Rolling cone bit with elements fanned along the gage curve

Details Rolling cone bit with elements fanned along the gage curve Rolling cone bit with elements fanned along the gage curve

2001-05-18

2003-11-25

Bagnell, David (Department: 3672)

Boring or penetrating the earth

Bit or bit element

Specific or diverse material

C175S341000, C175S378000

Reexamination Certificate

active

06651758

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to earth-boring bits used to drill a borehole for the ultimate recovery of oil, gas or minerals. More particularly, the invention relates to rolling cone bits and to an enhanced cutting structure for such bits. Still more particularly, the invention relates to the placement of gage cutter elements on the rolling cone cutters at locations that increase bit durability and rate of penetration.
BACKGROUND OF THE INVENTION
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 to the drill string, the rotating drill bit engages the earthen formation and proceeds to drill 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. As used herein, “bit diameter” and “gage diameter” refer to the same parameter.
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 on the bottom of the borehole as the bit is rotated, with the cutters engaging and disintegrating the formation material in the path of the bit. The rotatable cutters may be described as generally conical in shape and are therefore sometimes referred to as rolling cones. Rolling cone bits typically include a bit body with a plurality of journal segment legs. The rolling cones are mounted on bearing pin shafts that extend downwardly and inwardly from the journal segment legs. Each cone includes a plurality of cutter elements in its outer conical surface. The borehole is formed as the gouging and scraping or crushing and chipping action of the rotary cones remove chips of formation material. The chips are carried upward and out of the borehole by a drilling fluid, which is pumped downwardly through the drill pipe and out of the bit, and recirculates to the surface via the annulus between the drill pipe and the borehole wall.
The earth disintegrating action of the rolling cone cutters is enhanced by the cutter elements. 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 “steel 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.
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 that are usable over a wider range of formation hardness.
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 upon 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, which have become increasingly important. If gage is not maintained relatively constant, it becomes more difficult, and thus more costly, to insert drilling apparatus into the borehole than if the borehole had a constant 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 fall 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.
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 oriented 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 that are 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.
In general, the cutting action of the cutter elements at the borehole bottom is typically a crushing or gouging action, while the cutting action at the sidewall is a scraping or reaming action. Because differing forces are applied to the cutter elements by the sidewall than the borehole bottom, it is desired to separate these cutting duties so that the corresponding cutter elements can be optimized.
One U.S. Patent that teaches the separation of sidewall and bottom cutting duties is U.S. Pat. No. 5,372,210. U.S. Pat. No. 5,372,210 teaches the benefits of distributing the inserts on each rolling cone such that a more rounded borehole corner is formed. The '210 patent provides a “transition row” of cutter elements, which drill the rounded corner between the vertical sidewall and the borehole bottom. The purpose of this configuration is to reduce concentrated side forces and to facilitate directional drilling while minimizing gage wear. The '210 patent further provides an arrangement whereby the gage row insert diameter on each rolling cone is different than the others. Additionally, the '210 p

Affiliated with

Also associated with

Rating

Rolling cone bit with elements fanned along the gage curve does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rolling cone bit with elements fanned along the gage curve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rolling cone bit with elements fanned along the gage curve will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3151687