.

~ 76152-1 X ;

201753~ Each recessed portion 127 extends in a generally vertical direction along the juncture of each pair of adjacent legs 116 and provides an upward flow passage way for drilling fluid and entrained cuttings from bore hole bottom 130.

Since the main upward flow stream of drilling fluid and cuttings will be directed through the generally vertical flow passages formed by recessed portions 127 of bit body 112, it is desirable that the discharge nozzles be positioned so that minimal overlapping interference occurs between the main downward and upward flow streams.

A high velocity drilling flow chamber is shown at 129 receiving pressurized drilling fluid from a connected drill string. A nozzle 136 positioned inwardly of the outer circumference of bit body 112 is provided for each roller cutter 120A, 120B and 120C and has a flow passage 135 in fluid communication with chamber 129.

Nozzle 136 has a single circular orifice 137 for directing a high velocity stream 154 of drilling fluid against the outer gage row 128D in a manner similar to the embodiment of Figures 1-4.

Stream 154 engages the bore hole bottom 130 at the juncture 135 of horizontal bore hole portion 132 and vertical bore hole portion 134 as shown in Figure 7.

Thus, the location of nozzle 136 and orifice 137 is such that high velocity drilling fluid is directed against the cutting elements of the gage row to provide more hydraulic energy against the cutting elements in the gage row than against the cutting elements in the remaining rows.

The high velocity drilling fluid after cleaning the cutting elements of 11 . _ X 76152-1 2017533 the gage row 128D then engages the bore hole bottom formation at or closely adjacent the juncture 135 of the horizontal portion 132 with the vertical side portion 134 where the formation is normally the strongest thereby to provide an efficient and economical utilization of drilling fluid. While only a single nozzle is shown for each roller cutter in the embodiment of Figures 5-8, it is to be understood that large diameter bits, such as, for example, bits around 18-24 inches in diameter, may have additional nozzles or orifices for each roller cutter. However, in this event, the nozzles and orifices would be positioned and sized so that more hydraulic energy would be applied against the gage row of cutting elements than against the remaining rows of cutting elements.

While preferred embodiments of the present invention have been illustrated in detail, it is apparent that modification and adaptations of the preferred embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention as set forth in the following claims.

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