U.S. patent application number 13/587687 was filed with the patent office on 2014-02-20 for sealed and hydrostatically lockable retrievable mwd landing system.
This patent application is currently assigned to PACESETTER DIRECTIONAL DRILLING LTD.. The applicant listed for this patent is DUSTIN AASEN, AXEL SCHMIDT. Invention is credited to DUSTIN AASEN, AXEL SCHMIDT.
Application Number | 20140048332 13/587687 |
Document ID | / |
Family ID | 50099275 |
Filed Date | 2014-02-20 |
United States Patent
Application |
20140048332 |
Kind Code |
A1 |
SCHMIDT; AXEL ; et
al. |
February 20, 2014 |
SEALED AND HYDROSTATICALLY LOCKABLE RETRIEVABLE MWD LANDING
SYSTEM
Abstract
A sealed mule shoe assembly for use in directional drilling,
comprising an outer mule shoe and an inner housing for containing a
directional measurement tool which is slidably insertable in the
outer mule shoe. The mule shoe assembly advantageously has
half-moon mating surfaces which advantageously allow use
circumferential seals to thereby prevent ingress of abrasive
materials into the landing area between the outer mule shoe and the
inner housing, thereby greatly prolonging the life of the mule shoe
assembly. Such seals further make use of hydrostatic forces
downhole which cause locking landed engagement of the inner tool
within the outer mule shoe. Cup seals or a check valve are used to
allow escape of fluid when the inner tool is inserted within the
outer mule shoe, and similarly prevent ingress of abrasive fluids
and drill cuttings into the area of landed engagement.
Inventors: |
SCHMIDT; AXEL; (Calgary,
CA) ; AASEN; DUSTIN; (Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHMIDT; AXEL
AASEN; DUSTIN |
Calgary
Calgary |
|
CA
CA |
|
|
Assignee: |
PACESETTER DIRECTIONAL DRILLING
LTD.
Calgary
CA
|
Family ID: |
50099275 |
Appl. No.: |
13/587687 |
Filed: |
August 16, 2012 |
Current U.S.
Class: |
175/45 |
Current CPC
Class: |
E21B 47/017
20200501 |
Class at
Publication: |
175/45 |
International
Class: |
E21B 47/022 20120101
E21B047/022 |
Claims
1. 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 further resists ingress
into an interior of said mule shoe assembly of abrasive substances
such as drilling fines, 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.
2. A mule shoe assembly as claimed in claim 1, wherein each of said
half members comprise half-moon members.
3. A mule shoe assembly as claimed in claim 1 or 2, further
comprising: 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.
4. A mule shoe assembly as claimed in claim 1, wherein said
circumferential seals comprise a pair of `o` ring seals, and said
half members respectively each comprise half-moon members.
5. A mule shoe assembly as claimed in claim 4, wherein said check
valve is a ball-type check valve situated in said outer mule shoe
between said pair of `o` ring seals, having a ball resiliently
biased over an aperture in said outer mule shoe member and which
said aperture extends therethrough to said longitudinal bore.
6. A mule shoe assembly as claimed in claim 5, wherein said check
valve is positioned directly above said aperture, and said aperture
in said outer mule shoe member further extends through said
half-moon member situated therein into said longitudinal bore.
7. A mule shoe assembly as claimed in claim in claim 3, further
comprising a pair of check valves situated in said outer mule shoe
member intermediate said pair of `o` ring seals, 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.
8. A mule shoe assembly as claimed in claim 1, wherein said at
least one of said 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.
9. A mule shoe assembly as claimed in claim 8, wherein said at
least one "flapper" type seal is located in said mule shoe assembly
at an end thereof most closely proximate an extremity of said
housing when said housing is inserted within said longitudinal
bore.
Description
FIELD OF THE INVENTION
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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 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").
[0005] 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.
[0006] 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.
[0007] 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 longitudinal
movement of the measurement tool can occur by movement of the key
member within the channel of the directional tool member.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] Such frequent "tripping out" of the directional drilling
drill string greatly slows the drilling process, and greatly adds
to the expense of drilling.
[0014] 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.
[0015] 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.
[0016] U.S. Pat. No. 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 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
[0017] 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.
[0018] 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.
[0019] 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 further resist
ingress of abrasive substances such as drilling fines coming into
contact with the mule shoe landing area, comprising: [0020] (i) an
outer mule shoe member, having: [0021] (a) a longitudinal bore, a
portion of which is cylindrical; [0022] (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; [0023] (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: [0024] (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 [0025] (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.
[0026] 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 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.
[0027] 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.
[0028] 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.
[0029] In a second embodiment, mating "half-moon" members on
respectively the outer mule shoe member and inner directional
measurement tool are likewise employed, as 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.
[0030] 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
[0031] 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:
[0032] 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;
[0033] FIG. 1B is a non-exploded view of the prior art mule shoe
assembly of FIG. 1A;
[0034] FIG. 2 is cross-sectional view through the prior art mule
shoe assembly of FIG. 1B along section A-A thereof;
[0035] FIG. 3 is enlarged view of encircled area "B" of FIG. 2;
[0036] 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;
[0037] 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;
[0038] FIG. 6 is an enlarged view of the mule shoe apparatus shown
in FIG. 5, showing the housing fully inserted within the mule
shoe;
[0039] 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;
[0040] 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;
[0041] 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
[0042] 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
[0043] Mule shoe assemblies 10 of the prior art, as shown in FIGS.
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 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).
[0044] 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.
[0045] Inner cylindrical tool member 16 is adapted to be inserted
within mule shoe 12, as shown in FIGS. 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 "O" ring 44.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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 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 1.2 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.
[0050] 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.
[0051] 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 FIGS. 4-10
inclusive.
[0052] 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 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.
[0053] 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.
[0054] 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.
[0055] 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 FIGS. 4 & 5.
[0056] 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.
[0057] 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 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.
[0058] 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 V 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).
[0059] 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 FIGS. 6 & 7, so
that interstitial landed area 400, 401 is sealed from abrasives,
including drilling fluid containing drill tailings and sand.
[0060] 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.
[0061] 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.
[0062] In this first embodiment of the mule shoe apparatus 100 of
the present invention shown in FIGS. 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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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