Drill bit with canted gage insert

Details Drill bit with canted gage insert Drill bit with canted gage insert

1998-06-30

2003-11-04

Lee, Jong-Suk (James) (Department: 3673)

Boring or penetrating the earth

Bit or bit element

Rolling cutter bit or rolling cutter bit element

C175S374000, C175S426000

Reexamination Certificate

active

06640913

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to rolling cone drill bits and to an improved cutting structure for such bits. In one aspect, the invention relates to such bits with canted gage cutting inserts.
BACKGROUND OF THE INVENTION
The present invention relates generally to diamond enhanced inserts for use in drill bits and more particularly to diamond enhanced inserts for use in the gage or near-gage rows of rolling cone bits. Still more particularly, the present invention relates to placement of a diamond coating on an insert and to positioning the insert in a cone such that wear and breakage of the insert are reduced and the life of the bit is enhanced.
An earth-boring drill bit is typically mounted on the lower end of a drill string and is rotated by rotating the drill string at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied by the drill string, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone. The borehole formed in the drilling process will have a diameter generally equal to the diameter or “gage” of the drill bit.
A typical earth-boring bit includes one or more rotatable cutters that perform their cutting function due to the rolling movement of the cutters acting against the formation material. The cutters roll and slide upon the bottom of the borehole as the bit is rotated, the cutters thereby engaging and disintegrating the formation material in its path. The rotatable cutters may be described as generally conical in shape and are therefore sometimes referred to as rolling cones. Such bits typically include a bit body with a plurality of journal segment legs. Each rolling cone is mounted on a bearing pin shaft that extends downwardly and inwardly from a journal segment leg. The borehole is formed as the gouging and scraping or crushing and chipping action of the rotary cones remove chips of formation material that are carried upward and out of the borehole by drilling fluid that is pumped downwardly through the drill pipe and out of the bit. The drilling fluid carries the chips and cuttings in a slurry as it flows up and out of the borehole. The earth disintegrating action of the rolling cone cutters is enhanced by providing the cutters with a plurality of cutter elements.
The cost of drilling a borehole is proportional to the length of time it takes to drill to the desired depth and location. The time required to drill the well, in turn, is greatly affected by the number of times the drill bit must be changed in order to reach the targeted formation. This is the case because each time the bit is changed, the entire string of drill pipe, which may be miles long, must be retrieved from the borehole, section by section. Once the drill string has been retrieved and the new bit installed, the bit must be lowered to the bottom of the borehole on the drill string, which again must be constructed section by section. As is thus obvious, this process, known as a “trip” of the drill string, requires considerable time, effort and expense. Accordingly, it is always desirable to employ drill bits that will drill faster and longer and are usable over a wider range of formation hardnesses.
The length of time that a drill bit may be employed before it must be changed depends upon its rate of penetration (“ROP”), as well as its durability or ability to maintain an acceptable ROP. The form and positioning of the cutter elements on the cutters greatly impact bit durability and ROP and thus are critical to the success of a particular bit design.
Bit durability is, in part, measured by a bit's ability to “hold gage,” meaning its ability to maintain a full gage borehole diameter over the entire length of the borehole. Gage holding ability is particularly vital in directional drilling applications. If gage is not maintained at a relatively constant dimension, it becomes more difficult, and thus more costly, to insert drilling assemblies into the borehole than if the borehole had a constant full gage diameter. For example, when a new, unworn bit is inserted into an undergage borehole, the new bit will be required to ream the undergage hole as it progresses toward the bottom of the borehole. Thus, by the time it reaches the bottom, the bit may have experienced a substantial amount of wear that it would not have experienced had the prior bit been able to maintain full gage. This unnecessary wear will shorten the bit life of the newly-inserted bit, thus prematurely requiring the time-consuming and expensive process of removing the drill string, replacing the worn bit, and reinstalling another new bit downhole.
Cutter elements are generally of two types: inserts formed of a very hard material, such as tungsten carbide, that are press fit into undersized apertures in the cone surface; or teeth that are milled, cast or otherwise integrally formed from the material of the rolling cone. Bits having tungsten carbide inserts are typically referred to as “TCI” bits, while those having teeth formed from the cone material are known as “milled tooth bits.” In each case, the cutter elements on the rotating cutters functionally breakup the formation to form new borehole by a combination of gouging and scraping or chipping and crushing. While the present invention has primary application in bits having inserts rather than milled teeth and the following disclosure is given in terms of inserts, it will be understood that the concepts disclosed herein can also be used advantageously in milled tooth bits.
To assist in maintaining the gage of a borehole, conventional rolling cone bits typically employ a heel row of hard metal inserts on the heel surface of the rolling cone cutters. The heel surface is a generally frustoconical surface and is configured and positioned so as to generally align with and ream the sidewall of the borehole as the bit rotates. The inserts in the heel surface contact the borehole wall with a sliding motion and thus generally may be described as scraping or reaming the borehole sidewall. The heel inserts function primarily to maintain a constant gage and secondarily to prevent the erosion and abrasion of the heel surface of the rolling cone. Excessive wear of the heel inserts leads to an undergage borehole, decreased ROP, increased loading on the other cutter elements on the bit, and may accelerate wear of the cutter bearing and ultimately lead to bit failure.
In addition to the heel row inserts, conventional bits typically include a gage row of cutter elements mounted adjacent to the heel surface but orientated and sized in such a manner so as to cut the corner of the borehole. In this orientation, the gage cutter elements generally are required to cut both the borehole bottom and sidewall. The lower surface of the gage row insert engages the borehole bottom while the radially outermost surface scrapes the sidewall of the borehole. Conventional bits also include a number of additional rows of cutter elements that are located on the cones in rows disposed radially inward from the gage row. These cutter elements are sized and configured for cutting the bottom of the borehole and are typically described as inner row cutter elements.
Differing forces are applied to the cutter elements by the sidewall than the borehole bottom. Thus, requiring gage cutter elements to cut both portions of the borehole compromises the cutter design. In general, the cutting action operating on the borehole bottom is typically a crushing or gouging action, while the cutting action operating on the sidewall is a scraping or reaming action. Ideally, a crushing or gouging action requires a tough insert, one able to withstand high impacts and compressive loading, while the scraping or reaming action calls for a very hard and wear resistant insert. One grade of cemented tungsten carbide cannot optimally perform both of these cutting functions as it cannot be as hard as desired for cutting the sidewall and, at the same time, as tough as desired for cutting the borehole bottom

Affiliated with

Also associated with

Rating

Drill bit with canted gage insert does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Drill bit with canted gage insert, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drill bit with canted gage insert will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3183015