U.S. patent application number 14/443940 was filed with the patent office on 2015-11-05 for downhole electromagnetic telemetry system utilizing electrically insulating material and related methods.
The applicant listed for this patent is HALLIBURTON ENERGY SERVICES INC.. Invention is credited to David Lyle, Paul F. Rodney.
Application Number | 20150315906 14/443940 |
Document ID | / |
Family ID | 51021868 |
Filed Date | 2015-11-05 |
United States Patent
Application |
20150315906 |
Kind Code |
A1 |
Rodney; Paul F. ; et
al. |
November 5, 2015 |
Downhole Electromagnetic Telemetry System Utilizing Electrically
Insulating Material and Related Methods
Abstract
A downhole electromagnetic telemetry system and method whereby
electrically insulating material is placed above and/or below an
electrical current launching device or receiver along a well string
in order to extend the range of the telemetry system, increase the
telemetry rate, and/or reduce downhole power requirements.
Inventors: |
Rodney; Paul F.; (Spring,
TX) ; Lyle; David; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HALLIBURTON ENERGY SERVICES INC. |
Houston |
TX |
US |
|
|
Family ID: |
51021868 |
Appl. No.: |
14/443940 |
Filed: |
December 28, 2012 |
PCT Filed: |
December 28, 2012 |
PCT NO: |
PCT/US12/72080 |
371 Date: |
May 19, 2015 |
Current U.S.
Class: |
340/854.4 |
Current CPC
Class: |
E21B 47/16 20130101;
G01V 3/02 20130101; E21B 47/13 20200501; G01V 3/18 20130101 |
International
Class: |
E21B 47/16 20060101
E21B047/16 |
Claims
1. A method for utilizing an electromagnetic telemetry system in a
downhole well, the method comprising: providing a well string
comprising one or more tubulars attached to a bottom hole assembly,
the bottom hole assembly comprising at least one of an electrical
current launching device or a receiver; applying electrically
insulating material around one or more portions of the well string;
deploying the bottom hole assembly into the well; conducting an
electromagnetic telemetry operation using the bottom hole assembly;
and utilizing the electrically insulating material to reduce at
least one of: short circuits from the current launching device to
casing; or current leakage from the well string into the casing or
formation along the well.
2. A method as defined in claim 1, further comprising applying the
electrically insulating material around one or more portions of the
well string immediately above or below the current launching device
or receiver.
3. A method as defined in claim 1, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises wrapping the one or more portions of the
well string with one or more sheets of electrically insulating
material.
4. A method as defined in claim 1, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises positioning an insulation sleeve around
the one or more portions of the well string, the insulation sleeve
being comprised of electrically insulating swellable material.
5. A method as defined in claim 1, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises applying at least one of: an electrically
insulating swellable material; an electrically insulating
injection-molded coating; an electrically insulating spray coating;
or an electrically insulating anodized layer.
6. A method as defined in claim 1, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises: determining a length of an electrically
conductive portion of the formation along the well; and applying
the electrically insulating material based upon the determined
length.
7. An electromagnetic telemetry system for use in a downhole well,
the system comprising: a well string comprising one or more
tubulars attached to a bottom hole assembly, the bottom hole
assembly comprising at least one of an electrical current launching
device or a receiver; and electrically insulating material
positioned around one or more portions of the well string to reduce
at least one of: short circuits from the current launching device
to casing; or current leakage from the well string into the casing
or formation along the well.
8. A system as defined in claim 7, wherein the electrically
insulating material is positioned immediately above or below the
current launching device or receiver.
9. A system as defined in claim 7, wherein the electrical current
launching device is a gap sub assembly or a toroid.
10. A system as defined in claim 7, wherein the receiver is a gap
sub assembly or a toroid.
11. A system as defined in claim 7, wherein the electrically
insulating material is one or more sheets of electrically
insulating material.
12. A system as defined in claim 7, wherein the electrically
insulating material is an insulation sleeve.
13. A system as defined in claim 7, wherein the electrically
insulating material is at least one of: an electrically insulating
swellable material; an electrically insulating injection-molded
coating; an electrically insulating spray coating; or an
electrically insulating anodized layer.
14. A method for utilizing an electromagnetic telemetry system in a
downhole well, the method comprising: applying electrically
insulating material around one or more portions of a well string
comprising at least one of an electrical current launching device
or a receiver; deploying the well string into the well; and
utilizing the electrically insulating material to reduce at least
one of: short circuits from the current launching device to casing;
or current leakage from the well string into the casing or
formation along the well.
15. A method as defined in claim 14, further comprising applying
the electrically insulating material around one or more portions of
the well string immediately above or below the current launching
device or receiver.
16. A method as defined in claim 14, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises applying at least one of: an electrically
insulating swellable material; an electrically insulating
injection-molded coating; an electrically insulating spray coating;
or an electrically insulating anodized layer.
17. A method as defined in claim 14, wherein applying the
electrically insulating material around the one or more portions of
the well string comprises: determining a length of an electrically
conductive portion of the formation along the well; and applying
the electrically insulating material based upon the determined
length.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to electromagnetic
telemetry and, more specifically, to a downhole telemetry system in
which electrically insulating material is placed around one or more
portions of a well string in order to extend the range of the
telemetry system, increase the telemetry rate, and/or reduce
downhole power requirements.
BACKGROUND
[0002] Electromagnetic telemetry systems are used in downhole
operations to transmit and receive electromagnetic signals for a
variety of purposes. An electromagnetic telemetry transmitter
launches an electrical signal into drill pipe either by impressing
a potential difference across a section of drill collar connected
to the drill pipe or by launching a current on the drill string by
way of a toroid that is placed around a section of the drill
string.
[0003] However, when an electromagnetic transmitter is within
casing, signal losses can be excessive as the current on the pipe
jumps to the casing, thus launching part of the signal to the
casing, but also shorting part of the signal along the casing.
Furthermore, and especially when there is direct contact between
any part of the pipe and the casing, motion of the drill string can
cause intermittent contact and, thus, introduce a very significant
noise into the telemetry signal. Moreover, as the signal travels up
or down the pipe and/or casing, it is attenuated substantially as
current leaks into the formation surrounding the borehole. As a
result, the signal received at the surface or downhole receiver can
be attenuated to the point where the signal to noise ratio is not
high enough to allow for reliable communication, even at a data
rate of a few bits per second.
[0004] In view of the foregoing, there is a need in the art for a
cost effective method by which to extend the range of the telemetry
system and/or to prevent short circuits through the mud and into
the casing or directly into the casing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIGS. 1A and 1B illustrate a drilling rig and an
electromagnetic telemetry system 10 according to one or more
exemplary embodiments of the present invention; and
[0006] FIGS. 2A, 2B and 2C are graphs illustrating the signal
improvement effects of adding electrically insulating material
above and/or below the current launching device, according to one
or more exemplary embodiments of the present invention.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0007] Illustrative embodiments and related methodologies of the
present invention are described below as they might be employed in
a downhole telemetry system in which electrically insulating
material is placed around one or more portions of the well string.
In the interest of clarity, not all features of an actual
implementation or methodology are described in this specification.
Also, the "exemplary" embodiments described herein refer to
examples of the present invention. It will of course be appreciated
that in the development of any such actual embodiment, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which will vary from one
implementation to another. Moreover, it will be appreciated that
such a development effort might be complex and time-consuming, but
would nevertheless be a routine undertaking for those of ordinary
skill in the art having the benefit of this disclosure. Further
aspects and advantages of the various embodiments and related
methodologies of the invention will become apparent from
consideration of the following description and drawings.
[0008] As described herein, exemplary embodiments of the present
invention extend the range of an electromagnetic telemetry system
when the system is within a cased or uncased section of a well. To
achieve this objective, electrically insulating material is applied
to the well string immediately above and/or immediately below the
electrical current launching device (gap sub assembly or toroid,
for example) or receiver. In other embodiments, the electrically
insulating material may also cover the current launching device or
receiver. Accordingly, as the current launching device launches the
electrical signal into the drill pipe, the electrically insulating
material prevents the current from jumping to the casing either
directly or through the drilling mud, thus preventing or reducing
the severity of short circuits through the casing and/or electrical
current leakage into the formation in situations where casing is
not present around the transmitter, thereby improving the range
and/or signal to noise ratio of the telemetry system, and/or
reducing the power required by the system. Moreover, in those
embodiments where a downhole receiver is utilized, the electrically
insulating material acts to reduce current leakage from the well
string to the casing or formation during downlink operations.
[0009] In certain exemplary embodiments, the electrically
insulating material is one or more sheets of material wrapped
around the bottom hole assembly or drill pipe using an adhesive
backing. In others, for example, electrically insulating swellable
material or a variety of coatings may also be utilized. As a
result, the range of the electromagnetic telemetry system within
and without the cased section is increased by roughly the same
amount of pipe that is electrically insulated. Therefore, the data
rate of the electromagnetic telemetry system may also be increased
without the need for adding repeaters.
[0010] FIGS. 1A and 1B illustrate a drilling rig 12 and an
electromagnetic telemetry system 10 according to one or more
exemplary embodiments of the present invention. As understood in
the art, electromagnetic telemetry system 10 generates and/or
receives electromagnetic waves downhole. Electromagnetic telemetry
system 10 includes a bottom hole assembly 14, current launching
device 16 (gap sub assembly, for example) and tubular section 18
(referred to in combination as a well string, for example), all
extending down through casing 20 of well 22. The term "well
string," as used herein, may refer to a variety of deployment
strings such as, for example, drill string, coiled tubing,
production tubing, etc. In the exemplary embodiment of FIGS. 1A and
1B, the well string is a drill string.
[0011] In addition, electromagnetic telemetry system 10 includes a
receiver 24 electrically coupled to a ground reference 26, and may
also have one or more repeaters (not shown) along tubular 18 as
necessary. In general, electromagnetic telemetry system 10
communicates by launching a low frequency current (between about 1
and 30 Hz, for example) along tubular 18. Signals associated with
the current are then detected at the surface by receiver 24 where a
potential difference is measured between drilling rig 12 and ground
26. In this exemplary embodiment, electromagnetic telemetry system
10 may operate in, for example, a phase modulated carrier mode,
pulse position modulation mode or orthogonal frequency-division
multiplexing mode, or a number of other modulation modes, as will
be understood by those ordinarily skilled in the art having the
benefit of this disclosure.
[0012] In order to produce the current transmitted by
electromagnetic telemetry system 10, electrical current launching
device 16 is provided adjacent bottom hole assembly 14 (or may form
part of bottom hole assembly 14). In a first exemplary embodiment,
electrical current launching device 16 is provided as an electrical
break between bottom hole assembly 14 and tubular 18 which
effectively turns the well string into a large antenna. In the
exemplary embodiment of FIG. 1A, a gap sub assembly serves as the
electrical break or antenna. An electrical potential difference is
thereby created between bottom hole assembly 14 and tubular 18,
thus creating the transmitted current. As understood in the art,
the gap sub assembly is an electrical isolation joint designed to
withstand the high torsional, bending, tensile and compression
loads of electromagnetic telemetry system 10. However, in other
embodiments, electrical current launching device 16 may instead be
a toroid assembly, as understood in the art. These and other
aspects of electromagnetic telemetry system 10 will be readily
understood by those ordinarily skilled in the art having the
benefit of this disclosure.
[0013] Still referring to FIGS. 1A and 1B, tubular 18 has been
lowered through blow out preventer 28 down into well 22, and
through casing 20. As previously mentioned, in this exemplary
embodiment, tubular 18 is drill pipe forming part of a drill
string; however, in other embodiments, tubular 18 may be, for
example, coiled or production tubing utilized for some other
operation. Nevertheless, tubular 18 extends down to current
launching device 16 which is coupled to bottom hole assembly 14. A
drill bit 30 is positioned at the distal end of bottom hole
assembly 14. Drill bit 30 may be rotated by a variety of methods
including, for example, tubular 18 or a mud motor. In this
exemplary embodiment, bottom hole assembly 14 comprises a CPU (not
shown) and electromagnetic telemetry transmitter 32 that includes
electronics necessary to sense, detect and transmit electromagnetic
signals via current launching device 16, in addition to handling
other operations of bottom hole assembly 14, as understood in the
art.
[0014] In certain exemplary embodiments of electromagnetic
telemetry system 10, an electrically insulating material 34 is
applied around one or more portions of a drill string (tubular 18
or bottom hole assembly 14) above and/or below current launching
device 16. In one embodiment, the electrically insulating material
34 need not be a perfect insulator; rather, the resistivity of
electrically insulating material 34 is no less than two orders of
magnitude higher than that of the fluid (drilling mud, for example)
used during the downhole operation. Moreover, in certain
embodiments, it is also not necessary that electrically insulating
material 34 be without break along tubular 18 or bottom hole
assembly 14. Nevertheless, electrically insulating material 34 may
be a variety of materials, such as, for example, a swellable
material, injection-molded coating, bands, sleeves, stabilizers,
high oxygen fuel spray coating, anodized layers, etc. The swellable
material may be, for example, such materials as used in the Swell
Technology.TM. Systems, commercially available through the Assignee
of the present invention, Halliburton Energy Services, Co. or
Houston, Tex. In addition, the swellable material may be selected
based upon the mud type (oil or water based, for example) such
that, once contact has been made with the drilling mud, the
swellable material swells onto bottom hole assembly 14 and/or
tubular 18 and adheres to it.
[0015] As previously described, electrically insulating material 34
is applied to one or more portions of the well string (i.e.,
tubular 18 and bottom hole assembly 14) above and/or below the
current launching device 16. In one embodiment, electrically
insulating material 34 is applied immediately above and/or below
current launching device 16, as shown in FIGS. 1A and 1B. However,
in other embodiments, electrically insulating material 34 may also
be placed all along tubular 18 as desired. In certain exemplary
embodiments, electrically insulating material 34 may be applied as
a tape that is wrapped around one or more portions of bottom hole
assembly 14 as it is tripped into well 22. The electrically
insulating tape may be adhered along the well string by wetting it
with the same fluid (drilling mud, for example) that will be
utilized to cause it to swell. However, in other embodiments, an
adhesive backing may also be utilized on the tape to adhere it to
the well string. Exemplary insulating tapes may be, for example,
swellable materials, adhesive-backed rubber, silicone rubber,
Teflon, polyester films, polyimide tapes, polymer sheets
(polyethylene, for example). In certain embodiments, however, the
use of polyethylene would be limited to about 115.degree. C. since
a typical melting point for a polyethylene plastic is around
120.degree. C. Moreover, the tape may be one to several feet wide
and a fraction of an inch thick (1/8 inch, for example).
[0016] In an alternate embodiment, electrically insulating material
34 may be formed into a sleeve having an inner diameter somewhat
larger than that of the box-pin outer diameter of bottom hole
assembly 14 or tubular 18. In one example, the electrically
insulating sleeve would be applied along the well string as it is
tripped into well 22. The electrically insulating sleeve may be
held in place during deployment in a variety of ways such as, for
example, by applying clamps or tape to hold the electrically
insulating sleeve in place until the swellable material begins to
swell. In the alternative, the electrically insulating sleeve may
be snug enough around the well string portion to hold itself in
place until swelling begins. In addition, portions of the
electrically insulating sleeve may be wetted with drilling mud,
thus causing that portion of the sleeve to swell and adhere to the
well string. Nevertheless, after deployment, as the electrically
insulating sleeve comes into the contact with the drilling fluid,
the swellable material is then activated to swell against the
surface of bottom hole assembly 14 or tubular 18, thus adhering to
it. The swellable material may be selected, for example, based upon
the type of drilling mud utilized, as will be understood by those
ordinarily skilled in the art having the benefit of this
disclosure.
[0017] Moreover, still referring to FIGS. 1A and 1B, electrically
insulating material 34 may also be applied to one or more sections
of tubular 18 using any of the methods described herein. Such an
embodiment will minimize current loss during transmission along
tubular 18. In prior art telemetry systems, the current traveling
up the well string and casing tends to migrate off the well
string/casing and go to ground, thus resulting in signal loss.
However, through use of this alternate embodiment of the present
invention whereby one or more portions of tubular 18 are insulated
above current launching device 16, the amount of current going to
ground along tubular 18 is then reduced, which increases the amount
of current traveling back up the well string and reaching the
surface, thus resulting in a larger amplitude signal. In certain
embodiments, electrically insulating material 34 may be utilized
along bottom hole assembly 14 only, tubular 18 only, or in
combination along both bottom hole assembly 14 and tubular 18.
[0018] Additionally, in yet another alternative embodiment, an
electrically resistive fluid may be pumped into well 22 to assist
in electrically isolating electromagnetic telemetry system from
casing 22. Such fluid may be drill mud and or fluid additives added
to the fluid. In another embodiment, the electrically resistive
fluid may be utilized without electrically insulating material 34,
as will be understood by those ordinarily skilled in the art having
the benefit of this disclosure.
[0019] Although not shown in FIGS. 1A and 1B, exemplary embodiments
of present invention may also be utilized in downlink telemetry
systems which may only utilize a downhole receiver. As understood
in the art, electromagnetic telemetry system 10 may comprise a
receiver in place of current launching device 16 which is used to
receive signals transmitted from the surface via tubular 18. Such
an embodiment may or may not include electromagnetic telemetry
transmitter 32. In such embodiments, the receiver may be, for
example, a gap sub assembly or toroid as previously described.
However, unlike the previous embodiments described herein, the
receiver will instead receive and decode the signal in order to
perform some operation within bottom hole assembly 14. In such
embodiments, placement of electrically insulating material 34
around one or more portions of tubular 18 will reduce and/or
eliminate current leakage from tubular 18 into casing 20 or the
open hole formation, as will be understood by those ordinarily
skilled in the art having the benefit of this disclosure.
[0020] Now with reference to the graphs of FIGS. 2A-2C, the signal
improvement effects of adding electrically insulating material 34
above and/or below current launching device 16 will now be
described. The graphs plot the current on tubular 18 and casing 20
along various depths of well 22 wherein various lengths of
electrically insulating material 34 have been applied. FIG. 2A is a
plot of the current on tubular 18 and casing 20 in a 2,800 foot
well with 2,500 feet of drill pipe, 2,500 feet of casing, a 1 inch
gap sub assembly, at a depth of 1400 feet and using 0.25 ohm meter
mud. As can be seen, the current very rapidly bleeds off of the
pipe into casing 20 in such a way that a significant portion of the
current is no longer available as a signal, but instead has been
effectively shorted out by casing 20.
[0021] FIG. 2B is a plot of the current on tubular 18 and casing 20
in the same well as FIG. 2A, but with 400 feet of electrically
insulating material 34 along bottom hole assembly 14 below the 1
inch gap sub assembly. The mud resistivity is again 0.25 ohm
meters. As illustrated, current still quickly bleeds to casing 20
as soon as there is no electrically insulating material 34, but the
overall signal level is significantly improved. FIG. 2C is yet
another plot of the current along the well, but with 400 feet of
insulation above and 400 feet of insulation below a 1 inch gap sub
assembly. The mud resistivity is again 0.25 ohm meters. As before,
the current quickly leaks to casing 20 where the electrically
insulating material 34 ends, but the overall signal level is again
improved. Chart 1 below is a summary of these and other signal
levels that may be observed at the surface.
TABLE-US-00001 CHART I Voltage mv c V dB R mud Insulation to inf
dBm Ohm m Inches/feet 0.21972 73.1624 0.25 1'' 0.33617 69.4688 0.25
100 feet below gap 0.61561 64.2139 0.25 400 feet below gap 1.3439
57.433 0.25 800 feet centered on gap 0.33688 69.4505 2.5 1''
0.43331 67.2641 2.5 100 feet below gap 0.71538 62.9092 2.5 400 feet
below gap 1.4828 56.5782 2.5 800 feet centered on gap
As shown, the signal level in millivolts appears in the first
column, the signal level expressed as decibel millivolts appears in
the second column, the mud resistivity appears in the third column,
and a summary of the insulation appears in the fourth column.
Although the foregoing examples address embodiments utilizing
transmitters, the same types of gains in signal to noise ratio will
be present in embodiments utilizing downhole receivers, as will be
understood by those ordinarily skilled in the art having the
benefit of this disclosure.
[0022] In view of the foregoing, electrically insulating material
34 may be applied to the well string in a variety of ways. For
example, electrically insulating material 34 may be applied to one
or more portions of the well string as the well string is being
made up. In the alternative, one or more portions of the well
string may be insulated before the well string is made up.
Moreover, exemplary embodiments of the present invention may be
utilized in open and cased wells. In cased sections of the well,
electrical insulating material 34 reduces or prevents short
circuits from current launching device 16 into casing 20. In open
sections of the well, electrical insulating material 34 reduces or
prevents current leakage from the well string into the formation.
Accordingly, the up hole or down hole telemetry range of
electromagnetic telemetry system 10 is increased by a distance
roughly equal to the length of insulation applied and downhole
power requirements are reduced. Therefore, electromagnetic
telemetry is efficiently provided while drilling (or performing
other operations) with the telemetry transmitter inside and outside
the casing.
[0023] In addition, in those embodiments of the present invention
utilized inside cased wells, the portion of the well string below
current launching device 16 (or the receiver) may be insulated.
However, in those embodiments utilized along portions of wells that
are open to the formation, portions of the well string above
current launching device 16 (or the receiver) may be insulated. In
the latter embodiment, the length of one or more electrically
conductive portions of the formation along the open well may be
determined, and the length of electrically insulating material 34
is determined based upon the length of the conductive formation. As
understood in the art, the location of the electrically conductive
formations may be determined based upon, for example, resistivity
logs of other wells near the well under construction, as will be
understood by those ordinarily skilled in the art having the
benefit of this disclosure. Based upon the logged data, as well as
the planned well trajectory and how far the bit will be beyond the
conductive formation at a given time (in those embodiments utilized
in a drill string), those same skilled persons can readily
determine the length of electrically conductive material necessary
to be applied above current launching device 16 (or the receiver).
For example, if the well is a vertical well and the bit run is
planned to extend to a depth of 12,000 feet, the electromagnetic
transmitter is 200 feet above the drill bit, and a very conductive
formation extends from 10,000 to 11,000 feet, then 1,800 feet of
electrically insulating material 34 may be positioned above the
current launching device 16 so that once current launching device
16 passed the bottom of the conductive formation (i.e. once it was
beyond a depth of 11,000 feet), there would always be electrically
insulating material 34 between tubular 18 and the formation.
Nevertheless, in either embodiment, one or more portions of the
well string above and/or below current launching device 16 or the
receiver (not shown) may also be insulated.
[0024] An exemplary methodology of the present invention provides a
method for utilizing an electromagnetic telemetry system in a
downhole well, the method comprising providing a well string
comprising one or more tubulars attached to a bottom hole assembly,
the bottom hole assembly comprising at least one of an electrical
current launching device or a receiver; applying electrically
insulating material around one or more portions of the well string;
deploying the bottom hole assembly into the well; conducting an
electromagnetic telemetry operation using the bottom hole assembly;
and utilizing the electrically insulating material to reduce at
least one of short circuits from the current launching device to
casing or current leakage from the well string into the casing or
formation along the well. The conducted electromagnetic telemetry
operation may be, for example, transmitting and/or receiving
electromagnetic signals along the system. Another method further
comprises applying the electrically insulating material around one
or more portions of the well string immediately above or below the
current launching device or receiver. In another method, applying
the electrically insulating material around the one or more
portions of the well string comprises wrapping the one or more
portions of the well string with one or more sheets of electrically
insulating material.
[0025] In yet another, applying the electrically insulating
material around the one or more portions of the well string
comprises positioning an insulation sleeve around the one or more
portions of the well string, the insulation sleeve being comprised
of electrically insulating swellable material. In another, applying
the electrically insulating material around the one or more
portions of the well string comprises applying at least one of: an
electrically insulating swellable material; an electrically
insulating injection-molded coating; an electrically insulating
spray coating; or an electrically insulating anodized layer. In yet
another, applying the electrically insulating material around the
one or more portions of the well string comprises: determining a
length of an electrically conductive portion of the formation along
the well; and applying the electrically insulating material based
upon the determined length.
[0026] An exemplary embodiment of the present invention provides an
electromagnetic telemetry system for use in a downhole well, the
system comprising a well string comprising one or more tubulars
attached to a bottom hole assembly, the bottom hole assembly
comprising at least one of an electrical current launching device
or a receiver; and electrically insulating material positioned
around one or more portions of the well string to reduce at least
one of short circuits from the current launching device to casing;
or current leakage from the well string into the casing or
formation along the well. In another embodiment, the electrically
insulating material is positioned immediately above or below the
current launching device or receiver. In yet another, the
electrical current launching device is a gap sub assembly or a
toroid. In another, the receiver is a gap sub assembly or a toroid.
In another, the electrically insulating material is one or more
sheets of electrically insulating material. In yet another, the
electrically insulating material is an insulation sleeve. In
another, the electrically insulating material is at least one of:
an electrically insulating swellable material; an electrically
insulating injection-molded coating; an electrically insulating
spray coating; or an electrically insulating anodized layer.
[0027] Yet another exemplary methodology of the present invention
provides a method for utilizing an electromagnetic telemetry system
in a downhole well, the method comprising: applying electrically
insulating material around one or more portions of a well string
comprising at least one of an electrical current launching device
or a receiver; deploying the well string into the well; and
utilizing the electrically insulating material to reduce at least
one of short circuits from the current launching device to casing
or current leakage from the well string into the casing formation
along the well. Another method further comprises applying the
electrically insulating material around one or more portions of the
well string immediately above or below the current launching device
or receiver. In another, applying the electrically insulating
material around the one or more portions of the well string
comprises applying at least one of an electrically insulating
swellable material; an electrically insulating injection-molded
coating; an electrically insulating spray coating; or an
electrically insulating anodized layer. In yet another, applying
the electrically insulating material around the one or more
portions of the well string comprises determining a length of an
electrically conductive portion of the formation along the well;
and applying the electrically insulating material based upon the
determined length.
[0028] The foregoing disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed. Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the apparatus in use or operation in
addition to the orientation depicted in the figures. For example,
if the apparatus in the figures is turned over, elements described
as being "below" or "beneath" other elements or features would then
be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The apparatus may be otherwise oriented (rotated 90
degrees or at other orientations) and the spatially relative
descriptors used herein may likewise be interpreted
accordingly.
[0029] Although various embodiments and methodologies have been
shown and described, the invention is not limited to such
embodiments and methodologies and will be understood to include all
modifications and variations as would be apparent to one ordinarily
skilled in the art having the benefit of this disclosure. For
example, one or more repeaters may also form part of the telemetry
systems described herein and, in such cases, the same inventive
principles would be applicable, as will be understood by those same
ordinarily skilled persons. Therefore, it should be understood that
the invention is not intended to be limited to the particular forms
disclosed. Rather, the intention is to cover all modifications,
equivalents and alternatives falling within the spirit and scope of
the invention as defined by the appended claims.
* * * * *