U.S. patent application number 14/417490 was filed with the patent office on 2015-08-13 for near-bit borehole opener tool and method of reaming.
This patent application is currently assigned to Halliburton Energy Services, Inc.. The applicant listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Eric Yves Claudey, Martin Lindgrin, Olivier Mageren, Stein Erik Moi, Svein Ravndal, Alexandre Schmitz, Mariano Talamini.
Application Number | 20150226009 14/417490 |
Document ID | / |
Family ID | 47713970 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150226009 |
Kind Code |
A1 |
Claudey; Eric Yves ; et
al. |
August 13, 2015 |
Near-Bit Borehole Opener Tool and Method of Reaming
Abstract
The present disclosure relates to a near-bit borehole opener
(reamer) tool and a method of drilling a wellbore comprising: (a)
disposing in the wellbore a tool string; (b) lowering and rotating
the tool string and drilling a first portion of the wellbore having
a first diameter with the drill bit, wherein the at least one
cutter assembly of the borehole reamer is in a closed position; (c)
reaming with the second borehole reamer a portion of the wellbore
to a second diameter larger than the first diameter, wherein a rat
hole portion of the wellbore is not reamed with the second borehole
reamer, said rat hole portion of the wellbore having the first
diameter; (d) extending the at least one cutter assembly of the
first borehole reamer; and (e) concurrently rotating and moving the
first borehole reamer up or down in the rat hole portion of the
wellbore with the first diameter and abrading and cutting away the
wellbore wall contacted by the at least one cutter assembly of the
first borehole reamer assembly, thereby enlarging the diameter of a
portion of the rat hole portion of the wellbore.
Inventors: |
Claudey; Eric Yves; (Bergen,
NO) ; Talamini; Mariano; (Mons, BE) ; Mageren;
Olivier; (Jette, BE) ; Schmitz; Alexandre;
(Marcq, BE) ; Lindgrin; Martin; (Stavanger,
NO) ; Moi; Stein Erik; (Hommersak, NO) ;
Ravndal; Svein; (Figgjo, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
47713970 |
Appl. No.: |
14/417490 |
Filed: |
June 25, 2013 |
PCT Filed: |
June 25, 2013 |
PCT NO: |
PCT/US2013/047558 |
371 Date: |
January 26, 2015 |
Current U.S.
Class: |
175/40 ; 175/61;
175/78 |
Current CPC
Class: |
E21B 10/32 20130101;
E21B 10/42 20130101; E21B 7/064 20130101 |
International
Class: |
E21B 10/32 20060101
E21B010/32; E21B 7/06 20060101 E21B007/06; E21B 10/42 20060101
E21B010/42 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2012 |
EP |
12305953.7 |
Feb 15, 2013 |
EP |
13155472.7 |
Claims
1. A method of drilling a wellbore comprising: (a) disposing in the
wellbore a tool string including a drill bit on a distal end of the
tool string, a first borehole reamer assembly having at least one
cutter assembly, said first borehole reamer disposed adjacent to
the drill bit, a downhole remote steering assembly disposed in the
tool string above and proximal to the first borehole reamer
assembly, and a second borehole reamer assembly with at least one
cutter assembly disposed in the tool string above the downhole
remote steering assembly; (b) lowering and rotating the tool string
and drilling with the drill bit a first portion of the wellbore
having a circumferential wall and a first diameter, wherein the at
least one cutter assembly of the first borehole reamer are in a
closed position; (c) reaming with the second borehole reamer a
portion of the wellbore to a second diameter larger than the first
diameter, wherein a rat hole portion of the wellbore is not reamed
with the second borehole reamer, said rat hole portion of the
wellbore having the first diameter; (d) extending the at least one
cutter assembly of the first borehole reamer; and (e) concurrently
rotating and moving the first borehole reamer up or down in the rat
hole portion of the wellbore with the first diameter and abrading
and cutting away the wellbore wall contacted by the at least one
cutter assembly of the first borehole reamer assembly, thereby
enlarging the diameter of a portion of the rat hole portion of the
wellbore.
2. The method of claim 1 further including disposing a MWD/LWD
assembly in the tool string above the downhole remote steering
assembly and below the second borehole reamer.
3. The method of claim 1 wherein the first borehole reamer and the
drill bit are joined to each other by welding before they are
disposed in the tool string.
4. The method of claim 1 wherein a body of the first borehole
reamer and a body of the drill bit are formed integrally.
5. The method of claim 1 wherein the cutter assemblies of the
second borehole reamer are opened in step (b) and steps (b) and (c)
are conducted concurrently.
6. The method of claim 1, further including: prior to beginning
step (c) pulling up the tool string out of the rat hole portion of
the wellbore and wherein in step (e) the first borehole reamer
assembly is rotated and moved in a downward direction into the rat
hole portion thereby reaming a portion of the rat hole portion to a
larger diameter.
7. A bottom hole assembly for use in a wellbore comprising: a
borehole reamer assembly including a body adapted at an upper end
to be connected to a tool string including a downhole remote
steering assembly, and adapted at a lower end to be connected to a
drill bit; said borehole reamer assembly further including at least
one cutter assembly adapted to extend in a radial direction away
from a longitudinal axis of the body, said cutter assembly further
adapted to abrade and cut away a circumferential wall of the
wellbore contacted, thereby enlarging a diameter of the wellbore in
an area contacted by the cutter assembly.
8. The bottom hole assembly of claim 7 wherein the borehole reamer
assembly adapted at a lower end to connect to a drill bit comprises
a body of the borehole reamer welded at a lower end of the body to
a drill bit body thereby forming a unitary reamer drill bit
combination tool.
9. The bottom hole assembly of claim 7 wherein a body of the
borehole reamer and a body of the drill bit are formed
integrally.
10. The bottom hole assembly of any of claim 7 wherein the tool
string further includes a MWD/LWD assembly disposed in the tool
string above the downhole remote steering assembly.
11. The bottom hole assembly of any of claim 7 wherein the tool
string further includes a second borehole reamer assembly disposed
in the tool string above the downhole remote steering assembly or
the MWD/LWD assembly.
12. The bottom hole assembly of any of claim 7 wherein the tool
string disposed above the borehole reamer assembly further includes
a second borehole reamer assembly disposed in the tool string above
both the RSS assembly and the MWD assembly.
13. The method of drilling a wellbore comprising: (a) disposing in
the wellbore a tool string including a drill bit on a distal end of
the tool string, a borehole reamer assembly having at least one
cutter assembly, said borehole reamer disposed adjacent to the
drill bit; (b) lowering and rotating the tool string and drilling a
first portion of the wellbore having a first diameter with the
drill bit, wherein the at least one cutter assembly of the borehole
reamer is in a closed position; (c) extending the at least one
cutter assembly of the first borehole reamer; and (d) concurrently
rotating and moving the borehole reamer up or down in a rat hole
portion of the wellbore with the first diameter and abrading and
cutting away a circumferential wall of the wellbore wall contacted
by the at least one cutter assembly of the borehole reamer
assembly, thereby enlarging a diameter of a portion of the rat hole
portion of the wellbore.
14. The method of claim 13 further including disposing a downhole
remote steering assembly in the tool string above and proximal to
the first borehole reamer assembly.
15. The method of claim 14 further including disposing a MWD/LWD
assembly in the tool string above the downhole remote steering
assembly.
16. The method of claim 15 further including disposing a second
borehole reamer assembly with at least one cutter assembly disposed
in the tool string above the downhole remote steering assembly.
17. The method of claim 16 further including joining the first
borehole reamer and the drill bit to each other by welding before
they are disposed in the tool string.
18. The method of claim 16 further including forming integrally a
body of the first borehole reamer and a body of the drill bit.
19. The method of claim 16 further including: prior to step (c),
reaming with the second borehole reamer a portion of the wellbore
to a second diameter larger than the first diameter, wherein a rat
hole portion of the wellbore is not reamed with the second borehole
reamer, said rat hole portion of the wellbore having the first
diameter.
20. The method of any of claim 19 further including opening the
cutter assembly of the second borehole reamer in step (b) and steps
(b) and (c) are conducted concurrently.
21. The method of any of claim 13 further including: prior to
beginning step (c) pulling up the tool string out of the rat hole
portion of the wellbore and in a step (e) rotating the first
borehole reamer and moving in a downward direction into the rat
hole thereby reaming a portion of the rat hole to a larger
diameter.
22. A bottom hole assembly for use in a wellbore comprising: a
borehole reamer assembly including a body having an attachment
structure for securing an upper end to a tool string including a
downhole remote steering assembly, said borehole reamer attachable
at a lower end to a drill bit, said borehole reamer assembly
further including at least one cutter assembly extending in a
radial direction away from a longitudinal axis of the body, said
cutter assembly further including at least one cutter element
operable to abrade and cut away a wellbore wall contacted by the
cutter, and thereby enlarge the diameter of the wellbore in the
area contacted by the cutter.
23. The bottom hole assembly of claim 22 wherein the borehole
reamer assembly comprises a unitary reamer drill bit combination
tool having a body of the borehole reamer welded at a lower end of
the body to a drill bit.
24. The bottom hole assembly of claim 22 wherein the borehole
reamer assembly comprises a unitary reamer drill bit combination
tool having an integrally formed borehole reamer body and drill bit
body.
25. The bottom hole assembly of any of claim 22 wherein the tool
string further includes a MWD/LWD assembly disposed in the tool
string above the downhole remote steering assembly.
26. The bottom hole assembly of any of claim 22 wherein the tool
string further includes a second borehole reamer assembly disposed
in the tool string above the downhole remote steering assembly or
the MWD/LWD assembly.
27. The bottom hole assembly of any of claim 25 wherein the tool
string disposed above the borehole reamer assembly further includes
a second borehole reamer assembly disposed in the tool string above
both the RSS assembly and the MWD assembly.
28. The bottom hole assembly of any of claim 22 wherein an overall
longitudinal length of the borehole reamer assembly for reaming a
167/8 diameter hole is less than or equal to 60 inches.
Description
BACKGROUND
[0001] During well drilling operations, a drill string is lowered
into a wellbore. Typically, in conventional vertical drilling
operations the drill string is rotated. The rotation of the drill
string provides rotation to a drill bit affixed to the distal end
of the drill string. If the wellbore is deviated from vertical,
some prior art drilling systems use a downhole mud motor disposed
in the drill string above the drill bit to rotate the bit instead
of rotating the drill string to provide rotation to the drill
bit.
[0002] FIG. 1A illustrates an example of a deviated wellbore
including a bottom hole assembly ("BHA") therein. A BHA 10 is shown
drilling a borehole 2 in a subterranean formation 9. Bottom hole
assembly 10 includes a drill bit 6, a first stabilizer 8, a roller
cone-type under reamer 17 and a drilling assembly 12 in the order
shown. The drilling assembly 12 includes a bent housing directional
mechanism 14 and a downhole motor 16 to directionally drill
borehole 2 with bit 6 and roller-cone type under reamer 17.
Optionally, a second stabilizer 19 may be added to BHA 10 which may
be located above (shown) or below drilling assembly 12. BHA is
illustrated creating a borehole 2 in a subterranean formation 9.
The borehole 2 includes a reduced diameter lower portion 3
sometimes referred to in the art as a "rat hole" or "pilot
hole."
[0003] FIG. 1B illustrates another example of a drilling assembly.
A BHA 25 is shown drilling a borehole 2 in a subterranean formation
9. Bottom hole assembly 25 includes bit 6, a radial piston-type
under reamer 18, and a drilling assembly 12 including a downhole
motor 16 and a bent housing directional mechanism 14. The borehole
2 includes a reduced diameter lower portion 3, sometimes referred
to in the art as a "rat hole" or "pilot hole."
[0004] In recent years, rotary steerable systems ("RSS") have been
developed to provide downhole rotation to the drill bit. In a
rotary steerable system, the BHA trajectory is deflected while the
drill string continues to rotate. As such, rotary steerable systems
include two types: push-the-bit systems and point-the-bit systems.
In a push-the-bit RSS, a group of expandable thrust pads extend
laterally from the BHA to thrust and bias the drill string into a
desired trajectory. In order for this to occur while the
drillstring is rotated, the expandable thrusters extend from what
is known as a geostationary portion of the drilling assembly.
Geostationary components do not rotate relative to the formation
while the remainder of the drillstring is rotated. While the
geostationary portion remains in a substantially consistent
orientation, the operator at the surface may direct the remainder
of the BHA into a desired trajectory relative to the position of
the geostationary portion with the expandable thrusters. An
alternative push-the-bit rotary steering system has lateral thrust
pads mounted on a body, which is connected to and rotates at the
same speed as that of the rest of the BHA and drill string. The
pads are cyclically driven, controlled by a control module with a
geostationary reference, to produce a net lateral thrust which is
substantially in the desired direction.
[0005] The rotary steerable tools are generally programmed by an
engineer or directional driller who transmits commands using
surface equipment (typically using either pressure fluctuations in
the mud column or variations in the drill string rotation) which
the RSS tools understand and gradually steer in the desired
direction.
[0006] FIGS. 2 and 2A illustrate one example of a rotary steerable
system such as Halliburton's Geo Pilot System. The system 50 may
include a flex power assembly 34 attached to a drill string 31. The
system further includes in descending order a driver 32, a
stabilizer 30, electronics module 28, hydraulics module 26,
actuator 24, compensator 22, and extended gage bit 20.
[0007] In some implementations, a drill string using an RSS System,
a lower portion of the drill string may include a measurement while
drilling (MWD) and Logging While Drilling (LWD) telemetry tool
section. MWD/LWD technology is well known in the prior art. In some
implementations, the MWD/LWD system sends downhole data on the
geologic formations penetrated by the wellbore and drilling
performance data to the surface for evaluation. Transmission of
information to or from the MWD tools typically uses mud pulse
technology or, alternatively, other information transmission
means.
[0008] In order to pass through the inside diameter of upper
strings of casing already in place in the wellbore, often times the
drill bit will be of such a size as to drill a smaller gage hole
than may be desired for later operations in the wellbore. It may be
desirable to have a larger diameter wellbore to enable running
further strings of casing and allowing adequate annulus space
between the outside diameter of such subsequent casing strings and
the borehole wall for a good cement sheath. A conventional borehole
opener (reamer) may be included in the drill string above the MWD
tools and the rotary steerable tools. Note as used herein the term
"borehole opener" is interchangeable with "under reamer." Because
of the configuration of the tool string, it is not possible for the
conventional reamer to reach the bottom of the wellbore. This
leaves a smaller gage section of borehole that is referred to as a
"rat hole" or alternatively a "pilot hole." This under gage rat
hole section may be 60 to 90 feet in length.
DETAILED DESCRIPTION
[0009] The present disclosure includes a "near-bit reamer" disposed
on the distal end of the tool string proximal to the drill bit.
This near-bit cutting structure reamer may be less robust than the
one of a primary conventional reamer (such as the reamers discussed
in the above noted prior art references) because the near-bit
reamer is only reaming the rat hole 3 portion of the wellbore that
a conventional reamer cannot reach.
[0010] Referring now to FIG. 3, wherein one implementation of a
tool string 100 including a near-bit borehole enlargement tool 200
is illustrated. Note as used herein the terms "borehole enlargement
tool" and "borehole opener tool" are used interchangeably. The tool
string 100 is attached to a drill string 101 that is suspended from
a drilling rig (not shown). The tool string may include a
conventional under reaming tool 104, e.g., a Halliburton model XR
Reamer or UR type conventional under reamer.
[0011] In some implementations, below the conventional reamer 104
is disposed a Measurement While Drilling (MWD) tool string and/or a
Logging While Drilling (LWD) Tool string section generally denoted
as element 120. The MWD/LWD tool section 120 may include a HOC P4M
Pulser 112 which is a communication device to receive RSS and MWD
tool instructions and send data to a surface communication
means.
[0012] The MWD/LWD tool section 120 may include one or more in-line
stabilizer elements 114, 118 and 122. The MWD/LWD tool section 120
further includes elements 116 and 124 that receive information on
downhole data of the geologic formations penetrated by the wellbore
and drilling performance data and transmit that data to the surface
for evaluation, typically using mud pulse technology or other data
transmission means.
[0013] Below the MWD tool section 120 is a flexible sub 130.
[0014] Disposed below the flexible sub 130 is the RSS tool string
denoted generally as 140. For an exemplary RSS tool string, see
FIG. 2.
[0015] In the present disclosure, below the RSS tool section 140
and the MWD/LWD tool section 120 is a near-bit reamer 200 which is
disposed proximal to a conventional drill bit 150 that is disposed
on the distal end of the tool string 100.
[0016] Referring to FIG. 4, therein is illustrated another
embodiment of the present disclosure wherein the near-bit borehole
enlargement tool ("NBR") and drill bit are integrally combined as
element 360. In some implementations the fishing necks of an NBR
tool are removed and the conventional pin and box connection of the
NBR and drill bit are removed and the NBR tool is welded to the
drill bit. (It will be understood that it is not necessary to
modify actual existing NBR tools and drill bits to construct the
combination tool 360. The elements of such a combination tool 360
may be manufactured and constructed in accordance with the design
elements disclosed herein.) It will be understood that welding is
only one method of securing the bit body to the reamer body. The
bodies may be integrally cast as a single body or machined from a
single casting or forging. Alternatively, the two bodies may be
secured by other conventional connection means.
[0017] The alternative tool string 300 includes a conventional
reamer 304. Various crossover subs and stabilizers 318 and 322 are
disposed above the MWD tool 320 (e.g., Halliburton Evader Gyro).
The MWD/LWD tool section 120 may include a HOC P4M Pulser 312 which
is a communication device to receive RSS and MWD tool instructions
and send data to a surface communication means.
[0018] Below the MWD tool section is a flexible sub 330.
[0019] Disposed below the flexible sub 330 is a RSS tool denoted
generally as 340 (e.g., Halliburton Geo-pilot tool). Detailed
information on Halliburton's Geo-pilot system is contained in
Appendix A.
[0020] In the present disclosure, below the RSS tool section 340 is
an optional stabilizer sub 326. The combination bit and reamer 360
includes a short near-bit borehole enlargement tool (NBR) 362
welded to the body of a roller cone or PDC bit 364 disposed on the
distal end of the tool string 100.
[0021] It will be understood that the present disclosure is not
limited to the Halliburton product elements described above. The
Halliburton product elements included herein are exemplary products
that may be used in the subject disclosure. However, other products
of a similar nature manufactured by other manufacturers may be used
as elements in the subject disclosure.
[0022] FIGS. 5A and 5B illustrate an enlarged perspective view of
an exemplary combination near-bit hole opener (reamer) and drill
bit 360. The combination tool 360 includes a near-bit reamer 362
that includes a body section 361. The overall length L.sub.1 of the
body section is 40 inches or smaller. The overall length of the NBR
tool 360 is L.sub.2 of 60 inches or smaller. The reamer 362
includes a plurality of cutter elements 368 disposed on radial
pistons 369 disposed inside the body 361. When the reamer 362 is
actuated, the cutter elements 368 are moved radially outward from a
central longitudinal axis 301 of the reamer 362 and contact the
borehole wall. (It will be understood that other configurations of
cutter elements may be used in the near-bit hole enlargement tool
of the present disclosure.) As the reamer 362 is rotated by the
rotation of the drill string 101, the cutter elements 368 abrade
and cut away the formation, thereby expanding the diameter of the
borehole.
[0023] Mechanical elements of a conventional near-bit reamer are
illustrated in FIG. 10 (e.g., Halliburton NBR tool). The
conventional NBR includes a box connection 1001, a pin connection
1002, a body 1006 portion of approximately 167/8 inches diameter
and an overall length L.sub.5 of 14.33 inches, a cutter 1010 is
disposed on a piston that is adapted to move radially out of the
body 1006 to engage the borehole wall. The overall diameter L.sub.6
is about 167/8 inches.
[0024] FIGS. 6A, 6B and 6C illustrate another embodiment of a
combined near-bit borehole enlargement tool 460. The combination
tool 460 includes a drill bit 464 and a near-bit reamer 462 that
includes a body section 461. The reamer 462 includes a plurality of
cutter elements 468 disposed on radial pistons disposed inside the
body 461. When the reamer 462 is actuated, the cutter elements 468
are moved radially outward from a central longitudinal axis 401 of
the reamer 462 and contact the borehole wall. (It will be
understood that other configurations of cutter elements may be used
in the near-bit hole enlargement tool of the present disclosure.)
As the reamer 462 is rotated by the rotation of the drill string
101, the cutter elements 468 abrade and cut away the formation,
thereby expanding the diameter of the borehole. For a combination
tool 460 sized to ream a hole diameter of 17.5 inches to an opening
of 20 inches, the overall length L.sub.3 of the body section 461 is
about 40 inches. The overall length of the combination tool 460 for
reaming a 20 inch hole is L.sub.4 about 60 inches or smaller.
[0025] FIGS. 7 and 8 illustrate additional embodiments of the
present disclosure wherein the body 761, 861 of the near-bit
borehole enlargement tool 760 and 860 has spiral body design
including spiral water courses 764 and 864 disposed in the outside
of the body. The spiral water course provides the benefits over a
linear longitudinal exterior water course of:
[0026] a. Optimized stabilization
[0027] b. Reduction of BHA vibrations, hence increasing cutter's
lifetime
[0028] c. Better cleaning performance
[0029] The present disclosure further includes a method of using
the near-bit borehole enlargement tool 200, 360, 460, 760 and 860
to open the reduced diameter portion rat hole 3 of the borehole
4.
[0030] It will be understood that other implementations of a
combination bit and reamer may be used in the near-bit borehole
enlargement tool of the present disclosure.
[0031] It is important to note that it is not desirable to place a
conventional reamer directly above the bit and below the RSS and
MWD/LWD for several reasons. In some conventional reamers a ball
(plug) is pumped down the drill string and landed in the under
reamer which activates the reamer arms. Placement of a conventional
reamer below the RSS and MWD/LWD may prevent the ball/plug from
passing through the RSS and MWD/LWD tools and reaching the
conventional reamer to activate it. Additionally, it is not
desirable to place a conventional under reamer below the RSS and
MWD tools because the conventional under reamer is too long to
allow the RSS tool to steer and/or propel itself properly.
[0032] Further, it is not desirable to place a conventional reamer
below the RSS and LWD tools and ream as it is being drilled (to
eliminate the creation of a rat hole) because the RSS and MWD/LWD
tool strings need to be in contact with the wellbore walls in order
to function. The RSS needs to contact the wellbore wall to direct
the steering and it is desirable for the MWD/LWD tools to have the
sensor elements of the tools in proximity to the borehole wall in
order to obtain better quality formations data.
[0033] Additionally, it is not feasible to use a larger gage bit on
the bottom to drill an oversized hole (to eliminate the creation of
a rat hole) because the RSS and MWD/LWD tool strings need to be in
contact with the wellbore walls in order to function. The RSS needs
to contact the wellbore wall to direct the steering and it is
desirable for the MWD/LWD tools to have the sensor elements of the
tools in proximity to the borehole wall in order to obtain better
quality formations data (to eliminate the creation of a rat hole)
because the RSS and MWD/LWD tool strings need to be in contact with
the wellbore walls in order to function. The RSS needs to contact
the wellbore wall to direct the steering and it is desirable for
the MWD/LWD tools to have the sensor elements of the tools in
proximity to the borehole wall in order to obtain better quality
formation data.
[0034] In prior art systems, in order to eliminate the rat hole,
the entire drill string and tool string would have to be pulled
from the wellbore and a trip would have to be made in the hole with
a full gage bit or under reamer with a bull plug in the end and run
to the bottom to drill/ream out the 60 to 90 foot rat hole section.
This trip in and out of the wellbore with the drill string and an
under reamer/larger gage bit to eliminate the rat hole costs many
thousands of dollars of rig time.
[0035] Referring now to FIG. 9A, wherein is illustrated a
simplified schematic of the tool string 100 and near-bit reamer
200, 360, 460, 760 and 860 of FIGS. 5A, 5B, 6A to 6C, 7 and 8. FIG.
9A illustrates a conventional reamer 104 with cutting arms extended
and wherein the upper portion 5 of borehole 4 has been reamed out
to a desired larger gage than the lower reduced diameter portion
under gage rat hole portion 3. The tool string 100 is disposed in
the lower end of drill string 101. The tool string includes a
conventional under reamer 104, an RSS section 140 and MWD section
120, the near-bit reamer 200 and the bit 150. As can be seen, the
conventional reamer cannot reach the bottom of borehole 4 to
enlarge the rat hole portion 3 of the hole because the reamer is
disposed above the RSS section 140, the MWD section 120.
[0036] FIG. 9B illustrates the tool string 100 pulled up/back into
the larger gage reamed portion of the borehole 4 and the
conventional reamer's arms are closed and the near-bit reamer's
cutting pads 208 are extended. (It will be understood that closing
the conventional reamer's arms is optional because leaving the
conventional reamer's arms open may provide stabilization for the
bottom hole assembly as the near-bit borehole enlargement tool 200
is reaming down the rat hole in FIG. 9C).
[0037] FIG. 9C illustrates the tool string 100 after it has been
rotated and moved back down the borehole 4 to enlarge the gage of a
portion of the formerly reduced gage rat hole section 3.
[0038] It will be understood that the present disclosure can be
implemented without pulling up the tool string 100 out of the rat
hole and then lowering the near-bit reamer with extended cutters to
ream the hole by moving downward into the rat hole while the reamer
is being rotated. Instead, the cutters of the near-bit reamer may
be extended while the near-bit reamer is in the rat hole portion of
the hole and the tool string rotated and pulled upward to ream the
rat hole in an upward direction.
[0039] Note: The terms "raised" and "lowered" have been used herein
to describe movement of the tool string; however, if the borehole 4
is deviated (e.g., horizontally, as wellbore 2 is illustrated in
FIGS. 1A and 1B), raising the tool string 100 would be understood
to mean moving the drill string away from the distal end of the
borehole 4 and lowering would be understood to mean moving the tool
string 100 toward the distal end of the borehole 4.
[0040] Note: FIGS. 9A, 9B and 9C are schematics that illustrate the
cutters as pads on a piston; however, in other implementations the
near-bit reamer may have arms with a reaming cone on each arm.
Likewise, the upper conventional reamer 104 may have arms and
roller cones or extendable pads.
[0041] In reaming operations for the rat hole section 3 of borehole
4, the tool string is pulled up out of the reduced diameter rat
hole 3, and in some implementations circulation of mud is increased
from a first flow rate during drilling with the conventional under
reamer to a second predetermined flow rate which shears pins in the
NBR reamer and opens the NBR cutters 208. The cutters 208 are
extended away from the longitudinal axis 201 of the near-bit tool
200. The drill string is rotated and lowered back into the under
gage rat hole section 3 and the near-bit reamer enlarges the under
gage rat hole section. See FIGS. 9B and 9C.
[0042] Advantages:
[0043] The near-bit borehole enlargement tool (NBR) 200, 360, 460,
760 and 860 may be used in combination with a conventional under
reamer (e.g., the Halliburton XR or UR reamer). When used in a tool
string combination including a conventional under reamer, the "NBR"
may remain dormant during reaming work performed by the
conventional reamer disposed above the MWD/LWD tools and the RSS
tool. The "NBR" may be activated when the total depth of a section
of the wellbore is reached to ream the rat hole section. The NBR
combination with the conventional reamer provides using the
conventional reamer to ream long distances in the borehole due to
its robust cutting structure. The NBR of the present disclosure is
very compact (made much shorter than the original "NBR") to reduce
the rat hole distance at the bottom of a wellbore. The NBR tool of
the present disclosure further provides:
[0044] 1. Easy steerability, as a function of the short length;
[0045] 2. Alternative helical stabilizing blades and helical mud
ways instead of straight shape for: [0046] a. Optimized
stabilization; [0047] b. Reduction of BHA vibrations, hence
increasing cutter's lifetime; and [0048] c. Better cleaning
performance.
[0049] 3. Monobloc product for: [0050] a. Stronger tool
(possibility to eliminate the API connection between the Bit and
the Reamer); [0051] b. Cutting structure drilling performance
optimization (combination of XR or UR and NBR concept); [0052] c.
Tool simplicity and parts count reduction; and [0053] d. Stronger
bit/reamer connection. Reduced loads (bending, side forces, and
vibration) decrease connection failure risk.
[0054] 4. NBR structure better stabilized by means of the bit
proximity to the reamer.
[0055] 5. NBR gets better well contact coverage (combination of the
bit and the NBR might be close to 360.degree.). [0056] a. Perfect
pilot hole fitting; [0057] b. Suppress kick-off risk; [0058] c.
Reduce BHA vibrations; [0059] d. Increase cutting efficiency; and
[0060] e. Increase cutter lifetime.
[0061] 6. Eliminates rig time and saves money--in prior art systems
in order to eliminate the rat hole, the entire drill string and
tool string would have to be pulled from the wellbore and a trip
would have to be made in the hole with a full gage bit or under
reamer with a bull plug in the end and run to the bottom to
drill/ream out the 60 to 90 foot rat hole section. This trip in and
out of the wellbore with the drill string and an under
reamer/larger gage bit to eliminate the rat hole costs many
thousands of dollars of rig time.
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