U.S. patent application number 14/708817 was filed with the patent office on 2015-10-29 for method and apparatus for catching darts and other dropped objects.
The applicant listed for this patent is BLACKHAWK SPECIALTY TOOLS, LLC. Invention is credited to BRAD GROESBECK, J. CHRISTOPHER JORDAN.
Application Number | 20150308213 14/708817 |
Document ID | / |
Family ID | 48171223 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150308213 |
Kind Code |
A1 |
JORDAN; J. CHRISTOPHER ; et
al. |
October 29, 2015 |
METHOD AND APPARATUS FOR CATCHING DARTS AND OTHER DROPPED
OBJECTS
Abstract
A dart or other dropped object having a rigid nose is dropped or
launched down hole, typically during cementing operations, until it
lands on a resilient seat within a dart catcher receptacle. By
increasing a pressure differential across the landed dart to a
predetermined amount, the dart extrudes through the seat and passes
into a ported catcher sub. The seat member can be constructed of
engineered composite material that does not yield in response to
passage of the dart and returns to its original size following such
passage.
Inventors: |
JORDAN; J. CHRISTOPHER;
(HOUSTON, TX) ; GROESBECK; BRAD; (HOUSTON,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BLACKHAWK SPECIALTY TOOLS, LLC |
HOUSTON |
TX |
US |
|
|
Family ID: |
48171223 |
Appl. No.: |
14/708817 |
Filed: |
May 11, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13665422 |
Oct 31, 2012 |
|
|
|
14708817 |
|
|
|
|
Current U.S.
Class: |
166/377 ;
166/193 |
Current CPC
Class: |
E21B 33/12 20130101;
E21B 33/16 20130101 |
International
Class: |
E21B 33/12 20060101
E21B033/12 |
Claims
1. A dart catcher apparatus comprising: a) a dart having a rigid
nose defining an outer diameter; and b) a housing having a central
through bore, wherein a portion of said through bore has a reduced
internal diameter defining a seat having an inner diameter smaller
than said outer diameter of said nose, and wherein said seat
comprises resilient material adapted to expand to allow passage of
said rigid dart nose in response to a predetermined axial force
acting on said dart.
2. The dart catcher assembly of claim 1, wherein said seat is at
least partially constructed of composite material.
3. The dart catcher assembly of claim 1, wherein said seat does not
permanently yield during passage of said dart.
4. The dart catcher assembly of claim 1, wherein said seat returns
to substantially its original size following passage of said
dart.
5. The dart catcher assembly of claim 1, further comprising a
receptacle disposed below said seat adapted to receive a dart
passing through said seat.
6. The dart catcher assembly of claim 5, wherein said receptacle
comprises a substantially cylindrical housing defining an inner
chamber and at least one flow port extending from said inner
chamber through said housing.
7. The dart catcher assembly of claim 6, wherein said at least one
flow port comprises an elongate aperture.
8. A method for catching dropped objects in a well comprising: a)
introducing a dart having a rigid nose defining an outer diameter
into said well; b) receiving said dart on a seat in a dart catcher
assembly, wherein said dart catcher assembly comprises a housing
having a central through bore defining said seat, and wherein said
seat has an inner diameter smaller than said outer diameter of said
dart nose and is at least partially constructed of resilient
material adapted to deform to allow passage of said rigid dart nose
in response to a predetermined axial force; c) applying axial force
to said dart; and d) passing said dart through said seat.
9. The method of claim 8, wherein said seat returns to
substantially its original size following passage of said dart.
10. The method of claim 9, wherein said seat does not permanently
yield in response to passage of said dart.
11. The method of claim 9, wherein said dart catcher apparatus
further comprises a receptacle disposed below said seat adapted to
receive a dart passing through said seat.
12. The method of claim 11, wherein said receptacle comprises a
substantially cylindrical housing defining an inner chamber and at
least one flow port extending from said inner chamber through said
housing.
13. The method of claim 12, wherein said at least one flow port
comprises an elongate aperture.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/665,422, filed Oct. 31, 2012, currently
pending, which claims priority of U.S. Provisional Patent
Application Ser. No. 61/554,255, filed Nov. 1, 2011, all
incorporated herein by reference.
STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLY
SPONSORED RESEARCH AND DEVELOPMENT
[0002] None
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention pertains to a method and apparatus for
performing cementing operations in oil and/or gas wells. More
particularly, the present invention pertains to a method and
apparatus for catching darts or other objects dropped or launched
during such well cementing operations.
[0005] 2. Brief Description of the Prior Art
[0006] Conventional rotary drilling rigs typically comprise a
supportive rig floor, a substantially vertical derrick extending
above said rig floor, and a traveling block, top drive unit or
other hoisting mechanism that can be raised and lowered within said
derrick. During drilling or servicing operations, such rig
equipment is often used to manipulate tubular goods, such as drill
pipe or drill collars, in and out of a well bore that extends into
the earth's crust. Once a well has been drilled to a desired depth,
large diameter pipe called casing is frequently installed in such
well and, thereafter, cemented in place. The casing is typically
installed to provide structural integrity to a well bore, and to
keep geologic formations isolated from each other.
[0007] During casing installation operations, casing is typically
inserted into a well in a number of separate sections of
substantially equal length. As the bottom or distal end of the pipe
string penetrates further into a well, additional sections of pipe
are added to the ever-lengthening pipe string at the rig. After a
sufficient length of casing has been installed into a bore hole,
cement is typically pumped down the internal bore of said casing
(or a smaller diameter workstring disposed within the casing), out
the bottom of the casing, and up the annular space existing between
the outer surface of the casing and the inner surface of the bore
hole. When the cement hardens, a cement sheath is formed around the
outer surface of the casing, anchoring the casing in place and
isolating down-hole formations penetrated by said well from being
in fluid communication with one another.
[0008] During cementing operations, darts, balls, plugs and/or
other objects, typically constructed of rubber, plastic or other
material, are frequently pumped into a well in connection with such
cementing operations. In many instances, such items are suspended
within a cementing head or other similar device at or near the
surface until the objects are released or "launched" at desired
points during the cement pumping process. Once released, such items
join cement slurry flow and can be pumped down hole directly into a
well. Typically, such darts, balls, plugs and/or other objects
should be beneficially held in place within the slurry flow passing
through a cement head prior to being launched or released without
being damaged or washed away by such slurry flow.
[0009] Dart catchers, which are well known in the art, are devices
that can be used to enhance cementing performance and subsequent
drill-out operations. In most cases, at least one dart catcher is
run downhole (frequently near the bottom of a casing string) via an
inner workstring during installation of a casing string. While
cement is being pumped into the inner bore of said workstring, a
wiping dart or other droppable object can be launched and pumped
downhole with the cement slurry until it "lands" within such a dart
catcher.
[0010] After such wiping dart or other droppable object lands
within said dart catcher, fluid flow through said dart catcher is
restricted, resulting in an increase in pump pressure observable at
the surface. Such pressure response provides a surface indication
of the precise location of a cement wiping dart or other droppable
object which, in turn, provides important fluid/cement displacement
volume information regarding the cementing operation being
performed.
[0011] After a wiping dart or other droppable object has been
seated within a downhole dart catcher, many conventional dart
catchers can then be shifted to a fluid by-pass position or
otherwise opened to permit fluid flow through said dart catcher
apparatus. Following such shifting or opening, pumping can resume
and cement displacement operations can be completed. Typically,
such wiping darts or other droppable objects will remain seated
within in a dart catcher assembly, and can be retrieved upon
removal of the workstring from the well.
[0012] Although such conventional dart catchers have a number of
important benefits, existing dart catcher technology has certain
important operational limitations. By way of example, such
limitations relate to the methods of seating of wiping darts or
other dropped objects, pressure indications related to the landing
process, as well as flow capacity through such dart catchers after
a dart has been landed. Thus, there is a need for an improved
method and apparatus for catching darts or other dropped objects,
particularly in connection with well cementing operations.
SUMMARY OF THE INVENTION
[0013] The present invention comprises a dart or other dropped
object having a shearable nose member, as well as a dart catcher
receptacle for receiving/landing said dart. For ease of reference,
the droppable object is referred to herein primarily as a "dart" or
wiper dart. However, it is to be understood that such terminology
is not intended to be, nor should it be construed as, limiting in
any manner. Accordingly, the droppable or launchable objects
described herein are not limited to darts or other similar objects,
and may include other droppable objects having different
configurations.
[0014] The dart catcher receptacle of the present invention has an
inner bore with a beneficial inner profile having a dart catching
seat, described in more detail below that permits fluid flow
through said catcher receptacle. Said dart catcher receptacle is
positioned at a desired location downhole, typically prior to
commencement of cementing operations. Thereafter, a dart of the
present invention is launched or dropped and is pumped
downhole.
[0015] Said dart proceeds downhole until it lands on the seat of
the dart catcher receptacle. After said dart is landed within said
dart catcher receptacle, the dart restricts fluid flow through the
inner bore of said dart catcher receptacle. As fluid (typically
cement slurry) is pumped down hole, a pressure indication, usually
in the form of increased pump pressure, can be observed at the
surface.
[0016] As cement slurry or other fluid is pumped into the well from
the surface, a pressure differential is created across said dart.
As said pressure differential increases to a predetermined amount,
at least one sleeve on the outer diameter ("OD") of the nose of
said dart shears (giving a pressure indication at the surface) from
said dart; the dart passes through said sleeve, but the sleeve
remains within the inner bore of the dart catcher receptacle. In
the preferred embodiment, shear screws or pins join said
sleeve-like nose member to said dart, and shear at a predetermined
differential pressure. Further, in the preferred embodiment, the
shape of the nose sleeve is such that it leaves a smooth transition
for the nose on a subsequently-launched dart to land and shear. The
process can be repeated multiple times.
[0017] In the preferred embodiment, the wiper dart receptacle of
the present invention has a restricted inner diameter to prevent
darts from passing through said receptacle without the shearable
nose member seating within said through-bore. However, the diameter
of said through-bore is sufficiently large to permit passage of
darts therethrough following shearing of the nose member; in most
case, such darts pass through said through-bore and rest within a
ported housing situated below the dart catcher receptacle.
[0018] The shearable sleeve nose member of the dart of the present
invention includes an inner profile designed to ensure that wiper
fins from darts are not cut or left behind by passing through the
nose sleeve as they extrude into the catcher tube. Generally, the
core or stem of a dart must be small enough to fit through the
seat, yet strong enough not to break during use.
[0019] An alternative embodiment of the present invention comprises
a dart catcher receptacle having a collet seat. Typically, collet
seats are designed with collet finger seams oriented radially
outward to permit said collet fingers to spread or expand outward
when not restricted by an outer ring or other member. Such
conventional collet seats can be problematic when pumping dart fins
through spread collet fingers as dart fins can extrude through gaps
formed between the collet fingers, resulting in said dart fins
becoming stuck in said gaps or tearing away from the dart body.
[0020] In the preferred embodiment of the present invention, the
collet fingers of the present invention are cut at an angle--that
is, not radially outward from the central bore of the collet seat.
As the collet fingers of the present invention spread or expand
outward, said fingers push against each other but do not create
gaps that can catch or tear dart fins.
[0021] As with other embodiments of the present invention, this
embodiment of the present invention comprises a downhole dart
catcher receptacle to catch drill pipe wiper darts. When such a
dart is seated within said collet seat of the dart catcher
receptacle, flow is restricted through said dart catcher
receptacle. As a result, fluid (primarily pump) pressure from above
creates a pressure differential across the seated dart, resulting
in a pump pressure increase observable at the surface when each
dart lands in the tool. The modular design of the collet and mating
darts allows multiple darts to be utilized with a single tool.
[0022] Collet fingers of the present invention can beneficially
flex, but always overlap one another to prevent any gaps between
said fingers. The darts of the present invention have body sections
small enough to fit through the expanded collet seat, yet strong
enough not to break or bend during use. Dart passage pressure
through said collet seat can be modified by adding/removing c-rings
to the outer diameter of the collet seat, or by machining the
collet fingers to have desired material characteristics.
[0023] In a second alternative embodiment of the present invention,
portions of the downhole dart catcher receptacle are constructed of
a resilient engineered composite material that is able to expand to
pass a rigid dart nose, but subsequently contract back to its
original size without permanently yielding. In this manner,
multiple darts can pass through the inner bore of said downhole
dart catcher receptacle with substantially the same pressure/force
requirements.
[0024] In all embodiments, the dart catcher receptacle of the
present invention provides sufficient clearance to allow a minimum
equivalent flow diameter substantially the same as drill pipe
(i.e., no flow restriction) and allow both forward and reverse flow
through said tool. A catcher tube has enough bypass ports to allow
minimum equivalent flow diameter as drill pipe (i.e., no flow
restrictions) per foot and allow both forward and reverse flow
through the tool. Flow slots are positioned such that reverse flow
is possible even if a dart is pushed back up and covers the inlet
to said catcher tube.
[0025] Dimensions described herein are for illustration only and
are not to be construed as limiting in any manner. Further, as used
herein, multiple references are made to darts. However, it is to be
understood that the present invention is not limited solely to
darts, and the present invention can beneficially function with
other dropped objects including, without limitation, other
configurations of wipers and the like.
BRIEF DESCRIPTION OF DRAWINGS/FIGURES
[0026] The foregoing summary, as well as any detailed description
of the preferred embodiments, is better understood when read in
conjunction with the drawings and figures contained herein. For the
purpose of illustrating the invention, the drawings and figures
show certain preferred embodiments. It is understood, however, that
the invention is not limited to the specific methods and devices
disclosed in such drawings or figures.
[0027] FIG. 1 depicts a perspective view of a first embodiment of a
wiper dart equipped with the shearable sleeve member of the present
invention.
[0028] FIG. 2 depicts a side sectional view of a dart catcher
assembly of the present invention with a dart received within the
inner seat profile of said dart catcher assembly.
[0029] FIG. 3 depicts a side sectional view of a dart catcher
assembly of the present invention after a dart has passed through
the inner seat profile of said dart catcher assembly.
[0030] FIG. 4 depicts a side sectional view of a dart catcher
assembly of the present invention after multiple darts have passed
through the inner seat profile of said dart catcher assembly.
[0031] FIG. 5 depicts a side sectional view of the detail area
highlighted in FIG. 3.
[0032] FIG. 6 depicts a side sectional view of the detail area
highlighted in FIG. 4.
[0033] FIG. 7 depicts a perspective view of a collet seat member of
an alternative embodiment of the dart catcher of the present
invention.
[0034] FIG. 8 depicts a bottom view of a collet seat member of an
alternative embodiment of the dart catcher of the present
invention.
[0035] FIG. 9 depicts a bottom view of a conventional prior art
collet seat.
[0036] FIG. 10 depicts a side sectional view of a second
alternative embodiment dart catcher assembly of the present
invention.
[0037] FIG. 11 depicts a side sectional view of the detail area
highlighted in FIG. 10.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0038] FIG. 1 depicts a perspective view of a first embodiment of a
wiper dart 100 equipped with the shearable sleeve 110 of the
present invention. As depicted in FIG. 1, wiper dart 100 embodies a
typical configuration of a conventional wiper dart, in that it
comprises substantially cylindrical central stem member 101, as
well as fin members 102 that extend radially outward from said
central stem member 101. Said fin members 102 are flexible and can
beneficially partially collapse or fold; in certain applications,
said fin members 102 can be used to contact and wipe internal pipe
surfaces, while being capable of passing through restrictions that
may be encountered in such pipe.
[0039] Still referring to FIG. 1, wiper dart 100 comprises dart
nose 104. Although the specific design of said nose 104 can vary,
in the dart embodiment depicted in FIG. 1, said nose 104 includes
tapered surface 103. Shearable sleeve 110 having tapered shoulder
surface 111 is disposed on said nose 104. Said shearable sleeve 110
is secured to nose 104 using radial shear screws 120; it is to be
observed that alternative shear devices such as, for example, shear
rings or pins, can be used in place of said shear screws 120.
[0040] It is to be observed that the present invention is described
with specific reference to wiper dart 100. However, it is to be
understood that such reference is not intended to be, nor should it
be construed as, limiting in any manner. Accordingly, the scope of
the present invention extends to any number of different droppable
or launchable objects, and is not limited merely to darts or other
similar objects. Further, it is also to be observed that shearable
sleeve 110 could be positioned at other locations on wiper dart
100, particularly if said wiper dart has a different shape or
configuration.
[0041] FIG. 2 depicts a side sectional view of dart catcher
assembly 10 of the present invention with wiper dart 100 received
within an inner bore of said dart catcher assembly 10.
Specifically, dart catcher assembly 10 of the present invention
comprises axially connected receptacle assembly 20, housing
assembly 30 and connection member 40.
[0042] Dart catcher receptacle assembly 20 comprises outer housing
21 having axial central through bore 22 and upper threaded
connection member 23. Upper threaded connection 23 is adapted to
connect to drill pipe, tubular workstring or other similar
equipment. Seat member 24 has sleeve 25, which is disposed within
said central through bore 22 of outer housing 21. Central through
bore 26 extends through seat member 24 and defines an inner
surface. It is to be observed that, when no obstruction (such as,
for example, wiper dart 100) is present in through bore 26, fluid
can flow through said dart catcher receptacle assembly 20.
[0043] Ported catch housing assembly 30 is connected to the bottom
of dart catcher receptacle assembly 20. Said ported catch housing
assembly 30 comprises substantially cylindrical body member 35
having axial central through bore 31 extending there through and
defining a chamber within said body member. At least one port 32
extends through the side of cylindrical body member 35. Bowl-like
seat 33 is disposed at or near the base of said ported catch
housing assembly 30. Connection member 40 is connected below said
ported sub 30 and has substantially cylindrical body section 43 and
central through bore 45 extending there through, as well as upper
connection member 41 and lower connection member 42.
[0044] In the preferred embodiment, dart catcher assembly 10 is
connected to a tubular workstring and positioned at a desired
location down hole, typically prior to commencement of cementing
operations. Fluid (including, without limitation, cement slurry
and/or displacement fluid) can be pumped down said tubular
workstring. When desired, wiper dart 100 can be launched or dropped
within said tubular workstring and is pumped down hole with cement
slurry or displacement fluid. Said wiper dart 100 proceeds through
such tubular workstring until it enters said dart catcher assembly
10 and lands within said dart catcher assembly 10 as depicted in
FIG. 1 and as described in detail herein. After said wiper dart 100
is landed within said dart catcher assembly 10, dart 100 restricts
fluid flow through bore 26 of seat member 24 (and said dart catcher
assembly 10).
[0045] As cement slurry or other fluid is pumped into the well
through said tubular workstring, a pressure differential is created
across said dart 100. As the pressure above said dart 100 increases
and said differential reaches a predetermined amount, axial forces
acting on dart 100 cause shear screws 120 to shear, thereby
releasing sleeve 110 from nose assembly 104 of dart 100. Downward
pressure acting on dart 100 forces said dart 100 through said
shearable sleeve 110.
[0046] FIG. 3 depicts a side sectional view of a dart catcher
assembly 10 of the present invention after dart 100 has passed
through shearable sleeve 110. As depicted in FIG. 3, said shearable
sleeve 110 remains seated within through bore 26 of seat member 24.
Dart 100 passes through said shearable sleeve 110, proceeds into
ported catch housing assembly 30 and rests on seat 33. In most
cases, the passage of dart 100 through the inner bore of shearable
sleeve 110 and into catch housing assembly 30 results in a pressure
indication observable at the surface (typically in the form of pump
pressure reduction); after the obstruction caused by dart 100 is
removed from seat member 24, a fluid restriction is removed and
fluid can flow through said dart catcher assembly 10. Further, in
the preferred embodiment, the shape of shearable sleeve 110 is
beneficially designed to receive the nose of a
subsequently-launched wiper dart, allowing such subsequent dart to
land within said shearable sleeve 110.
[0047] FIG. 5 depicts a side sectional view of the detail area
highlighted in FIG. 3. Shearable sleeve 110 has lower tapered
shoulder 111 that rests on tapered landing shoulder 27 defined by
the inner surface of through bore 26 of seat member 24. Because
tapered landing shoulder 27 defines a smaller internal diameter
than the largest outer diameter of shearable sleeve 110, said
shearable sleeve 110 seats on, and cannot pass beyond, said landing
shoulder 27. As discussed above, when pressure above a landed wiper
dart (not shown) increases, shear screws 120 shear, allowing
shearable sleeve 110 to release from dart 100. Downward pressure
acting on dart 100 forces said dart through an inner bore of
shearable sleeve 110 and into ported catch housing assembly 30
below; however, shearable sleeve 110 remains behind within through
bore 26 of seat member 24.
[0048] FIG. 4 depicts a side sectional view of a dart catcher
assembly 10 of the present invention after multiple wiper darts
have passed through said dart catcher assembly 10 of the present
invention. As depicted in FIG. 4, a first wiper dart can be dropped
or launched and subsequently landed within dart catcher assembly
10. As downward fluid pressure is applied in accordance with the
process described above, downward pressure acting on dart 100
forces said dart 100 through shearable sleeve 110 and into ported
catch housing assembly 30 below, with shearable sleeve 110
remaining within through bore 26 of seat member 24.
[0049] Thereafter, a second wiper dart 150 can be dropped or
launched and subsequently landed within shearable sleeve 110, which
is itself landed within dart catcher assembly 10. As downward fluid
pressure is applied in accordance with the process described above,
downward pressure acting on dart 150 causes shearable sleeve 130 to
separate from dart 150. Downward forces acting on said dart 150
force said dart 150 through stacked shearable sleeves 130 and 110,
and into ported catch housing assembly 30. Shearable sleeve 130
remains seated within previously landed shearable sleeve 110; both
stacked sleeves remain within through bore 26 of seat member
24.
[0050] FIG. 6 depicts a side sectional view of the detail area
highlighted in FIG. 4. Shearable sleeve 130 has lower tapered
shoulder 131 that rests within a central bore of shearable sleeve
110. Because the central bore of shearable sleeve 110 defines a
smaller internal diameter than the largest outer diameter of
shearable sleeve 130, said shearable sleeve 130 cannot pass beyond
shearable sleeve 110, which in turn, cannot pass beyond landing
shoulder 27 of seat member 24.
[0051] As discussed above, when pressure above a landed wiper dart
(not shown) increases, shearable sleeve 130 is released from such
dart. Downward pressure acting on such dart forces the dart through
axially stacked shearable sleeves 130 and 110 and into ported catch
housing assembly 30. The process can be repeated multiple times,
with shearable sleeves, positioned in a stacked configuration, to
accommodate multiple darts. The shearable sleeves of the present
invention include inner profiles designed to ensure that wiper fins
from darts are not cut or left behind when passing through said
sleeves as darts/fins extrude into a ported catch housing assembly
below.
[0052] A first alternative embodiment comprises a dart catcher
receptacle assembly (such as dart catcher receptacle assembly 20
depicted in FIG. 20) having a collet seat member disposed within
seat member 24. FIG. 7 depicts a perspective view of a collet seat
member 200 of said first alternative embodiment of the dart catcher
of the present invention. Said collet seat member 200 is mounted
within such a dart catcher receptacle assembly so that the nose or
leading tip of a dropped or launched dart will land within central
bore 201 of said collet seat member. After such a wiper dart is
landed within bore 201 of said collet seat member 200, said dart
restricts fluid flow through said bore 201 of said dart catcher
assembly.
[0053] As cement slurry or other fluid is pumped into the well
through said tubular workstring, a pressure differential is created
across said landed dart. As the pressure above said dart increases
and said pressure differential reaches a predetermined amount,
axial forces acting on dart cause collet fingers 202 of collet seat
member 200 to expand or spread radially outward. Downward pressure
acting on said dart forces said collet fingers 202 to continue to
spread radially outward until said previously seated dart passes
through central bore 201 of collet member 200.
[0054] FIG. 9 depicts a bottom view of a collet seat member 250
having conventional prior art collet fingers 252. Conventional
collet fingers 252 are typically designed with collet finger seams
253 oriented radially outward to permit said collet fingers 252 to
expand outward when not restricted by an outer ring or other
member. However, the design of such conventional collet fingers 252
can be problematic when pumping dart fins through said collet
fingers 252, as said dart fins can extrude through the gaps formed
between the collet fingers, resulting in said dart fins becoming
stuck in said gaps or tearing away from a dart body.
[0055] FIG. 8 depicts a bottom view of a collet member 200 of the
present invention. As depicted in FIG. 8, seams 203 formed between
collet fingers 202 of the present invention are oriented at an
acute angle--that is, not radially outward from the central bore
201 of collet seat member 200. Said collet fingers 202 are still
capable of expanding radially outward to permit passage of a wiper
dart under application of predetermined forces; however, said
collet fingers 202 ride against each other and do not create gaps
or spaces along said seams 203 that could catch or tear dart fins.
Put another way, collet fingers 202 of the present invention can
beneficially flex and spread, but always overlap one another to
prevent any gaps between said fingers.
[0056] When a wiper dart is seated within inner bore 201 of collet
seat member 200 of the present invention, fluid flow is restricted
through said bore 201. As a result, fluid (primarily pump) pressure
from above said seated dart creates a pressure differential across
the seated dart, resulting in a pump pressure increase observable
at the surface when a dart lands in collet seat member 200.
Moreover, the design of the alternative embodiment of the present
invention utilizing collet seat member 200 allows multiple darts to
be utilized with a single tool. Dart passage pressure can be
modified by adding/removing c-rings to the outer diameter of the
collet member 200 (such as in recessed section 204), or by
machining or forming collet fingers 202 from material having
desired physical properties or characteristics.
[0057] FIG. 10 depicts a side sectional view of a second
alternative embodiment dart catcher receptacle of the present
invention, while FIG. 11 depicts a side sectional view of the
detail area highlighted in FIG. 10. In said second alternative
embodiment of the present invention, seat 300 is mounted within
downhole dart catcher receptacle assembly; in the preferred
embodiment, said seat 300 is mounted within inner bore 26 of seat
member 24. Said seat member 300 is constructed of an expanding
engineered composite material that is able to expand to pass a
rigid dart, but contract back to its original size without
permanently yielding. In this manner, multiple darts can pass
through the inner bore of said downhole dart catcher receptacle
with substantially the same pressure/force requirement.
[0058] The body of the dart catcher receptacle of the present
invention provides enough clearance to allow a minimum equivalent
flow diameter as drill pipe or other tubular workstring (i.e., no
flow restriction) and allow both forward and reverse flow through
the tool. Catch housing assembly 30 has enough bypass ports 32 to
allow minimum equivalent flow diameter as drill pipe (i.e., no flow
restrictions) per foot and allow both forward and reverse flow
through dart catcher assembly 10. Flow ports 32 can be elongate
(slots) and positioned such that reverse flow is possible even if a
dart within catch housing assembly 30 is pushed back upward and
blocks the inlet to said catch housing assembly.
[0059] As used herein, multiple references are made to darts.
However, it is to be understood that the present invention is not
limited solely to darts, and the present invention can beneficially
function with other dropped objects including, without limitation,
other configurations of wipers and the like.
[0060] The above-described invention has a number of particular
features that should preferably be employed in combination,
although each is useful separately without departure from the scope
of the invention. While the preferred embodiment of the present
invention is shown and described herein, it will be understood that
the invention may be embodied otherwise than herein specifically
illustrated or described, and that certain changes in form and
arrangement of parts and the specific manner of practicing the
invention may be made within the underlying idea or principles of
the invention.
* * * * *