Patent Grant
7210377
1. Field of the Invention
The invention relates generally drill bits used to drill wellbores through earth formations. More specifically, the invention relates to hardfacing structures applied to drill bits and methods for applying the same so as to reduce erosion of the drill bit during drilling operations.
2. Background Art
Drill bits used to drill wellbores through earth formations generally are made within one of two broad categories of bit structures. Drill bits in the first category are generally known as “fixed cutter” or “drag” bits, which usually include a bit body formed from steel or another high strength material and a plurality of cutting elements disposed at selected positions about the bit body. The cutting elements may be formed from any one or combination of hard or superhard materials, including, for example, natural or synthetic diamond, boron nitride, and tungsten carbide.
Drill bits of the second category are typically referred to as “roller cone” bits, which usually include a bit body having one or more roller cones rotatably mounted to the bit body. The bit body is typically formed from steel or another high strength material. The roller cones are also typically formed from steel or other high strength material and include a plurality of cutting elements disposed at selected positions about the cones. The cutting elements may be formed from the same base material as is the cone. These bits are typically referred to as “milled tooth” bits. Other roller cone bits include “insert” cutting elements that are press (interference) fit into holes formed and/or machined into the roller cones. The inserts may be formed from, for example, tungsten carbide, natural or synthetic diamond, boron nitride, or any one or combination of hard or superhard materials.
Application of hardfacing to the base material from which the cones and drill bit are formed is known in the art. The hardfacing can be applied in the form of special erosion protection inserts used in addition to the cutting elements. See for example, U.S. Pat. No. 3,952,815 issued to Dysart. Another method known in the art that uses hardfacing to protect roller cones is described in U.S. Pat. No. 5,291,807 issued to Dysart. The method in the Dysart '807 patent includes marking the face of a roller cone by masking or etching, applying hardfacing material, such as tungsten carbide, in the form of a powder, and heating the cone to bond the hardfacing powder to the cone. U.S. Pat. Nos. 3,461,983 and 3,513,728 issued to Hudson include disclosure related to drilling holes (sockets) in the cone prior to application of the hardfacing, plugging the holes, and then applying the hardfacing material using a flame application process. After applying the hardfacing material with the flame process, the plugs are removed and the inserts are pressed into the previously drilled sockets.
Moreover, U.S. Pat. No. 5,348,770 issued to Sievers discloses a method for applying hardfacing to a cone which uses a high velocity oxygen fuel (HVOF) spray process after the cone is formed. Forming the cone includes drilling the sockets for the inserts. U.S. Pat. No. 4,396,077 issued to Radtke discloses a method for applying hardfacing to a fixed cutter bit. The method includes generating an electric arc and spraying arc-heated hardfacing material onto a substantially completely assembled bit structure.
In one aspect, the invention comprises a method of forming a drill bit structure, the method comprising affixing a plurality of spacers to the drill bit structure at preselected locations on an outer surface of the drill bit structure. A hardfacing material is applied to the drill bit structure. The plurality of spacers are then removed from the drill bit structure and holes are machined in the drill bit structure proximate the preselected locations. Drilling inserts are positioned in each hole.
In another aspect, the invention comprises a method of forming a drill bit structure, the method comprising machining a plurality of holes at preselected locations in the drill bit structure. Spacer inserts are positioned in each of the plurality of holes. A hardfacing material is applied to the drill bit structure using an arc hardfacing process, and the plurality of spacer inserts are removed from the plurality of holes. Drilling inserts are positioned in each of the plurality of holes.
In another aspect, the invention comprises a method of forming a drill bit structure, the method comprising machining a plurality of holes in preselected locations in the drill bit structure. Spacer insert are positioned in each of the plurality of holes. A hardfacing material is applied to the drill bit structure using an arc hardfacing process, and the plurality of spacer inserts are removed from the plurality of holes. The plurality of machined holes are enlarged to a selected diameter so as to enable disposition of drilling inserts therein, and drilling inserts are positioned in each of the plurality of enlarged holes.
In another aspect, the invention comprises a method of forming a drill bit structure, the method comprising machining a plurality of holes in preselected locations in the drill bit structure. Spacer insert are positioned in each of the plurality of holes. A hardfacing material is applied to the drill bit structure using a high velocity oxygen fuel hardfacing process, and the plurality of spacer inserts are removed from the plurality of holes. The plurality of machined holes are enlarged to a selected diameter so as to enable disposition of drilling inserts therein, and drilling inserts are positioned in each of the plurality of enlarged holes.
In another aspect, the invention comprises a method of forming a drill bit structure, the method comprising machining a plurality of holes at preselected locations in the drill bit structure. Spacer inserts are positioned in each of the plurality of holes. A hardfacing material is applied to the drill bit structure with a high velocity oxygen fuel hardfacing process, and the plurality of spacer inserts are removed from the plurality of holes. Drilling inserts are positioned in each of the plurality of holes.
In another aspect, the invention comprises a method of forming a drill bit structure, the method comprising applying a hardfacing material to selected surfaces of the drill bit structure. The hardfacing material comprises a carbide infiltrated material comprising a plurality of perforations at preselected locations therein and a powder infiltrated material comprising a plurality of perforations therein, the perforations in the powder infiltrated material adapted to correspond to the perforations in the carbide infiltrated material. A plurality of holes are machined in the drill bit structure proximate the plurality of corresponding perforations, and drilling inserts are positioned in each hole.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
Each of three roller cones 16 is rotatably mounted on a corresponding leg 22 proximate the lower end of the bit body 20. A plurality of cutting elements, which in this case comprise inserts 18 that are typically formed from cemented tungsten carbide, are press-fit (or interference fit), brazed, or otherwise affixed in holes (not shown separately in
Referring to
The cones 16 include multiple rows of the inserts 18, and the roller cones 16 generally include a heel portion 17 located between gage row inserts 15 and the O-ring groove 23. A plurality of heel row inserts 30 are approximately equally spaced about a circumference of the heel 17. The heel row inserts 30 and the gage row inserts 15 act together to drill a gage diameter of the borehole 25. The interior row inserts 18 are generally arranged in, for example, concentric rows, and they serve to crush and chip the earth formations being drilled.
As used herein, the term “erosion” refers to both erosion and other abrasive wear. Much of the erosion of the roller cones 16 typically occurs between the gage row inserts 15 and heel row inserts 30. Furthermore, erosion also may occur at lands 27 formed between the gage row inserts 15 and inner row inserts 18. Generally, a “land” refers to a surface on a roller cone where holes (e.g., “sockets”) are drilled so that inserts 18, 15, 30 may be disposed therein. Moreover, erosion may occur in grooves 24 formed between successive inner rows of inserts 18. These areas on a roller cone surface are collectively referred to as “areas susceptible to erosion” and must generally be protected to increase the longevity of the drill bit in both normal and harsh drilling conditions. For example, erosion in these areas may result in damage to the roller cone, loss of the inserts and/or roller cone cracking (particularly between the inserts), and/or a loss of lubrication for the roller cones. In highly erosive environments, the entire cone body may be exposed to severe erosion.
Accordingly, embodiments of the present invention relate to methods of applying hardfacing coatings to roller cones and drill bits so that bit longevity and performance may be extended, especially in harsh drilling conditions. In some embodiments of the invention, hardfacing coatings may be applied with an arc process as described in U.S. Pat. No. 6,196,338 issued to Slaughter et al. and assigned to the assignee of the present invention. For example, the hardfacing may be applied with a plasma transferred arc process (PTA), a gas-shielding tungsten arc (also known as “gas tungsten arc”) welding process, a metal inert gas arc (“gas metal arc”) welding process, and similar processes known in the art.
In some embodiments, an electric arc such as that formed by the PTA process is preferred because an area of a cone heated for application of hardfacing may be closely controlled. Advantageously, close control of the heated area prevents damage to a large area of the cone that may be produced with, for example, an unshielded chemical flame.
The following detailed discussion describes various aspects of the invention. The hardfacing techniques described below may be used to apply a hardfacing coating to any drill bit structure such as, for example, a roller cone or a drill bit shoulder. Accordingly, descriptions related to application of hardfacing coatings to roller cones are not intended to limit the scope of the invention to a single use (e.g., hardfacing roller cones). Further, while some embodiments are described with respect to insertion of cutting elements into machined holes in a drill bit structure, other types of drilling inserts (where the term drilling inserts is intended to include cutting elements), such as gage protection elements, may be used within the scope of the invention. Accordingly, the examples provided in the description below are not intended to be limiting with respect to, for example, a specific type of drilling insert.
In one embodiment of the invention shown in
The spacers 50 may be positioned at selected locations on the surface 52 of the roller cone 54. The positioning of the spacers 50 is adapted to correspond to, for example, desired locations of cutting element inserts that will be affixed to the roller cone 50 after a hardfacing material has been applied thereto. The spacers 50 enable a hardfacing material to be applied to the entire surface 52 of the roller cone 54 without, for example, omitting hardfacing from the desired locations where cutting element inserts (or drilling inserts) and/or gage protection elements are to be disposed. This aspect of the invention helps ensure that a substantially even coating of hardfacing material is applied to the selected areas of the roller cone 54 and/or drill bit (not shown). Moreover, use of spacers 50 may increase a speed of application of the hardfacing material because an operator does not have to spend as much time avoiding application of the hardfacing material to the locations where cutting element inserts will be disposed.
Referring to
After hardfacing has been completed, and because the hardfacing material 56 generally does not adhere to the spacers in the same manner as the hardfacing material 56 adheres to a base metal of the roller cone 54 (e.g., because the hardfacing material 56 generally does not form a metallurgical or mechanical bond with the spacers 50), the portions of the hardfacing material 56 proximate the spacers 50 may be removed so that cutting element insert holes 58 my be drilled as described above. After the holes 58 have been drilled in the roller cone 54, cutting element inserts (not shown) may be affixed in the holes 58 by interference fit, brazing, and/or other means known in the art.
In another embodiment of the invention shown in
Referring to
In another embodiment of the invention shown in
The mushroom caps 90 may be formed from any suitable material known in the art. For example, the mushroom caps 90 may be formed from the materials described above with respect to the spacers and spacer inserts of the previous embodiments.
The previous embodiments related to the use of, for example, inserts as spacers for the positioning of cutting element inserts generally include application of hardfacing materials using the aforementioned arc processes. Moreover, high velocity oxygen fuel (HVOF) processes may also be used to apply hardfacing in these embodiments of the invention. In a preferred embodiment, the hardfacing material is applied via an electric arc process. The electric arc process enables the hardfacing material application to be closely controlled so that, for example, only selected portions of the roller cone and/or drill bit to be hardfaced are heated to elevated temperatures during the hardfacing process.
Advantageously, the above described embodiments of the invention include precise application of a selected pattern of hardfacing material to the roller cone or other surface that is to be coated for erosion protection. In this manner, the invention helps avoid formation of a hardened layer that is difficult to machine when, for example, cutting element inserts holes are later drilled for installation of cutting element inserts.
In another embodiment of the invention shown in
A powder infiltrated layer 72 may then be placed on top of the carbide infiltrated layer 70. The powder infiltrated layer 72 may comprise, for example, Nickel, Boron, Cobalt, Silicon, Chromium, PTFE, and combinations thereof. The roller cone 78, the carbide infiltrated layer 70, and the powder infiltrated layer 72 are then heated in a controlled environment (e.g., in an enclosed oven (not shown) with a selectively controlled atmosphere) to a relatively low temperature so as to vaporize the PTFE. The temperature is then elevated to approximately 900–1200° C. for a selected period of time. At the elevated temperature, the alloys (e.g., Nickel, Cobalt, etc.) in the powder infiltrated layer 72 liquefy, infiltrate the carbide infiltrated layer 70, and thereby form a hardfacing material 74 that becomes metallurgically bonded to the surface 76 of the roller cone 78 (see, e.g.,
Heating of the infiltrated layers 70, 72 may be performed by any means known in the art. For example, the roller cone 78 and/or other parts of the drill bit (including the entire bit in some embodiments) may be placed in an oven and heated to the selected temperatures. In other embodiments, heating may be performed using spot heating sources including lasers, high intensity light sources, induction heating tools, microwave sources, and the like. Accordingly, the type of heat source used to heat the infiltrated layers 70, 72 so as to form the desired metallurgical bond is not intended to be limiting.
In embodiment shown in
In another embodiment of the invention, the infiltrated layers are selectively infiltrated with hardfacing materials so that selected areas of the infiltrated layers comprise substantially only PTFE (or another suitable material) that may be vaporized at a relatively low temperature. After the PTFE (or other suitable material) is vaporized, “gaps” or preformed perforations are formed in the hardfacing material. The gaps are selectively arranged to correspond to desired locations of insert holes (e.g., in rows) that may be machined in a roller cone or other drill bit structure after the hardfacing process has been completed. Accordingly, specially formed infiltrated layers may be developed to correspond to, for example, selected roller cone cutting element geometries, different size roller cones (e.g., for different sizes of drill bits), and the like.
Note that other embodiments may comprise, for example, a carbide infiltrated layer pre-bonded to a powder infiltrated layer (e.g., using a mechanical bond, an adhesive bond, a chemical bond, or similar means known in the art). In these embodiments, perforations in the materials may be pre-aligned so as to ease positioning the materials proximate the surface of the drill bit structure in a desired manner.
Advantageously, the infiltrated material hardfacing process forms a strong metallurgical bond with, for example, the surface of the roller cone. The metallurgical bond is typically stronger (e.g., more resistant to wear and erosion) than a traditional mechanical bond formed by other hardfacing processes. The metallurgical bond provides increased wear resistance and longevity when drilling in, for example, harsh downhole and/or other subsurface environments. Further, the perforations in the infiltrated materials may be closely controlled so as to produce, for example, a closely toleranced cutting element arrangement. Finally, application of the infiltrated cloth to the hardfaced areas may be performed relatively quickly (as compared to, for example, traditional welded application hardfacing processes).
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
This application is a divisional application of U.S. patent application Ser. No. 09/974,735 entitled “CONE EROSION PROTECTION FOR ROLLER CONE BITS,” filed Oct. 10, 2001 now U.S. Pat. No. 6,698,098.
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|---|---|---|---|
| 3513728 | Hudson et al. | May 1970 | A |
| 4679640 | Crawford | Jul 1987 | A |
| 4889017 | Fuller et al. | Dec 1989 | A |
| 5051112 | Keshavan et al. | Sep 1991 | A |
| 5348770 | Sievers et al. | Sep 1994 | A |
| 6454030 | Findley et al. | Sep 2002 | B1 |
| 6568491 | Matthews et al. | May 2003 | B1 |
| 20020035895 | Davies et al. | Mar 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040187290 A1 | Sep 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09974735 | Oct 2001 | US |
| Child | 10774571 | US |
