U.S. patent application number 11/212035 was filed with the patent office on 2006-05-04 for high chrome/nickel milling with pdc cutters.
Invention is credited to Rustom K. Mody, Brad R. Pickle, Calvin J. Stowe.
Application Number | 20060090897 11/212035 |
Document ID | / |
Family ID | 35276089 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090897 |
Kind Code |
A1 |
Stowe; Calvin J. ; et
al. |
May 4, 2006 |
High chrome/nickel milling with PDC cutters
Abstract
A method of downhole milling of an item having high chrome/high
nickel content, using polycrystalline diamond cutting elements,
exhibiting less wear, requiring less torque and weight, and
producing less heat, than prior art tungsten carbide elements.
Inventors: |
Stowe; Calvin J.; (West
University Place, TX) ; Mody; Rustom K.; (Bellaire,
TX) ; Pickle; Brad R.; (Houston, TX) |
Correspondence
Address: |
GERALD W. SPINKS
P. O. BOX 5242
GLACIER
WA
98244
US
|
Family ID: |
35276089 |
Appl. No.: |
11/212035 |
Filed: |
August 23, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60604201 |
Aug 24, 2004 |
|
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|
Current U.S.
Class: |
166/298 ;
166/55.7 |
Current CPC
Class: |
E21B 10/567 20130101;
E21B 29/00 20130101 |
Class at
Publication: |
166/298 ;
166/055.7 |
International
Class: |
E21B 29/00 20060101
E21B029/00 |
Claims
1. A method for downhole milling of material having high nickel
content or high chrome content, or both, said method comprising:
provide a mill body adapted to be attached to a work string, with
at least one row of polycrystalline diamond cutting elements
mounted adjacent to a peripheral surface of said mill body; lower
said mill body into a well bore; rotate said mill body in a
selected direction about a longitudinal axis of said mill body to
mill said material having high nickel content or high chrome
content with said polycrystalline diamond cutting elements.
2. The method recited in claim 1, further comprising: provide each
said cutting element in said at least one row with a cutting face
oriented substantially toward said selected direction of rotation
of said mill body, with a major transverse dimension on each said
cutting face, said major transverse cutting face dimension being
measured substantially transverse to said selected direction of
rotation of said mill body; and space apart adjacent said cutting
elements in said at least one row, said spacing being measured
substantially along a line parallel to said longitudinal axis of
said mill body; wherein said spacing between any two adjacent
cutting elements in said at least one row is at least 20% of said
major transverse cutting face dimension on either of said two
adjacent cutting elements.
3. The method recited in claim 1, further comprising orienting said
at least one row of said cutting elements substantially along a
spiral line along the periphery of said mill body.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application relies upon U.S. Provisional Patent
Application No. 60/604,201, filed on Aug. 24, 2004, and entitled
"High Chrome/Nickel Milling with PDC Cutters."
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention is in the field of mills used for downhole
milling of metal objects, in an oil or gas well.
[0005] 2. Background Art
[0006] Metals with over 12% chrome, or over 6% nickel, or over 12%
chrome in combination with over 6% nickel, present unique cutting
challenges. Specifically, such metals require substantially more
energy to cut, and produce significantly greater cutter wear than
conventional metals. They exhibit unusually high friction between
the cutter and the base material being cut, and between the cutter
and the chip being formed. Previously known methods of cutting
these materials involved the use of tungsten carbide cutters. When
these materials are being cut with these conventional tungsten
carbide cutters, the cutters suffer heavy breakage, wear quickly,
require considerably more load and torque, and tend to vibrate or
chatter severely. These tungsten carbide cutters exhibit a
relatively high coefficient of friction with the high chrome and
high nickel materials. The high coefficient of friction increases
torque by increasing the sliding force between the cutter and the
base material or substrate.
[0007] The high friction also increases the force required to make
the chip flow up the tungsten carbide cutter face. This increased
force requirement directly increases the cutting load, as the force
required to hold the tungsten carbide cutter down into the cut is
increased. This increased force requirement also indirectly
increases the cutting load, as the chip tends to form a hard "ball"
of the material being cut around the outer edge of the tungsten
carbide cutter, which effectively blunts the cutter edge.
[0008] An important result of the higher friction, higher load, and
duller edge is that considerable heat is generated at the cut by
the tungsten carbide cutters. This heat increases the wear rate of
the conventional tungsten carbide cutters, and the elevated
temperature generally increases the strain-to-failure
characteristics of the high chrome/high nickel materials, which
further increases the cutting energy required.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention comprises the downhole cutting of high
chrome/high nickel materials with a cutting tool which is dressed
with polycrystalline diamond (PDC) cutters as the primary cutting
elements.
[0010] The novel features of this invention, as well as the
invention itself, will be best understood from the attached
drawings, taken along with the following description, in which
similar reference characters refer to similar parts, and in
which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] FIG. 1 is a side elevation view of a first embodiment of a
mill used according to the present invention;
[0012] FIG. 2 is a partial side elevation view of a second
embodiment of a mill used according to the present invention;
[0013] FIG. 3 is a lower end elevation view of the mill shown in
FIG. 2; and
[0014] FIG. 4 is a third embodiment of a mill used according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The PDC material of the cutters used according to the
present invention, being composed largely of diamond, exhibits less
wear by virtue of its hardness, but more importantly has a much
lower coefficient of friction with the high chrome/high nickel
materials. The low coefficient of friction reduces torque by
reducing the sliding force between the cutter and the base material
or substrate. The low friction also reduces the force required to
make the chip flow up the cutter face. This low friction directly
reduces the cutting load, as the force to hold the cutter down into
the cut is reduced, and it indirectly reduces the cutting load, as
the chip does not tend to form a hard "ball" of the material being
cut around the outer edge. This effectively leaves a sharper cutter
edge. An important result of the lower friction, the lower load,
and a sharper edge is that considerably less heat is generated at
the cut, by the PDC cutters. This lower heat generation decreases
the wear rate of the PDC cutters, and the lower temperature
generally decreases the cutting energy required.
[0016] As shown in FIG. 1, a first embodiment of a mill 10 for use
in the present invention has a mill body 12, on the periphery of
which are arranged and mounted a plurality of PDC cutting elements
14. The PDC cutting elements 14 can be arranged in a plurality of
spiral rows 16, arranged generally along the axial dimension of the
mill body 12. The mill 10 is designed to be rotated in a selected
direction, clockwise when viewed from the top end 18, for the mill
shown. The cutting face 20 of each cutting element 14 is oriented
toward the direction of rotation. The distance 22 between any two
adjacent cutting elements 14 in any given row 16, measured along a
line parallel to the longitudinal axis of the mill body 12, is a
minimum of 20% of the diameter of the cutting face 20 of either of
the two adjacent cutting elements 14.
[0017] As shown in FIG. 2, the spiral rows 16 of cutting elements
14 can be paired, with each such pair having a leading row 24 and a
trailing row 26, with the leading row 24 being in front of the
trailing row 26, relative to the selected direction of rotation.
The cutting elements 14 in the trailing row 26 can be aligned to
follow in the cutting paths established by respective cutting
elements 14 in the leading row 24. The cutting elements 14 can be
substantially cylindrical, with circular cutting faces 20 as shown,
or they can have other shapes, without departing from the present
invention. The cutting elements 14 can be mounted directly on the
mill body 12 as shown, or they can be mounted on cutting blades
(not shown) on the mill body, as is known in the art. The cutting
elements 14 can be mounted on the lateral periphery 28 of the mill
body 12, and they can be mounted on the lower end face 30 of the
mill body 12, as shown in FIG. 3. The mill body 12 can be generally
tapered from a larger diameter at the upper end 18 thereof to a
smaller diameter at the lower end 30 thereof, or it can be
cylindrical or any other shape known in the art.
[0018] As shown in FIG. 4, a fourth embodiment of the mill used in
the present invention can have a mill body 32 with an extended
tapered shape, with an even greater axial separation between any
two adjacent cutting elements 14 in a given row 16.
[0019] In operation, according to the present invention, the mill
10 is rotated while contacting the item to be milled, which is made
of a material having a high chrome/high nickel content. The PDC
cutting elements 14 remove chips or cuttings of metal from the
substrate of the item being milled. Because of the greater hardness
and lower coefficient of friction exhibited by the PDC cutting
elements, as compared to the prior art tungsten carbide cutting
elements, the required torque to turn the mill is less, the
required vertical force applied is less, and the cutting edges of
the cutting elements 14 remain sharper. In addition, less heat is
generated than with the prior art tungsten carbide cutting
elements, and the rate of cutting element wear is less than with
the prior art tungsten carbide cutting elements.
* * * * *