Rotating cutting elements for pdc bits

Abstract

A drill bit has a bit body, a plurality of blades extending radially from the bit body, at least one rolling cutter pocket disposed on the plurality of blades, and at least one rolling cutter, wherein each rolling cutter is disposed in one of the rolling cutter pockets, and wherein a side surface of the rolling cutter pocket and an outer circumferential surface of the rolling cutter have at least one mating lip and channel formed therein. Further, the rolling cutter may include a cavity extending at least partially along a rotational axis through the rolling cutter, from a bottom surface of the rolling cutter, and a retention pin disposed within the cavity.

Description

BACKGROUND[0001]1. Technical Field[0002]Embodiments disclosed herein relate generally to cutting elements for drill bits or other tools incorporating the same. More specifically, embodiments disclosed herein relate generally to rotatable cutting elements for rotary drill bits.[0003]2. Background Art[0004]Drill bits used to drill wellbores through earth formations generally are made within one of two broad categories of bit structures. Depending on the application / formation to be drilled, the appropriate type of drill bit may be selected based on the cutting action type for the bit and its appropriateness for use in the particular formation. Drill bits in the first category are generally known as “roller cone” bits, which 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 p...

AI Technical Summary

Problems solved by technology

Additionally, the bit and the PDC cutters may be subjected to substantial abrasive forces.

In some instances, impact, vibration, and erosive forces have caused drill bit failure due to loss of one or more cutters, or due to breakage of the blades.

Without proper flow characteristics, insufficient cooling of the cutters 150 may result in cutter failure during drilling operations.

Specifically, alloys suitable for brazing cutting elements with diamond layers thereon have been limited to only a couple of alloys which offer low enough brazing temperatures to avoid damage to the diamond layer and high enough braze strength to retain cutting elements on drill bits.

Cracking (and / or formation of micro-cracks) in the bit body can also occur during the cutter brazing process in the area surrounding the cutter pockets.

The formation and propagation of cracks in the matrix body during the drilling process may result in the loss of one or more PDC cutters.

A lost cutter may abrade against the bit, causing further accelerated bit damage.

Conventional polycrystalline diamond is stable at temperatures of up to 700-750° C. in air, above which observed increases in temperature may result in permanent damage to and structural failure of polycrystalline diamond.

Upon heating of polycrystalline diamond, the cobalt and the diamond lattice will expand at different rates, which may cause cracks to form in the diamond lattice structure and result in deterioration of the polycrystalline diamond.

Damage may also be due to graphitization at diamond-diamond necks leading to loss of microstructural integrity and strength loss, at extremely high temperatures.

Exposure to heat (through brazing or through frictional heat generated from the contact of the cutter with the formation) can cause thermal damage to the diamond table and eventually result in the formation of cracks (due to differences in thermal expansion coefficients) which can lead to spalling of the polycrystalline diamond layer, delamination between the polycrystalline diamond and substrate, and conversion of the diamond back into graphite causing rapid abrasive wear.

As a cutting element contacts the formation, a wear flat develops and frictional heat is induced.

As the cutting element is continued to be used, the wear flat will increase in size and further induce frictional heat.

The heat may build-up that may cause failure of the cutting element due to thermal mis-match between diamond and catalyst discussed above.

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