Patent Application
20080223619
1. Technical Field
The present invention relates in general to drill bits and, in particular, to an improved system, method, and apparatus for passive and active updrill protective and cutting features for oil field tools such as roller cone drill bits.
2. Description of the Related Art
When drilling in formation with unconsolidated, highly abrasive sand formations, the legs of drill bits are subjected to the abrasive cuttings being drilled, the high sand content in the mud, and the sand particles along the borehole wall. Improvements in the shirttail and motor hardfacing and/or a combination of compacts have helped to limit the accelerated wear from occurring to the outer diameter of the legs in the normal (i.e., downward) drilling mode. However, a need exists to help protect the upper leg surfaces above the transition edge (such as compensator areas) from excessive wear, especially when back reaming is performed.
Embodiments of a system, method, and apparatus for providing additional protective and cutting features for oil field tools are disclosed. The invention is well suited for use on the upper leg surfaces of roller cone drill bits above the transition edge of the head outer diameter during up drilling. These objectives are accomplished by strategically placing a volume of metallurgically bonded hardfacing material near the shank end of the drill bit, such as between the leading transition edge and trailing transition edge.
The strategically located hardfacing is typically passive in the normal drill mode, but active in the updrill drilling mode and/or during back reaming. Alternative designs include other strategic material placement, the formation of hardfacing materials in tooth/wear design shapes, bimetallic gage, graded composite hardfacing materials, inverted radius at edges of the outer diameter, and various methods of applying the material also may be employed.
The hardfacing comprises a thickness of at about 0.25 inches or more, which is more than twice as thick as conventional hardfacing (i.e., typically on the order of 0.120 inches or less). This substantial increase in hardfacing thickness is made possible by the locations of the installation, which also facilitate enhanced geometric features (e.g., teeth shapes, etc.). The method of the invention may comprise removing material from the oil field tool above the transition edge edges, backfilling with hardfacing to those edges, optionally adding additional hardfacing above the original surface of the tool, and machining or shaping the hardfacing into various geometric designs. The hardfacing material itself may comprise iron or nickel-based materials. Examples include a matrix of Ni—Cr—B—Si with spherical cast WC. Processes for application of the hardfacing to oil field tools include those known to one skilled in the art, including oxy-acetylene, MIG, TIG, SMA, SCA, etc.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings.
So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
Referring now to
One or more top transition surfaces 51 are located between the head OD 49 and the thread shoulder 47. Transition edges 53 are defined between the head OD 49 and the top transition surfaces 51. Compensator caps 55 are located in at least some of the top transition surfaces 51. One or more leading edge transition surfaces 57 are located on one side of respective ones of the head OD 49 and top transition surfaces 51, and one or more trailing edge transition surfaces 59 are located opposite the leading edge transition surfaces 57 on another side of said respective ones of the head OD 49 and top transition surfaces 51.
The drill bit 31 has a conventional down drilling mode wherein portions of the bit body that are distal to (i.e., below, in vertical drilling) the transition edge 53 are defined as “active” and directly encounter and cut formation during down drilling. The drill bit 31 also has an up drilling mode wherein portions of the bit body that are proximal to (i.e., above) the transition edge 53 and radially inboard of the head OD 49 are defined as “passive” (i.e., does not intentionally cut formation) during down drilling, but which are active during up drilling or back reaming. Accordingly, the portions that are active during down drilling typically become passive during up drilling.
The drill bit 31 also has metallurgically bonded hardfacing material 61 that is strategically located on the passive portions of the bit body. Unlike prior art designs, the hardfacing 61 has a thickness of about 0.25 inches or more. In another embodiment, a thickness of 0.050 inches or more may be used. Hardfacing 61 is for cutting formation and providing wear protection for the bit body during up drilling or back reaming. Accordingly, the hardfacing 61 is located axially above the transition edges 53, and radially inward of the maximum outer diameter of the drill (e.g., at head OD 49). As illustrated in
As shown in the embodiments of
In addition, a portion 77 of the hardfacing 71 also may be located on the compensator caps 55 (see, also,
In the embodiment of
As shown in
Still other alternative designs for the hardfacing include further strategic material placement, the formation of hardfacing materials in tooth/wear design shapes, bimetallic gage, graded composite hardfacing materials, recesses or cavities at edges of the outer diameter, and various methods of applying the material also may be employed. Moreover, material may be removed from the passive portions of the bit body to form cavities. The cavities are then backfilled with hardfacing and comprise additional hardfacing extending out of the cavities above an original surface of the bit body.
The hardfacing material itself may comprise iron or nickel-based materials. Examples include a matrix of Ni—Cr—B—Si with spherical cast WC pellets, and/or spherical sintered WC pellets. Another example may include an iron matrix, again with spherical WC pellets, spherical cast WC pellets, crushed sintered WC, and/or crushed cast WC granules or any combination thereof. Processes for application of the hardfacing to oil field tools include those known to one skilled in the art, including oxy-acetylene, MIG, TIG, SMA, SCA, etc.
Referring now to
While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.
