U.S. patent application number 10/544512 was filed with the patent office on 2006-03-16 for downhole tool.
Invention is credited to Jacques Orban.
Application Number | 20060054354 10/544512 |
Document ID | / |
Family ID | 9952754 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054354 |
Kind Code |
A1 |
Orban; Jacques |
March 16, 2006 |
Downhole tool
Abstract
A downhole tool comprising: an axial drive unit (10) having a
connection for an electric power cable extending up the borehole,
and including an anchoring mechanism (12, 16) operable in the
borehole between a first configuration in which the anchoring
mechanism resists rotational and axial movement of the unit, and a
second configuration in which the anchoring mechanism is moveable
axially in the borehole, an axial drive mechanism that moves the
anchoring mechanism axially down the borehole when in the second
configuration; a motor (28) mounted on the drive unit at the
downhole end thereof; an hydraulic pump (30) connected to the
motor, the pump providing a source of hydraulic power; and a
functional unit connected below the hydraulic pump and powered
thereby, operation of the axial drive mechanism acting to move the
functional unit axially down the borehole.
Inventors: |
Orban; Jacques; (Garches,
FR) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
200 GILLINGHAM LANE
MD 200-9
SUGAR LAND
TX
77478
US
|
Family ID: |
9952754 |
Appl. No.: |
10/544512 |
Filed: |
February 4, 2003 |
PCT Filed: |
February 4, 2003 |
PCT NO: |
PCT/EP04/01167 |
371 Date: |
August 4, 2005 |
Current U.S.
Class: |
175/40 ;
175/107 |
Current CPC
Class: |
E21B 4/18 20130101; E21B
7/061 20130101; E21B 23/14 20130101 |
Class at
Publication: |
175/040 ;
175/107 |
International
Class: |
E21B 47/00 20060101
E21B047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 11, 2003 |
GB |
0303019.4 |
Claims
1. A downhole tool comprising: (i) an axial drive unit (10) having
a connection for an electric power cable extending up the borehole
(14), and including anchoring mechanism operable in the borehole
between a first configuration the which resists rotational and
axial movement of the unit, and a second configuration in which the
anchoring mechanism is moveable axially in the borehole, an axial
drive mechanism that moves the anchoring mechanism axially down the
borehole when in the second configuration; wherein the downhole
tool further comprises: (ii) a motor mounted on the drive unit at
the downhole end thereof; (iii) an hydraulic pump connected to the
motor, the pump providing a source of hydraulic power; and (iv) a
functional unit connected below the hydraulic pump and powered
thereby, operation of the axial drive mechanism acting to move the
functional unit axially down the borehole.
2. A tool as claimed in claim 1, further comprising an orienting
unit that allows axial rotation of at least part of the tool below
the drive unit.
3. A tool as claimed in claim 1, further comprising a diverting
member positioned below the functional unit and which acts to urge
the functional unit in a predetermined direction on operation of
the drive mechanism.
4. A tool as claimed in claim 1, wherein the hydraulic pump uses
fluid in the borehole to provide the source of hydraulic power.
5. A tool as claimed in claim 1, wherein the functional unit is a
well construction device.
6. A tool as claimed in claim 5, wherein the well construction
device comprises a drilling assembly.
7. A tool as claimed in claim 6, wherein the drilling assembly
includes a drilling motor that is powered by the hydraulic power
supply from the pump.
8. A tool as claimed in claim 7, further comprising a drill bit
that is drive by the drilling motor.
9. A tool as claimed in claim 7, the drilling motor is connected to
the pump by a hollow drill shaft through which the hydraulic fluid
flows.
10. A tool as claimed in claim 9, further comprising at least one
support member mounted o the drill shaft to support against
buckling when drilling.
11. A tool as claimed in claim 6, further comprising at least one
baffle arranged to direct drilled cuttings down the well below the
tool.
12. A tool as claimed in claim 6, further comprising a cuttings
catcher positioned below the drilling unit and attached to the tool
for catching material drilled by the drilling unit.
13. A tool as claimed in claim 12, further comprising diverters
located above and below the drilling unit to force the cuttings
into the catcher.
14. A tool as claimed in claim 13, further comprising a circulation
tube extending between the diverters to allow fluid to circulate
back up the borehole one the cuttings have been removed.
15. A tool as claimed in claim 6, further comprising a measurement
unit located in the drilling unit.
16. A tool as claimed in claim 6, further comprising an inflatable
packer above the drilling tool which, when inflated, allows
pressure isolation of at least the portion of the borehole in which
the drilling tool is located.
17. A tool as claimed in claim 5, wherein the well construction
unit comprises a completion unit.
18. A tool as claimed in claim 17, wherein the well construction
unit comprise a tubular completion member that can be advanced into
the borehole by operation of the drive unit and disconnected so as
to remain in place when the tool is withdrawn from the
borehole.
19. A tool as claimed in claim 18, wherein the completion member is
filled with a completion fluid that is pumped out of the completion
member and into the borehole around the completion member by means
of the hydraulic pump.
20. A tool as claimed in claim 1, further comprising a storage unit
located in the borehole in which at least one functional unit can
be stored when not in use.
21. A tool as claimed in claim 20, further comprising a latching
system for disconnecting the functional unit stored in the storage
unit from the remainder of the tool.
22. A tool as claimed in claim 1, further comprising an imaging
device for locating the portion of the borehole at which the tool
is to operate.
Description
[0001] The present invention relates to downhole tools, in
particular tools that are used in boreholes such as oil, water or
gas wells, or the like.
[0002] In the construction and treatment of underground boreholes
there are a number of basic techniques that are used for the
conveyance and operation of tools in the borehole. In drilling, for
example, a drill bit is fixed at the lower end of a drill string
formed from a series of hollow drill pipes connected end-to-end. By
rotating the drill string at the surface, or by using a downhole
motor, the bit is caused to rotate and this, together with weight
applied to the bit allows drilling to progress. To remove the
drilled material and assist in the drilling process a drilling
fluid, typically known as "mud", is pumped down the inside of the
drill string to exit at the drill bit and carry drilled material
("cuttings") back to the surface in the annulus around the outside
of the drill string. The drilling fluid also provides support to
the borehole and balances the pressure of fluids in the formation
due to the hydrostatic pressure created by the column of fluid. In
a development of this technique, a motor, typically in the form of
a Moyno (positive displacement) device is installed in the drill
string just above the bit. The motor is driven by the flow of mud
and can be used to rotate the drill bit independently of the
rotation of the drill string. This technique, in combination with a
bent downhole assembly ("bent sub") and an orientation sensor
allows the direction of drilling to be controlled. For straight
drilling, the technique of rotating the drill string is used
("rotary drilling") together with rotating the drill bit with the
motor. To change direction, rotary drilling is stopped, the bent
sub is oriented so that the bit face points towards the intended
direction by rotating the drill string from the surface and
drilling recommenced using the downhole motor to rotate the bit and
by applying weight to the bit from the surface through the drill
string ("sliding mode drilling"). When the borehole has attained
the desired direction, rotary drilling recommences.
[0003] Measuring devices can also be provided in the lower part of
the drill string ("bottom hole assembly" or "BHA"). These devices,
for example measurement while drilling ("MWD") devices for
measurements relating to the drilling processes: weight on bit,
ROP, direction and inclination, or logging while drilling ("LWD")
devices for formation-related measurements: resistivity, nuclear
measurements, acoustic measurements, can provide data to the
surface via memory devices removed when the BHA is withdrawn from
the borehole, via an electric cable running inside the drill
string, or by mud-pulse telemetry in which pressure pulses created
in the drilling mud by means of a siren located in the BHA are
detected at the surface.
[0004] Any activities that involve the use of a drill string
require the presence of a drilling rig at the surface. Also, the
time taken to run the string into and pull the string out of the
well is relatively long, especially in very deep wells.
[0005] Once the borehole has been drilled, measuring devices can be
lowered into the borehole on cables that provide electric power and
data communication ("wireline", "electric line", "slick line")
between the downhole tool and the surface. Such operations do not
require the use of a drilling rig and can be conducted relatively
quickly. However, to date it has only been possible to conduct
drilling operations using a wireline unit on a small scale in view
of the difficulty in providing power, torque and weight on bit
downhole. Coring is one example of a drilling activity that has
been conducted by a wireline system. In coring, a cylindrical drill
bit is used to extract a solid core of material from the rock
surrounding the borehole which is returned to the surface for
analysis. An example of a wireline coring unit is shown in U.S.
Pat. No. 4,354,558. Other wireline devices have been proposed for
drilling relatively small holes laterally from a main borehole. All
of these devices provide only relatively short drain holes and all
suffer from the problem of providing torque and weight on bit,
especially where it is necessary to drill through metallic casing
in the borehole before drilling onto the rock. One approach, as
shown in U.S. Pat. No. 6,167,968, involves separating the action of
drilling or milling through the casing using a short stiff mill
section from the action of drilling into the rock using a flexible
drill section. In another technique, the flexible drill shaft is
surrounded by a series of discs which provide support and allow
pressure to be applied to the drill bit. This is shown in U.S. Pat.
No. 6,276,453. Another approach which separates the provision of
thrust and torque is shown in U.S. Pat. No. 5,687,806.
[0006] EP 1 247 936 describes a wireline tool that can be run
inside drill pipe and used to obtain cores by drilling outside the
drill string via a side exit mandrel in the bottom hole assembly.
In this device, a packer is inflated inside the drillpipe and an
electronics an piston sub is positioned above the packer, and a
drilling motor and core bit is positioned below the packer. The
piston provides weight on the bit by driving through a sliding seal
in the packer and torque is provided by diverting mud flow from the
inside of the drillstring into the drilling motor below the packer.
The drilling mud and cuttings return to the surface via the annulus
in the lateral core hole and the annulus in the main hole in the
normal manner. The packer in this arrangement serves as a reaction
point for the weight on bit and torque applied during the drilling
process. It also causes the drilling mud to flow through the motor.
However, because it is necessary to provide a sliding seal through
the packer, the design is limited in its ability to provide an
extended drilling depth. Also, it is essential that there is a
supply of drilling mud from the surface and an annulus for the
return of the drilling mud and the cuttings.
[0007] One particular use of such drilling tools, is that of
re-entry drilling in which further drilling operations are
conducted in an existing well for the purposes of improving
production, remediation, etc. A review of such techniques can be
found in Hill D, Nerne E, Ehlig-Economides C, and Mollinedo M
"Reentry Drilling Gives New Life to Aging Fields," Oilfield Review
(Autumn 1996) 4-14. One particular tool described is the VIPER
Coiled Tubing Drilling System which comprises a drilling head
module with connectors for a wireline cable, a logging tool
including an number of sensors and associated electronics, an
orienting tool including a motor and power electronics, and an
drilling unit with a steerable motor. While the system is provided
with power and data via a cable, it is also necessary to provide a
coiled tubing to push the tool along the well.
[0008] It is an object of the present invention to provide a
downhole tool that can be run on wireline and which has the ability
to provide sufficient weight on bit and torque to achieve effective
drilling.
[0009] In accordance with the present invention, there is provided
a downhole tool comprising: an axial drive unit having a connection
for an electric power cable extending up the borehole, and
including an anchoring mechanism operable in the borehole between a
first configuration in which the anchoring mechanism resists
rotational and axial movement of the unit, and a second
configuration in which the anchoring mechanism is moveable axially
in the borehole, an axial drive mechanism that moves the anchoring
mechanism axially down the borehole when in the second
configuration; an electric motor mounted on the drive unit at the
downhole end thereof; an hydraulic pump connected to the motor, the
pump providing a source of hydraulic power; and a functional unit
connected below the hydraulic pump and powered thereby, operation
of the axial drive mechanism acting to move the functional unit
axially down the borehole.
[0010] Preferably an orienting unit is positioned below the drive
unit that allows axial rotation of at least part of the tool below
the drive unit, so allowing any asymmetry in the functional unit to
be oriented in a specific direction. A diverting member, such as a
kick plate, can be positioned below the functional unit to urge the
unit in a predetermined direction on operation of the drive unit to
advance the functional unit down the borehole.
[0011] The borehole will typically be filed with a fluid and the
hydraulic pump can preferably use this as the hydraulic fluid
supply which provides the hydraulic power.
[0012] The functional unit can have a number of possible functions:
drilling, well completion, measurement, stimulation, remediation,
etc. and any combination of these functions. Where the functional
unit has a drilling function, it preferably comprises a drilling
motor that is powered by the hydraulic fluid from the pump. The
drilling motor is typically connected to the pump (which is driven
by the electric motor) by means of a hollow drill shaft through
which the fluid flows and by means of which the drive unit urges
the drilling unit forwards. A drill bit can be connected to the
drilling motor.
[0013] By appropriate use of the kick plate and/or a bent sub in
the drilling tool (for example, the bent sub is oriented in a plane
substantially perpendicular to that of the kick plate with the bit
facing away from the plate), the drill bit can be caused to drill
away from the borehole. The extent of drilling away from the
borehole is determined by the length of the drill shaft.
Preferably, at least one support is provided on the drill shaft to
avoid buckling during drilling.
[0014] In order to prevent drilled material blocking the well or
causing the tool to become stuck, a cuttings catcher can be
positioned below the drilling unit and attached to the tool, such
that the catcher, typically a bag or storage tube, can be withdrawn
from the well with the tool on the wireline cable. Diverters, e.g.
rubber cups, can be located above and below the drilling unit to
force the cuttings into the catcher. In such a case, it is
preferred to provide a circulation tube to allow fluid to circulate
back up the borehole one the cuttings have been removed.
Alternatively one or more baffles can be provided to direct flow
containing cuttings down the borehole below the tool to avoid
sticking.
[0015] The drilling unit can also include measurement units and,
optionally, inflatable packers for providing pressure isolation of
parts of the borehole. This latter feature can be useful in making
formation pressure measurements using the tool.
[0016] An alternative form of functional unit can comprise an
completion unit. This will typically comprise a tubular completion
member, for example a casing or screen that can be advanced into
the borehole, typically with the assistance of a properly
positioned kick plate or whipstock, and disconnected so as to
remain in place when the tool is withdrawn from the borehole. The
completion member can be filled with a completion fluid, for
example a cement slurry or gravel pack that is pumped out of the
completion member and into the borehole around the completion
member by means of the hydraulic pump.
[0017] The tool can further comprise a storage unit located in the
borehole in which at least one functional unit can be stored when
not in use. In such a case, it is preferred that a latching system
is provided for disconnecting the functional unit stored in the
storage unit from the remainder of the tool.
[0018] One further embodiment of the tool comprises an imaging
device for locating the portion of the borehole at which the tool
is to operate.
[0019] The present invention will now be described by way of
examples, as shown in the accompanying drawings, in which:
[0020] FIG. 1 shows common features of first embodiment of the
present invention;
[0021] FIG. 2 shows the embodiment of FIG. 1 configured for
drilling;
[0022] FIGS. 3a and 3b shows the embodiment of FIG. 2 in different
stage of a drilling operation;
[0023] FIG. 4 shows a second embodiment of the invention configured
for drilling;
[0024] FIG. 5 shows a third embodiment of the invention configured
for drilling and measurement;
[0025] FIG. 6 shows a fourth embodiment of the invention configured
for drilling and pressure measurement;
[0026] FIGS. 7a and 7b shows a fifth embodiment of the invention
configured for completion in different stages of operation and
[0027] FIG. 8 shows a sixth embodiment of the invention configured
for multiple operations.
[0028] Referring now to the drawings, there are shown therein a
number of embodiments of the present invention. While these
embodiments are all described in the context of an open borehole,
it will be appreciated that this can also be a cased borehole, or
includes drill string or production tubing. All of these senses are
included in the use of the term "borehole". Also, in the context of
a borehole and the arrangement of the tool, the terminology used is
"up" for the direction towards the surface, and "down" for the
direction away from the surface, even if the borehole in question
is not vertical. A first embodiment of the invention is shown in
FIG. 1 and comprises a drive unit 10 including a connection for a
wireline cable (not shown). The drive unit 10 is essentially a
tractor unit such as is described in U.S. Pat. No. 5,954,131.
However, in the configuration shown here, it is situated at the top
of the tool string and serves to push the tools along the borehole
rather than pull them behind it. Futhermore, wiring is provided to
allow power and data to be provided below the unit 10.
[0029] The drive unit operates by extending locking members 12
positioned at one end of the unit 10 against the walls of the
borehole 14. Corresponding locking members 16 are provides at the
other end of the drive unit 10, but in this first configuration,
these are not locked against the borehole 14. The portion of the
drive unit between the locking members 12, 16 comprises and
extending and contracting mechanism 18. This mechanism 18 is
operated to urge the lower part of the drive unit down the
borehole. Once the full extent of the mechanism 18 is reached, the
unit is advanced by locking the lower members 16 against the
borehole 14, unlocking the upper members 12 from the borehole 14,
and contracting the mechanism 18 so as to drag the upper portion of
the unit down the well. This cycle can be repeated as often as is
required. When it is desired to run the tool into a vertical part
of the well, or to withdraw the tool from the well, both sets of
members 12, 16 are unlocked and the tool moves down by gravity or
is pulled back to the surface by the cable in the usual manner.
[0030] Immediately below the drive unit 10 is located an orienting
sub 20. This is essentially the same as that used in the VIPER
coiled tubing drilling system described above. The orienting sub
includes a motor and allows relative axial rotation between parts
of the tool above and below the sub.
[0031] A control sub 22 is located below the orienting sub 20. The
control sub 22 includes a number of functions for control of the
tool, including power supply and control, a telemetry system,
system control logic and the like.
[0032] Below the control sub 22 (or possibly forming part of the
control sub 22) is a navigation sub 24. This can include
accelerometers, magnetometers, and/or gyros for determining the
position and orientation of the tool in the borehole 14. Suitable
sensors include the GPIT inclinometer tool of Schlumberger, or the
navigation sensors o the VIPER tool described above. The navigation
sub can be placed above the orienting sub. In this case, an
indexing function is required to register the relative position of
the tool parts below the orienting sub relative to the navigation
sub.
[0033] A pumping unit 26, comprising an electric motor 28 driving a
Moyno (positive displacement) pump 30, is located below the
navigation sub 24. The sizes and powers of the electric motor 28
and pump 30 are selected according to operational limitations. For
example, the power of the motor 28 will be determined by the amount
of power available over the wireline cable and the maximum size
limitation of the tool string to be able to pass through the
borehole, production tubing or the like. The output from the pump
30 will be affected by the power output from the motor 28, the
speed of the motor 28, and again, the operational size limitations.
The pump has an inlet 32 at its upper end to allow borehole fluid
to enter the pump, and an outlet 34 at its lower end from which the
fluid is pumped to provide the hydraulic power supply.
[0034] The functional unit of the invention is attached at the
outlet end 34 of the pump 30. FIGS. 2-7 show a functional unit in
the form of a drilling tool. As is shown in FIG. 2, a drill shaft
36 in the form of small diameter drill pipe (e.g. 1.5'') is
connected to the output of the pump 30. The length of this shaft
will determine the maximum length of any lateral hole drilled-from
the main borehole 14. A drilling motor 38 is located at the lower
end of the shaft 36. This drilling motor 38 is typically a Moyno
device (similar to the pump 30, except that in this configuration,
it is driven by the fluid flow entering the motor, arriving from
the pump 30 via the drill pipe 36). The drilling motor 38 is
typically relatively small (21/8'' or 23/8'') and will usually
include a bend in the housing as is known in directional drilling
practises. It is particularly preferred to use a flex motor with
bend housing to build enough angle in a short distance to produce
effective lateral holes from the main borehole 14.
[0035] A drill bit 40 (e.g. 2.4'') is attached to the drilling
motor 38 in the normal manner.
[0036] A kick plate 42 is positioned below the drill bit but
connected directly to the upper part of the drive unit 10 by means
of a support 43. The kick plate 42 comprises a plate or other
planar surface that is angled relative to the borehole axis and
serves to urge the drill bit against the borehole wall in a
specific direction. In operation, the kick plate functions in a
similar manner to a whipstock, as will be described below. The
support 43 is connected to the drive unit by means of a lockable
sliding connection 44. A swivel 46 is provided part way along the
support 43 to allow the kick plate 42 to be oriented in the
borehole by operation of the orienting sub 20. Functioning of the
kick plate 42 is described in more detail below.
[0037] In use, the tool is lowered into the well on a wireline
cable until the desired depth is reached. At this point the drive
unit 10 is locked by operation of the upper locking members 12 and
the electrical pumping unit 26 is activated. The fluid ("mud") from
the main well 14 is pumped into the small drill-pipe 36. The mud
flows in the drill pipe 36 and reaches the motor 38, which rotates
the bit 40.
[0038] Before starting drilling, the orienting sub 20 insures that
the bend of the drilling motor 38 and the kick-plate 42 are facing
towards the proper direction (often called "tool-face"). Axial
displacement and weight on bit ("WOB") are delivered by the drive
unit 10.
[0039] This combination technique allows the drill-bit 40 to be
pushed into the formation and to drill a curved hole thanks to the
bent drilling motor 38. The bend angle is chosen so that the
lateral borehole 50 turns through 90 degrees over its length
(typically around 100 ft) as is shown in FIGS. 3a and 3b. Mud
circulation in lateral hole 50 is provided by the pumping unit 26
in the main hole 14, via the small drill-string and bit. Cuttings
are lifted in the lateral hole 50 and brought into the main hole 14
by the mud and deposited in a cuttings catcher device as described
below in relation to FIG. 4.
[0040] When the drilling of one lateral hole 50 is completed and if
the cutting catcher bag is not full, the wireline electrical drill
system can be moved to another depth and another lateral hole can
be started.
[0041] The kick-plate 42 is a guidance plate disposed at an angle
to the axis of the main hole 14. The plate 42 acts as a whipstock
to generate side force on the bit 40 and to push the bit into the
formation. This kick-plate 42 is typically hung onto the drive unit
10 by a sliding connection 44. The kick-plate 42 can be held at a
fixed position in the borehole 14, or at a fixed distance from the
static part of the drive unit 10 when starting the kick-off
drilling. During the first push displacement of the drive unit 10,
after the upper part of the drive unit 10 has been locked in the
borehole, the bit 40 is pushed into contact with the kick-plate 42.
Once the drill bit 40 has started to penetrate the borehole wall to
form the lateral hole 50, the kick-plate 42 may move away from the
entry point when the drive unit 10 is repositioned in the borehole
14.
[0042] In an alternative, the kick-plate is held by two support
tubes parallel to the drill-sting. These tubes slide into the
connection 44 on the drive unit 10 and a swivel is used as
described above. The connection for the support tubes is attached
to the middle or upper section of the drive unit. Sliding movement
of the support tube in the connection can be controlled by a lock
system in the connection, as follows: [0043] a) At the beginning of
the drilling of a new lateral hole, the drive unit contracts to
bring the upper and lower parts together, and then locks its upper
part in the hole, while releasing its lower part. [0044] b) The
locking system for the kick-plate support tubes is blocked. This
fixes the tube with respect to the upper part of the drive unit
[0045] c) The drive unit then starts to extend. This pushes the
bottom section (including drill-string) towards the bottom. The bit
hits the kick-plate and a radial displacement is generated, forcing
the bit into the formation. [0046] d) When the bit is entered
sufficiently into the side formation, the locking system for
support tube can be released. In some cases, it may be required
with some options to keep the kick-plate at the initial position
relative to the borehole rather than relative to the drive unit
during the complete drilling operation of the lateral hole.
[0047] A further embodiment of the invention is shown in FIG. 4
which ensures that well section around the kick plate 42 is
hydraulically isolated. This isolation is achieved by two rubber
cups 52, 54 (alternatively by two packers) that seal in the
borehole 14 above and below the drilling section. This isolation
forces the mud flowing out of the lateral hole 50 during drilling
to be forced into a cutting catcher bag 56 attached to the lower
cup 54. When moving the tool in the wellbore, the rubber cups or
the packers are retracted or deflated.
[0048] The cuttings catcher 56 comprises a large bag attached at or
near the kick-plate 42. This bag collects cuttings brought by the
mud out of the lateral hole 50 during drilling. In a preferred
arrangement, the bag 56 extends below the kick-plate 42 as is shown
in FIG. 4. A filling mechanism allows proper circulation of the
cuttings (with mud flow return to ensure proper filling), for
example a "bellows" type bag which is attached to the lower cup 54.
A circulation tube 58 is attached between the cups 52, 54. The bag
56 is porous so that mud can pass through while cuttings are
retained, the mud passing back up the tube 58 and into the borehole
14 near the pump unit 26. Alternative arrangements comprise porous
tubes to catch the cuttings in place of the bag, or an arrangement
of baffles that direct cuttings down the borehole 14 below the tool
if it is not necessary to be able to re-enter the lower part of the
borehole.
[0049] The drill-pipe 36 between the pump unit 26 and the motor 38
is under compression to transmit axial force from the drive unit 10
onto the drill-bit 40 and ensure Weight-On-Bit (WOB). The diameter
of the pipe will typically be small (probably between 1 to 1.75''),
and the pipe length can be around 150 ft. Up to 3 tons WOB may be
required in some drilling applications. Such an axial load can
generate buckling effects in the drill pipe. In large diameter
boreholes, large deformations of the drill pipe may occur which can
be detrimental to the drill pipe structure and drilling process. To
avoid buckling the drill pipe 36 in the large hole section, pipe
guides 60 can be installed at various distances along the pipe 36.
These guides can comprise cross-shaped members with dimensions
similar to the diameter of the main hole. The pipe 36 slides in the
guides 60. The guides 60 can be connected to each other by flexible
couplings 62 such that the maximum separation is limited. At the
upper end, the couplings 62 are connected to the drive unit 10, and
at the lower end to the to the kick-plate 42.
[0050] WOB is generated by the drive unit 10, which preferably
operates at constant force rather than constant speed. It is
controlled to reduce WOB quickly when the drilling motor 38 stalls
(which can be detected by real-time pump pressure monitoring).
[0051] A small logging (measurement) sub 64 can be inserted between
the drill-pipe 36 and the motor 38, as is shown in FIG. 5. This sub
64 can have an OD typically around 2 3/8'' while having a internal
bore of approximately 1'' for the internal mud flow. This sub can
contain at least the minimum components to support the
measurements, and is linked to the control sub 22 below the drive
unit 10. Communication can be based on wiring or by wireless
telemetry. This control sub 22 controls the measurement sub 64 and
transmits data to the surface over the wireline cable
[0052] The measurement sub 64 can include the following functions:
[0053] Resistivity measurement. This can be electrode-based
(lateralog), induction coil-based, or toroid antenna-based.
Localized electronics may be provided for measurements while
limiting cross-talk effect. [0054] Inclinometer to determine the
inclination of the lateral hole. [0055] Mini gamma-ray detector.
[0056] Pore pressure measurement behind the damage zone as is shown
in FIG. 6. An inflatable packer 66 can be provided to isolate the
annulus of the lateral hole 50. A pressure gauge is installed
inside the drill string 36 below the pumping unit 26. During the
measurement, the packer 66 seals the small annulus 50, while the
pump 30 is run in the reversed mode to "empty" the small wellbore
50 near the bit 40. This allows the measurement of formation
pressure. If the pump 30 used for drilling is not able to generate
a pressure low enough near the bit 40, a piston pump (not shown)may
be used in parallel for large pressure reduction (a valve is
required to isolated the drilling pump).
[0057] The integrated logging, drilling methods allows to determine
the profile of the logged data versus radial distance from the
wellbore. High resolution characterization can be achieved
perpendicularly to the main wellbore.
[0058] The ability to re-enter in the small lateral hole 50 after
withdrawing the tool from the borehole 14 may be important. Since
depth and orientation measurements may be insufficient, borehole
images may be required (from electrical or ultrasonic imaging
tools, such as the FMI, OBMI or UBI tools of Schlumberger). These
images allow the operator to visualize the small radial hole (which
will appear as a long ellipse in the borehole wall). For this
application, the drill system should insure "thoughwiring" so that
the imaging tool can be installed below the kick-plate. Logging
upwards is initially performed to locate the small hole. When
located, the drive unit 10 is used to lower the bit 40 to the
proper depth (and at the proper orientation). Improved positioning
of the device to re-enter in the lateral and the offset of depth
between the imaging system and the device can be measured by the
drive unit displacement.
[0059] In the embodiment of the invention shown in FIGS. 7a and 7b,
the drilling configuration of the tool described above is replaced
by a completions function. In the case shown, a liner 70,
pre-loaded with cement slurry 72 and provided with plugs at the top
74 and bottom 76 is connected at the end of a drill pipe 73 and is
run into the hole 14 and advanced into the lateral hole 50 using
the drive unit 10 and kick plate 42 in a similar manner to that
described above in relation to the drilling function. When the
liner 70 is positioned in the lateral hole 50 (FIG. 7b), the
pumping unit 26 is operated to pump the upper plug 74 down inside
the liner to force the lower plug 76 out (or to shear a seal at the
lower end of the liner) and force the cement slurry into the
annulus around the liner 70 in the lateral hole 50, where it is
allowed to set. The liner 70 can then be disconnected from the
drill pip 73 and the tool withdrawn from the borehole 14. If the
liner 70 extends from the lateral hole 50, it may be necessary to
mill the portion protruding from the borehole wall. This can be
done with a special tool or with a suitable functional unit
attached to the tool of the present invention.
[0060] Other completion options are also available, as follows:
[0061] a) The liner can be a slotted liner. [0062] b) The
completion can consist of a filter with gravel-pack. Again, the
packing gravel will be contained inside the filter for the running
in hole and pumped out in the same manner as described above for
cementing. In this case, it will be necessary to provide a
temporary liner inside the screen to allow the pack to be pumped
out of the end of the screen. [0063] c) Intelligent completion with
integrated valve and measurement systems.
[0064] In some application, it may critical to perform multiple
operations within one run in the main hole. One example could be
the drilling of one lateral and installation of permanent sensor in
the lateral.
[0065] For this application, a two head system can be used.
Initially, the system is oriented so that the drill bit is facing
the-proper direction for the lateral. After drilling, the orienting
sub turns the drill head by 180 degrees (without the kick-pad). In
this case, a clutch is provided to decouple (when required) the
rotation of the drill head from the kick-pad. The other head is
then positioned in front of the kick-pad, ready to enter the
lateral hole. This can be the permanent installation system for the
lateral, for example.
[0066] FIG. 8 shows an embodiment of the invention configured for
multiple operations. The kick pad 42 is provided with a clutch
system for rotation (or not) with the orienting sub 20 and the
drilling motor. Furthermore, the kick pad can be equipped with two
or more storage barrels 80, 81 to hold the motor and other
functional elements items when unlatched.
[0067] For this application, the motor 38 is connected to the
drill-pipe 36 by a latch system 82 controlled from the control sub
22. This allows unlatching of the motor 36 so as to be left in the
large kick-pad barrel 80. The drill-pipe latch 82 can then be
guided to another small barrel 80 in the kick pad 42. This small
barrel 80 can be loaded with a different functional unit 84
terminated by a latch system 82. This allows the drill-pipe 36 to
latch onto this item. The tool can then be used to push the
functional unit 84 into the lateral hole 50 and install it
permanently as described above (if required).
[0068] The present invention can also be adapted for use in cased
hole. In such a use, a first trip to the proper location may be
required with a mill to open a window in the casing, after which
drilling and/or other operations can be conducted as described
above.
[0069] When the tool is to be used through production tubing,
variations may also be required. For example, a wireline fishable
whipstock may be needed instead of the kick plate. Also, a tool
such as a multi-finger calliper tool might replace the imaging tool
used to locate the hole in the casing.
* * * * *