Note: Descriptions are shown in the official language in which they were submitted.
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DOWNHOLE INSTRUMENT AND METHODS
OF M~NUFACTURING AND USING THE SAME
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This invention pertains generally to bore hole drilling and
surveying, and more particularly to a downhole instrument and
methods of manufacturing and using the same.
In the drilling of oil ~ells and other bore holes in the earth,
it is at times necessary to determine -the location of the
drill or the precise location of the hole at a substantial
distance below the surface of the earth. For this purpose,
a surveying probe is inserted into the hole, and data from
the probe is analyzed at the surface to determine the location
of the probe. It is also desirable to determine the direction
in which the drill is progressing and to control this direction.
In the downhole surveying equipment heretofore provided, the
probe generally comprises an elongated, rigid body with an
inflexible metal shell. Probes of this type are incapable
of traveling around bends of relatively short radius (e.g.,
a 6 - 12 inch radius in a hole having a diameter on the order
of 3/4 - 1 inch), and therefore, they cannot be used in some
holes.
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Tools have also been provided for cutting and severing
tubing, drill pipe and casing in a bore hole. Such tools generally
have one or more remotely detonated explosive charges mounted in an
elongated, rigid housing. Tools of this type are subject to the
same limitations and disadvantages as the surveying and logging
instruments heretofore provided in that they cannot travel around
bends of relatively short radius and are not suitable for use in
some holes.
It is in general an object of the invention to provide a
new and improved downhole instrument and methods of manufacturing
and using the same.
Another object of the invention is to provide an instru-
ment and method of the above character which can also be utilized
in the guidance of a downhole drill.
Another object of the invention is to provide an instru-
ment and method of the above character which can be utilized in
the cutting or severing of tubing, drill pipe and casing.
Another object of the invention is to provide an instru-
ment and method of the above character which are suitable for use in
holes having bends of relatively short radius.
Another object of the invention is to provide an instru-
ment of the above character which is economical to manufacture.
Accordingly, the present invention provides in a package
for carrying a payload in a bore hole in the earth: an axially
elongated casing of flexible material having a high tensile strength,
an elongated mass of flexible, cushioning material surrounding the
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payload and filling the casing to form a flexible body which can
be propelled through the bore hole in piston-like fashion by pres-
surized fluid and can travel around bends of relatively short radius
in the bore hole, and a flexible cable extending axially from one
end of the body and secured to the casing of flexible material for
carrying signals between the payload and the surface of the earth.
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The probe may include one or more sensors, explosive
charges or the like, as the payload.
The present invention further provides in a method of
transporting a payload into a hole having a limited diameter and
at least one bend of relatively small radius, the steps of: pack-
aging the payload in an elongated, flexible body having a mass of
cushioning material therein, introducing the body into the hole,
passing the body along the hole and around the bend, the body
flexing freely as the instrument passes around the bend, and
advancing the body along the hole until the payload is in a desired
position. The probe may be driven into a bore hole in piston-like
fashion by a pressurized fluid such as water or air.
Instrumentation for processing signals from the probe is
located at the surface of the earth, and a flexible cable inter-
connects the instrumentation with the probe.
In drawings which illustrate exemplary embodiments of
the invention,
Figure 1 is a schematic diagram of one embodiment of a
bore hole surveying system incorporating the invention, with the
flexible probe being inserted into a bore hole and passing around
a bend.
Figure 2 is a block diagram of the surveying system of
Figure 1.
Figure 3 is an enlarged sectional view, partly broken
away, of the flexible probe of the embodiment of Figure 1.
As illustrated in Figure 1, the surveying system includes
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an elongated, flexible probe 11 which is inserted into a hole 12
to be surveyed. The hole can be a bore hole in the earth, as
illustrated, or any other elongated opening of limited diameter
such as the opening in a pipe or tubing. The probe has a generally
circular cross section, with an outer diameter slightly smaller
than the inner diameter of the hole, e.g., for a hole diameter on
the order of 3/4 - l inch, the probe would have a diam~ter on the
order of .70 - .95 inch. The length of
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the probe is substantially greater than the diameter, and
a pro~e having a diameter of .70 inch could, for example,
have a length on the order of 48 inches.
A flexi~le logging cable 16 extends in an axial direction
from one end of the probe and carries electrical power
and signals between the probe and equipment at tne
surface of the earth. This cable is of conventional
design and has a plurality of flexible electrical
conductors interleaved with a plurality of reinforcing
strands of suitable material such as stainless steel.
The cable is stored on a cable reel 18 at the surface
of the earth, and the amount of cable fed into the hole
is monitored by a cable length indicator 19 connected
to the reel.
At the surface of the earth, the probe is interfaced
with a microcomputer 21 by a suitable interface unit 22.
The computer processes the signals from the probe and
the cable depth indicator to determine the location
and/or orientation of the hole in the region ~here the
pro~e is located~
As illustrated in Figure 2, probe 11 includes a payload
such as three orientation sensors 23-25 which provide
electrical signals corresponding to the orientations of
the sensors relative to orthogonal reference axes. In
this embodiment, the reference axis of sensor 2~ is
aligned with the axis of the probe, and the axes of
sensors 24, 25 are aligned in perpendicular radial
directio~s. Sensors 23-25 can be any suitable sensors
of known design, including fluxgate compasses and other
magnetometers. As used herein, the term magnetometer
includes any instrument capable of detecting natural or
artificial flux lines, two common types of maynetometers being H~l
effect devices and flux gate transformer systems. Other suitable
sensors include gyroscopes and other inertial devices. Sensors 23-
25 are connected to cable 16 through an electrical power and signal
conditioning module 26 in the probe. The probe also includes an
inclinometer 27 which provides a signal corresponding to the
orientation of the probe about a pitch axis. If desired, addition-
al inclinometers can be included to provide additional information
such as the dip angle of the tool. Suitable inclinometers include
accelerometers, electrolytic levels, and pendulous devices. Elect-
rical connections between the cable, the power and signal condi-
tioning module and the elements within the probe are made by a
connector 28 of suitable known design.
As illustrated in Figure 3, sensors 23-25, module 26,
inclinometer 27 and connector 28 are spaced apart along the axis of
probe 11 and are innerconnected by flexible electrical conductors
31. Alternatively, the electrical components can be fabricated on
a flexible circuit board, or on a board having a plurality of
relatively short, rigid sections interconnected by one or more
flexible sections. These elements are encased within an elongated,
flexible casing 32 of high tensile strength. The casing is closed
and secured to a stainless steel nose piece 33 by a clamp 34 at the
distal end of the probe, and at the proximal end the casing is
affixed by a clamp 35 to connector 28 and thus to logging cable 16.
In one presently preferred embodiment, casing 32 comprises
a fabric woven or braided of fibers having a high tensile, strength,
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i.e. a tensile strength greater than that of stainless steel,
preferably 250,000 lb/in2 or more. One presently preferred
fabric is an aromatic
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polyamide fiber manufactured by DuPont under the trade-
mark Kevlar. This fiber has a tensile strength on the
order of 400,000 lbjin2. Other suitable fibers of high
tensile strength can also be employed, including graphite
fibers, glass fibers, nylon fibers and boron fibers.
The interior of casing 32 is filled with a mass of
flexible, electrically insulative material 36 which
surrounds the sensors and other electrical components
and provides cushioning for them. This maLerial and
the outer casing form a flexible body which can pass
freely around bends of relatively short radius in the
bore hole. Suitable materials include silicones and
other synthetic rubber materials such as Devcon
(trademark) polyurethane or a silicone rubber sold under
the trademark Silastic. The flexible material can be
either in a solid form or in a fluid form. Suitable
fluid materials include silicones and fluorocarbons of
high dielectric constant and low vapor pressure. The
fluid can be in the form of a gel, and it preferably has
a relatively high viscosity. One particularly suitable
fluid material is a silane polymer known as Dow Corning
- 200 fluid. Alternatively, with a solid cushioning
material, the fabric casing can be omitted, and axially
extending fibers can be embedded in the mass of material
to provide the desired tensile strength, in which case
it is desirable that the fibers be able to move axially
within the mass of material to avoid collapsing of the
body as it is bent.
The outer surface of casing 32 can be coated with a
lubricious material such as polytetrafluoroethylene
(Teflon*) which facilitates the free passage of the probe
through the bore hole. A flexible sealing ring 41 is
affixed to the outer wall of the body toward the proximal
end thereof to facilitate driving the probe through a
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bore hole, as discussed hereinafter. The outer diameter
of the seal is chosen to provide sliding, sealing
engagement with the inner wall of the opening in which
the probe is to be used, and seals of different sizes
and shapes can be mounted interchangeably for casings of
different diameters. The seal can be bypassed with flow
passageways (not shown) to prevent the formation of a
vacuum behind the head of the probe as it is withdrawn
from the hole.
In one presently preferred method of manufacture, the
electrical components of the probe are connected together
and suspended vertically from cable 16 in the desired
spaced apart relationship. Casing 32 is positioned
coaxially of these components, with the open end of the
casing facing in an upward direction. The fluid silicone
rubber material is then poured into the casing to form
tne flexible body. Connector 28 is installed and
connected electrically to the leads in the probe and to
the conductors of cable 16, the open end of the casing
is drawn about the connector, and clamp 35 is installed.
With a solid cushioning material, the material can be
formed about the electrical components in one or more
successi~e layers, with adjacent ones of the layers
being able to move somewhat relative to each other.
The components and cushioning material are then inserted
into the fabric casing as a unit.
In use, probe 11 is inserted into the upper portion of
the hole to be surveyed or drilled, and pressurized
fluid (e.g., water or air~ is applied to the hole above
the probe to drive the probe down through the hole in
piston-like fashion, with seal 41 forming a seal between
the body of the probe and the wall of the casing or
other opening in which the probe is inserted. In the
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event that fluid is trapped in the hole ahead of the
probe, it can be removed by any suitable means, e.g.,
by pumping it out o~ the hole, by withdrawing it from the
hole by the cable, or by driving it into the formation
surrounding the hole. When the probe reaches a bend in
the hole, the body flexes, and the probe passes freely
around the bend. As discussed above, the probe can
travel around bends of relatively short radius, e.g., a
bend having a radius o 6 inches in a hole having a
diameter of 3/4 - 1 inch. The probe is withdrawn from
the hole by drawing on the logging cable.
Because of its relatively small diameter, probe ll is
also suitable for use in the guidance of a downhole
drilling system. In this application, the probe is
mounted in the drill motor housing itself or in a fluid
passageway near the drill head, and cable 16 extends to
the surface through the fluid passageway or another
suitable passageway in the well casing. At the surface,
the signals from the probe are processed and utilized to
control the direction of the drill.
In addition to direction sensors, the payload or
instrumentation within the probe can include other
sensors for other logging functions, e.g., temperature,
pressure, nuclear radiation, hydrogen ion concentration,
and instruments for measuring the characteristics of the
formation being drilled.
The invention is also useful in tools for cutting or
severing drill pipes, tubing and/or casing in a bore
hole. A tool of this type made in accordance with the
invention is similar to the instrument of Figures l and
3, with electrically detonated explosive charges instead
of sensors 23-25. The explosives can be any suitable
explosives of known composition, e.g., pellets or
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plastic explosives, such as C3 or RDX. Electrical
detcnating signals are applied to the explosives ~y
cable 16 and the electrical leads within the probe.
The charges can be arranged to provide any type of
cutting action required, e.g., a concentrated explosion
for severing a drill head from the end of a tube, or a
series of explosions for perforating a line as the
probe passes through it.
It is apparent from the foregoing that a new and
improved downhole probe and methods of manufacturing
and using the same have been provided. While only
certain presently preferred embodiments have been
described in detail, as will be apparent to those
familiar with the art, certain changes and modifications
can be made without departing from the scope of the
invention as defined by the following claims.
