U.S. patent number 3,894,402 [Application Number 05/489,979] was granted by the patent office on 1975-07-15 for apparatus and method for emplacing a conduit along an underground arcuate path.
Invention is credited to Martin D. Cherrington.
United States Patent |
3,894,402 |
Cherrington |
July 15, 1975 |
Apparatus and method for emplacing a conduit along an underground
arcuate path
Abstract
A method for emplacing a production casing such as a pipeline or
other conduit beneath a surface obstacle such as a water course is
disclosed. A drill is provided which has a trailing drill string. A
pilot hole is drilled along an inverted arcuate path beneath a
surface obstacle from one side to the other side of the obstacle so
that the drill string occupies the pilot hole. A reamer is provided
which has a relatively smaller leading end and a larger trailing
end. The leading end of the reamer is attached to one of the ends
of the drill string, and an end of the production casing is
attached to the trailing end of the reamer. The production casing
is thrust into the pilot hole at one side of the surface obstacle
to project the reamer with the production casing following into the
pilot hole. As the production casing is thrust into the pilot hole
at one side of the obstacle, the drill string exits the pilot hole
at the opposite side of the obstacle. The reamer is operated by
rotating the production casing or other method simultaneously with
thrusting the production casing into the pilot hole to scarify and
dislodge the earth circumscribing the pilot hole. The pilot hole is
enlarged to a diameter slightly greater than the production casing
to provide an annulus between the production casing and the reamed
hole. Drilling mud is injected through the drill string to exit at
the reamer where it entrains the dislodged earth. The drilling mud
containing the dislodged earth is allowed to flow into the annulus
surrounding the production casing.
Inventors: |
Cherrington; Martin D.
(Sacramento, CA) |
Family
ID: |
23946082 |
Appl.
No.: |
05/489,979 |
Filed: |
July 19, 1974 |
Current U.S.
Class: |
405/184; 175/53;
175/62 |
Current CPC
Class: |
E21B
7/046 (20130101); E21B 21/00 (20130101); E21B
7/28 (20130101) |
Current International
Class: |
E21B
21/00 (20060101); E21B 7/28 (20060101); E21B
7/04 (20060101); E21B 7/00 (20060101); F16l
001/00 (); E02d 029/10 () |
Field of
Search: |
;61/72.1-72.7,84,85,42,43 ;175/44,45,61,62,53,171,260,257 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Taylor; Dennis L.
Attorney, Agent or Firm: Townsend and Townsend
Claims
What I claim as new is:
1. A method for emplacing a production casing beneath a surface
obstacle such as water course, said method comprising the steps
of:
providing a drill having a trailing drill string;
drilling a pilot hole along an inverted arcuate path beneath the
surface obstacle from a first side to a second opposite side of the
obstacle with said drill so that the drill string occupies the
pilot hole with the opposite ends of said drill string being on
opposite sides of the obstacle;
providing a reamer having a relatively smaller leading end and a
relatively larger trailing end;
attaching the relatively smaller leading end of the reamer to one
of the ends of the drill string;
attaching an end of the production casing non-rotatably to the
relatively larger trailing end of the reamer;
forcing the production casing into the pilot hole at one side of
the surface obstacle to project the reamer with said production
casing following into said pilot hole, the drill string exiting the
pilot hole at the other opposite end of the obstacle; and
rotating the production casing simultaneously with said thrusting
step to operate the reamer to scarify and dislodge the earth around
the pilot hole to enlarge the pilot hole to a diameter at least
equal to the production casing so that said production casing is
emplaced along the arcuate path as the pilot hole is being
enlarged.
2. A method as recited in claim 1 wherein said forcing comprises
thrusting the production casing at its trailing end.
3. A method as recited in claim 1 wherein rotating the production
casing to operate the reamer is adapted to enlarge the pilot hole
to a diameter slightly larger than the diameter of the production
casing to provide a narrow annulus circumscribing said production
casing, said method additionally comprising the steps of injecting
drilling mud into the end of the drill string opposite from the end
of the drill string attached to the leading end of the reamer so
that said drilling mud flows through said drill string to exit at
the reamer; entraining in said drilling mud the earth scarified and
dislodged by the reamer; and allowing the drilling mud containing
the scarified earth to flow into the annulus around the production
casing to lubricate the casing as it is forced into the pilot
hole.
4. A method as recited in claim 1 wherein rotating the production
casing to operate the reamer is adapted to enlarge the pilot hole
to a diameter slightly larger than the diameter of the production
casing, said method additionally comprising the steps of providing
an inlet pipe internal to the production casing, said inlet pipe
having one end terminating adjacent the reamer; injecting drilling
mud into the inlet pipe so that said drilling mud flows through
said inlet pipe to exit at the reamer; entraining in said drilling
mud the earth scarified by the reamer; and allowing the drilling
mud containing the scarified earth to flow into the annulus around
the production casing.
5. A method as recited in claim 1 wherein attaching the leading end
of the reamer to one of the ends of the drill string comprises
attaching the leading end of the reamer to the end of the drill
string at said first side of the surface obstacle.
6. A method as recited in claim 1 wherein said attaching the
leading end of the reamer to one of the ends of the drill string
comprises attaching the leading end of the reamer to the end of the
drill string at said second side of the surface obstacle.
7. A method as recited in claim 1 wherein said trailing drill
string comprises a plurality of drill string segments, and
additionally comprising the step of removing the segments
individually from the drill string as said drill string segments
exit the pilot hole at the opposite end of the obstacle.
8. A method as recited in claim 1 and additionally comprising the
step of providing an inclined drill rig at the first side of the
surface obstacle, and wherein said drilling step additionally
includes thrusting the drill string into the pilot hole with said
drill rig, wherein said production casing forcing step additionally
includes thrusting the production casing with said drilling rig,
and wherein said production casing rotating step additionally
includes rotating the production casing with said inclined drill
rig.
9. A method as recited in claim 1 and additionally comprising the
steps of filling the emplaced production casing with a liquid, and
inserting a plurality of product pipes in the filled production
casing, the leading ends of said product pipes being sealed to
provide buoyancy to said pipes as said pipes are inserted in the
production casing.
10. A method for emplacing a large diameter production casing
beneath a surface obstacle such as a water course, said method
comprising the steps of:
providing a drill having a trailing drill string;
drilling a pilot hole along an inverted arcuate path beneath the
surface obstacle from one side to the other with said drill so that
the trailing drill string occupies the pilot hole with the opposite
ends of said drill string being on opposite sides of the
obstacle;
providing a reamer having a relatively smaller leading end and a
relatively larger trailing end;
attaching the leading end of the reamer to one of the ends of the
drill string;
attaching an end of the large diameter production casing to the
trailing end of the reamer;
providing means for rotating the reamer internal to the production
casing;
forcing the production casing into the pilot hole to project the
reamer with said production casing following into said pilot hole;
and
rotating the reamer with said rotating means simultaneously with
said forcing step to operate the reamer to scarify and dislodge the
earth around the pilot hole to thereby enlarge the pilot hole to a
diameter at least equal to the production casing so that the said
production casing is emplaced along the arcuate path as the pilot
hole is being enlarged.
11. A method as recited in claim 10 wherein said providing means
for rotating the reamer comprises the step of providing a drive
shaft internal to the production casing, said drive shaft having a
power output end attached to the reamer, and wherein said rotating
the reamer step comprises rotating the reamer by rotating the drive
shaft simultaneously with said forcing step to operate the
reamer.
12. A method for emplacing a production casing beneath a surface
obstacle such as a water course, said method comprising the steps
of: providing a drill having a trailing drill string; drilling a
pilot hole along an inverted arcuate path beneath the surface
obstacle from a first side to a second opposite side of the
obstacle with said drill so that the trailing drill string occupies
the pilot hole with the ends of said drill string being on opposite
sides of the obstacle; providing a reamer having a relatively
smallerleading end and a relatively larger trailing end; attaching
the leading end of the reamer to one of the ends of the drill
string; connecting an end of the production casing to the trailing
end of the reamer; providing means for rotating the reamer;
thrusting the production casing into the pilot hole to project the
reamer with said production casing following into said pilot hole;
rotating the reamer with rotating means simultaneously with said
thrusting step to operate the reamer to scarify and dislodge the
earth around the pilot hole; injecting drilling mud into the end of
the drill string opposite from the end of the drill string attached
to the leading end of the reamer so that said drilling mud flows
through said drill string to exit at the reamer; and allowing the
drilling mud containing the scarified earth to flow into the
annulus around the production casing so that the production casing
slips easily into the enlarged hole.
13. A method as recited in claim 12 and additionally comprising the
steps of providing a return pipe internal to the production casing;
providing communication between said return pipe and the outer
surface of the production casing; and allowing the drilling mud
contained in the annulus around the production casing to flow out
of the production casing through the return pipe.
14. A method as recited in claim 12 wherein the trailing end of the
reamer is nonrotatably attached to the production casing, and
wherein providing means for rotating the reamer comprises providing
means for rotating the production casing to rotate the reamer.
15. A method as recited in claim 12 wherein said providing means
for rotating the reamer comprises providing a drive shaft internal
to the production casing, said drive shaft being connected to the
reamer so that rotation of the drive shaft rotates the reamer.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method for emplacing a
production casing such as a pipeline or other conduit beneath a
surface obstacle such as a water course.
The traditional method for laying pipelines, telephone cables and
other underground conduits is to dig an open trench, lay the
conduit in the trench and then close the trench. This method is
quite efficient in general, but problems arise when an obstacle
such as a water course or a heavily traveled road is encountered,
and the conduit must traverse the obstacle.
When a road is encountered, the road must either be closed, the
traffic diverted, or parts of the road closed and the conduit laid
in sections, all of which are inconvenient and interfere
substantially with the use of the road. When a conduit must span a
water course, other problems arise. First, the trench must be dug
to a depth considerably below the level at which the conduit is to
be laid since the current will partially fill the trench before the
conduit can be inserted. This is a significant problem because such
trenches have a generally triangular cross section, and the volume
of dirt which must be removed increases with the square of the
depth of the trench. Such trenching also stirs the alluvium at the
bottom of the water course interfering with the natural flora.
Even after a trench has been dug in a water course, difficulties
arise in placing the conduit therein. One method of placing the
conduit is to float it across the span of the water course and then
remove its buoyancy to sink the pipe into the trench. The
difficulty with this method is that the water course must be closed
to traffic, floating objects are trapped by the floating conduit,
the current of the river bends the conduit, and when the conduit is
sunk, it quite often misses the trench. A second method is to
attach a sled or skid to the leading end of the conduit, and drag
this leading end through the trench to lay the conduit. With this
method, the conduit must be coated with a substance to give it
negative buoyancy, and this coating is quite expensive since the
entire length of the conduit must be so coated.
In my previously filed patent application entitled, "APPARATUS AND
PROCESS FOR DRILLING UNDERGROUND ARCUATE PATHS," Ser. No. 421,548,
now pending, a method for drilling along an inverted underground
arcuate path under a surface obstacle is disclosed. However, such
methods are used primarily for drilling a relatively small pilot
hole which must be significantly enlarged in order that a
production casing such as a pipeline, telephone cable and other
underground conduits can be placed therein.
One of the methods which has been tried experimentally to enlarge
an arcuate pilot hole so that a production casing can be placed
therein has been to pull a reamer through the pilot hole with the
drill string used in drilling the pilot hole, and having a larger
drill string trailing the reamer. After the hole has been reamed
from end to end, a production casing is attached to the end of the
larger drill string, and the larger drill string is dragged through
the hole with the production casing following to place the casing
therein. However, this method was unsuitable for several reasons.
First, pulling the reamer through the arcuate hole results in the
drill string knifing through the soil and the reamer does not
follow the original reamed hole. Another reason is that pulling the
production casing into the hole without providing lubricating
drilling mud scars the outside of the casing, which is particularly
critical when gas or oil lines are being installed. The results of
this method were found to be commercially unfeasible because the
integrity of the pipeline installed could not be guaranteed, and
also the complexity and difficulty of the method did not warrant
its use over other alternative methods.
SUMMARY OF THE INVENTION
The present invention relates to a method for emplacing a
production casing such as a pipeline or other conduit under a
surface obstacle. A drill is provided having a trailing drill
string. A pilot hole is drilled along an inverted arcuate path
beneath the obstacle from one side to the other so that the
trailing drill string occupies the pilot hole. A reamer is provided
having a relatively small leading end and a relatively larger
trailing end, and the leading end of the reamer is attached to one
of the ends of the drill string. The production casing is attached
to the trailing end of the reamer. The production casing is thrust
into the pilot hole to project the reamer with the production
casing following into the hole, and the drill string exits the
pilot hole at the other side of the obstacle. The reamer is rotated
either by rotating the production casing or other method
simultaneously with the thrusting of the production casing to
operate the reamer to scarify and dislodge the earth surrounding
the pilot hole. The pilot hole is enlarged to a diameter at least
equal to the diameter of the production casing so that the
production casing is placed along the arcuate path as the pilot
hole is being enlarged.
In the preferred embodiment of the present invention, drilling mud
is injected into the drill string so that it exits at the reamer.
The drilling mud thus entrains the earch scarified and dislodged by
the reamer. The pilot hole is reamed to a diameter slightly larger
than that of the production casing and the drilling mud with the
entrained earth therein flows into this annulus. The drilling mud
lubricates the production casing as it is thrust ino the hole so
that friction on the production casing is minimized and there is no
damage to the outer surface of the casing. Insertion of the
production casing can be further facilitated by matching the
buoyancy of the casing to the drilling mud and the casing will slip
easily into the hole.
When the surface obstacle is relatively wide, it is preferred to
remove excess drilling mud containing the entrained earth therein
from the hole. A relatively small return pipe is placed internal to
the production casing, and is connected to the annulus around the
casing. Drilling mud still fills the annulus to lubricate the
production casing, but the excess drilling mud exits the hole
through the return pipe so that the hole is not enlarged more than
necessary and does not "blow out," as described below. The diameter
of the return pipe can be selected so that the casing has neutral
buoyancy and other weights are not required.
In one of the embodiments of the present invention, the reamer is
non-rotatably attached to the production casing, and the production
casing itself is rotated in order to operate the reamer. This has
the secondary advantage that the friction between the production
casing and the sides of the hole is reduced because the casing
rotates as it enters the hole. However, the production casing is
being placed along an arcuate path and the side walls of the casing
are flexed upon each revolution of the casing. For larger diameter
production casings, this flexing can cause fatigue failure. Hence,
an alternate embodiment of the present method is provided wherein
the production casing is rotatably attached to the reamer, so that
the casing does not rotate, and a drive shaft or other mechanism is
employed to operate the reamer.
The novel features which are believed to be characteristic of the
invention, both as to organization and method of operation together
with further objects and advantages thereof will be better
understood from the following description considered in connection
with the accompanying drawings in which preferred embodiments of
the invention are illustrated by way of example. It is to be
expressly understood, however, that the drawings are for the
purpose of illustration and description only and are not intended
as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the completion of the pilot hole
underneath the surface obstacle;
FIG. 2 is a perspective view similar to that of FIG. 1 illustrating
the reaming of the pilot hole to selected larger diameter;
FIG. 3 is a fragmentary elevation view of the reaming apparatus of
the present invention;
FIG. 4 is a fragmentary elevation view of the reaming apparatus of
the present invention partially cut away; and
FIG. 5 is a fragmentary elevation view of an alternate embodiment
of the present invention;
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The drilling of the pilot hole 10 beneath a surface obstacle such
as water course 12 is illustrated by way of reference to FIG. 1. An
inclined drill rig 14 is placed in an inclined pit 16 at one side
of water course 12. A drill bit 18 having a trailing drill string
20 is directed along the desired arcuate path to exit at the other
side of obstacle 12. Drill string 20 comprises a plurality of
interconnected drill string segments which are joined to form the
drill string. After drill bit 18 emerges at the other side of
obstacle 12, drill string 20 occupies the entire pilot hole 10.
In order to enlarge pilot hole 10, the smaller leading end of a
frustro-conical reamer 30 is attached to one end of drill string 20
as illustrated in FIG. 2. In the preferred embodiment of the
present invention, production casing 32 is non-rotatably attached
to the larger trailing end of reamer 30. The production casing is
forced into pilot hole 10 by thrusting the casing at its trailing
end using drill rig 14, and reamer 30 is operated by rotating the
casing. Production casing 30 can be either a steel or cement pipe
such as used for oil and water pipelines, protective casings for
telephone lines and the like. Production casing 32 consists of a
plurality of segments such as 34.
In the embodiment of the present invention illustrated in FIG. 2, a
tube 36 is attached to the leading end of drill string 20. Tube 36
is attached to a pump 38 which forces drilling mud through the
drill string to exit at the reamer. As sections of drill string 20
emerge from the pilot hole as production casing 32 is thrust
therealong, the segments are placed in a pile 40 and tube 36 is
reattached to the leading end of the next segment. Hence, drilling
mud is continuously injected into pilot string 20 to exit at the
reamer. As the segments of drill string 20 are taken off the
leading end thereof, segments 34 of production casing 32 are added
at the trailing end. The drill rig 14 used for drilling the pilot
hole also acts to thrust the production casing 32 into the ground
in this embodiment as illustrated by arrow 42, and in the preferred
embodiment rotates the production casing as well as operates the
reamer.
The manner in which reamer 30 is interposed between drill string 20
and production casing 32 is illustrated in more detail in FIG. 3.
The narrower leading end of frustro-conical reamer 30 connects
non-rotatably to drill string 20. In the preferred embodiment, the
larger trailing end of reamer 30 is non-rotatably connected to
production casing 32. Reamer 30 has a plurality of reamer teeth 42
which enlarge pilot hole 10 to a diameter slightly larger than that
of production casing 32. This provides a small annulus 44 about the
outer diameter of production casing 32. Drilling mud which is
injected through drill string 20 and exits at reamer 30 flows
around the reamer and entrains the earth 46 scarified and dislodged
by reamer teeth 42 as illustrated by arrows 48. The drilling mud
containing the dislodged earth flows into the annulus 44
circumscribing the production casing 32 as illustrated by arrows
50. The used drilling mud serves to lubricate production casing 32
so that it slips easily into the enlarged hole.
When the relatively long production casing is to be placed under
the ground, the buoyancy of the production casing can be a critical
problem. Since the density of production casing 32 with its hollow
interior is substantially less than that of the drilling mud in
annulus 44 for larger production casings, the production casing
will be forced upwardly and will distort the path of the production
casing as it is being emplaced. For smaller production casings, the
density of the casing with its hollow interior is greater than that
of the drilling mud and the weight of the casing distorts the path.
One of the features of the present invention is to weight the
production casing 32 so that its density including the hollow
interior is substantially equal to that of the drilling mud. In
this situation, the production casing 32 will have neutral buoyancy
with respect to the drilling mud and will slip easily into the hole
along the axis of pilot hole 10. Such neutral buoyancy can be
achieved by placing foam inside the production casing, coating the
casing, placing weights in the casing, and the like.
A preferred embodiment of the present invention wherein excess
drilling mud is removed as the production casing 32 is being
emplaced is illustrated by way of reference to FIG. 4. In this
embodiment, drilling mud is injected through drill string 20 as
illustrated by arrow 60 as previously shown. This drilling mud
exits at the reamer and flows into the annulus 44 around production
casing 32. However, in order to relieve the pressure of the
drilling mud in annulus 44, an internal return pipe 62 is provided
inside production casing 32. Return pipe 62 has a plurality of
extensions 64 which communicate with holes 66 in the walls of
casing 32. In this manner, a connection is provided between return
pipe 62 and annulus 44 so that excess drilling mud in the annulus
can flow out through return pipe 62 as illustrated by arrow 68.
Since volumetric flow of drilling mud into the hole is generally
greater than that which can be accommodated by annulus 44, failure
to provide a return pipe such as 62 forces the drilling mud to flow
backwardly along the production casing 32. In the placing of a
relatively long production casing, the pressure on the enlarged
hole adjacent the reamer will be relatively large to force the mud
along the entire casing. As a result, when drilling under river
bottoms and the like, the hole may "blow out" due to this pressure
and water from the river can flow into the hole. Also, the excess
drilling mud will flow into the water course and pollute the stream
and destroy the natural wildlife. The provision of return pipe 62
will avoid such a "blow out" when long production casings are
emplaced. A further advantage of the return pipe is that the
diameter of the pipe can be selected so that the drilling mud will
weight production casing 32 so that it has neutral buoyancy with
respect to the drilling mud. Hence, a separate weighting mechanism
need not be provided to achieve neutral buoyancy.
In the preferred embodiment, pipe 62 is used to return used
drilling mud as illustrated by arrows 68. However, as an
alternative embodiment, a pipe such as 62 can be used to inject
drilling mud so that it exits near reamer 30 rather than inject
drilling mud through drill string 20. To this end, pipe 62 would be
extended as illustrated in phantom 69 so that the drilling mud
would be injected at reamer 30 rather than into annulus 44. After
the drilling mud entrains the earth scarified and dislodged by
reamer 30, the used drilling mud flows into annulus 44 as in the
previous embodiments.
An alternate embodiment to those discussed above which is primarily
adapted for use with relatively large production casings is
illustrated in FIG. 5. When a production casing such as casing 70
has a diameter of greater than approximately 20 inches, rotating
the production casing in the arcuate path can cause excessive
fatigue of the casing and it is preferred not to rotate the casing.
For such large production casings 70, the casing is rotatably
attached to the trailing end of a reamer such as 72. The leading
end of reamer 72 is non-rotatably attached to drill string 74, and
drilling mud is injected through drill string 74 as illustrated by
arrow 76, similar to the method described above. However, reamer 72
is operated by means of a drive shaft 78 which rests along the
bottom of casing 70. A pulley 80 or gear arrangement is connected
to reamer 72 so that rotation of drive shaft 78 operates the
reamer. As an alternative, a drilling motor as known in the art can
be placed at the leading end of casing 70 to operate the
reamer.
In the embodiment illustrated in FIG. 5, a return pipe, such as
return pipe 62 illustrated in FIG. 4, could also be provided. Also,
the production casing 70 could be rotated slowly (relative to the
rotation of the reamer 72) to make the casing slip more easily into
the hole and reduce friction thereon. Fatigue of the casing is
dependent upon the speed of rotation of the casing so that at low
speed rotation may be acceptable where high speed rotation such as
required to operate the reamer is not acceptable.
In many applications such as the installation of telephone lines,
several smaller product pipes are installed in the production
casing after it is in place. This installation is facilitated by
filling the production casing with a fluid such as treated water or
oil and sealing the leading ends of the product pipes before
inserting them in the production casing. As a result, the product
pipes will be at least partially buoyant so that they will float
easily into the production casing.
While preferred embodiments of the present invention have been
illustrated in detail, it is apparent that modifications and
adaptations of that embodiment 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.
* * * * *