Note: Descriptions are shown in the official language in which they were submitted.
METHOD AND APPARATUS FOR DATA TRANSMISSION
IN A WELL USING A FLEXIBLE LINE WITH STIFFENER
1 Field of the Invention
This invention relates to methods and apparatus for
communicating data from the bottom to the top of a well.
Background of he Invention
Oil and gas wells are known having a well bore for
passing fluid, transversely across a side of the well bore at
a down hole location of the well bore and longitudinally in
the will bore, between a geological formation located at the
down hole location and a top portion of the well bore. The
pressure of the fluid flowing across the side of the well is
an important parameter to know by operators at the top of the
well. Other parameters of the fluid as it flows across the
side of the well may also be important to know at the top of
the we'll. For example, during fracturing, when fluid is
passed into the geological formation, pressure at the down
hole location is important in determining whether a fracture
is vertical or horizontal and to determine growth parameters
of the fracture. Fluid pressure and temperature at the down
hole location of a producing well, where fluid is flowing from
the geological formation to the top of the well, may also be
important in some situations. However, remoteness of the down
hole location from the top of the well, high flow rates of the
fracture fluid across the side of the well and the harsh
environment down hole create difficulties in reliably
recovering data representing the pressure and other parameters
from the fluid at the down hole location..
Therefore, a need exists for easy to use apparatus and
methods for recovery, at the top of a well borer data which
accurately and reliably represents a parameter, particularly
pressure, of a fluid and particularly a fracture fluid, as
; what parameter exists in the fluid flowing through the side of
the well at the down hole location.
S _ cry of the Invention
Briefly, method and apparatus is disclosed herein or
recovery of data in an oil or gas well having a well bore for
1 passing fluid, transversely across a side of the well bore at
a down hole location of the well bore and longitudinally in
the well bore, to a neological formation located at the down
hole location from a top portion ox the well bore
An embodiment ox the present invention is a method for
recovering data up hole at the top of a well bore while
passing fracturing fluid down hole to a geological formation
through a zone, hazing up hole and down hole extremities, in
the well bore. Briefly the steps are as follows:
A parameter sensor and a transmitter of data signals
are positioned at a location in the we'll bore which is
substantially down hole from the zones down hole extremity.
the data signals represent a parameter sensed by the sensor.
A flexible line, preferably a wire line is lowered in the well
that has, suspended therefrom, a receiver which is separate
from the sensor and transmitter and a stiffener positioned up
hole from the down hole extremity of the receiver with at
least one insulated conductor passed up to the top of thy well
bore through the stiffener and the line. The step of lowering
zoo also includes the step ox lowering the line until the receiver
is in proximity to the transmitter and at least a portion of
the stiffener extends substantially from the up hole extremity
to the down hole extremity in front of the zone.
Preferably, the step of lowering includes the step of
attaching to a lower end of the line, as the stiffener, a
substantially rigid cylindrical member and then lowering the
line and the cylindrical member and the receiver. By using a
plurality of the cylindrical members attached end to end, the
stiffener can be made large enough to span very large or
lengthy zones through which the fracturing fluid flows. The
receiver is, preferably attached to a free lower end of one
of the cylindrical members. In one arrangement the receiver
senses potentials applied in the fracturing Plaid. In another
arrangement the receiver senses magnetic signclls.
Preferably/ the parameter represented by the data signals
1 is pressure.
One embodiment has the sensor and transmitter mounted
together in a single module and the module is dropped down the
inside of tubing string or down the casing due to the pull of
gravity ox assisted with fluid pressure.
A number of advantages can be achieved by the present
invention By way of example, the flexible line can be
lowered 50 that the receiver is down immediately adjacent to
or near by the transmitter, and as a result, the distance over
I which signals must be transmitted is minimized. Thus, where
the transmitter and receiver are at the bottom of the well
bore below the zone through which the fracturing fluid is
passed, the stiffeners provide a substantially rigid member in
front of the zone preventing the insulated conductor from
being sucked into or whipped into the openings formed in the
zone.
It is possible to position the receiver after the casing
is set. It is unnecessary to reattach the receiver to casing
or the live.
Additionally, where the casing has become weak because of
deterioration or because of the depth of the well bore r it is
possible to run tubing down the center of the casino, lower
the flexible line, receiver and stiffener in the annuls
between the tubing and casing and pass the fracturing fluid
down the tubing. As a result the flow of the fluid is not in
direct contact with the flexible line until it gets clove to
the zone through which the fracturing fluid is passed thereby
minimizing the downward pull and wear on the flexible line.
With arrangements where there is a tubing string inside
of a casing, it is desirable to make the tubing string as
large in diameter as possible, relative to the inside of the
casing causing the annuls spacing to be quite small, leaving
very little room for passing parts on a flexible line or
otherwise down the well. Since a receiver can be made quit
3 small, by mounting only the receiver and stiffener on the line
it
1 it is possible to pass or feed the line down the annuls.
Minimizing the obstruction to the line in the annuls by
minimizing the parts hung on the line as it is passed down the
annuls is, therefore, very important. The parts which are
larger in a transverse direction, such as the transmitter,
sensor and the battery for the transmitter and receiver, are
separated from the receiver and line and are lowered to the
desired position. This can be done either by mounting them on
a tubing string and lowered, or they can be dropped (i.e.,
"air mailed") down the hole in a common module. If the
transmitter, sensor and battery are air mailed, this can be
done down the inside of the tubing string or down the casing
prior to insertion of the tubing.
I
l Brief Description of the Drawings_
In the drawings:
FIG. l is a schematic of an oil or gas well
showing tubular casing and cement in cross-section
within a well bore to reveal a receiver and a stiffener
suspended from a wire line which extends to the top
of the well bore and a sensor and transmitter and
embodies the present invention;
FIG. 2 is a schematic and partial cross-sectional
lo view similar to FIG. 1 with tubing creating an annuls
for the wire line down to the fracture zone and
embodies the present inverltion;
FIG. 3 is a schematic, cross-sectional and
exploded view of a wire line, a stiffener, a cable
head or making the stiffener up to the wire line and
an exposed electrode-type receiver for receiving the
data signals from the transmitter;
FIG. is a schematic and block diagram in cross
section of a sensor and transmitter mounted in a
common module inside of casing,
FIG. 5 is a cross-sectional view of a wire line,
a cable head, a stiffener and dipole type exposed
electrode receiver (having two vertically displaced
electrodes) for use in JIGS. l and 2;
FIX. 6 is a schematic diagram of a dipole
type exposed electrode receiver having two horizontally
displaced electrodes for use in FIGS. 1 and 2;
EGO. 7 is a cross-sectional view of the receiver
of FIG. 6 taken along the lines 7-7;
FIG. 8 is a schematic diagram of a vertical
dipole exposed electrode receiver;
:
1 EGO. 3 is a schematic and block diagram of a jell
bore containing a sensor and transmitter mounted
on a tube and a vertical dipole receiver;
FIG. I is a schematic diagram of an alternate
receiver which receives electromagnetic fields;
FIG. 11 is a schematic and cross-sectional
view of a preferred receiver for receiving electromagnetic
fields;
FIG. 12 is a schematic and side elevation view
of the upper portion of a cable head, such as that
depicted at the left in FIG. 3 including a spring
tapered upper end err making the transition between
the wire line and the cable head,
FIG. 13 is a schematic diagram of a sensor,
transmitter, receiver and processing display and
storage for use in the system of FIGS. 1 and 2;
FIG. I is a schematic and block diagram depicting
the sensor and details of a transmitter for forming
digitally encoded frequency modulated carrier signals
:: 20 representing the parameter;
FIG. 15 provides a schematic and block diagram
depicting the details of the processing display and
storage for frequency modulated carrier signals
received by the receiver of FIG. 13;
FIG. 16 is a schematic and block diagram depicting
an alternate arrangement of the sensor and transmitter
in which analog signals from the sensor are converted
to frequency modulated signals for sending to the
receiver;
FIG. 17 depicts a receiver and processing,
display and storage apparatus for use with the data
signals provided by FIG. 16;
I
Jo -
1 FIG. 18 is a detailed schematic diagram of the
sensor and transmitter for forming electromagnetic fields
for use in FIG. 13; and
FIG. 19 is a schematic and block diagram similar
to FIG. 18 modified to produce a stronger signal in
the annuls.
1 Detailed Desert lion of the Preferred Embodiments
FIG. 1 is a schematic and partial cross-sectional view of
an oil or gas well 20 and illustrates a method and means for
obtaining from down hole, data signals which represent a
parameter, preferably pressure, in a well bore 25.
The well has a tubular casing 24 cemented by means of
cement 46 into on the inside of well bore aye. A transmitter
28 and a sensor 30 contained in a module 31 are located at the
bottom of the well bore or on a plug in the well located below
one or more perforations I through which fracture fluid 60 is
passed to an adjacent formation 44.
The perforations I are, by way of example, holes or a
cutout through the casing made, as well known in the well
drilling art, which extend throughout a zone in the well bore
indicated at 29 having as a zone upper extremity aye and a
zone lower extremity 29b.
A flexible wire line has, suspended therefrom, a receiver
which is separate from the sensor and transmitter. The wire
line also has a stiffener 32 which is positioned up hole from
thy down hole extremity aye of a receiver 34. An insulated
conductor, shown and disclosed in more detail with reference
to FIG. 3 passes up to the top of the well bore through the
stiffener and the wire line. The stiffener extends completely
across the zone 29 in front of the perforations 48. As a
result, the receiver 34 can be placed down adjacent to or very
close to the transmitter below the fracture zone without
having the flexible wire line, or the insulated conductor,
exposed in front of the zone 29 where fast flowing fracture
fluid passing through the perforations 48 would tend to draw
them into the perforations and damage or destroy these flexible
I
elements
Although stiffener 32 is shown as a separate
element from the receiver 34, it should be understood
that the stiffener may actually encompass a portion
of the receiver.
The well extends into the earth 42 to a geologic
stratum or formation I from which oil or other
hydrocarbons are to be produced. The invention is
especially well suited for wells that may extend
anywhere prom 5,000 to 20,000 feet or more below the
surface. Though the apparatus and method, according
to the present invention can be used in shallower
wells, it is especially well suited for deeper wells.
A basin or tank 52 holds the fracturing fluid
54. Fluid 54, under the pressure developed in pump 58,
is supplied through a supply line 56, through the
central passage of casing I and through the perorations
48 to the formation.
The fracturing fluid is applied under pressure
at a high flow rate to the formation for creating,
opening up or enlarging a fracture on the formation.
on operation, the sensor 30 and transmitter 28
are located in the well bore at the bottom at a
position which is adjacent to or substantially down hole
from the zone 29 up hole extremity aye. The sensor is
preferably for sensing bottom hole pressure and the
transmitter provides data signals to the receiver
which represent the pressure parameter sensed by the
sensor.
A flexible wire line is lowered in the well bore
while having suspended therefrom the receiver, which
is separate from the sensor and transmitter. Additionally,
the wire line has suspended therefrom the stiffener
I
1 which is positioned up hole from the down hole
extremity of the receiver. An insulated conductor
(to be described) passes up to the top of the well
Gore through the stiffener and the wire line. The
wire line is lowered until the receiver is in proximity
to the transmitter and the stiffener extends
substantially prom the zone up hole extremity to the
zone down hole extremity in front of the zone as
depicted in FIG. 1. Preferably the stiffener extends
completely across the zone 29 slightly beyond the
up hole and down hole extremities. The stiffener is
more rigid than the wire line and is sufficiently rigid
that it is not drawn into the perforations.
The pump is then started causing the fracturing
fluid to start flowing down through the central
passage of the casing 24 past the stiffener 32 through
the perforations of the zone 29 into the adjacent
formation for fracturing as discusses above.
Electronics in the sensor in the transmitter,
and, to the extent present, in the receiver are
active during the process of fracturing. For example,
a start timer may be included in the transmitter
which times out and activates the electronics.
Alternatively, the electronics operations may be
initiated before the tubing and packer are lowered in
place O
As the fracturing fluid is forced through the
perforations 48 and into the surrounding region the
flow is impeded by the earth formation so that pressure
is developed in the area of the perforations. The
pressure is sensed by sensor I which produces
signals for transmitter 28 which are a function of
; the pressure. The signals are manipulated or processed
:
I
1 as desired and data signals representing the pressure
are passed by transmitter I to and are received by
the receiver 34. Data signals representing the
pressure are then conducted along wire line 3G to
the processing display and storage apparatus 38 for
analysis, and display and/or storage.
The wire line is wound on a reel 63 at the top
of the well. The receiver is made up on thinned of
the wire line and then the reel is rotated to unwind
the wire line and lower the receiver and stiffener
down the well bore or disconnected above. Preferably
the lowering of the receiver is done after the transmitter
is lowered into place.
FIG. 2 is a schematic and cross-sectional view
essentially the same as FIG. 1 except that tubing 26
is shown for passing the fracturing fluid down the
well bore to a position adjacent to or slightly above
the upper extremity aye of the zone 29. With this
arrangement it will be necessary to plug or cap the
top of the annuls between the tubing and casing
to prevent the fluid from passing along the
outside of the tubing and out of the top ox the well
as is conventional in the well drilling art. The use
of the tubing has two desirable effects. First the
flowing fracture fluid is not in contact with the
wire line I until close to the down hole location of
the zone and, therefore, very little downward drag is
applied to the wire line. Also, the use ox the tubing
protects casing that has deteriorated or become weak
from the flowing fracture fluid.
The wire line includes a central insulated
conductor which extends to the top of the well bore.
The data signals representing the pressure parameter
I
1 transmitted by transmitter 28 are received by receiver
34 and data signals representing the parameter are
conducted up to the top of the well bore over the
insulated conductor contained in the wire line. The
wire line may be constructed in a number of different
ways, but must be of suitable strength to support the
receiver and stiffener and withstand the harsh environment
in the well bore, and must be long enough to position
the receiver as close as possible to the transmitter.
The wire line may be an insulated coaxial cable.
However, preferably the wire line is similar to that
conventionally used in the oil tool art, and has a
central insulated conductor, insulation surrounding
the central conductor and an outer metal sheath which
protects the wire line from the abrasive effects
of the fluid and other materials in the well with
which it comes in contact when in or moving down the
annuls of the well. The wire line, including the
central conductor, the insulation and outer sheath
extend to the top of the well, and are wound on the
reel 63. Preferably the conductor is stranded.
It Lo typical in the well drilling art to make
up the tubing string out of a number of separate
pipes or annular members threaded end to end. The
tubular string is lowered into the well by adding
pipes one at a time to the uppermost end of the
tubing string, lowering the tubing string with the
connected packer into the well.
It will be understood by those skilled in this
art that procedures need to be followed to prevent
Jo the inlet to the sensor from plugging up with particles
from the fluid. This may be accomplished by making
the sensor opening large enough that the particles
I
I
1 do not wedge in the opening or by positioning the
pressure sensing surface flush with the opening to
the sensor. Preferably the outer diameter of the
jacket on the wire line and the electrode are each
substantially 1/2 inch. An optimum and preferred
length for the electrode is between 3 and I feet.
The longer the electrode the better the contact
between the conductive fluid and the electrode and
hence the higher the signal to noise ratio of the
received signal at the top of the well. However, the
shorter the electrode the easier it will be to lower
the electrode on the end of the wire down to the
desired position in a narrow annuls.
FIG. 3 is a cross-sectional view of a receiver
made up on a wire line where the receiver is of the
type for receiving potentials from the conductive
fluid in the annuls. A wire line 100 has an electrode
type receiver 102 suspended from the end of the wire
line. The receiver 102 shown is for use with a
conductive fracturing fluid 60, and is adapted for
receiving electrical potentials or data signals,
representing the sensed parameter, which are created
in the conductive fluid.
The receiver is comprised of an electrically
conductive, elongated and cylindrical shaped metallic
conductor or electrode 103. The electrode is preferably
copper plated steel and is exposed so that it will be
in electrical contact with the surrounding conductive
fluid. The electrode is suspended from the down hole
end of the stiffener.
The wire line has an outer sheath 104, a
central insulated conductor 106 and an annular insulator
103 separating the conductor 106 from the conductive
I
1 sheath 104. The conductor 106 is connected to a
spring contact or banana plug l:L0 by means of a
terminal nut 109 having a circular bore into which
the exposed end of the conductor 106 is inserted and
crimped. The opposite end of the terminal nut 1~9
has a bore into which an end of contact rod 112 is
threaded. The opposite end of the rod 112 has a
threaded bore into which the rear end of banana plug
110 is threaded. The nut and electrically connected
rod and plug, all being electrically conductive
materials, provide continuous electrical path between
the insulated conductor 106 and the plug 110. The
conductive outer sheath 104 of the wire line is
electrically connected in a babbit-type stinger 114
which in turn is threaded into one end of an electrically
conductive sleeve 116. The opposite end of the
sleeve 116 is threaded over the end of an electrically
conductive contact sub 118, which in turn is electrically
isolated from the rod 112 by an insulating sleeve 120
from plug 110 by an insulating washer 122.
Electrode 102 has its upper externally threaded
end which is threaded into a sleeve-shaped coupler
124. An insulating sleeve 126 on the electrode 102
electrically insulates the electrode 102 from tile
coupler 124. The upper end of the electrode 102
contains a bore 123 into which an electrical plug of
the stiffener is inserted.
The stiffener 32 is depicted in JIG. 3 as a
series of cylindrical shaped stiffeners each identified
by the number 202. Each stiffener is identical and
I; all are connected end to end between the end 123 of
the cable head and the up hole end ox the electrode
102. Two stiffeners 202 are shown for illustration
US
16
1 but more can be employed as required.
Each stiffener 202 includes an upper threaded
connector or receptacle 204. The upper Yost stiffener
202 is threaded on end 123 of the cable head. An
electrical receptacle or connector 206 receives the
plug 110 of the cable head forming an electrical
connection to a rod or conductor 208 which in turn is
connected by means of a threaded connector 216 to a
spring contact 214 at the lower end of the stiffener.
The stiffener 202 has a rigid tubular shaped outer
sleeve 210 which provides a rigid support for the
conductor 208 preventing it from being drawn into the
perforations during fracturing. An insulator sleeve
211 separates the conductor 208 from the outer sleeve
21~. The down hole end of each stiffener 202 includes
Jo a threaded plug 21~ which is either threaded into the
threaded receptacle 204 of the next lower stiffener
or receptacle 127 in the coupler 124 for the electrode
102. The insulating sleeve 126 insulates the coupler
124 and, therefore, the outer sleeve 210 of the
stiffeners, the outer sleeve of the cable head and,
thwarter, the outer sheath 104 of the cable from the
electrode 102.
With this arrangement, a rigid structure is
formed actually starting with the upper end of the
electrode 102 extending along the series of stiffeners
- which can 'be positioned in front of the zone 29
without being drawn into the perforations during the
high flow rates of the fluid during fracturing.
FIG. 4 depicts the arrangement of FIGS. 1 and 2
I; where the sensor and transmitter are dropped or "air
mailed" down the central passage of the casing or
tubing string and to the bottom of the well bore.
FIG. 4 depicts in cross section the casing 24, cement
I
17
l 46, and conductive fluid I The transmitter is
generally depicted at 90 and is in a single modular
construction together with the sensor. More specifically,
the module includes an elongated, preferably about 2
S foot long, segment of tubing 92 containing therein
pressure sensor 94, battery 96, voltage Jo frequency
convertor I and an elongated coil 91. Preferably
coil 91 is mounted on a tubular shaped ferrite core
93 and together are mounted on the outside of and
lo coaxial with tubing 92. The windings of the coil 91
are wound longitudinally along the tubular core 93
and set up a longitudinally extending flow of current
in tubing 92 as depicted at "i". The current induced
in the tubing 92 flows longitudinally along the wall
aye of the tubing 92 into surrounding conductive
fracturing fluid 60 to the receiver 34 causing a
potential to be induced on the electrode of receiver
34 relative to a reference.
Plugs 95 and 97, preferably made of electrically
conductive material, are inserted in the opposite ends
of the tubing 92 for sealing the inside of the tubing
(and hence the sensor, the battery and the electronics)
from the surrounding fluid. The sensor 94 has a
passage aye tapped through the plug 95 for sensing
US pressure external to the module. The coil 91 is
insulated from the core and from the tubing 92 by
insulation (not shown). Because of the alternating
current frequency generated by the coil 91 circulating
eddy currents may be set up in the tubing 92 as well
as the longitudinal currents. However, the frequency
of the signal is preferably sufficiently low that the
eddy currents can be made small.
I
I
1 In some applications it will be desirable to
insulate the length of the tubing 92 while using
electrically conductive plugs exposed in the ends of
the tube, thereby causing the longitudinally extending
induced currents to flow out of the plugs into the
conductive fluid. This would minimize linkage current
from the sides of the tubing 92.
ERGS. 6 and 7 depict an alternate horizontal dipole
type receiver for receiving potentials which has a
pair of horizontally displaced exposed electrodes 132
and 134 connected by leads 138 and 139 to insulated
conductors 142 and 144, respectfully on or in a wire line
140. The insulated conductors 142 and 144 and the
wire line 140 extend to the top of the well. If a
shielded wire line is used as in JIG. 3 one of conductors
142 and 144 may ye connected to the shield and the
other to the central conductor. The exposed electrodes
132 and 134 are recessed into or otherwise mounted on
the bottom and partially up the side of a cylindrical
rod 136 made of an insulating material. The signal
created in the conductive fluid causes a potential
difference between the horizontally spaced electrodes
132 and 134, which can be sensed at the top of the
well between the conductors 142 and 144.
FIG. 8 depicts an alternate vertical dipole type
receiver 150 which has vertically displaced electrodes
152 and 153 electrically connected, respectfully, to
insulated conductors 15~ and 156 in a wire line
indicated at 157 which in turn extends to the top of
the well similar to wire line 140 of ERG. 7. Electrodes
152 and 153 are ring shaped, recessed and mounted
Cole with and around the periphery of cylindrical
rod 158, which is made of an insulating material.
19
1 The vertically displaced electrodes 152 and 153 and
the horizontally displaced electrodes 132 and 134 of
FIG. 7 are spaced sufficiently jar apart to receive a
potential difference on the spaced electrodes of a
sufficient magnitude to be detected. The electrodes
in both FIGS. 7 and 9 are recessed to protect the
electrodes from physical contact with the tubing
casing, fluids or other material as the receiver is
passed down through the annuls and also to prevent a
direct short between the electrodes due to the intervening
conductive fluid. The larger the spacing between the
electrodes the larger the signal will become between
the electrodes.
YIP. 9 depicts a vertical dipole electrode 150
similar to that depicted in FIG. 8 adjacent a
transmitter I and sensor 30. The transmitter 28'
has spaced apart electrodes 159 and 160 mounted on an
insulated cylinder 156. Electronic unit 161 applies
electrical potentials between electrodes 159 and 160
representative of the bottom hole pressure sensed by
pressure sensor 30.
FIG. 5 shows a vertical dipole receiver in
combination with the wire line 100, the cable head,
and a stiffener 32 composed of stiffeners 202, all,
I except for the dipole receiver, being the same as
described with reference to FIG. 3. The dipole
receiver forms part of the stiffener and is depicted
at 170 and includes a tubular member 172 whose upper
end is threaded onto the lower end of the lower
stiffener 202. A top receptacle 174 receives and
forms an electrical contact with the contact 214 (see
FIG. 3) of the adjacent stiffener 202. A contact rod
17~ electrically connects the receptacle 174 to the
I
1 threaded rear end of a spring contact or banana plug
178, in a similar manner to the connection of plug
110 to rod 112. The upper electrode of the dipole is
formed by the electrically conductive outer surface
of the sleeve 210 (see FIG. 3) on the stiffener 202
which is adjacent and above the member 172. The
lower electrode is formed by an electrically conductive
plug 180 which has a cylindrical outer surface exposed
for electrical contact with the surrounding conductive
fluid. The outer surfaces of both the sleeve 210 of
stiffener 202 and the plug I are copper plated to
enhance conductivity. The plug 180 is threaded into
the lower end 1~2 of sleeve 172. A non-conductive
sleeve 184 on plug 180 electrically isolates the plug
180 from the sleeve 172. The sleeve 172 is electrically
insulated by insulators from the contact 174, rod 176
and plug 178 as generally indicated in EGO. S. If
needed, the sleeve 172 may either be made of a non-conductive
material or of a conductive material, but with a
non-conductive epoxy coating covering the outside, so
as to electrically insulate the same from the conductive
fluid
JIG. 10 depicts an alternate arrangement in
which the receiver is of a solenoid-type which receives
magnetic fields or signals produced by the transmitter.
The receiver 240 is in the form of a coil spirally
wound around a cylindrical ferrite core 244. The
ends of the coil 242 are connected between the central
conductor and the conducting metal sheath on a wire
line 246 above, which extends to the top of the well.
Preferably the receiver is housed in a non-magnetic
housing (not shown) the diameter of the antenna is
preferably approximately the same as or smaller than
the diameter of the wire line 246.
1 FIG. 11 depicts a preferred construction for
the inductive type or solenoid type receiver for
mounting at the down hole end of the stiffener such as
stiffener 202 as depicted in FIG. 3. The receiver
coil assembly is depicted at 260 and includes a coil
262, wound about a core 263. The coil has leads or
ends 264 and 266 which are connected, respectfully,
to an electrically conductive receptacle 268 and a
contact rod 270. The receptacle 268 is constructed
for receiving and electrically forming a connection
with the plug 214 of stiffener 202. The opposite end
of the rod 270 from the lead 266 is electrically
connected to another receptacle 272. The assembly
also includes an outer electrically conductive sleeve
; 15 274, having upper threaded end 276 into which threads
on the lower end 218 of the stiffener 202 are inserted.
The sleeve 274 also has a lower threaded end 278 into
which a plug 280 is threaded. The plug 280 has a
spring-type plug 282 which is inserted into and forms
electrical contact with the receptacle 272. The plug 280
is an electrically conductive material which electrically
connects the receptacle 272 and hence the rod 270 and
lead 266 of the coil 262 to the outer electrically
conductive sleeve 274, which in turn is electrically
connected through the conductive outer sleeve of the
stiffener 202 to the electrically conductive sub, and
therefore to the electrically conductive outer sheath
of the wire line 200. The other end 26~ of the coil
262 is electrically connected through the receptacle
268 to the plug 210 and hence to the conductor
206 of the wire line. As a result the magnetic signals
received by the coil, cause electrical signals to be applied
between the ends 264 and 266 of the coil, which in
I
1 turn may be sensed a the top of the well between the
center conductor and outer sheath of the wire line.
FIG. 12 depicts the upper end of the sleeve 116 of
the cable head made up to the wire line 100. A
coiled conical shaped spring 290 is wound around the
sleeve, the babbit-type stinger 114 see FIG. 3) and
along a short distance of the wire line 100. This
structure is important in that it allows the flowing
fracture fluid to pass from the transition between
the wire line 100 and the cable head along a rather
smooth gradual transition as opposed to an abrupt
change which would be present without the conical
spring.
Additionally, the conical spring 290 absorbs the
side motion of the stiffener and protects the wire
line as it bends preventing it from wearing and
breaking at the up hole end of the babbit-type stinger.
Refer now to FIG. 13 which depicts a schematic
diagram of over all systems involved in detecting,
29 providing and sending data signals representing a
parameter front down hole to the top of the well bore.
Sensor 350 senses the parameter, preferably pressure,
and provides a data signal to transmitter 352. The
transmitter 352 includes electronics 356 and a signal
sender for sending signals into the annuls between
the tubing string and the casing. The signal sender
is generally referred to herein for ease of reference
as transmitting antenna 358 and includes either apparatus
for inducing potentials in the conductive fluid in
the annuls or the solenoid type antenna which generates
electromagnetic f folds into the annuls. Also included is a
battery 354 for providing power to the electronics
356 and if necessary to the sensor 35~. To be explained
23
1 in more detail the electronics 356 may take on a
number of configurations, however, it is arranged for
receiving data signals from the sensor 35~ representing
the sensed parameter and for producing data signals
which can be sent by the transmitting antenna 358
to and received by a receiver. The sensor 350,
transmitter 352 and power supply 354 are always
located down hole. A receiver, also referred to for
convenience, as a receiving antenna 360, receives the
data signals representative of the parameter which
has been sent into the annuls by the transmitting
antenna 358. In one embodiment a wire line 362 (with
one or multiple conductors), conduct data signals
representative of the parameter (represented by the
received data signals) up hole to receiving electronics,
display and storage apparatus I (see FIG. 1).
Apparatus 38 includes amplifier 364 which amplifies
the data signals from the wire line and receiving
electronics 367, which processes the amplified
sugarless into a form suitable for display and/or
storage by means not shown in FIG. 13.
To be explained in the more detail the amplifier 364
may be divided up into two amplifier sections, a pro-
amplifier section down hole at the lower end of the
wire line near the receiving antenna 360 and an
: amplifier section up hole. The preamplifier section
: preamplifes the signals before they are conducted
by the wire line up hole to the rest of the amplifier
: section. If the signal is preamplifier before conduction
up the wire line, the wire line must be a coaxial
conductor, by way of example as shown in FIG. 3.
: Also, power can be provided over the wire line trot
the top of the wire line without adding additional
24
1 conductors thus avoiding the need for batteries or
other sources of power down at the receiver. It
should also be noted that the amplifier will have two
inputs indicated at 366 and 368. The input 366 may
be connected to the insulated conductor in the wire
line whereas the other input 368 may be connected to
a shield (if present) or other conductor in or on the
wire line, the upper end of the casing 24 at the top
of the well or to one or more ground electrodes positioned
in the ground around the well, depending on the configuration
and design of the system. Where the receiving antenna
receives potentials, the shield or other conductor
of the wire line, the upper end of the casing or the
ground electrodes connected to the second input 368
I become a source of reference potentials or a reverence
with respect to which the signals at input 366 are
detected. In the arrangement where the receiving
antenna 360 is a magnetic pick-up, picking up magnetic
signals, the inputs 366 and 368 will be effectively
connected across the ends of the coil forming a part
of the magnetic pick-up in the receiving antenna.
With the foregoing in mind it will be appreciated
that if all sections of the amplifier 364 are contained
at the top of the well, then the receiving antenna
and everything at the bottom of the wire line will be
passive and thus will minimize the amount of the
electronics, the power required down hole and the
outer size of the equipment lowered on the end of the
wire line. If on the other hand portions of the
amplifier or other electronics are located down hole
at the lower end of the wire line, then the equipment
at the receiving antenna is not passive and may
require additional and larger equipment then with a
1 passive arrangement.
FIX 14 shows a specific example of the electronics
356. Specifically the sensor provides an analog
output whose amplitude is proportional to sensed
pressure. Analog to digital convertor 370 converts
the analog signal to digital coded signals for a
micro-processor 372. The micro-processor 372 converts
the digital signals into a serial and redundantly
encoded bit string. The frequency modulation and
amplifier unit 37~ then transmits the serial bit
string via transmitting antenna 358 into the
annuls using a signal of one frequency to represent
a binary 0 and a signal of a second frequency to
represent a binary 1. The data signal is then sent
by the transmitting antenna 358 into the annuls.
It should be understood that the frequency
modulator 374 may be replaced by other suitable means
for forming signals that may be sent out into the annuls
by antenna 358, such as circuits which produce amplitude
modulated signals, phase modulated signals or other
suitable signals for transmission by transmitting
antenna 358.
The analog~to-digital convertor 370 may comprise
any one of a number of convertors well known in the
art as may processor 372. Preferably the processor
is a COOS circuit and encodes the signals provided
to frequency modulator 374 to a form which allows error
correction. Preferably the microprocessor 372 provides
digital signals to the frequency modular 374 at the
I rate of 1 binary bit per second. A suitable carrier
frequency is preferably as low as 10 to 20 hertz and
as high as 10 kilohertz or higher.
26
1 FIG. 15 depicts a specific embodiment of the receiving
portion of FIG. 13 including the receiving antenna
360 and the receiving electronics, display and storage
apparatus 38. Apparatus 38 includes amplifier 364,
electronics 367, and a display and storage unit 386.
The system of FIX. 15 is for receiving data signals
represented by the frequency modulated signals produced
by the system of JIG. 14. Specifically, receiving
antenna 360 receives the frequency modulated data signals
from the antenna 358 of JIG. 14. With a passive system
the signals are conducted directly from the antenna
360 up the wire line 362 to amplifier 36~ where the data
signals are amplified. The demodulator 380 converts
the amplified data signals from frequency modulated
signals to digital signals representative of the parameter.
Pulse-shaper 382 shapes the signals into a proper
Jo form for reading by micro-processor 384. Micro-processor
384 processes the digital signals into the proper
form for display such as on a digital visual display
and for storage such as on magnetic tape, disk or the
like.
The system of FIG. 15 just discussed is passive,
that is, none of the amplifier or other electronics,
are located at the bottom of the wire line.
In another arrangement the amplifier 364 and
demodulator 380 are located down hole at the receiving
antenna as depicted to the left of dash line 390 and
the pulse-shaper, microprocessor in display and
storage are located up hole as indicated to the right
of dash line 390. With this latter arrangement, wire
line 362 would be replaced by a suitable electrical
connector to amplifier 364 and the wire line would be
positioned at 362' between the demodulator and the
27-
1 pulse-shaper. With this arrangement the signals will
be of higher amplitude and therefore easier to detect
at the top of the hole than if no amplifying is
provided down hole.
FIG. 16 depicts a specific embodiment of the
sensor electronics and transmitting antenna 358 shown
to the left in FIG. 13 where the pressure parameter
data signals are encoded in analog form. The analog output
data signals prom the sensor 350 representing the pressure
parameter are processed by the analog processing unit
400 and converted to a frequency modulated signal,
the frequency of which represents the analog signal
and hence parameter The frequency modulated signal
is then amplified by amplifier ~02 and then sent to
the transmitting antenna 358 for sending data signals
into the annuls for pick-up by the receiving antenna.
The analog processing unit 4~0, by way of example
operates on an analog signal from 0 - 5 volts and
converts these signals to a frequency from 10 -
several thousand hertz, the actual frequency being
proportional to the actual voltage level of the
analog signal. Preferably the analog processing unit
400 alternates between the frequency representing the
actual analog signal and a signal representing the
full scale analog output for calibration purposes at
the top of the well.
FIG. 17 depicts the receiving antenna 360 and
the receiving electronics and display and storage
apparatus 38 for use with the data signals formed by
the transmitter of FIG. 16. Specifically, the data
signals sent by antenna 358 ox FIG. 16 are received
by receiving antenna 360, signals corresponding
thereto representing the sensed parameter are conducted
28
1 up the wire line 362 to amplifier 364 which amplifies
the signals and provides them to demodulator ~10.
Demodulator 410 converts the frequency modulated signals
back to analog voltage signals in the range of between
0 - 5 volts, the magnitude of which represents the
value of the parameter. Analog to digital
convertor 412 converts the analog signals to digital
form for the micro-processor 414. The micro-processor
414 does signal processing to remove errors from the
signal and to convert the digital signals to a Norm
which can be displayed and stored by display and
storage unit 3~6 in the manner discussed above.
With the arrangement just discussed, the down
hole portion of the system at the receiving antenna
360 is passive. To this end the dash line 413
indicates that everything to the let is down hole
whereas everything to the right is up hole. It may
be desirable in some applications to locate the
amplifier and demodulator down hole at the
receiving antenna 360, in which case the portion to
the left of dash line 418 will be down hole and the
portion to the right will be up hole and the wire
line will be at 362" between the demodulator
and the analog to digital convertor.
The digital system depicted in FIGS. 14 and 15
are potentially more accurate than the analog versions
of FIGS. 16 and 17 J since in the digital version
error correcting encoding methods can be used to
correct for the effects of noise in the transmission
link,
The analog version depicted in FIGS. 16 and 17
has an advantage in that less down hole electronics are
generally required in order to conduct the signals to
29
1 the top of the well, making it easier to design for
high temperatures. Additionally, less power is
required down hole.
FIG. 18 depicts a specific example of the sensor,
electronics and transmitting antenna of FIG. 13 which
produces magnetic fields and electrical potentials in
the annuls. Although the circuit of FIG. 18 worms
electrical potentials in the conductive fluid for the
electrode receiver, it is preferably used to form
magnetic signals for inductive type receivers where
there is a close spacing between the transmitting antenna
and the receiver.
Sensor 35U' includes a balanced bridge circuit
395 having a conventional four terminal bridge with
resistors aye, 395b, 395c, and 395d, each connected
between a different pair of terminals. Terminal
397 is connected to the ground conductor for power
supply 354. Terminal 399 is connected through resistor
462 to the + V side of power supply 354. Variable
pressure sensitive resistor aye is connected between
the terminals 396 and 399, the resistance ox resistor
; aye varies as a function of pressure sensed by the
sensor.
Electronics 356' preferably includes an integrated
circuit chip 450 of the type AD 537 manufactured by
Analog Devices of Nerd, Massachusetts, which converts the
analog signals from the pressure sensor to a frequency
modulated carrier signal for application to the receiving
antenna 358'. The chip 450 includes a voltage to
frequency convertor 458, operational amplifier 454,
and NUN transistor 456, a transistor driver 466, NUN
transistor 468 and a source ox reverence voltage 460.
The terminal 398 between resistors 395c and d of the
:
~39~
l bridge is coupled to the + input of amplifier 454.
The terminal 396 between resistors aye and b of the
bridge is coupled through resistor 452 to the - input
of amplifier 454. The output of amplifier 454 is
connected to the base electrode of transistor 456.
The emitter electrode of transistor 456 is coupled to
the junction between resistor 452 and the - input of
amplifier 454. The collector electrode of transistor
456 is corrected to the control input of voltage to
frequency convertor 458. Voltage to frequency
convertor 458 provides a signal through driver circuit
466 to transistor 468 which signal has a frequency
that is proportional to the current supplied through
the collector of transistor 456~ Power supply 354
applies an output of approximately + 6 volts potential
at the V output. Resistor 462 is selected to cause
a voltage of approximately + l volts to occur at
terminal 399 ox the bridge. The internal reference
generated at the output to convertor 458 by V reference
460 will be proportional to the signal at terminal 399.
Preferably the resistor 462 is approximately 175U
OHMS with a pressure sensing resistor Sue value of
approximately 450 OHMS. As a result a small amount
of current is drawn from the voltage reference at
terminal 399.
The output, at which the resultant frequency
signals are formed by the convertor 458, is coupled
through driver circuit 466 to the base electrode of
transistor 46~. The transistor 46~ operates in a
switching mode. The emitter electrode of transistor
468 is connected to ground, whereas collector electrode,
of the transistor is connected by conductor 4~5
through a current limiting resistor 472 to one side
of the coil in the transmitting antenna 35~'. The
I
1 opposite side of the coil of the transmitting antenna
358' is connected to the + V OUtpllt of the power
supply 354. As a result the frequency modulated
signals formed by the convertor ~58 cause the transistor
468 to form signals in the coil of the transmitting
antenna 358' causing it to form electromagnetic
fields, which are picked up by the corresponding
receiving antenna.
Diode 474 is connected in parallel with resistor
472 and the coil of transmitting antenna 358 and
limits voltage at the collector of transistor 468 as
well as provides a discharge path for current in coil
of antenna 358' when transistor 468 is switched off.
Resistor 472 is a current limiting resistor in both
the charge and discharge cycles and also sets the
resistance inductance time constant. The power
supply 354 is preferably three high temperature
lithium battery cells with unregulated voltage, but
the voltage must be greater than 5 volts DC. With
; 20 this arrangement the sensor electronics and transmitting antenna can be run directly from a battery type power
supply 354 and the chip is relatively insensitive to
supply voltage variations.
The circuit of FIG. 19 is essentially the same
as FIG. 18 except that it is modified to provide
greater amplification to the signals being sent by the
transmitting antenna and hence greater output power
so that the signals can be transmitted over a larger
separation between the transmitting antenna and the
receiving antenna. In this regard a MISFIT transistor 488
or amplifier, is provided with its control electrode
connected to output conductor 485 and its output
electrodes connected between the + V output of battery
~'3'3~
1 354 and the junction between diode 474 and resistor
472. The junction of diode 474 and the coil of the
transmitting antenna 358' are connected to the ground
conductor for the power supply 354. In addition, a
pull up resistor 489 is connected between the control
electrode of transistor 488 and the V output of the
battery 354.
Where there is a closely spaced relation between
the transmitter and receiver, the transmitter may
transmit and the receiver may receive optical signals
or acoustic signals.
Although a wire line having one or more conductors
for passing the data signals to the top ox the well
bore is the preferred form of the flexible line, it
will be understood by those skilled in the art that a
flexible line with fiber optic conductors may be used
with appropriate means for conversion of the received
data signals to optical form.
Also, it spacing between transmitter and receiver
is sufficiently close, applications may be encountered
where the optic or sonic wave signals may be transmitted
by the transmitter and received by the receiver.
It should be noted that the above are preferred
configurations, but others are foreseeable. The
described embodiments of the invention are only
considered to be preferred and illustrative of the
inventive concepts. The scope of the invention is
not to be restricted to such embodiments. Various
and numerous other arrangements may be devised by one
skilled in the art without departing from the spirit
and scope of the invention.
