Rotary drag bit and methods therefor

Abstract

A rotary drag bit includes a bit body having a face and an axis, a plurality of blades extending radially and longitudinally outward from the face, and at least one split cutter set. The split cutter set includes a plurality of cutters, where at least two of the cutters are primary and / or kerfing cutters located on different blades of the plurality of blades. The pair of primary and / or kerfing cutters of the split cutter set may be located substantially the same radial distance from a center line, or axis of rotation, of the bit and located at substantially the same longitude, or elevation, on the bit as one another, or follow substantially the same rotational or helical cutting path as each other. In addition, at least one backup cutter may be located substantially the same radial distance from a center line, or axis of rotation, of the bit and located at substantially the same longitude, or elevation, on the bit as one or both primary and / or kerfing cutters, or follow substantially the same rotational or helical path as one or both of the primary and / or kerfing cutters. The cutters of a split cutter set may be configured and oriented to provide improved bit life and reduced stress on the cutters. Other embodiments of rotary drag bits are also provided, including methods therefor.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 897,457, filed Jan. 25, 2007, for “ROTARY DRAG BIT,” the entire disclosure of which is hereby incorporated herein by this reference.TECHNICAL FIELD[0002]The present invention, in several embodiments, relates generally to a rotary drag bit for drilling subterranean formations and, more particularly, to rotary drag bits having select plural kerfing cutter configurations configured to enhance cutter life and performance, including methods therefor.BACKGROUND[0003]Rotary drag bits have been use for subterranean drilling for many decades, and various sizes, shapes and patterns of natural and synthetic diamonds have been used on drag bit crowns as cutting elements. A drag bit can provide an improved rate of penetration (ROP) over a tri-cone bit in many formations.[0004]Over the past few decades, rotary drag bit performance has been improved with the use of a p...

AI Technical Summary

Benefits of technology

[0010]Embodiments of a rotary drag bit include a bit body having a face and an axis, a plurality of blades extending longitudinally and radially over the face, and at least one split cutter set. Each cutter of the split cutter set includes a cutting surface protruding at least partially from, or exposed beyond, a surface of a blade of the drag bit. All of the cutters of a split cutter set are located substantially the same radial distance from the central axis of the bit and may be located at substantially the same elevation along the central axis of the bit or at locations that enable them to substantially traverse a common cutting path upon rotation of the bit body about its central axis. A split cutter set includes a first primary cutter on a first blade and a corresponding second primary cutter on a different, second blade. One of the first and second primary cutters may be a so-called “kerfing cutter,” which largely follows the cutting path of the other primary cutter, but removes additional material from the formation into which the drag bit is drilling. A split cutter set also includes at least one backup cutter positioned rotationally or helically behind the first primary cutter or the second primary cutter so as to follow substantially the same cutting path as the primary cutter behind which it is positioned. In some embodiments, one or more backup cutters may be provided for each primary cutter of a split cutter set. Such a split cutter set enables faster drilling while reducing stress upon the cutters. In this respect, the lives of the cutters of the bit are extended and the bit is more durable than comparable conventional drag, bits, extending the life of the rotary drag bit.

Problems solved by technology

While the PDC cutting element improves drill bit efficiency in drilling many subterranean formations, the PDC cutting element is nonetheless prone to wear when exposed to certain drilling conditions, resulting in a shortened life of a rotary drag bit using such cutting elements.

The decrease in the penetration rate is a manifestation that the cutting elements of the rotary drag bit are wearing out, particularly when other drilling parameters remain constant.

While researchers continue to develop and seek out improvements for longer lasting cutters or generalized improvements to cutter performance, they fail to accommodate or implement an engineered approach to achieving longer drag bit life by maintaining or increasing ROP by taking advantage of cutting element wear rates.

Also, it is believed that conventional backup cutters in combination with their associated primary cutters may undesirably lead to balling of the blade area with formation material.

Images