Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SEALED AND HYDROSTATICALLY LOCKABLE RETRIEVABLE MWD
LANDING SYSTEM
FIELD OF THE INVENTION
The present invention relates to a component of a drill string for use in
directionally drilling of oil wells, and more particularly to an improved mule
shoe
assembly for downhole MWD ("measurement while drilling") operations as part of
a drill
string, having an outer mule shoe member which receives therein a directional
measurement tool having electronic ensing components and/or mud pulser units
therein
for sensing and transmitting, respectively, directional drilling data from
downhole to
surface during drilling. Due to its unique configuration the mule shoe
assembly of the
present invention is able to make use of seals which seal the area of mating
engagement to thereby resist ingress of abrasive substances such as sand which
otherwise disadvantageously causes extreme wear and ultimate loss of
functionality of
the mule shoe assembly, and by such configuration is further adapted to use
hydrostatic
forces to better retain the two components together.
BACKGROUND OF THE INVENTION
For directional drilling of oil and gas wells, a drill string generally has,
at its distal
end, a rotating drill bit which is energized by a hydraulically-powered "mud"
motor.
Such drill bit and hydraulically-powered motor are generally contained in a so-
called
"bent sub" used in directional drilling of wells using so-called MWD
(measurement-
while-drilling) tool orientation directional sensing apparatus.
A universal bottom hole orienting sub assembly ("UBHO orienting sub")
containing a mule shoe assembly and which contains therein a directional
measurement
tool, is generally threadably coupled to the bent sub, uphole therefrom, which
assists the
drill operator in directional drilling, in the manner described below.
Specifically, the directional measurement tool within the mule shoe assembly
which forms part of the UBHO orienting sub contains electronic circuitry for
determining
drill bit location and orientation and generally also information about the
geology of the
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rock being drilled in, to thereby assist and allow the drill operator to
effectively "steer" the
bit in a desired direction during drilling. Such mule shoe assembly and UBHO
sub
together form part of the drill string bottom hole assembly ("BHA").
The UBHO sub is adapted at its downhole end to be threadably connected to the
bent sub, and at its uphole end to be threadably connected to various other
bottom hole
assembly components, typically the non-magnetic tool collar, with the mud
pulser
apparatus for transmitting downhole drilling orientation information from the
directional
measurement tool uphole to surface sitting within the mule shoe assembly.
The UBHO sub has, as one component thereof, a hollow cylindrical outer
member, colloquially known to persons of skill in the art as a "mule shoe",
which typically
in prior art mule shoe assemblies to date has an arcuate camming surface on an
interior
surface thereof for landing against a mating arcuate camming surface on an
exterior
surface of a directional measurement tool when such directional measurement
tool is
co-axially inserted and caused to nest within the outer mule shoe member, to
form a
mule shoe assembly. The matingly-engageable arcuate camming surfaces are
adapted
to engage in a manner so as to cause the angular position of the inserted
(nested)
directional measurement tool within the outer mule shoe member to be fixed and
further
precisely known relative to the outer mule shoe member in the resulting mule
shoe
assembly.
The mule shoe outer member of a mule shoe assembly of the prior art typically
has an elongate slot (aperture) perpendicularly disposed to but extending
through the
outer surface of the mule shoe outer member housing and into the hollow bore
of the
mule shoe, which elongate slot is adapted for receiving therein a similarly
shaped
elongate key member which extends therethrough and further into an axially-
extending
channel in the directional measurement tool when the directional measurement
tool is
inserted within the bore of the mule shoe and the arcuate camming surfaces on
the
respective mule shoe member and inner directional measurement tool engage and
thereby cause each of the aforesaid components to be rotated into a desired
relative
angular relation to one another thereby aligning the key member with the
channel. The
key member when inserted and pinned in such inserted position within the
channel of
the measurement tool fixedly keeps the angular relation of the inner
directional
measurement tool relative to the outer mule shoe member constant, although
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=
longitudinal movement of the measurement tool can occur by movement of the key
µ
member within the channel of the directional tool member.
To prevent such relative longitudinal movement between such two components
of the mule shoe assembly a threaded set screw (or screws) or dowel member is
used,
which extends from the mule shoe member to the inner directional measurement
tool so
as to secure and "lock" the directional measurement tool within the mule shoe
member
and prevent longitudinal movement of the directional measurement tool within
the mule
shoe member and thereby allow the UBHO sub (containing the mule shoe and
directional measurement tool locked therewithin) and the bent sub and drill
bit attached
thereto to be lowered downhole so as to permit directional drilling.
Disadvantageously and problematically with such prior art mule shoe
assemblies,
circumferential seals are not capable of being provided within the mule shoe
assembly of
such designs due to the arcuate camming surfaces employed which extend
longitudinally of the outer mule shoe and the directional measurement tool. As
a result,
abrasive materials such as drilling fines, sand and other detritus from
drilling operations
frequently enters the mule shoe assembly during drilling. Specifically, sand,
detritus,
and drilling fines invariably enters the area of mating engagement between the
directional measurement tool and the outer mule shoe member. Due to extreme
vibration to which the mule shoe assembly is exposed during drilling (such
vibration
caused by large and rapid pressure pulses created by the mud pulser which uses
rapid
pressure fluctuations of the drilling mud to transmit drilling data to
surface) small
longitudinal and/or angular movement is created between the outer mule shoe
member
and the directional tool component.
Such vibrational movement (albeit initially small) due to the large numbers of
vibration cycles needed to transmit ever increasing quantities of data to
surface, due to
the highly abrasive nature of drilling fines and fluids containing such fines
or sand,
causes rapid and extensive wear of each of the two components at the point of
coupling
Such wear leads to loss of the fixed angular orientation of the directional
measurement
tool relative to the outer mule shoe member, and thus invariably leads to loss
in
accuracy of the measurement tool orientation and thus loss of ability to sense
the
direction of drilling of the drill bit.
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In addition, such imparted vibration and exposure to abrasive materials causes
extensive wear of the two components such that directional sensor orientation
is lost,
which directly results in the loss of the ability to "steer" the drilling bit
from surface by
rotating the drill string (and bit attached thereto) during directional
drilling operations.
Either of the above scenarios necessitates the entirety of the drill string to
be
"tripped out" of the well being drilled in order to replace the worn mule shoe
assembly.
Such frequent "tripping out" of the directional drilling drill string greatly
slows the
drilling process, and greatly adds to the expense of drilling.
Accordingly, a real and serious need exists in the directional drilling
industry for a
robust mule shoe assembly which can withstand extensive and lengthy periods of
exposure to significant vibration in abrasive drilling environments, yet
continue to
operate effectively.
More particularly, and in addition, a real and serious need exists in the
directional
drilling industry for an integral mule shoe assembly which permits a
directional
measurement tool to be easily installed in an outer mule shoe component
thereof, but at
the same time when the two components are assembled and when such assembly is
used downhole as part of a drill string in an abrasive environment, prevents
sand and/or
drilling fines from entering the assembly in the region of mating engagement
between
the outer mule shoe and the inner concentrically-located directional
measurement tool.
US 7,900,698 to a "Downhole Wet-Mate Connector Debris Exclusion System"
teaches a downhole wet connector system, principally for connecting two fibre
optic
cables together (although other types of connectors could be used). Such wet
connector
system consists of two half-members 12, 14, each having respective orientation
profile
16, 18 respectively, to ensure proper and consistent angular alignment of one
half
member relative to the other during coupling. US '798 discloses a check valve
106 (ref.
col 3, line 43 and Fig. 1C). However, such check valve 106 is not for the
purpose of
allowing release of fluid during coupling of the two half members but appears
instead,
after coupling, to allow injection and subsequent retention therewithiin of a
cleaning/flushing fluid (preferably a fluid such as hydroxyethylcellulose)
into the coupled
device, wherein the fluid thereafter functions to assist in providing a
presence of fluid as
opposed to open space which will then hopefully discourage ingress of dirt and
other
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contaminants. Thus the check valve 106 of US '698 in no way assists in
coupling the
two halves together by allowing egress of air out of the coupled unit so that
hydrostatic
force outside the half-members will assist in ensuring the half members remain
coupled
together.
SUMMARY OF THE INVENTION
The present invention by its novel configuration avoids the dowel or "threaded
screw" arrangement of the prior art, and further avoids the arcuate landing of
the outer
mule shoe member using a key within a slotted channel, and instead using a
different
landing arrangement further incorporating protective seals to protect the
landing area of
the mule shoe from abrasive substances so as to greatly prolong the life of
the mule
shoe and avoid expensive "tripping out" operations to replace worn mule shoe
assemblies.
Specifically, to greatly improve the resistance of the mule shoe assembly to
wear
in the abrasive downhole environments in which such mule shoe apparatus
operate as
compared to the prior art mule shoe assemblies as described herein, the
present
invention provides for a mule shoe assembly making use of mating "half
members",
which in a preferred embodiment are mating "half-moon" members, on
respectively the
outer mule shoe member and the directional tool member (the latter being
concentrically
located within the bore of the outer mule shoe member) which manner of mating
engagement allows using seal means, specifically a pair of circumferential
seals such as
"o" rings or flexible `lip' or `cup' seals as further elaborated on below,
respectively located
at opposite ends of, and bounding, the mating "half moon" members on the outer
mule
shoe and the inner directional measurement tool. The seals, in conjunction
with the
particular configuration for landing the direction tool and housing within the
mule shoe,
greatly reduces sand and/or drilling fines from coming into contact with such
landing
area, namely with the half-moon members of the mule shoe and directional tool
housing.
Accordingly, in one broad aspect of the present invention, the invention
comprises a mule shoe assembly for use in directional drilling of wells, which
mule shoe
assembly is adapted to lockingly secure a directional measurement tool therein
and
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,
,
further resist ingress of abrasive substances such as drilling fines coming
into contact
with the mule shoe landing area, comprising:
=
(i) an outer mule shoe member, having:
(a) a longitudinal bore, a portion of which is
cylindrical;
(b) a half member
located within said cylindrical portion of said
longitudinal bore, fixedly secured to a circumferential portion of said
longitudinal bore about at least a portion of a circumference thereof;
(ii) a cylindrical housing for containing a direction-indicating tool, said
housing adapted for insertion in said longitudinal bore of said outer mule
shoe member,
comprising:
(a)
a half member situated on an circumferential portion of an outer
surface of said housing, extending longitudinally along said portion of said
outer surface and protruding radially outwardly about said portion of said
outer surface of said housing, adapted to matingly engage said half
member located within said mule shoe member so that, when matingly
engaged, angular rotation of the housing within the mule shoe member is
prevented; and
(iii) a pair of circumferential seals, respectively situated proximate
mutually
opposite ends of said mule shoe member and said housing when said housing is
inserted in said longitudinal bore, adapted to reduce ingress of drilling
fines and fluids
containing drilling fines into an interstitial area bounded by said pair of
circumferential
seals.
Advantageously, the pair of circumferential seals perform a dual function-not
only
do they prevent ingress of abrasive matter, including drilling fines suspended
in drilling
fluids, into the landed area of engagement of the inner housing and the outer
mule shoe
member, but they further cause, due to such created seal, hydrostatic forces
to
effectively exert a continual compressive force which continually forces the
two members
into landed engagement with each other thus better allowing the mule shoe
assembly to
maintain locking landed engagement of the inner tool within the outer mule
shoe despite
these vibrational forces which tend to otherwise cause separation of the outer
mule shoe
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,
and the inner tool. In such manner the mule shoe assembly is able to better
withstand
. vibrationally-imparted separation forces when downhole, thus
reducing or eliminating
relative vibrationally-induced movement between the mule shoe and the inner
directional
tool, thus permitting the mule shoe assembly to avoid and reduce wear on its
components when used in directional drilling , thus allowing for substantially
longer life of
the assembly.
In a preferred embodiment of the above mule shoe assembly a check valve,
(typically a ball-style check valve, but other similarly-operating check
valves are
contemplated as known to persons of skill in the art) is situated intermediate
said pair of
circumferential seals. Such check valve is used to facilitate and allow escape
of
trapped fluid in the interstitial space between such outer mule shoe member
and inner
directional measurement tool during insertion of the directional tool member
concentrically within the bore of the outer mule shoe member. Conversely, such
check
valve resists and prevents fluids including drilling fines from entering such
interstitial
space and area of mating engagement, namely at the respective mating "half-
moon"
members. In addition, due to hydrostatic forces exerted on the individual mule
shoe and
directional tool housing, particularly when downhole there is huge pressure
differentials,
the use of the check valve in such preferred embodiment serves to allow
forcible locking
(via allowing fluid to be evicted from within the drilling assembly and
thereby allowing
drilling fluid hydrostatic pressure exerted on the exterior of the outer mule
shoe and
directional tool housing to force the two members together) so as to prevent
separation
while at the same time preventing sand, grit, and drill fines from getting
into the mule
shoe assembly in areas which could cause wear, particularly in the area of
landing of the
two members together in the region of the two half-moon members located in the
area
between the pair of circumferential seals.
Accordingly, in a preferred embodiment of the invention the above mule shoe
assembly further comprises a check valve situated in said outer mule shoe
member,
adapted to allow egress of fluid from within said mule shoe member upon
insertion of
said housing in said longitudinal bore, and configured to prevent ingress of
fluid into said
longitudinal bore.
In a second embodiment, mating "half-moon" members on respectively the outer
mule shoe member and inner directional measurement tool are likewise employed,
as
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are seal means disposed at opposite ends of the mule shoe assembly seal, so as
to seal
therewithin the half-moon mating members. However, in such second alternative
embodiment of the mule shoe assembly of the present invention, no ball-style
check
valve is needed or employed. Rather, in such second alternative embodiment at
least
one (or both) of the seal means incorporate a flexibile lip seal or flapper
type seal, which
allows release of fluid from within the mule shoe when the directional tool is
inserted into
the bore of the mule shoe member, but which resists ingress of fluid into an
interior of
the mule shoe assembly and likewise thereby serves to hydrostatically lock the
tool
within the mule assembly once the directional measurement tool is inserted
therewithin.
Accordingly, in a second embodiment of the mule shoe assembly of the present
invention at least one of the circumferential seals comprises a "flapper" type
seal
adapted to allow egress of fluid from within said mule shoe member upon
insertion of
said housing in said longitudinal bore, and to prevent ingress of fluid into
said
longitudinal bore when said housing is inserted in the longitudinal bore and
engaging
such at least one circumferential seal.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate one or more exemplary embodiments of
the present invention and are not to be construed as limiting the invention to
these
depicted embodiments:
FIG. 1A is an exploded perspective view of a mule shoe assembly of the prior
art, which uses a threaded set screw to lockably (non-releasably) secure an
inner tool to
an outer mule shoe;
FIG. 1B is a non-exploded view of the prior art mule shoe assembly of FIG. 1A;
FIG. 2 is cross-sectional view through the prior art mule shoe assembly of
FIG.
1B along section A-A thereof;
FIG. 3 is enlarged view of encircled area "B" of FIG. 2;
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FIG. 4 is an exploded perspective, partial cross-sectional view of one
embodiment of the mule shoe apparatus of the present invention, shown coupled,
on the
right hand side thereof, to a portion of a drill string;
FIG. 5 is a side, partial cross-sectional view of the mule shoe apparatus and
drill
string of Fig. 4, with the housing partially inserted in the outer mule shoe;
FIG. 6 is an enlarged view of the mule shoe apparatus shown in Fig. 5, showing
the housing fully inserted within the mule shoe;
FIG. 7 is a further side perspective view, in partial section, of the mule
shoe
apparatus of Fig. 6, showing the aperture in the half-moon member of the mule
shoe
member which provides fluid egress from the bore of the mule shoe member;
FIG. 8 is a perspective partial sectional view of an alternative embodiment of
the
mule shoe apparatus of the present invention, in which the check valve is
located in a
different location but still intermediate the two circumferential "o" rings
situated at
respectively mutually opposite ends of the mule shoe assembly;
FIG. 9 is a perspective partial sectional view of a still further alternative
embodiment of the mule shoe apparatus of the present invention, in which a
pair of
check valves are positioned still intermediate the two circumferential "o"
rings situated at
respectively mutually opposite ends of the mule shoe assembly; and
FIG. 10 is a still further alternative embodiment of the present invention,
which
does not employ a check valve but instead utilizes a circumferential "cup"
type seal
means at one end of the mule shoe assembly which allows egress of fluid from
between
the cup seal and the "o" ring seal during insertion of the housing, but which
resists
ingress of fluid and thereby assists in hydrostatically locking the
measurement tool within
the mule shoe assembly.
DETAILED DESCRIPTION OF SOME OF THE PREFERRED EMBODIMENTS
Mule shoe assemblies 10 of the prior art, as shown in FIG.'s 1A, 1B, 2, & 3
hereto, typically comprise a substantially cylindrical mule shoe member 12
having a
hollow bore 28. Downhole end 13 of mule shoe 12 is adapted to be threadably
coupled
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to a mud motor and associated drill bit (not shown). Uphole end 17 thereof
mule shoe
12 is adapted to be secured to additional BHA components, such as a mud pulser
(not
shown) .
Camming member 24 of mule shoe 12 has an arcuate camming surface 14
thereon, and is insertable within bore 28 and is typically welded in a desired
location
and angular orientation within interior bore 28 of mule shoe 12.
Inner cylindrical tool member 16 is adapted to be inserted within mule shoe
12,
as shown in FIG. 1A & 1B. Inner tool housing member 16 is adapted to contain
within
its bore 40 a directional measurement tool (not shown), which is retained in
such bore
40 by threaded sleeve 42 and associated "0" ring 44.
A direction sensing tool and associated electronics, as well as a mud pulser
apparatus (not shown) are adapted to be contained within inner tool housing
member
16. Inner tool housing 16 possesses an exterior arcuate camming surface 18 on
an
outer periphery 19 thereof, which shape is complementary to arcuate camming
surface
14, and which camming surface 14 is adapted for landed engagement with camming
surface 18 upon insertion of inner tool housing 16 within outer mule shoe 12.
Threaded set screws 30 are provided, adapted to be threadably inserted within
apertures 32 in mule shoe 12, for the purposes of longitudinal fixation of
inner tool
member 16 within mule shoe 12. When inner tool housing member 16 is inserted
in
bore 28 of outer mule shoe 12, mutual engagement of each of arcuate camming
surfaces 14 and 18 causes relative rotation of the inner tool housing member
16 relative
to outer mule shoe 12, so that apertures 32 in mule shoe 12 become aligned
with, and
positioned directly above, respective apertures 34 in inner tool housing
member 16.
Upon mutual alignment of apertures 32 with apertures 34 in inner tool housing
member 16, set screws 30 may further be tightened to thereby extend into
apertures 34
in inner tool housing member 16, thereby fixedly securing inner tool housing
16 (with a
directional tool inserted within a bore 40 thereof) to outer mule shoe 12.
For further maintaining the angular position of inner tool housing 16 relative
to
outer mule shoe 12, a channel 41 is typically further provided on outer
periphery 19
thereof. Upon landed engagement of the respective arcuate camming surfaces 14
and
18 of the respective mule shoe 12 and inner tool housing member 16, channel 41
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becomes aligned with slot 60 in mule shoe 12. Key member 70 is then inserted
in slot
60 which simultaneously engages channel 41 in inner tool member 16, thereby
preventing any further insertion of inner tool housing member 16 within bore
28 of mule
shoe 12 and further preventing any relative angular rotation of inner tool
housing
member 16 (and directional tool member contained therein) relative to mule
shoe 12.
Key member 70 may be fixedly secured in slot 60 in mule shoe 12 by means of
"friction
fit" pin members 80. The inner tool 16 is thus effectively landed within mule
shoe 12.
Disadvantageously, however, as mentioned above, due to the arcuate camming
surfaces 14, 18 used to angularly orientate and land the directional tool
housing 16
within outer mule shoe member 12, circumferential seals cannot be used.
Accordingly,
when such mule shoe assembly 10 is downhole, abrasive substances such as drill
tailings and sand enter such landing area. Due to large and rapid pressure
oscillations
and vibration during drilling (such vibration caused in part from operation of
mud pulsers
downhole within or proximate the mule shoe assembly 10 for transmitting data
from the
directional measurement tool to surface) small angular and/or longitudinal
movement of
the inner directional tool 16 relative to the mule shoe 12 occurs. Due to the
highly
abrasive nature of the drilling fluid, even wear on specially treated and
surface-hardened
metal surfaces occurs. Such initial wear has a negative cascading effect,
since as wear
progresses it causes greater space between mating parts, namely in the channel
14 and
key member 70, and the area of landed engagement at surfaces 14, 18, which
greater
space allows further entry of fluids containing abrasive substances which
begets still
further wear, until ultimately angular fixation of the mule shoe 12 relative
to the
directional tool housing inner tool 16 is completely lost and/or torque cannot
be
transmitted, rendering effective directional steering of the downhole drill
bit (not shown)
impossible. "Tripping out" of the entire drill string to replace the defective
mule shoe
assembly 10 is then required, resulting in great loss of time and money.
Accordingly, in order to overcome the aforementioned disadvantages with the
mule shoe assemblies 10 of the prior art, a mule shoe assembly 100 is provided
as
shown in FIG's 4-10 inclusive.
In a first embodiment of the present invention , various views of which are
shown
in Figs. 4-7, mule shoe assembly 100 comprises an outer mule shoe member 120
and a
tool housing 160 for containing a direction-indicating tool therewithin (not
shown) . Outer
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mule shoe member 120 is provided with a longitudinal bore 280, a portion of
which is
cylindrical. A half-moon member 124, one embodiment of which is best shown in
Fig. 4
in perspective view, is fixedly secured, typically by welding, to a
circumferential portion
125 of longitudinal bore 280 about at least a portion 126 of a circumference
of bore 280.
Directional tool housing 160, as shown in Fig. 4, is typically hollow and is
adapted for containing therein a direction-indicating tool (not shown), such
tool being
retained therein via a threaded end cap member 130, which end cap member 130,
as
further explained below, possesses at least one circumferential seal in the
form of at
least one 'o' ring 300 extending about the circumference thereof.
Tool housing 160 and the directional tool therein (not shown) are adapted for
insertion in longitudinal bore 280 of outer mule shoe member 120, as best
shown
(partially inserted) in Fig. 5, and fully inserted in Fig. 6.
A half-moon member 134 is provided on the directional tool housing 160, namely
on a circumferential portion 135 of an outer surface 137 of tool housing 160,
which half-
moon member 134 extends longitudinally along portion 135 of outer surface 137
and
protrudes radially outwardly from said portion 135 of outer surface 137, and
is of a
similar diameter to that of half ¨moon member 124, as may be seen from Fig's.
4 & 5.
Half- moon member 134 is adapted to matingly engage half-moon member 124
within mule shoe member 120 when tool housing 160 is inserted within
longitudinal bore
280 of mule shoe member 120 so that, when each of half-moon members 124, 134
matingly engage as shown in Fig. 5, angular rotation of tool housing 160
relative to mule
shoe member 120 is prevented.
A pair of circumferential seals in the form of 'o' rings 300 are provided in
the first
embodiment of the mule shoe assembly 100 of the invention, respectively
situated
proximate mutually opposite ends 121, 122 thereof. Such circumferential seals
300 may
be situated in distal ends 161, 162 of the directional tool 160, or in distal
ends 121, 122
of the outer mule shoe 120, or a combination of the foregoing whereby at one
end 122 of
mule shoe assembly 100 such are located within annular rings 320 located
within outer
mule shoe 120, and at another opposite end of mule shoe assembly 100 are
located in
annular rings 375 located on directional tool member 160 , as shown in Fig. 5.
In all
instances such circumferential seals 300 which serve to prevent ingress of
drilling fines
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and fluids containing drilling fines into said mule shoe assembly 100, namely
into
interstitial landed areas 400, 401 bounded by said pair of circumferential
seals 300.
Specifically, in the first embodiment shown in Fig. 4 -7, a pair of seal
grooves
320 are provided proximate distal end 122 of outer mule shoe 120, in which 'o'
rings 300
may be placed. Such 'o' rings 300 engage distal end 162 of directional tool
160 when
directional tool 160 is concentrically located in bore 280 of outer mule shoe
member 120,
as shown in Fig. 5 (partially inserted) and Fig. 6, 7 (fully inserted).
Similarly, a pair of seal grooves 375 may be situated at a distal end 161 of
tool
housing 160, in which similar 'o' rings 300 may similarly be placed, which
sealingly
engage distal end 121 of outer mule shoe member 120 when directional tool 160
is fully
inserted in outer mule shoe 120, as shown in Fig. 6 & 7, so that interstitial
landed area
400, 401 is sealed from abrasives, including drilling fluid containing drill
tailings and
sand.
Advantageously, seals 300 allow hydrostatic forces exerted on the mule shoe
assembly 100 when downhole to maintain directional tool member 160 in landed
engagement within mule shoe assembly 100.
In addition, however, if desired, similar set screws 30 as used in the prior
art and
as shown in Fig 1A, Fig. 2, and Fig. 3 or alternatively dowel pins (not
shown), may
similarly be employed to assist in maintaining directional tool 160 within
outer mule shoe
120, particularly when downhole hydrostatic forces may not be acting.
In this first embodiment of the mule shoe apparatus 100 of the present
invention
shown in Fig.'s 4-7 a single check valve 500 is situated within a borehole 501
located in
outer mule shoe member 120. Check valve 500 contains a resiliently biased
member,
such as a ball 502 biased via a spring 503 over aperture 520 in outer mule
shoe member
120. A bore 700 is further provided in half ¨moon member 124, which aligns
with bore
520 in mule shoe member 120. Check valve 500 is accordingly adapted to allow
egress
of fluid from within said mule shoe member 120, namely egress of fluid such as
air which
is expelled during insertion of tool housing 160 in bore 280 and in particular
during the
mating engagement of half-moon members 124, 134 upon insertion of said housing
160
in said longitudinal bore 280.
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Conversely, check valve 500 operates to prevent ingress of air or such fluid,
including and in particular drilling fluid containing abrasive drill tailings
or sand, into
interstitial landed area 400, 401 via borehole 501 and bore 700.
A second embodiment of the invention is shown in Fig. 8 and similarly utilizes
a
half-moon member 124 situated on a portion 126 of interior of longitudinal
bore 280. In
such embodiment half-moon member 124 is of a slightly different configuration
than that
shown in Fig. 4-7, namely having eliminated therefrom the circular collar 801
(see Fig.
7). Borehole 501 is provided, which aligns with aperture 520, both of which
are in fluid
communication with interstitial landed area 400. Borehole 501 is adapted to
contain a
check valve 500 (not shown in Fig. 8) to allow egress of fluid such as air
when said
directional tool member 160 and associated half-moon member 134 matingly
engage
half-moon member 124 within mule shoe member 120. Advantageously in such
second
embodiment the need for a bore 700 through half-moon member 124 may be
dispensed
with, thus dispensing with a machining step.
Fig. 9 shows a third embodiment of the mule shoe assembly 100 of the present
invention, which is further adapted to improve the ease by which fluid may be
allowed to
egress landed areas 400, 401 when the directional tool member 160 is inserted
within
mule shoe member 120, which uses two boreholes 501, each adapted to contain an
associated check valve 500, and which two check valves 500 together operate to
allow
egress of all fluid such as air from within said mule shoe assembly 100 when
said
directional tool member 160 and associated half-moon member 134 matingly
engage
half-moon member 124 within mule shoe member 120. Again, due to the
elimination of
a circular collar 801 (see Fig. 7) on half moon member 124, fluid can
effectively egress
from within interstitial areas 400, 401 via respective check valves 500, and
no bore 700
is needed within either of half moon members 124, 134.
Fig. 10 shows a separate, fourth embodiment of the mule shoe assembly 100 of
the present invention which eliminates the borehole(s) 501 and ball-style
check valve(s)
500, and instead utilizes, in the embodiment shown, an annular "flapper" style
seal
member 308 which effects a seal between distal end 161 of directional tool
member 160
and mule shoe member 120 at one end 121 of mule shoe assembly 100. An
externally-
threaded nut 311 may be used to retain seal member 308 within outer mule shoe
member 120, as shown in Fig. 10.
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CA 02786471 2012-08-16
,
,
Advantageously, flapper style seal member 308 is of a resiliently flexible
material
such as synthetic rubber, and allows egress of fluid from interstitial areas
400, 401
during insertion of directional tool member 160 within mule shoe member 120,
but which
prevents ingress of fluid, including and in particular drilling fluid
containing abrasive drill
tailings or sand, into interstitial landed area 400, 401. A small borehole 603
may
optionally be provided in half-moon member 124, to allow fluid communication
between
landed areas 401 and 400, respectively, to better allow egress of all fluid
such as air
which will be forcibly voided upon insertion of directional tool 160 within
outer mule shoe
120.
In the embodiment shown in Fig. 10 seal member 308 in combination with seals
300 at mutually opposite end 121 of outer mule shoe 120, allow hydrostatic
forces
exerted on the mule shoe assembly 100 when downhole to maintain directional
tool
member 160 in landed engagement within mule shoe assembly 100.
The above describes preferred embodiments of the invention. Other variations
will now be apparent to those of skill in the art. In view of the foregoing
the scope of the
claims should not be limited by the preferred embodiments set forth in the
foregoing
examples. Instead, the claims should be given the broadest interpretation
consistent
with the description as a whole, and are not to be limited to the preferred or
exemplified
embodiments of the invention.
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