HYBRID DRILL BIT
A drill bit includes a bit body having a longitudinal bit axis extending there through, a plurality of journals extending from the bit body, each journal having a journal axis extending from a base of the journal through the length of the journal, a roller cone rotatably mounted to each of the journals, and at least one blade protruding from the bit body center and extending radially outward to less than an outer diameter of the drill bit.
Historically, there have been two main types of drill bits used for drilling earth formations, drag bits and roller cone bits. The term “drag bits” refers to those rotary drill bits with no moving elements. Drag bits include those having cutting elements attached to the bit body, which predominantly cut the formation by a shearing action. Roller cone bits include one or more roller cones rotatably mounted to the bit body. These roller cones have a plurality of cutting elements attached thereto that crush, gouge, and scrape rock at the bottom of a hole being drilled.
Bit type may be selected based on the primary nature of the formation to be drilled. However, many formations have mixed characteristics (i.e., the formation may include both hard and soft zones), which may reduce the rate of penetration of a bit (or, reduce the life of a selected bit) because the selected bit is not as desirable for certain zones. For example, both milled tooth roller cone bits and PDC bits can efficiently drill soft formations, but PDC bits will often have a rate of penetration several times higher than roller cone bits.
PDC Drill Bits
Drag bits, often referred to as “fixed cutter drill bits,” include bits that have cutting elements attached to the bit body, which may be a steel bit body or a matrix bit body formed from a matrix material such as tungsten carbide surrounded by a binder material. Drag bits may generally be defined as bits that have no moving parts. However, there are different types and methods of forming drag bits that are known in the art. For example, drag bits having abrasive material, such as diamond, impregnated into the surface of the material which forms the bit body are commonly referred to as “impreg” bits. Drag bits having cutting elements made of an ultra hard cutting surface layer or “table” (often made of polycrystalline diamond material or polycrystalline boron nitride material) deposited onto or otherwise bonded to a substrate are known in the art as polycrystalline diamond compact (“PDC”) bits.
PDC bits drill soft formations easily, but they may frequently be used to drill moderately hard or abrasive formations. They cut rock formations with a shearing action using small cutters that do not penetrate deeply into the formation. Because the penetration depth is shallow, high rates of penetration are achieved through relatively high bit rotational velocities.
Roller Cone Drill Bits
Roller cone drill bits may be used to drill formations that fail more efficiently by crushing and gouging as opposed to shearing. Roller cone drill bits are also used for heterogeneous formations that initiate vibration in drag bits. Roller cone drill bits include milled tooth bits and insert bits. Milled tooth roller cone bits may be used to dill relatively soft formations, while insert roller cone bits are suitable for medium or hard formations. Roller cone drill bits include a bit body with a threaded pin formed on the upper end of the bit body for connecting to a drill string, and one or more legs extending from the lower end of the bit body. The threaded pin end is adapted for assembly onto a drill string for drilling oil wells or the like. Roller cone bits, on the other hand, may have better steerability when building curve section of a wellbore.
Hybrid Drill Bits
Both roller cone and PDC bits have their own advantages. Due to the difference in cutting mechanisms and cutting element materials, they are best suited for different drilling conditions. Roller cone bits predominantly use a crushing mechanism in drilling, which gives roller cone bits overall durability and strong cutting ability (particularly when compared to previous bit designs, including disc bits). PDC bits use a shearing mechanism for cutting, which allows higher performance in soft formation drilling than roller cone bits are able to achieve.
Thus, in drilling operations facing mixed formations, using one type of drill bit over the other may not be adequate for the entire operation. Hybrid drill bits that use a combination of one or more crushing mechanisms and one or more shearing mechanisms have been proposed previously. However, problems arise during the design of these hybrid bits in trying to combine rolling cutters and fixed blades within a limited amount of space.
SUMMARY OF DISCLOSUREThis summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to a drill bit including a bit body having a longitudinal bit axis extending there through, a plurality of journals extending from the bit body, each journal having a journal axis extending from a base of the journal through the length of the journal, a roller cone rotatably mounted to each of the journals, and at least one blade protruding from the bit body center and extending radially outward to less than an outer diameter of the drill bit.
In another aspect, embodiments disclosed herein relate to a drill bit including a bit body having a longitudinal bit axis extending there through, a plurality of journals, extending from the bit body, and a roller cone rotatably mounted to each of the journals, wherein at least one roller cone having a different outer diameter than the others, wherein an offset angle ranging from about 0 degrees to about 90 degrees is formed between a line perpendicular to the bit axis and extending through the bit axis and a center of a backface of the roller cone.
In yet another aspect, embodiments disclosed herein relate to a drill bit including a bit body having a longitudinal bit axis extending there through, a plurality of journals, extending from the bit body, each journal having a journal axis extending from a base of the journal through the length of the journal, wherein the plurality of journals extend from the bit body such that an acute angle ranging from about 15 degrees to about 25 degrees is formed between the journal axis and the bit axis. The drill bit further includes a roller cone rotatably mounted to each of the journals, wherein at least one roller cone comprises a plurality of roller cone cutting elements having planar cutting faces and at least one roller cone comprises a plurality of roller cone cutting elements having non-planar cutting faces, wherein the roller cone cutting elements comprise a roller cone cutting profile.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
Embodiments disclosed herein relate generally to drill bits. In particular, embodiments disclosed herein relate to roller cone drill bits having radially offset journals such that the roller cones engage and cut different regions of a borehole.
Referring to
In this embodiment, the rolling cone cutting elements 137 and the blade cutting elements 127 have planar cutting faces. However, different types of cutting elements may be used on the blades 126 and roller cones 136. For example, as shown in
As discussed above, a roller cone may be rotatably mounted to journals extending from a bit body. Roller cones may include bodies having rounded, conical, or disc shape and a plurality of cutting elements disposed thereon. For example, referring again to
Further, according to some embodiments, the plurality of roller cones 136 may be arranged in such a manner that they engage with and cut the nose and shoulder regions of a bottom hole, but do not engage with the center of a bottom hole whereas the at least one blade 126 may engage and cut the center of a bottom hole. The blade cutting elements 127 form a blade cutting profile, and the roller cone cutting elements 137 form a roller cone cutting profile. As used herein, a cutting profile (e.g., a blade cutting profile and a roller cone cutting profile) refers to the profile or outline of cutting elements as they would appear in rotated view, i.e., when the bit rotated about its longitudinal axis and the roller cones are rotated about their rotational axes. The extent of overlap between roller cone 136 cutting profile and blade 126 cutting profile depends on the radial extension of the at least one blade 126, each blade 126 extending to less than an outer diameter of the drill bit 130.
Further, journals may extend from the bit body at different angles with respect to the longitudinal axis of the bit, as compared to a conventional roller cone bit. Specifically, as shown in
Additionally in accordance with various embodiments of the present disclosure, as shown in
Due to the orientation of the cone 136, disclosed above, the cutting elements used on roller cones may have a unique orientation for roller cone cutting elements so as to enable the cutting elements to shear the formation. Specifically, cutting elements may be oriented or installed on the cones with a particular back rake and/or side rake. For example, referring now to
Equivalent back rake 520 is defined as the resultant of installation back rake angle with the combination of journal angle, and measured by the journal angle β less the installation back rake 511 angle. As previously discussed, the journal angle forms an angle β, between a longitudinal axis 510 of the bit and the center of roller cone back surface 509. According to some embodiments, the equivalent back rake angle, as defined herein, may range from about 10 degrees to about 30 degrees. In more specific embodiments, the equivalent back rake angle may range from about 15 to about 25 degrees.
Referring now to
Equivalent side rake 609 is defined as the resultant of installation side rake angle with the combination of journal offset, and measured by the angle formed between the engage point velocity 607 and the roller cone axis 603 less the installation side rake 605 angle. As previously discussed and shown in
Referring to
In such embodiments, the rolling cone cutting elements 737 have planar cutting faces, such as those conventionally referred to as polycrystalline diamond compact (PDC) cutters. As discussed above, rolling cones having cutting elements with planar cutting faces are also known as shearing rolling cones since the cutting elements shear the formation. Alternatively, rolling cones having cutting elements with non-planar cutting faces are also known as crushing rolling cones since the cutting elements crush/fracture the formation. For example, in some embodiments, rolling cones having cutting elements with non-planar cutting faces may have a pointed, or conical shaped, dome shaped, chisel shaped, and/or saddle shaped cutting face geometry. In some embodiments, rolling cones may have a combination of cutting elements with planar and non-planar cutting faces. Cutting elements used with hybrid drill bits of the present disclosure may include polycrystalline diamond compacts (PDCs), diamond grit impregnated inserts (“grit hot-pressed inserts” (GHIs), natural diamond, milled steel teeth, tungsten carbide inserts (TCIs), diamond enhanced inserts (DEIs), or conical shaped (or other substantially pointed) cutting elements.
According to various embodiments of the present disclosure, roller cone drill bit 730 may include a plurality of gauge cutters 740 disposed on the bit body 732 and along a gauge region of the bit which extends parallel to bit axis 710 at the outer radial periphery of the overall bit cutting profile. In such embodiments, gauge cutters 740 are arranged to engage a side wall of the formation. The plurality of gauge cutters 740 may include rotatable and non-rotatable cutting elements having planar and non-planar cutting faces. In some embodiments, gauge cutters 740 may be substantially similar in material, shape, and size as roller cone cutting elements 737. Further, gauge cutters may be oriented or installed on the bit body 732 with a particular back rake and/or side rake angle.
Additionally in accordance with various embodiments of the present disclosure, at least one roller cone has a different outer diameter than the others. As shown in
One of ordinary skill in the art will appreciate that a roller cone may be characterized by its diameter to height ratio. Referring to
Referring to
Referring to
As shown in
Though two sizes of roller cone are illustrated in each of
While
Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.
Claims
1. A drill bit, comprising:
- a bit body having a longitudinal bit axis extending there through;
- a plurality of journals extending from the bit body, each journal having a journal axis extending from a base of the journal through the length of the journal;
- a roller cone rotatably mounted to each of the journals; and
- at least one blade protruding from the bit body center and extending radially outward to less than an outer diameter of the drill bit.
2. The drill bit of claim 1, wherein the at least one blade comprises a plurality of cutting elements having planar cutting faces.
3. The drill bit of claim 2, wherein the blades extend to a nose region of the drill bit.
4. The drill bit of claim 2, wherein the blades extend to a shoulder region of the drill bit.
5. The drill bit of claim 1, wherein the plurality of journals extend downward and radially outward such that an acute angle ranging from about 15 degrees to about 25 degrees is formed between the journal axis and the longitudinal bit axis.
6. The drill bit of claim 5, wherein the plurality of roller cone cutting elements having an installation back rake angle ranging from about 10 degrees to about 90 degrees.
7. The drill bit of claim 5, wherein the plurality of roller cone cutting elements having an installation side rake angle ranging from about 0 degrees to about 60 degrees.
8. The drill bit of claims 6 and 7, wherein the plurality of roller cone cutting elements having an equivalent back rake ranging from about 10 degrees to about 30 degrees.
9. The drill bit of claims 6 and 7, wherein the plurality of roller cone cutting elements having an equivalent side rake ranging from about 0 degrees to about 30 degrees.
10. A drill bit, comprising:
- a bit body having a longitudinal bit axis extending there through;
- a plurality of journals, extending from the bit body; and
- a roller cone having an outer diameter rotatably mounted to each of the journals, wherein at least two of the outer diameters are different, and
- wherein an offset angle ranging from about 0 degrees to about 90 degrees is formed between a line perpendicular to the bit axis and extending through the bit axis and a center of a backface of the roller cone.
11. The drill bit of claim 10, wherein the roller cone comprises a plurality of roller cone cutting elements having planar cutting faces, wherein the roller cone cutting elements comprise a roller cone cutting profile.
12. The drill bit of claim 11, wherein the smallest roller cone cutting profile extends an axial height greater than the largest roller cone cutting profile.
13. The drill bit of claim 12, wherein the smallest roller cone cutting profile radially overlaps with the largest roller cone cutting profile.
14. A drill bit, comprising:
- a bit body having a longitudinal bit axis extending there through;
- a plurality of journals, extending from the bit body, each journal having a journal axis extending from a base of the journal through the length of the journal;
- wherein the plurality of journals extend from the bit body such that an acute angle ranging from about 15 degrees to about 25 degrees is formed between the journal axis and the bit axis; and
- a roller cone rotatably mounted to each of the journals, wherein at least one roller cone comprises a plurality of roller cone cutting elements having planar cutting faces and at least one roller cone comprises a plurality of roller cone cutting elements having non-planar cutting faces,
- wherein the roller cone cutting elements comprise a roller cone cutting profile.
15. The drill bit of claim 14, wherein the roller cones each have an outer diameter, and wherein at least two of the outer diameters are different.
16. The drill bit of claim 15, wherein each of the roller cone cutting profiles radially overlaps with one another.
17. The drill bit of claim 16, wherein the plurality of roller cone cutting elements having an installation back rake angle ranging from about 10 degrees to about 90 degrees.
18. The drill bit of claim 16, wherein the plurality of roller cone cutting elements having an installation side rake angle ranging from about 0 degrees to about 60 degrees.
19. The drill bit of claims 17, wherein the plurality of roller cone cutting elements having an equivalent back rake ranging from about 10 degrees to about 30 degrees.
20. The drill bit of claims 17, wherein the plurality of roller cone cutting elements having an equivalent side rake ranging from about 0 degrees to about 30 degrees.
Type: Application
Filed: May 27, 2015
Publication Date: Dec 1, 2016
Inventors: Xiaoge Gan (Houston, TX), Jiaqing Yu (Conroe, TX), Yuelin Shen (Spring, TX), Youhe Zhang (Spring, TX), Yong Zhou (Spring, TX), Jian Wu (Houston, TX)
Application Number: 14/722,193