U.S. patent application number 13/829655 was filed with the patent office on 2014-04-17 for agitator sub.
The applicant listed for this patent is BBJ TOOLS INC.. Invention is credited to Bradley R. COTE.
Application Number | 20140102804 13/829655 |
Document ID | / |
Family ID | 50474380 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140102804 |
Kind Code |
A1 |
COTE; Bradley R. |
April 17, 2014 |
AGITATOR SUB
Abstract
A hydraulically driven agitator sub includes: a tubular body for
connection within a string including a first mandrel and a second
mandrel, and a central bore defining a longitudinal axis of the
tubular body and creating a flow path permitting a flow of fluids
between the two mandrels and through the tubular body, the second
mandrel secured, at least partially, within an annular bore of the
first mandrel so that the second mandrel is telescopically arranged
with and axially moveable within the first mandrel between a
telescopically extended position and a compressed position; and a
first sealing part and a second sealing part, one of the first and
the second sealing part being secured to the first mandrel and the
other sealing part being secured to the second mandrel, both
sealing parts being within the fluid flow path of the tubular body,
the first sealing part and the second sealing part being positioned
to come together when the first mandrel and the second mandrel are
in the compressed position to form a seal in the fluid path, the
seal substantially preventing the flow of fluids through the
tubular body
Inventors: |
COTE; Bradley R.; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BBJ TOOLS INC. |
Calgary |
|
CA |
|
|
Family ID: |
50474380 |
Appl. No.: |
13/829655 |
Filed: |
March 14, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61714040 |
Oct 15, 2012 |
|
|
|
61731308 |
Nov 29, 2012 |
|
|
|
Current U.S.
Class: |
175/171 ;
405/184 |
Current CPC
Class: |
E21B 17/076 20130101;
E21B 7/24 20130101 |
Class at
Publication: |
175/171 ;
405/184 |
International
Class: |
E21B 17/07 20060101
E21B017/07 |
Claims
1. An apparatus comprising: a tubular body for connection within a
string including a first mandrel and a second mandrel, and a
central bore defining a longitudinal axis of the tubular body and
creating a flow path permitting a flow of fluids between the two
mandrels and through the tubular body, the second mandrel secured,
at least partially, within an annular bore of the first mandrel so
that the second mandrel is telescopically arranged with and axially
moveable within the first mandrel between a telescopically extended
position and a compressed position; and a first sealing part and a
second sealing part, one of the first and the second sealing part
being secured to the first mandrel and the other sealing part being
secured to the second mandrel, both sealing parts being within the
fluid flow path of the tubular body, the first sealing part and the
second sealing part being positioned to come together when the
first mandrel and the second mandrel are in the compressed position
to form a seal in the fluid path, the seal substantially preventing
the flow of fluids through the tubular body.
2. The apparatus of claim 1 further comprising a biasing member
acting between the first mandrel and the second mandrel and biasing
the first mandrel and the second mandrel toward the compressed
position.
3. The apparatus of claim 1 further comprising a transmission
arrangement between the first mandrel and the second mandrel to
transmit torsional forces therebetween.
4. The apparatus of claim 1 further comprising a dampener to act
between the first mandrel and the second mandrel in the compressed
position to mitigate damaging contact between the first sealing
part and the second sealing part.
5. The apparatus of claim 1 wherein the first sealing part has an
aperture therethrough forming a portion of the fluid flow path and
the second sealing part includes a profile portion that seats in
and plugs the center aperture when the first sealing part and the
second sealing part come together to form a seal.
6. A drill string comprising: a string of tubulars; a drill bit
connected at a distal end of the string of tubulars; a drill
collar; and a hydraulically driven agitator positioned between the
drill bit and the drill collar.
7. The drill string of claim 6 wherein the hydraulically driven
agitator includes: a tubular body including a first mandrel
connected at an upper end directly or indirectly to the drill
collar and a second mandrel connected at a lower end directly or
indirectly to the drill bit, and a central bore defining a
longitudinal axis of the tubular body and creating a flow path
permitting a flow of fluids between the two mandrels and through
the tubular body, the second mandrel secured, at least partially,
within an annular bore of the first mandrel so that the second
mandrel is telescopically arranged with and axially moveable within
the first mandrel between a telescopically extended position and a
compressed position; and a first sealing part and a second sealing
part, one of the first and the second sealing part being secured to
the first mandrel and the other sealing part being secured to the
second mandrel, both sealing parts being within the fluid flow path
of the tubular body, the first sealing part and the second sealing
part being positioned to come together when the first mandrel and
the second mandrel are in the compressed position to form a seal in
the fluid path, the seal substantially preventing the flow of
fluids through the tubular body.
8. The drill string of claim 7 wherein the hydraulically driven
agitator further comprises a biasing member acting between the
first mandrel and the second mandrel and biasing the first mandrel
and the second mandrel toward the compressed position.
9. The drill string of claim 7 wherein the hydraulically driven
agitator further comprises a transmission arrangement between the
first mandrel and the second mandrel to transmit torsional forces
therebetween.
10. The drill string of claim 7 wherein the hydraulically driven
agitator further comprises a dampener to act between the first
mandrel and the second mandrel in the compressed position to
mitigate damaging contact between the first sealing part and the
second sealing part.
11. The drill string of claim 7 wherein the first sealing part has
an aperture therethrough forming a portion of the fluid flow path
and the second sealing part includes a profile portion that seats
in and plugs the center aperture when the first sealing part and
the second sealing part come together to form a seal.
12. A method for creating an agitation effect in a wellstring, the
method comprising: connecting an apparatus according to claim 1
in-line with a wellbore string to position the second mandrel and
the first mandrel in the compressed position when there is weight
on bit in the wellbore string; applying weight on bit to position
the first mandrel and the second mandrel in the fully compressed
position; pumping fluids through the wellbore string to develop a
fluid pressure overcoming the weight on bit holding the first
mandrel and the second mandrel in compressed position and driving
the first mandrel and the second mandrel apart; allowing the
pressure to dissipate such that the first mandrel and the second
mandrel return back to the compressed position; and continuing to
pump fluids through the wellbore string to create an agitation
effect as the first mandrel and the second mandrel continue to be
pumped apart and then returned to the compressed position.
13. The method of claim 12 further comprising applying torsional
forces through the wellbore string and transmitting the torsional
forces through the apparatus.
14. The method of claim 12 wherein driving the first mandrel and
the second mandrel apart includes lifting a drill collar upwardly
away from a drill bit.
Description
FIELD
[0001] The present invention relates to an apparatus and method for
creating an agitation effect in a string.
BACKGROUND
[0002] Agitators are employed to facilitate wellbore drilling and
installation of wellbore liners. Agitators create a regular
movement of the string that enhances advancement of the drill bit
and prevents slip stick in a well string such as a liner.
SUMMARY
[0003] In accordance with a broad aspect of the present invention
there is provided an apparatus comprising: a tubular body for
connection within a string including a first mandrel and a second
mandrel, and a central bore defining a longitudinal axis of the
tubular body and creating a flow path permitting a flow of fluids
between the two mandrels and through the tubular body, the second
mandrel secured, at least partially, within an annular bore of the
first mandrel so that the second mandrel is telescopically arranged
with and axially moveable within the first mandrel between a
telescopically extended position and a compressed position; and a
first sealing part and a second sealing part, one of the first and
the second sealing part being secured to the first mandrel and the
other sealing part being secured to the second mandrel, both
sealing parts being within the fluid flow path of the tubular body,
the first sealing part and the second sealing part being positioned
to come together when the first mandrel and the second mandrel are
in a fully compressed position to form a seal in the fluid flow
path, the seal preventing the flow of fluids through the tubular
body.
[0004] In accordance with another broad aspect of the present
invention there is provided a drill string comprising: a string of
tubulars; a drill bit connected at a distal end of the string of
tubulars; a drill collar; and a hydraulically driven agitator
positioned between the drill bit and the drill collar.
[0005] In accordance with another broad aspect of the present
invention there is provided a method for creating an agitation
effect in a wellstring, the method comprising: connecting an
apparatus as above in-line with a wellbore string to position the
second mandrel and the first mandrel in the compressed position
when there is weight on bit in the wellbore string; applying weight
on bit to position the first mandrel and the second mandrel in the
fully compressed position; pumping fluids through the wellbore
string to develop a fluid pressure overcoming the weight on bit
holding the first mandrel and the second mandrel in compressed
position and driving the first mandrel and the second mandrel
apart; allowing the pressure to dissipate such that the first
mandrel and the second mandrel return back to the compressed
position; and continuing to pump fluids through the wellbore string
to create an agitation effect as the first mandrel and the second
mandrel continue to be pumped apart and then returned to the
compressed position.
[0006] It is to be understood that other aspects of the present
invention will become readily apparent to those skilled in the art
from the following detailed description, wherein various
embodiments of the invention are shown and described by way of
illustration. As will be realized, the invention is capable for
other and different embodiments and its several details are capable
of modification in various other respects, all without departing
from the spirit and scope of the present invention. Accordingly the
drawings and detailed description are to be regarded as
illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Referring to the drawings, several aspects of the present
invention are illustrated by way of example, and not by way of
limitation, in detail in the Figures, wherein:
[0008] FIG. 1 is a schematic representation of a typical well bore
drilling scenario with one embodiment of the apparatus connected
in-line with a string.
[0009] FIG. 2A is a side elevation, sectional view of one
embodiment of the apparatus in an extended position.
[0010] FIG. 2B is a side elevation, sectional view of one
embodiment of the apparatus in a sealing position.
DESCRIPTION OF VARIOUS EMBODIMENTS
[0011] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
embodiments of the present invention and is not intended to
represent the only embodiments contemplated by the inventor. The
detailed description includes specific details for the purpose of
providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the
present invention may be practiced without these specific
details.
[0012] For the sake of clarity, within this description, the terms
"up", "uphole", "upper", "above" generally refer to the direction
within the wellbore towards the surface. Likewise, the terms
"down", "downhole", "lower", "below" make reference to the
direction within the wellbore away from surface. The terms "inner"
and "inward" refer to the direction towards the center of a
wellbore, whereas the terms "outer" and "outward" refer to the
direction away from the center of a wellbore, for example towards
the well bore wall. As those skilled in the art of well bore
drilling can appreciate these terms are similarly relevant to
deviated and directionally drilled well bores and the tools used
therein.
[0013] The apparatus is an agitator that can be employed to agitate
a wellbore string. The string can be a drill string, as shown, or
another string that requires agitator, such as a liner string. As
such, while the following description implies a drilling
application, the method and apparatus are equally useful for liner
placement applications and any other application in which a
wellbore string requires agitation.
[0014] A typical drilling rig 10 is shown on the surface 12 with a
well bore 14 being drilled through subterranean formations 16
towards a target reservoir 18, as shown in FIG. 1. Within the
wellbore, a string 20 is depicted including a drill bit 22 and a
tubular body 24 is shown incorporated with the string. Drilling rig
10 or a downhole motor (not shown) or any other method known in the
art may provide the torsional force on the drill bit. The string
may include any number and variety of downhole elements 27 such as
tools, string subs including measurement-while-drilling tools,
drill collars, sensors and the like.
[0015] The present invention provides an apparatus and method that
allows the operator of a drilling operation to agitate the string
in a regular way during pumping of fluid through the string and
when there is weight on bit. The apparatus may telescopically
compress in response to weight on the string and the apparatus may
be used to pump the parts apart until they are stopped or the
pressure dissipates and weight urges them back together causing a
hammering effect each time the apparatus recompressed after being
pumped apart.
[0016] Because the hydraulic design is capable of generating
significant pressures, the agitator can lift a lot of weight. It
can, therefore, be placed close to the bit to have a very direct
hammering effect thereon. For example, the agitotaor can be placed
between the bit 22 and the drill collars 27b, such as the
non-magnetic drill collars in a directional system. Drill collars,
and in particular non-magnetic drill collars, are often called
"monels".
[0017] For example, with reference to FIGS. 2A and 2B, the present
invention may provide an apparatus. The apparatus may comprise a
tubular body 24 for connection within a string 20 including a first
mandrel 28 and a second mandrel 30. In this embodiment, the first
mandrel is depicted as positioned uphole from the second
mandrel.
[0018] The tubular body may also include a central bore 26a, 26b
defining the longitudinal axis of the body and permitting the flow
of fluids, for example drilling mud, through the tubular body from
its upper end to its lower end. The body may include the first
mandrel and the second mandrel with the central bore extending
through both mandrels. The first mandrel may include an outer wall
32 and an inner wall 34.
[0019] Central bore 26a, 26b may provide a conduit so that, if the
apparatus is connected into the string, the central bore becomes
continuous with the bore of the string. This may be of interest for
the pumping of drilling fluids from the surface through the string
and the body to a drill bit. The second mandrel may include an
outer wall 54 and an inner wall 56, the later which defines the
central bore 26b through the second mandrel. In one embodiment,
first mandrel 28 may include an inner sleeve 42 that forms an
extension through which extends portion 26a of the central bore.
Inner sleeve 42 extends generally coaxially with, and spaced from,
inner wall 34. An annular hollow chamber 36 is formed between
sleeve 42 and wall 34. Inner sleeve 42 defines an inner limit of
chamber 36, such that chamber 36 is defined as an annular space
defined between wall 34 and sleeve 42. The upper end of annular
chamber 36 is wall 48 and the lower end of the annular chamber is
open.
[0020] The second mandrel may be secured, at least partially,
within an annular hollow chamber 36 also defined by inner wall 34
of the first mandrel. Second mandrel 30 is telescopically arranged
with, and axially moveable, within the first mandrel. The first
mandrel and the second mandrel are telescopically arranged and
moveable between an axially compressed position FIG. 2B and an
axially expanded position FIG. 2A. In these positions, the madrels
remain connected. A first sealing part 52 and a second sealing part
58 may form part of the apparatus with one sealing part secured to
the first mandrel and the other sealing part secured to the second
mandrel and both sealing parts are, at least partially, within the
fluid flow of the tubular body. The first sealing part and the
second sealing part may be positioned to come together when the
mandrels are compressed, as by applying weight on the string in
which the apparatus is installed. When the sealing parts come
together they may form a fluid seal in the central bore to
substantially prevent the flow of fluids through the tubular
body.
[0021] First mandrel 28 may include an inwardly directed ledge 50
on its lower end. Ledge 50 is a return that reduces the inner
diameter across chamber 36.
[0022] The uphole end of the first mandrel may be connectable into
the string through a tubular connection 41a, for example a threaded
box or pin arrangement or any other tubular connection.
[0023] The inner sleeve may include first sealing part 52 on its
inner diameter such that first sealing part is positioned in the
central bore. For example, the first sealing part may form an
annular surface or a seat with a central aperture 53. The first
sealing part may extend into central bore to such an extent that
fluid flow is substantially not restricted through the central
aperture. In an alternate embodiment, first sealing part may extend
across central bore and have ports, rather than a central aperture,
therethrough to permit the substantially unrestricted fluid flow
past first sealing part.
[0024] Having described the various embodiments of the elements
associated with the first mandrel, the description now turns to the
second mandrel, with one embodiment thereof depicted in Figures 2A
and 2B. The second mandrel may connect into the string, for example
to the drill bit via a tubular connection 41b such as box or pin
threading, etc.
[0025] The second mandrel may insert into the first mandrel and
have a limited range of telescopic movement therein. For example,
the second mandrel may be inserted in annular chamber 36 with at
least a portion of outer wall 54 axially slidable along wall 34 and
inner wall 56 facing the outer surface of inner sleeve 42.
[0026] Extending inwardly from the inner wall and into central bore
26b may be second sealing part 58. The second sealing part may
include a profile portion 60, which can engage and create a fluidic
seal with first sealing part 52 of the first mandrel. In general,
the second sealing part may be a variety of relevant shapes such as
a dart, a ball point, conical, frustoconical, pyramidal and the
like that can plug the center aperture 53 of the first part. For
example, the profile portion of second part 58 can seat into and
seal against the edges of the center aperture exposed on first
sealing part 52.
[0027] Regardless of the specific shape, the second sealing part
may have adjacent thereto one or more flow ports 62 to permit the
flow of drilling fluid to pass and access the central bore of the
string downhole of the second mandrel (see flow direction
represented by lines X in FIG. 2A). The flow ports can be any shape
or size to permit such flow of drilling fluid. As will be discussed
further below, the flow ports may be positioned so that if the
matching profile portion engages the first sealing part drilling
fluids cannot flow past the first sealing part to access the
central bore there below. Further, the sealing parts are positioned
on their respective mandrels such that the sealing parts come
together when the mandrels are fully, telescopically
compressed.
[0028] In an alternative embodiment, where it is not desirable to
create a perfect seal in the apparatus second sealing part 58 may
also have one or more apertures 63 or the first sealing part may
have apertures, to permit the communication of a small flow of
fluids across the second sealing part even when the first sealing
part and the second sealing part come together. Apertures 63 may
permit fluidic communication there across so that drilling fluids
may have a restricted flow, arrows x1, past the second sealing part
even if matching profile 60 is sealed in the first sealing part. As
such, although sealing of the parts is contemplated to form a
pressure pulse sufficient to drive movement and operation of the
tool, such a seal may not be a perfect seal so that drilling fluid
circulation is not cut off completely.
[0029] In one embodiment, the uphole end of second mandrel 30 may
include a flange 64 that extends outward therefrom. The flange may,
for example, be integral such as a lateral extension of the second
mandrel or an additional component secured to the second mandrel
such as a safety clip. The flange may extend, at least partially,
radially out beyond ledge 50. The engagement of flange 64 with
ledge 50 may define the most axially extended position of the
limited range of telescopic movement between the first mandrel and
second mandrel 30, as shown in FIG. 2A.
[0030] The apparatus may further include a biasing member 38, if
desired, that biases the two mandrels into a partially compressed
position because the biasing member has a biasing strength. The
biasing member limits the extent to which the parts may be
telescopically pulled apart and therefore determines the stroke
length. The biasing member may also act as a shock absorber. As
will be appreciated, therefore, the biasing member may be omitted
if neither stroke length determination or shock absorption are of
interest.
[0031] Biasing member 38 may act between the first mandrel and
second mandrel 30 to bias them into a partially compressed
position. If the biasing member is disposed in the annular hollow
chamber between the flange 64 and the ledge 50, in the most axially
extended position, biasing member 38 is fully compressed between
the ledge and the flange, as shown in FIG. 2A.
[0032] Biasing member 38 may be any conventional biasing member
such as, for example, a compression spring. As a further example,
compression springs may be Belleville springs, coiled compression
springs, helical springs, variable pitch conical springs and the
like. A coiled compression spring may have a known, constant
biasing strength that allows the spring to resist applied
compressive forces to a predictable degree. If the compressive
forces exceed the biasing strength constant limit, the spring will
compress. As will be described further below, the biasing member
acts between the two mandrels to bias them into a partially
compressed position and in particular, to resist axial movement of
the sealing members 53, 60 apart beyond a certain limit. This
prevents damaging forces by the two mandrels being forcibly urged
apart, once pressure builds up above the sealing members.
[0033] The biasing member may be selected, when in a neutral
position, to leave some space between the sealing members 53, 60 in
order to allow the agitator to be stopped by removing the weight
from the string. In particular, by lifting the string off the
bottom, the second mandrel may drop by gravity or pump pressure
apart such that sealing members do not come together and cannot
cause vibration in the string.
[0034] The outer surface of inner sleeve 42 may have an annular
gland 66 to house an inner sealing member 68. The annular gland may
be a rounded groove, a square cut groove, an indentation etc. In
the illustrated embodiment of FIGS. 2A and 2B, annular gland 66 is
square cut. The inner sealing member may be an o-shaped sealing
ring that protrudes from the annular gland so that the sealing
member may be compressed between annular gland 66 and the inner
surface of the second mandrel creating therebetween a pressure and
fluid seal to prevent fluidic communication between the central
bore and the annular hollow chamber. It is to be understood herein
that the term "sealing member" will, unless otherwise specified,
refer to sealing members composed of materials suitable to create
and sustain a seal against the pressures associated with a downhole
wellbore drilling environment.
[0035] The inner wall of first mandrel 28 may have a lower annular
gland 70 to house a lower sealing member 72. The lower annular
gland may be a rounded groove, a square cut groove, an indentation
etc. In the illustrated embodiment of FIG. 2B, the lower annular
gland is square cut. The lower sealing member may be an o-shaped
sealing ring that protrudes from the lower annular gland so that
the lower sealing member may be compressed between the lower
annular gland and the outside surface of the second mandrel
creating therebetween a pressure and fluid seal to prevent fluidic
communication between the wellbore and the annular hollow
chamber.
[0036] In another embodiment of the present invention, flange 64
may include ports 82 to permit the bi-directional flow of fluids
therethrough to decrease the likelihood of a pressure build up on
either side of the flange. As one can appreciate, such a build up
could create a pressure lock impairing the functionality of the
agitation sub.
[0037] In one embodiment of the present invention, a dampener 74
may be installed to mitigate damaging contact between the sealing
members. The dampener, not shown, may be positioned between wall 48
and the flange.
[0038] In another embodiment of the present invention, there may be
a transmission arrangement 76 between the first mandrel and the
second mandrel to permit the transmission of torsional forces there
between. The transmission arrangement may, for example, be a
tongue-and-groove arrangement. The transmission arrangement may
include the lower sleeve having one or more splines 78 that engage
and axially move within one or more receiving grooves 80 on the
outer wall of second mandrel 30. The splines and grooves mate so
that rotation of one part is transferred to the other part. Of
course, the one or more splines may be included on the outer wall
of second mandrel and the one or more receiving grooves may be on
the inner surface of the lower sleeve.
[0039] In one embodiment, the mandrels may each be constructed of
one piece. In another embodiment, the mandrels may each be
constructed of two or more components. For example, as shown in
FIG. 2A, the first mandrel may be constructed of three primary
components, including: an outer sleeve 40 forming walls 32, 34,
inner sleeve 42 and a lower sleeve 44 forming ledge 50. The primary
components of the first mandrel may define the lateral walls of the
annular hollow chamber. For example, lower sleeve 44 may threadedly
connect with outer sleeve 40 proximal its lower end. The inner wall
of outer sleeve 40, above the connection point with lower sleeve
44, may define an inner wall 34 open to the annular hollow chamber.
The inner sleeve may threadedly connect to outer sleeve 40, below
the tubular connection and above the end wall. The outer wall of
the inner sleeve may extend below the end wall to define an inner
wall and of the annular hollow chamber.
[0040] In operation, the apparatus can be placed in a string and
positioned downhole. The apparatus may be connected in-line with a
wellbore string so that the position of second mandrel in the first
mandrel is dependent upon weight on the string; applying torsional
and axial forces on the string to position the first mandrel and
the second mandrel in the fully compressed position; pump fluids
through the string to develop a fluid pressure overcoming the
weight on bit holding the first mandrel and the second mandrel in a
sealing position and driving the first mandrel and the second
mandrel apart; allowing the pressure to dissipate when the first
mandrel moves out of sealing position with the second mandrel such
that the first mandrel returns back to a sealing position against
the second mandrel; and continuing to pump fluids through the
string to create an agitation effect of the first mandrel and the
second mandrel being pumped apart and then returned to a sealing
position
[0041] For example, when the string is urged down against the
bottom or against frictional forces below the apparatus, herein
called weight on bit, the apparatus is driven to axially compress,
which causes the sealing members to come together (FIG. 2B). When
fluid is pumped through the string, it is stopped by the seal
formed by the seated sealing parts and parts 52, 58 can only be
forced apart when sufficient pressure builds up in bore 26a The
force must be sufficient to lift mandrel 28 off mandrel 30.
[0042] When the pressure builds, the parts will be forced apart,
causing mandrels 28, 30 to move into their axially extended
position. Then, when the pressure dissipates by passage through
bore 26b, the weight of the string causes the sealing parts to come
back to together (FIG. 2B) until pressure forces them apart again
(FIG. 2A). Thus, the effect is a regular hammering and agitation in
the string as the parts cycle: pressure forces the parts apart and
then they come back together.
[0043] In the sealing position, the profile of the second sealing
part may seat in and create a fluidic seal with the profile of the
first sealing part, as shown in FIG. 2B, and thereby prevent the
flow of fluids there through (except for any small flow through
port 63). The fluidic seal may be created by the profile of the
second sealing part blocking central aperture 53 of the first
sealing part, which prevents the flow of fluids through the central
bore of the tubular body.
[0044] The fluidic seal may prevent any fluid communication across
the first sealing part so that, for example, drilling fluids being
pumped from surface down the central bore of the string will no
longer communicate below the fluidic seal provided by parts 52, 58.
The effect of creating such a fluidic seal, while drilling fluid
continues to be pumped from surface, is agitation and hammering in
the string.
[0045] If the apparatus is positioned between the drill bit and the
drill collar, driving the first mandrel and the second mandrel
apart includes lifting a drill collar upwardly (i.e. toward
surface) away from the drill bit. Thus, the agitation and hammering
can be applied very close and perhaps directly at the drill
bit.
[0046] The first and second mandrel may be arranged so that
torsional forces are transmitted between the two mandrels. For
example, the lower sleeve may have one or more splines that engage
and axially move within one or more receiving grooves on the outer
wall of second mandrel that mate with the one or more splines, or
vice versa, the one or more splines may be included on the outer
wall of second mandrel and the one or more receiving grooves may be
on the inner surface of the lower sleeve.
[0047] The previous description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
present invention. Various modifications to those embodiments will
be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the present invention is not intended to be limited to the
embodiments shown herein, but is to be accorded the full scope
consistent with the claims, wherein reference to an element in the
singular, such as by use of the article "a" or "an" is not intended
to mean "one and only one" unless specifically so stated, but
rather "one or more". All structural and functional equivalents to
the elements of the various embodiments described throughout the
disclosure that are known or later come to be known to those of
ordinary skill in the art are intended to be encompassed by the
elements of the claims. Moreover, nothing disclosed herein is
intended to be dedicated to the public regardless of whether such
disclosure is explicitly recited in the claims. No claim element is
to be construed under the provisions of 35 USC 112, sixth
paragraph, unless the element is expressly recited using the phrase
"means for" or "step for".
* * * * *