U.S. patent application number 09/917612 was filed with the patent office on 2002-04-18 for erectable arm assembly for use in boreholes.
Invention is credited to Meyer, Timothy Gregory Hamilton, Stockwell, Matthew, Trueman, Robert.
Application Number | 20020043404 09/917612 |
Document ID | / |
Family ID | 25645442 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020043404 |
Kind Code |
A1 |
Trueman, Robert ; et
al. |
April 18, 2002 |
Erectable arm assembly for use in boreholes
Abstract
An erectable arm assembly for use in a borehole, the erectable
arm assembly comprising a main body and an arm member, the arm
member being able to move between a collapsed position in which the
assembly can be removed from the borehole and an erected position,
the erectable arm assembly being adapted to house a fluid drilling
assembly comprising a fluid cutting device and a flexible hose
drill string such that the arm member during erection can contain
at least part of the fluid drilling assembly, and when in the
erected position the arm member is able to guide the fluid cutting
device towards the borehole wall, the assembly further including at
least one sensor for monitoring the arm member or the fluid
drilling assembly.
Inventors: |
Trueman, Robert; (Brisbane,
AU) ; Meyer, Timothy Gregory Hamilton; (Brisbane,
AU) ; Stockwell, Matthew; (Brisbane, AU) |
Correspondence
Address: |
PERKINS COIE LLP
PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Family ID: |
25645442 |
Appl. No.: |
09/917612 |
Filed: |
July 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09917612 |
Jul 27, 2001 |
|
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|
09445161 |
Dec 6, 1999 |
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Current U.S.
Class: |
175/45 ; 175/263;
175/61; 175/62 |
Current CPC
Class: |
E21B 47/09 20130101;
E21B 7/061 20130101; E21B 7/18 20130101 |
Class at
Publication: |
175/45 ; 175/61;
175/62; 175/263 |
International
Class: |
E21B 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 1997 |
AU |
P0 7264 |
Claims
1. An erectable arm assembly for use in a borehole, the erectable
arm assembly comprising a main body and an arm member, the arm
member movable between a collapsed position in which the assembly
can be removed from the borehole and an erected position, the arm
assembly being adapted to house a fluid drilling assembly
comprising a fluid cutting device and a flexible hose drill string
such that during erection the arm member can contain at least part
of the fluid drilling assembly, and when in the erected position
the arm member is able to guide the fluid cutting device towards
the borehole wall, the assembly further including at least one
sensor for monitoring the arm member or the fluid drilling
assembly.
2. The assembly of claim 1, wherein the fluid cutting device can be
retracted into the arm member.
3. The assembly of claim 2, wherein a said sensor is adapted to
detect when the fluid cutting device has been retracted into the
arm member.
4. The assembly of claim 3, wherein the sensor comprises an
electromagnetic sensor which is adapted to detect the presence of
the fluid cutting device.
5. The assembly of claim 3, wherein the sensor comprises an
electric sensor which is adapted to the presence of the fluid
cutting device.
6. The assembly of claim 1, wherein a said sensor is adapted to
detect the angle of erection of the arm member relative to the main
body.
7. The assembly of claim 6, wherein the sensor comprises a tilt
transducer.
8. The assembly of claim 6, comprising an hydraulic or pneumatic
ram for moving the arm member between the collapsed position and
erected position, the arm member being attached at one end to the
main body and at the other end to the arm member and wherein the
sensor is adapted to determine the extension of the ram.
9. The assembly of any one of the preceeding claims, including
guides to guide the flexible hose drill string through the main
body and the arm member.
10. The assembly of claim 9, wherein a said sensor is able to
detect the position and/or direction of travel of the flexible hose
drill string.
11. The assembly of claim any one of the preceding claims, which
further includes a compass for detecting the azimuth of the arm
member.
12. The assembly of any one of the preceding claims, wherein the
arm member is formed from at least two arm members coupled together
to provide a larger degree of curvature for a drill string
13. The assembly of claim 1, wherein the arm member has at least
one fluid cutting nozzle thereon to cut a slot in the bore wall as
the arm is erected, the at least one nozzle being adapted to be
connected to a supply of high pressure fluid.
14. The assembly of any one of the preceding claims, wherein the
main body is elongate and the arm member is pivotally attached to
the main body such that it can move about a pivot axis between the
collapsed and the erected position.
15. The assembly of claim 14, wherein the arm member in the
collapsed position sits entirely within or substantially within the
main body.
16. A method for forming at least one lateral borehole from an
existing borehole, the method comprising lowering an erectable arm
assembly into the borehole to a desired position, the assembly
having a main body and an erectable arm member, positioning a
self-advanceable fluid cutting device to be supported by the arm
member at least as the arm member is erected, operating the fluid
cutting device to self advance the fluid cutting device from the
arm member and into the side wall of the borehole to form a lateral
bore in a direction dictated by the position of the arm member in
the borehole.
17. An erectable arm assembly for use in a borehole, the assembly
comprising a main body and an arm member which can move between a
collapsed position where the assembly can be installed and removed
from the borehole, and an erected position where the arm member can
guide a fluid drilling assembly towards the borehole wall.
18. The assembly of claim 17 wherein when the arm member is in the
erected position, the main body and the arm member define a guide
for turning the fluid drilling assembly through an angle of about
90.degree. within a radius of less than about 300 mm.
Description
FIELD OF THE INVENTION
[0001] This invention relates to an erectable arm assembly for use
in boreholes, and particularly relates to an assembly which can
direct a fluid cutter into the borehole wall.
BACKGROUND ART
[0002] Whipstocks are well known in the mining and petroleum
industries and are used to change the direction of a drill hole
(directional drilling). Since the earliest times, boreholes were
made to deviate by placing tapered wedges or "whipstocks" in the
borehole to force the bit sideways into a new direction, and it is
well known that different bottom-hole assemblies had a tendency
either to increase or decrease the inclination of the hole. No one
drilling method is satisfactory for all radii of curvature. It is
therefore customary to distinguish among these as long-, medium-,
short-, and ultra-short-radius methods. The invention relates to
ultra-short-radius methods which are typically defined to have a
radius of 2 ft. (0.6 m) or less.
[0003] Directionally drilled wells fall into two main categories.
In the first category, the task is to reach locations that are not
accessible through straight, vertical holes. The objective is to
reach a substantial distance horizontally away from the drilling
location. The second category consists of wells in which part of
the well that lies in a particular oil or gas reservoir is given a
particular orientation so as to increase productivity. An example
of this second category is a vertically thin reservoir where a
horizontal hole can contact a greater part of the reservoir than a
vertical one, increasing the drainage contact area. It is this
second category to which the invention primarily relates.
[0004] Ultra-short-radius whipstocks have been developed that are
applicable to the second category of directional drilling.
[0005] A common feature of existing ultra-short-radius whipstocks
is a requirement to incorporate a device in the bottom-hole
assembly that either pushes the drill string around the
ultra-short-radius and into the deposit which is to be drilled, or
uses a complicated hydraulic piston drive arrangement. Drill
strings for use with these whipstocks are either segmented or
coiled tubing.
[0006] More elaborate devices are also known to turn a drill string
and/or cutter into the borehole wall. For instance, U.S. Pat. No.
5,197,783 describes a cavity forming device for use in boreholes
and which has an erectable arm member provided with a fluid cutting
jet to cut a large cavity in the borehole.
[0007] U.S. Pat. No. 4,497,381 describes a drill string bending
assembly which has an extending arm portion to direct the drill
string into the sidewall.
[0008] A disadvantage with existing whipstocks and other similar
assemblies is in correctly determining various parameters in the
down hole and drilling process. For instance it is necessary to
determine the distance travelled by the fluid cutter, whether the
segmented or coiled tubing drill string is feeding properly through
the bore, when the fluid cutter is properly retracted so that the
arm member can be retracted, the orientation of the arm member, the
degree of inclination of the arm member, and so on.
[0009] The assembly of the invention can be used with a drilling
system that uses a high pressure hose as a flexible hose drill
string and a self-advancing fluid jet cutting nozzle. Such a nozzle
has been described in International Application No.
PCT/AU96/00783.
OBJECT OF THE INVENTION
[0010] The present invention is directed to a method for
directional drilling of lateral boreholes from an existing
borehole, and to an assembly which can be lowered down the existing
borehole and where the assembly has an arm member which can be
erected to position a cutter and/or drill string into a side wall
of the borehole.
[0011] Optionally, the assembly can cut a slot into the side wall
of the borehole as the arm is erected.
[0012] It is an object of the invention to provide a method and
assembly which may overcome the abovementioned disadvantages or
provide the consumer with a useful or commercial choice.
[0013] In one form of the invention, there resides an erectable arm
assembly for use in a borehole, the erectable arm assembly
comprising a main body and an arm member, the arm member movable
between a collapsed position in which the assembly can be removed
from the borehole and an erected position, the arm assembly being
adapted to house a fluid drilling assembly comprising a fluid
cutting device and a flexible hose drill string such that during
erection the arm member can contain at least part of the fluid
drilling assembly, and when in the erected position the arm member
is able to guide the fluid cutting device towards the borehole
wall, the assembly further including at least one sensor for
monitoring the arm member or the fluid drilling assembly.
[0014] In a second form, the invention resides in a method for
forming at least one lateral borehole from an existing borehole,
the method comprising lowering an erectable arm assembly into the
borehole to a desired position, the assembly having a main body and
an erectable arm member, positioning a self-advanceable fluid
cutting device to be supported by the arm member at least as the
arm member is erected, operating the fluid cutting device to self
advance the fluid cutting device from the arm member and into the
side wall of the borehole to form a lateral bore in a direction
dictated by the position of the arm member in the borehole.
[0015] In a third form, the invention resides in an erectable arm
assembly for use in a borehole, the assembly comprising a main body
and an arm member which can move between a collapsed position where
the assembly can be installed and removed from the borehole, and an
erected position where the arm member can guide a fluid drilling
assembly towards the borehole wall.
[0016] In another form, the invention resides in a method for
forming at least one lateral borehole of known distance from an
existing borehole, comprising lowering an assembly in the borehole
to a desired position, the assembly having a main body and an
erectable arm member, positioning a self-advanceable fluid cutting
device to be supported by the arm member at least as the arm member
is erected, operating the fluid cutting device to self-advance the
fluid cutting device from the arm and into the side wall of the
borehole to form a lateral bore in a direction dictated by the
position of the arm member in the borehole.
[0017] It is preferred that the method comprises monitoring the
length of the lateral bore by at least one sensor on the
assembly.
[0018] The method can be used to form several lateral bores
approximately in the same plane but in different directions, and
this can be achieved by turning the assembly in the existing
borehole before launching the fluid cutter. The method may also be
used to form several lateral bores in different planes.
[0019] The method can include an assembly as described above and
having various sensors as described above.
[0020] The method and assembly can be used as a tight radius
drilling system (TRD) by which is meant that the flexible hose
drill string can be turned through 90 degrees within a short
radius, typically less than 300 mm.
[0021] The method and assembly can be used to drill multiple
lateral boreholes from a single existing borehole in the same
horizon and/or at multiple horizons, for instance to extract
methane from coal seams. The existing boreholes are typically
vertical or near vertical. The lateral boreholes generally follow
the direction of a coal seam and are typically horizontal. After
completion of the lateral boreholes, production of gas from the
well is started by lowering the water level in the existing,
borehole with a simple foot pump or the like. This technique is
extremely effective in coal seams where the methane desorption
pressure is equal to or less than the hydrostatic head of the
ground water table, as is the case for the majority of the coal
deposits in the world.
[0022] The current method and assembly can form horizontal lateral
boreholes in excess of 200 meters almost directly from the existing
borehole well. In this manner it is possible to drain a relatively
large area of coal from a single borehole. The borehole may extend
to a depth of at least 400 meters and in some cases may exceed 600
meters.
[0023] The tight radius bend helps eliminate a lot of the problems
encountered with dewatering larger radius deviated wells by
requiring only a basic foot pump inserted into the existing
borehole to drain all of the lateral boreholes branching from that
well.
[0024] The method and assembly described above are adapted
particularly but by no means exclusively for use in recovering
methane from underground deposits such as coal seams.
Alternatively, one form of the invention is a method and assembly
for recovering methane from underground deposits which incorporate
the above described method for directional drilling and the
assembly.
[0025] Suitably, the main body of the assembly is elongate and has
a prismatic configuration or tubular configuration. The main body
may have a channel like cross section.
[0026] The arm member may be pivotally attached to the main body
such that it can move about a pivot axis between its retracted
position and its extended position. It is preferred that the arm
member, in the retracted position, sits entirely within or
substantially entirely within the main body. For instance, the main
body may have an open front through which the arm member can
extend. Alternatively, the main body may be provided with a
recessed portion in which the arm member lies when the arm member
is in the retracted position.
[0027] The arm member may comprise a single member, or a number of
members coupled together. For instance, if the flexible hose drill
string, when guided through the assembly, requires a larger degree
of curvature, the arm member may be formed from two linked
members.
[0028] The arm member may comprise a single member, or a number of
separate members which can be hinged together, telescoped together,
and the like.
[0029] When the arm member is in the retracted position, it should
not form any hindrance to movement of the assembly in the
borehole.
[0030] The arm member may be moved between its retracted and
extended position by an actuator. The actuator may be located
within the main body. The actuator may comprise a hydraulic or
pneumatic ram, one end of which is attached relative to the main
body, and the other end of which is attached relative to the arm
member.
[0031] The arm member may comprise a sliding link arrangement. In
this arrangement the arm member may be hingedly coupled relative to
the body. A link member may be pivotally coupled to the arm member
and to a slide. The slide can move along a track and is coupled to
an actuator. The actuator can cause the slide to move along its
track which in turn can cause the arm member to move between its
retracted and extended positions.
[0032] It is preferred that the arm member is configured to allow
it to support a flexible hose drill string. Thus, when the assembly
is placed in position, and the arm member is moved to its extended
position, the arm member can be maintained in its extended position
and a flexible hose drill string can be passed down the existing
borehole through an upper portion of the tubular body and along the
arm member thereby positioning the drill string for lateral
borehole formation.
[0033] To achieve this, the arm member may be tubular in
configuration to allow the flexible hose drill string to pass
therethrough. Alternatively, other methods of supporting the
flexible hose drill string are envisaged such as struts, guides,
and the like.
[0034] In another form of the invention, the assembly houses a
self-advancing fluid cutting device. The fluid powered cutting
device may be self-propelled and may be steerable.
[0035] The cutting device may be connected to a flexible hose drill
string in the form of a tube or hose or combination thereof,
through which high pressure fluid can pass to provide the required
propulsion of the cutting device, and optionally also to provide
high pressure fluid to the forward nozzles.
[0036] In this form of the invention, the cutting device may be
held by the arm member, and if the arm member is tubular, may be
positioned within the arm member.
[0037] Guide members in the form of rollers, pulleys, and the like,
can be positioned within the tubular body and/or on the arm member
to guide the tube or hose through the assembly as the cutting
device moves away from the assembly. The cutting device, in an
embodiment, has a substantially tubular steel body with at least
one forwardly directing high pressure water jet cutting nozzle, and
at least one rearwardly facing thrusting jet to propel the device
in a forward direction.
[0038] The assembly can be positioned at a desired elevation in the
existing borehole and used to launch the cutting device to cut a
series of lateral boreholes. The assembly can be turned in the
borehole before the cutting device is again launched. A clamping
means can be provided to clamp the assembly in the borehole at the
desired azimuth. The clamping means may be provided on the assembly
below the arm member and may comprise an extendible member which
can be actuated to clamp the assembly against the borehole wall or
casing.
[0039] To facilitate smooth movement of the arm member, at least
one flushing jet may be provided to flush away any cuttings which
may settle on the assembly and especially around the arm member as
the cutting device is operative.
[0040] If the assembly has no self slotting capability, a cavity is
required in the existing borehole to allow the arm member to be
erected. Conventional cavity formers are well known, but these
devices are not generally able to form cavities of a precise size
and shape. If the assembly is lowered into a cavity which is too
large, and the arm member erected, the free end of the arm member
may be some distance from the cavity wall. If the fluid cutting
device is launched, it can become jammed between the end of the arm
member and the cavity wall, or can lose its desired
orientation.
[0041] Therefore a cavity reamer can be provided which can cut
cavities of sufficient accuracy to allow proper working of the
assembly. The cavity reamer may comprise a rotatable main body
which can be lowered down an existing borehole and a plurality of
erectable arm members which can be moved between a collapsed
position substantially in line with the main body, and an extending
position where the arm members contact the side wall of the
borehole, the arm members being provided with cutting means to cut
a cavity in the borehole as the reamer is rotated in the borehole,
and means to urge the arm members into the extended position.
[0042] In another variation to the invention, the arm member can
have cutting means to cut a slot into the wall of the borehole as
the arm member moves towards its extended position. In this
embodiment, the assembly can cut a slot as the arm member extends
from the main body and therefore the need for a cavity may be
eliminated or an undersized cavity may be used.
[0043] The cutting means may comprise any type of cutting means
which can cut into the side wall of the borehole as the arm member
is extended. Suitably, the cutting means comprises high pressure
fluid which may pass through one or more nozzles.
[0044] It is preferred that a number of cutting means are provided
and these may be spaced along the arm member. Suitably, the one or
more cutting means are located on a leading edge of the arm member,
that is, the edge or portion of the arm member that is proximal to
the side wall of the borehole which is to be cut.
[0045] If the cutting means comprises high pressure fluid passing
though nozzles, it is preferred that the nozzles are spaced along
the arm member such that the spacing between a first nozzle and a
second nozzle is about that of the working distance of the high
pressure fluid. That is, if the high pressure fluid is able to
efficiently cut a certain distance, the second nozzle is preferably
positioned at that distance such that high pressure fluid passing
through the second nozzle extends the cutting distance of the
combined working fluids.
[0046] A number of sensors and/or instrumentation components can be
included in order to control the drilling system. Excess feed of
high pressure hose from the surface can cause bunching at the
assembly entry. A hinge joint on one of the rollers may have a
strain gauge to measure force on the roller. This gives an
indication of tension on the high pressure hose through the
assembly. A position transducer in the hydraulic ram and a tilt
transducer in the arm member can measure the arm member
inclination. A contact or inductive sensor can be located in the
arm member to indicate the positive retraction of the drilling
assembly from the lateral borehole. Pressure transducers and
temperature gauges may be located in the assembly to measure
existing borehole hydrostatic pressure and temperature. An optical
sensor may be located in the assembly to pick up reflected light
from cuttings as they exit the lateral boreholes enabling colour
change to be assessed. An assessment of the strata in which
drilling is carried out can therefore be made.
[0047] More particularly, location of the cutting device in the arm
member can be detected by an electromagnetic sensor which detects
the presence of the steel body of the cutting device. The sensor
can be positioned in the arm member In addition to, or as an
alternative to the above electro-magnetic sensor, an electric
sensor can be provided which detects the steel body of the cutting
device by using the steel body to complete an electric circuit.
[0048] Correctly determining that the cutting device is fully
within the arm member is important to prevent jamming of the arm
member upon its retraction.
[0049] The erection angle of the arm member is important to
determine the launch angle of the cutting device within the arm
member. A sensor to determine the extension of the ram can be used
which will determine the erection angle of the arm member relative
to the main body of the assembly. In addition thereto, or
alternatively thereto, an arm member inclination sensor can be
used. This sensor can comprise a tilt transducer.
[0050] In addition to the degree of extension of the arm member
from the body portion, it is important to determine the azimuth of
the assembly to correctly position the arm member to enable lateral
boreholes to be cut around the existing borehole. In one embodiment
a compass can be used to determine the azimuth.
[0051] With the use of flexible hose as the drill string, there is
a tendency for the hose to coil or buckle in the borehole.
Therefore, the length of hose lowered into the existing borehole is
not always a good indication of the length of the lateral borehole
cut by the fluid cutter. The assembly may therefore include a
sensor to detect the speed and the direction of hose travel through
the assembly. The sensor may comprise an encoder wheel in the
assembly which is biased against the hose.
[0052] Other sensors may be provided which are not part of the
assembly but which determine various parameters of the flexible
hose drill string. For instance, a surface sensor may be provided
to determine the amount of tension in the hose feeding down the
existing borehole, and this sensor can comprise a load cell. The
hose may be wound around a hose drum which may include a load cell
to determine the tension in the hose.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] Embodiments of the invention will be described with
reference to the following drawings in which
[0054] FIG. 1 is a diagrammatic view showing a vertical borehole
and a coal seam;
[0055] FIGS. 2, 2A and 2B are views of an assembly according to an
embodiment of the invention with the arm member in a retracted
position;
[0056] FIGS. 3, 3A and 3B are views of the assembly of FIG. 2 with
the arm in an extended position.
[0057] FIG. 4 is a view of an alternative assembly having a single
linked arm member and without cutters, and in the extended
position.
[0058] FIG. 5 is a view of another assembly in the retracted
position, with fluid cutters, and with no provision for a flexible
hose drill string to pass through the arm member. (ie a pure
cutter).
[0059] FIG. 6 is a view of the assembly of FIG. 5 in the extended
position.
[0060] FIG. 7 is a view of an assembly according to a further
embodiment of the invention and which contains a number of
sensors.
[0061] FIG. 8 is a close up view of the arm member of FIG. 7.
BEST MODE
[0062] Referring to the figures, and initially to FIG. 1, there is
shown diagrammatically an ultra-short-radius drilling method and
assembly for cutting a substantially horizontal bore 63 into a coal
seam 10 from an existing vertical borehole 11.
[0063] FIG. 1 shows a vertical bore 11 pre-drilled into the ground
and extending through a coal seam 10.
[0064] An assembly 14 is shown in FIG. 1 and which is positioned in
a pre-formed slot or cavity 60 in one side of vertical borehole
11.
[0065] A self-advancing steerable fluid cutting device 16 has been
positioned substantially horizontally into coal seam 10 by virtue
of the assembly 14.
[0066] The self-advancing cutting device 16 has a tubular steel
body about 40-80 cm long and 5-15 cm in diameter. The body has a
number of rearwardly facing high pressure retro jet thrusters which
propel the cutting apparatus in a forward direction. The front face
of the cutting device is provided with one or more high pressure
water jet cutters to cut the bore. High pressure water is supplied
to the cutting device by a surface pump 61 and through a high
pressure flexible hose 62 which is attached to the rear of cutting
device 16. Hose 62 is flexible and can pass through the assembly 14
as the cutting device moves along the bore 63. To retract the
cutting device 16 it is dragged back along bore 63 by winding the
flexible hose 62 onto hose winch 18, and until the cutting device
is back in the arm member 22.
[0067] The flexible hose drill string 62 which extends to the
surface and to a high pressure pump 61 and hose winch 18. High
pressure fluid is passed through hose 62 to power the forward water
jet cutters of the device 16 and also the retro-thrusters which
propels the device forwardly and against the coal face to be cut by
the water jets.
[0068] The cutting device 16, in the retracted "at home" position,
is initially within erectable arm member 22 which can move from a
collapsed position where it is inside main body 20 of assembly 14
to an erect position as illustrated in FIG. 1. Of course, the arm
member can adopt a partially erect position, with the position of
the arm member determining the point of entry of the fluid cutting
device 16 into the cavity side wall.
[0069] Cutting device 16 can be lowered down the vertical borehole
and fed into arm member 22 when the arm member is in the collapsed
position, or can be prepositioned in arm member before the assembly
is lowered into the vertical bore. In both instances, the cutting
device 16 is in the arm member as it is raised.
[0070] As the cutting device propels itself from the arm member 22
by virtue of the retro thrusters on the cutting device, various
sensors (better described with reference to FIG. 7) detect that the
cutting device has been released from the arm member 22 and track
the distance of travel of the cutting device. The sensors also
ensure that the cutting device is fully retracted into arm member
22 before the assembly is collapsed for withdrawal from the
borehole, or for repositioning in the cavity to allow a further
lateral bore to be cut by the cutting device.
[0071] Assembly 14 is releasably locked into position by a clamping
means in the form of a borehole clamp 70. Clamp 70 is positioned on
a the centralising tail piece 64 of assembly 14 and below the
cavity 60. The clamp 70 consists of an hydraulically operated ram,
a number of link members, and an expanding mechanism which pushes
against the borehole casing thereby securing the assembly against
twisting in the vertical borehole. Hydraulic power can comprise
pressurised water.
[0072] Borehole clamp 70 prevents assembly 14 from undesired
twisting in the vertical bore as the cutting device is in
operation. As the cutting device leaves arm member 22, the high
pressure retro jets thrust against the sides of the arm member.
Should the assembly twist, the arm member will twist away from the
borehole entrance formed by the cutting device, and this can cause
a sharp bend to form in the high pressure hose which can prevent
advancement of the cutting device.
[0073] An instrument housing 19 is provided above arm member 22 to
process the data from the various sensors.
[0074] Cavity 60 should be formed with good control of the cavity
diameter to ensure that the end of arm member 22, when erect, is
against, or spaced sufficiently close to the cavity wall, to ensure
that the cutting device 16 in arm member 22 is launched correctly.
For instance, the free gap between the end of arm member 22 and the
cavity side wall should be less that half the length of the cutting
device.
[0075] The assembly of FIG. 1 is supported by a tubular steel drill
rods 17 which consists of rigid steel rods coupled together as is
known in the art. Alternatively, the assembly can be lowered down
by coiled tubing as is also known in the art. A control umbilical
bundle 65 which incorporates cables and hoses for electric,
hydraulic and water control, is strapped to tubular steel drill
rods 17 and sends sensor information from the sensors and
instruments within instrument housing 19 to the surface
computer(s).
[0076] The assembly therefore allows accurate tracking of the
position of the fluid cutter relative to the assembly.
[0077] A surface skid 9 can be provided to contain the necessary
equipment to lower and raise the assembly and to control the
cutting device 16, and the skid can contain the computers to decode
the sensor readings.
[0078] FIG. 1 is merely illustrative of the general parts and
features of the invention.
[0079] FIGS. 7 and 8 illustrate an assembly 80 provided with
various sensors and instrument packages. Like numbers have been
used to identify like parts. Assembly 80 has an arm member 22 in
which a cutting device 16 is located when the cutting device is in
the retracted position. In this embodiment, arm member 22 is
substantially enclosed to define a cage. Inside the arm member is
an electromagnetic sensor 81 which detects the presence of the
steel bodied cutting device 16 using an alternating magnetic field.
Sensor 81 is used to detect when the cutting device 16 is fully
retracted into the arm of the assembly. It should be realised that
failure to fully retract cutting device 16 before collapsing
assembly 80 can result to jamming the assembly in the vertical
borehole. Sensor 81 is positioned such that it detects the steel
body of cutting device 16 only when the cutting device is fully
retracted into arm member 22.
[0080] As a backup, a second electric sensor 82 is provided. This
sensor is also positioned on arm member 22 and detects full
retraction of cutting device 16 into the arm member by using the
steel body of the cutting device to complete an electric circuit
which in turn causes the resistivity of the circuit to drop
significantly when the cutting device makes contact with the
sensor.
[0081] Assembly 80 has an hydraulic ram 84 which extends and
collapses arm member 22. A ram position sensor 83 comprising a
linear transducer is incorporated into the ram rod. The signal from
the transducer relates directly to the extension of the ram which
can be related back to the angle of elevation of arm member 22.
[0082] As a backup to the ram position sensor 83, an arm
inclination sensor 85 is provided on arm member 22. Sensor 85 is a
tilt transducer whereby electrical resistance can be related
directly to the relative orientation of the transducer around its
central axis. Sensor 85 in combination with ram position sensor 83
allows for a redundancy in determining the arm inclination, and in
the event of mechanical failure of arm member 22, the sensors in
combination will provide some diagnostic information.
[0083] Assembly 80 further includes a compass 86. Compass 86 is a
flux-gate magnetic compass which is used to indicate the azimuth of
the front of assembly 80. Sensor 86 is electronic and is mounted at
the toe of the assembly away from magnetic material. Sensor 86 is
necessary for correctly positioning the radial lateral boreholes
around the central existing borehole. Sensor 86 will work in
combination with fibreglass casing, as steel casing will cause
false readings. A gyroscopic compass will be used in applications
with steel casing.
[0084] Assembly 80 further includes a flexible hose travel sensor
87. Sensor 87 includes an encoder wheel which is used to detect the
speed and direction of hose travel through assembly 80. In the
embodiment, sensor 87 is a roller wheel which is spring loaded
against the flexible hose. As the hose moves through the assembly,
the roller wheel rotates. A series of magnets are placed
circumferentially around both sides of the roller. Additional
sensors are situated such that the magnets pass these sensors as
the roller turns. A signal from the additional sensors can be
interpreted for speed and direction of travel of the hose. The hose
travel sensor 87 gives a good indication of whether the cutting
device 16 is penetrating into the coal seam and helps prevent
feeding too much hose from the surface hose winch 18. (Too high a
feed rate can cause bunching of the hose and risk hose damage and
jamming of the assembly in the existing borehole).
[0085] Instrument housing 19 includes circuit boards, provides a
power supply to the various sensors, receives signals from the
sensors and sends data to the surface. Instruments housing 19
contains a temperature transducer 88 to monitor the temperature
inside instrument housing 19. A pressure gauge 90 is provided to
measure hydrostatic pressure.
[0086] On the surface, other sensors can be used to determine the
amount of tension in the hose feeding down the existing borehole.
For instance, load cells may be positioned on winch drums and
supporting structures to record loads indicative of hose tension,
to ensure that the hose is not overtensioned. An additional related
sensor can be provided on the hose winch drum and can consist of a
load cell which indicates the torque provided by the hose drum
motor. This data helps determine the tension in the hose at the
surface and it compliments the load cell situated in the foot of
the goose neck.
[0087] A surface computer can be used to interpret the signals
coming from the instrumentation on the assembly and at various
places around the surface skid.
[0088] Referring now to FIGS. 2 and 3, there is illustrated in
greater detail the assembly 14.
[0089] Assembly 14 comprises a prismatic main body 20 which is
elongate and hollow throughout its length. Body 20 is half
hexagonal and open at the front in cross-section. Body 20 is sized
to allow it to be lowered down borehole 11 to a desired position,
for instance, adjacent a coal seam.
[0090] Body 20 is fully open at the front, except for some
structural stiffening members 21. This opening allows an internal
arm member 22 to extend from body 20. Arm member 22 in FIG. 2 is
positioned entirely within body 20 thereby allowing the assembly 14
to easily move along bore 11.
[0091] Arm member 22, as shown in FIG. 2, is formed from two
separate members being a first shorter arm member 23, and a second
longer arm member 22. Arm members 23, 22 are hingedly coupled
together at 24 to form a linked arm member system. The arm members
are tubular or channel-shaped to allow a flexible hose drill string
to pass therealong.
[0092] The pair of linked arm members 22, 23 provide a larger
degree of curvature to a flexible hose drill string passing down
the borehole, into body 20, along first arm member 23 and along
second arm member 22. This provides a minimum friction path and
also reduces the possibility of the flexible hose drill string
kinking, becoming caught, or being damaged as the flexible hose
drill string passes from a vertical direction to a substantially
horizontal direction.
[0093] Guides in the form of rollers and the like 36 are located
within arm members 22, 23 to assist in guiding the flexible hose
drill string along the arm members.
[0094] Arm member 22 is hingedly coupled to one end of an opposed
pair of plate members 27, the plate members being hingedly attached
at 28 to body 20, thereby allowing the arm member to move between
its extended position and its retracted position.
[0095] In a lower part of prismatic body 20 is an actuator 29 which
is in the form of a fluid ram having a ram body and a ram rod 29A,
the ram rod being able to move into and out of ram body in the
usual manner. In FIG. 3, ram rod 29A is attached to a slide block
50. Slide block 50 is mounted for sliding movement within body 20
and can slide between an upper position shown in FIG. 3 and a lower
position shown in FIG. 2. Slide block 50 is moved between its upper
and lower positions by ram 29. This is better illustrated in the
embodiment of FIG. 4.
[0096] Hingedly attached to slide block 50 is a link member 51.
Link member 51 is formed from two spaced apart link bars which nest
around arm member 22 when in the retracted position illustrated in
FIG. 2. This allows the assembly to be formed in a compact manner.
Link member 51 is pivotally attached to arm member 22 at a position
approximately mid-way along arm member 22.
[0097] Thus, when the ram is operated to extend ram rod 29A, slide
block 50 is pushed to its upper position which in turn causes link
member 51 to be pushed out of body 20, which in turn moves arm
member 22 to its extended position illustrated In FIG. 3.
Retraction of ram rod 29A causes collapse of arm member 22 back
into body 20. The actuator and link member arrangement provides a
stronger and more robust system.
[0098] Arm member 22 in the embodiment is a hollow steel member of
substantially rectangular cross section. On the upper or leading
surface 30 is a cutting means which comprises pairs, or an array of
spaced nozzles 31-34.
[0099] Nozzles 31-34 are attached to a high pressure fluid hose
(not shown) and high pressure cutting fluid can pass through the
nozzles to cut a slot or cavity in the coal seam.
[0100] Nozzles 31-34 are spaced from each other by a distance
approximating the working distance of the high pressure fluid
passing through the nozzles. In this manner, efficient cutting of a
slot in the coal seam occurs as arm member 22 is raised from the
inside of main body 20.
[0101] Inside arm member 22 are a number of guides in the form of
rollers 36. Rollers 36 function to guide the high pressure hose
which powers the self-propelled steerable jet nozzle 16 illustrated
in FIG. 1. That is, rollers 36 prevent the hose from kinking as the
hose passes from the inside of main body 20 to along the inside of
arm member 22. Further guides in the form of rollers 37 are
positioned inside main body 20 and on a pair of spaced apart plates
between which the high pressure hose which powers the
self-propelled steerable jet nozzle passes.
[0102] In use, assembly 14 is passed down bore 11 until it reaches
the desired position (within a coal seam). Water under high
pressure is then supplied to nozzles 31-34 and at the same time ram
29 is actuated to begin movement of arm member 22. Initially, the
forward portion of arm member 22 (that is, adjacent nozzles 31)
will contact the side wall of the bore and these nozzles will begin
to cut into the coal seam. High pressure water passing through
nozzles 31-34 will also begin to cut into the coal seam as arm
member 22 is further raised. The amount of movement of arm member
22 can be controlled by the degree of actuation of ram 29 and thus
arm member 22 can be raised to 90.degree. or over, but can also be
raised partially, for instance, depending on the relative dip of
the coal seam if the coal seam is not horizontal.
[0103] Once the arm member 22 has been raised to its desired
amount, high pressure water is shut off from nozzles 31-34 and a
flexible hose drill string can be lowered down existing borehole 10
and into arm member 22. The end of the drill string is provided
with a cutter, such as a fluid cutter, to then cut the passageway
into the coal seam.
[0104] In a variation, a self-advancing steerable jet nozzle can be
pre-positioned within arm member 22 before the assembly is lowered
into the borehole. In this variation, the high pressure hose which
supplies the self-propelled steerable jet nozzle is guided by
rollers 36 and 37 and passes up bore 11 to the high pressure pump
and hose winch 18. Thus, the hose forms the drill string to the
self-propelled steerable jet nozzle.
[0105] Water from the high pressure water pump 61 is supplied via
the high pressure hose to the jet nozzle 16 at up to full pressure
of 1150 bar at 234 liters per minute, thereby operating the cutting
jet or jets and propelling the retrojet or jets. The self-advancing
nozzle penetrates the coal seam, the continuous flexible hose drill
string (that is, the high pressure hose) is pulled behind it.
[0106] The self-propelled nozzle can penetrate into the seam for a
distance of up to 200 meters or more with typical drilling times of
less than two hours. The nozzle can then be retracted by winding
the high pressure hose. Ram 29 can then be actuated to return arm
member 22 back into its retracted position as shown in FIG. 2. The
assembly 14 can then be pulled up the hole, or alternatively, can
be rotated about its longitudinal axis and the arm member extended
to cut another passageway into the coal.
[0107] The assembly 14 can be attached to the surface by means of a
conventional tubular steel drill rods or some other system such as
coiled tubing. The tubular steel drill rods or tubing supports the
assembly 14 within the borehole. The drill string or tubing
provides the conduit to allow high pressure fluid to pass through
the drill string or tubing and into cutting nozzles 31-34a.
Alternatively, a flexible high pressure hose can be used to supply
water to these cutters. Rollers 36-37 provide a suitable bend
radius for the flexible hose drill string which is connected to the
self-propelled drilling nozzle 16, thereby allowing the flexible
hose drill string to feed smoothly through the assembly as the
nozzle penetrates laterally away from the assembly.
[0108] FIG. 4 illustrates an assembly 40 according to another
embodiment. In this embodiment, the assembly does not have any self
slotting capability, but does house a self-propelled fluid cutting
device in the extendible arm member. The assembly is lowered down a
borehole which has an already formed cavity in it. Assembly 40 is
similar to that described with reference to FIGS. 2 and 3 in that
it has an main elongate body 41 which is substantially hollow
throughout its length. In body member 41 is an arm member 42 which
can be moved between a retracted position (not shown) and an
extended position illustrated in FIG. 4. In the retracted position,
arm member 42 is entirely within or essentially within body member
41 to allow the assembly 40 to be lowered into a borehole.
[0109] Guides in the form of rollers and the like 46 are located
within arm member 42 and a small mostly internal arm member 43 to
assist in guiding the flexible hose drill string along main body 40
and along arm member 42 and to minimise kinking of the drill
string.
[0110] In a lower part of body member 41 is an actuator 47 which is
in the form of a fluid ram having a ram body 48 and a ram rod 49,
ram rod 49 being able to move into and out of ram body 48 in the
usual manner. Ram rod 49 is attached to a slide block 50. Slide
block 50 is mounted for sliding movement within body member 41 and
can slide between an upper position shown in FIG. 4 and a lower
position (not shown). Slide block 50 is moved between its upper and
lower positions by operation of actuator 47.
[0111] Hingedly attached to slide block 50 is a link member 51.
Link member 51 is formed from two spaced apart link bars which can
nest around arm member 42 when arm member 42 is in its retracted
position. This allows the assembly to be formed in a compact
manner. Link member 51 is pivotally attached to arm member 42 at a
position approximately mid-way along arm member 42.
[0112] Thus, when the ram is operated to extend ram rod 49, slide
block 50 is pushed to its upper position which in turn causes link
member 51 to be pushed out of main body 41 which in turn moves arm
member 42 to its extended position illustrated in FIG. 4.
Retraction of ram rod 49 causes collapse of arm member 42 back into
main body 41.
[0113] FIGS. 5 and 6 illustrate an assembly similar to the assembly
illustrated in FIG. 4 but now including fluid cutters 52-54. These
cutters are similar to the cutters and arrangement illustrated and
described with reference to FIGS. 2 and 3 except that they are
rigidly linked to a tramming hydraulic cylinder (not illustrated).
This enables nozzles 52-54 to oscillate during cutting.
[0114] In this embodiment, the assembly excludes the provision of a
drill string passing through the main body and the arm member. This
assembly simply creates the required slots and can then be removed
from the borehole after which the assembly of FIG. 4 can be
inserted to allow drilling.
[0115] An air supply to an air lift device in the foot of the
assembly may be provided to assist in removal of cuttings from the
borehole as lateral penetration of the drilling nozzle occurs, and
as the assembly forms the required slot.
[0116] In one embodiment of the TRD system, a brief description of
operation is as follows A borehole which is usually vertical is
conventionally drilled from surface (141/4" diameter), intersecting
the targeted seams for drainage. A sump of sufficient capacity to
take the cuttings from both the reaming/slotting operation and
horizontal turnouts, and to house the foot pump once the production
phase of the well commences is included. The well is lined with
95/8" casing. The casing material over the seam intersections is
fibreglass. Alternatively, other casing materials such as steel,
fibreglass, aluminium or PVC may be used. The casing is cemented
into position. A conventional oilfields hole opener is lowered down
to the bottom seam intersection and the casing and cement removed.
The hole opener is retrieved and a modified marine casing cutter is
lowered down the hole and a cavity reamed to a diameter suitable to
allow full erection of the assembly such as over the full interval
of the seam. Some coal may be left in the roof of the cavity if
this improves the stability of the cavity. This procedure is
repeated for all seams to be drained.
[0117] Once the cavities have been formed the TRD skid is moved
into position adjacent to the collar of the well. The assembly is
attached to 23/8" EUE tubing and the flexible hose drill string is
threaded through the assembly such that the water jet nozzle is
housed in the erectable arm. The control bundle is attached to the
assembly and a check made on the functionality of the assembly and
its associated instrumentation. The assembly is then lowered down
the hole by means of the tubular steel drill rods. The high
pressure hose and control bundle are fed down at the appropriate
speed. The control bundle is strapped to the drill rods at regular
intervals such that its weight is fully supported. Centralisers are
added every 10 m to provide a low friction path for the passage of
the flexible hose drill string once horizontal drilling
commences.
[0118] Upon reaching the seam to be drained the assembly is
orientated to the correct azimuth by means of the onboard compass
and is clamped against the borehole wall and the arm is erected.
This brings the water jet nozzle in close proximity to the wall of
the cavity. The preferred sequence of horizontal drilling is from
bottom to top of the existing borehole. Before commencing drilling,
the high pressure pump is brought up to full pressure (e.g. 1150
bar at 234 liters per minute). The high pressure spinning jets
emanating from the front of the nozzle commence to create a
horizontal borehole. Forward thrust is generated from the rearward
facing high pressure jets. This thrust causes the drilling assembly
to move forward into the cavity wall as high pressure hose is fed
from the drum on the surface.
[0119] In this manner, horizontal boreholes of up to 200 meters in
length are produced. Upon full extension, the pump pressure is
dropped to around 700 bar and the drilling assembly retracted back
into the erectable arm by means of the powered drum mounted on the
surface skid. The erectable arm is collapsed, the assembly
unclamped and the assembly rotated to a new azimuth direction. The
assembly arm is again clamped and the assembly arm is erected and
another horizontal hole is drilled. This process is repeated until
the required number of directional lateral boreholes are formed at
each level in each horizon. The assembly is then pulled out of the
hole. The cuttings formed during the formation of the lateral
boreholes are then cleaned from the sump by means of a reverse
circulation system.
[0120] It can be seen that the assembly, and the combination of the
assembly with a self-advancing steerable drilling assembly within
arm member 22 provides a number of distinct advantages over
conventional devices. For instance, the assembly contains an
extensive range of instrumentation to monitor the borehole
conditions and the operation of the lateral borehole formation in
the self-advancing drilling system. This leads to effective
formation of lateral boreholes to a typical distance of 200 meters
and in drilling times of less than two hours. The assembly allows
rapid repositioning to allow multiple lateral borehole creation.
This array of multiple lateral boreholes at one or more horizons is
particularly suitable for the extraction of fluids such as water
and methane through a single existing borehole.
[0121] The assembly can position the resultant cutting device more
accurately than conventional devices.
[0122] It should be appreciated that various other changes and
modifications may be made to the embodiment described without
departing from the spirit and scope of the invention
* * * * *