Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF THE INVENTION
This invention relates to improvements made in jar tools
used ~or well drilling.
BACKGROUND OF_ THE INVENTION
Jar tools are extensively used in the oil drilling industry
to dislodge drill bits, drill string sections, or other well
tools trapped in well bores. An example of such a jar tool is
disclosed in U,S. Patent 3,716,109 (Griffiths) entitled ROTARY
JAR and owned by the applicantO U.S. Patent 3,716,109
discloses a jar tool which has been in satisfactory use for a
number of years.
Problems have remained with the paten~ed appara~us,
however, which have resulted in improvements being made which
are the subject o this application.
U.S. Patent 3,716,109 discloses a jar tool having a spline
mandrell and an outer housing, t.he mandrell and the housing
being able to move longitudinally relative to each other. A
knocker is connected to ~he mandrell and it collides with an
anvil which is connected to the housing. The collision or
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impact between them causes the jar on the drill string and it
sh~uld be appreciated that the impact is violent and the
operating conditions under which the tool iS used are extreme~
This impact is created by the sudden release of entrapped
hydraulic fluid which is allowed to rush by a piston assembly
travelling from a relatively narrow diameter of a hydraulic
cylinder into a relatively larger diameter where the fluid flow
past the piston is largely unimpeded.
To actuate the piston assembly, a piston actuator is used.
This piston actuator includes resilient fingers extending from
the actuator and towards the piston. The fingers engage a
resilient part on the piston assembly when contact is made and
provide a "pulling" action on the piston assembly to return it
to its home position following the jar. The technique of using
these fingers and the necessary costs entailed in using them
and complementary parts on the piston assembly is expensive and
complicated.
Further, it was considered desirable to improve the
metering system~ The use of the metering system, required
fluids that, although having viscosity characteristics more
constant under different operating temperatures, did not have
desirable lubricating qualities. The metering system could be
improved by selecting tempera~ure compensable valves within the
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metering system and pressure relief valves. The metering and
pressure relief ~alves may be used in various combinations to
achieve desirable operating characteristics.
The use of a metering system which allows for the changes
in fluid viscosity and density as the temperatures within the
drill hole vary, allows for the use of more desirable fluids
from a lubriction view point.
SUMMARY OF THE INVENTION
Accordingly, the invention disclosed and claimed is a jar
tool for use in a drill string, said jar tool comprising:
A jar tool for use in a drill string, said jar tool
comprising:
a mandrell adapted to be connected at one end to an
adjacent piece of drill pipe;
a housing surrounding the major portion of said mandrell
and defining therein a passageway for drilling fluid and an
annular chamber for hydraulic fluid, said annular chamber
having first, second and third sections, said first section
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being of relatively smaller diameter and located adjacent to
said second section and said third section being located
adjacent said first section;
coupling means between said mandrell and said housing, said
coupling means acting to transmit torque between said mandrell
and said housing and to allow longitudinal relative movement
between said housing and said mandrell between closed and open
positions~
respective pairs of abutment faces between said housing and
said mandrell to deEine said closed and open positions of said
tool;
a piston assembly mounted within said annular chamber and
around said mandrell, said assembly being adapted to move
longitudinally relative to said housing and mandrell between
said first section and said second section and acting ko seal
said third section from said first section, said third section
being located adjacen~ said first section on the end of said
piston assembly opposed from said second section, said first
section being adapted to closely receive said piston assembly;
shoulder means in said annular chamber between said first
and third sections defining a rest position for said piston
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assembly, said piston assembly further defining a metering
passageway for hydraulic ~luid;
piston actuation means mounted on said mandrell in said
third section and acting to actuate and move said piston
assembly from said first section to said second section as said
tool moves from said closed to open positions;
spring means within said housing acting on said piston
assembly to retain said assembly on said shoulder means
whereby, as said tool moves from said closed to said open
position, said piston actuation means moves said piston
assembly from said first section to said second section as said
fluid flows through said metering passageway wherein in said
second section, said fluid freely flows past said piston
allowing said abutment faces on said mandrell and housing to
collide and impart shock to said drill string; and wherein said
spring means acts to return said piston assembly to said
shoulder position when said tool moves from said open to said
closed position,
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described, by
way of example only, with reference to the accompanying
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drawings in which:
Figure 1 is a cross-sectional view of the jar tool in its
entirety;
Figure 2 iæ a cros -sectional view of the pis~on of the jar
tool in position just prior to the jar being initiated;
Figure 3 is a cross-section view of the piston of the jar
tool in a fully open position;
Figure 4 is an enlarged cross-sectional view of the area
IV-IV of Figure 1 showing the relief and metering valves in a
parallel configuration;
Figure 5 is an enlarged cross-sectional view of the area
IV-IV of Figure 1 showing the relief and pressure valves in a
combination parallel and series con~iguration;
Figure 6 is an enlarged cross-sectional view of the area
IV-IV of Figure 1 showing the relief and pressure valves in a
series configuration; and
Figure 7 is an enlarged cross-sectional view of the area
IV-IV of Figure 1 showing only a pressure relief valve
configuration.
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DESCRIP'rION OF A SPECIFIC EMBODIMENT
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Referring now to Figure 1, a jar tool is shown generally at
10. The jar tool 10 comprises a spline mandrell 11 and an
outer housing 12.
Spline mandrell 11 is made up of a threaded socket 13
adapted to receive an adjacent piece of drill pipe (not shown)
within the head portion 14 of the mandrell 11.
Hexagonal splines 15 extend longitudinally along mandrell
11 to threaded portion 16. A knocker 17 is connected through
complementary threads at 16. Impact ring 18 is mounted between
knscker 17 and shoulder 79 on spline mandrell 11. Knocker 17
has an opposed threaded end 19 and a piston mandrell 20 is
threadedly connected to knocker 17 by way of thr~aded
connection 19. Xnocker 17 also includes two O-rings 27, which
act as a seal between knocker 17, spline mandrell 11 and piston
mandrell 20.
Mounted on an opposed threaded connection 21 of piston
mandrell 20 is a washpipe 22 which extends longitudinally alon~
the axis of jar tool 10 and terminates at end 23.
A piston actuator 24 (see also Figure 2) is threadedly
connected to complementary threads 25 on washpipe 22. An
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O-ring 26 acts as a seal between piston mandrell 20 and
washpipe 22.
~ he outer housing 12 comprises several sections. A sealing
housing 29 extends from head portion 14 of spline mandrell 11
to a threaded onnection 30. The sealing housing 29 has
polypak 80 ac~ing as a seal between sealing housing 29 and head
portion 14 of spline mandrell 11. Sealing housing 29 also
includes bearing bushing 81 and cylinder fill plug 82 for
adding hydraulic fluid to the jar tool 10. A spline housing 31
has complementary threads at 30 and, additionally, further
threads 32 which are located at its opposed end. A knocker
housing 33 is mounted on threads 32 and extends longitudinally
from spline housing 31 to female threaded connection 34.
0-rings 83 act between spline housing 31, sealing housing 29
and knocker housing 33, respectively, A cylinder fill plug 35
acts as a port for adding hydraulic fluid to the jar tool 10 in
the upper chamber 55.
A packing sub 36 with complementary threaded connection 34
is connected to knocker housing 33 and it has an opposed
threaded connection 37 which allows complementary threads of
hydraulic cylinder 38 to be mounted thereon. Two O-rings 39
act as seals between the packing sub 36~ knocker housing 33 and
hydraulic cylinder 38, respectively.
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Packing sub 36 has an internally formed shoulder 41 and an
inner diameter which changes from a ~aximum area at 42 to a
minimum area 43. Packing sub 36 also includes a further
threaded connection 44.
Hydraulic cylinder 38 extends from the packing sub 36 to a
threaded connection 45 and includes two cylinder fill plugs 35
in its periphery. The inside of hydraulic cylinder 38 is
formed into three main diameters 46, 47 and 48 with a
transition portion 49 existing between diameters 46 and 47~ A
shoulder 50 is formed between diameters 47 and 48.
Washpipe housing 51 is connected to hydraulic cylinder 38
at threaded ~onnection 45 and extends longitudinally to
threaded connection 52. An O-ring ~3 acts as a seal between
hydraulic cylinder 38 and washpipe housing 51.
The various apparatus which are located between the several
sections of the outer housing 12 and spline mandrell 11,
respectively, will now be described.
A knocker gland 54 is mounted between the knocker 17 and
packing sub 36 in upper chamber 55. Knocker gland 54 contains
four polypak rings 56 which act as seals between the knocker
gland 54, knocker housing 33 and piston mandrell 20,
respectively.
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Seated against shoulder 57 o~ packing sub 36 is O-ring
gland 58. O~ring gland 58 includes four O~rings and back up
rings 59 which act between the packing sub 36 and piston
mandrell 20. A female junk ring 60 abuts O-ring gland 58 and
V-rings 61 are inserted between female junk ring 60 and male
junk ring 62. A packing spring 63 is inser~ed between male
junk ring 62 and upper gland nut 64. Upper gland nut 64 is
threadedly connected ~o packing sub 36 at threaded connection
44 and includes a wiper ring 65 acting between piston mandrell
20 and upper gland nut 64.
On shoulder 41 of packing sub 36 in the area 43 between the
packing sub 36 and piston mandrell 20, a second female junk
ring 85 is positioned together with V-rings 66 and male junk
ring 67. One end of piston return spring 68 abuts male junk
ring 67 and the other is in contact with piston assembly 69.
Piston assembly 69 abuts shoulder 50 in hydraulic cylinder
38 in its rest position and is shown more clearly in Figures 2
and 3. There is a close tolerance between the piston assembly
69 and the diameter of the piston mandrell 20 and hydraulic
cylinder 380 The piston assembly 69 includes a piston cup 70.
The metering valve 86 is removable from the piston assembly 69
and may be replaced with other suitable valves depending on the
operating conditions. Metering valves manufactured by the Lee
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Company, Arlington, Texas, are particularly appropriate for
this type of application.
A filter cage 71 (Figure 2) is also installed within the
piston assembly 69 to remove contaminants within the hydraulic
oil prior to passing through the metering and/or valve system
Piston return spring 68 retains piston assembly 69 against
shoulder 50 and also acts to retain the V-rings 66, male junk
ring 67 and female junk ring 85 (Figure 1) in the positions
depicted.
An O-ring gland 72 is inserted between washpipe housing 51
and washpipe 22. The O-ring gland 72 contains four O-rings and
back up rings 73 which act as seals between the O-ring gland
72, washpipe housing 51 and washpipe 22, respectively. A gland
nut 74 is connected to washpipe housing 51 at threaded
connection 75 and a retaining ring 76 retains the gland nut 74
in position.
Referring now to Figure 4, an enlarged view o~ the piston
assembly 69 i5 shown in which an alternative embodiment of the
invention is described. In this embodiment, the piston
assembly 69 is provided with a metering valve 86 as well as a
pressure relief valve 85 which is inserted in the piston
assembly 69 in a configuration parallel to that of the metering
valve 86.
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Referring now to Figure 5, an ~nlarged view o the piston
assembly 69 is shown in which a further embodiment of the
inven~ion is described. In this embodiment, the piston
assembly Ç9 is provided with a metering valve 86 and a pressure
relief valve 95 in serles on one side of the piston assembly 69
and with a pressure relief valve 95 only on the opposite side.
Referring now to Figure 6, an enlarged view of the piston
assembly 69 is shown in which a further embodiment of the
invention is described. In this embodiment, the piston
assembly 69 is provided with a pressure relief valve 95 and a
metering valve 86.
Referring now to Figure 7, an enlarged view of the piston
assembly 69 is shown in which yet a further embodiment of the
invention is described~ In this embodiment, the piston
assembly 69 is provided with a pressure relief valve 95 only.
OPERATION
In operation, when the driller wishes to operate the jar
tool, it will be assumed the tool is originally in the position
shown in Figure 1. The driller com~ences to apply a tension
which tends to lift the drill string in the direction indicated
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by ~he arrow and, in so doing, force will be applied between
the spline mandrell 11 and the outer housing 12. The head
portion 14 of the spline mandrell 11 therefore, will begin to
move away from sealing housing 29 at their abutting faces 87
such that cylindrical surface B5 is expose~. As spline
mandrell 11 moves relative to outer housing 12~ piston actuator
24 will also move leftwardly with piston mandrell 20. When
piston actuator 24 contacts piston assembly 69, piston assembly
69 will move away from shoulder 50 under the influence of the
piston actuator 24 as seen in Figure 2 since the counter-acting
force against piston assembly 69 by piston return spring 68 is
relatively much smaller than the force from the piston actuator
24. Hydraulic cylinder 38, however, contains hydraulic fluid
77 and the oil cannot pass from area 47 of hydraulic cylinder
38 to area 48 without passing through metering valve 86.
Accordingly, the relatively slow passage of hydraulic fluid 77
through metering valve 86 restricts the speed at which the
spline mandrell 11 and outer housing 12 can move relative to
each other until the piston assembly 69 reaches the position
shown in Figure 2. This builds up pressure within the area 46
which causes a large tensile force buildup between the two ends
of the tool lO.
When the piston assembly 69, including piston cup 70
however, passes into area 46 under the continued influence of
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piston actuator 24, hydraulic oil 77 is free to pass around the
piston assembly 69 and into areas 47 and 48 wi~h the result
that the spline mandrell ll and outer housing 12 increase their
movement relative to each other enormously. ThuS, impact ring
18 on knocker 17 collides violently with impact surface 78 of
spline housing 31 and this collision causes a jar or shock to
the drill string. The tool assumes the condi~ion depicted in
Figure 3.
The driller will ordinarily jar the ~ool several times to
free the stuck drill bit or well tool and, therefore, he will
now ordinarily lower the drill pipe. Piston assembly 69, under
the influence of piston return spring 68, will closely follow
piston actuator 24 until it returns to its rest position
against shoulder 50 of hydraulic cylinder 38. Thereafter, the
piston actuator may return to its rest position as depicted in
Figure l before a further jar is initiated by the driller.
There are many further modifications which can be made to
the specific embodiment of the invention just described which
changes, however, may still fall within the scope and spirit of
the invention.
