Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Method For Extending The Life Of Thin Walled Tubing And
Austempered Weld Stress Relieved Thin Walled Tubing
INVENTOR: Dan Thomas Benson
BACKGROUND OF THE INVENTION
1: Field Of The Invention
[00011 The present invention is directed to a method of extending the life of
thin walled
tubing by austempering the tubing in a controlled process involving heating,
quenching, and
cooling the tubing pursuant to predetennined process parameters. The invention
is also
directed to a process for austempering tubing having a welded seam and for
relieving residual
stress in the weld. The invention is ftu-ther directed to the product of the
above processes as
well as an austempered weld stress relieved thin walled tubing and such tubing
in
combination with other apparatus with which it is suitable for use in the
production of
hydrocarbons.
2. Description Of The Prior Art
[0002] Each instance tubing is rolled on or off a coil tubing reel, it is
peimanently
elongated. The elongation accumulates until exhausted and the tubing breaks.
Hence,
elongation is a sigr-ificant property of the tubing material.
[0003] The second significant property of tubing material is strength or
hardness. This
quality resists dialation stresses of pressure and tension stresses of
deployinents in deep wells.
[0004] A characteristic of steel is decreasing elongation with increasing
hardness.
Metallurgically, an ideal coil tubing is a paradox: hard for strength in deep
or high pressure
wells, ductile for repetitive reeling.
[0005] Present tecluiology coil tubing steels have a martensitic stiucture.
Martensite has
unfavorable hardness versus elongation trade-off. On the other hand,
austempered steels
have a bainitic stiucture. Bainitic stiuctured steels are not only hard, but
also retain
commendable elongation.
[0006] Austempering of steel is known in the prior art, however it is
typically
accomplished in a non-continuous batch process which is unsuitable for coil
tubing milling.
[0007] Represented by Fig. 1 is the cuirent technology to continuously mill
steel tubing:
metal strip is introduced to a tube formation device, the seam welded and
scarfed, and the
foi-med tubular amiealed, e.g., by heating. The tubing is chilled by cooling
apparatus and
then travels through additional formation devices, e.g., sizing rolls. The
tubular may then be
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heated and cooled again and taken up, e.g., on a reel. By welding the butts of
the strip stock
at the fi-ont end of the process, very long lengths of tubing can be milled.
[0008] In the continuous tube milling process, the sizing operation in Fig. 1
work-hardens
the tubing increasing the strength. The thet-tnal processes depicted in Fig. 1
are either
palliatives for problems caused by welding, or to soften tubing to the desired
grade after
work-hardening. The thermal processes used in present tubing milling
tecltrtology do not
harden the tube.
SUMMARY OF THE INVENTION
[0009] The present inventions are directed toward an apparatus and methods
useful for
increasing the strength of the tubing while maintaining the elongation of thin
walled tubing
by austempering the thin walled tubing. The present invention is further
directed toward a
method for austempering thin walled tubing comprising a welded seam and for
stress
relieving the welded seam. The present invention is also directed toward a
product produced
by the methods and/or processes described above. The present invention is also
directed
toward a thin walled austempered tubing comprising a stress relieved welded
seam.
DESCRIPTION OF THE DRAWINGS
100101 Figure 1 is a schematic overview of a prior art system.
[0011] Figures 2 and 2a are schematic overviews of an exemplary apparatus for
practicing the present inventions' methods.
[0012] Figure 3 is a view in partial perspective of a section of austempered
tubing.
[0013] Figure 3 is a schematic view of an exemplary deploytnent of austempered
tubing
in a well.
[0014] Figure 5 is a block diagram of a first method of the present invention.
[0015] Figure 6 is a block diagram of a second method of the present
invention.
[0016] Figure 7 is a block diagram of a third method of the present invention,
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Referring now to Fig. 2, exemplary apparatus 10 for austempering thin
walled
tubing according to the methods of the present inventions comprises heater 20,
low
temperature reservoir 30, and cooler 40. Apparatus 10 is adapted to be used
with continuous
runs of tubing 12 while practicing the methods of the present invention. As
used herein, a
continuous t-un is one which processes a length of around 200 feet or more in
a single
processing procedure.
[0018] Metallic tubing 12 has a wall thickness of less than 0.25 inches,
preferably around
0.120 inches. In an embodiment, metallic tubing 12 comprises a steel alloy
with a carbon
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content greater than or equal to 0.25 and less than or equal to 0.45 and may
comprise 4130
alloy steel. Metallic tubing 12 may be supplied from source 15 of a
substantially continuous
supply of metal, e.g. a rolled strip, and formed in to a tubular at tube
foimer 90. Seams
created by tube formation may be welded at seam welder 91 and the formed seam
scarfed at
scarfer 92.
[0019] Heater 20 is adapted to accept a section of inetallic tubing 12 and
heat the section
to a high temperature in the range of 1300 - 1600 F. Heater 20 may comprise
an induction
heater and/or a flame or the like, or a combination thereof. Heater 20, e.g.
an induction
heater, may be located proximate to or within low temperature reservoir 30.
100201 Low temperature reservoir 30 is adapted to accept a moving section of
metallic
tubing 12 as part of a continuous nin process and to reduce the temperature of
the section of
metallic tubing to a first low temperature in the range of 500 - 1000 F in a
time period of
less than 3 seconds. Low temperature reservoir 30 as used for quenching may
comprise a
molten salt bath. Moving may be accomplished by numerous equivalent means
including by
using rollers.
[00211 Cooler 40 is adapted to cool a section of metallic tubing 12 to a
second low
temperature below 100 F. Cooling cooling may be accomplished by numerous
equivalent
means including by forced convection. Additional coolers may be present, e.g.
water cooler
93, as is practiced in the art.
[0022] Additional processing may occur after the second cooling. For exainple,
austempered metallic tubing 12 may be sized at sizing rollers 94 and cooled
further by
coolers 96 and 97.
[0023] Austempered metallic tubing 12 may then be talcen up, e.g. at takeup
reel 17.
[0024] Austempered thin walled welded tube 12 may be coiled on a reel, e.g.,
takeup reel
17,which may be further mounted on ship 16 (Fig. 2a).
[0025] Referring to Fig. 3, austempered thin walled welded tube 12 may
comprise first
end region 12a adapted to be attached to device 19, e.g. a motor, an overshoot
jar, an
intensifier, a landing nipple, a plug catcher, a casing scraper, a snake pin,
a downllole tool, a
valve, or the like. Austempered thin walled welded tube 12 may further
comprise second end
region 12b opposite first end region 12a which may be adapted to be further
connected to
device 18, e.g. a pump.
[0026] Austempered, thin walled, and stress relieved welded tubing 12 may be
produced
by any of the exemplary methods described herein. Moreover, thin walled welded
tube 12
produced by any of the exemplary methods described herein may comprise an
austempered
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cylindrical body created as part of the continuous run processes ot those
methods where the
austempered cylindiical body comprises first seam edge 12c, second seam edge
12d, and a
wall having a thickness of less than 0.25 inches. Thin walled welded tube 12
may fiu-ther
comprise stress relieved welded seam 12e join'ing the first and second seam
edges.
[0027] Referring now to Fig. 4, in an exemplary embodiment thin walled welded
tube 12
is unspooled from takeup reel 17. One end of thin walled welded tube 12 is
comlected to
pump 18 and the other end deployed tluough well casing 90 and/or production
tubing 91,
tenninating in tool 19.
[0028] In the operation of exemplary embodiments, refening now to Fig. 5, in a
first
exemplary method for austempering thin walled tubing, a section of metallic
tubing 12 (Fig.
2a) is heated to a high temperature in the range of 1300-1600 F in heater 20
(Fig. 2a). The
section of metallic tubing 12 has a wall thiclcliess of less than 0.25 inches,
preferably around
0.120 inches.
[0029] After being heated, the section of heated metallic tubing 12 (Fig. 2a)
is moved
from heater 20 (Fig. 2a) to low temperature reservoir 30 (Fig. 2a) as part of
a continuous run
process. While in low temperature reservoir 30, the section of metallic tubing
12 is quenched
to reduce the temperature of the section of metallic tubing 12 to a first low
temperature in the
range of 500-1000 F in a time period of less than 3 seconds. Processing the
section of
metallic tubing 12 may comprise a time-temperature-transformation cuive where
the start of
conversion to austentite-ferrite is at least 0.75 seconds after quenching in
low temperature
reservoir 30.
[0030] The section of metallic tubing 12 (Fig. 2a) is allowed to transform to
bainite and
then moved out of low temperature reservoir 30 (Fig. 2a) as part of the
continuous run
process and cooled to a second low temperature below around 100 F. Cooling
may be by
forced convection, e.g. at cooler 40 (Fig. 2a).
[0031) In a second exemplary method, referring to Fig. 6, a further exemplary
method for
austempering thin walled coiled tubing 12 (Fig. 2a) comprises extending a
section of thin
walled metallic tubing 12 having a wall thicl:ness of less than 0.25 inches
from a coil
mounted about reel 15 (Fig. 2a) into heater 20 (Fig. 2a) as pait of a
continuous run process.
The section of metallic tubing 12 is heated to a higli temperature in the
range of 1300 - 1600
F in heater 20 and then moved from heater 20 to low temperature reservoir 30
(Fig. 2a) as
part of the continuous run process. In low temperature reservoir 30, the
section of metallic
tubing 12 is quenched in low temperature reservoir 30 to reduce the
temperature of the
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section of metallic tubing 12 to a first low temperature in the range of 500 -
1000 F in a time
period of less than around 3 seconds.
[0032] The section of metallic tubing 12 (Fig. 2a) is allowed to transform to
bainite and
then the section of metallic tubing 12 transformed into bainite is moved out
of low
temperature reservoir 30 (Fig. 2a) as part of the continuous iun process and
cooled to a
second low temperature below around 100 F, e.g. at cooler 40 (Fig. 2a).
[0033] After it reaches the second low temperature, the section of metallic
tubing may be
coiled, e.g. about reel 17 (Fig. 2a).
[0034] In a third exemplary method, refernng now to Fig. 7, a section of thin
walled
metallic tubing 12 (Fig. 2a) having a welded seam and a wall thickness of less
than 0.25
inches is extended from a coil mounted about reel 15 (Fig. 2a) into heater 20
(Fig. 2a) as
part of a continuous run process. The section of metallic tubing 12 is heated
to a high
temperature in the range of 1300 - 1600 F in heater 20 (Fig. 2a) and then
moved from heater
20 to low temperature reseivoir 30 (Fig. 2a) as part of the continuous run
proccss. hi low
temperature reseivoir 30, the section of metallic tubing 12 is quenched to
reduce the
temperature of the section of metallic tubing 12 to a first low temperature in
the range of 500
- 1000 F in a time period of less than around 3 seconds.
[0035] The section of metallic tubing 12 (Fig. 2a) is then allowed to
transfonn to bainite.
The section of metallic tubing 12 transfonned to bainite is then moved out of
low temperature
reservoir 30 (Fig. 2a) as part of the contlnUOUs run process cooled to a
second low
temperature below around 100 F, e.g. at cooler 40 (Fig. 2a).
[0036] The foregoing disclosure and description of the inventions are
illustrative and
explanatory. Various changes in the size, shape, and materials, as well as in
the details of the
illustrative construction and/or a illustrative method may be made without
departing from the
spirit of the invention.
