Two piece mold used in manufacture of PDC drill bits and method of using same
A graphite core mold having its own cavity is pressed into a cavity of a graphite shell mold. The core cavity is filled with tungsten carbide, mixed with a nickel alloy, heated and then cooled to thereby provide a carbide matrix body. After milling the carbide matrix body to thereby provide a carbide bit body, the intact shell mold is removed and then used again.
This invention relates generally to the manufacture of fixed cutter drill bits used to drill oil and gas wells.
Various types of drill bits have been developed and found useful in different drilling environments. Bits typically used for drilling boreholes in the oil and gas industry include roller cone bits and fixed cutter bits. Cutting structures on bits vary depending on the type of bit and the type of formation being cut. Roller cone cutting structures typically include milled steel teeth, tungsten carbide inserts, or diamond enhanced inserts. Cutting structures for fixed cutter bits typically include polycrystalline diamond compacts, commonly referred to as “PDC” cutters. The selection of a bit type and cutting structure for a given drilling application depends on many factors including the formation type to be drilled, rig equipment capabilities, and the time and cost associated with drilling.
It is common in the art of manufacturing PDC, fixed cutter drill bits, to manufacture the carbide matrix body of the drill bit in a graphite mold. Such a mold known in the prior art is typically made with a single mold manufactured from graphite.
Fixed cutter drill bits, also referred to as fixed head bits or drag bits, are generally more expensive than mill tooth roller cone drill bits and are considered to offer less aggressive cutting structures than roller cone drill bits. However, in several applications, fixed cutter bits can be used to drill longer well segments in a single run and can be rebuilt and reused multiple times to provide an overall economic benefit that outweighs the higher cost. Fixed cutter bits which include PDC cutters are typically referred to as PDC bits.
Referring now to the drawings in more detail,
In using the single piece mold of the prior art illustrated in
Referring now to
The funnel 38 through which the nickel alloy and the tungsten carbide powder is filled, allows the tungsten carbide powder and the nickel alloy to go into the cavity within the mold core 32 as illustrated in
Claims
1. A mold for forming a carbide matrix PDC bit body, comprising:
- a cylindrical shell having a closed end, an open end and a cavity commencing with the open end of said shell;
- a cylindrical core having a closed end, an open end, and a cavity commencing with the open end of said core, said core having an outside diameter sized to closely fit within the inside diameter of the cavity within said shell, wherein the cavity within the core can be filled with a mixture of tungsten carbide powder and particles of a metallic alloy, which when heated and then cooled and then milled, form a carbide matrix PDC bit body.
2. The mold according to claim 1, wherein said core comprises graphite.
3. The mold according to claim 2, where said shell comprises graphite.
4. The mold according to claim 1, wherein the closed end of said core and the closed end of said shell are pressed against each other.
5. The mold according to claim 1, wherein said metallic alloy comprises nickel.
6. A method for molding a carbide matrix body for a PDC drill bit, comprising the steps of:
- pressing a graphite core into a graphite shell;
- pouring tungsten carbide powder and particles of a metallic alloy into a cavity in said core;
- melting the mixture of the powder and the particles within the cavity in the core;
- cooling the molten mixture to thereby provide a carbide matrix body;
- removing the intact shell from around the core;
- milling the carbide matrix body with the desired features of a PDC drill bit; and
- removing the core from the carbide matrix body.
7. The method according to claim 6, including the repetition of the steps according to claim 6, using the same graphite shell in the repeated process.
8. The method according to claim 6, wherein the metallic alloy comprises nickel.
Type: Application
Filed: Oct 24, 2008
Publication Date: Apr 29, 2010
Inventors: Michael M. Tomczak (Cypress, TX), Vincente S. Salvo (Spring, TX), Juan Rios (Houston, TX)
Application Number: 12/288,889
International Classification: B22D 23/00 (20060101); B21K 5/04 (20060101);