U.S. patent application number 13/797675 was filed with the patent office on 2014-03-27 for system and method for wireless drilling and non-rotating mining extenders in a drilling operation.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Brian Oliver Clark, Daniel Codazzi, Raphael Gadot.
Application Number | 20140083770 13/797675 |
Document ID | / |
Family ID | 50337786 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140083770 |
Kind Code |
A1 |
Codazzi; Daniel ; et
al. |
March 27, 2014 |
System And Method For Wireless Drilling And Non-Rotating Mining
Extenders In A Drilling Operation
Abstract
Various embodiments of methods and systems for wireless power
and data communications transmissions to a sensor subassembly below
a mud motor in a bottom hole assembly are disclosed. Power and/or
communications are transmitted through stationary or fixed coils.
By leveraging resonantly tuned circuits and impedance matching
techniques for the stationary coils, power and/or communications
can be transmitted efficiently from one stationary coil to the
other stationary coil despite any vibration and/or misalignment of
the two coils.
Inventors: |
Codazzi; Daniel; (Houston,
TX) ; Gadot; Raphael; (Houston, TX) ; Clark;
Brian Oliver; (Sugar Land, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
50337786 |
Appl. No.: |
13/797675 |
Filed: |
March 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61704820 |
Sep 24, 2012 |
|
|
|
61704805 |
Sep 24, 2012 |
|
|
|
61704758 |
Sep 24, 2012 |
|
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Current U.S.
Class: |
175/40 |
Current CPC
Class: |
E21B 17/028 20130101;
E21B 47/13 20200501; E21B 47/12 20130101 |
Class at
Publication: |
175/40 |
International
Class: |
E21B 47/12 20060101
E21B047/12 |
Claims
1. A drilling and mining ("D&M") extender device for
communicatively coupling two stationary tools in a bottom hole
assembly of a drill string, the extender device comprising: a first
stationary coil associated with a first tool; and a second
stationary coil associated with a second tool; wherein electrical
transmissions between the first and second tools are transmitted
wirelessly between the first and second stationary coils via
inductive coupling between the coils; the first stationary coil
positioned proximate to the second stationary coil; the coils are
inductively coupled such that: k=M/ {square root over
(L.sub.1L.sub.2)}.ltoreq.0.9, wherein k is the coupling coefficient
of the coils, M is the mutual inductance between the coils, and
L.sub.1 and L.sub.2 are the self-inductances of the respective
coils; each coil is resonantly tuned with a capacitor such that:
f.sub.1.apprxeq.f.sub.2, wherein f 1 = 1 2 .pi. L 1 C 1
##EQU00012## and ##EQU00012.2## f 2 = 1 2 .pi. L 2 C 2
##EQU00012.3## and f.sub.1 and f.sub.2 are the frequencies in Hertz
of the respective coils, L.sub.1 and L.sub.2 are the
self-inductances of the respective coils, and C.sub.1 and C.sub.2
are capacitances of tuning capacitors associated with the
respective coils; and the coils have an associated figure of merit,
U, such that: U=k {square root over (Q.sub.1Q.sub.2)}.gtoreq.3,
wherein Q 1 = 2 .pi. f 1 L 1 R 1 ##EQU00013## and ##EQU00013.2## Q
2 = 2 .pi. f 2 L 2 R 2 ##EQU00013.3## and Q1 and Q2 are the quality
factors associated with the respective coils, f.sub.1 and f.sub.2
are the frequencies in Hertz of the respective coils, L.sub.1 and
L.sub.2 are the self-inductances of the respective coils, and
R.sub.1 and R.sub.2 are the resistances of the respective
coils.
2. The drilling and mining extender device of claim 1, wherein the
first tool has an impedance as a source, R.sub.S wherein the
impedance is governed by the equation: R.sub.S.apprxeq.R.sub.1
{square root over (1+k.sup.2Q.sub.1Q.sub.2)}, wherein R.sub.1 is
the series resistance of the first coil, k is the coupling
coefficient of the pair of coils, Q.sub.1 is the quality factor
associated with the first coil and Q.sub.2 is the quality factor
associated with the second coil.
3. The drilling and mining extender device of claim 2, further
comprising approximately matching an impedance of the second tool
with an impedance of the source by setting: R.sub.L.apprxeq.R.sub.2
{square root over (1+k.sup.2Q.sub.1Q.sub.2)}, wherein R.sub.2 is
the series resistance of the second coil, k is the coupling
coefficient of the pair of coils, Q.sub.1 is the quality factor
associated with primary coil and Q.sub.2 is the quality factor
associated with the second coil.
4. The drilling and mining extender device of claim 1, wherein one
or more of the electrical transmissions are selected from the group
of power transmissions and data communication transmissions.
5. The drilling and mining extender device of claim 1, wherein the
first coil is of a mandrel type and the second coil is of a annular
type.
6. The drilling and mining extender device of claim 1, wherein the
first coil is of a mandrel type and the second coil is of a mandrel
type.
7. The drilling and mining extender device of claim 1, wherein the
first coil is of an annular type and the second coil is of an
annular type.
8. The drilling and mining extender device of claim 1, wherein the
first tool and second tool mate together using a fixed and
non-movable coupling.
9. The drilling and mining extender device of claim 8, wherein the
fixed and non-movable coupling comprises a mechanical fastener.
10. The drilling and mining extender device of claim 9, wherein the
fixed and non-movable coupling comprises at least one of screw
threads, rivets, and welds.
11. A drilling and mining ("D&M") extender device for
communicatively coupling two stationary tools in a bottom hole
assembly of a drill string, the extender device comprising: a first
stationary coil associated with a first tool; and a second
stationary coil associated with a second tool; wherein electrical
transmissions between the first and second tools are transmitted
wirelessly between the first and second stationary coils via
inductive coupling between the coils; the first stationary coil
positioned proximate to the second stationary coil, the first tool
and second tool mate together using a fixed and non-movable
coupling.
12. The drilling and mining extender device of claim 11, wherein
the fixed and non-movable coupling comprises at least one of screw
threads, rivets, and welds.
13. The drilling and mining extender device of claim 11, wherein
the coils are inductively coupled such that: k=M/ {square root over
(L.sub.1L.sub.2)}.ltoreq.0.9, wherein k is the coupling coefficient
of the coils, M is the mutual inductance between the coils, and
L.sub.1 and L.sub.2 are the self-inductances of the respective
coils; each coil is resonantly tuned with a capacitor such that:
f.sub.1.apprxeq.f.sub.2, wherein f 1 = 1 2 .pi. L 1 C 1
##EQU00014## and ##EQU00014.2## f 2 = 1 2 .pi. L 2 C 2
##EQU00014.3## and f.sub.1 and f.sub.2 are the frequencies in Hertz
of the respective coils, L.sub.1 and L.sub.2 are the
self-inductances of the respective coils, and C.sub.1 and C.sub.2
are capacitances of tuning capacitors associated with the
respective coils; and the coils have an associated figure of merit,
U, such that: U=k {square root over (Q.sub.1Q.sub.2)}.gtoreq.3,
wherein Q 1 = 2 .pi. f 1 L 1 R 1 ##EQU00015## and ##EQU00015.2## Q
2 = 2 .pi. f 2 L 2 R 2 ##EQU00015.3## and Q1 and Q2 are the quality
factors associated with the respective coils, f.sub.1 and f.sub.2
are the frequencies in Hertz of the respective coils, L.sub.1 and
L.sub.2 are the self-inductances of the respective coils, and
R.sub.1 and R.sub.2 are the resistances of the respective
coils.
14. The drilling and mining extender device of claim 11, wherein
one or more of the electrical transmissions are selected from the
group of power transmissions and data communication
transmissions.
15. The drilling and mining extender device of claim 11, wherein
the first coil is of a mandrel type and the second coil is of a
annular type.
16. The drilling and mining extender device of claim 11, wherein
the first coil is of a mandrel type and the second coil is of a
mandrel type.
17. The drilling and mining extender device of claim 11, wherein
the first coil is of an annular type and the second coil is of an
annular type.
18. A wireless coupling for drilling comprising: a first stationary
coil attached to a first drilling structure; and a second
stationary coil attached to a second drilling structure; wherein
electrical transmissions between the first and second coils are
transmitted wirelessly via inductive coupling between the coils;
the first stationary coil positioned proximate to the second
stationary coil, the first drilling structure and second drilling
structure being held in position with a fixed and non-movable
fastening mechanism.
19. The wireless coupling of claim 18, wherein the fixed and
non-movable fastening mechanism comprises at least one of screw
threads, rivets, and welds.
20. The wireless coupling of claim 19, wherein the coils are
inductively coupled such that: k=M/ {square root over
(L.sub.1L.sub.2)}.ltoreq.0.9, wherein k is the coupling coefficient
of the coils, M is the mutual inductance between the coils, and
L.sub.1 and L.sub.2 are the self-inductances of the respective
coils; each coil is resonantly tuned with a capacitor such that:
f.sub.1.apprxeq.f.sub.2, wherein f 1 = 1 2 .pi. L 1 C 1
##EQU00016## and ##EQU00016.2## f 2 = 1 2 .pi. L 2 C 2
##EQU00016.3## and f.sub.1 and f.sub.2 are the frequencies in Hertz
of the respective coils, L.sub.1 and L.sub.2 are the
self-inductances of the respective coils, and C.sub.1 and C.sub.2
are capacitances of tuning capacitors associated with the
respective coils; and the coils have an associated figure of merit,
U, such that: U=k {square root over (Q.sub.1Q.sub.2)}.gtoreq.3,
wherein Q 1 = 2 .pi. f 1 L 1 R 1 ##EQU00017## and ##EQU00017.2## Q
2 = 2 .pi. f 2 L 2 R 2 ##EQU00017.3## and Q1 and Q2 are the quality
factors associated with the respective coils, f.sub.1 and f.sub.2
are the frequencies in Hertz of the respective coils, L.sub.1 and
L.sub.2 are the self-inductances of the respective coils, and
R.sub.1 and R.sub.2 are the resistances of the respective coils.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Patent Application Ser. No. 61/704,820, entitled
"System And Method For Wireless Drilling And Mining Extenders In A
Drilling Operation, and filed on Sep. 24, 2012, U.S. Provisional
Patent Application Ser. No. 61/704,805, entitled "System And Method
for Wireless Power And Data Transmission In A Mud Motor," and filed
on Sep. 24, 2012, and U.S. Provisional Patent Application Ser. No.
61/704,758, entitled "Positive Displacement Motor Rotary Steerable
System And Apparatus," and filed on Sep. 24, 2012, the disclosures
of which are hereby incorporated by reference in their
entireties.
DESCRIPTION OF THE RELATED ART
[0002] Bottom hole assemblies ("BHA") at the end of a typical drill
string used in the drilling and mining industry today may be a
complex assembly of technology that includes not only a drill bit,
but also an array of serially connected drill string components or
tools. The various drill string tools that make up a BHA commonly
include electrically powered systems on a chip ("SoC") designed to
leverage local sensors for the collection, processing and
transmission of data that can be used to optimize a drilling
strategy. In many cases, the various tools that make up a BHA are
in bidirectional communication.
[0003] As one might expect, a BHA may be an equipment assembly with
a hardened design that can withstand the demands of a drill string.
Failure of a BHA, whether mechanically or electrically, inevitably
brings about expensive and unwelcomed operating costs as the
drilling process may be halted and the drill string retracted from
the bore so that the failed BHA can be repaired. In many cases,
retraction of a drill string to repair a failed BHA can range in
cost from hundreds of thousands of dollars to millions of
dollars.
[0004] A common failure point for BHAs is the point of connection
from tool to tool, which is naturally prone to failure from adverse
fluid ingress and/or misalignment between adjacent tools. While the
individual tools may be robust in design, the mechanical and
electrical connections between the tools may be a natural "weak
point" that often determines the overall reliability of the BHA
system.
SUMMARY OF THE DISCLOSURE
[0005] Various embodiments of methods and systems for wireless
power and data communications transmissions in a BHA are disclosed.
The efficient transfer of electrical power and/or communication
signals between two otherwise weakly, stationary coupled coils in a
BHA may be accomplished in various embodiments that may leverage
resonantly tuned circuits and impedance matching techniques. In
this way, a wireless coupling may be provided between two fixed or
stationary tools so that a direct mechanical connection for power
and/or communications is not required when assembling the tools
together and while they are operated in a bore hole. A gap between
the tuned coils may exist and does not degrade performance of power
and communications transfer between the coil. To compensate for any
potential flux leakage, embodiments resonate inductively coupled
primary and secondary coils at the same frequency. Further, in some
embodiments, the source resistance is matched to the transmitting
coil impedance and the load resistance is matched to the receiving
coil impedance.
[0006] Power and/or communications may be transmitted through a
stationary annular coil to an inductively coupled stationary
second, mandrel coil (it is envisioned that various embodiments may
employ any combination of annular and mandrel coils). By using
resonantly tuned circuits and impedance matching techniques for the
stationary coils, power and/or communications may be transmitted
efficiently from one stationary coil to the other despite relative
movement/vibration and misalignment of the two stationary coils.
For example, to compensate for flux leakage, embodiments resonate
inductively coupled primary and secondary coils at the same
frequency.
[0007] Additionally, in some embodiments, the source resistance is
matched to the transmitting coil impedance and the load resistance
is matched to the receiving coil impedance.
[0008] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the Figures, like reference numerals refer to like parts
throughout the various views unless otherwise indicated. For
reference numerals with letter character designations such as
"102A" or "102B", the letter character designations may
differentiate two like parts or elements present in the same
figure. Letter character designations for reference numerals may be
omitted when it is intended that a reference numeral to encompass
parts having the same reference numeral in figures.
[0010] FIG. 1A is a diagram of a system for wireless drilling and
mining extenders in a drilling operation;
[0011] FIG. 1B is a diagram of a wellsite drilling system that
forms part of the system illustrated in FIG. 1A;
[0012] FIG. 2 is a schematic drawing depicting a primary or
transmitting circuit and a secondary or receiving circuit;
[0013] FIG. 3 is a schematic drawing depicting a primary or
transmitting circuit and a secondary or receiving circuit with
transformers having turn ratios N.sub.S:1 and N.sub.L:1 that may
used to match impedances;
[0014] FIG. 4 is a schematic drawing depicting an alternative
circuit to that which is depicted in FIG. 3 and having parallel
capacitors that are used to resonate the coils'
self-inductances;
[0015] FIGS. 5A-5B illustrate an embodiment of a receiving coil
inside a transmitting coil;
[0016] FIGS. 6-7 are graphs illustrating the variation in k versus
axial displacement of the receiving coil when x=0 is small and the
transverse displacement when z=0 produces very small changes in k
of given embodiments, respectively;
[0017] FIGS. 8-9 are graphs illustrating that power efficiency may
also be calculated for displacements from the center in the z
direction and in the x direction, respectively, of given
embodiments;
[0018] FIG. 10 is a graph illustrating that the sensitivity of the
power efficiency to frequency drifts may be relatively small in
some embodiments;
[0019] FIG. 11 is a graph illustrating that drifts in the
components values of some embodiments do not have a large effect on
the power efficiency of the embodiment;
[0020] FIG. 12 depicts a particular embodiment configured to
convert input DC power to a high frequency AC signal, f.sub.0, via
a DC/AC convertor;
[0021] FIG. 13 depicts a particular embodiment configured to pass
AC power through the coils;
[0022] FIG. 14 depicts a particular embodiment that includes
additional secondary coils configured to transmit and receive
data;
[0023] FIGS. 15A1-15C2 are diagrams of tools in a bottom hole
assembly of a drill string that are coupled via embodiments of a
wireless drilling and mining extender;
[0024] FIG. 16A illustrates a wireless power distribution scheme
between stationary tools that leverages alternating current ("AC")
to transmit power across various tools in a BHA that includes
wireless drilling and mining extenders; and
[0025] FIG. 16B illustrates wireless power distribution scheme
between stationary tools that leverages alternating current ("AC")
and direct current ("DC") to transmit power across various tools in
a BHA that includes wireless drilling and mining extenders.
DETAILED DESCRIPTION
[0026] The system described below mentions how power and/or
communications may flow from one drill collar to another. The
inventive system may transmit power and/or communications in either
direction and/or in both directions as understood by one of
ordinary skill in the art.
[0027] Referring initially to FIG. 1A, this figure is a diagram of
a system 102 for controlling and monitoring a drilling operation.
The system 102 includes a control module 101 that is part of a
controller 106. The system 102 also includes a drilling system 104,
which has a logging and control module 95, a bottom hole assembly
("BHA") 100, and wireless power and data connections 402. The
wireless power and data connections 402 may exist between several
elements of the BHA as will be explained below.
[0028] The controller 106 further includes a display 147 for
conveying alerts 110A and status information 115A that are produced
by an alerts module 110B and a status module 115B. The controller
106 in some instances may communicate directly with the drilling
system 104 as indicated by dashed line 99 or the controller 106 may
communicate indirectly with the drilling system 104 using the
communications network 142
[0029] The controller 106 and the drilling system 104 may be
coupled to the communications network 142 via communication links
103. Many of the system elements illustrated in FIG. 1A are coupled
via communications links 103 to the communications network 142.
[0030] FIG. 1B illustrates a wellsite drilling system 104 that
forms part of the system 102 illustrated in FIG. 1A. The wellsite
can be onshore or offshore. In this system 104, a borehole 11 is
formed in subsurface formations by rotary drilling in a manner that
is known to one of ordinary skill in the art. Embodiments of the
system 104 can also use directional drilling, as will be described
hereinafter. The drilling system 104 includes the logging and
control module 95 as discussed above in connection with FIG.
1A.
[0031] A drill string 12 is suspended within the borehole 11 and
has a bottom hole assembly ("BHA") 100 which includes a drill bit
105 at its lower end. The surface system includes platform and
derrick assembly 10 positioned over the borehole 11, the assembly
10 including a rotary table 16, kelly 17, hook 18 and rotary swivel
19. The drill string 12 is rotated by the rotary table 16,
energized by means not shown, which engages the kelly 17 at the
upper end of the drill string. The drill string 12 is suspended
from a hook 18, attached to a traveling block (also not shown),
through the kelly 17 and a rotary swivel 19 which permits rotation
of the drill string 12 relative to the hook 18. As is known to one
of ordinary skill in the art, a top drive system could
alternatively be used instead of the kelly 17 and rotary table 16
to rotate the drill string 12 from the surface. The drill string 12
may be assembled from a plurality of segments 125 of pipe and/or
collars threadedly joined end to end.
[0032] In the embodiment of FIG. 1B, the surface system further
includes drilling fluid or mud 26 stored in a pit 27 formed at the
well site. A pump 29 delivers the drilling fluid 26 to the interior
of the drill string 12 via a port in the swivel 19, causing the
drilling fluid to flow downwardly through the drill string 12 as
indicated by the directional arrow 8. The drilling fluid exits the
drill string 12 via ports in the drill bit 105, and then circulates
upwardly through the annulus region between the outside of the
drill string 12 and the wall of the borehole 11, as indicated by
the directional arrows 9. In this system as understood by one of
ordinary skill in the art, the drilling fluid 26 lubricates the
drill bit 105 and carries formation cuttings up to the surface as
it is returned to the pit 27 for cleaning and recirculation.
[0033] The BHA 100 of the illustrated embodiment may include a
logging-while-drilling ("LWD") module 120, a
measuring-while-drilling ("MWD") module 130, a roto-steerable
system ("RSS") and motor 150 (also illustrated as 280 in FIG. 15
described below), and drill bit 105.
[0034] The LWD module 120 is housed in a special type of drill
collar, as is known to one of ordinary skill in the art, and can
contain one or a plurality of known types of logging tools. It will
also be understood that more than one LWD 120 and/or MWD module 130
can be employed, e.g. as represented at 120A. (References,
throughout, to a module at the position of 120A can alternatively
mean a module at the position of 120B as well.) The LWD module 120
includes capabilities for measuring, processing, and storing
information, as well as for communicating with the surface
equipment. In the present embodiment, the LWD module 120 includes a
directional resistivity measuring device.
[0035] The MWD module 130 is also housed in a special type of drill
collar, as is known to one of ordinary skill in the art, and can
contain one or more devices for measuring characteristics of the
drill string 12 and drill bit 105. The MWD module 130 may further
include an apparatus (not shown) for generating electrical power to
the BHA 100.
[0036] This apparatus may include a mud turbine generator powered
by the flow of the drilling fluid 26, it being understood by one of
ordinary skill in the art that other power and/or battery systems
may be employed. In the embodiment, the MWD module 130 includes one
or more of the following types of measuring devices: a
weight-on-bit measuring device, a torque measuring device, a
vibration measuring device, a shock measuring device, a stick slip
measuring device, a direction measuring device, and an inclination
measuring device.
[0037] The foregoing examples of wireline and drill string
conveyance of a well logging instrument are not to be construed as
a limitation on the types of conveyance that may be used for the
well logging instrument. Any other conveyance known to one of
ordinary skill in the art may be used, including without
limitation, slickline (solid wire cable), coiled tubing, well
tractor and production tubing.
[0038] FIG. 2 is a schematic drawing depicting a primary or
transmitting circuit 210 and a secondary or receiving circuit 220.
In this description, the time dependence is assumed to be
exp(j.omega.t) where .omega.=2.pi.f and f is the frequency in
Hertz. Returning to the FIG. 2 illustration, the transmitting coil
is represented as an inductance L.sub.1 and the receiving coil as
L.sub.2. In the primary circuit 210, a voltage generator with
constant output voltage V.sub.S and source resistance R.sub.S
drives a current I.sub.1 through a tuning capacitor C.sub.1 and
primary coil having self-inductance L.sub.1 and series resistance
R.sub.1. The secondary circuit 220 has self-inductance L.sub.2 and
series resistance R.sub.2. The resistances, R.sub.1 and R.sub.2,
may be due to the coils' wires, to losses in the coils magnetic
cores (if present), and to conductive materials or mediums
surrounding the coils. The Emf (electromotive force) generated in
the receiving coil is V.sub.2, which drives current I.sub.2 through
the load resistance R.sub.L and tuning capacitor C.sub.2. The
mutual inductance between the two coils is M, and the coupling
coefficient k is defined as:
k=M/ {square root over (L.sub.1L.sub.2)} (1)
[0039] While a conventional inductive coupler has k.apprxeq.1,
weakly coupled coils may have a value for k less than 1 such as,
for example, less than or equal to about 0.9. To compensate for
weak coupling, the primary and secondary coils in the various
embodiments are resonated at the same frequency. The resonance
frequency is calculated as:
.omega. 0 = 1 L 1 C 1 = 1 L 2 C 2 ( 2 ) ##EQU00001##
[0040] At resonance, the reactance due to L.sub.1 is cancelled by
the reactance due to C.sub.1. Similarly, the reactance due to
L.sub.2 is cancelled by the reactance due to C.sub.2. Efficient
power transfer may occur at the resonance frequency,
f.sub.0=.omega..sub.0/2.pi.. In addition, both coils may be
associated with high quality factors, defined as:
Q 1 = .omega. L 1 R 1 and Q 2 = .omega. L 2 R 2 . ( 3 )
##EQU00002##
[0041] The quality factors, Q, may be greater than or equal to
about 10 and in some embodiments greater than or equal to about
100. As is understood by one of ordinary skill in the art, the
quality factor of a coil is a dimensionless parameter that
characterizes the coil's bandwidth relative to its center frequency
and, as such, a higher Q value may thus indicate a lower rate of
energy loss as compared to coils with lower Q values.
[0042] If the coils are loosely coupled such that k<1, then
efficient power transfer may be achieved provided the figure of
merit, U, is larger than one such as, for example, greater than or
equal to about 3:
U=k {square root over (Q.sub.1Q.sub.2)}>>1. (4)
[0043] The primary and secondary circuits are coupled together
via:
V.sub.1=j.omega.L.sub.1I.sub.1+j.omega.M I.sub.2 and
V.sub.2=j.omega.L.sub.2I.sub.2+j.omega.M I.sub.1, (5)
where V.sub.1 is the voltage across the transmitting coil. Note
that the current is defined as clockwise in the primary circuit and
counterclockwise in the secondary circuit. The power delivered to
the load resistance is:
P.sub.L=1/2R.sub.L|I.sub.2|.sup.2, (6)
while the maximum theoretical power output from the fixed voltage
source V.sub.S into a load is:
P MAX = V S 2 8 R S . ( 7 ) ##EQU00003##
[0044] The power efficiency is defined as the power delivered to
the load divided by the maximum possible power output from the
source,
.eta. .ident. P L P MAX . ( 8 ) ##EQU00004##
[0045] In order to optimize the power efficiency, .eta., the source
resistance may be matched to the impedance of the rest of the
circuitry. Referring to FIG. 2, Z.sub.1 is the impedance looking
from the source toward the load and is given by:
Z 1 = R 1 - j / ( .omega. C 1 ) + j .omega. L 1 + .omega. 2 M 2 R 2
+ R L + j .omega. L 2 - j / ( .omega. C 2 ) ( 9 ) ##EQU00005##
[0046] When .omega.=.omega..sub.0, Z.sub.1 is purely resistive and
may equal R.sub.S for maximum efficiency.
Z 1 = R 1 + .omega. 2 M 2 R 2 + R L .ident. R S . ( 10 )
##EQU00006##
[0047] Similarly, the impedance seen by the load looking back
toward the source is
Z 2 = R 2 - j / ( .omega. C 2 ) + j .omega. L 2 + .omega. 2 M 2 R 1
+ R S + j .omega. L 1 - j / ( .omega. C 1 ) ( 11 ) ##EQU00007##
[0048] When .omega.=.omega..sub.0, Z.sub.2 is purely resistive and
R.sub.L should equal Z.sub.2 for maximum efficiency
Z 2 = R 2 + .omega. 2 M 2 R 1 + R S .ident. R L . ( 12 )
##EQU00008##
[0049] The power delivered to the load is then:
P L = 1 2 R L .omega. 0 2 M 2 V S 2 [ ( R S + R 1 ) ( R 2 + R L ) +
.omega. 0 2 M 2 ] 2 , ( 13 ) ##EQU00009##
and the power efficiency is the power delivered to the load divided
by the maximum possible power output,
.eta. .ident. P L P MAX = 4 R S R L .omega. 0 2 M 2 [ ( R S + R 1 )
( R 2 + R L ) + .omega. 0 2 M 2 ] 2 . ( 14 ) ##EQU00010##
[0050] The optimum values for R.sub.L and R.sub.L may be obtained
by simultaneously solving
R S = R 1 + .omega. 2 M 2 R 2 + R L and R L = R 2 + .omega. 2 M 2 R
1 + R S , ( 15 ) ##EQU00011##
with the result that:
R.sub.S=R.sub.1 {square root over (1+k.sup.2Q.sub.1Q.sub.2)} and
R.sub.L=R.sub.2 {square root over (1+k.sup.2Q.sub.1Q.sub.2)}.
(16)
[0051] If the source and load resistances do not satisfy equations
(16), then it is envisioned that standard methods may be used to
transform the impedances. For example, as shown in the FIG. 3
illustration, transformers with turn ratios N.sub.S:1 and N.sub.L:1
may be used to match impedances as per equations (16).
Alternatively, the circuit illustrated in FIG. 4 may be used. In
such an embodiment in FIG. 4, parallel capacitors are used to
resonate the coils' self-inductances according to equation (2). As
before, Z.sub.1 is defined as the impedance seen by the source
looking toward the load, while Z.sub.2 is defined as the impedance
seen by the load looking toward the source. In addition, there are
two matching impedances, Z.sub.S and Z.sub.T which may be used to
cancel any reactance that would otherwise be seen by the source or
load. Hence Z.sub.1 and Z.sub.2 are purely resistive with the
proper choices of Z.sub.S and Z.sub.T. Notably, the source
resistance R.sub.S may equal Z.sub.1, and the load resistance
R.sub.L may equal Z.sub.2. The procedures for optimizing efficiency
with series capacitance or with parallel capacitance may be the
same, and both approaches may provide high efficiencies.
[0052] Turning now to FIGS. 5A and 5B, a cross sectional view of
two coils 232, 234 is illustrated in FIG. 5A and a side view of the
two coils 232, 234 is illustrated in FIG. 5B. In these two figures,
a receiving coil 232 inside a transmitting coil 234 of a particular
embodiment 230 is depicted. The receiving coil 232 includes a
ferrite rod core 235 that, in some embodiments, may be about 12.5
mm (about 0.49 inch) in diameter and about 96 mm (about 3.78
inches) long with about thirty-two turns of wire 237. Notably,
although specific dimensions and/or quantities of various
components may be offered in this description, it will be
understood by one of ordinary skill in the art that the embodiments
are not limited to the specific dimensions and/or quantities
described herein.
[0053] Returning to FIG. 5, the transmitting coil 234 may include
an insulating housing 236, about twenty-five turns of wire 239, and
an outer shell of ferrite 238. The wall thickness of the ferrite
shell 238 in the FIG. 5 embodiment may be about 1.3 mm (about 0.05
inch). In certain embodiments, the overall size of the transmitting
coil 234 may be about 90 mm (about 3.54 inch) in diameter by about
150 mm (about 5.90 inches) long. The receiving coil 232 may reside
inside the transmitting coil 234, which is annular.
[0054] The receiving coil 232 may be free to move in the axial (z)
direction or in the transverse direction (x) with respect to the
transmitting coil 234. In addition, the receiving coil 232 may be
able to rotate on axis with respect to the transmitting coil 234.
The region between the two coils 232, 234 may be filled with air,
fresh water, salt water, oil, natural gas, drilling fluid (known as
"mud"), or any other liquid or gas. The transmitting coil 234 may
also be mounted inside a metal tube, with minimal affect on the
power efficiency because the magnetic flux may be captured by, and
returned through, the ferrite shell 238 of the transmitting coil
234.
[0055] The operating frequency for these coils 232, 234 may vary
according to the particular embodiment, but, for the FIG. 5 example
230, a resonant frequency f=about 100 kHz may be assumed. At this
frequency, the transmitting coil 234 properties are:
L.sub.1=6.7610.sup.-5 Henries and R.sub.1=0.053 ohms, and the
receiving coil 232 properties are L.sub.2=7.5510.sup.-5 Henries and
R.sub.2=0.040 ohms. The tuning capacitors are C.sub.1=3.7510.sup.-8
Farads and C.sub.2=3.3610.sup.-8 Farads. Notably, the coupling
coefficient k value depends on the position of the receiving coil
232 inside the transmitting coil 234. The receiving coil 232 is
centered when x=0 and z=0 and there is k=0.64.
[0056] The variation in k versus axial displacement of the
receiving coil 232 when x=0 may be relatively small, as illustrated
by the graph 250 in FIG. 6. The transverse displacement when z=0
may produce very small changes ink, as illustrated by the graph 252
in FIG. 7. The receiving coil 232 may rotate about the z-axis
without affecting k because the coils are azimuthally symmetric.
According to equations (16), an optimum value for the source
resistance may be R.sub.S=32 ohms, and for the load resistance may
be R.sub.L=24 ohms when the receiving coil 232 is centered at x=0
and z=0. The power efficiency may thus be .eta.=99.5%.
[0057] The power efficiency may also be calculated for
displacements from the center in the z direction in mm (as
illustrated by the graph 254 in FIG. 8) and in the x direction in
mm (as illustrated by the graph 256 in FIG. 9). It is envisioned
that the efficiency may be greater than about 99% for axial
displacements up to about 20.0 mm (about 0.79 inch) in certain
embodiments, and greater than about 95% for axial displacements up
to about 35.0 mm (about 1.38 inches). It is further envisioned that
the efficiency may be greater than 98% for transverse displacements
up to 20.0 mm (about 0.79 inch) in some embodiments. Hence, the
position of the receiving coil 232 inside the transmitting coil 234
may vary in some embodiments without reducing the ability of the
two coils 232, 234 to efficiently transfer power.
[0058] Referring now to FIG. 10, it can be seen in the illustrative
graph 258 where the Y-axis denotes efficiency in percentage and the
X-axis denotes frequency in Hz that the sensitivity of the power
efficiency to frequency drifts may be relatively small. A .+-.10%
variation in frequency may produce minor effects, while the coil
parameters may be held fixed. The power efficiency at 90,000 Hz is
better than about 95%, and the power efficiency at 110,000 Hz is
still greater than about 99%. Similarly, drifts in the component
values may not have a large effect on the power efficiency. For
example, both tuning capacitors C.sub.1 and C.sub.2 are allowed to
increase by about 10% and by about 20% as illustrated in the graph
260 of FIG. 11. Notably, the other parameters are held fixed,
except for the coupling coefficient k. The impact of the power
efficiency is negligible. As such, the system described herein
would be understood by one of ordinary skill in the art to be
robust.
[0059] It is also envisioned that power may be transmitted from the
inner coil to the outer coil of particular embodiments,
interchanging the roles of transmitter and receiver. It is
envisioned that the same power efficiency would be realized in both
cases.
[0060] Referring to FIG. 12, an electronic configuration 262 is
illustrated for converting input DC power to a high frequency AC
signal, f.sub.0, via a DC/AC convertor. The transmitter circuit in
the configuration 262 excites the transmitting coil at resonant
frequency f.sub.0. The receiving circuit drives an AC/DC convertor,
which provides DC power output for subsequent electronics. This
system 262 is appropriate for efficient passing DC power across the
coils.
[0061] Turning to FIG. 13, AC power can be passed through the
coils. Input AC power at frequency f.sub.1 is converted to resonant
frequency f.sub.0 by a frequency convertor. Normally this would be
a step up convertor with f.sub.0>>f.sub.1. The receiver
circuit outputs power at frequency f.sub.0, which is converted back
to AC power at frequency f.sub.1. Alternatively, as one of ordinary
skill in the art recognizes, the FIG. 13 embodiment 264 could be
modified to accept DC power in and produce AC power out, and vice
versa.
[0062] In lieu of, or in addition to, passing power, data signals
may be transferred from one coil to the other in certain
embodiments by a variety of means. In the above example, power is
transferred using an about 100.0 kHz oscillating magnetic field. It
is envisioned that this oscillating signal may also be used as a
carrier frequency with amplitude modulation, phase modulation, or
frequency modulation used to transfer data from the transmitting
coil to the receiving coil. Such would provide a one-way data
transfer.
[0063] An alternative embodiment includes additional secondary
coils to transmit and receive data in parallel with any power
transmissions occurring between the other coils described above, as
illustrated in FIG. 14. Such an arrangement may provide two-way
data communication in some embodiments. The secondary data coils
266, 268 may be associated with relatively low power efficiencies
of less than about 10%. It is envisioned that in some embodiments
the data transfer may be accomplished with a good signal to noise
ratio, for example, about 6.0 dB or better. The secondary data
coils 266, 268 may have fewer turns than the power transmitting 234
and receiving coils 232.
[0064] The secondary data coils 266, 268 may be orthogonal to the
power coils 232, 234, as illustrated in FIG. 14. For example, the
magnetic flux from the power transmitting coils 232, 234 may be
orthogonal to a first data coil 266, so that it does not induce a
signal in the first data coil 266. A second data coil 268 may be
wrapped as shown in FIG. 14 such that magnetic flux from the power
transmitters does not pass through it, but magnetic flux from first
data coil 266 does. Notably, the configuration depicted in FIG. 14
is offered for illustrative purposes only and is not meant to
suggest that it is the only configuration that may reduce or
eliminate the possibility that a signal will be induced in one or
more of the data coils by the magnetic flux of the power
transmitting coils. Other data coil configurations that may
minimize the magnetic flux from the power transmitter exciting the
data coils will occur to those with ordinary skill in the art.
[0065] Moreover, it is envisioned that the data coils 266, 268 may
be wound on a non-magnetic dielectric material in some embodiments.
Using a magnetic core for the data coils 266, 268 might result in
the data coils' cores being saturated by the strong magnetic fields
used for power transmission. Also, the data coils 266, 268 may be
configured to operate at a substantially different frequency than
the power transmission frequency. For example, if the power is
transmitted at about 100.0 kHz in a certain embodiment, then the
data may be transmitted at a frequency of about 1.0 MHz or higher.
In such an embodiment, high pass filters on the data coils 266, 268
may prevent the about 100.0 kHz signal from corrupting the data
signal. In still other embodiments, the data coils 266, 268 may
simply be located away from the power coils 232, 234 to minimize
any interference from the power transmission. It is further
envisioned that some embodiments may use any combination of these
methods to mitigate or eliminate adverse effects on the data coils
266, 268 from the power transmission of the power coils 232,
234.
[0066] FIGS. 15A1-16C2 are diagrams of tools 305, 310 in a bottom
hole assembly 100 of a drill string 12 that are coupled via
embodiments of a wireless drilling and mining ("D&M") extender
301. Advantageously, a wireless D&M extender 301 provides for
replacement of a physical pin connection of the conventional art
with a stationary tuned-inductive coupler mechanism configured to
pass power and data communication transmissions from tool to tool.
As is understood by one of ordinary skill in the art of inductive
coupling or magnetic coupling, a change in current flow through one
coil may induce a voltage across an adjacent coil through
electromagnetic induction.
[0067] The amount of inductive coupling between two conductors is
measured by their mutual inductance. Inductive coupling may be
leveraged in this manner between two wires, however one of ordinary
skill in the art will recognize that the coupling between two wires
can be increased by winding them into coils and placing them close
together on a common axis, so the magnetic field of one coil passes
through an and in and me the other coil.
[0068] It is envisioned that embodiments of a wireless D&M
extender may include separate stationary coils or wires for power
and data communications transmission. Power exchanged between the
stationary coils would have a frequency in hundreds of kiloHertz
(kHz) while data transmissions between the stationary coils would
likely occur in the megahertz (MHz) range as understood by one of
ordinary skill in the art.
[0069] As described above, smaller stationary coils, such as coils
266, 268 of FIG. 14 would be used in conjunction with larger coils
232, 234. The smaller stationary coils 266, 268 may transmit data
communications while the stationary larger coils 232, 234 would
transmit power signals. As understood by one of ordinary skill the
art, the larger coils 232, 234 and the smaller coils 266, 268 may
share a common ferrite core 235 such that one ferrite core 235 has
two sets of coils: one coil having a higher number of windings for
power transfer while a second coil has a lower number of windings
for data transfer.
[0070] Returning to FIGS. 15A1-15C2, FIG. 15A1 depicts a
stationary/fixed "mandrel to mandrel" embodiment of a wireless
D&M extender 301A for stationary tools that do not move,
translate, or rotate relative to each other. In the FIG. 15A1
embodiment, tool 310A includes a mandrel type coil 311A that is
communicatively coupled to a mandrel type coil 306A of tool 305A
via a tuned-inductive coupler arrangement. As explained above,
power and/or data communications may be transmitted between tools
305A, 310A via inductive coupling between coils 306A, 311A for tool
305, 310 that are generally fixed or do not move relative to each
other.
[0071] Advantageously, although stationary coils 306A, 311A may be
juxtaposed such that a change in current flow in one coil induces a
voltage in the other, the coils 306A, 311A are not required to be
mechanically coupled or rigidly aligned when the tools 305, 311 are
connected together. That is, it is envisioned that in a wireless
D&M extender, a gap (not easily seen in FIG. 15A1 but see FIG.
15A2) may exist between coils 306A and 311A even though the tools
305, 310 may have a fixed coupling 323 (see FIG. 15A2), such as
screw threads, rivets, or welds for engaging each other. As such,
mechanical wear, misalignment, and/or vibration in the physical
connections between various tools 305A, 310A of a given BHA may not
adversely affect or otherwise cause the failure of the
communications bus.
[0072] FIG. 15A2 depicts an enlarged view of the stationary
"mandrel to mandrel" embodiment of a wireless D&M extender
301A. The fixed coupling 323 between the two tools 310A and 305A,
in which the first tool 310A may include a drill collar pin
connection while the second tool 305A may include a drill collar
box connection, is illustrated in further detail. The coupling 323
between tools 305, 310 may include screw threads and/or other
secure mechanical fasteners, like bolts, screws, rivets, welds, and
other similar fasteners as understood by one of ordinary skill the
art. The coupling 323 is designed to provide a rigid and non-moving
connection between the tools 305, 310.
[0073] Meanwhile, the stationary coils 311A, 306A may be coupled to
respective and extenders 1605. The extenders 1605 may be coupled to
respective pressure housings (not illustrated) which enclose or
shield electronics that generate at least one of communication
signals and power signals. The extender 1605 may be made from a
metal that is non-magnetic, such as stainless steel. A gap distance
g may exist between the two coils 311C, 306C. The gap distance g is
usually not greater than twice the diameter T of a respective
ferrite core 235.
[0074] In the FIG. 15B embodiment, tool 310B includes an annular
type coil 311B that is communicatively coupled to a mandrel type
coil 306B of tool 305B via a tuned-inductive coupler arrangement.
As explained above, power and/or data communications may be
transmitted between tools 305B, 310B via inductive coupling between
coils 306B, 311B. Advantageously, although coils 306B, 311B are
positioned juxtaposed such that a change in current flow in one
coil induces a voltage in the other, the coils 306B, 311B are not
required to be mechanically coupled or rigidly aligned.
[0075] That is, it is envisioned that in a wireless D&M
extender, a gap 315 may exist between coils 306B and 311B. As such,
mechanical wear, misalignment, and/or vibration in the physical
connections between various tools 305B, 310B of a given BHA may not
adversely affect or otherwise cause the failure of the
communications bus. The stationary annular type coil 311B is
described in more detail above in connection with FIGS. 5A-5B.
[0076] In the FIG. 15C1 embodiment, tool 310C includes a stationary
annular type coil 311C that is communicatively coupled to a
stationary annular type coil 306C of tool 305C via a
tuned-inductive coupler arrangement. As explained above, power
and/or data communications may be transmitted between tools 305C,
310C via inductive coupling between coils 306C, 311C.
Advantageously, although coils 306C, 311C are juxtaposed such that
a change in current flow in one coil induces a voltage in the
other, the coils 306C, 311C are not required to be mechanically
coupled or rigidly aligned.
[0077] That is, it is envisioned that in a wireless D&M
extender, a gap (not easily seen in FIG. 15C1 but see FIG. 15C2)
may exist between coils 306C and 311C. As such, mechanical wear,
misalignment, and/or vibration in the physical connections between
various tools 305C, 310C of a given BHA may not adversely affect or
otherwise cause the failure of the communications bus.
[0078] FIG. 15C2 provides an enlarged view of the stationary
annular type coil 311C that is communicatively coupled to a
stationary annular type coil 306C of tool 305C in FIG. 15C1. The
ferrite cores 235 of this arrangement may have a hollow cylindrical
shape. As noted previously, a gap distance g may exist between the
two coils 311C, 306C. The gap distance g is usually not greater
than twice the thickness T of a respective ferrite core 235.
[0079] FIG. 16A illustrates a wireless power distribution scheme
402 between two stationary tools such as a MWD 130 and a LWD 120
that leverages alternating current ("AC") to transmit power in a
BHA 100. In the FIG. 16A illustration, MWD tool 130 is the power
source for LWD tool 120. The power is generated in MWD tool 130 via
a turbine 425, although other power sources such as, but not
limited to, batteries are envisioned. The power generated by
turbine 425 is supplied through AC/DC module 420 and switching amp
415 to source resonators 410 and 430. The source resonators 410,
430 may be leveraged to wirelessly transmit power and/or data
communications to a receiving device resonator in a juxtaposed
tool, such as device resonator 440 in LWD tool 120. The
transmissions are then used within LWD tool 120 and relayed to
subsequent tools in the given BHA via source resonator 450.
[0080] FIG. 16B illustrates a wireless power distribution scheme
402 between two stationary tools like a MWD 130 and LWD 120 that
leverages alternating current ("AC") and direct current ("DC") to
transmit power in a BHA 100. The wireless power distribution scheme
402 largely mirrors that of scheme 402 in FIG. 16A with the
exception that the AC transmission is converted within LWD tool 120
to DC and then back to AC for subsequent transmission to other
tools via source resonator 450.
[0081] Although a few embodiments have been described in detail
above, those skilled in the art will readily appreciate that many
modifications are possible in the embodiments without materially
departing from this disclosure. Accordingly, such modifications are
intended to be included within the scope of this disclosure as
defined in the following claims. In the claims, means-plus-function
clauses are intended to cover the structures described herein as
performing the recited function and not only structural
equivalents, but also equivalent structures. Thus, although a nail
and a screw may not be structural equivalents in that a nail
employs a cylindrical surface to secure wooden parts together,
whereas a screw employs a helical surface, in the environment of
fastening wooden parts, a nail and a screw may be equivalent
structures. It is the express intention of the applicant not to
invoke 35 U.S.C. .sctn.112, sixth paragraph for any limitations of
any of the claims herein, except for those in which the claim
expressly uses the words `means for` together with an associated
function.
* * * * *