U.S. patent application number 15/945537 was filed with the patent office on 2019-04-18 for device and method for enhacning well perforating.
The applicant listed for this patent is Peng DAI, Bo QU. Invention is credited to Peng DAI, Bo QU.
Application Number | 20190113315 15/945537 |
Document ID | / |
Family ID | 66095696 |
Filed Date | 2019-04-18 |
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United States Patent
Application |
20190113315 |
Kind Code |
A1 |
DAI; Peng ; et al. |
April 18, 2019 |
DEVICE AND METHOD FOR ENHACNING WELL PERFORATING
Abstract
A perforation enhancement cap for a shaped charge contains a
shell and a pack of a solid propellant disposed inside the shell.
The shell has a tubular straight section and a rounded cap. The
rounded cap has a hole. The propellant pack has a through hole. The
straight section, the rounded cap, the hole in the rounded cap, as
well as the through hole are disposed about a common longitudinal
axis. The through hole has a conical frustum section with its
larger base facing the inside of the enhancement cap. The
enhancement cap is adapted to receive the shaped charge to-form an
enhanced perforation charge assembly for perforation and fracturing
the formation.
Inventors: |
DAI; Peng; (Xi'an, CN)
; QU; Bo; (Xi'an, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAI; Peng
QU; Bo |
Xi'an
Xi'an |
|
CN
CN |
|
|
Family ID: |
66095696 |
Appl. No.: |
15/945537 |
Filed: |
April 4, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62574118 |
Oct 18, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B 1/028 20130101;
E21B 43/117 20130101 |
International
Class: |
F42B 1/028 20060101
F42B001/028; E21B 43/117 20060101 E21B043/117 |
Claims
1. A perforation enhancement cap for a shaped charge, comprising: a
shell and a pack of a solid propellant, wherein the shell comprises
a tubular straight section with a first end and a second end, and a
rounded cap having a hole, wherein the rounded cap is connected to
the first end of the tubular straight section, the second end of
the tubular straight section is adapted to be coupled with a shaped
charge, wherein the propellant pack resides in a cavity formed by
the rounded cap and the tubular straight section, and the
propellant pack has a through hole in alignment with the hole in
the rounded cap, and wherein the tubular straight section, the
rounded cap, the hole in the rounded cap, and the through hole are
coaxially aligned.
2. The perforation enhancement cap of claim 1, wherein the through
hole in the propellant pack has a conical frustum section connected
with an optional straight section, wherein an opening angle of the
conical frustum is in the range of 90.degree. to 150.degree..
3. The perforation enhancement cap of claim 2, wherein the opening
angle of the conical frustum is in the range of 90.degree. to
120.degree..
4. The perforation enhancement cap of claim 2, wherein the opening
angle of the conical frustum is in the range of 120.degree. to
150.degree..
5. The perforation enhancement cap of claim 2, wherein the diameter
of the optional straight section equals the diameter of the hole in
the rounded cap, and is in the range of 10-40 mm.
6. The perforated enhancement cap of claim 2, wherein the through
hole is in the propellant pack is in the shape of a conical
frustum, wherein the hole facing the rounded cap is the smaller
base in the conical frustum.
7. The perforation enhancement cap of claim 1, wherein the rounded
cap is a spherical cap having an inner diameter of 14-80 mm and a
height of 10-30 mm.
8. The perforation enhancement cap of claim 7, wherein the tubular
straight section has a height in the range of 8-30 mm, an inner
diameter in the range of 28-58 mm, and an outer diameter of 30-60
mm.
9. The perforation enhancement cap of claim 1, wherein the
propellant pack has a weight in the range of 6-50 grams.
10. The perforation enhance cap of claim 2, wherein the propellant
pack is in the shape of a conical frustum without a straight
section.
11. The perforation enhancement cap of claim 1, wherein the
propellant comprises 30-70 wt % of ammonium perchlorate, 10-30 wt %
aluminum powder, 10-15 wt % additive, and 3-5 wt % dioctyl
sebacate.
12. The perforation enhancement cap of claim 11, wherein the
additive comprises hydroxyl-terminated polybutadiene (HTPB).
13. The perforation enhancement cap of claim 12, wherein the
additive is a mixture of HTPB, N, N'-diphenyl-p-phenylenediamine,
and toluene di-isocyanate (TDI) at a weight ratio of
(2.85-7):(0.05-0.2):(3-7.8).
14. An enhanced perforation charge assembly for formation
perforation, comprising a shaped charge and the perforation
enhancement cap of claim 1 coaxially mounted on a front-face of the
shaped charge.
15. The enhanced perforation charge assembly of claim 14, wherein
the shaped charge contains an explosive pack having a weight of 6
to 80 grams and the perforation enhancement cap contains a
propellant pace having a weight of 6 to 50 grams.
16. A method for formation perforation, comprising: lowering a
perforating gun into a borehole, wherein the perforating gun
comprises the enhanced perforation charge assembly of claim 14; and
detonating the enhanced shaped charge of claim 14.
Description
RELATED APPLICATION
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn. 119 to U.S. Provisional Application No. 62/574,118,
filed on Oct. 18, 2017, the entire contents of which are hereby
incorporated by reference.
FIELD OF TECHNOLOGY
[0002] This disclosure relates generally to oil & gas field
services, particularly to devices and methods for enhancing well
perforation.
BACKGROUND
[0003] Perforation is frequently used in oil or gas well completion
nowadays. In this context, a borehole is drilled down past the
formation desired for oil or gas production (i.e., the pay zone).
Casing is installed between the borehole and the formation to
separate them from each other. A perforating gun is lowed into the
borehole to a desired depth and pay zone. The perforating gun is a
tubular device that carries many shaped charges. A shaped charge
has a metal case, explosives inside charge cavity, and conical
liner. The explosive in the shaped charge is then detonated, the
charge produces a jet of metal particles penetrating the casing,
cement, and into the surrounding formation. These jets thereby
punch many holes on the casing wall and many perforation tunnels in
the formation. The formation around the perforation tunnels is
crushed and compacted as a result, forming a crush zone in the
formation. The permeability of the crush zone may be much less than
the initial undamaged formation impeding the flow into from the
formation into the wellbore.
[0004] U.S. Pat. No. 9,835,014 discloses a perforation assembly
having a shaped charge and a case having a fracture explosive which
is attached to the open-face of the shaped charge. The fracture
explosive case and the shaped charge is coaxially disposed to a
common longitudinal axis. The fracture explosive enters the
perforation tunnel following the perforation jet and produces ample
energy that eliminates the crush zone and creates micro-fractures
and induced fractures in the formation around the perforation
tunnel. Fractures increases the formation permeability, which
results in oil and gas well production enhancement. However, if the
design of the assembly with the fracture explosive is improper, the
fracture explosive may interfere with the perforating jet so as to
reduce the effectiveness of perforation, even causing the failure
of perforation. Accordingly, there is a need for a perforation
charge assembly that eliminates or reduces the crush zone, creates
fractures and increases the permeability after perforation.
SUMMARY
[0005] In view of the aforementioned needs, this disclosure
provides a perforation enhancement cap, which is designed to be
amounted on the open-face of the shaped charge, contains a shell
and a pack of a solid propellant disposed inside the shell. The
shell has a tubular straight section and a rounded cap. The rounded
cap has a hole. The propellant pack has a through hole. The
straight section, the rounded cap, the hole in the rounded cap, as
well as the through hole are disposed about a common longitudinal
axis. The through hole has a conical frustum section with its
larger base facing the inside of the enhancement cap. The
enhancement cap is adapted to receive the shaped charge to form an
enhanced perforation charge assembly.
[0006] In some embodiments, the through hole in the propellant pack
has a conical frustum section connected with an optional straight
section. The opening angle of the conical frustum is in the range
of 90.degree. to 150.degree., for example, 90.degree. to
120.degree. or 120.degree. to 150.degree..
[0007] In other embodiments, the diameter of the straight section
equals the diameter of the hole in the rounded cap, and is in the
range of 10-40 mm. The length of the straight section is in the
range of 0-40 mm.
[0008] In still other embodiments, the rounded cap is a spherical
cap having an inner diameter of 14-80 mm and a height of 10-40 mm.
The tubular straight section has a height in the range of 8-30 mm,
an inner diameter in the range of 28-58 mm, and an outer diameter
of 30-60 mm.
[0009] In further embodiments, the propellant pack has a weight in
the range of 6-50 grams, up to 100 grams. Such an enhancement cap
can be mounted to the open-face of a shaped charge to form a
perforation charge assembly. The corresponding shaped charge has an
explosive pack having a weight of 6-80 grams. The perforation
charge assembly is installed in a perforation gun.
[0010] The propellant contains 30-70 wt % of ammonium perchlorate,
10-30 wt % aluminum powder, 10-15 wt % additive, and 3-5 wt %
dioctyl sebacate. The additive contains hydroxyl-terminated
polybutadiene (HTPB), for example, it is a mixture of HTPB, N,
N'-diphenyl-p-phenylenediamine, and toluene di-isocyanate (TDI) at
a weight ratio of (2.85-7):(0.05-0.2):(3-7.8).
[0011] This disclosure also provides an enhanced perforation charge
assembly for formation perforation, which has a shaped charge and
the enhancement cap. The enhanced perforation charge assembly is
installed in a perforating gun and lowered into a wellbore. Upon
the detonation of the enhanced perforation charge assembly, the
perforation jet creates perforation tunnel and carries the
propellant into the tunnel. The propellant ignites in the tunnel
and creates fractures in the formation. The outer diameter of the
perforating gun is 2''-3.5'', 3.5''-5'', or can be above 5''.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1A and 1B are two views of a perforation enhancement
cap in this disclosure.
[0013] FIG. 2 is a schematic illustration of an enhanced
perforation charge assembly having a shaped charge and the
perforation enhancement cap.
[0014] FIG. 3 is a testing apparatus for monitoring pressure in the
perforation tunnel created by detonation of the enhanced
perforation charge assembly.
[0015] FIG. 4A is a sectional view of one embodiment of the
perforation enhancement cap in this disclosure.
[0016] FIG. 4B is a sectional view of a comparative perforation
enhancement cap.
[0017] FIG. 5 shows the pressure surge in a perforation tunnel
created in the testing apparatus of FIG. 3 produced by an
embodiment of the perforation enhancement cap in this
disclosure.
[0018] FIG. 6 shows the pressure surge in a perforation tunnel
created in the testing apparatus of FIG. 3 produced by a
comparative perforation enhancement cap.
[0019] FIG. 7 compares oil well productions for wells perforated
with the enhanced perforation charge assembly with those using
regular shaped charges without the perforation enhancement cap.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Reference will now be made in detail to embodiments,
examples of which are illustrated in the accompanying drawings,
wherein like reference numerals refer to the like elements
throughout the several views. In this regard, the present
embodiments may have different forms and should not be construed as
being limited to the descriptions set forth herein. Accordingly,
the embodiments are merely described below, by referring to the
figures, to explain aspects of the present description. Terms used
herein are for descriptive purposes only and are not intended to
limit the scope of the disclosure. The terms "comprises" and/or
"comprising" are used to specify the presence of stated elements,
steps, operations, and/or components, but do not preclude the
presence or addition of one or more other elements, steps,
operations, and/or components. The terms "first," "second," and the
like may be used to describe various elements, but do not limit the
elements. Such terms are only used to distinguish one element from
another. These and/or other aspects become apparent and are more
readily appreciated by those of ordinary skill in the art from the
following description of embodiments of the present disclosure,
taken in conjunction with the accompanying drawings. The figures
depict embodiments of the present disclosure for purposes of
illustration only. One skilled in the art will readily recognize
from the following description that alternative embodiments of the
structures and methods illustrated herein may be employed without
departing from the principles of the disclosure described
herein.
[0021] FIGS. 1A and 1B present two views of an embodiment of the
perforation enhancement cap 10. The enhancement cap 10 has a shell
11, which has a straight section and a rounded, substantially
spherical cap. The tubular straight section has a height (H) in the
range of 0-40 mm (e.g., 8-30 mm), an inner diameter (B) in the
range of 28-58 mm, and an outer diameter (A) of 30-60 mm. In this
embodiment, the thickness of the wall of the ring is 1-2 mm. The
radius of the spherical cap (J) is 15-80 mm. The shell 11 houses a
pack of propellant 12. The propellant pack 12 has a shape that
resembles the top half of a sliced bagel, having a flat round base
and a dome-shaped top with a through hole F inside. The propellant
pack 12 is fitted into the spherical cap of the shell, where the
through hole F in the propellant pack is aligned with, and has a
same or smaller diameter than the opening in the spherical cap. The
through hole F in the propellant pack is in the shape of a funnel,
with a wide, conical frustum top portion and a narrower, straight
"stem." The length of the straight stem can be adjusted according
to the weight of the propellant pack and is in the range of 0-40
mm. The larger base of the conical frustum opens to the inside of
the cap. The opening angle of the conical frustum is in the range
of 50.degree.-150.degree.. The weight of the propellant pack is
6-50 grams.
[0022] The propellant has a composition of 30-70 wt % of ammonium
perchlorate (e.g., 30-40 wt %, 30-50 wt %, or 50-70 wt %), 10-30 wt
% aluminum powder (e.g., 10-15 wt %), 10-15 wt % additive, 3-5 wt %
dioctyl sebacate, e.g., 1-4 wt %. The additive is
hydroxyl-terminated polybutadiene (HTPB). The additive can also be
a mixture of HTPB, N, N'-diphenyl-p-phenylenediamine, and toluene
di-isocyanate (TDI) at a weight ratio of
(2.85-7):(0.05-0.2):(3-7.8).
[0023] In the first embodiment of the enhancement cap, the
propellant pack weighs about 6-20 grams of the propellant. The
straight section of the shell 11 is a straight tube having a height
(H) in the range of 10-20 mm, e.g., 10-18 mm or 12-16 mm. The inner
diameter of the straight tube (B) is in the range of 25-41 mm (e.g.
28-38 mm or 30-38 mm) while its outer diameter (A) is 30-46 mm
(e.g., 32-44 mm or 36-42 mm). In this embodiment, the thickness of
the wall of the straight tube is 1 mm. The spherical cap has a
round hole in the top of a diameter of 10-18 mm. The radius of the
spherical cap (J) is 34-49 mm, e.g., 40-48 mm.
[0024] The enhancement cap of the first embodiment, the base radius
of the through hole D1 (i.e., the larger base of the conical
frustum) of the propellant pack is in the range of 16-35 mm (e.g.,
18-30 mm or 20-30 mm) and the diameter of the straight stem D2 is
from 10-18 mm (e.g., 12-16 mm), coincide with the hole in the
spherical cap. The height of the stem section of the propellant
pack is in the range of 1-20 mm, e.g., 1-10 mm or 10-18 mm. The
opening angle R1 of the conical frustum in the propellant pack is
from 80.degree.-150.degree., for example, 85.degree.-140.degree.,
100.degree.-130.degree., 110.degree.-120.degree.. This embodiment
of enhancement cap is particularly suitable for a perforating gun
having an outer diameter of 2''-3.5''.
[0025] In the second embodiment of the enhancement cap, the
propellant pack weighs about 15-50 grams of the propellant. The
straight section of the shell 11 has a height (H) in the range of
10-30 mm, e.g., 12-28 mm or 18-26 mm. The inner diameter of the
straight tube (B) is in the range of 36-48 mm (e.g. 36-46 mm or
40-44 mm) while its outer diameter (A) is 42-58 mm (e.g., 45-55 mm
or 50-55 mm). In this embodiment, the thickness of the wall of the
straight tube is 1 mm. The spherical cap has a round hole in the
top, which has a diameter of 18-30 mm. The radius of the spherical
cap (J) is 49-79 mm, e.g., 50-65 mm or 65-75 mm.
[0026] Further, the base radius of the through hole D1 (i.e., the
diameter of the larger base of the conical frustum) of the
propellant pack is in the range of 20-45 mm (e.g., 20-40 mm or
25-35 mm) and the diameter of the straight stem D2 is from 18-30 mm
(e.g., 20-28 mm). The height of the stem section of the propellant
pack is in the range of 10-40 mm, e.g., 15-35 mm or 18-35 mm. The
opening angle R1 of the conical frustum in the propellant pack is
from 90.degree.-150.degree., for example, 90.degree.-140.degree.,
100.degree.-130.degree., or 110.degree.-120.degree.. This
embodiment of enhancement cap is particularly suitable for a
perforating gun having an outer diameter of 3.5''-5''.
[0027] The enhancement cap 10 can be installed on a shaped charge
20 as shown in FIG. 2. Referring to FIG. 2, the enhancement cap 10
is coaxially mounted on the open-face of shaped charge 20. The
shaped charge 20 has a charge case 21, and a metal liner 22
coaxially disposed inside the charge case 21. The charge case 21
and the liner 22 form a cavity in between, which is filled with an
explosive material 23. The back end of the charge case 21 has a
detonating semi-circle slot 24 for holding a detonating cord. The
detonating semi-circle slot 24 is in communication with the
explosive material 23 through a detonating hole 25. Upon
denotation, the power and heat released from the explosive material
23 collapses and melts the metal liner 22, forming a metal jet
penetrating the well casing, cement and shooting into the
surrounding formation via the through hole in the enhancement cap
10.
[0028] Without being bound by the theory, it is believed that the
energy and heat released by the explosive material 23 disintegrates
the propellant pack 10. The propellant travels with the jet through
the casing into the formation tunnel, where the propellant releases
more energy. With the additional boost of energy from the
propellant, the metal jet penetrates deeper into the formation.
Also, more fractures are created in the compact zone, increasing
permeability. Nevertheless, it is noticed that if the enhancement
cap is not properly design, the propellant may not ignite at the
proper time or proper location, reducing the effectiveness of the
enhancement cap. In the extreme, the propellant may explode in the
perforating gun, causing the failure of perforation.
[0029] In this regard, various designs of the enhancement cap have
been tested. FIG. 3 shows a device for testing the enhancement cap.
The assembly of the shaped charge 320 and the enhancement cap 310
are placed in a pressure proof container 304. Two hooks 303 are
provided on the container. The shaped charge is detonated by a
detonator 306, generating a metal jet shooting into the target tube
311, which is filled with water 307. The target tube 311 has a
pressure relief valve 312 installed thereon and is affixed to a
base 313. Sensors 301, 302, 308, and 309 measure the pressure at
their respective locations continuously and send the signals to be
recorded.
[0030] One aspect of this test is to simulate the pressure profile
in the perforation tunnel in the formation. For example, if there
is only one pressure peak at the positions of sensors 308 and 309,
it would mean that the propellant may have ignited outside the
perforation tunnel. If instead there are two pressure spikes, it
would indicate that the propellant is ignited inside the
perforation tunnel in the formation for the first pressure spike is
likely caused by the initial metal jet and the second pressure
spike is caused by the ignition of the propellant in the
perforation tunnel.
EXAMPLE 1
[0031] FIG. 4A shows an inventive embodiment of the enhancement cap
A having a propellant pack A that weighs 12.3 grams. FIG. 4B shows
a comparative example--the enhancement cap A having a propellant
pack B that weighs 13.5 grams. However, the propellant pack A has a
through hole with a diameter of 27 mm at its larger base and a
diameter of 16 mm in the straight stem portion. The conical frustum
of the through hole in the propellant pack has an opening angle of
85.degree.. In contrast, the propellant pack B has a through hole
with a diameter of at its base is 30 mm and a diameter of 7 mm in
the stem section.
[0032] FIG. 5 shows a pressure-time curve with propellant pack A,
detected by sensor 308. It clearly shows a secondary pressure wave
following a first pressure peak. The secondary pressure wave
arrived 7.5 ms after the detonation, peaked at between 10 ms to 20
ms, then trailed off to zero at 127 ms. The total duration of the
pressurization was 127 ms. First pressure peak caused by the
explosive in the shaped charge was over 100 MPa while the secondary
pressure wave produced by propellant reached the peak value of 32.8
MPa. The duration of the pressurization above 25 MPa was about 20
ms. More data about these tests are presented in Table 1.
TABLE-US-00001 TABLE 1 2.sup.ndary Pressure Wave 1.sup.st Pressure
Peak Stating Measuring Peak Pressure Point Duration Impulse Point
(MPa) (MPa) (ms) (ms) (MPa s) Channel 1 >100 32.8 7.51 127 1.53
Sensor 308
[0033] In comparison, the enhancement cap with the propellant pack
B was also tested, the results are shown in FIG. 6 and Table 2.
TABLE-US-00002 TABLE 2 1.sup.st Pressure Measuring Peak Duration
Impulse Point (MPa) 2.sup.nd Pressure Wave (ms) (MPa S) Channel 1
>200 negligible None None Sensor 308
[0034] As shown in FIG. 6 and Table 2, the detonation created only
one pressure surge with no secondary pressure wave. Although the
peak pressure surpassed 200 MPa, it only lasted a few milliseconds.
Therefore, propellant pack B would not be able to create more
fracturing in the compact zone surround the perforation tunnel.
EXAMPLE 2
[0035] The performance of enhancement caps A and B were tested by
shooting at steel bars. In these experiments, caps A and B were
respectively combined with the same type of shaped charge. The
enhanced perforation charge assembly was placed on top of a steel
bar and detonated, creating a perforation hole in the steel
bar.
[0036] Table 3 compares the results from the shaped charge with or
without the enhancement cap A.
TABLE-US-00003 TABLE 3 Penetration Avg. Avg. Steel Depth Opening
Size Depth Diameter Cylinder No. Charge Configuration (mm) (mm)
(mm) (mm) 1 without Cap A 178 11.1 .times. 11.7 169 11 2 without
Cap A 160 10.4 .times. 11.1 3 with Cap A 180 12.8 .times. 11 171 12
4 with Cap A 163 12.3 .times. 12.1 5 with Cap A 172 12 .times. 12.4
6 with Cap A 169 11.6 .times. 12.3
[0037] Table 4 compares the results from the shaped charge with or
without the enhancement cap B.
TABLE-US-00004 TABLE 4 Steel Target Charge Penetration Opening Size
No. Configuration Depth (mm) (mm) 7 with Cap B 131 10.4 * 11.2 8
with Cap B 143 11.3 * 10.9 9 with Cap B 137 10.1 * 10.8 Average 137
10.8
[0038] The shaped charge without any enhancement cap created
perforation tunnels about 169 mm long on average and openings about
11 mm in diameter on average. The shaped charge equipped with the
enhancement cap A created perforation tunnels having an average
length of 171 mm and an average opening diameter of 12 mm. In
comparison, the shaped charge equipped with the enhancement cap B
created an average penetration length of 137 mm and an average
opening diameter of 11 mm.
[0039] It is believed that the perforation tunnel in steel bar was
mainly created by the first pressure peak because the second
pressure wave does not have sufficient energy to lengthen or
enlarge the tunnel in steel. Therefore, the results from the shape
charge with cap A is only slightly better than that of the shaped
charge alone. However, the penetration by the shaped charge with
cap B is about 20% less than by the shaped charge only while the
size of the opening in the steel bar was practically the same. The
result suggests that the enhancement cap B may have hindered the
metal jet, possibly due to a premature detonation that in fact
reduced the peak pressure of the metal jet.
[0040] These experiments again confirmed that the perforation
performance is heavily dependent upon the shape of the propellant
cap.
EXAMPLE 3
[0041] The enhancement cap described in this disclosure has been
used on a total of 240,000 charges in over 2,000 vertical oil wells
by China Yanchang Petroleum. There was no explosion accident or
other safety issues. The average yield of crude oil for those wells
was increased by 28.04% by using the enhancement cap.
[0042] FIG. 7 shows oil output of six wells from same production
field in a period of 34 months from 2009 to 2012. Three among the
six wells were perforated using shaped charges with an enhancement
cap, whose outputs are traced in solid lines. The other three were
perforated with shaped charges only, whose outputs are traced in
dash lines. Otherwise, these wells were located in the same block,
same formation, and operated under the same conditions.
[0043] Total oil output from test wells using the enhancement cap
was 4364.16 T while those did not employ enhancement wells have a
total output of 1318.51 T for the test period.
[0044] It is to be understood that the exemplary embodiments
described herein are that for presently preferred embodiments and
are not limiting. Descriptions of features or aspects within each
embodiment should typically be considered as available for other
similar features or aspects in other embodiments.
* * * * *