U.S. patent application number 11/024285 was filed with the patent office on 2005-06-30 for turbine generator system and method.
This patent application is currently assigned to NOBLE DRILLING CORPORATION. Invention is credited to Maurer, William C., McDonald, William J..
Application Number | 20050139393 11/024285 |
Document ID | / |
Family ID | 34748834 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139393 |
Kind Code |
A1 |
Maurer, William C. ; et
al. |
June 30, 2005 |
Turbine generator system and method
Abstract
In one embodiment, a wellbore power generation method includes
causing a fluid to flow through a downhole turbine, and causing the
turbine to rotate a generator. At least one of a turbine
configuration and a flow rate of the fluid is selected to cause the
downhole turbine to operate near its runaway speed, such that
changes in load applied to the generator do not substantially
affect a rotation rate of the downhole turbine.
Inventors: |
Maurer, William C.;
(Houston, TX) ; McDonald, William J.; (Houston,
TX) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
2001 ROSS AVENUE
SUITE 600
DALLAS
TX
75201-2980
US
|
Assignee: |
NOBLE DRILLING CORPORATION
|
Family ID: |
34748834 |
Appl. No.: |
11/024285 |
Filed: |
December 28, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60532931 |
Dec 29, 2003 |
|
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|
Current U.S.
Class: |
175/57 ;
166/65.1; 175/40; 175/73 |
Current CPC
Class: |
E21B 41/0085
20130101 |
Class at
Publication: |
175/057 ;
175/040; 175/073; 166/065.1 |
International
Class: |
E21B 007/00 |
Claims
1. A wellbore power generation method, comprising: causing a fluid
to flow through a downhole turbine; causing the turbine to rotate a
generator; and wherein at least one of a turbine configuration and
a flow rate of the fluid is selected to cause the downhole turbine
to operate near its runaway speed, such that changes in load
applied to the generator do not substantially affect a rotation
rate of the downhole turbine.
2. The method of claim 1, wherein causing the downhole turbine to
operate near its runaway speed comprises causing the downhole
turbine to operate at a minimum of 75% of its runaway speed.
3. The method of claim 1, wherein causing the downhole turbine to
operate near its runaway speed comprises causing the downhole
turbine to operate at a minimum of 85% of its runaway speed.
4. The method of claim 1, wherein causing the downhole turbine to
operate near its runaway speed comprises causing the downhole
turbine to operate substantially at its runaway speed.
5. The method of claim 1, wherein the downhole turbine generator is
associated with a drilling tool and the fluid is a drilling
fluid.
6. The method of claim 5, wherein the drilling tool is selected
from the group consisting of a MWD tool, a LWD tool, and a rotary
steerable tool.
7. The method of claim 1, wherein the generator comprises an
electric generator.
8. The method of claim 1, wherein the generator comprises a
hydraulic pump.
9. The method of claim 1, wherein the downhole turbine generator is
associated with a producing well and the fluid is a production
fluid.
10. A wellbore power generation system, comprising: a pump
circulating a fluid through a downhole turbine to rotate a
generator; and wherein at least one of a turbine configuration and
a flow rate of the fluid is selected to cause the downhole turbine
to operate near its runaway speed, such that changes in load
applied to the generator do not substantially affect a rotation
rate of the downhole turbine.
11. The system of claim 10, wherein the fluid operates the downhole
turbine at a minimum of 75% of its runaway speed.
12. The system of claim 10, wherein the fluid operates the downhole
turbine at a minimum of 85% of its runaway speed.
13. The system of claim 10, wherein the fluid operates the downhole
turbine substantially at its runaway speed.
14. The system of claim 10, further comprising a drilling tool
associated with the downhole turbine generator and wherein the
fluid is a drilling fluid.
15. The system of claim 14, wherein the drilling tool is selected
from the group consisting of a MWD tool, a LWD tool, and a rotary
steerable tool.
16. The method of claim 10, wherein the generator comprises an
electric generator.
17. The method of claim 10, wherein the generator comprises a
hydraulic pump.
18. The system of claim 10, further comprising a producing well
associated with the downhole turbine generator and wherein the
fluid is a production fluid.
19. A wellbore drilling method, comprising: drilling a wellbore
with a drilling tool, the drilling tool comprising a downhole
turbine driven by a drilling fluid flowing at a first flow rate;
causing the downhole turbine to operate near its runaway speed; and
then changing the flow rate of the drilling fluid to a second flow
rate without removing the drilling tool from the wellbore, the
second flow rate being different from the first flow rate by at
least twenty-five percent.
20. The method of claim 19, wherein causing the downhole turbine to
operate near its runaway speed comprises causing the downhole
turbine to operate at a minimum of 75% of its runaway speed.
21. The method of claim 19, wherein causing the downhole turbine to
operate near its runaway speed comprises causing the downhole
turbine to operate substantially at its runaway speed.
22. A power generation method, comprising: causing a fluid to flow
through a turbine disposed in a conduit; and causing the turbine to
rotate a generator; and wherein at least one of a turbine
configuration and a flow rate of the fluid is selected to cause the
turbine to operate near its runaway speed, such that changes in
load applied to the generator do not substantially affect a
rotation rate of the turbine.
23. The method of claim 22, wherein causing the turbine to operate
near its runaway speed comprises causing the turbine to operate at
a minimum of 75% of its runaway speed.
24. The method of claim 22, wherein causing the turbine to operate
near its runaway speed comprises causing the turbine to operate
substantially at its runaway speed.
Description
RELATED APPLICATIONS
[0001] Priority is claimed from U.S. Provisional Application Ser.
No. 60/532,931, entitled "Downhole Turbine Generator Apparatus,"
filed provisionally on Dec. 29, 2003.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates generally to the field of power
generation and, more particularly, to a downhole turbine generator
system and method.
BACKGROUND OF THE INVENTION
[0003] Downhole wellbore drilling tools include instrumentation,
such as "measurement while drilling" (MWD) instruments, which use
flow of drilling mud to operate an electrical generator and/or
hydraulic pump. The electrical generator and/or hydraulic pump
provides power to operate various devices within such instruments,
for example, to power electronic circuitry and/or to operate
various steering devices that are hydraulically actuated.
[0004] It is known in the art to use a turbine to convert drilling
mud flow into rotational energy to drive the electrical generator
and/or hydraulic pump. A turbine includes a plurality of
circumferentially spaced apart "blades" having physical
characteristics selected to provide a particular rotational speed
and torque (the product of which is the power) output to drive a
electrical generator and/or hydraulic pump for a selected flow rate
of drilling mud therethrough.
[0005] For most turbines, turbine blades deliver maximum power
output when operated at about half of their "runaway" speed
(rotational speed of the turbine with substantially zero load). A
graph of the power output with respect to turbine rotation rate of
a typical fluid driven turbine has a characteristic trajectory. The
trajectory begins at zero power output at zero speed, rises to a
power peak at a determinable rotation speed, and again returns to
zero power output at the runaway speed. Near the peak power output,
even small changes in the load applied to the turbine can result in
large changes in the rotational speed of the turbine at a constant
mud flow rate. When driving a device such as an electric generator,
for example, such small changes in load may occur in response to
meeting the demands of downhole electrically powered equipment,
such as the switching of electronics or the firing of
solenoid-operated valves, and thus can cause significant changes in
the turbine rotary speed. Such changes in the rotary speed may
result in the turbine not delivering adequate power to the downhole
equipment under increased load conditions.
[0006] The rotary speed of a turbine varies approximately linearly
with the mud flow rate through the turbine. As a result,
turbine-driven power generating systems used in downhole equipment
must use a wide variety of blade characteristics (e.g., blade
angle, blade flow area, blade pitch and curvature, etc.) to allow
use of the turbine generator system in a number of different
expected drilling mud flow rates. Generally, the blade
characteristics in the turbine must be selected to match the
expected mud flow rates. When drillers change the mud flow rate by
more than about 25%, it is usually necessary to change the turbine
blade configuration to match, otherwise the turbine may not deliver
adequate power to the electrical and/or hydraulic generator.
[0007] Changing the blade configuration can include, for example,
adding additional "stages" (combination of turbine and stator
sections) or changing the physical characteristics of the turbine
in one or more such sections. Changing the blade configuration can
be a time-consuming and expensive operation since the downhole tool
must be pulled from the well to change any aspect of the turbine
system. Further, manufacturing and maintaining additional turbine
sets to enable use with varying expected mud flow rates can add to
the overall capital cost of such systems.
SUMMARY OF THE INVENTION
[0008] In one embodiment, a wellbore power generation method
includes causing a fluid to flow through a downhole turbine, and
causing the turbine to rotate a generator. At least one of a
turbine configuration and a flow rate of the fluid is selected to
cause the downhole turbine to operate near its runaway speed, such
that changes in load applied to the generator do not substantially
affect a rotation rate of the downhole turbine.
[0009] Embodiments of the invention may provide a number of
technical advantages. In one embodiment, operating a downhole
turbine at or near its runaway speed causes an electric generator
for a downhole drilling tool to be very stable and operate at
relatively constant speed, which makes the electric generator
easier to use. Such an operating method facilitates fewer turbine
blade designs, which reduces the need to inventory a large number
of turbine blade designs and eliminates the need to disassemble the
tool and change the blade designs for different well
applications.
[0010] Other technical advantages are readily apparent to one
skilled in the art from the following figures, descriptions, and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional elevation view illustrating a
turbine generator used in drilling a wellbore in accordance with
one embodiment of the present invention;
[0012] FIG. 2 is a graph illustrating the operating range of prior
art turbines; and
[0013] FIG. 3 is a graph illustrating an operating range of a
turbine in accordance with one embodiment of the present
invention.
DETAILED DESCRIPTION
[0014] FIG. 1 is cross-sectional elevation view illustrating a
turbine generator 100 used in drilling a wellbore 102 in accordance
with one embodiment of the present invention. Although FIG. 1
illustrates turbine generator 100 being used in the drilling of
wellbore 102, the present invention contemplates other applications
for turbine generator 100, such as the production of wellbore
fluids and fluid flow in pipelines, such as oil and gas gathering
lines and major pipelines, or other suitable conduits.
[0015] In the illustrated embodiment in FIG. 1, turbine generator
100 is associated with a suitable drilling tool (not explicitly
illustrated) in order to drill wellbore 102. For example, the
drilling tool may be a measurement while drilling ("MWD") tool,
logging while drilling ("LWD") tool, rotary steerable directional
drilling tool, or other suitable tools. Turbine generator 100 may
be used to provide electrical and/or hydraulic power to any
suitable system, equipment, instrument, or device, such as simple
electronic sensors, data acquisition and control ("DAC") systems,
downhole hydraulic power generation systems, systems that switch
hydraulic valves downhole, resistivity and nuclear magnetic
residence ("NMR") logging tools, Electromagnetic ("EM")-type LWD
tools, or other suitable MWD tools. In a pipeline application,
turbine generator 100 could be used to "trickle charge" batteries
used for powering monitoring stations on pipelines or for powering
cathodic protection devices in extremely harsh environments. The
present invention contemplates turbine generator 100 delivering any
suitable amount of power to any suitable system, equipment,
instrument, or device.
[0016] The present invention also contemplates any suitable
configuration for turbine generator 100. In the illustrated
embodiment, turbine generator 100 includes a turbine 111 comprised
of a turbine shaft 104 and a rotor blade assembly 106, and a stator
blade assembly 105 that are each disposed within a housing 103.
Each of these components may have any suitable size and shape and
may be formed from any suitable material known in the art for use
in wellbore turbine power generation systems. Both stator blade
assembly 105 and rotor blade assembly 106 may have any suitable
blade design known in the art.
[0017] Turbine 111 is driven by a fluid 110 flowing through housing
103. Fluid 110 is circulated through housing 103 by a pump 108,
which may be any suitable device operable to circulate fluid
through housing 103. Fluid 110 may be any suitable fluid depending
on the application. For example, in the illustrated embodiment,
fluid 110 is a suitable drilling fluid, such as drilling mud. In
other applications, fluid 110 may be a production fluid or other
suitable fluid.
[0018] In downhole turbine power generation systems known in the
art, as explained in the BACKGROUND section herein, turbine blades
operate most efficiently and deliver maximum power output when
operated at approximately half of their runaway speed for any
selected flow rate. Consequently, turbine generating systems known
in the art typically have turbine blade characteristics selected to
provide peak power output at the expected flow rate of drilling mud
through the turbine. At the peak power output value (about half
runaway speed), however, small changes in power output of the
turbine correspond to relatively large changes in the rotation
speed of the turbine. Thus, small changes in power load on the
generating device driven by the turbine, such as to meet variable
demand of certain downhole equipment, for example, the switching of
electronics or the firing of solenoid valves, may cause significant
changes in the turbine rotary speed. This is illustrated in FIG. 2,
which shows a graph 200 of power output with respect to rotation
speed of typical turbine power generation systems.
[0019] As illustrated by graph 200, an operating range 202 (the
shaded area under the curve) illustrates the operating range of
prior art downhole turbines. As illustrated, operating range 202 is
at or very near 50% of the runaway speed for the downhole turbine.
Thus, small changes in the power output to meet the changes in
demand of the downhole equipment may cause a significant change in
the rotary speed of the downhole turbine, as shown by graph 200. As
a result, the downhole turbine system may not deliver adequate
power to the downhole equipment under some load conditions.
[0020] Therefore, in one embodiment of the invention, turbine 111
is caused to operate at or near its runaway speed by adjusting the
flow of fluid 110 through housing 103. This is illustrated in FIG.
3, which shows a graph 300 of power versus speed of turbine 111
according to one embodiment of the invention. Operating the turbine
at or near its runaway speed can be attained by selecting a turbine
blade configuration for which the peak power output (at one half
runaway speed) is much greater than the maximum expected load on
the turbine.
[0021] In the embodiment illustrated in FIG. 3, an operating range
302 shows that turbine 111 is operated at a minimum of about 75% of
its runaway speed. In other embodiments, downhole turbine 111
operates at a minimum of about 85% of its runaway speed. In a more
particular embodiment of the invention, turbine 111 operates
substantially at its runaway speed. Operating turbine 111 at or
near its runaway speed prevents changes in power output from
significantly varying the speed of turbine 111, which makes turbine
111 less vulnerable to short-duration "spike" loads that may occur
during a drilling operation, such as activating solenoid valves or
pulsing the stepper motor in a mud pulse LWD system. In addition,
in some embodiments, turbine 111 may deliver much more power than
is needed by the downhole equipment so turbine 111 may always
deliver adequate power regardless of the flow rate of fluid 110 or
the power requirement of the equipment.
[0022] Another important advantage of operating turbine 111 at or
near its runaway speed is that it eliminates the need to have
available a large number of different turbine blade configurations,
as in previous downhole turbine systems. Most operators of such
downhole turbine systems keep an inventory of somewhere between
five to ten different turbine blade designs for the situation when
the drilling fluid flow rate needs to be changed in respect of
certain drilling conditions. Changing the blade configuration can
be a time-consuming and expensive operation since the downhole tool
must be pulled from the wellbore to change any part of the
turbine.
[0023] In operation of one embodiment of the invention, a wellbore
drilling method may include drilling wellbore 102 with a drilling
tool having turbine 111 that is driven by drilling fluid 110
flowing at a first flow rate. Turbine 111 is caused to operate at
its runaway speed during the drilling process. If an operator needs
to overcome hole problems, such as inadequate rock cuttings removal
from the hole or hole enlargements that require higher flow rates
to lift the rock cuttings in the enlarged zones, the flow rate of
fluid 110 needs to be increased. Therefore the flow rate of
drilling fluid 110 may be changed to a second flow rate without
removing the drilling tool from wellbore 102. In one embodiment,
the second flow rate is different from the first flow rate by at
least twenty-five percent.
[0024] Although embodiments of the invention and their advantages
are described in detail, a person of ordinary skill in the art
could make various alterations, additions, and omissions without
departing from the spirit and scope of the present invention as
defined by the appended claims.
* * * * *