U.S. patent number RE33,660 [Application Number 07/530,816] was granted by the patent office on 1991-08-13 for apparatus for drilling a curved borehole.
This patent grant is currently assigned to Baroid Technology. Invention is credited to Henk H. Jelsma.
United States Patent |
RE33,660 |
Jelsma |
August 13, 1991 |
Apparatus for drilling a curved borehole
Abstract
A non-rotating drill string is formed from a plurality of
independent, cylindrical sections pivotally connected together by a
latch mechanism. The adjacent ends are partially beveled such that
the sections can bend in a single direction. Means are disclosed
for varying the effect of the beveled surfaces, thus controlling
the angle of bend for a given one of the sections. A downhole mud
motor (PDM) drives the drill bit through the use of a flexible
drive shaft running through the center of a metal-lined, neoprene
drilling fluid hose which runs through the interior of the
independent cylindrical sections. The total curvature of the
borehole drilled by the system equals the sum of the angles of bend
between the individual sections.
Inventors: |
Jelsma; Henk H. (Spring,
TX) |
Assignee: |
Baroid Technology (Houston,
TX)
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Family
ID: |
26853552 |
Appl.
No.: |
07/530,816 |
Filed: |
May 30, 1990 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
156831 |
Feb 17, 1988 |
04880067 |
Nov 14, 1989 |
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Current U.S.
Class: |
175/107; 175/61;
175/73; 175/320 |
Current CPC
Class: |
E21B
7/061 (20130101); E21B 17/20 (20130101); E21B
4/02 (20130101); E21B 7/068 (20130101) |
Current International
Class: |
E21B
4/02 (20060101); E21B 4/00 (20060101); E21B
17/20 (20060101); E21B 7/04 (20060101); E21B
7/06 (20060101); E21B 17/00 (20060101); E21B
007/06 (); E21B 017/20 () |
Field of
Search: |
;175/61,45,73,76,79,89,107,101,92,320,324,325 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Claims
What is claimed is:
1. A drill string for drilling a curved borehole, wherein said
drill string has a plurality of cylindrical sections, each of said
sections having a longitudinal axis and also having an upper end
and a lower end, comprising:
a first of said drill string sections having first and second
surfaces on the said lower end of said first section; and
a second of said drill string sections having first and second
surfaces on the said upper end of said second section, said first
surfaces being parallel to each other and perpendicular to each
said longitudinal axis and an angle being formed between said
second surfaces.
2. A drill string for drilling a curved borehole, wherein said
drill string has a plurality of cylindrical sections, each of said
sections having a longitudinal axis and also having an upper end
and a lower end, comprising:
a first of said drill string sections having first and second
surfaces on the said lower end of said first section;
a second of said drill string sections having first and second
surfaces on the said upper end of said second section, wherein said
first surfaces are parallel to each other and perpendicular to each
said longitudinal axis and a first angle exists between said second
surfaces while said drill string is being lowered vertically, and
when said drill string is in the process of drilling a curved
borehole, the said second surfaces are parallel and a second angle
exists between said first surfaces.
3. The drill string according to claim 2 including, in addition
thereto, means to vary said first angle.
4. A drill string for drilling a curved borehole, wherein said
drill string has a plurality of cylindrical sections, each of said
sections having a longitudinal axis and also having an upper end
and a lower end, comprising:
a first of said drill string sections having first and second
surfaces on the said lower end of said first section;
a second of said drill string sections having first and second
surfaces on the said upper end of said second section, wherein said
first surfaces are parallel to each other and perpendicular to each
said longitudinal axis and a first angle exists between said second
surfaces while said drill string is being lowered vertically, and
while said drill string is in the process of drilling a curved
borehole, the said first angle is reduced and a second angle is
formed between said first surfaces.
5. The drill string according to claim 4 including, in addition
thereto, means to vary the amount the said first angle is
reduced.
6. A drilling system for drilling a curved borehole,
comprising:
a drill string having a plurality of independent cylindrical
sections pivotally connected together;
a PDM motor in said drill string;
a drill bit in said drill string;
a steel-lined neoprene hose for delivering drilling fluid from said
motor to said drill bit; and
a flexible drive shaft connected between said motor and said drill
bit, said independent sections having the ability to bend only in a
single direction while said system is drilling said curved
borehole.
7. The system according to claim 6 wherein said independent
sections are pivotally connected together with pairs of latch
assemblies, each of said latch assemblies comprising a metal strap
enclosed within a latch box having a slightly larger width than the
width of said strap, each said strap being pivotally connected to
two of said plurality of sections.
8. A drilling system for drilling a curved borehole, comprised of a
drill string having a first location and a second location, and
having independent sections therebetween, a PDM motor in the first
location of said drill string, and a drill bit in the second
location of said drill string, a flexible pressure hose interior of
said independent sections and connected between said PDM motor and
said drill bit and a flexible drive shaft interior of said pressure
hose connected between said PDM motor and said drill bit, said
independent sections having the ability to bend in only a single
direction while said system is drilling said curved borehole.
.Iadd.
9. A drilling system for drilling a curved borehole,
comprising:
a drill string including a plurality of tubular members connected
together and having an interior flow path for transmitting
pressurized fluid;
a fluid-driven motor having a drive shaft within the drill
string;
a drill bit at an end of the drill string;
a plurality of cylindrical sections spaced within the drill string
between the motor and the drill bit, the plurality of cylindrical
sections pivotally connected together to bend only in a single
direction while the system is drilling a curved borehole;
a flexible pressure hose interior of the plurality cylindrical
sections for delivering pressurized fluid from the motor to the
drill bit; and
a flexible shaft positioned within the pressure hose and
mechanically interconnected the drill bit to the motor drill shaft.
.Iaddend. .Iadd.10. The drilling system as defined in claim 9,
wherein;
each of the plurality of cylindrical sections has a longitudinal
axis, an upper end, and a lower end;
a first of the cylindrical sections having its upper end connected
to the fluid driven motor and having first and second surfaces on
its lower end; and
a second of the cylindrical sections having first and second
surfaces on its upper end, wherein the first surfaces are parallel
to each other and perpendicular to each of the longitudinal axes
and a first angle exists between the second surfaces while said
drill string is being lowered vertically, and when the system is
drilling the curved borehole the first angle is reduced and a
second angle is formed between the first surfaces. .Iaddend.
.Iadd.11. The drilling system as defined in claim 10, further
comprising:
adjusting means to vary the reduction of the first angle.
.Iaddend.
.Iadd. . A system as defined in claim 9, wherein one of said
plurality of cylindrical sections is a bearing sub, the bearing sub
houses a plurality of bearings, and the plurality of bearings
include radial bearings and thrust bearings. .Iaddend. .Iadd.13. A
drilling system as defined in claim 12, further comprising:
a flow restrictor for diverting pressurized fluid to lubricate the
plurality of bearings. .Iaddend. .Iadd.14. A drilling system as
defined in claim 12, further comprising:
the bearing sub is the lowermost of the plurality of cylindrical
sections. .Iaddend. .Iadd.15. A drilling system as defined in claim
12, wherein a lower end of the flexible pressure hose terminates
within the bearing sub at a position axially above the plurality of
bearings. .Iaddend. .Iadd.16. A drilling system as defined in claim
9, further comprising:
a pair of latch assemblies for pivotably connecting the cylindrical
sections together, each of the latch assemblies including a metal
strap enclosed within a latch box having a slightly larger width
than the width of the corresponding strap, each strap being
pivotably connected to two of the plurality of cylindrical
sections. .Iaddend. .Iadd.17. A drilling system as defined in claim
9, wherein the fluid-driven motor is a positive displacement mud
motor. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, generally, to a method and apparatus
for drilling a curved borehole and, specifically, to a method and
apparatus for drilling a curved borehole while presetting the
amount of angle building in the curvature of such borehole.
2. Description of the Background
The prior art has typically involved the rotation of the drill
string and used, for example, bent subs to control the curvature of
the borehole. Other prior art methods and apparatus have involved
attempts to control the curvature through the controlled angling of
the drill bit and/or the controlled angling or bending of the
downhole mud motor used to rotate the drill bit.
SUMMARY OF THE INVENTION
The invention comprises a new and improved method and apparatus
which utilizes a plurality of independent sections in a drill
string to drill a curved borehole, wherein each of said sections
has an ability to bend in only one direction. The sections are
pivotally connected together.
As an additional feature of the invention, the angle through which
an individual section can bend is adjustable.
As yet another feature, the drill string is formed with a plurality
of such sections, with the total of the individual angles between
sections being equal to the total degree of curvature of the
drilled borehole.
As still another feature of the invention, a downhole mud motor
drives a drill bit through the use of a flexible drive shaft
running through a flexible drilling fluid hose passing through the
interior of the independent sections.
As yet another advantage of the invention, the drill string made up
of the individual sections is caused to be deflected by a diverter
shoe in the well bore having the same angle and direction of
curvature as that of the desired angle of curved borehole.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, in cross section, of a cased earth
borehole in which a deflection shoe has been used in conjunction
with a casing window mill bit to cut a window in the casing in
proximity to a targeted production zone;
FIG. 2 is an elevational view of a drill string in accordance with
the present invention, shown traversing a cased earth borehole
prior to encountering the deflection shoe in FIG. 1;
FIG. 3 is a schematic view of the drill string illustrated in FIG.
2, shown continuing to drill the targeted production zone after
having contacted the deflection shoe illustrated in FIG. 1;
FIG. 4 is an elevated view, partially in cross section, of the
hang-off sub portion of the drill string illustrated in FIG. 2,
illustrating a portion of the high pressure mud hose the flexible
drive shaft;
FIG. 5 is a cross-sectional view taken along the section lines 5--5
of FIG. 2;
FIG. 6 is a schematic view, partially in cross section, of the
lower end of the drill string illustrated in FIG. 2, illustrating
the bearing sub into which the drill bit box is rotatably
mounted.
FIG. 7 is a top plan view of the connection junction between the
drill bit box and the flexible drive shaft;
FIG. 8 is a schematic view of one embodiment of the apparatus used
to vary the preset angle of the drill string;
FIG. 9 is a schematic view of an alternative embodiment of the
apparatus used to vary the preset angle of the drill string;
and
FIG. 10 is a schematic view of portions of two sections of the
drill string according to the present invention, showing in greater
detail the strap and boxes used to hold the sections together.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawings, an each borehole 10 having
a steel casing 12 therein traverses the earth formations 14.
Although not illustrated, the borehole 10 extends to the earth's
surface. Based upon an evaluation of these earth formations 14
through the use of conventional seismic prospecting methods, taken
in conjunction with well logging data, the zone 16 has been
targeted for lateral drilling. Through the use of lateral drilling,
a horizontal well can be drilled through the producing zone 16,
allowing the formation to be drained into a horizontal well bore
that extends into the reservoir at a depth, where a maximum output
can be achieved over a specific length of time in order to obtain
either a quick return on investment, or extend or increase the
producing life of a reservoir.
Although not illustrated in FIG. 1, once the depth of the targeted
production zone 16 has been fully identified, a conventional
deflection shoe 18 is run into the earth borehole 10 on a tubing
string 20 which can be anchored to the casing 12 through means of a
conventional anchor or an inflatable packer 22. The setting of the
deflection shoe 18 is well known in the art, for example, as shown
in U.S. Pat. No. 4,266,621 which is incorporated herein by
reference. The well casing window mill bit which is shown in that
same patent can be run into the well on a conventional drill string
to mill out the window 24 in the casing 12 in proximity to the
targeted formation 16. As illustrated in FIG. 1, once the window
has been cut through the casing, the conventional drill string and
casing window mill bit are removed from the borehole 10.
Referring now to FIG. 2, there is illustrated a drill string in
accordance with the present invention which is run into the earth
borehole 10 of FIG. 1 subsequent to the removal of the drill string
bearing the casing window mill bit. The drill string 30 is made up
of a plurality of drill string sections 32, 34 and 36. In putting
together an actual drill string, the present invention contemplates
the use of as many of these sections as is required to build up the
desired angle. For example, if the angle between two sections is
3.degree., and a 90.degree. total angle is desired, there will be
thirty-one of these sections. The sections are held together
through pairs of latches, for example, two latches, such as the
latch 38 which holds together the sections 32 and 34. Latch 38 is
shown in greater detail in FIG. 10 and includes a metal strap 40
pivotally connected to the pins 42 and 44 with pin 42 being an
integral part of the section 32 and pin 44 being an integral part
of section 34. The strap 40 can pivot within the U-shaped sections
46 and 48 which are sized slightly larger than the width of the
strap 40. If desired, the straps 40 can be U-shaped in cross
section for additional strength.
Referring again to FIG. 2, it should be appreciated that the
latches 38 are preferably arranged in pairs. Thus, there would be
another identical latch on the opposite side of the drill string
from the latch 38 as illustrated.
Within the interior of the sections 32, 34 and 36 and also within
the hang-off sub 50 runs a continuous, steel-lined, neoprene high
pressure hose 52 which transports the drilling mud. The hose 52 is
latched on its top end to the hang-off sub 50 with its bottom end
latched to the bearing sub 54. A conventional drill bit 56 is
threaded into a bit box 58 which is rotatably mounted within the
bearing sub 54. A conventional small kick stabilizer 60 is mounted
on the side of the bearing sub 54 opposite the direction in which
the drill string will ultimately be drilling.
Referring now to FIG. 3, there is illustrated schematically the
drill string illustrated in FIG. 2 having encountered the diverter
shoe 18, passing through the window 24 in the casing 12 and
continuing to drill into the targeted zone 16. It should be
appreciated that the sections 32, 34 and 36 can only pivot in the
direction as illustrated. The deflection shoe 18 preferably has an
angle of deflection equivalent to the angle capability of the drill
string in accordance with the present invention. Drilling off from
the face is achieved by rotating the bit 56 through the use of a
conventional positive displacement mud motor (FDM) 51 in the drill
string which is arranged through the hang-off sub 50 to drive the
drill bit 56 through a flexible drive shaft. As the drill bit 56
passes through the window 24 and commences drilling, the drill
string assembly will fold into the desired bend and will drill off
the deflection face. The starting angle, through the small kick
stabilizer 60 on the low side of the bearing sub 54 will increase
as more weight is added, due to the formation interference that
will now act as a deflection wedge itself. The drilling will
continue until the total desired angle is obtained. At specific
intervals as desired, the assembly will be withdrawn, the hole
surveyed and re-entered until a conventional type of flexible
rotary drilling string is reinserted to continue the horizontal
path, if desired.
Referring now to FIG. 4, there is illustrated in cross section the
hang-off sub 50. The PDM downhole motor 51 (not illustrated in FIG.
4) threads into the upper portion of the hang-off sub 50 and will
have a drive shaft which mates with the shaft box 70. The transfer
axle 72 is mounted on top of the articulated, flexible drive shaft
74. The downward weight is carried through a ball bearing system 76
and 78 carried by the hang-off ring 80. Again it should be
appreciated that the PDM motor 51 to be used with the hang-off sub
50 is conventional and will have a standard pin and box connection
for mating with the box connection at the top end of the hang-off
sub 50. The continuous, steel-lined, neoprene, high pressure hose
52 is also connected to the ring 80. The axial flow velocity of the
drilling mud through the hose 52 can be controlled, if desired, by
controlling the openings (not illustrated) in the transfer axle 72.
It should be appreciated that the lower end of the hang-off sub 50
can either be threadedly engaged with the top section 32 or can be
held onto section 32 through the use of a strap 38 if desired.
FIG. 5 illustrates a cross-sectional view taken along the section
lines 5--5 of FIG. 2. It should be appreciated that the outer shell
of the cylindrical section 34 surrounds the high pressure hose 52
which in turn surrounds the flexible drive shaft 74. On opposite
sides of the shell of the section 34 there are located the U-shaped
boxes 48 and 48' for holding the latch 40 (not illustrated in this
figure).
Referring now to FIG. 6 there is illustrated in greater detail the
bearing sub 54. Bearing sub 54 is latched to the section 36 by a
latch member similar to latch 38. A hose connector 80 connects the
bottom end of the hose 52 to the body of the bearing sub 54. The
drill bit box 82 into which the drill bit 56 is threadedly
connected is .[.retained in.]. .Iadd.rotatably mounted relative to
.Iaddend.the fixed body 84 by radial bearings 86 and three rows of
retainer thrust bearings 88, 90 and 92. These bearings are
lubricated through mud flow that is allowed to flow through the
flow restrictor 94. The drive shaft 74 is inserted into the grooved
connections 96 (see FIG. 7) of the drive shaft retaining ring 98
shown in FIGS. 6 and 7.
In the operation of the embodiment shown in FIGS. 4 and 6, it
should be appreciated that as the PDM motor (not illustrated in
these figures) causes the transverse axle 72 to rotate the flexible
drive shaft 74, which in turn is connected at its lower end through
the retaining ring 98 to the bit box 82 which causes the bit 56 to
rotate. As drilling fluid passes through the PDM and through the
transverse axle 72, it enters the high pressure hose 52 and exits
at the lower end of the hose through the flow restrictor 94,
through the retaining ring 98 to the interior of the bit box 82 and
hence to the interior of the drill bit 56 for exit therefrom in the
conventional manner.
Referring now to FIG. 8, there is illustrated schematically a
method and apparatus for varying the angle between the sections 32
and 34. For ease of illustration, the latch mechanism between
theses two sections is not illustrated in FIG. 8. If it were not
for the bolt 110, the lower beveled edge 112 of section 32 would
form a given angle A with the upper beveled edge 114 of section 34.
The angle A between lines 112 and 114 is preferably maintained at
3.degree.. By using a threaded bolt 110, threaded into the surface
112, the surface 114 can only rotate through the angle B which is
coincident with the head of the bolt 110. Thus, by varying the
distance into which the bolt 110 travels into surface 112, the
angle achieved will vary preferably between 0.5.degree. and
3.degree.. Alternatively, steel pegs of predetermined length can be
driven into holes in the surfaces, with a predetermined portion of
each such peg protruding from the surface.
FIG. 9 illustrates schematically an alternative embodiment for
changing the angle between the surfaces 112 and 114. By using a
wedge-shaped member 116 attached to the upper surface 112 with a
bolt 118, the angle C can be selected to be any value between zero
(by having the wedge shape 116 also touch the surface 114), up to
approximately 3.degree..
The preferred embodiments contemplate that both the upper and lower
surfaces of the sections be beveled such that a V shape is formed
between the adjacent surfaces. However, it should be appreciated
that both surfaces need not be beveled. For example, as illustrated
in FIG. 9, the wedge-shaped section 116 could be integrally formed
with the section 32 and only have the surface 114 be beveled.
Conversely, the top of section 34 could be flat, i.e., not beveled,
and only have the surface 112 be beveled. Moreover, while the
preferred embodiment of the invention contemplates that the angles
between adjacent sections be the same throughout the curved
section, the angles can be different, if desired. For example, the
angle between sections 32 and 34 might be set at 3.degree., and the
angle between sections 34 and 36 could be set at 2.degree.,
etc.
Thus, it should be appreciated that there has been described and
disclosed herein a drill string system which allows a vertical well
bore to be re-entered while being lowered vertically, and with a
controlled flexibility to drill a curve up to 90.degree. and even
further. The system is designed such that no rotation is required
to the main body of the string. Other variations of the preferred
embodiments will become apparent to those skilled in the art from a
reading of the foregoing description. For example, although the
preferred embodiment contemplates the use of a diverter shoe to
cause the drill string to pass out through a window in the casing,
those skilled in the art will recognize that a similar diverter
shoe can be anchored in an open hole and thus allow the drill bit
and related drill string to drill directly into the formation from
the open hole. The system described herein allows the non-rotating
drill string to bend in only a single direction. As illustrated in
FIG. 8, the section 34 can rotate with respect to the section 32
only in the direction which decreases the angle A during bending,
since the non-beveled surface area 120 on the lower side of section
32 is parallel and already touching the surface portion 122 on the
upper end of section 34. Thus, as best illustrated in FIG. 2, when
it is desired that the drill string bend to the right, the beveled
portions of the sections are maintained on the right-hand side of
the well bore. Conversely, when it is desired that the drilll
string bend to the left, the beveled sections will be maintained on
the left-hand side of the well bore.
* * * * *