U.S. patent application number 11/510265 was filed with the patent office on 2008-09-11 for downhole tool with closed loop power systems.
This patent application is currently assigned to Western Well Tool, Inc.. Invention is credited to Norman Moore.
Application Number | 20080217024 11/510265 |
Document ID | / |
Family ID | 38926436 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080217024 |
Kind Code |
A1 |
Moore; Norman |
September 11, 2008 |
DOWNHOLE TOOL WITH CLOSED LOOP POWER SYSTEMS
Abstract
A tool for moving within a passage comprises an elongated body;
a closed system for converting a circulating flow of a fluid into
movement of the tool within the passage, and a pump-powering
assembly configured to power the pump, the pump-powering assembly
comprising one of a turbine and an E-line controlled motor. The
closed system comprises a gripper assembly on the body, a barrel
surrounding and engaged with the body, a piston longitudinally
fixed with respect to the body, a valve assembly, and a pump
configured to circulate the fluid through the closed system. The
gripper assembly is configured to utilize fluid pressure to grip
onto an inner surface of the passage. The barrel is longitudinally
movable with respect to the body, and the gripper assembly is
longitudinally fixed with respect to the barrel. The barrel and the
body define an annular space therebetween, wherein one or more
interfaces between the barrel and the body are sealed to
substantially prevent escape of fluid from the annular space to an
exterior of the barrel. The piston is positioned within the barrel
and fluidly separates the annular space into aft and forward
chambers of the barrel, wherein sizes of the aft and forward
chambers of the barrel vary as the piston moves longitudinally
within the barrel. The valve assembly is configured to direct fluid
to and from (1) the gripper assembly and (2) the aft and forward
chambers of the barrel to produce movement of the body within the
passage.
Inventors: |
Moore; Norman; (Aliso Viejo,
CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Western Well Tool, Inc.
1150 N. Tustin Avenue
Anaheim
CA
92807
|
Family ID: |
38926436 |
Appl. No.: |
11/510265 |
Filed: |
August 24, 2006 |
Current U.S.
Class: |
166/382 ;
166/212; 166/65.1; 166/66.4; 166/68 |
Current CPC
Class: |
E21B 23/001 20200501;
E21B 4/18 20130101; E21B 41/0085 20130101 |
Class at
Publication: |
166/382 ;
166/068; 166/066.4; 166/212; 166/065.1 |
International
Class: |
E21B 23/08 20060101
E21B023/08 |
Claims
1. A tool for moving within a passage, comprising: an elongated
body; a closed system for converting a circulating flow of a fluid
into movement of the tool within the passage, the closed system
comprising: a gripper assembly on the body, the gripper assembly
configured to utilize fluid pressure to grip onto an inner surface
of the passage; a barrel surrounding and engaged with the body, the
barrel being longitudinally movable with respect to the body, the
gripper assembly being longitudinally fixed with respect to the
barrel, the barrel and the body defining an annular space
therebetween, wherein one or more interfaces between the barrel and
the body are sealed to substantially prevent escape of fluid from
the annular space to an exterior of the barrel; a piston
longitudinally fixed with respect to the body, the piston
positioned within the barrel, the piston fluidly separating the
annular space into aft and forward chambers of the barrel, wherein
sizes of the aft and forward chambers of the barrel vary as the
piston moves longitudinally within the barrel; a valve assembly
configured to direct fluid to and from (1) the gripper assembly and
(2) the aft and forward chambers of the barrel to produce movement
of the body within the passage; and a pump configured to circulate
the fluid through the closed system; and a pump-powering assembly
configured to power the pump, the pump-powering assembly comprising
a turbine.
2. The tool of claim 1, wherein the body has an internal fluid
chamber, the body configured to be secured to a fluid conduit so
that an open-system fluid flowing through the conduit flows into
the internal fluid chamber of the body, the turbine configured to
receive the open-system fluid flow through the internal fluid
chamber of the body, the turbine having an output shaft configured
to rotate as the open-system fluid flows through the turbine,
wherein rotation of the output shaft powers the pump.
3. The tool of claim 2, wherein the pump-powering assembly further
comprises: a generator operatively connected to the output shaft of
the turbine so that rotation of the output shaft causes the
generator to produce electricity; and a motor configured to be
powered by electricity generated by the generator, the motor
operatively connected to power the pump.
4. The tool of claim 2, wherein the pump-powering assembly further
comprises a gearbox operatively connected between the pump and the
output shaft of the turbine.
5. The tool of claim 2, wherein the fluid conduit is coiled
tubing.
6. (canceled)
7. A method comprising: providing an elongated body within a
passage; providing a closed system comprising: a gripper assembly
longitudinally movably engaged with the body and configured to
utilize fluid pressure to grip onto an inner surface of the
passage; a propulsion assembly configured to utilize fluid pressure
to propel the body within the passage when the gripper assembly
grips the inner surface of the passage; and a valve assembly
configured to direct fluid to and from the gripper assembly and the
propulsion assembly to produce movement of the body within the
passage; providing a flexible conduit extending from the body and
in fluid communication with an internal chamber of the body;
pumping a first fluid through the flexible conduit and the internal
chamber of the body; and converting kinetic energy of the first
fluid into power for powering a pump, the pump in turn powering a
flow of a second fluid within the closed system, the second fluid
flow powering movement of the body within the passage; wherein
power provided by the second fluid to power movement of the body
within the passage is substantially linearly proportional to a flow
rate of the first fluid through the flexible conduit.
8. The method of claim 7, wherein converting kinetic energy of the
first fluid into power for powering the pump comprises: conveying
the first fluid through a turbine downstream of the flexible
conduit, the turbine driving a generator that produces electrical
power; and powering the pump with the electrical power produced by
the generator.
9. The method of claim 7, wherein converting kinetic energy of the
first fluid into power for powering the pump comprises: conveying
the first fluid through a turbine downstream of the flexible
conduit, thereby producing rotation of an output shaft of the
turbine; and utilizing the rotating output shaft to power the
pump.
10. The method of claim 9, wherein utilizing the rotating output
shaft to power the pump comprises using a gear reduction
operatively connected between the output shaft and the pump.
11. An apparatus, comprising: an elongated body having an internal
chamber and being configured to be positioned within a passage; a
flexible fluid conduit with a distal end connected to the body in
fluid communication with the internal chamber; a first pump
connected in fluid communication with a proximal end of the
flexible conduit, the first pump configured to pump a first fluid
into the flexible conduit; a closed system for converting a
circulating flow of a second fluid into movement of the body within
the passage, the closed system comprising: a gripper assembly on
the body, the gripper assembly configured to utilize fluid pressure
to grip onto an inner surface of the passage; a barrel surrounding
and engaged with the body, the barrel being longitudinally movable
with respect to the body, the gripper assembly being longitudinally
fixed with respect to the barrel, the barrel and the body defining
an annular space therebetween, wherein one or more interfaces
between the barrel and the body are sealed to substantially prevent
escape of fluid from the annular space to an exterior of the
barrel; a piston longitudinally fixed with respect to the body, the
piston positioned within the barrel, the piston fluidly separating
the annular space into aft and forward chambers of the barrel,
wherein sizes of the aft and forward chambers of the barrel vary as
the piston moves longitudinally with respect to the barrel; a valve
assembly configured to direct fluid to and from (1) the gripper
assembly and (2) the aft and forward chambers of the barrel to
produce movement of the body within the passage; and a second pump
configured to circulate the second fluid through the closed system
to thereby power movement of the body within the passage; and a
pump-powering assembly downstream of the flexible conduit, the
pump-powering assembly configured to convert a flow of the first
fluid into power for the second pump, such that the power for the
second pump is substantially linearly proportional to an output
flow rate of the first fluid from the first pump.
12. The apparatus of claim 11, wherein the pump-powering apparatus
comprises a turbine through which the first fluid flows.
13. The apparatus of claim 12, wherein the pump-powering apparatus
further comprises a generator driven by the turbine to produce
electrical power, the second pump configured to be powered by the
electrical power produced by the generator.
14. The apparatus of claim 12, wherein the turbine includes an
output shaft that rotates as the first fluid flows through the
turbine, the output shaft powering the second pump.
15. The apparatus of claim 14, wherein the pump-powering apparatus
further comprises a gearbox operatively connected between the
output shaft and the second pump.
Description
INCORPORATION BY REFERENCE
[0001] The present application incorporates by reference the entire
disclosures of U.S. Pat. Nos. 6,003,606 (entitled "PULLER-THRUSTER
DOWNHOLE TOOL"); 6,347,674 ("ELECTRICALLY SEQUENCED TRACTOR");
6,241,031 ("ELECTRO-HYDRAULICALLY CONTROLLED TRACTOR"); 6,679,341
("TRACTOR WITH IMPROVED VALVE SYSTEM"); 6,464,003 ("GRIPPER
ASSEMBLY FOR DOWNHOLE TRACTORS"); and 6,715,559 ("GRIPPER ASSEMBLY
FOR DOWNHOLE TRACTORS"). The present application also incorporates
by reference the entire disclosures of U.S. Patent Application
Publication Nos. 2004/0168828 ("TRACTOR WITH IMPROVED VALVE
SYSTEM"); and 2005/0247488 ("ROLLER LINK TOGGLE GRIPPER AND
DOWNHOLE TRACTOR"). The present application also incorporates by
reference the entire disclosure of U.S. Provisional Patent
Application No. 60/781,885, filed Mar. 13, 2006 ("EXPANDABLE RAMP
GRIPPER").
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to tools for
conducting operations within passages, and specifically to tools
for borehole intervention and/or drilling.
[0004] 2. Description of the Related Art
[0005] U.S. Pat. No. 6,003,606, entitled "Puller-Thruster Downhole
Tool," discloses an innovative self-propelled tool or tractor for
drilling, completion, stimulation, and intervention that pulls a
drill string and simultaneously thrusts itself and its payload
downhole and/or into a casing or borehole formation. The '606
patent discloses a tractor that includes one or more gripper
assemblies (e.g., bladders or packerfeet) that grip onto an inner
surface of a borehole or casing, and one or more propulsion
assemblies that propel the tractor body forward when at least one
of the gripper assemblies is gripping the borehole. A valve system
directs a fluid (e.g., drilling mud, intervention fluid, hydraulic
fluid) to and from the gripper assemblies and propulsion assemblies
to power movement of the tractor.
[0006] The '606 patent discloses two basic types of tractor
configurations--open loop and closed loop. The open loop system
uses an externally provided fluid as a medium of hydraulic
communication within the tractor. The open loop consists of a
ground surface pump, tubing extending from the pump into a
borehole, a tractor within the borehole and connected to the
tubing, and an annulus between the exterior of the tractor and an
inner surface of the borehole. The fluid is pumped down through the
tubing to the tractor, used by the tractor to move and conduct
other downhole operations, and then forced back up the borehole
through the annulus. The tractor is powered by differential
pressure--the difference of the pressure at the point of intake of
fluid to the tractor and the pressure of fluid ejected from the
tractor into the annulus. In the open loop system, a portion of the
fluid is used to power the tractor's movement and another portion
of the fluid flows through the tractor for various downhole
purposes, such as hole cleaning, sand washing, acidizing, and
lubricating of a drill bit (in drilling operations). Both portions
of the fluid return to the ground surface through the annulus.
[0007] The '606 patent also discloses a closed loop configuration
in which a hydraulic fluid is circulated through the gripper
assemblies and propulsion assemblies to power the tractor's
movement within the borehole. In particular, FIG. 19 of the '606
patent discloses a downhole motor that powers the recirculation of
the hydraulic fluid.
[0008] The '606 patent further discloses, in FIG. 24, an embodiment
in which an electrical line (referred to herein as an "E-line") is
provided within the coiled tubing. The E-line can be utilized to
send electrical signals from the ground surface to the tractor to
control the position of a start/stop valve that regulates the
inflow of drilling fluid into the tractor's valve assembly, in an
open loop system.
[0009] U.S. Pat. Nos. 6,347,674; 6,241,031; and 6,679,341, as well
as U.S. Patent Application Publication No. 2004/0168828, disclose
alternative valve systems and methods for directing fluid to and
from a downhole tractor's gripper assemblies and propulsion
assemblies for moving the tractor.
SUMMARY
[0010] In one aspect, a tool for moving within a passage is
provided. The tool comprises an elongated body; a closed system for
converting a circulating flow of a fluid into movement of the tool
within the passage, and a pump-powering assembly configured to
power the pump, the pump-powering assembly comprising one of a
turbine and an E-line controlled motor. The closed system comprises
a gripper assembly on the body, a barrel surrounding and engaged
with the body, a piston longitudinally fixed with respect to the
body, a valve assembly, and a pump configured to circulate the
fluid through the closed system. The gripper assembly is configured
to utilize fluid pressure to grip onto an inner surface of the
passage. The barrel is longitudinally movable with respect to the
body, and the gripper assembly is longitudinally fixed with respect
to the barrel. The barrel and the body define an annular space
therebetween, wherein one or more interfaces between the barrel and
the body are sealed to substantially prevent escape of fluid from
the annular space to an exterior of the barrel. The piston is
positioned within the barrel and fluidly separates the annular
space into aft and forward chambers of the barrel, wherein sizes of
the aft and forward chambers of the barrel vary as the piston moves
longitudinally within the barrel. The valve assembly is configured
to direct fluid to and from (1) the gripper assembly and (2) the
aft and forward chambers of the barrel to produce movement of the
body within the passage.
[0011] For purposes of summarizing the invention and the advantages
achieved over the prior art, certain objects and advantages of the
invention have been described herein above. Of course, it is to be
understood that not necessarily all such objects or advantages may
be achieved in accordance with any particular embodiment of the
invention. Thus, for example, those skilled in the art will
recognize that the invention may be embodied or carried out in a
manner that achieves or optimizes one advantage or group of
advantages as taught herein without necessarily achieving other
objects or advantages as may be taught or suggested herein.
[0012] All of these embodiments are intended to be within the scope
of the invention herein disclosed. These and other embodiments of
the present invention will become readily apparent to those skilled
in the art from the following detailed description of the preferred
embodiments having reference to the attached figures, the invention
not being limited to any particular preferred embodiment(s)
disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic diagram of a conventional coiled
tubing tractor system.
[0014] FIG. 2 is a schematic diagram of a turbine-powered motor for
a closed loop system for powering a downhole tractor, according to
an embodiment of the invention.
[0015] FIG. 3 is a more detailed schematic diagram of the closed
loop system of FIG. 2.
[0016] FIG. 4 is a schematic diagram of an E-line powered motor for
a closed loop system for powering a downhole tractor, according to
an embodiment of the invention.
[0017] FIG. 5 is a more detailed schematic diagram of the closed
loop system of FIG. 4.
[0018] FIG. 6 is a schematic diagram of a turbine-powered pump for
a closed loop system for powering a downhole tractor, according to
an embodiment of the invention.
[0019] FIG. 7 is a more detailed schematic diagram of the closed
loop system of FIG. 6.
[0020] FIG. 8 is a schematic diagram of a system in which a
positive displacement motor powers a pump for a closed loop system
for powering a downhole tractor, according to an embodiment of the
invention.
[0021] FIG. 9 is a more detailed schematic diagram of the closed
loop system of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] FIG. 1 illustrates a conventional coiled tubing tractor or
tool for conducting downhole operations such as intervention and
drilling. The illustrated system is an open loop configuration. The
coiled tubing system 100 typically includes a power supply 102 for
powering ground-level equipment, a tubing reel 104, a tubing guide
106, and a tubing injector 110, which are well known in the art.
The illustrated system includes a bottom hole drilling assembly 120
for drilling a borehole 132 with a drill bit 130. However, other
types of bottom hole assemblies 120 can alternatively be provided,
such as those for intervention operations like hole cleaning, sand
washing, acidizing, and the like. As known, coiled tubing 114 is
inserted into the borehole 132, and a fluid (e.g., drilling mud,
intervention fluid) is typically pumped through the inner flow
channel of the coiled tubing 114 towards the drill bit 130 located
at the end of the drill string. Positioned between the drill bit
130 and the coiled tubing 114 is a tool or tractor 112. The
illustrated bottom hole assembly 120 includes a number of elements
known to those skilled in the art, such as a downhole motor 122 and
a Measurement While Drilling (MWD) system 124. The tractor 112 is
preferably connected to the coiled tubing 114 and the bottom hole
assembly 120 by connectors 116 and 126, respectively, as known in
the art. In this system, the fluid is pumped through the inner flow
channel of the coiled tubing 114 and through the tractor 112 to the
drill bit 130. The fluid and drilling debris return to the surface
in the annulus defined between the exterior surface of the tractor
112 and the inner surface of the borehole 132, and also defined
between the exterior surface of coiled tubing 114 and the inner
surface of the borehole 132.
[0023] When operated, the tractor 112 is configured to move within
the borehole 132. This movement allows, for example, the tractor
112 to maintain a pre-selected force on the bottom hole assembly
120 such that the rate of movement or drilling can be controlled.
The tractor 112 can be used to move various types of equipment
through the borehole 132. For example, it will be understood that
the tractor 112 can be connected with or include, without
limitation, a downhole motor (for rotating a drill bit), steering
system, instrumentation sub (an instrumented package that controls
various aspects of downhole operation, including shock vibration,
weight on bit, torque at bit, rate of penetration, downhole motor
rpm, and differential pressure across motor), Measurement While
Drilling apparatus (an apparatus for measuring gyroscopic data such
as azimuth, inclination, and measured depth), drill bit, mechanical
and hydraulic disconnect for intervention, jetting tools,
production logging tools (including apparatus for measuring and
recording, without limitation, temperature, annulus pressure, and
various flow rates), drilling logging tools (for measuring and
recording, without limitation, resistivity measurements, magnetic
resonance (MRI), sonic neutron density, density, fluid
identification, and gamma ray measurements), perforation guns,
casing collar locators, and torque limiting tools (for
drilling).
[0024] A closed loop configuration has relevant differences from an
open loop system that operates on differential pressure (the
difference in pressure between the bore of the tractor and the
exterior of the tractor). With an open system, a restriction in the
system is required to produce a pressure difference (decrease)
between the interior and exterior of the tractor. Typically, the
restriction is an orifice such as a fixed diameter nozzle, and is
not capable of being adjusted from the surface. For typical coiled
tubing rig operations, the effective means of control is to control
the surface pump output flow rate. However, the differential
pressure available at the tractor is a quadratic (non-linear)
function of the surface pump output flow rate. Thus, doubling the
surface pump output flow rate will increase the differential
pressure through an in-series fixed orifice by a factor of four.
This makes power control of the tractor more difficult as normal
operational changes can have non-linear impact on tractor power,
requiring additional features to be incorporated into the open loop
powered tractor to restrict the amount of pressure delivered to the
gripper assemblies, for example. Further, this has a disadvantage
in that the normal operating range of the surface pump output flow
rate required for various operations may have to be restricted,
thus reducing cleaning efficiency during the operation.
[0025] Described below are four embodiments of closed loop power
systems for powering a tractor: (1) a turbine-powered motor, (2) an
E-line powered motor, (3) a turbine-powered pump; and (4) a pump
powered by a positive displacement motor. Any one of these
configurations can be used for circulating a given tractor's closed
system fluid (e.g., hydraulic fluid) through the tractor's valve
system, gripper assemblies, and propulsion assemblies. The
difference between these configurations is how power is delivered
to the downhole pump that circulates the fluid.
Turbine-Powered Motor
[0026] FIG. 2 is a schematic illustration of a turbine-powered
motor for circulating hydraulic fluid in a closed loop for powering
a downhole tool or tractor, according to an embodiment of the
present invention. In this configuration, a first fluid (typically
drilling/intervention fluid) that is externally pumped into the
coiled tubing usually at the ground surface flows through the
tractor and passes through a turbine 150 on its way to the
remaining bottom hole assembly (typically secured to the distal end
of the tractor). The turbine 150 drives a generator 152 that
produces electricity, as known in the art of turbine power
generation. The electricity produced by the generator 152 powers an
electric motor 154 that in turn powers a pump 156. The pump 156
circulates a second fluid (typically hydraulic fluid) in a closed
system loop 155. Box 158 represents a valve system, gripper
assemblies, and propulsion assemblies as known in the art. For
example, the valve system, gripper assemblies, and propulsion
assemblies can be substantially as shown and described in U.S. Pat.
Nos. 6,003,606; 6,347,674; 6,241,031; and 6,679,341, as well as
U.S. Patent Application Publication No. 2004/0168828. Also, the
gripper assemblies can be substantially as shown and described in
U.S. Pat. Nos. 6,464,003 and 6,715,559; U.S. Patent Application
Publication No. 2005/0247488; and U.S. Provisional App. No.
60/781,885. The second fluid provides hydraulic force for operation
of the gripper assemblies and propulsion assemblies, and in some
cases the valves.
[0027] Commercially available turbine-generators are sold by Spring
Electronics of Worcestershire, United Kingdom. One
turbine-generator sold by Spring Electronics comprises a
three-phase alternator, rectifier, and switch mode power supply
producing about 70 Watts at 50 volts. Larger versions of
turbine-generators are commercially available.
[0028] FIG. 3 is a more detailed schematic illustration of the
closed loop system of FIG. 2 adapted for use with a variation of
the Puller-Thruster Downhole Tool (also referred to as "Puller
Thruster Assembly" or "PTA") described in U.S. Pat. No. 6,003,606.
As the first fluid is pumped through the turbine 150, the turbine
powers the motor 154 and in turn the pump 156 that circulates the
second fluid through the illustrated valve assembly. The second
fluid flows from a supply line 228 through a start/stop valve 160
(also known as an "idler valve") into the valve system. A six-way
control valve 162 shuttles back and forth to direct the fluid to
and from an aft gripper assembly 180 (illustrated as a deflated
packerfoot) and a forward gripper assembly 182 (illustrated as an
inflated packerfoot), and also to and from an aft propulsion
assembly 184 and a forward propulsion assembly 186 (each propulsion
assembly comprising barrels and internal pistons, as taught in the
'606 patent). Valves 164 and 166 (also known as "directional
control valves") control the shuttling and position of the six-way
control valve 162. Packerfeet valves 168 and 170 regulate the flow
of fluid into the packerfeet 180 and 182. A reverser valve 172
controls the direction of tractor movement (i.e., uphole or
downhole). The operation of these valves is understood from the
teachings of the aforementioned patents incorporated by reference.
A sump 157 is preferably provided to store a reservoir of the
second fluid. The circulating second fluid returns to the sump 157
via a return line 230.
[0029] FIG. 3 shows an embodiment of a tool 200 (illustrated as a
Puller-Thruster Assembly) positioned within a drilled hole 205
inside a rock formation 212. The tool 200 includes an elongated
body formed of central coaxial cylinders 207. The aft gripper
assembly 180, aft propulsion assembly 184, forward gripper assembly
182, and forward propulsion assembly 186 are engaged on the central
coaxial cylinders 207. The aft propulsion assembly 184 includes
annular pistons 218 secured to the cylinders 207. Similarly, the
forward propulsion assembly 186 includes annular pistons 220
secured to the cylinders 207. The number of pistons can vary (e.g.,
up to 20 pistons) and depends on the desired thrust and pull
loads.
[0030] The tool body defines an internal mud flow passage 224
inside the cylinders 207. The aft end of the tool body has an inlet
201 connected to coiled tubing 114 via a coiled tubing connector
206 (connection can be threaded or snapped together). While FIG. 3
shows coiled tubing 114, the tool 200 can also be used with rotary
drill rigs instead (and the same is also true for the embodiments
of FIGS. 4-9). The forward end of the tool body is connected to a
bottom hole assembly (BHA) 204. The illustrated tool includes a
female coiled tubing connector 208 and stabilizers 210. The valve
control pack 214 is positioned between the forward and aft gripper
assemblies and also between the forward and aft propulsion
assemblies. Splines 216 can optionally be incorporated between the
central coaxial cylinders 207 and the gripper assemblies to prevent
the transmission of torque from the BHA 204 to the coiled tubing
114.
[0031] In use, drilling/intervention fluid flows from the coiled
tubing 114 into the inlet 201 of the tool body, and downhole
(toward the bottom of the hole) through the mud flow passage 224.
The fluid flows through the turbine 150, turning the motor 154. The
fluid continues through the passage 224 into the BHA 204, exiting
the BHA 204 through an outlet 203. The inlet 201 and outlet 203 are
also shown in relation to the turbine 150 on the bottom right hand
side of FIG. 3. The drilling/intervention fluid that exits via the
outlet 203 then flows uphole to the ground surface through an
annulus defined between the tool 200 and the drilled hole 205.
[0032] The upper right hand side of FIG. 3 includes a
cross-sectional view of the inflated packerfoot 182, taken along
line A-A. The illustrated packerfoot 182 includes three inflated
sections. Three mud flow return paths 222 are defined between the
three inflated sections of the packerfoot. These return paths 222
allow drilling fluid that exits via the outlet 203 to flow back
uphole past the inflated packerfoot. It will be understood that the
aft packerfoot 180 can be substantially identical to the forward
packerfoot 182. The illustrated packerfoot cross section shows the
packerfoot inflated radially beyond the outside diameter 226 of the
tool 200.
[0033] An advantage of the system using a turbine-powered motor as
illustrated is that the system is flow-based, meaning that the
downhole tractor can be more easily controlled by the surface pump
that pumps fluid down into the coiled tubing toward the turbine.
With a flow-based system, any change in the surface pump output
volume flow rate linearly changes the power available to the
tractor. Since the surface pump output flow rate can be relatively
easily adjusted dynamically during tractor operation, the resulting
adjustment of the power to the tractor provides enhanced control
over the tractor's speed and pulling force. This enhanced control
is available over a substantial operating range of surface pump
output flow rates. This is convenient for some types of operations.
For example, during sand washing it is desirable to provide a
maximum amount of fluid into the borehole while the tractor
continues its forward movement, usually at near-maximum pulling
capacity.
[0034] While the illustrated turbine-powered motor system disclosed
in FIGS. 2 and 3 offers enhanced control over prior systems, one
limitation of the system is a loss of efficiency. With each energy
conversion, the overall machine efficiency is reduced. For example,
the conversion from fluid flow of the drilling/intervention fluid
in the coiled tubing into mechanical rotation of the turbine
results in some energy loss. Similarly, the conversion of
mechanical rotation of the turbine into electrical power from the
generator also results in some energy loss.
[0035] Another limitation of the turbine-powered pump system is
that the turbine requires relatively high flow rates to generate
significant amounts of electrical power. For some tractor
operations, such as delivering perforation guns, it may be
desirable to limit the amount of flow that gets delivered to the
bottom hole assembly, for environmental protection reasons. For
these types of applications, a turbine-powered motor system may be
less preferable than other embodiments disclosed herein.
E-Line Powered Motor
[0036] FIG. 4 is a schematic illustration of an E-line powered
motor for circulating hydraulic fluid in a closed loop for powering
a downhole tool or tractor, according to an embodiment of the
present invention. In this configuration, an E-line 190 preferably
extends from the tractor upward to a control box 191, typically
located at the ground surface. As used herein, "control box" is a
broad term and incorporates a wide variety of controls, including
controls in a very small housing and those including wireless
features. The illustrated E-line 190 extends to the downhole
electric motor 154 that in turn powers the pump 156, it being
understood that the motor 154 and pump 156 are preferably housed
within or on the tractor. Compared to the embodiment of FIGS. 2 and
3, this embodiment does not include a turbine. The control box 151
preferably includes at least a portion of an electronic control
system adapted to send electrical control signals through the
E-line 190 for powering and controlling the motor 154. The pump 156
circulates a fluid (typically hydraulic fluid) in a closed system
loop 155. Box 158 represents a valve system, gripper assemblies,
and propulsion assemblies as known in the art and preferably as
described above.
[0037] In one embodiment, the E-line 190 is provided within coiled
tubing that also delivers a fluid to the tractor in an open system
loop. For example, in drilling operations it is typically desirable
to deliver fluid to the drill bit to lubricate the bit and carry
drill cuttings back up to the ground surface through the annulus
between the borehole inner surface and the exterior of the tractor.
In other operations, it may be desirable to deliver an intervention
fluid to the bottom hole assembly (e.g., sand washing, acidizing,
hole cleaning, etc.). The drilling or intervention fluid preferably
passes through an internal passage of the tractor to the bottom
hole assembly, and then flows up through the annulus.
[0038] In an alternative embodiment, the E-line 190 is provided
within a wireline that does not include a lumen for the delivery of
fluid. In other words, there is no coiled tubing. In this
embodiment, the tractor is completely electrically powered and
controlled. This configuration is useful for operations that do not
require the delivery of fluid into the borehole, for example
logging operations.
[0039] FIG. 5 is a more detailed schematic illustration of the
closed loop system of FIG. 4 adapted for use with the variation of
the Puller-Thruster Downhole Tool shown in FIG. 3. The E-line 190
provides power and electrical control for the motor 154, which in
turn powers the pump 156 that circulates a fluid (typically
hydraulic fluid) in a closed loop through the illustrated valve
assembly. The E-line 190 extends along with the coiled tubing 114
for delivering drilling/intervention fluid to a BHA 204. As noted
below, other embodiments omit the coiled tubing 114 and only
provide a wireline. In use, drilling/intervention fluid flows from
the coiled tubing 114 into the inlet 201 of the tool body, and
downhole (toward the bottom of the hole) through the mud flow
passage 224. The fluid flows into the BHA 204 and ultimately exits
the BHA 204 through the outlet 203. The drilling/intervention fluid
that exits via the outlet 203 then flows uphole to the ground
surface through an annulus defined between the tool 200 and the
drilled hole 205.
[0040] An advantage of an E-line powered motor as described herein
is that the tractor's performance is independent of any fluid flow
pumped down to the tractor from a ground surface pump. In the
illustrated embodiment, the power to operate the tractor comes from
surface electricity. Hence, the tractor is completely controllable
with electrical power transmission and control equipment. The power
can be delivered to the motor via an E-line or wireline, without
using any coiled tubing. Advantageously, for operations that do not
require an intervention or drilling fluid (e.g., logging), the
tractor can be operated with wireline equipment alone. This makes
the system easily transportable because the costs and time
associated with assembly and disassembly of coiled tubing equipment
are completely circumvented. Thus an advantage of the disclosed
embodiment is the ability to be rapidly deployed.
[0041] The disclosed system is useful for a variety of operations.
For example, the disclosed configuration is useful if multiple
tractors are employed in series, as may be necessary to traverse a
"washout" in the borehole. A washout is a portion of the borehole
having a relatively larger diameter than the rest of the borehole.
The washout diameter may be larger than the expansion capability of
the tractor's gripper assemblies, making it impossible to grip the
borehole wall within the washout. However, the washout can be
traversed if two tractors are employed in series and both tractors
employ a closed loop hydraulic fluid circuit powered by an E-line
and electric motor as disclosed above. In particular, the first
tractor's motor can be electrically powered until the first tractor
encounters the washout, at which point its gripper assemblies are
unable to contact the borehole wall. When this condition is
detected, power to the first tractor's motor can be turned off and
power to the second tractor's motor can be turned on. The second
tractor will then move until it encounters the washout, at which
point the second tractor can be turned off and the first tractor
again turned on to resume movement in a portion of the borehole
having a contactable hole diameter. It will be understood that the
separation between the tractors typically controls the maximum
length washout that can be traversed. Separate E-lines can be
provided for each tractor. Alternatively, a single E-line and a
downhole control system can be provided to control which tractor
receives the electrical power. In some operations, it may be
desirable to simultaneously power both tractors.
[0042] Even in embodiments in which the E-line is provided within
coiled tubing, skilled artisans will recognize that the fluid
delivery through the coiled tubing can be selectively provided or
shut off (simply by turning on or off the surface pumps) depending
upon the type of operation conducted by the tractor. For operations
that require tractor movement but do not require fluid for other
purposes (e.g., logging), tractor control becomes easier and less
expensive due to the ability to shut off the fluid delivery through
the coiled tubing.
[0043] Another advantage of the E-line powered motor system,
compared to the turbine-powered motor system of FIGS. 2 and 3, is
that there is no efficiency loss associated with converting turbine
rotation into electricity with a generator, or in converting a
fluid flow into motor rotation. The motor is controlled entirely
electrically. Still another advantage of the E-line powered motor
system, compared to the turbine-powered motor system, is that it is
possible to generate significant amounts of electrical power
without any fluid input to the tractor, let alone an undesirably
high rate of fluid input. As mentioned above, in certain tractor
operations, such as delivering perforation guns, it is desirable to
limit fluid flow to the bottom hole assembly. In these
applications, an E-line powered motor system may be preferable.
[0044] While the illustrated E-line powered motor system may be
more efficient in some cases than the turbine-powered motor system
described above, the E-line system nonetheless still involves some
energy losses associated with the transmission of electrical power
through the E-line, as well as efficiency loses in the electric
motor and the downhole pump.
[0045] In one embodiment, the control box 191 comprises a power
supply, switches, connectors, displays (e.g., LED, other types of
lights), a NEMA (National Electrical Manufacturers Association)
box, and electrical wires. In this embodiment, the control box 191
is designed for simple on/off toggling for the delivery of power to
the motor 154. In addition, various types of power regulation
devices may be included, such as a rheostat to adjust power to the
tractor and hence tractor speed.
[0046] In another embodiment, in addition to using the E-line 190
to deliver power and control signals to the motor 154, the control
box 191 delivers power and control signals through the E-line 190
to other components of the tractor. The control box 191 can also
receive signals from such other components and use the received
signals to make control decisions. In this embodiment, the control
box 191 preferably comprises a power supply, electrical switches,
electrical connectors, power converters, a computer server or
personal computer with CPU board, display panel, data storage
capability, user interface (preferably graphical), software
operating system, high speed mouse, and keyboard. Software for
running the control box 191 can be custom-developed. Alternatively,
the software can be a modification of a commercially available
program (such as "Lab View" made by National Instruments of Austin,
Tex.).
[0047] In this embodiment, the control box 191 can deliver
electrical power and control signals through the E-line 190 to
various instruments, tools, and apparatuses on the tractor. The
control box 191 can also be configured to present and store data
collected from such instruments, tools, and apparatuses. For
example, for intervention and completion operations, the tractor
can include logging tools (e.g., pressure sensors, flow rate
sensors, and temperature sensors), casing collar collectors, and/or
gyroscopic-based positioning instruments electrically connected to
the control box 191 through the E-line 190. As another example, for
drilling operations, the tractor can include a Measurement While
Drilling apparatus (e.g., for measuring inclination, azimuth, and
depth), tension compression sub, instrumented downhole drilling
motor, and/or Logging While Drilling apparatus (e.g., drilling
logging tools for detecting resistivity, magnetic resonance (MRI),
sonic, neutron density, density, fluid identification, gamma ray
measurements) electrically connected to the control box 191 through
the E-line 190. Furthermore, sensors such as speedometers,
temperature sensors, pressure sensors and the like can be included
within the tractor and in electrical communication with the control
box 191 through the E-line 190.
Turbine-Powered Pump
[0048] FIG. 6 is a schematic illustration of a turbine-powered pump
for circulating hydraulic fluid in a closed loop for powering a
downhole tool or tractor, according to an embodiment of the present
invention. In this configuration, a first fluid (typically
drilling/intervention fluid) that is externally pumped into the
coiled tubing at the ground surface flows through the tractor and
passes through a turbine 150 on its way to the remaining bottom
hole assembly (typically secured to the distal end of the tractor).
The flow through the turbine 150 produces rotation of the turbine's
output shaft, which drives the pump 156 through a gearbox 192. The
pump 156 circulates a second fluid (typically hydraulic fluid) in a
closed system loop 155. Box 158 represents a valve system, gripper
assemblies, and propulsion assemblies as known in the art and
preferably as described above.
[0049] FIG. 7 is a more detailed schematic illustration of the
closed loop system of FIG. 6 adapted for use with the variation of
the Puller-Thruster Downhole Tool shown in FIG. 3. As the first
fluid is pumped through the turbine 150, the turbine output shaft
rotates to power the pump 156 via the gearbox 192 (not shown), and
the pump 156 in turn circulates the second fluid through the
illustrated valve assembly. In use, drilling/intervention fluid
flows from the coiled tubing 114 into the inlet 201 of the tool
body, and downhole (toward the bottom of the hole) through the mud
flow passage 224. The fluid flows through the turbine 150, powering
the pump 156. The fluid continues through the passage 224 into the
BHA 204, exiting the BHA 204 through the outlet 203. The inlet 201
and outlet 203 are also shown in relation to the turbine 150 on the
bottom right hand side of FIG. 7. The drilling/intervention fluid
that exits via the outlet 203 then flows uphole to the ground
surface through an annulus defined between the tool 200 and the
drilled hole 205.
[0050] A relevant advantage of using a turbine-powered pump as
illustrated is that the system is flow-based, as described above.
In other words, the downhole tractor can be more easily controlled
by the surface pump that pumps fluid down into the coiled tubing
toward the turbine. With a flow-based system, any change in the
surface pump output volume flow rate linearly changes the power
available to the tractor. Since the surface pump output flow rate
can be relatively easily adjusted dynamically during tractor
operation, the resulting adjustment of the power to the tractor
provides enhanced control over the tractor's speed and pulling
force. This enhanced control is available over a substantial
operating range of surface pump output flow rates.
[0051] Another relevant advantage of the turbine-powered pump
system is that the downhole pump is desirably directly powered by
the rotating output of the turbine/gearbox combination, without any
intermediate steps (e.g., electrical power generation from the
turbine output, and use of such electrical power to drive an
electric motor that drives the pump). As explained above, the
provision of such intermediate steps can introduce a risk of a loss
of efficiency in converting the kinetic energy of the first fluid
pumped into the turbine into power for driving the operation of the
downhole pump. While the turbine-powered pump system still involves
some efficiency losses associated with converting the first fluid's
flow into mechanical rotation of the turbine, the disclosed
turbine/gearbox combination advantageously provides a highly
efficient conversion of the first fluid's kinetic energy.
Pump Powered by Positive Displacement Motor
[0052] FIG. 8 is a schematic illustration of a pump powered by a
positive displacement motor (PDM) for circulating hydraulic fluid
in a closed loop for powering a downhole tool or tractor, according
to one embodiment of the present invention. In this configuration,
a first fluid (typically drilling/intervention fluid) that is
externally pumped into the coiled tubing typically at the ground
surface flows through the tractor and passes through a positive
displacement motor 250 (sometimes referred to as a "mud motor") on
its way to the remaining bottom hole assembly (typically secured to
the distal end of the tractor). The flow through the positive
displacement motor 250 produces rotation of the motor's output
shaft 251, which drives the pump 156, typically through a gearbox
252. The pump 156 circulates a second fluid (typically a different
type of fluid than the first fluid, such as, for example, hydraulic
fluid) in a closed system loop 155. Box 158 represents a valve
system, gripper assemblies, and propulsion assemblies as known in
the art and preferably as described above.
[0053] Positive displacement motors are well known. A positive
displacement motor typically comprises a stator that defines a
fluid flow enclosure, a rotor that revolves within the stator, and
an output shaft that rotates with the rotor. The rotor typically
includes a plurality of lobes, i.e., curved or rounded projections
that absorb the kinetic energy of fluid flowing through the stator,
causing the rotor to revolve within the stator. Numerous suppliers
sell positive displacement motors in a wide variety of sizes and
performance capabilities. For example, Weatherford's
(www.weatherford.com) "High Performance PDM" and a "MacDrill High
Temperature PDM" are suitable, as is the "Navi-Drill Ultra Series"
motors sold by Baker Hughes (www.bakerhughes.com). Positive
displacement motors are also sold by numerous smaller suppliers,
and are commercially available in small diameter sizes that produce
significant torque at acceptable RPM levels.
[0054] FIG. 9 is a more detailed schematic illustration of the
closed loop system of FIG. 8 adapted for use with the variation of
the Puller-Thruster Downhole Tool shown in FIG. 3. As the first
fluid is pumped through the positive displacement motor 250, the
motor's output shaft 251 rotates to power the pump 156 via the
gearbox 252, and the pump 156 in turn circulates the second fluid
through the illustrated valve assembly. In use,
drilling/intervention fluid flows from the coiled tubing 114 into
the inlet 201 of the tool body, and downhole (toward the bottom of
the hole) through the mud flow passage 224. The fluid flows through
the positive displacement motor 250, which drives the pump 156
through the gearbox 252. The fluid continues through the passage
224 into the BHA 204, exiting the BHA 204 through the outlet 203.
The inlet 201 and outlet 203 are also shown in relation to the
positive displacement motor 250 on the bottom right hand side of
FIG. 9. The drilling/intervention fluid that exits via the outlet
203 then flows uphole to the ground surface through an annulus
defined between the tool 200 and the drilled hole 205.
[0055] A relevant advantage of using a pump 156 powered by a
positive displacement motor 250 as illustrated is that the system
is flow-based, as described above. In other words, the downhole
tractor can be more easily controlled by the surface pump that
pumps fluid down into the coiled tubing 114 toward the motor 250.
With a flow-based system, any change in the surface pump output
volume flow rate linearly changes the power available to the
tractor. Since the surface pump output flow rate can be relatively
easily adjusted dynamically during tractor operation, the resulting
adjustment of the power to the tractor provides enhanced control
over the tractor's speed and pulling force. This enhanced control
is available over a substantial operating range of surface pump
output flow rates. The pump 156 powered by a positive displacement
motor 250 also allows an operator to more quickly and easily shut
off the tractor simply by stopping the pumping of the open system
fluid down through the coiled tubing 114 to the motor 250, or by
reducing the fluid's flow rate to a level that is less than a level
required to maintain operation of the pump 156.
[0056] Another advantage of a positive displacement motor 250 is
that several design aspects of the motor can be varied to allow
some tuning of the expected operational torque and RPM delivered to
the gearbox 252. Design aspects that can be varied include the
rotor pitch angle, the number of stages, and the number of lobes of
the rotor. This makes it easier to optimize the range of operation
of the pump 156. Still another advantage is that positive
displacement motors are a proven, reliable, and relatively
inexpensive technology for utilizing the kinetic energy of a
fluid.
[0057] Yet another advantage of this system is that the pump 156
can be directly powered by the rotating output shaft 251 of the
motor/gearbox combination, without any intermediate steps (e.g.,
electrical power generation from the motor output, and use of such
electrical power to drive an electric motor that drives the pump).
The provision of such intermediate steps would introduce a risk of
a loss of efficiency in converting the kinetic energy of the first
fluid pumped through the positive displacement motor 250 into power
for driving the operation of the pump 156. The disclosed
motor/gearbox combination advantageously provides a highly
efficient conversion of the first fluid's kinetic energy.
[0058] Although this invention has been disclosed in the context of
certain preferred embodiments and examples, it will be understood
by those skilled in the art that the present invention extends
beyond the specifically disclosed embodiments to other alternative
embodiments and/or uses of the invention and obvious modifications
thereof. Thus, it is intended that the scope of the present
invention herein disclosed should not be limited by the particular
disclosed embodiments described above.
* * * * *