Note: Descriptions are shown in the official language in which they were submitted.
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MECHANICAL PARTS HAVING INCREASED WEAR RESISTANCE
CROSS-REFERENCE TO RELATED APPLICATIONS
.[0oo1] This application claims priority to United States Provisional patent
application
serial number 60/745,228, filed April 20, 2006, the entirety of which is
hereby incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] This invention pertains of borided parts for wear surfaces in equipment
for use in
earth boring, well completion and fluid extraction.
BACKGROUND OF THE INVENTION
[0003] Oil exploration is a spjcializecl process that combines elegant
scientific models
and brute force prospecting. Seismic prospecting techniques employ sound waves
to find
probable oil reserves thousands of feet below the Earth's surface, and
sophisticated modeling
techniques are used to characterize the geology of those locations. Once a
likely site is
identified, a hole is drilled into the ground until oil or gas is found or the
driller decides to
abandon the site for a likelier prospect. At some sites, the hole is drilled
using a top head
drive attached to a length of hollow pipe. As the hole becomes deeper, extra
sections are
added to the pipe. In addition, a continuous stream of drilling "mud," an
aqueous slurry
containing clay and other chemicals, is pumped through the drill pipe and
through holes in
the drill bit to cool the bit. The mud also coats the side of the hole to
prevent collapse and
carries crushed rock to the surface. The mud is pumped into the hole by a mud,
or slush,
pump.
[00041 The drill bit has to cut through rock and gradually wears. In
addition,'the mud and
the cuttings traveling to the surfacx.e.~wear not only the drill bit but
components of the mud
pump. Drilling (and mud pumping) is conducted 24 hours a day, but if any of
the parts wear
out, the entire operation may need to be halted while the part is repaired.
The components of
the mud pump, located at the surface, are easily accessible. On the other
hand, the entire
length of thousands of feet of hollow pipe have to be removed section by
section to replace
the drill bit. As a result, it is desirable to increase the useable lifetime
of all the wearing parts
used in oil drilling.
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DEFINITIONS
[0005] As used herein, the terms "boriding" and "boronizing" are used
interchangeably
and indicate the development of a;boron-containing layer on a metal substrate,
such that
boron diffuses into the metal and reacts with a component of the metal or a
component of the
metal diffuses to the boron-containing layer and reacts with the boron, or
both.
[0006] As used herein, the term "fluid extraction" refers to the removal of
oil, natural gas,
water, and/or other fluids from underground.
[00071 As used herein, the term "metallic" refers to a material that includes
at least 50%
metal elements (e.g., Fe, Ti, Zn, etc.) in a metallic, intermetallic, or alloy
phase. In some
embodiment, the material may include at least 60%, at least-70%, at least 80%,
at least 90%,
or at least 95% metal elements in a metallic, intermetallic, or alloy phase.
[00081 As used herein, the terms "mud pump" and "slush pump" are used
interchangeably.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention is described with reference to the several figures of the
drawing, in
which,
[0010] Figure 1 is an exploded view of a piston and liner for use in an
exemplary mud
pump (Gardner Denver Service Manual 15-504).
[0011] Figure 2 is a cross-sectional view of an exemplary mud pump (Gardner
Denver
Service Manual 15-603, page 11)
[0012] Figure 3 is an exploded view of a valve for use in an exemplary mud
pump
(Gardner Denver Service Manual 15-504 p 9).
[00131 Figures 4A and B are micrographs of cross-sections of two steel samples
after
boriding at A) 1700 F for 8 hr and B) 1500 F for 24 hr.
[00141 Figure 5 is a graph illustrating the change of hardness (HV5o) with
depth for
various borided components (1 V and 2V: Valve bodies; IS and 2S: Valve seats).
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE
INVENTION
[0015] In one embodiment, at least a first, portion of a surface of a
component for use in
combination with a second component during earth-boring, well completion
(e.g., fracturing
and cementing the well after drilling), or fluid extraction comprises a
metallic material and is
borided. In certain embodiments, the borided portion does not wear against a
metallic surface
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of the second component during use. In some embodiments, the component is not
a tricone
bit. The component may be fabricated from a ferrous or non-ferrous metal or
metal alloy. In
some embodiments, the metal or metal alloy may be steel, titanium, or a
titanium or
chromium alloy. In certain embodiments, the first portion is substantially
metallic, or may be
at least 80% metallic, at least 85% metallic, at least 90% metallic, or at
least 95% metallic.
[0016] Various equipment for use in earth-boring, well completion, and fluid
extraction
can benefit from the teachings of the invention. During exploration and
drilling for fluids
such as oil, natural gas, and water; drilling hardware is subjected to
abrasive, erosive, and
corrosive conditions. These wear modes reduce the useful life of hardware
components and
increase drill rig operating costs. The teeth of drill bits used in oil and
gas exploration and
drilling are often made from cemented tungsten carbide, due to its resistance
to abrasion and
erosion. However, due to the difficult nature of working with tungsten
carbide, fabrication of
the teeth for drill bits is complex, labor intensive, and costly. Steel teeth,
which are easier
and less costly to fabricate, are sometimes used, however they may not be
sufficiently wear-
resistant for some applications. The surface of the drill bit, the roller
cones to which the teeth
are secured, and the nozzle from which drilling mud is directed into the drill
hole are often
fabricated from steel as well. Boriding can increase the wear resistance of
all of these
components, allowing them to be fabricated from steel or other metals instead
of tungsten
carbide or other cermets or metal-matrix composites. Wear also is a problem
for many other
components used in oil and gas drilling, such as, for example, radial and
thrust bearings,
mechanical couplings, wear pads, flow i,diverters and restrictors, mud pump
liners, and
impellers.
[0017] Additional parts that may benefit from boriding include various fishing
tools,
apparatus to recover parts from within a bore. Because these components tap a
thread in the
component to secure themselves to the component, they often can only be used
once for a
particular size component, after which the tap/thread is too worn to recover a
second
component of the same size. These tools are often tapered and thus can be used
to recover a
component having a larger diameter even after the smaller diameter regions
become worn.
However, boriding can harden the surface sufficiently that the fishing tool
can be used two or
more times to recover parts from a bore. Exemplary fishing tools include but
are not limited
to spears, taper taps, and overshots.
[0018] Many other components of exploration and drilling equipment are subject
to wear
by corrosion, abrasion, or erosion, including, for example, radial and thrust
bearings,
mechanical couplings, wear pads, -flow divdrters and restrictors, mud and
cement pump liners
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and impellers, drill pipes, valves, directional drilling assemblies, hanger
assemblies, fishing
tools (e.g., spears, taper taps, and overshots), percussion assemblies,
nozzles, and core lifters.
Many different coating methods have been tried for improving the abrasion and
co'rrosion
resistance of these components. These include thermal spraying and application
carbide
composite coatings, as well as nickel and chrome plating. While these coatings
can improve
the life of the part, further improvements can provide dramatic decreases in
downtime and
replacement costs.
[0019] During earth-boring, mud pumps are used to circulate pumping mud in the
drill
hole as the mud carries cuttings to the surface. The extent and mode of wear
to the pump
components is determined by the abrasiveness, particle concentration, particle
size, velocity,
pH, and other characteristics of the particles and the fluid as well as the
operating conditions
of the pump such as flow rate, pressure, etc. Depending on the site, pumps may
need to run
continuously for weeks or months at a time. Wear results in part from the flow
of particles
within the mud abrading the surfaces of the pump's components. As the surfaces
of these
components wear away even a small amount, the ability of a pump to maintain
pressure and
convey the pumping mud becomes greatly diminished. When pump components wear
beyond a certain limit and begin to perform below acceptable process limits,
the pumps
and/or process lines must be shut down and the components or entire pumps must
be
replaced.
[0020] In an exemplary embodiment, at least some of the metal bearing surfaces
of a
mud, or slush, pump are borided=. Figure I is an exploded view of an exemplary
piston for
use in an exemplary mud pump. Piston rod 1, pump liner 5, and piston hub 6 all
have metal
bearing surfaces. Figure 2 is a cross=sectional view of a mud pump. In
addition to the piston
and its associated components, the pump also includes two valves 20, shown in
exploded
view in Figure 3. Both valve body 23 and valve seat 24 have metallic bearing
surfaces. It is
contemplated that all of these components can experience improved tribological
properties
and performance as a result of boriding.
[0021] It is contemplated that other components employed in earth-boring, well
completion, and fluid extraction may also benefit from boriding. For example,
DTH (down
the hole) hammer bits wear against rock as they drill the well, while the
internal components
of the hammers wear against each other. While these hammer bits often have
carbide inserts,
it is contemplated that the lifetime of the metallic portions of the hammer
bit may also be
extended by boriding. Fracturing tubes may be abraded andlor corroded by the
fracturing
fluid. Valve seats and valve bodies abrade against the pumping mud but also
against each
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other. Drill pipes are initially abraded bythe pumping mud, foam (air
drilling), brine, and the
rock it carries out of the well and later by fluids being extracted by the
well and any
particulate matter they carry. Drill pipes may also be corroded by fluids such
as water that
are pumped into the well. Abrasion of core lifters can reduce the length of
cores that can be
cut and brought to the surface and, in extreme cases, can jeopardize the
cohesion of the core
sample, making recovery difficult. Directional drilling assemblies may
experience uneven
wear as a result of the deviation of the drilling direction from the vertical.
Plungers for
cement pumps abrade against the rocks in the cement and are also chemically
eroded by the
elevated pH of lime-based materials. Flow diverters and flow restrictors may
wear not only
from particulates in the extracted fluid but also from the fluid itself. It is
contemplated that
boriding of radial and thrust bearings may not only reduce wear but may also
reduce fatigue
by reducing friction during use. Additional parts that may benefit from
boriding include but
are not limited to mechanical couplings, wear pads, impellers, hanger
assemblies, percussion
.. ,
assemblies, nozzles, rollers, cams, anfl shatfts.
(0022] As discussed above, the lifetime of drilling and pump parts that are
constantly
abraded by rock from a well is determined in part by the tribological
properties of the
components. The use of diffusion-based treatments such as nitriding,
carburization, and
boriding to increase surface hardness and resistance to wear is well known.
Boriding can
produce a harder surface than nitriding or carburization and is suitable for
some steel alloys
for which nitriding or carburization are less optimal. Boriding also improves
the corrosion
resistance and reduces the coefficient of friction more than carburization,
increasing the
lifetime of parts. Even a 10% improvement in part life can create immense
savings over the
course of drilling and completing a single well. Other techniques for
increasing surface
hardness include the simple deposition of a boron-containing layer at the
surface of a
material. For example, electrochemistry may be employed to form a layer of
iron boride at
the surface of a component. Alternatively, superabrasive composites including
materials
such as diamond or cubic boron nitride may be electroplated onto metallic
components, or
metaUmetal boride mixtures may be thermally sprayed onto components. However,
layers
formed by these methods may not be chemically or mechanically integrated with
the bulk
material. Boriding provides greater integration of the boron-containing layer
with the
substrate. This integration increases the strength of the interface between
the boride-
containing layer and the substrate, further reducing galling, tearing,
seizing, and other forms
of wear in which a material flakes from the surface.
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[0023] A variety of boriding techniques may be used to improve the tribology
of wearing
parts for use in earth-boring, well completion, and fluid extraction. In some
embodiments,
boriding includes two processes: the generation of a thin boride layer at the
surface of the
material and the growth of that layer by diffusion into the bulk material. In
some cases, the
depth of the boron-containing diffu'sion zone may be over seven times thicker
than the
surface boride layer (ASM Handbook, Volume'4, ASM International, Materials
Park, OH,
1994). The diffusion layer increases the resistance of the layer to
delamination and also helps
reduce cracking resulting from differential rates of thermal expansion during
processing. In
addition, diffusion of the boron into the bulk material may improve the
fatigue performance
of the component.
[0024] An exemplary boriding method is pack boriding. A boron-containing
powder is
packed around a workpiece in a refractory container and heated. Alternatively,
a paste may
be applied to the workpiece and heated, or a fluidized bed may be employed. In
another
embodiment, boriding may be performed with a gas or plasma, allowing the
boriding to be
performed without annealing the core of the work piece, which can lead to
grain coarsening
and softening of the base material. Plasma boriding also allows quicker
diffusion of reactive
elements and higher velocity impact of reactive boron species against the
surface of the
workpiece. In some embodiments, if may'be desirable to have a hardened surface
around a
more malleable core. The surface heating imposed during plasma boriding allows
the
difference in mechanical properties between the various regions of the part to
be maintained.
Exemplary boriding methods are disclosed in U.S. Patents Nos. 3,926,327,
4,610,437,
4,637,837, and 6,783,794. In another embodiment, a potassium haloborate may be
decomposed to the potassium halide salt and the boron trihalide, which is then
fed into an
inert gas stream for plasma boriding. In one embodiment, the potassium
haloborate is
potassium fluoroborate. It is contemplated that this technique facilitates
boriding of larger
parts more cheaply and safely than plasma boriding techniques employing
organoborates or
boron halides.
(0025] It is contemplated that use of boriding to surface harden components
allows them
to be made from materials that are not traditionally employed in earth-boring.
For example,
pump liners are often fabricated from chromium-containing steels. However, the
use of a
borided surface may enable these components to be fabricated from chromium
alloys,
titanium, and titanium alloys, for example, Ti-6A1-4V, Ti-6A1-6V-2Sn, Ti-1OV-
2Fe-3A1,
Ti-0.3Mo-0.8Ni, Ti-0.2Pd, etc. TiB2 has a hardness of 3300 vickers, which can
greatly
improve the lifetime of components fabricated from borided titanium-containing
metals.
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[0026] In another embodiment, a system for preparing a well for fluid
extraction includes
a first component having a surface, at least a first portion of which
comprises a metallic
material that is borided. In certain embodiments, the system further includes
a second
component having a metallic portion, and the first portion does not wear
against the metallic
portion during use. In certain embodiments, the component is not a tricone
bit. In certain
embodiments, the system includes a drill, a mud pump, a cement pump, and/or a
fracturing
tube. The system may also include sqgments of a well liner.
[0027] In a further embodiment, a method of preparing a component for wearing
against
a material transported during earth-boring, well completion, or fluid
extraction, the
component having a stirface, at least a portion of which comprises a metallic
material,
includes boriding at'least the first portion. In certain embodiments, the
component is not a
tricone bit.
[0028] In a further embodiment, at least a first portion of an interior
surface of a pump
liner for use in earth-boring, well completion, or fluid extraction is
borided. In another
embodiment, a first portion of a surface of a component for use in earth-
boring, well
completion, or fluid extraction includes a substantially metallic material
that is borided.
According to another embodiment of the invention, the component is a valve
seat, valve
body, mud pump liner, piston hub, sucker rod, piston rod, fishing tool, or
plunger.
= EXEMPLIFICATION
Example 1: Boronization of Valve Seat and Valve Body
[0029] A valve seat and valve body were borided by pack boriding. One sample
was
borided for 8 hours at 1700 F; the second was treated for 24 hours at 1500 F.
Micrographs
of the boride layer, showing the sawtooth pattern frequently observed in
borided steels, are
shown in Figures 4A and B. The sample treated at 1700 F had a solid boride
layer of
0.0041" and a total boride layer depth of 0.0064". The sample treated at 1500
F had a solid
boride layer of 0.0037" and a total boride layer depth of 0.0046". HV25 was
measured
(ASTM E 384-99E1, Vickers indenter, 50 g load) at a depth of 0.002" below the
surface and
was 2018 and 1926 for the samples treated at 1700 and 1500 , respectively,
while HV5oo
measured at the (unborided) core was 156 and 162, respectively, an improvement
of about
12-13%. Figure 5 is a graph of HV50 for borided valve bodies, seats, and a
liner, measured
across a cross section of a sample prepared to a 1 micron final polish.
Example 2: Field Testing of Boronized Valve Seat and Valve Body
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[0030] Four borided valve bodies and valve seats, with urethane insert, as
well as four
non-borided valve bodies and valve seats (control), with urethane inserts,
were installed on a
Continental Emsco DB 550 Duplex mud pump. The pump was run under normal
operating
conditions for four months, at which point the non-borided parts had to be
replaced. The
borided parts continued to work effectively.
[0031] Other embodiments of the invention will be apparent to those skilled in
the art
from a consideration of the specification or practice of the invention
disclosed herein. It is
intended that the specification and examples be considered as exemplary only,
with the true
scope and spirit of the invention being indicated by the following claims.
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