U.S. patent number RE33,793 [Application Number 07/384,775] was granted by the patent office on 1992-01-14 for apparatus and method for forming an enlarged underground arcuate bore and installing a conduit therein.
This patent grant is currently assigned to Cherrington Corporation. Invention is credited to Martin D. Cherrington, William D. Cherrington.
United States Patent |
RE33,793 |
Cherrington , et
al. |
January 14, 1992 |
Apparatus and method for forming an enlarged underground arcuate
bore and installing a conduit therein
Abstract
An apparatus and method for drilling a pilot bore hole (B) along
an underground arcuate path (P) between two surface locations (O,
E). The pilot bore hole (B) is drilled in one direction with a
drill string (10) having a leading pipe section (10A) of a reduced
diameter to provide increased flexibility. Upon completion of the
pilot bore hole (B), a reamer (48) connected to a product conduit
(46) is connected to the drill string (10). Drill string (10) pulls
the reamer (48) and product conduit (46) along the pilot bore hole
(B) in an opposite direction for enlarging the bore hole (B) to
receive the product conduit (46). A spud bit (34) has a flat or
blunt leading end portion (34A) with a discharge opening (34D)
therein to discharge high velocity drilling fluid into the
formation at a location offset from the longitudinal axis of the
drill string (10) to assist in guiding the drill string (10). An
in-hole hydraulic motor (70) is provided in an embodiment (FIG. 7)
for rotating the drill bit (78), and the longitudinal axis of a
drive shaft (74) for the drill bit (78) is offset from the
longitudinal axis of the drill pipe string (10) to assist in a
deviation of the drill bit (78).
Inventors: |
Cherrington; Martin D. (Fair
Oaks, CA), Cherrington; William D. (Citrus Heights, CA) |
Assignee: |
Cherrington Corporation
(Sacramento, CA)
|
Family
ID: |
27010746 |
Appl.
No.: |
07/384,775 |
Filed: |
July 14, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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733723 |
May 14, 1985 |
|
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Reissue of: |
853344 |
Apr 17, 1986 |
04679637 |
Jul 14, 1987 |
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Current U.S.
Class: |
175/61; 175/231;
175/325.2; 175/424; 175/53; 175/67; 175/73 |
Current CPC
Class: |
E21B
7/04 (20130101); E21B 7/06 (20130101); E21B
7/065 (20130101); E21B 7/068 (20130101); G06F
8/313 (20130101); E21B 7/28 (20130101); E21B
10/60 (20130101); E21B 17/00 (20130101); E21B
17/04 (20130101); E21B 7/18 (20130101) |
Current International
Class: |
E21B
7/00 (20060101); E21B 7/04 (20060101); E21B
7/06 (20060101); E21B 7/28 (20060101); E21B
17/04 (20060101); E21B 17/00 (20060101); E21B
7/18 (20060101); E21B 17/02 (20060101); E21B
10/00 (20060101); E21B 10/60 (20060101); G06F
9/44 (20060101); E21B 007/04 (); E21B 007/08 () |
Field of
Search: |
;175/19,21,22,53,61,67,73,107,162,203,231,320,325,350,406,424
;405/184 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Article "Pipeline Digest", Sep. 18, 1978, pp. 8 and 9. .
Pet. Ext. Serv./Univ. Texas, 1969, "Controlled Directional
Drilling", Unit III, Lesson I, (pp. I-19-I-24). .
Article--Oil & Gas Journal/10-1-84, "Directional Drilling
Technique is Proposed for Installing Marine Pipelines in Arctic
Areas". .
Reynolds Metals Co.--Table I--Properties-Reynolds Aluminum &
Steel Drill Pipe (pp. 6-7)/Table 3-Reynolds Aluminum Drill Pipe
41/2' (pp. 10-11)/Table 6-Reed Alstan Tool Joints/Reynolds Aluminum
Drill Pipe..
|
Primary Examiner: Neuder; William P.
Attorney, Agent or Firm: Vinson & Elkins
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
733,723, filed May 14, 1985 now abd.
Claims
What is claimed is:
1. A method for drilling an arcuate underground pilot bore hole
along a predetermined arcuate path in one direction of travel
between two surface locations, and then enlarging the pilot bore
hole in an opposite direction of travel between the surface
locations to receive a production conduit therein, the bore hole
being drilled by a drill pipe string of connected pipe sections
including a leading drill pipe section of a smaller diameter than
the diameter of at least the majority of the remaining pipe
sections, said method comprising the steps of:
advancing the small diameter leading drill pipe section with a
drill bit thereon in one direction of travel along the arcuate path
from a surface entry location to a surface exit location;
removing the small diameter leading drill pipe section from the
drill pipe string after exit from the exit location;
attaching a reamer and production conduit connected thereto to the
drill string at the exit location after the small diameter leading
pipe section has been removed;
pulling the drill string, reamer, and production conduit along the
pilot bore hole from the exit location to the earth entry location
in an opposite direction of travel with the reamer forming an
enlarged opening to receive the production conduit;
rotating said drill string and reamer during pulling thereof;
and
circulating drilling fluid through said drill string during the
drilling and reaming operations.
2. A method for drilling an arcuate underground pilot bore hole
along a predetermined arcuate path in one direction of travel
between two surface locations defining an entrance and an exit, and
then enlarging the pilot bore hole in an opposite direction of
travel between the surface locations to receive a production
conduit therein, the bore hole being drilled by a drill pipe string
of connected pipe sections including a leading drill pipe section
of a strength less than the strength of at least the majority of
the remaining pipe sections; said method comprising the steps
of:
providing thrusting means at the surface entrance location to
advance the drill string and small diameter leading drill pipe
section with a drill bit thereon in one direction of travel along
the arcuate path;
circulating drilling fluid through said drill string during the
drilling operation;
removing the small diameter leading drill pipe section from the
drill pipe string after exit from the exit location;
attaching a reamer and production conduit connected thereto to the
drill string at the exit location after the small diameter leading
pipe section has been removed;
pulling the drill string, reamer, and production conduit along the
pilot bore hole from the exit location to the entry location in an
opposite direction of travel with the reamer forming an enlarged
opening to receive the production conduit;
rotating said drill string and reamer during pulling thereof;
and
circulating drilling fluid through said drill string during the
reaming operation.
3. A method of drilling an arcuate underground pilot bore hole
along a predetermined path between two spaced surface locations
utilizing a spud bit on a leading drill pipe section of a drill
string with a discharge nozzle in a leading planar front face of
the bit directly adjacent the formation to be excavated and eroded;
said method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with the nozzle in said planar face positioned
directly adjacent the formation to be excavated from a surface
entry location to a surface exit location;
and discharging drilling fluid from said nozzle in a jet parallel
to but offset from the longitudinal axis of said drill pipe section
to aid in guiding the drill pipe section along the predetermined
path.
4. The method of drilling an arcuate underground pilot bore hole as
set forth in claim 3 and further including the step of providing a
predetermined partial rotation of said leading drill pipe section
and said spud bit thereby to change the direction of offset and the
deviation of the leading drill pipe section.
5. A method of drilling an arcuate underground pilot bore hole
along a predetermined path between two spaced surface locations
utilizing a spud bit on a leading drill pipe section of a drill
string with discharge nozzle means in a leading front face of the
bit directly adjacent to the formation to be excavated and eroded;
said method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with said nozzle means in said front face
positioned directly adjacent the formation to be excavated from a
surface entrance location to the surface exit location;
discharging drilling fluid from said nozzle means in a jet with the
center of the drilling fluid jet being discharged offset from the
longitudinal axis of the leading pipe section to aid in guiding the
pipe string along the predetermined arcuate path; and
providing a predetermined partial rotation of the leading drill
pipe section and the spud bit thereby to change the direction of
offset of said nozzle means and the deviation of the leading pipe
section.
6. A method of drilling an arcuate underground pilot bore hole
along a predetermined path between two spaced surface locations
utilizing a spud bit on a leading drill pipe section of a drill
string with discharge nozzle means in a leading front face of the
bit directly adjacent to the formation to be excavated and eroded;
said method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with said nozzle means in said front face
positioned directly adjacent the formation to be excavated from a
surface entrance location to a surface exit location;
discharging drilling fluid from said nozzle means in a jet with the
center of the drilling fluid jet being discharged offset from the
longitudinal axis of the leading pipe section to aid in guiding the
pipe string along the predetermined arcuate path;
providing a predetermined partial rotation of the leading drill
pipe section and the spud bit thereby to change the direction of
offset of said nozzle means and the deviation of the leading pipe
section;
providing thrusting means at the surface entrance location to
advance the drill string and spud bit thereon in a direction of
travel along the arcuate path from an entrance opening to an exit
opening;
attaching a reamer to the drill string at the exit location;
pulling the drill string and reamer back through the pilot bore
hole from the exit opening to the entrance opening in an opposite
direction of travel with the reamer forming an enlarged
opening;
pushing the reamer back through the reamed hole from said entrance
opening to said exit opening;
connecting the production conduit to the reamer said exit opening;
and
then pulling the reamer and production conduit back through the
reamed opening from said exit opening to said entrance opening for
installing the production conduit within the enlarged reamed
hole.
7. A method of boring an arcuate underground pilot bore hole along
a predetermined path between two spaced surface locations in a
single boring operation of a single constant diameter utilizing a
drill bit on a leading drill pipe section of a lightweight drill
string formed of a flexible high strength non-magnetic alloy
material; said method comprising the steps of:
advancing the drill string having the drill bit thereon from a
surface entrance location to a surface exit location to form a
pilot bore hole of a single constant diameter;
providing means on said drill bit to permit a predetermined
deviation of the leading pipe section upon a partial rotation of
the leading pipe section a predetermined amount;
discharging drilling fluid from said leading drill pipe section
during the boring operation;
removing the drill bit from the drill string at the surface exit
location;
attaching a reamer to the drill string at the exit location;
pulling the drill string and reamer back through the pilot bore
hole from the exit opening to the entrance opening in an opposite
direction of travel while rotating said reamer with the reamer
forming an enlarged opening;
pushing the reamer back through the reamed hole from said entrance
opening to said exit opening;
connecting the production conduit to the reamer at said exit
opening to permit rotation of the reamer relative to the production
conduit;
then pulling the reamer and production conduit back through the
reamed opening from said exit opening to said entrance opening for
installing the production conduit within the enlarged reamed hole;
and
rotating said drill string and reamer relative to the production
conduit during pulling of the reamer and production conduit.
8. A method for drilling an arcuate underground pilot bore hole
along a predetermined arcuate path in one direction of travel
between two surface locations defining an entrance and an exit in a
single drilling operation of a single constant diameter, and then
enlarging the pilot bore hole in an opposite direction of travel
between the surface locations to receive a production conduit
therein, the bore hole being drilled by a drill pipe string of
connected pipe sections having leading end sections formed of high
strength non-magnetic material and having an outer diameter of at
least around three inches, said drill pipe string including a
leading drill pipe section, electrical survey equipment within the
leading pipe section, and a drill bit on the end of the leading
pipe section; said method comprising the steps of:
providing thrusting means at the surface entrance location to
advance the drill string and leading end section in one direction
of travel along the arcuate path;
providing means on said drill bit to permit a predetermined
deviation of the leading pipe section upon a partial rotation of
the leading pipe section a predetermined amount;
circulating drilling fluid through said drill string during the
drilling operation;
removing the drill bit from the drill pipe string after exit from
the exit location;
attaching a reamer to the drill string at the exit location after
the drill bit has been removed;
pulling and simultaneously rotating the drill string and reamer
along the pilot bore hole from the exit location to the entry
location in an opposite direction of travel with the reamer forming
an enlarged opening adapted to receive a production conduit;
and
circulating drilling fluid through said drill string during the
reaming operation.
9. A method of drilling an arcuate underground pilot bore hole
along a predetermined arcuate path in one direction of travel
between two spaced surface locations in a single drilling operation
of a single constant diameter, and then enlarging the pilot bore
hole in an opposite direction of travel between the surface
locations to receive a production conduit therein, the bore hole
being drilled by a drill pipe string of connected pipe sections
formed by high strength non-magnetic material, said drill pipe
string including a leading drill pipe section, electrical survey
equipment within the leading pipe section, a drill bit on the end
of the leading pipe section, and an in-hole hydraulic motor having
a longitudinal axis offset from the longitudinal axis of the drill
pipe string for rotating the drill bit; said method comprising the
steps of:
advancing the leading drill pipe section carrying the drill bit and
in-hole hydraulic motor along the arcuate path from a surface entry
location to a surface exit location;
providing a drive shaft between the drill bit and in-hole hydraulic
motor for rotating the drill bit along the arcuate path between the
two surface locations;
providing a predetermined deviation of the leading pipe section
upon a partial rotation of the leading drill pipe section and
in-hole motor a predetermined amount;
circulating drill fluid through the drill string to the hydraulic
motor and drill bit for driving the hydraulic motor and providing
drilling fluid for the drilling operation;
removing the leading pipe sections with the drill bit and in-hole
hydraulic motor from the drill string after exit from the surface
exit location;
attaching a reamer to the drill string at the exit location after
removal of the leading pipe section; and
pulling and simultaneously rotating the drill string and reamer
along the pilot bore hole from the exit location to the entry
location in an opposite direction of travel with the reamer forming
an enlarged opening adapted to receive a production conduit.
10. A method of drilling an arcuate underground pilot bore hole
along a predetermined path between two spaced surface locations
utilizing a spud bit on a leading drill pipe section of a drill
string with discharge nozzle means in a leading front face of the
bit directly adjacent to the formation to be excavated and eroded;
said method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with said nozzle means in said front face
positioned directly adjacent the formation to be excavated from a
surface entrance location to a surface exit location;
discharging drilling fluid from said nozzle means in a jet with the
center of the drilling fluid jet being discharged offset from the
longitudinal axis of the leading pipe section to aid in guiding the
pipe string along the predetermined arcuate path;
providing a predetermined partial rotation of the leading drill
pipe section and the spud bit thereby to change the direction of
offset of said nozzle means and the deviation of the leading pipe
section;
providing thrusting means at the surface entrance location to
advance the drill string and spud bit thereon in a direction of
travel along the arcuate path from an entrance opening to an exit
opening;
attaching a production conduit to the drill string at the exit
location; and
pulling the drill string and production conduit back through the
bore hole from the exit opening to the entrance opening in an
opposite direction of travel.
11. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
earth surface locations; said apparatus comprising:
a drill pipe string including a plurality of connected pipe
sections extending from one surface location into a bore entrance
opening of the pilot bore hole;
means at said one surface location to apply a thrust on said pipe
string;
said drill pipe string having a leading pipe section with a drill
bit thereon and being of a flexibility greater than the other pipe
sections; and,
means to circulate drilling fluid during the drilling
operation.
12. Apparatus as set forth in claim 11 wherein the increased
flexibility of said leading pipe section is achieved by said
leading pipe section being of a diameter less than the other pipe
sections.
13. Apparatus as set forth in claim 12 wherein a cross-over sub
connects the leading pipe section with the adjacent pipe
section.
14. Apparatus as set forth in claim 12 wherein both the leading
pipe section and the immediately adjacent pipe section have a
diameter less than the remainder of the pipe sections thereby to
form a relatively long length flexible end for the drill
string.
15. Apparatus as set forth in claim 12 wherein the diameter of the
leading pipe section is less than around three (3) inches and the
diameter of the regular drill pipe sections is more than around
three (3) inches.
16. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel while simultaneously placing a production conduit
therein; said apparatus comprising:
a drill pipe string including a plurality of threaded connected
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, said string including pipe
sections of different strengths and a leading pipe section with a
drill bit thereon;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface locations;
means to circulate drilling fluid through said drill string during
the drilling operation;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is drilled between said spaced
surface locations to form an enlarged opening along the pilot bore
hole;
a production conduit connected to said reamer and following said
reamer through the enlarged opening formed by the reamer;
said means at said one surface location including means for pulling
said drill string, said reamer, and said production conduit along
the enlarged opening in an opposite direction of travel, said
pulling means at said one surface location rotating said drill
string and reamer simultaneously with the pulling action; and
said means to circulate drilling fluid providing drilling fluid for
said reamer during the reaming operation.
17. Apparatus as set forth in claim 16 wherein said pipe sections
adjacent said means applying a thrust are of a greater strength
than the pipe search at the leading end of said pipe string.
18. Apparatus as set forth in claim 16 wherein the drill bit on
said leading pipe section comprises a spud bit.
19. Apparatus as set forth in claim 16 wherein a swivel connects
said reamer and said production conduit to each other to permit
relative rotation therebetween.
20. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
earth surface locations; said apparatus comprising:
a drill pipe string including a plurality of connected pipe
sections extending from one surface location into a bore entrance
opening of the pilot bore hole;
means at said one surface location to apply a thrust on said pipe
string;
said drill pipe string having a leading pipe section with a drill
bit thereon and being of a strength less than the pipe sections
adjacent said means to apply a thrust; and
means to circulate drilling fluid through said drill pipe during
the drilling operation.
21. Apparatus as set forth in claim 20 wherein said leading pipe
section is of a smaller diameter than the diameter of the pipe
sections adjacent said means to apply a thrust.
22. Apparatus as set forth in claim 20 wherein said leading pipe
section is of the same diameter as the remaining pipe sections but
has a decreased wall thickness.
23. Apparatus as set forth in claim 20 wherein said leading pipe
section is of the same diameter as the remaining pipe sections but
formed of a more flexible high strength material than at least the
majority of the remaining pipe sections.
24. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel while simultaneously placing a production conduit
therein; said apparatus comprising:
a drill pipe string including a plurality of threaded connected
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, said string including pipe
sections of different strengths and a leading pipe section with a
drill bit thereon;
at least some of the leading pipe sections being of a reduced
strength relative to at least some of the trailing pipe sections,
and at least some of the leading pipe sections being of an
increased flexibility relatively to at least some of the trailing
pipe sections;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the drilling operation;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is drilled between said spaced
surface locations to form an enlarged opening along the pilot bore
hole;
a production conduit connected to said reamer and following said
reamer through the enlarged opening formed by the reamer;
said means at said one surface location including means for pulling
said drill string, said reamer, and said production conduit along
the enlarged opening in an opposite direction of travel, said
pulling means at said one surface location rotating said drill
string and reamer simultaneously with the pulling action; and
means operatively connecting the production conduit to the
reamer;
said means to circulate drilling fluid providing drilling fluid for
said reamer during the reaming operation.
25. Apparatus as set forth in claim 24 wherein the majority of the
pipe sections in said pipe string have a diameter over around three
(3) inches.
26. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel while simultaneously placing a production conduit
therein; said apparatus comprising:
a drill pipe string including a plurality of threaded connected
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, said string including pipe
sections of different strengths and a leading pipe section with a
spud bit thereon;
said spud bit having a planar forward end portion forming a flat
front face thereof, said flat face having a discharge opening for
receiving and discharging high velocity drilling fluid directly
into the adjacent formation, and an intermediate planar portion
slanting rearwardly from said front face for riding along the
surface of the bore hole;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the drilling operation;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is drilled between said spaced
surface locations to form an enlarged opening along the pilot bore
hole; and
a production conduit connected to said reamer and following said
reamer through the enlarged opening formed by the reamer;
said means at said one surface location including means for pulling
said drill string, said reamer, and said production conduit along
the enlarged opening in an opposite direction of travel, said
pulling means at said one surface location rotating said drill
string and reamer simultaneously with the pulling action;
said means to circulate drilling fluid providing drilling fluid for
said reamer during the reaming operation.
27. Apparatus for drilling a pilot bore hole as set forth in claim
21 wherein an arcuate shoe is secured to the outer periphery of the
leading pipe section adjacent said spud bit for riding along a
surface of the bore hole.
28. Apparatus for drilling a pilot bore hole as set forth in claim
27 wherein said spud bit has a lower planar shoulder adjacent said
arcuate shoe for riding along a surface of the bore hole.
29. Apparatus for drilling a pilot bore hole along a predetermined
underground arcuate path between two spaced surface locations
comprising:
a drill pipe string including a plurality of connected drill pipe
sections extending from one surface location into a bore entrance
opening of the pilot bore hole and having a leading pipe
section;
means at said one surface location to apply an axial thrust to said
pipe string;
means to circulate drilling fluid through said drill pipe string
during the drilling operation; and
a spud bit on the leading pipe section of said pipe string having a
leading end face thereon and fluid discharge nozzle means on said
end face for discharging drilling fluid in a jet offset from the
longitudinal axis of said leading pipe section to aid in guiding
the pipe string along the predetermined arcuate path, said leading
drill pipe section and said spud bit adapted to be partially
rotated a predetermined amount to change the deviation of offset of
said nozzle means and the deviation of the leading drill pipe
section.
30. Apparatus for drilling a pilot bore hole as set forth in claim
29 wherein an arcuate shoe is secured to the outer periphery of the
leading pipe section adjacent said spud bit for riding along the
surface of the bore hole opposite the desired direction of
deviation.
31. Apparatus for drilling a pilot bore hole as set forth in claim
29 wherein said spud bit has a lower planar shoulder adjacent said
arcuate shoe for riding along the surface of the bore hole opposite
the desired direction of deviation.
32. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel for receiving a production conduit therein; said
apparatus comprising:
a drill pipe string including a plurality of connected threaded
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, the drill pipe string
including a leading pipe section having a spud bit with a leading
front face thereon;
fluid discharge nozzle means on said front face for discharging
drilling fluid in a jet having its center offset from the
longitudinal axis of said leading pipe section to aid in guiding
the pipe string along the predetermined arcuate path, said leading
drill pipe section and said spud bit adapted to be partially
rotated in a predetermined amount to change the directional offset
of said nozzle means and the deviation of the leading drill pipe
section;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the drilling operation;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is drilled between said spaced
surface locations and after removal of the spud bit from the drill
string;
said means at said one surface location including means for pulling
said drill string and said reamer along the pilot bore hole in the
opposite direction of travel to form an enlarged opening for
receiving a production conduit, said pulling means rotating said
drill string and reamer simultaneously with the pulling action.
33. Apparatus for drilling an arcuate underground pilot bore hole
as set forth in claim 32 wherein the leading front face of said
spud bit is a planar face extending in a plane generally
transversely of the longitudinal axis of the drill string and
having a plurality of discharge nozzles therein for discharging
drilling fluid in streams directly against the formation, the
center of the mass of discharged fluid being offset from the
longitudinal axis of the drill string.
34. Apparatus for drilling an arcuate underground pilot bore hole
as set forth in claim 32 wherein the leading front face of said
spud bit is a planar face extending in a plane generally
transversely of the longitudinal axis of the drill string, and said
spud bit has an inclined planar lower surface extending from said
planar front face and adapted to ride along the lower surface of
the pilot bore hole.
35. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
earth surface locations; said apparatus comprising:
a lightweight drill pipe string including a plurality of connected
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, each pipe section being of
a high strength flexible non-ferrous alloy sufficient to permit a
deflection of around five (5) degrees;
means at said one surface location to apply an axial thrust to said
pipe string;
a spud bit on the leading pipe section of said drill pipe string
having a leading front face thereon and forming said pilot bore
hole of a single constant diameter, said front face having a
discharge opening for receiving and discharging high velocity
drilling fluid directly into the adjacent formation;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force the pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means associated with said spud bit for changing the deviation of
the leading drill pipe section upon a partial rotation of said spud
bit and leading drill pipe section a predetermined amount;
means to circulate drilling fluid through said drill string during
the drilling operation to provide drilling fluid through the fluid
discharge opening in said spud bit; and
a reamer connected to the drill string at the other surface
location after the pilot bore hole of a single constant diameter is
drilled between said spaced surface locations;
said means at said one surface location including means for pulling
said drill string and said reamer in an opposite direction of
travel along the pilot bore hole from said exit opening to said
entrance opening to enlarge the pilot bore hole for receiving a
production conduit, said means to circulate drilling fluid
providing drilling fluid for said reamer during the reaming
operation.
36. Apparatus as set forth in claim 35 wherein means at said one
surface location applying a thrust on said drill string in said one
direction of travel is utilized to push said reamer back through
the reamed hole from said entrance opening to said exit
opening;
means at said exit opening to connect the production conduit to
said reamer;
said pulling means then pulling said reamer and said production
conduit connected to said reamer from said exit opening back
through the enlarged opening formed by the reamer thereby to
install production conduit in the reamed hole after it has been
completely reamed with all obstructions removed before the
production conduit is initially positioned within the enlarged
opening.
37. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined arcuate path between two spaced earth surface
locations; said apparatus comprising:
a lightweight drill pipe string including a plurality of connected
drill pipe sections extending from one surface location into a bore
entrance opening of the pilot bore, each drill pipe section being
formed of a high strength aluminum alloy material and being of a
flexibility to permit a deflection of around five (5) degrees;
a separate high strength steel tool joint threaded onto each end of
the aluminum drill pipe sections to form a male end on one end of
the drill pipe section and a mating female end on the other end of
the drill pipe section, the steel tool joints on adjacent aluminum
drill pipe sections being threadedly connected to each other to
form a high strength steel connection between adjacent aluminum
drill pipe sections;
a drilling bit on the leading end of the drill string for forming
the pilot bore hole of a single constant diameter along the arcuate
path from said bore entrance opening to a bore exit opening;
a reamer connected to the drill string at the bore exit opening
after the single diameter pilot bore hole is drilled between said
spaced surface locations for enlarging the pilot bore hole; and
means at said one surface location providing power for driving said
drilling bit between said entrance opening and said exit opening,
and for driving said reamer between said exit opening and said
entrance opening to enlarge the pilot bore hole for receiving a
production conduit.
38. Apparatus for drilling an arcuate underground pilot bore hole
as set forth in claim 37 wherein said drilling bit is a spud bit
and said means for driving said drilling bit pushes said spud bit
along the arcuate path in a thrust action.
39. Apparatus for drilling an arcuate underground pilot bore hole
as set forth in claim 37 wherein said drill pipe sections have an
inner diameter over around three (3) inches and an outer diameter
over around four (4) inches.
40. Apparatus for boring an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel in a single boring
operation of a single constant diameter, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel for receiving a production conduit therein; said
apparatus comprising:
a lightweight drill pipe string including a plurality of threaded
connected pipe sections having a diameter of at least around three
(3) inches and extending from one surface location into a bore
entrance opening of the pilot bore hole, said string being formed
of a flexible high strength, non-ferrous material and including a
leading pipe section having electrical survey equipment therein and
a drill bit thereon;
means associated with said bit for changing the deviation of the
leading drill pipe section upon a partial rotation of the drill bit
and leading pipe section a predetermined amount;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the boring operation;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is bored between said spaced
locations to form an enlarged opening along the pilot bore
hole;
a production conduit at said other surface location adapted to be
connected to said reamer and to follow said reamer through the
enlarged opening formed by the reamer;
said means at said one surface location including means for pulling
said drill string, said reamer, and said production conduit along
the enlarged opening in an opposite direction of travel, said
pulling means at said one surface location rotating said drill
string and reamer simultaneously with the pulling action; and
said means to circulate drilling fluid providing drilling fluid for
said reamer during the reaming operation.
41. Apparatus as set forth in claim 40 wherein the drill bit on
said leading pipe section comprises a spud bit.
42. Apparatus as set forth in claim 40 wherein a swivel connects
said reamer and said production conduit to each other to permit
relative rotation therebetween.
43. Apparatus as set forth in claim 40 wherein said reamer
simultaneously forms said enlarged opening along the pilot bore
hole and pulls said production conduit within the enlarged
opening.
44. Apparatus as set forth in claim 40 wherein said reamer forms
said enlarged opening in a first travel pass along the pilot bore
hole and then pulls said production conduit within the enlarged
opening in a second travel pass along the enlarged opening.
45. Apparatus as set forth in claim 40 wherein the drill bit on
said leading pipe section is a rotary drill bit.
46. Apparatus as set forth in claim 45 wherein said leading pipe
section includes an in-hole hydraulic motor for rotating said
rotary drill bit.
47. Apparatus for boring an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel in a single boring
operation of a single constant diameter, and then reaming an
enlarged opening along the pilot bore hole in an opposite direction
of travel for receiving a production conduit therein; said
apparatus comprising:
a lightweight drill pipe string including a plurality of threaded
connected pipe sections extending from one surface location into a
bore entrance opening of the pilot bore hole, at least the leading
pipe section being formed of a high strength non-magnetic flexible
alloy material to permit a deflection of at least around five (5)
degrees and having a diameter of at least around three (3) inches,
and electronic survey equipment within the leading pipe
section;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
a reamer connected to said drill string at the other surface
location after the pilot bore hole is bored between said spaced
surface locations to form an enlarged opening along the pilot bore
hole;
a production conduit at said other surface location adapted to be
connected to said reamer and to follow said reamer through the
enlarged opening formed by the reamer;
said means at said one surface location including means for pulling
said drill string, said reamer, and said production conduit along
the enlarged opening in an opposite direction of travel, said
pulling means at said one surface location rotating said drill
string and reamer simultaneously with the pulling action; and
means to circulate drilling fluid through said drill string during
the boring and reaming operations.
48. Apparatus as set forth in claim 47 wherein means at said one
surface location applying a thrust on said drill string in said one
direction of travel is utilized to push said reamer back through
the reamed hole from said entrance opening to said exit
opening;
said pulling means then pulling said reamer and said production
conduit connected to said reamer from said exit opening back
through the enlarged opening formed by the reamer thereby to
install production conduit in the reamed hole after it has been
completely reamed with all obstructions removed before the
production conduit is initially positioned within the enlarged
opening.
49. Apparatus for drilling an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaced
surface locations in one direction of travel, and then pulling a
production conduit along the bore hole in an opposite direction of
travel; said apparatus comprising:
a drill pipe string including a plurality of connected threaded
pipe sections extending from one surface location into a bore
entrance opening of the pilot bore hole, the drill pipe string
including a leading pipe section having a spud bit with a leading
front face thereon;
fluid discharge nozzle means on said front face for discharging
drilling fluid in a jet having its center offset from the
longitudinal axis of said leading pipe section to aid in guiding
the pipe string along the predetermined arcuate path, said leading
drill pipe section and said spud bit adapted to be partially
rotated in a predetermined amount to change the directional offset
of said nozzle means and the deviation of the leading drill pipe
section;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the drilling operation; and
a production conduit connected to said drill string at the other
surface location after the pilot bore hole is drilled between said
spaced surface locations and after removal of the spud bit from the
drill string;
said means at said one surface location including means for pulling
said drill string and said production conduit through the bore hole
in the opposite direction of travel.
50. Apparatus for boring an arcuate underground pilot bore hole
along a predetermined inverted arcuate path between two spaved
surface locations in one direction of travel in a single boring
operation of a single constant diameter, and then pulling a
production conduit along the bore hole in an opposite direction of
travel; said apparatus comprising:
a lightweight drill pipe string including a plurality of threaded
connected pipe sections having a diameter of at least around three
(3) inches and extending from one surface location into a bore
entrance opening of the pilot bore hole, said string being formed
of a flexible high strength, non-ferrous material and including a
leading pipe section having electrical survey equipment therein and
a drill bit thereon;
means associated with said bit for changing the deviation of the
leading drill pipe section upon a partial rotation of the drill bit
and leading pipe section a predetermined amount;
means at said one surface location applying a thrust on said pipe
string in said one direction of travel to force said pipe string in
a thrust action along the arcuate path in said one direction of
travel to an exit opening at the other surface location;
means to circulate drilling fluid through said drill string during
the boring operation; and
a production conduit at said other surface location connected to
said drill string after removal of said drill bit;
said means at said one surface location including means for pulling
said drill string, and said production conduit along the bore hole
in an opposite direction of travel. .Iadd.
51. A method of drilling an arcuate underground bore hole between
two spaced surface locations utilizing a spud bit on a leading
drill pipe section of a drill string with a discharge nozzle in the
bit directly adjacent the formation to be excavated and eroded,
said method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with the nozzle in said bit positioned
directly adjacent the formation to be excavated from a surface
entry location to a surface exit location;
and discharging drilling fluid from said nozzle in a jet parallel
to but offset from the longitudinal axis of said drill pipe section
to aid in guiding the drill pipe section. .Iaddend. .Iadd.52. The
method of drilling an arcuate underground bore hole as set forth in
claim 51 wherein said spud bit has a planar end portion inclined
rearwardly from a forward portion of said bit to form a ramp.
.Iaddend. .Iadd.53. The method of drilling an arcuate underground
bore hole as set forth in claim 52 wherein said forward portion is
a flat end portion and said inclined planar end portion extends
rearwardly from said flat forward end portion to form said ramp.
.Iaddend. .Iadd.54. The method of drilling an arcuate underground
bore hole as set forth in claim 53 wherein said spud bit has a
lower planar shoulder for riding along the surface of the bore
hole. .Iaddend. .Iadd.55. The method of drilling an arcuate
underground bore hole as set forth in claim 54 wherein said
inclined planar end portion forms said ramp by extending rearwardly
from said flat forward end portion to said lower
planar shoulder. .Iaddend. .Iadd.56. The method of drilling an
arcuate underground bore hole as set forth in claim 55 wherein an
arcuate shoe is secured to the leading pipe section adjacent said
spud bit for riding along the surface of the bore hole. .Iaddend.
.Iadd.57. The method of drilling an arcuate underground bore hole
as set forth in claim 56 wherein said arcuate shoe is adjacent said
lower planar shoulder. .Iaddend. .Iadd.58. The method of drilling
an arcuate underground bore hole as set forth in claim 51 and
further including the step of rotating said leading drill pipe
section and said spud bit thereby to change the direction of
leading drill pipe section. .Iaddend. .Iadd.59. A method of
drilling an arcuate underground bore hole between two spaced
surface locations utilizing a spud bit on a leading drill pipe
section of a drill string with discharge nozzle means in the bit
directly adjacent to the formation to be excavated and eroded, said
method comprising the steps of:
advancing the leading drill pipe section of the drill string having
the spud bit thereon with said nozzle means in said bit positioned
directly adjacent the formation to be excavated from a surface
entrance location to a surface exit location;
discharging drilling fluid from said nozzle means in a jet with the
center of the drilling fluid jet being discharged from a position
offset from the longitudinal axis of the leading pipe section to
aid in guiding the pipe string along the desired arcuate path;
and
providing a rotation of the leading drill pipe section and the spud
bit thereby to change the direction of offset of said nozzle means
and the deviation of the leading pipe section;
said spud bit having a planar end portion inclined rearwardly from
a forward position of said bit to form a ramp. .Iaddend. .Iadd.60.
The method of drilling an arcuate underground bore hole as set
forth in claim 59 wherein said forward portion is a flat end
portion and said inclined planar end portion extends rearwardly
from said flat forward end portion to form said ramp. .Iaddend.
.Iadd.61. The method of drilling an arcuate underground bore hole
as set forth in claim 60 wherein said spud bit has a lower planar
shoulder for riding along the surface of the bore hole. .Iaddend.
.Iadd.62. The method of drilling an arcuate underground bore hole
as set forth in claim 61 wherein said inclined planar end portion
forms said ramp by extending rearwardly from said flat forward end
portion to said lower planar shoulder. .Iaddend. .Iadd.63. The
method of drilling an arcuate underground bore hole as set forth in
claim 62 wherein an arcuate shoe is secured to the leading pipe
section adjacent said spud bit for riding along the surface of the
bore hole. .Iaddend. .Iadd.64. The method of drilling an arcuate
underground bore hole as set forth in claim 63 wherein said arcuate
shoe is adjacent said lower planar shoulder.
.Iaddend. .Iadd.65. Apparatus for drilling a bore hole along a
underground arcuate path between two spaced surface locations
comprising:
a drill pipe string including a plurality of connected drill pipe
sections extending from one surface location into a bore entrance
opening of the pilot bore hole and having a leading pipe
section;
means at said one surface location to apply an axial thrust to said
pipe string;
means to circulate drilling fluid through said drill pipe string
during the drilling operation; and
a spud bit on the leading pipe section of said pipe string having a
fluid discharge nozzle means for discharging drilling fluid in a
jet parallel to but offset from the longitudinal axis of said
leading pipe section to aid in guiding the pipe string along the
predetermined arcuate path, said leading drill pipe section and
said spud bit adapted to be rotated to control the direction of
said bit. .Iaddend. .Iadd.66. Apparatus for drilling an arcuate
underground bore hole as set forth in claim 65 wherein said spud
bit has a planar end portion inclined rearwardly from a forward
portion of said bit to form a ramp. .Iaddend. .Iadd.67. Apparatus
for drilling an arcuate underground bore hole as set forth in claim
66 wherein said forward portion is a flat end portion and said
inclined planar end portion extends rearwardly from said flat
forward end portion to form said ramp. .Iaddend. .Iadd.68.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 67 wherein said spud bit has a lower planar shoulder
for riding along the surface of the bore hole. .Iaddend. .Iadd.69.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 68 wherein said inclined planar end portion forms
said ramp by extending rearwardly from said flat forward end
portion to said lower planar shoulder. .Iaddend. .Iadd.70.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 69 wherein an arcuate shoe is secured to the leading
pipe section adjacent said spud bit for riding along the surface of
the bore hole. .Iaddend. .Iadd.71. Apparatus for drilling an
arcuate underground bore hole as set forth in claim 70 wherein said
arcuate shoe is adjacent said lower planar shoulder. .Iaddend.
.Iadd.72. Apparatus for drilling a bore hole as set forth in claim
71 wherein an arcuate shoe is secured to the outer periphery of the
leading pipe section adjacent said spud bit for riding along the
surface of the bore hole opposite the desired direction of
deviation. .Iaddend.
.Iadd. Apparatus for drilling a hole underground between two spaced
surface locations comprising:
a drill pipe string including a plurality of connected drill pipe
sections extending from one surface location into a bore entrance
opening of the hole and having a leading pipe section;
means at said one surface location to apply an axial thrust to said
pipe string;
means to circulate drilling fluid through said drill pipe string
during the drilling operation; and
a bit on the leading pipe section of said pipe string having a
leading end face thereon and fluid discharge nozzle means on said
end face for discharging drilling fluid in a jet offset from and
parallel to the longitudinal axis of said leading pipe section to
aid in guiding the pipe-string along a steerable path, said bit
adapted to be rotated in a controlled way to change the direction
of said bit. .Iaddend. .Iadd.74. Apparatus for drilling an arcuate
underground bore hole as set forth in claim 73 wherein said spud
bit has a planar end portion inclined rearwardly from a forward
portion of said bit to form a ramp. .Iaddend. .Iadd.75. Apparatus
for drilling an arcuate underground bore hole as set forth in claim
74 wherein said forward portion is a flat end portion and said
inclined planar end portion extends rearwardly from said flat
forward end portion to form said ramp. .Iaddend. .Iadd.76.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 75 wherein said spud bit has a lower planar shoulder
for riding along the surface of the bore hole. .Iaddend. .Iadd.77.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 76 wherein said inclined planar end portion forms
said ramp by extending rearwardly from said flat forward end
portion to said lower planar shoulder. .Iaddend. .Iadd.78.
Apparatus for drilling an arcuate underground bore hole as set
forth in claim 77 wherein an arcuate shoe is secured to the leading
pipe section adjacent said spud bit for riding along the surface of
the bore hole. .Iaddend. .Iadd.79. Apparatus for drilling an
arcuate underground bore hole as set forth in claim 78 wherein said
arcuate shoe is adjacent said lower planar shoulder. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for
drilling a pilot bore hole along an underground arcuate path
between two surface locations, and then enlarging the pilot bore
hole for installing a conduit therein, such as pipe, casing, cable,
or a pipeline.
Heretofore, directional drilling apparatus has been provided for
drilling an underground pilot bore hole along an arcuate path
between two surface locations, and then enlarging the pilot bore
hole for receiving a product conduit, such as a pipeline therein. A
common apparatus and method has utilized a drill pipe string of
relatively small diameter less than two (2) inches with a drill bit
thereon forming a relatively small diameter pilot bore hole, which
is followed by a relatively large diameter washover pipe such as
around five (5) inches in diameter or more, in concentric relation
to the drill string and having cutting blades on the leading end
thereof for enlarging the initial pilot bore hole. Upon completion
of the pilot bore hole as enlarged by the washover pipe, the drill
string has been removed and the washover string then connected to a
reamer at the exit end for pulling the reamer and connected product
conduit along the initial bore hole for reaming to a desired
diameter to receive the product conduit.
Thus, the method and apparatus employed heretofore for forming a
pilot bore hole normally has included two separate cutting or
drilling steps prior to the reaming operation, the first cutting
step being the drilling of a small diameter bore hole from a drill
bit with a relatively small diameter light weight drill string, and
the second cutting step resulting from an enlarging of the bore
hole by the washover string in concentric relation to the drill
string. Thereafter, the reaming operation has taken place to
enlarge the pilot bore hole to receive the product conduit or
pipe.
Heretofore, a relatively small diameter drill pipe string of around
one and three-fourths (13/4) inches in diameter has been utilized
for such pilot bore holes as it was found desirable to have a
relatively lightweight drill pipe or string, particularly when
drilling under streams where sand and clays are normally
encountered with water also being present at times. Under the
weight of the drill string, the drill string could sink under
certain conditions and it was accepted as common practice in the
industry to employ a relatively small diameter drill string in
order to keep the weight of the entire drill string at a minimum
and to provide flexibility. Such a small diameter drill pipe string
thus necessitated the use of a separate washover string in order to
provide the necessary strength for the subsequent reaming operation
and pulling of the production conduit through the enlarged bore
hole.
The utilization of two separate cutting steps or procedures for
forming the pilot bore hole prior to the reaming operation results
in a costly operation.
Other directional drilling apparatus and methods for underground
arcuate bores or openings not employing a washover pipe following
the drill string have utilized other types of reamers or cutters
which enlarge the initial pilot bore hole by a cutter or reamer
moving in the same direction as the initial drill pipe string
forming the pilot bore hole.
SUMMARY OF THE INVENTION
This invention is directed to an apparatus and method for drilling
in one direction of travel a pilot bore hole along an underground
arcuate path between two earth surface locations, and then
enlarging in an opposite direction of travel the initial pilot bore
hole for receiving a product conduit therein. The apparatus and
method utilized to accomplish this comprise two separate cutting
operations, the first being a pilot bore drilled by a conventional
drill pipe string but utilizing at least for a majority of the
drill pipe sections an increased diameter of around three and
one-half (31/2) inches which increases the strength of the pipe
string as compared with common industry practice heretofore. The
increased strength drill string thus eliminates the necessity of
having a separate washover string as the increased drill string
strength is adequate for the torsional or rotational stresses
developed in the subsequent reaming operation and pulling of the
production conduit through the enlarged bore hole.
The drill string is thrust along a predetermined arcuate path to
form an initial pilot bore hole of a relatively small diameter,
such as around five (5) inches, for example. After the drilling of
the initial pilot bore hole and exit of the drilling string from
the exit surface opening, a reamer and connected production conduit
are attached to the drill string, and the drill string is then
pulled back through the pilot bore hole in an opposite direction of
travel with the reamer enlarging the bore hole to a diameter
sufficient to receive the production conduit therein. The enlarged
opening may be around thirty (30) inches in diameter for a
production conduit, such as a pipeline, around twenty (20) inches
in diameter thereby providing a five (5) inch annulus between the
production conduit and the enlarged opening.
In order to provide the desired flexibility in the leading end pipe
section of the drill string, such as is desirable when relatively
soft formations are encountered, the leading end pipe section
having the drill bit thereon may be provided of a diameter smaller
than the diameter of the regular drill string sections, or a
different wall thickness or different type of material may be
utilized for the leading pipe section to provide the desired
flexibility. Preferably, the drill string sections except for the
leading pipe sections are over around three (3) inches in diameter
and sections of three and one-half (31/2) inches in diameter have
been found satisfactory. The leading drill pipe section of this
invention is preferably below three (3) inches in diameter. Thus,
the leading drill pipe section or sections may be provided with an
increased flexibility and the length of the leading end section may
be varied. Any reduced diameter drill pipe section or sections are
preferably removed at the surface location adjacent the exit
opening prior to the attachment of the reamer and production
conduit to the drill string. Thus, a constant diameter drill string
may be provided for pulling the reamer and following product
conduit through the pilot bore hole in a reverse or opposite
direction of travel.
Under certain conditions it may be desirable, such as for
relatively long arcuate paths, to provide drill pipe sections in
the drill string of an increasing strength from the leading end
thereof to the power means for thrusting the drill bit and/or
rotating the drill string in the reaming operation. The increased
strength pipe sections compensate for the increasing friction of
the drill string along its length. Drill pipe sections having an
increased strength may be provided independently of any increased
flexibility, if desired. In some situations, it may be desirable to
have less flexibility on the leading end drill pipe sections.
Another feature of this invention utilizes an in-hole hydraulic
motor positioned within the leading drill string section for
rotating the drill bit, such as might be desirable where relatively
hard formations are encountered. When a leading pipe section for
the drill bit is provided utilizing the in-hole hydraulic motor,
the longitudinal axis of the drive shaft for rotating the drill bit
is parallel to but offset from the longitudinal axis of the drill
string. This offset results in the deviation or deflection of the
drill bit a predetermined amount in the desired direction of travel
as the leading pipe section rides along the surface of the pilot
bore hole formed by the drill bit opposite the desired direction of
deviation.
In a separate embodiment of this invention, a drill string is
provided consisting of a plurality of connected pipe sections with
each pipe section being formed of a high strength flexible alloy
material, such as aluminum, having an inside diameter of around
four (4) inches. The use of a material such as aluminum which is
non-magnetic or non-ferrous does not affect sensitive monitoring or
surveying equipment which may be positioned within the drill
string, particularly since a relatively large diameter drill pipe
is utilized. A high strength large diameter drill pipe section
permits the use of a relatively large diameter drill bit and also
provides sufficient strength for pulling the reamer and/or
production conduit back through the hole after the pilot hole has
been drilled.
Additionally, it has been found with certain types of formations
that it is advisable to add a separate step to the method or
process for installing the production conduit by first pulling the
reamer back through the drilled pilot hole without the production
conduit. Then, pushing the reamer back through the enlarged empty
hole, and then attaching the production conduit to the reamer for
installation of the production conduit. This method ensures that
the small diameter pilot hole can be enlarged without hitting an
obstruction, and requires less power for pulling the production
conduit through the hole since the reaming operation is
completed.
Another feature of this invention is the use of a spud bit having
fluid discharge nozzle means at its leading end with the center or
longitudinal axis of the fluid stream or jet discharged from the
bit being offset from the longitudinal axis of the drill string for
guiding the drill string. The drill string may also be rotated
through a selected defined angle to aid in guiding the drill
string. In the event more than one discharge nozzle is provided,
the center or longitudinal axis of the mass of drilling fluid being
discharged is offset from the longitudinal axis of the drill string
in the desired travel path.
An object of this invention is to provide an apparatus and method
in which a conventional drill string comprising a plurality of
drill pipe sections is thrust along an arcuate path to the desired
surface exit opening, and then a reamer and production conduit are
pulled, upon connection to the drill string, back through the pilot
bore hole in a minimum of time.
A further object is to provide a drill string for drilling the
pilot bore hole having a leading pipe section with an increased
flexibility for drilling through relatively soft formations, or for
utilizing various lengths of leading drill pipe sections as may be
desired.
Another object is to provide a spud bit on the leading end of the
drill string having fluid discharge nozzle means for discharging
high velocity drilling fluid in a jet or stream having its center
offset from the longitudinal axis of the drill string to guide the
drill string.
Another object is to provide a drill string for drilling the pilot
bore hole having drill pipe sections of increasing strength to
compensate for the increasing friction of the drill string along
the pilot bore hole.
An additional object is to provide in a drill string for drilling
the pilot bore hole an in-hole hydraulic motor for rotating the
drill bit relative to the drill string, and having its rotational
axis parallel but offset from the longitudinal axis of the drill
string to provide a desired deflection or deviation to the drill
bit.
Another object is to provide a spud bit for drilling a bore hole
having a novel shape particularly adapted for use with discharge
nozzles for a high velocity drilling fluid.
Other objects, features, and advantages of this invention will
become more apparent after referring to the following specification
and drawings.
DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective schematic cross-section of the initial
drilling operation in drilling an inverted arcuate pilot hole or
bore from an earth entry opening to an earth exit opening and
utilizing the apparatus and method of the present invention;
FIG. 2 is a perspective schematic cross-section similar to FIG. 1
but showing the enlarging of the initial pilot bore hole by a
reamer and the pulling of the production conduit and reamer
therethrough by the initial drill string;
FIG. 3 is a schematic side elevation, partly in section, of the
entrance end of the pilot bore hole showing the thrust and rotating
device for the drill string;
FIG. 4 is an exploded view of a crossover sub for connecting
adjacent drill string lengths or sections of different
diameters;
FIG. 5 is a schematic side elevation of the leading end of the
drill string showing a deflecting spud bit for forming the initial
pilot bore hole shown in FIG. 1;
FIG. 5A is an end elevation of the spud bit shown in FIG. 5;
FIG. 6 is a schematic side elevation of the end of the drill string
connected to a reamer and production conduit at the exit opening of
the small diameter pilot bore hole for pulling the reamer and
production casing through the enlarged opening formed by the
reamer;
FIG. 7 is a schematic cross-section showing a modified drill bit
arrangement in which an in-hole motor driven by drilling fluid is
utilized, such as may be required for certain types of formations
or bore hole lengths;
FIG. 8 illustrates in side elevation, partly in section, a
plurality of drill pipe sections formed of large diameter aluminum
pipe connected by suitable tool joints;
FIG. 9 is a side elevation of a modified spud bit showing a
plurality of fluid discharge nozzles therein; and
FIG. 10 is a front elevation of the modified spud bit shown in FIG.
9.
Referring now to the drawings for a better understanding of our
invention, reference is made to FIG. 1 in which an arcuate pilot
bore hole is illustrated at B extending along an underground path
shown at P. Path P extends from an earth surface entrance opening O
to an earth surface exit opening E underneath an obstruction shown
as a river R.
While exit opening E is shown as a surface exit opening in the
drawings, the terms "exit opening", "surface exit opening" or
"surface location" as used in the specification and claims shall be
interpreted as including an opening beneath the surface at which a
product conduit is connected to the drill string to be pulled
through the bore hole, such as an underground cable.
A drill string indicated generally at 10 includes a leading end
pipe section 10A of a small diameter, an adjacent end section 10B
of an intermediate diameter, and following pipe sections 10C of
uniform diameter. Drill string 10 is utilized to drill small
diameter pilot bore hole B along path P. A plurality of lengths or
sections of pipe string 10 are normally positioned adjacent
entrance opening O such as shown at 10C in broken lines in FIG.
1.
As pointed out above, drill string pipe sections utilized
heretofore in association with a separate washover pipe string have
been of a diameter around one and three-fourths (13/4) inches since
the washover string was relied upon for rotation of the reamer and
pulling of the production conduit. However, the present invention
eliminates the washover pipe and instead, provides a higher
strength drill pipe string having a diameter of three and one-half
(31/2) inches. Such an increased diameter provides a stiffer pipe
string than used heretofore.
Under certain types of conditions encountered such as relatively
soft formations, it is desirable to have a smaller, more flexible
leading end section on drill string 10 in order to achieve easily
the necessary or desired deflection. As shown in FIG. 1, sections
10C are of the normal or regular diameter of three and one-half
(31/2) inches. However, leading section 10A is formed of a smaller
diameter pipe and is around two and three-quarters (23/4) inches in
diameter, while pipe section 10B is of an intermediate diameter of
two and seven-eighths (27/8) inches. By using a drill string with
two or more graduated diameters, different length pipe sections may
be easily utilized as might be desirable under certain conditions,
and this has been found to be particularly useful where relatively
soft ground conditions are encountered where a smaller, more
flexible leading end pipe section is desirable for obtaining the
desired deflection necessary to follow arcuate path P.
While increased flexibility is obtained by having pipe sections 10A
and 10B of a smaller diameter than sections 10C, it is to be
understood that sections 10A and 10B could, if desired, provide
increased flexibility by other means, such as by being made of a
more flexible high strength material without being of a reduced
diameter, or by having a different wall thickness without any
change in external diameter.
It is also desirable for a relatively long arcuate path P to have
trailing pipe sections of the drill string of a strength greater
than the leading pipe sections. During a thrust action, the drill
string is pushed from the entrance opening O along the bore hole B,
and portions of the length of the drill string are in contact with
the surface of the bore hole B during the pushing action thereby to
generate sliding frictional resistance which has to be overcome.
The greater the length of the drill string, the greater the amount
of sliding friction. Likewise, upon rotation of the drill string
during a reaming action, the torsional or rotational stresses in
the drill string are higher at the power source providing rotation.
Thus, it is desirable to have drill pipe sections adjacent the
power source of an increased strength. It may be desired to have
drill pipe sections of graduated increasing strength from the drill
bit end to the power source. Further, it may not be desirable to
have the diameter of the drill string greater than around three and
one-half (31/2) inches, or to have the leading pipe sections of an
increased flexibility. Under such conditions, the strength of the
drill pipe sections, particularly those sections adjacent the power
means for thrusting the drill bit along a relatively long arcuate
path P, such as over five hundred (500) feet in length, are
preferably of an increased strength. Such increased strength could
be provided, for example, by making the pipe sections of high
strength materials or increasing the wall thickness of such pipe
sections. The utilization of drill pipe sections with different
strengths thereby eliminates the necessity of having a separate
washover pipe following the drill string in concentric relation, as
a specific drill string section can be designed for the specific
strength required at its location in a drill string.
As shown in FIG. 3, an inclined ramp is shown at 12 and has a
hydraulic motor 14 mounted on a carriage 16 for axial movement
along a suitable guideway on ramp 12, such as by a suitable pulley
or cog wheel 18 moving along a taut cable 20, for example. Motor 14
may be used, selectively, to rotate a connecting shaft 22 which is
connected at one end to a joint 24 attached to section 10C of drill
string 10, thereby to rotate drill string 10, if desired. Shaft 22
is connected at its other end to a swivel 26 which is in turn
connected to a hose 28 through which a suitable drilling fluid is
circulated. Carriage 16 reciprocates back and forth as drill pipe
sections are added by making and breaking joint 24.
Drilling mud circulated through hose 28 is supplied to the drill
pipe and out suitable fluid passageways (not shown) at the drill
bit for possible return to a sump shown at 30 adjacent the end of
entrance opening O which receives the drilling fluid and cuttings
from the drilling operation. A suitable hose shown at 32 returns
the drilling fluid or mud for removal of the cuttings, and again
providing drilling fluid to hose 28 as is well known in the
art.
Drill string 10 is standard and normally made up of a plurality of
drill pipe sections which are added to the drill pipe string at
connector 24. The pipe sections are advanced in the earth by
advancing hydraulic motor 14 connected to a suitable source of
hydraulic fluid (not shown) down ramp 12.
Leading small diameter pipe section 10A has a spud bit 34 on its
leading end. Spud bits of various types are well known generally in
the art for directional drilling or the like. However, spud bit 34
as shown in FIGS. 5 and 5A is particularly adapted in the present
invention for discharging a high velocity drilling fluid from its
leading end at a location closely adjacent the formation thereby to
obtain a highly effective excavating action to advance the drill
string. It is important to note that spud bit 34 preferably
discharges fluid in a direction parallel to the axis of the drill
string as shown by the arrows in FIG. 5. For this purpose, spud bit
34 has a flat or planar forward end portion 34A, an inclined
intermediate planar end portion 34B leading from forward end
portion 34A to form a ramp, and a rear planar shoulder 34C. An
arcuate shoe or wear plate 35 is secured to the outer periphery of
pipe section 10A adjacent rear shoulder 34C. It is noted that bore
hole B has a diameter larger than the maximum diameter of any
portion of the drill string moving through the hole.
A discharge opening 34D or discharge nozzle which may be threaded
within end portion 34A to form opening 34D is provided in the face
formed by planar end portion 34A. Thus, opening 34D is positioned
at the leading end of spud bit 34 directly adjacent the formation
to be excavated for discharging a jet of high velocity drilling
fluid therein. The drilling fluid may be pressurized from around
one hundred (100) psi to around two thousand (2000) psi, for
example. The longitudinal or discharge axis of discharge nozzle 34D
is parallel to, but offset from, the longitudinal axis of drill
string 10 to aid in deflecting end section 10A in the direction of
the offset. Discharge opening 34D is of sufficient depth such that
pressurized fluid is preferably discharged therefrom in a direction
parallel to the longitudinal axis of drill string 10 to erode
and/or excavate the formation. It is apparent that end section 10A
may be guided also by rotation of the drill string through a
defined angle. To provide an effective guiding action, the offset
of nozzle or opening 34D, or the offset of the center of the volume
of fluid being discharged in the event more that one discharge
opening is utilized, should be at least greater than around
three-fourths (3/4) inch. As an example, with a spud bit having a
diameter of five (5) inches as shown in FIG. 5A, nozzle 34D is
around three-eighths (3/8) inch in diameter and offset one (1) inch
from the longitudinal center line of section 10A.
It may be desirable under certain conditions to have more than one
discharge nozzle, but in any event, the center of the combined jets
of drilling fluid being discharged is parallel to and preferably
offset from the longitudinal axis of section 10A in the desired
travel path. The ramp formed by inclined planar end portion 34B,
rear shoulder 34C, and shoe 35 ride along the surface of bore hole
B opposite the desired direction of deviation and aid in guiding
pipe section 10A along travel path P. Under certain conditions it
may be desirable to have a ramp to aid in guiding pipe section 10A,
such as ramp 34B, extending across the entire leading end of the
spud bit without any separate planar end portion such as shown at
34A. Spud bit 34 thus moves along path P in a thrusting action
without being rotated except for a predetermined partial rotation
to obtain angular orientation to guide pipe section 10A.
While spud bit 34 has been developed primarily for use in drilling
a pilot bore hole along an arcuate path between two surface
locations, it is obvious that spud bit 34 may be utilized for other
types of directional or downhole drilling as well known in the
art.
Arcuate path P can be controlled or guided without withdrawing of
the drill string from the earth primarily by orientation of spud
bit 34 by a partial rotation of the drill string through a defined
angle, but such control may also be dependent on such factors or
parameters, for example, as the thrust on the drill string and the
volume of drilling mud passed to the drill string, as is well known
in the art. For further details concerning the deviation or
deflection of the drill string for directional drilling or the
like, as well known in the art, reference is made to U.S. Pat. No.
2,646,254 dated July 21, 1953 and U.S. Pat. No. 3,713,500 dated
Jan. 30, 1973, as examples.
For connecting two pipe sections of different diameters, such as
shown in FIG. 4, a crossover sub indicated generally at 36 is
illustrated having a threaded male end 38 adapted to be threaded
within a female end 40 on pipe section 10A, and having a female
connection 42 on an opposite end thereof adapted to receive the
male threaded end 44 of adjacent pipe section 10B. A similar
crossover sub 42 is provided between sections 10B and 10C. The
diameter of bore B is sufficiently larger than the diameter of pipe
string 10 to provide an annulus to permit the discharge of the
drilling fluid and cuttings from bore B. Utilizing a drill pipe
string of a maximum diameter around three and one-half (31/2)
inches, bore B may be around five (5) inches in diameter to provide
adequate clearance for the flow of cuttings and drilling fluid from
bore B.
When leading drill section 10A reaches exit opening E and pilot
bore hole B is completed, it is now necessary to enlarge the pilot
bore hole for receiving the production conduit shown in the
drawings as a pipeline 46. The production conduit may be any of
several types of continuous conduit, such as, for example, casing,
pipe, cables, or the like, and more than one production conduit may
be installed in enlarged opening D. For this purpose, a reamer
indicated generally at 48 is shown in FIG. 6. Reamer 48 has cutting
teeth 50 thereon and is coupled at 52 to the end of the first drill
section 10C of the uniform diameter of three and one-half (31/2)
inches for rotation by drill string 10 and motor 14. The end drill
pipe section 10A, or at least the drill bit and any associated
instrumentation (not shown), is removed for connection of drill
string 10 to reamer 48. It may be desirable to remove both sections
10A and 10B from the end of the drill string 10 prior to the
connection of reamer 48 if it is desired that drill string 10 be of
a uniform diameter and strength for rotating reamer 48 and pulling
production pipe 46 through bore hole B.
Drilling mud continues to be supplied through drill string 10 and
pipe section 10C to the cutting area adjacent reamer 48 where it is
discharged through suitable perforations as is well known. Shaft 54
extends from reamer 48 and has an enlarged diameter end thereof at
56 received within a swivel indicated generally at 50 so that the
reamer 48 can rotate relative to production pipe 46. An equally
satisfactory and effective method and means could be utilized by a
separate threaded sleeve connection between shaft 54 and reamer 48
as shown in FIG. 3 by connector 24. Enlarged end 56 of shaft 54 is
mounted within bearings 58 on opposite sides thereof for
transmitting thrust to swivel 50 and to permit relative rotation
between reamer 48 and production pipe 46. Preferably pipe 46 enters
the bore hole B without any rotation at all through in some
instances it may be desirable to rotate a production conduit being
installed. Swivel body 50 has a clevis defining two spaced arms 60
on the side thereof opposite shaft 54, and an extension 62 on a
sleeve 66 is pivotally connected to arms 60 by pin or bolt 64.
Sleeve 66 is shown in FIG. 6 threaded onto an end of production
pipe 46 which is formed of a plurality of welded sections as common
for pipelines. It is to be understood, however, as well known in
the art, that sleeve 66 could be secured by other means to a
production conduit, such as, for example, by welding, bolted
connection, or other types of threaded connections. Reamer 48 is of
a diameter larger than a diameter of production casing 46 so as to
form a suitable annulus 68 in the enlarged diameter opening D. For
example, if production casing or pipe 46 is of a diameter of twenty
(20) inches, reamer 48 may be of a thirty (30) inch diameter to
provide a five (5) inch annulus 68 about the periphery of pipe 46.
Annulus 68 may be utilized for cementing of conduit 46 in
position.
After pipe 46 has been pulled through the enlarged opening D from
surface location at opening O, sleeve 66 is removed from production
casing 46 and production casing 46 may be cemented or secured in
position.
Referring to FIG. 7, a modified form of end section is shown at 10D
for an in-hole motor 70 which is used where relatively hard
formations may be encountered. In-hole motor shown at 70 is
positioned within an enlarged diameter end portion 71 of drill
string section 10D and is a hydraulic motor driven by drilling
fluid received by the drill string. The longitudinal axis of the
drill string is shown along line 72 while the longitudinal axis of
the rotating drill bit shaft 74 is shown at 76. A drill bit 78 is
connected to the end of shaft 74 for rotation therewith. While
hydraulic motor 70 is shown schematically in FIG. 7 as being
separate and larger that shaft 74, it is to be understood, as well
known in the art, that motor 70 and shaft 74 may be combined and of
a single continuous diameter such as illustrated schematically by
shaft 74.
It is noted that axis 76 is offset from but parallel to axis 72 to
aid in deflecting end section 10D a predetermined amount in the
desired direction of travel. While axis 76 is shown as offset above
axis 72 in FIG. 7 to deflect end section 10D upwardly, it may be
offset laterally or downwardly by limited rotation of the drill
string through a defined angle if a different path of travel is
desired. It is noted that other parameters may be utilized to aid
in the control of direction of the drill string along the desired
travel path P as indicated above for the embodiment shown in FIG.
5, and, in addition, the speed of rotation of drill bit 78.
Enlarged diameter end portion 71 has a beveled leading end 79 which
rides along the surface 80 of bore B opposite the direction of the
offset and as a result of the offset directs bit 78 in the
direction of the offset. The amount of offset along with the other
parameters set forth for the embodiment of FIG. 5, and the speed of
rotation of drill bit 78, determine the amount of deviation or
deflection. Motor 70, as well known in the art, has a conventional
stator and rotor with drive shaft 74 connected to the rotor.
Drilling fluid passes through the rotor and stator to effect a
rotation of shaft 74 and drill bit 78, as well known in the
art.
While the bore hole B formed by drill bit 78 is illustrated
diagrammatically in FIG. 7 of a diameter not greater than the
diameter of enlarged end portion 71, it is to be understood that
the diameter of bore hole B formed by bit 78 is always of a
diameter greater than the diameter of end portion 71 in order to
provide a suitable annulus for the flow of drilling fluid and
cuttings from drill bit 78.
FIG. 8 shows a portion of a drill string having a plurality of
connected pipe sections 10D. Each drill pipe section 10D is of a
length of around thirty (30) feet and is formed of a high strength
flexible material. The end portions of pipe section 10D are of an
increased thickness and have externally threaded tapered ends 82.
Pipe section 10D is preferably formed of a high strength aluminum
alloy material. A pipe section 10D which has been found to be
satisfactory is a four and one-half (41/2) inch aluminum drill pipe
manufactured by Reynolds Metals Company, Richmond, Va. and having a
wall thickness of around one-half (1/2) inch, an inside diameter of
around three and one-half (31/2) inches, and a Young's modulus of
elasticity of ten million psi. Such a pipe section has been found
to be adequate to provide a deviation of around five (5) degrees
which permits a deflection of around fifteen (15) inches for a
thirty (30) foot length of pipe section.
For connecting pipe sections 10D to each other, male and female
tool joints indicated respectively at 84 and 86 are provided. One
end 82 of each section 10D has a male tool joint 84 connected
thereto and the other opposite end 82 has a female tool joint 86
connected thereto. Tool joints 84 and 86 are formed of a high
strength steel alloy material.
Tool joint 84 has an internally threaded female end portion 87 and
an externally threaded male portion 88 with tapered external
threads thereon. A shoulder 89 forms an abutting surface for the
adjacent end of pipe section 10D.
Female tool joint 86 has an internally threaded female end portion
90 having a hardened outer surface area indicated at 90A for wear
purposes and receiving an associated end 82 of pipe section 10D. A
shoulder 91 forms an abutting surface for the end of section 10D. A
female end portion 92 of tool joint 86 has tapered internal screw
threads to receive a mating end portion 88 of tool joint 84. Upon a
make-up of the connection, an interference fit is provided (1)
between the mating screw threads, (2) between shoulders 89 and 91
and the abutting ends of pipe sections 10D, and (3) between the
smooth outer surfaces 93 of pipe sections 10D adjacent their
threaded ends and the adjacent tool joints. Thus, the ends of pipe
section 10D are firmly gripped to provide a pressure tight assembly
and efficient transfer of tension, torsion, bending and compression
loads between pipe sections 10D and tool joints 84 and 86.
Since a relatively large diameter drill pipe is provided, adequate
space exists for the utilization of suitable electronic survey
equipment or the like indicated schematically at 93A which may be
positioned within the drill pipe section adjacent the leading end
of the drill string to provide signals to the surface for
indicating the position of the drill string and the direction of
travel thereof along the underground arcuate path.
It has been found with certain types of formations that it is
advisable to add a separate step to the method or process for
installing the production conduit, particularly where an
obstruction might be encountered in the formation when reaming the
large diameter hole. If an obstruction is encountered while reaming
the large diameter hole, it is desirable that the production
conduit not be connected to the reamer so that the reamer will be
freely movable for removal of the obstruction. For this purpose,
under certain types of operation, the reamer is pulled through the
pilot hole for enlarging the opening without having the production
conduit connected thereto. After the pilot hole has been enlarged,
the reamer is then pushed back through the empty hole to the exit
side and the production conduit is then attached to the reamer.
Then, the production conduit and reamer are pulled through the
enlarged hole for installation of the production conduit thereby to
insure that the enlarged hole is clear of any obstructions. Also,
less power is required to pull the production conduit into place if
the hole has been previously enlarged.
Referring also to FIGS. 9 and 10, an improved or modified spud bit
is shown generally at 94 and includes a generally tubular body 95
having an internally threaded end 96 threaded onto an externally
threaded end 97 of a suitable connecting tool joint 96 which is
connected at its opposite end to a drill pipe section 10D. The end
of bit 94 is closed at its leading end to form a head 100 having a
plurality of axis openings therein with their longitudinal axes
parallel to the longitudinal axis of the drill string. A ring 102
is secured to the leading end of bit 94. Body 95 has a plurality of
fluid nozzles designated 101A, 101B, 101C, 101D, 101E, 101F, 101G,
and 101H threaded therein in alignment with openings 101, each
nozzle having a fluid discharge port for discharging drilling fluid
in a high velocity jet or stream directly against the formation for
eroding the formation. Body 95 forms a planar leading face 104
extending in a plane at right angles to the longitudinal axis of
the drill string indicated at 106 and an inclined planar portion
108 extends rearwardly from leading face 104 at an angle A of
around five (5) degrees with respect to the longitudinal axis 106
of the drill string.
It is noted that the center of the combined jets of drilling fluid
from nozzles 101B through 101H would be balanced and parallel to
the longitudinal axis 106 of the drill string. However, the
addition of discharge nozzle 101A raises and offsets the center of
the combined jets or mass of drilling fluid to a position above
axis 106 and thus permits the drill string to be guided. The
rotation of the drill string through a defined predetermined angle
permits guidance or steering of the drill string. Drilling fluid
enters tubular body 95 and a fluid chamber 110 from the drill
string and is discharged through nozzles 101A-101H from leading
planar face 104 of drill bit 94.
While preferred embodiments of the present invention have been
illustrated in detail, it is apparent that modifications and
adaptations of the preferred embodiments will occur to those
skilled in the art. However, it is to be expressly understood that
such modifications and adaptations are within the spirit and scope
of the present invention as set forth in the following claims.
* * * * *