U.S. patent application number 13/585390 was filed with the patent office on 2014-02-20 for hydraulic jar with low reset force.
This patent application is currently assigned to THRU TUBING SOLUTIONS, INC.. The applicant listed for this patent is Roger L. Schultz, Brock W. Watson. Invention is credited to Roger L. Schultz, Brock W. Watson.
Application Number | 20140048247 13/585390 |
Document ID | / |
Family ID | 48986258 |
Filed Date | 2014-02-20 |
United States Patent
Application |
20140048247 |
Kind Code |
A1 |
Watson; Brock W. ; et
al. |
February 20, 2014 |
HYDRAULIC JAR WITH LOW RESET FORCE
Abstract
A hydraulic jar for delivering impacts downhole. The jarring
mechanism includes a cup-type piston that moves through a seal
bore. The cup is deformable in response to fluid pressure so that
it expands each time it moves through the seal bore to compensate
for wear on the lip. Since only minimum interference is required
between the piston and seal bore, less material may be used. This
reduces the force required to reset the tool, which is particularly
advantageous in horizontal wells. The seal bore may be slightly
wider at the exit; the cup expands to this exit diameter, ensuring
an interference fit as the cup travels back through the smaller
diameter entry section. The entry end of the seal bore may include
longitudinal grooves. This prevents the piston cup from rupturing
by preventing a fluid seal around the lip until the most of cup is
inside the seal bore.
Inventors: |
Watson; Brock W.; (Oklahoma
City, OK) ; Schultz; Roger L.; (Ninnekah,
OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Watson; Brock W.
Schultz; Roger L. |
Oklahoma City
Ninnekah |
OK
OK |
US
US |
|
|
Assignee: |
THRU TUBING SOLUTIONS, INC.
Oklahoma City
OK
|
Family ID: |
48986258 |
Appl. No.: |
13/585390 |
Filed: |
August 14, 2012 |
Current U.S.
Class: |
166/72 |
Current CPC
Class: |
E21B 31/1135 20130101;
E21B 17/20 20130101; E21B 19/22 20130101 |
Class at
Publication: |
166/72 |
International
Class: |
E21B 23/04 20060101
E21B023/04 |
Claims
1. A hydraulic jarring tool for use with a well conduit in an oil
or gas well, the tool comprising: a housing; a mandrel; wherein one
of the mandrel and the housing is attachable to the well conduit
and the other of the mandrel and the housing is attachable to a
fixed object in the well; wherein the housing and the mandrel have
telescopically engaged portions that are axially movable relative
to each other to fire and reset the tool; wherein the
telescopically engaged portions of the housing and the mandrel are
configured to form a hydraulic chamber therebetween, the hydraulic
chamber including a low pressure chamber, a high pressure chamber,
and a narrow diameter seal bore therebetween; wherein the seal bore
has a smaller diameter section and a larger diameter section
between the smaller diameter section and the high pressure chamber;
wherein the low pressure chamber includes an inwardly tapering
bevel that contacts the seal bore, and the high pressure chamber
includes an inwardly tapering bevel that contacts the seal bore; an
impact surface formed on each of the housing and the mandrel; a
piston supported in the hydraulic chamber for relative movement
between the high and low pressure chambers through the seal bore,
wherein the piston comprises a cup with an open end terminating in
a lip, the open end of the cup facing the high pressure chamber,
the cup being deformable in response to fluid pressure, so that as
the piston moves through the seal bore towards the high pressure
chamber, the lip of the cup expands permanently to a diameter
larger than the smaller diameter section of the seal bore; an
unrestricted flow path configured to allow hydraulic fluid to pass
through the seal bore as the piston moves through the seal bore
towards the low pressure chamber to reset the tool; and a
restricted flow path configured to restrict the flow of hydraulic
fluid as the piston moves through the seal bore towards the high
pressure chamber to fire the tool and create a jarring impact
between the impact surfaces.
2. The hydraulic jarring tool of claim 1 wherein the larger
diameter section of the seal bore comprises a tapered section, the
larger diameter end of the tapered section being continuous with
the high pressure chamber.
3. The hydraulic jarring tool of claim 2 wherein the smaller
diameter section of the seal bore comprises a straight section
extending between the smaller diameter end of the tapered section
and the low pressure chamber.
4. The hydraulic jarring tool of claim 1 wherein the cup of the
piston is formed of a metal.
5. The hydraulic jarring tool of claim 4 wherein the cup is formed
of a copper alloy.
6. The hydraulic jarring tool of claim 5 wherein the seal bore is
formed of alloy steel.
7. The hydraulic jarring tool of claim 1 wherein the piston
comprises a piston base from which the cup extends, wherein the
piston is part of a piston assembly that also includes a timing
washer and a sleeve, wherein the sleeve has a cup end and a base
end, wherein the sleeve is arranged coaxially inside the piston,
wherein the timing washer has an annular piston face opposing the
end of the piston base and the base end of the sleeve, wherein the
piston is supported for slight axially movement relative to the
piston face of the timing washer to create a space therebetween as
the piston moves through the seal bore towards the low pressure
chamber, and wherein the unrestricted flow path is formed in part
by the space formed between the end of the piston base and the
piston face of the timing washer, and wherein when the end of the
piston base is urged against the piston face of the timing washer,
the unrestricted flow path is closed and fluid is forced through
the restricted flow path.
8. The hydraulic jarring tool of claim 7 wherein the base end of
the piston sleeve and the piston face of the timing washer are
configured to provide a flow channel therebetween, wherein the
timing washer includes a restricted passageway continuous with the
flow channel between the piston face of the timing washer and the
base end of the piston sleeve, wherein the restricted passageway is
configured to allow the hydraulic fluid therethrough when the end
of the piston base is urged against the piston face of the timing
washer as the piston moves through the seal bore towards the high
pressure chamber, and wherein the restricted flow path is formed in
part by the flow channel between the base end of the piston sleeve
and the restricted passageway in the timing washer.
9. The hydraulic jarring tool of claim 8 wherein the restricted
passageway in the timing washer is a spiral groove.
10. The hydraulic jarring tool of claim 1 wherein the seal bore
comprises longitudinal grooves at the end of the seal bore that
adjoins the low pressure chamber configured to prevent a fluid seal
between the piston cup and the wall of the seal bore until a
substantial portion of the piston cup is inside the seal bore.
11. A bottom hole assembly comprising the jarring tool of claim
1.
12. A tubing string comprising the bottom hole assembly of claim
11.
13. A coiled tubing system comprising the tubing string of claim
12.
14. A bidirectional hydraulic jarring tool for use with a well
conduit in an oil or gas well, the tool comprising: a housing; a
mandrel; wherein one of the mandrel and the housing is attachable
to the well conduit and the other of the mandrel and the housing is
attachable to a fixed object in the well; wherein the housing and
the mandrel have telescopically engaged portions that are axially
movable relative to each other to fire and reset the tool; wherein
the telescopically engaged portions of the housing and the mandrel
are configured to form a sealed annular hydraulic chamber
therebetween, the sealed annular hydraulic chamber including an
upper chamber, a lower chamber, and a seal bore therebetween;
wherein the seal bore has an upper larger diameter section at the
upper end, a lower larger diameter section at the lower end, and a
smaller diameter section between the upper and lower larger
diameter sections; wherein the upper chamber includes an inwardly
tapering bevel that contacts the seal bore, and the lower chamber
includes an inwardly tapering bevel that contacts the seal bore; an
impact surface formed on each of the housing and the mandrel; a
pair of piston assemblies supported in the sealed annular hydraulic
chamber, the pair of piston assemblies comprising an upper piston
assembly and a lower piston assembly; wherein the upper piston
assembly is supported in the sealed annular hydraulic chamber for
relative movement between the upper and lower chambers through the
seal bore, and wherein the upper piston assembly comprises a cup
with an open end terminating in a lip, the open end of the cup
facing the lower chamber, the cup being deformable in response
fluid pressure, so that as the piston upper piston assembly moves
through the lower larger diameter section of the seal bore towards
the lower chamber, the lip of the cup expands permanently to a
diameter larger than the smaller diameter section of the seal bore;
wherein the lower piston assembly is supported in the sealed
annular hydraulic chamber for relative movement between the upper
and lower chambers through the seal bore, and wherein the lower
piston assembly comprises a cup with an open end terminating in a
lip, the open end of the cup facing the upper chamber, the cup
being deformable in response fluid pressure, so that as the lower
piston assembly moves through the upper larger diameter section of
the seal bore towards the upper chamber, the lip of the cup expands
to a diameter larger than the smaller diameter section of the seal
bore; an unrestricted flow path in the upper piston assembly
configured to allow hydraulic fluid to pass through the seal bore
as the upper piston assembly moves through the seal bore towards
the upper pressure chamber; an unrestricted flow path in the lower
piston assembly configured to allow hydraulic fluid to pass through
the seal bore as the lower piston assembly moves through the seal
bore towards the lower chamber; a restricted flow path in the upper
piston assembly to restrict the flow of hydraulic fluid as the
upper piston assembly moves through the seal bore towards the lower
chamber to fire the tool and create a upward impact between the
impact surfaces; a restricted flow path in the lower piston
assembly to restrict the flow of hydraulic fluid as the lower
piston assembly moves through the seal bore towards the upper
chamber to fire the tool and create a downward impact between the
impact surfaces.
15. The hydraulic jarring tool of claim 14 wherein the seal bore
comprises a center straight section forming the smaller diameter
section, wherein the upper larger diameter section is a tapered
section with the large end continuous with the upper chamber, and
wherein the lower larger diameter section is a tapered section with
the large end continuous with the lower chamber.
16. The hydraulic jarring tool of claim 14 wherein the cup of each
of the upper and lower piston assemblies is formed of a metal.
17. The hydraulic jarring tool of claim 16 wherein the cup of each
of the upper and lower assemblies is formed of a copper alloy.
18. The hydraulic jarring tool of claim 17 wherein the seal bore is
formed of alloy steel.
19. A bottom hole assembly comprising the jarring tool of claim
14.
20. A tubing string comprising the bottom hole assembly of claim
19.
21. A coiled tubing system comprising the tubing string of claim
20.
22. (canceled)
23. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to downhole tools
and methods and, more particularly, but without limitation, to
tools and methods used to deliver jarring impacts to objects
downhole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] FIG. 1 is a schematic illustration of a typical coiled
tubing system deploying a tool string comprising the jarring tool
of the present invention.
[0003] FIG. 2 is a longitudinal sectional view of a hydraulic
jarring tool constructed in accordance with a first embodiment of
the present invention. The jar is shown in the set or cocked
position.
[0004] FIG. 3 is a longitudinal sectional view of the jar shown in
FIG. 2 with showing the jar in the fired or discharged
position.
[0005] FIGS. 4A-C are enlarged sequential sectional views of the
tool of FIG. 2 showing the jar in the set or cocked position.
[0006] FIGS. 5A-5C are enlarged sequential sectional views of the
tool of FIG. 3 showing the jar in the fired or discharged
position
[0007] FIG. 6 is a further enlarged sectional view of the hydraulic
jarring assembly of the tool of FIG. 2. The piston is in the set or
cocked position in the upper chamber.
[0008] FIG. 7 is a further enlarged sectional view of the hydraulic
jarring assembly of the tool of FIG. 3. The piston is in the fired
or discharged position in the lower chamber.
[0009] FIG. 8 is an enlarged sectional view of the mandrel showing
the piston assembly in the position it assumes as it moves through
the seal bore towards the lower chamber to initiate a jarring
impact.
[0010] FIG. 9 is an enlarged sectional view of the mandrel showing
the piston assembly in the position it assumes as it moves through
the seal bore towards the upper chamber to reset the tool.
[0011] FIG. 10 is an end view of the cup end of the jar piston
sleeve.
[0012] FIG. 11 is a sectional view taken along line 11-11 of FIG.
10 through the jar piston sleeve.
[0013] FIG. 12 is a perspective view of the base end of the jar
piston sleeve.
[0014] FIG. 13 is an elevational view of the base end of the jar
piston.
[0015] FIG. 14 is a side elevational view of the jar piston.
[0016] FIG. 15 is a perspective view of the base end of the jar
piston.
[0017] FIG. 16 is a sectional view taken along line 16-16 of FIG.
13.
[0018] FIG. 17 is an elevational view of the piston face of the
timing washer.
[0019] FIG. 18 is an elevational view of the timing face of the
timing washer.
[0020] FIG. 19 is a sectional view taken along line 19-19 of FIG.
17.
[0021] FIG. 20 is a perspective view of the timing face of the
timing washer.
[0022] FIG. 21 is an enlarged fragmented section view of the upper
housing showing the seal bore detail.
[0023] FIG. 22 is a fragmented sectional view of the jarring
assembly portion of a tool constructed in accordance with a third
preferred embodiment of the invention. The jarring assembly of this
jar includes two piston assemblies to provide bidirectional
jarring. This figure shows the jar assembly in the set or cocked
position for a down jar and the fired or discharged position of an
up jar.
[0024] FIG. 23 is a fragmented section view of the jarring assembly
of FIG. 22 with the jar pistons in the neutral position with the
piston coupling positioned midway in the seal bore.
[0025] FIG. 24 is a fragmented sectional view of the jarring
assembly of FIG. 22. The jarring assembly is shown in the set or
cocked position for an up jar and the fired or discharged position
of a down jar.
[0026] FIG. 25 is an enlarged fragmented section view of the upper
housing of the tool shown in FIG. 22 showing the seal bore
detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0027] Jarring tools are used to jar or shake loose a downhole tool
or object that has become stuck or lodged in the well bore. In
hydraulic or reciprocating type jars, a metering or timing section
inside telescopically arranged inner and outer tubular members
resists allowing the jar to extend, which provides sufficient time
for the tubing string to be stretched before a hydraulic release
mechanism within the jar allows rapid extension and impact within
the tool. This creates a large dynamic load on the stuck tool or
object. Most hydraulic jars are designed for repetitive or cyclic
action to continue jarring the stuck object until it is dislodged.
The cyclic firing and resetting or recocking of the jar is
accomplished by pushing and pulling the tubing string.
[0028] Hydraulic jars are often run on coiled tubing. However,
there are several disadvantages to using coiled tubing to run a
hydraulic jar. Because of the increased frictional forces at work
in a horizontal well bore, it is particularly difficult to push or
"snub" coiled tubing into a horizontal well, making it difficult to
cycle the jar.
[0029] The jarring tool of the present invention offers an
improvement in methods and tools for jarring operations using
coiled tubing. In accordance with the present invention, the piston
of the jarring assembly comprises a cup that is expandable in
response to fluid pressure. For example, the jarring piston may be
formed of a copper alloy. Alternately, the piston may be formed of
an alloy steel. The component forming the hydraulic chamber,
including the seal bore, may be formed of simple steel of normal
steel hardness, such as AISI 4140.
[0030] The seal bore preferably has two sections, a smaller
diameter section at the entry and a larger diameter section at the
outlet end. In the most preferred embodiment, the seal bore is
tapered. The cup is designed to have a small interference fit with
the narrow diameter end of the tapered section. The tapered section
has a diameter selected to allow the piston cup to expand to the
point that is becomes permanently enlarged to the larger diameter
end of the tapered section. In this way, when the pressure is
released, the cup's enlarged diameter will be enough to maintain
the minimum required interference with the straight section of the
seal bore on the next cycle. This compensates for any wear or
erosion on the lip from the previous cycle.
[0031] Because the expansion of the cup as it exits the seal bore
reduces the effects of wear on the cup lip from the previous cycle,
the enlarged piston cup will maintain the minimum interference in
the straight section of the seal bore in the next cycle. Thus, wear
on the piston lip is compensated for by repeated expanding its
diameter, thus removing the need to use harder, more wear-resistant
material to make the cup and seal bore. This provides a relatively
thin piston cup which can be pushed through the seal bore using
less force, making it easier to reset the jar in every cycle.
[0032] Although the jarring tool and method of this invention is
particularly useful with coiled tubing, those skilled in the art
will appreciate that it can be employed with other tubular well
conduits, such as jointed well tubing and drill pipe. Additionally,
although this jarring tool is particularly advantageous for up
jars, in which the jarring action requires snubbing the coiled
tubing, down jars and bidirectional jars will be benefited by
employing this inventive jarring assembly.
[0033] Turning now to the drawings in general to and to FIG. 1 in
particular, there is shown therein a coiled tubing deployed jarring
system. The exemplary system or "rig," designated generally by the
reference number 10, includes surface equipment. The surface
equipment includes a reel assembly 12 for dispensing the coiled
tubing 14. An arched guide or "gooseneck" 16 guides the tubing 14
into an injector assembly 18 supported over the wellhead 20 by a
crane 22. The crane 22 as well as a power pack 24 may be supported
on a trailer 26 or other suitable platform, such as a skid or the
like. A control cabin, as well as other components not shown in
FIG. 1, may also be included.
[0034] A fishing tool 28 on the end of the tubing 14 in the
wellbore 30 is used to attach a jar 32 to the stuck object 34. The
combination of tools connected at the downhole end of the tubing 14
forms a tool string or bottom hole assembly ("BHA") 36. The bottom
hole assembly 36 and tubing 14 combined are referred to herein as
the tubing string 38. The bottom hole assembly 36 may comprise a
variety of tools including but not limited to a bit, a mud motor,
hydraulic disconnect, jarring tools, back pressure valves, and
connector tools.
[0035] Fluid is introduced into the coiled tubing 14 through a
system of pipes and couplings in the reel assembly, designated
herein only schematically at 40. In accordance with conventional
techniques, the jar 32 is cycled by raising and lowering the
section of tubing in the injector assembly 18 repeatedly until the
object 34 is dislodged.
[0036] In some instances, the jar 32 is connectable directly to the
stuck object 34 in the wellbore 30. In other instances, the jar 32
is connected as one member of a bottom hole assembly comprising
several tools. When the jar 32 is described as being connectable to
a "stationary object downhole," it is intended to mean that the
tool is connectable directly to the object or indirectly to the
object through another tool in the tool string, which may have
become lodged in the wellbore, or to the fishing tool 28 that is in
turn attached to the stuck object 34 in the well.
[0037] The coiled tubing injection system 10 illustrated in FIG. 1
is exemplary. It is not intended to be limiting. There are several
types of tubing injection systems presently available, and the
present invention may be used with equal success in any of these
systems. Moreover, as indicated previously, other types of well
conduits may be employed instead of coiled tubing.
[0038] Turning now to FIGS. 2 and 3, the jarring tool 32, made in
accordance with a first preferred embodiment of the present
invention, will be described in detail. FIG. 2 shows the jar 32 in
the cocked or set position, and FIG. 3 shows the jar in the fired
or discharged position. The jar 32 comprises two telescopically
engaged tubular assemblies, including an inner tubular assembly or
mandrel 102 and an outer tubular assembly or housing 104. The
housing 104 and the mandrel 102 have telescopically engaged
portions that are axially movable relative to each other to fire
and reset the jarring tool 32.
[0039] Either the mandrel 102 or the housing 104 is attachable to
the well conduit 14, and the other is attachable to the fixed
object 34 in the wellbore 30. In the particular embodiment shown,
the downhole end 106 of the mandrel 102 is attachable to the stuck
or stationary object 34, and the uphole end 108 of the housing 104
is attached to the tubing 14. In this way, the housing 104 is moved
up or down relative to the mandrel 102. However, it will be
appreciated that this arrangement may be reversed, that is, the
housing may be attachable to the downhole object (or other tool)
and the mandrel attachable to the well conduit.
[0040] As used herein, the terms "up," "upward," "upper," and
"uphole" and similar terms refer only generally to the end of the
drill string nearest the surface. Similarly, "down," "downward,"
"lower," and "downhole" refer only generally to the end of the
drill string furthest from the well head. These terms are not
limited to strictly vertical dimensions. Indeed, many applications
for the tool of the present invention include non-vertical well
applications.
[0041] Throughout this specification, the mandrel 102 and housing
104 as well as the jarring assembly components are described as
moving "relative" to one another. This is intended to mean that
either component may be stationary while the other is moved.
Similarly, where a component is referred to as moving "relatively"
downwardly or upwardly, it includes that component moving
downwardly as well as the other, cooperative component moving
upwardly.
[0042] In the preferred embodiment, the housing 104 comprises a top
sub 110 which is provided with a internally threaded end or box
joint forming the upper end 108 for attachment to the coiled tubing
14 or to another tool in the tool string 36. An upper housing 112
is connected to the downhole end of the top sub 110, and a lower
housing 114 is connected to the downhole end of the upper housing.
A wiper seal sub 116 connects to the downhole end of the lower
housing 114, and a collar or split sub 118 connects to the downhole
end of the wiper seal sub, forming the lower end of the housing
104. While this is a preferred assembly for the housing, the
components of the housing may vary in number and configuration.
[0043] Referring still to FIG. 4A-4C and FIGS. 5A-5C, the mandrel
102 preferably comprises a lower mandrel 120 with an externally
threaded downhole end forming the lower end 106 of the tool. A
center mandrel 122 is connected to the uphole end of the lower
mandrel 120, and an upper mandrel 124 is connected to the uphole
end of the center mandrel.
[0044] The preferred tool 32 includes a jarring assembly designated
generally at 130. The telescopically engaged portions of the
housing 104 and the mandrel 102 are configured to form a hydraulic
jarring chamber 132 therebetween. The hydraulic chamber 132
includes an upper or low pressure chamber 134, a lower high
pressure chamber 136, and a narrow diameter seal bore 138
therebetween. It will be understood that in a down jar version of
this tool, the lower chamber will be the high pressure chamber and
the upper chamber will be the low pressure chamber.
[0045] The jarring impact is created when an impact surface on the
housing 104, such as the hammer surface 140 impacts an impact
surface on the mandrel 102, such as the anvil surface 142. When the
tool is reset or cocked, an impact surface 144 on the housing 104
abuts an impact surface 146 on the mandrel 102, to limit the travel
of the housing when being reset. The shape and location of these
impact surfaces may vary.
[0046] A piston assembly 150 is supported on the upper mandrel 124
for movement inside the hydraulic jarring chamber 132. As shown in
FIG. 6, in the cocked or set position, the piston assembly 150 is
positioned in the upper or low pressure chamber 134. As the housing
104 is pulled up, the piston assembly 150 is squeezed through the
seal bore 138 and into the lower or high pressure chamber 134, as
shown in FIG. 7. As explained in more detail below, the jarring
impact results from a sudden pressure drop when the piston assembly
150 exits the seal bore 138.
[0047] Turning now to FIGS. 8 and 9, the structure and operation of
the piston assembly 150 will be explained. The preferred piston
assembly 150 comprises a piston sleeve 152 supported on the outer
diameter of the upper mandrel 124. The piston sleeve 152, shown in
more detail in FIGS. 10-12, comprises a sleeve body 154 with a
first or base end 156 and a flanged second or cup end 158. The base
end 156 is provided with radial grooves 160, and a flange 162
extends from the second end 158. The flange 162 has notches
164.
[0048] A cup-type piston 170 is slidably supported coaxially around
the piston sleeve 152. The piston 170, shown in detail in FIGS.
13-16, has a base end 172, which preferably is curved or otherwise
profiled so as to be nonplanar for a reason which will become
apparent. A cup 174 extends from the base 172 and terminates in a
lip 176. The inner diameter of the base 172 of the piston 170 is
slightly larger than the outer diameter of the sleeve 152 to
provide a flow channel 178 therebetween.
[0049] The piston assembly 150 further comprises a timing washer
180, shown in detail in FIGS. 17-20. The timing washer 180 has an
annular piston face 182 on one end and a metering face 184 on the
other end. The inner diameter 186 of the timing washer 180 has a
lengthwise groove 188 that is continuous with a spiral bleed
channel 190 formed on the metering face 184. The edge 192 between
the inner diameter 186 and the piston face 182 is beveled.
[0050] As best seen in FIGS. 8 and 9, the timing washer 180 is
supported on the upper mandrel 124 so that the piston face 182
opposes and is adjacent to the base end 172 of the piston 170 and
the grooved base end 156 of the piston sleeve 152. The metering
face 184 of the timing washer 180 abuts the annular face 196 of a
collar 198, which is captured on an annular shoulder 200 formed
near the lower end of the upper mandrel 124.
[0051] One or more springs 204 are supported between the flanged
end 162 of the piston sleeve 152 and uppermost end 206 of the
center mandrel 122. These springs are included to accommodate
slight variances in tolerances resulting from manufacturing. Thus,
the springs should be strong enough to resist any movement in the
piston sleeve 152 during operation of the tool.
[0052] As the housing 104 is pulled up on the mandrel 102 (towards
the left in FIG. 8), and the piston assembly 150 is squeezed
downwardly relative to the seal bore 138 (FIG. 6) with the open end
of the piston cup 174 leading. The fluid pressure causes the piston
lip 176 to seal against the seal bore 138, and the base 172 of the
piston 170 is urged into engagement with the piston face 182 of the
timing washer 180. This forces the hydraulic fluid along a
restricted flow path indicated by the arrows in FIG. 8. More
specifically, the fluid enters the piston cup 174 and passes
through the flow channel 178 between the inner diameter of the
piston base 172 and the outer diameter of the sleeve body 154. The
fluid then flows through the flow channel formed by the grooves 160
on the grooved end 156 of the piston sleeve, through the lengthwise
groove 188 on the inner diameter 186 of the timing washer 180, and
then enters the spiral bleed channel 190 on the metering face
184.
[0053] When the fluid reaches the end of the spiral channel 190 it
exits the piston assembly 150 around the outer diameter of the
timing washer 180 and flows up into the upper or low pressure
chamber 134 (FIG. 6). This restricted flow path creates pressure
that is suddenly released when the piston assembly 150 exits the
seal bore 138, generating the sudden jarring impact.
[0054] The piston assembly 150 also provides an unrestricted flow
path for passage of the hydraulic fluid through the piston assembly
when it passes through the seal bore 138 (FIG. 7) is the opposite
direction to reset the tool. This unrestricted flow path is
illustrated in FIG. 9. As the housing 104 is pushed down on the
mandrel 102 (towards the right in FIG. 9) to reset the tool, the
piston 170 is urged toward the springs 204 creating a space 202
between the base end 172 of the piston and the piston face 182 of
the timing washer 180. This allows the hydraulic fluid to pass from
the flow channel 178 between the piston 170 and sleeve 152 out into
seal bore through the space 202, bypassing the flow channel formed
by the grooves 160 in the end of the sleeve and the spiral bleed
channel 190.
[0055] While a preferred timing or metering mechanism has been
shown and described herein, it will be appreciated that the present
invention is not so limited. Other metering structures, such as
annular flow channels, orifices, tortuous paths of different
configuration, may be employed.
[0056] Directing attention now to FIG. 21, the preferred
configuration for the seal bore 138 will be explained. The seal
bore 138 is formed by a narrow or restricted diameter portion in
the upper housing 124. The seal bore 138 has an entrance end 210
and an exit end 212. These terms are intended to indicate the
direction of the piston assembly 150 as it is passes through the
seal bore 138 during a jarring stroke, where the open cup end of
the piston 170 is the leading end of the assembly.
[0057] In the preferred seal bore 138, the bore comprises a smaller
diameter section and a larger diameter section. Most preferably,
these different diameter sections take the form of a straight
section at the entrance end 210 of the bore 138 and a tapered
section extending from the straight section to the exit end 212 of
the bore. The straight section, designated by the arrow 218, is
relatively short compared to the tapered section, designated by the
arrow 220. While this straight section is advantageous for
manufacturing and assembly, it is not essential to the function of
the seal bore.
[0058] The straight section 218 has a constant diameter along its
length designated as "d.sub.1." The tapered section 220 gradually
increases in diameter from the dimension d.sub.1 to a slightly
larger diameter at the exit end designated as "d.sub.2." By way of
example only, if the piston 170 is made from 110 KSI copper allow
and is about 0.060 inch thick, and if the straight section is 2.25
inches in diameter (d.sub.1) and 0.63 in length, the tapered
section 220 may gradually increase in diameter to 2.272 inches in
diameter (d.sub.1) at the exit end 212 having a length of 2.75
inches, that is, a taper of 0.004 per inch.
[0059] The purpose of the tapered section with its slightly
increasing diameter is to allow the diameter of the piston cup 174
to permanently expand slightly in response to fluid pressure. As
indicated, the piston 170 is designed to permanently expand
slightly in response to fluid pressure. More particularly, the
piston is designed to permanently expand at a pressure that is
lower the operating pressure of the hydraulic fluid. By way of
example, the piston may be formed of a metal allow, such as a
copper allow, that is slightly resilient so that the fluid pressure
will expand the cup to the largest diameter of the seal bore. While
the metallic cup may not retain the fully expanded diameter,
neither will it resume its smallest original diameter; instead, the
cup will maintain a slightly enlarged diameter that is larger than
the smaller diameter section of the seal bore. Thus, the present
invention includes the use of resilient and non-resilient cup
materials that are capable of some permanent expansion.
[0060] The tapered section 220 is selected to achieve the desired
permanent reformed diameter of the piston cup, which is a function
of the diameter of the straight section 218 of the seal bore 138.
This is because the purpose of the expansion is to maintain a lip
diameter that will provide a minimum interference fit in the
straight section of the bore. Thus, the exit diameter is calculated
according to the following formula:
d exit = d small ( 1 + .sigma. y_piston E piston ) ##EQU00001##
[0061] With continuing reference to FIG. 21, another desirable
feature of the seal bore 138 will be described. As indicated, in
the preferred practice of this invention, the piston 170 is
deformable in response to the pressure of the hydraulic fluid. If
the burst pressure of the piston cup 174 is low enough, there is a
danger that the cup may rupture as it enters the seal bore 138.
[0062] Rupture of the cup 174 may be prevented by providing bypass
recesses at the entrance end 210 to allow the hydraulic fluid to
flow around the lip of the cup until the a substantial portion of
the cup is inside the bore. For example, in the preferred
embodiment, a plurality of longitudinal grooves 230 is provided
around the entrance 210 to the bore 138 and extending a distance
into the straight section 218. As the piston 170 moves into the
seal bore 138 and the lip engages the wall of the bore, fluid can
still pass through the grooves 230 around the lip. This prevents
the full pressure of the operating fluid from acting on the cup
until the cup is substantially inside the bore. How far into the
seal bore the cup needs to advance to prevent rupture will vary
with the pressure and the cup material. Thus, as used herein,
"substantially" means that the cup has advanced far enough into the
seal bore so that rupture of the cup is prevented.
[0063] Having described the structure of the tool 32, its use and
operation now will be explained. Referring again to FIG. 1, the
tubing string 38 is run downhole and latched onto the stuck object
34 preferably using the fishing tool 28. The tubing string 14 is
slacked off to ensure that the jar 32 is in the fully telescoped or
cocked position, as shown in FIGS. 2 & 4A-4C. In this position,
the piston assembly 150 is in the upper or low pressure chamber
134, as shown in FIG. 6. To initiate a jarring stroke, the operator
pulls upwardly on the tubing string 14 at the surface thereby
exerting an upward pull on the attached jar housing 104, that is,
the housing is pulled to the left in FIGS. 6 and 7. As the mandrel
102 is fixed to the stuck object, this pulling action causes the
piston assembly 150 to move downwardly through the seal bore
138.
[0064] As the piston assembly 150 moves through the seal bore 138,
fluid pressure below the piston assembly increases rapidly until
the piston assembly enters the lower or high pressure chamber 136.
At this point, there is a sudden release of the pressure, causing
the housing to complete its travel to the fully extended or fired
position (FIG. 7) and resulting in a jarring impact when the hammer
surface 140 on the housing 104 impacts the anvil surface 142 of the
mandrel 102.
[0065] To reset the tool 32, the tubing string 14 is snubbed
downwardly, which forces the housing 104 to move downwardly on the
mandrel 102, that is, to the right as seen in FIGS. 6 and 7. This
causes the piston assembly 150 to move upwardly (to the left in
FIG. 7) through the seal bore 138. Frictional drag on the piston
170 separates it from the timing washer 180 opening the space 202
(FIG. 9), thereby allowing the hydraulic fluid to pass through the
unrestricted flow path (FIG. 9). When the impact surface 144 on the
housing 104 abuts the impact surface 146 on the mandrel 102, the
tool 32 is reset and ready for another jarring stroke. This process
is repeated as often as necessary until the stuck object is
dislodged.
[0066] Now it will be appreciated that as the piston cup 174 moves
up and down through the seal bore 138 repeatedly, the lip 176 will
be worn away. However, due to the expandable nature of the cup 174
and the increasing diameter of the seal bore 138, the cup is also
repeatedly being plastically expanded to compensate for this
wear.
[0067] Turning now to FIGS. 22-24, another preferred embodiment of
the jarring tool of the present invention will be described. In
this embodiment, designated generally at 300, the tool is
constructed similarly to the tool 32 of the previously described
embodiment having a mandrel 302 telescopically received inside a
housing 304. FIGS. 22-24 show only the section of the tool with the
jarring assembly. The rest of the tool may be similar to that shown
in the previous embodiment.
[0068] This embodiment includes a bidirectional jarring assembly
designated generally at 330. The bidirectional jarring assembly
includes a pair of piston assemblies 350A and 350B positioned in a
hydraulic chamber 332. The hydraulic chamber 332 includes an upper
chamber 334, a lower chamber 336, and a narrow diameter seal bore
338 therebetween. The seal bore 338 of this embodiment is adapted
for two-way operation, as explained more fully below. The upper and
lower hydraulic chambers 334 and 336 function alternately as high
and low pressure chambers, depending on the jar direction.
[0069] Each of the piston assemblies 350A and 350B is similar to
the piston assembly 150 of the jar 32 (FIGS. 2-21). The two piston
assemblies 350A and 350B are oppositely oriented to each other in
the tool. The piston assembly 350A is arranged similarly to the
piston assembly 150 for producing an upward jar, while the piston
assembly 350B is oppositely disposed to create a downward jar. The
upper mandrel 324 comprises an upper section 324a and a lower
section 324b joined by a mandrel coupling 325. The piston assembly
350A is captured on the upper section 324a of the upper mandrel 324
between the shoulder 352 and the upper end of the coupling 325, and
the piston assembly 350B is captured between the lower end of the
coupling and the shoulder 354 on the lower section 324b of the
upper mandrel.
[0070] The seal bore 338 will now be described with reference to
FIG. 25. The seal bore 338 comprises an up jar section 360 and a
down jar section 362 and a center section 364 in between. The upper
end 366 serves as the entry end for the upper piston assembly 350A,
and the lower end 368 serves as the entry end for the lower piston
350B. The upper and lower ends 366 and 368 both are provided with
grooves 370 and 372, respectively, for the purpose previously
described. The up jar section 360 has a tapered diameter gradually
increasing from the diameter d.sub.1 to the slightly larger
diameter d.sub.2. The down jar section 362 has a tapered diameter
gradually increasing from the diameter d.sub.1 to the slightly
larger diameter d.sub.2. The center section 364 is straight or
cylindrical.
[0071] Now it will be apparent that the up jar piston assembly 350A
will function similarly to the previously described embodiment. The
piston assembly 350A will produce an up jar when it passes
downwardly through the up seal bore 338 from the position shown in
FIG. 24, through the mid-stroke position shown in FIG. 23, and then
to the down stroke or discharged position shown in FIG. 22, in same
manner as the piston assembly 150 of the up jar 32 previously
described. Now it will be apparent that the discharge position of
the up jar action is the set or cocked position for a subsequent
down jar. A down jar is produced when the down jar piston assembly
350B passes upwardly through the seal bore 338 from the position
shown in FIG. 22, through the mid-stroke position shown in FIG. 23,
and then to the upstroke or discharged position shown in FIG. 22.
In this way, the jar 300 can produce alternating bidirectional
jarring forces.
[0072] Referring still to FIG. 25, the plastic expansion of the cup
pistons in the piston assemblies occurs in a similar fashion. The
piston cup of the jar assembly 350A creates a seal with the seal
bore as the cup enters the end 366. The cup expands as it moves
through the tapered section 360 (to the right in FIG. 25) during an
up jar, as previously described. The enlarged cup maintains the
seal as it passes through the reversely tapered section 362 and
exits the seal bore 338 to create an up jar.
[0073] The piston cup of the jar assembly 350B creates a seal with
the seal bore as the cup enters the end 368. The cup expands as it
moves through the tapered section 362 (to the left in FIG. 25)
during a down jar, as previously described. The enlarged cup
maintains the seal as it passes through the reversely tapered
section 360 and exits the seal bore 338 to create a down jar.
[0074] Having described the structure of the tool 300, its use and
operation will now be explained. Referring again to FIGS. 22-24,
the tubing string 38 is run downhole and latched onto the stuck
object 34 preferably using the fishing tool 28. The tubing 14 is
slacked off to ensure that the jar 300 is in the fully telescoped
position, which means it is set or cocked for an up jar, as shown
in FIG. 24. In this position, the piston assemblies 350A and 350B
both are in the upper chamber 334.
[0075] To initiate an up jar stroke, the operator pulls upwardly on
the tubing string 14 at the surface thereby exerting an upward pull
on the attached jar housing 304. As the mandrel 302 is fixed to the
stuck object, this pulling action causes the piston assemblies 350A
and 350B to move downwardly through the seal bore 338 (to the right
in FIGS. 22-24).
[0076] As previously described, as the up jar piston assembly 350A
is forced downward (to the right) through the seal bore 338, fluid
is forced through its restricted flow path of the up jar to create
the sudden pressure release as it exits the seal bore. During the
same stroke, the down jar piston assembly 350B moves "backwards"
through the seal bore 338, allowing the fluid to pass through its
unrestricted flow path.
[0077] Next, to initial a reverse or down jar, the tubing 14 is
snubbed downwardly, which forces the housing 304 to move downwardly
on the mandrel 302 from the position shown in FIG. 22 to the
mid-stroke position shown in FIG. 23, that is to the left in FIGS.
22-24. As the down jar piston assembly 350B moves upwardly (to the
left) through the seal bore 338, fluid through the down jar piston
assembly is forced through its restricted flow path to create a
down jar impact when the down jar piston assembly exits the upper
end 366 of the seal bore 338. During this stroke, the up jar piston
assembly 350A is passive, that is, it is moving backwards and the
hydraulic fluid is flowing through its unrestricted flow path. A
downwardly directed impact is created as the down jar piston
assembly 350B enters the upper chamber 334.
[0078] This bidirectional embodiment can be operated to provide
repeated jars in either an up or down direction, or alternately may
be operated to provide jarring impacts in alternating directions.
To fire the jar repeatedly in one direction only, the jar assembly
is reset by returning the tool to the neutral or centered position
shown in FIG. 23, rather than to the fully extended or retracted
positions shown in FIGS. 22 and 24. From the neutral position, the
jar can be fired in either direction.
[0079] The embodiments shown and described above are exemplary.
Many details are often found in the art and, therefore, many such
details are neither shown nor described. It is not claimed that all
of the details, parts, elements, or steps described and shown were
invented herein. Even though numerous characteristics and
advantages of the present inventions have been described in the
drawings and accompanying text, the description is illustrative
only. Changes may be made in the details, especially in matters of
shape, size, and arrangement of the parts, within the principles of
the invention to the full extent indicated by the broad meaning of
the terms. The description and drawings of the specific embodiments
herein do not point out what an infringement of this patent would
be, but rather provide an example of how to use and make the
invention. Likewise, the abstract is neither intended to define the
invention, which is measured by the claims, nor is it intended to
be limiting as to the scope of the invention in any way. Rather,
the limits of the invention and the bounds of the patent protection
are measured by and defined in the following claims.
* * * * *