U.S. patent application number 13/876462 was filed with the patent office on 2013-08-01 for device and method for using the device for "in situ" extraction of bitumen or ultraheavy oil from oil sand deposits.
The applicant listed for this patent is Dirk Diehl. Invention is credited to Dirk Diehl.
Application Number | 20130192820 13/876462 |
Document ID | / |
Family ID | 44764112 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130192820 |
Kind Code |
A1 |
Diehl; Dirk |
August 1, 2013 |
DEVICE AND METHOD FOR USING THE DEVICE FOR "IN SITU" EXTRACTION OF
BITUMEN OR ULTRAHEAVY OIL FROM OIL SAND DEPOSITS
Abstract
The device has at least one electrical conductor loop formed of
a feed conductor, a return conductor and an inductor connected
therebetween. At least the inductor is at least partially or
completely disposed in the oil sand deposit. The device further has
an alternating current generator that is electrically connected to
the at least one conductor loop by at least two electrical contact
points. The alternating current generator has a transformer with at
least one primary and at least one secondary winding. The at least
one secondary winding comprises a center tap to which a ground
potential U.sub.e is electrically connected.
Inventors: |
Diehl; Dirk; (Bubenreuth,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Diehl; Dirk |
Bubenreuth |
|
DE |
|
|
Family ID: |
44764112 |
Appl. No.: |
13/876462 |
Filed: |
September 26, 2011 |
PCT Filed: |
September 26, 2011 |
PCT NO: |
PCT/EP11/66651 |
371 Date: |
March 27, 2013 |
Current U.S.
Class: |
166/248 ;
166/65.1 |
Current CPC
Class: |
H05B 2214/04 20130101;
H05B 6/62 20130101; E21B 43/2401 20130101; E21B 43/2408 20130101;
E21B 43/305 20130101 |
Class at
Publication: |
166/248 ;
166/65.1 |
International
Class: |
E21B 43/24 20060101
E21B043/24 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2010 |
DE |
10 2010 041 434.4 |
Nov 8, 2010 |
DE |
10 2010 043 529.5 |
Claims
1-12. (canceled)
13. A device for in situ extraction of bitumen or ultraheavy oil
from oil sand deposits, comprising: at least one electrical
conductor loop, each including a forward conductor, a return
conductor and an inductor connected between the forward conductor
and the return conductor, at least the inductor being arranged at
least partially in the oil sound deposit; and an AC generator,
electrically connected to the at least one conductor loop via at
least two electrical contact points, the AC generator including a
transformer having at least one primary winding and at least one
secondary winding, the at least one secondary winding having a
center tap to which a ground potential is applied electrically.
14. The device as claimed in claim 13, wherein the ground potential
is applied one of passively to the center tap electrically via a
galvanic connection, and actively to the center tap using circuitry
via an electrical circuit.
15. A device for in situ extraction of bitumen or ultraheavy oil
from oil sand deposits, comprising: at least one electrical
conductor loop, each including a forward conductor, a return
conductor and an inductor connected between the forward conductor
and the return conductor, at least the inductor being arranged at
least partially in the oil sound deposit; and an AC generator,
electrically connected to the at least one conductor loop via at
least two electrical contact points, the AC generator including a
transformer having at least one primary winding and at least one
secondary winding, the at least one secondary winding, a ground
potential being applied electrically to the conductor loop at a
point spatially removed from the AC generator.
16. The device as claimed in claim 15, wherein the ground potential
is applied spatially on the inductor at a furthest point on the
conductor loop from the AC generator.
17. The device as claimed in claim 16, wherein the AC generator
applies a voltage of at least 10 kV via the inductor that
inductively heats the oil sand deposit.
18. The device as claimed in claim 17, wherein the transformer is a
matching transformer the voltage of at least 10 kV.
19. The device as claimed in claim 18, wherein the inductor has a
length greater than 1 km
20. The device as claimed in claim 19, wherein the inductor has a
length greater than 5 km.
21. The device as claimed in claim 19, wherein, except for where
the ground potential has been applied, the electrical conductor
loop is electrically insulated completely from the oil sand
deposit, so that application of the ground potential results in
heating of the oil sand deposit via the electrical conductor loop
purely inductively.
22. The device as claimed in claim 21, further comprising power
converters electrically connected to the primary winding, and
wherein the at least one primary winding is DC-isolated from the at
least one secondary winding.
23. The device as claimed in claim 22, wherein the AC generator is
an HF generator with an electrical power of greater than 1 MW at 5
to 200 kHz
24. The device as claimed in claim 23, wherein the AC generator is
an HF generator with an electrical power of greater than 1 MW at
substantially 50 kHz.
25. A method for in situ extraction of bitumen or ultraheavy oil
from oil sand deposits, comprising: installing a device with at
least one electrical conductor loop, each including a forward
conductor, a return conductor and an inductor connected between the
forward conductor and the return conductor, at least the inductor
being arranged at least partially in the oil sound deposit; and an
AC generator, electrically connected to the at least one conductor
loop via at least two electrical contact points, the AC generator
including a transformer having at least one primary winding and at
least one secondary winding, the at least one secondary winding
having a center tap; and applying the ground potential at one of
the center tap of the secondary winding and a point on the
conductor loop spatially removed from the AC generator, so that a
voltage between the at least two electrical contact points is lower
than an output voltage without the ground potential applied.
26. The method as claimed in claim 23, wherein said applying
results in the voltage between the at least two electrical contact
points being substantially half the output voltage without the
ground potential applied.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. national stage of International
Application No. PCT/EP11/066651, filed Sep. 26, 2011 and claims the
benefit thereof. The International Application claims the benefit
of German Application No. 102010041434.4 filed on Sep. 27, 2010 and
German Application No. 102010043529.5 filed on Nov. 8, 2010, all
applications are incorporated by reference herein in their
entirety.
BACKGROUND
[0002] Described below is a device and a method for using the
device for the "in situ" extraction of bitumen or ultraheavy oil
from oil sand deposits. The device includes at least one electrical
conductor loop, which has a forward conductor and a return
conductor and an inductor connected therebetween, wherein at least
the inductor is arranged at least partially or completely in the
oil sand deposit. Furthermore, the device includes an AC generator,
which is electrically connected to the at least one conductor loop
via at least two electrical contact points. The AC generator
includes a transformer having at least one primary winding and at
least one secondary winding.
[0003] Bitumen or ultraheavy oil can be removed from oil sand or
oil shale deposits (merely referred to below as oil sand deposits
or reservoirs for reasons of simplicity) in mining or by "in situ"
extraction. "In situ" extraction includes the introduction of
solvents or thinners and/or the heating of the ground of the oil
sand deposits in order to make the ultraheavy oil or bitumen
free-flowing or to be able to pump away the ultraheavy oil or
bitumen. A much used procedure for "in situ" extraction is based on
the SAGD (Steam Assisted Gravity Drainage) method. In this case,
steam is introduced at elevated pressure into the ground through a
pipe running horizontally within the reservoir. The heated,
free-flowing ultraheavy oil or bitumen trickles to a second pipe,
for example one which is approximately 5 m deeper, by which it is
pumped away or conveyed.
[0004] DE 102007040605 B3 discloses a method in which the heating
of the ground of an oil sand deposit takes place inductively via an
electrical/electromagnetic heating method. With the method, heating
of unconventional heavy oil with viscosities of, for example,
5.degree. API to 15.degree. API from temperatures of approximately
10.degree. C. ambient temperature up to 280.degree. C. is possible.
As a result, the oil can flow in a gravitational process, owing to
the improvement in the fluidity, to the lower impermeable boundary
layer of the reservoir and from there can flow away by known
drainage production pipes in order to either be pumped to the
Earth's surface by lift pumps or to be conveyed to the surface,
overcoming the force of gravity, by the pressure built up in the
reservoir by heating and/or introduction of steam.
[0005] The electromagnetic heating process can in particular be
combined with a steam process, which ensures improved permeability
and/or conductivity. It is also possible for the steam stimulation
by the production pipe to be allowed to take place cyclically at
the beginning of the heating phase or later.
[0006] The electrical/electromagnetic heating method is implemented
with the aid of at least one electrical conductor loop, which is
supplied electrical power or AC current/voltage by an AC generator.
As a result, "in situ" extraction below the surface to depths of up
to several 100 meters is possible. The conductor loop in
conjunction with the AC generator forms, in the state in which
current is flowing, a resonant circuit, which produces an
alternating magnetic field in the environment of the conductor loop
in the reservoir, by which alternating magnetic field eddy currents
are produced in the environment of the conductor loop. The eddy
currents result in heating of the reservoir and therefore in
liquefaction of the ultraheavy oil or bitumen.
[0007] In order to achieve a good heating power in the MW range,
the conductor loop needs to be supplied an electrical voltage of up
to 10 kV or even greater by the AC generator. This means that the
electrical voltage of up to 10 kV or higher is present at
connection terminals, which electrically connect the conductor loop
to the AC generator, and that the voltage can drift freely towards
the ground potential. In order to reliably prevent electrical
flashovers or arcs from a connection of the conductor loop to the
surrounding ground, a dielectric strength which is higher than the
maximum clamping voltage by a factor X, which may be 2 to 10, for
example, should be provided. This results in a high degree of
complexity in terms of insulation and high costs.
SUMMARY
[0008] Described below are a device and a method for using the
device for "in situ" extraction of bitumen or ultraheavy oil from
oil sand deposits which reduce the insulation complexity and any
costs associated therewith. In this case, reliable insulation of
the terminals with respect to the environment should also be
provided at high electrical heating powers.
[0009] A device for the "in situ" extraction of bitumen or
ultraheavy oil from oil sand deposits has at least one electrical
conductor loop, which has a forward conductor and a return
conductor and an inductor connected therebetween. The inductor is
arranged at least partially or completely in the oil sand deposit.
The forward conductor and the return conductor can also act as
inductor or produce the inductor identically, wherein the conductor
loop in the latter case is formed from a continuous conductor. In
the text which follows, for reasons of simplicity, a forward
conductor and a return conductor and an inductor connected
therebetween are described even when the forward conductor and the
return conductor act as inductor or produce the inductor
identically. A forward conductor and a return conductor and an
inductor connected therebetween should thus correspondingly also be
understood to mean a forward conductor and a return conductor which
act as inductor or produce the inductor identically. Furthermore,
the device includes an AC generator, which is electrically
connected to the at least one conductor loop via at least two
electrical contact points. The AC generator in this case includes a
transformer having at least one primary winding and at least one
secondary winding. The at least one secondary winding has a center
tap, to which a ground potential UE has been applied
electrically.
[0010] By virtue of the application of the ground potential UE or
grounding of the center tap, the maximum electrical output voltage
which is present across the conductor loop between the contact
points is limited to half the maximum output voltage, for example.
This results in a considerably lower requirement in terms of
insulation for the contact points with respect to the ground in the
environment for preventing flashovers or arcs effectively and
reliably. The lower insulation requirement is also associated with
lower costs. The voltage is thus effectively prevented from
drifting freely at the contact points with respect to the
environment or the ground.
[0011] The ground potential UE can have been applied passively
electrically via a galvanic connection to the center tap, which
results in a simple and inexpensive solution to the problem.
Alternatively, the ground potential UE can have been applied
actively to the center tap using circuitry via an electrical
circuit. As a result, control or regulation using circuitry
corresponding to the method requirements is possible.
[0012] As an alternative or in addition to the center tap at the at
least one secondary winding, to which a ground potential UE has
been applied electrically, a device for the "in situ" extraction of
bitumen or ultraheavy oil from oil sand deposits having the
above-described features has a ground potential UE, applied
electrically at the conductor loop at a point spatially removed
from the AC generator, with or without a center tap. The advantages
are similar to the advantages associated with a ground potential UE
at a center tap on the at least one secondary winding, as have been
described previously.
[0013] The ground potential UE can have been applied spatially in a
region on the conductor loop, in particular on the inductor, which
is furthest removed from the AC generator. In general, the furthest
removed point is in the region of halfway along the length of the
conductor loop. Grounding at this point results in a maximum
possible limitation of the maximum electrical output voltage which
is present across the conductor loop between the contact points.
The insulation requirement for the contact points can thus be
reduced.
[0014] A voltage UH in the region of greater than 10 kV can have
been applied via the inductor for inductively heating the oil sand
deposit. This can result in a heating power in the MW range and is
therefore sufficient for heating the ground such that bitumen or
ultraheavy oil becomes free-flowing. The transformer can be in the
form of a matching transformer for transforming an output voltage
UA into a voltage in the region of the voltage UH.
[0015] The inductor can have a length of greater than 1 km, in
particular of greater than 5 km. Thus, sufficient ground can be
heated by the inductor in order to ensure usual oil extraction from
oil sand deposits.
[0016] With the exception of a point on the AC generator and/or a
point on the conductor loop spatially removed from the AC generator
at which the ground potential UE can have been applied in each
case, the electrical conductor loop can be electrically insulated
completely from the oil sand deposit. In particular the ground
potential UE can have been applied in such a way that heating of
the oil sand deposit via the electrical conductor loop takes place
purely inductively or at least substantially purely inductively.
The at least one primary winding can be DC-isolated from the at
least one secondary winding. The primary winding can be
electrically connected to power converters. The AC generator can be
in the form of an HF generator with an electrical power in the
range of from 1 to several MW at 5 to 200 kHz, in particular 50
kHz. This arrangement and these values enable optimum heating of
the oil sand deposit for extraction of bitumen or ultraheavy
oil.
[0017] A method using the above-described device involves
application of the ground potential UE at a point on the secondary
winding and/or at a point on the conductor loop spatially removed
from the AC generator, wherein the voltage between the contact
points is reduced to a value which is lower than the value of an
output voltage without the ground potential UE applied. The voltage
between the contact points can be reduced to a value which is
substantially half the value of an output voltage without the
ground potential UE applied.
[0018] The advantages associated with the method for using a device
as described above for the "in situ" extraction of bitumen or
ultraheavy oil from oil sand deposits are similar to the advantages
which were previously described in relation to the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other aspects and advantages will become more
apparent and more readily appreciated from the following
description of the exemplary embodiments, but without any
restrictions being imposed thereby, taken in conjunction with the
accompanying drawings of which:
[0020] FIG. 1 is a perspective view of an oil sand reservoir 1 with
an electrical conductor loop 2 running in the reservoir 1, and
[0021] FIG. 2 is a circuit diagram of an embodiment of a device for
the "in situ" extraction of bitumen or ultraheavy oil from oil sand
deposits 1 corresponding to that shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Reference will now be made in detail to the preferred
embodiments, examples of which are illustrated in the accompanying
drawings, wherein like reference numerals refer to like elements
throughout.
[0023] FIG. 1 illustrates an oil sand deposit referred to as a
reservoir, wherein a right-parallelepipedal unit 1 with the length
l, the width w and the height h is always described for further
considerations. The length l can be up to a few 500 m, the width w
from 60 to 100 m and the height h approximately 20 to 100 m, for
example. It is necessary to consider that, starting from the
Earth's surface E, a "platform" with a thickness s of up to 500 m
can be provided.
[0024] When implementing the SAGD method, an injection pipe for
steam or water/steam mixture and a conveying pipe for the liquefied
bitumen or oil are provided in the oil sand reservoir 1 of the
deposit in a known manner, and in a manner which is not illustrated
for reasons of simplicity, as is known from the related art, for
example DE 102007040605 B3.
[0025] The arrangement or device illustrated in FIG. 1, which
includes, inter alia, a conductor loop 2 which is arranged
partially or completely in the reservoir 1, is provided for
inductively heating the reservoir 1. This can take place in
addition to or as an alternative to known heating with steam, for
example. The conductor loop 2 laid in the ground, which conductor
loop can have a length of from a few hundred meters up to several
kilometers, for example, includes a forward conductor 10 and a
return conductor 20 and an inductor 15. The forward conductor 10
and the return conductor 20 are routed next to one another, in
particular into the ground and out of the ground, and the inductor
15 is connected electrically between the forward conductor and
return conductor 10, 20. In general, the inductor 15 has a
substantially U-shaped conductor, which is routed horizontally in
the ground, wherein both parts of the U shape are routed at the
same depth or lie one above the other.
[0026] The inductor 15 can be formed continuously from one
conductor or be formed from two conductors, which are connected to
one another at the U-shaped end via an element within or outside of
the reservoir 1. Conductor in this context is always understood to
mean electrical conductor below. The conductors 10 and 20 are
routed vertically at the start or down into the ground at a flat
angle. Typical distances between the forward conductor and the
return conductor 10, 20 and/or between the two parts of the
inductor 15 are 5 to 60 m given an outer diameter of the conductors
of 10 to 50 cm. The conductors 10, 15 and 20 can also be formed
from a continuous conductor or from conductor parts. Instead of a
forward conductor and a return conductor 10, 20, the inductor 15
can also perform the task of the conductors or be routed into the
ground corresponding to the profile of the conductors and replace
the conductors.
[0027] An HF generator 30, which can be accommodated in an external
housing, is electrically connected to the conductor loop 2 via
connection terminals, for example, and supplies electrical power to
the conductor loop. FIG. 1 does not show the connection terminals
since they are located in the housing with the HF generator 30.
[0028] An electrical double line, as is known, for example, from DE
102007040605 B3, can be used as conductors 10, 20 and 15. A double
line having the abovementioned typical dimensions has a
longitudinal inductance per unit length of 1.0 to 2.7 .mu.H/m. The
transverse capacitance per unit length given the mentioned
dimensions is only 10 to 100 .mu.F/m, with the result that the
capacitive quadrature currents can initially not be taken into
consideration. In this case, wave effects should be avoided. A wave
speed of an electrical wave is determined by the capacitance and
inductance per unit length of the conductor arrangement.
[0029] The characteristic frequency of the arrangement is
determined by the loop length and the wave propagation speed along
the arrangement of the double line 10, 15, 20. The loop length
should therefore be selected to be so short that no disruptive wave
effects result here. The power loss density distribution in a plane
perpendicular to the conductors, as is formed in the case of
energization of the upper and lower conductors in phase opposition,
decreases radially.
[0030] For an inductively introduced heating power of 1 kW per
meter of double line, a current amplitude of approximately 350 A
for low-resistance reservoirs with resistivities of 30 .OMEGA.m and
approximately 950 A for high-resistance reservoirs with
resistivities of 500 .OMEGA.m is required at 50 kHz. The required
current amplitude for 1 kW/m is inversely proportional to the
square of the excitation frequency, i.e. at 100 kHz, the current
amplitudes decrease to 1/4 of the above values. Given an average
current amplitude of 500 A at 50 kHz and a typical inductance per
unit length of 2 .mu.H/m, the inductive voltage drop is
approximately 300 V/m.
[0031] With the abovementioned total lengths of the double
conductors 10, 15, 20, the total inductive voltage drop would add
up to values of >100 kV. Such high voltages need to be avoided
in order to reduce the risk of flashover in particular between the
connection terminals and in order not to require large insulation
layer thicknesses. The connection terminals need to be insulated
from the reservoir 1 in respect of high voltages in order to
suppress a resistive current flow. Thick insulation layers result
in a high consumption of materials and high costs.
[0032] A solution to the problem can be provided by grounding a
point on the conductor loop 2 in a region 15 or by grounding a
center tap 70 of a secondary winding SE of a transformer 50 of the
power generator 30. The latter is possible as a result of the
circuit illustrated schematically in FIG. 2. The conductor loop 2
is formed by the forward and return conductors 10, 20 and the
inductor 15. The forward and return conductors 10, 20 can also act
as inductor 15 or the inductor identically, wherein the conductor
loop 2 in the latter case is formed from a continuous conductor.
The conductor loop 2 is connected electrically to a transformer 50
via connection terminals 40, 40'. The transformer 50 can match an
output voltage UA to a voltage UH at a frequency which is optimum
for the inductive heating with the conductor loop 2. As has already
been described above, this is dependent on dimensions such as
length, cross section or design of the lines or double lines 10,
15, 20 and frequency, for example.
[0033] The transformer 50 is formed from a primary coil PR and a
secondary coil SE, for example. The primary coil PR is supplied
electrical power from a current/voltage supply 60 with an output
voltage UA. The output voltage UA is converted into a voltage UH
for heating the inductor 15 by the transformer 50, wherein voltage
losses on the forward and return lines 10, 20 have not been taken
into consideration for reasons of simplicity. These voltage losses
would, when added to the voltage UH, result in the voltage to be
obtained or transformed at the secondary coil SE.
[0034] The device includes a center tap 70 on the secondary coil
SE. A ground potential UE has been applied electrically to the
center tap 70, i.e. the center tap is grounded. Without the center
tap 70 and with complete insulation of the conductors 10, 20, 30,
the total voltage UH would be present at the connection terminals
40, 40', which voltage can be in the region of greater than 10 kV
at the maximum in relation to the ground potential UE and would
drift freely. As a result of a grounded center tap 70, the
potential difference between the inductor 15 or the forward
conductor 10 and return conductor 20 and the surrounding ground is
safely limited to half the voltage UH between the connection
terminals 40, 40'. Without fixing the potential at the center tap
70 or at the opposite end of the conductor loop 2, the potential of
the conductor loop could drift freely and thus assume higher
voltages at a branch on the forward conductor side or return
conductor side than half the voltage UH with respect to the
surrounding ground, which could result in flashovers or arcs.
Depending on the arrangement of the center tap 70 on the secondary
coil SE, voltage values differing from half the voltage can also be
achieved at the connection terminals 40, 40'. This is dependent on
the secondary coil SE being split into two parts by the center tap
70. A maximum possible reduction in the voltage present at the
connection terminals 40, 40' is, however, half the value of the
voltage UH which is obtained when the secondary coil SE is split
into two identical parts by the center tap 70.
[0035] An alternative possibility for reducing the maximum voltage
present at the connection terminals 40, 40' with respect to the
surrounding environment is not illustrated in the figures for
reasons of simplicity. Instead of or in addition to a center tap
70, as is illustrated in FIG. 2, the inductor 15 and/or the forward
or return line 10, 20 can have a point at which a ground potential
UE has been applied or which is grounded. This can take place by
virtue of the insulation being interrupted at the point on a
conductor 10, 15, 20 which is otherwise electrically insulated
completely from the ground. A maximum reduction in the maximum
voltage UH present at the connection terminals 40, 40' takes place
in a similar manner to in the exemplary embodiment of the center
tap 70 when the ground potential or the voltage UE is applied at a
point which is spatially removed from the connection terminals 40,
40' to a maximum extent. In the case of an inductor 15 with a U
shape, as is illustrated, for example, in FIG. 1, with two
identical parts of the inductor being connected to one another by a
U-shaped end, grounding of the point 15 with the U-shaped end
results in the maximum reduction in the potential which is
maximally present at the connection terminals 40, 40'. In general,
grounding expediently takes place only at one of two possible
points on the conductor loop 2, at the center tap 70 of the
secondary winding or at the opposite point on the conductor loop 2
itself. If other points, such as, for example, points on the
forward conductor 10 or return conductor 20, are brought or set to
ground potential, the maximum possible reduction in the voltage
between the inductor 15 and the ground to half the value of the
maximum voltage UH present at the connection terminals 40, 40'
cannot be achieved.
[0036] Both in the exemplary embodiment illustrated in FIG. 2 with
the grounded center tap 70 and in the last-described exemplary
embodiment with a grounded point on the inductor 15 and/or the
forward or return conductors 10, 20, grounding can take place
passively or actively. Passively in this context means that
grounding takes place via an electrical line or a direct electrical
contact with the surrounding environment. Actively in this context
means that grounding or application of the potential UE takes place
via a regulated or controlled electrical circuit.
[0037] A description has been provided with particular reference to
exemplary embodiments. Thus, combinations of the exemplary
embodiments with one another and/or with exemplary embodiments from
the related art are also possible, inter alia. It will be
understood that variations and modifications can be effected within
the spirit and scope of the claims which may include the phrase "at
least one of A, B and C" as an alternative expression that means
one or more of A, B and C may be used, contrary to the holding in
Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir.
2004). For example, it is possible for grounding at more than one
point to be favorable, instead of grounding at one point, depending
on the design and use of the device, in particular in the case of
active grounding. Grounding of one of the two contact points 40,
40' can also take place. As a result, although the full potential
UH is present at the second contact point 40 or 40', a reduction in
the complexity in terms of insulation is possible owing to the fact
that only the second contact point 40 or 40' is insulated
* * * * *