Note: Descriptions are shown in the official language in which they were submitted.
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WELLBORE LOGGING SYSTEM
The invention relates to a logging system for use in
a borehole formed in an earth formation.
Generally, in the practice of wellbore drilling each
further section of a wellbore is drilled after the
previously drilled wellbore sections are cased with
wellbore casing. After completing drilling of the further
section, a logging tool is lowered by wireline through
the previously installed casing and into the newly
drilled section so as to conduct a measurement of a
downhole parameter. An example of such logging tool is a
formation pressure test/sampling tool for measuring the
pressure or composition of fluid present in the earth
formation. Such tool is provided with a conduit which is
pushed into the borehole wall a short distance so as to
create fluid communication between the earth formation
fluid and a fluid chamber of the tool.
A drawback of such wireline logging method is the
required additional drilling rig time during lowering and
operating the logging tool. A further drawback is that
there is a danger that the logging tool gets blocked in
the open wellbore section. Moreover, it may not be
possible to insert the logging tool into a significant
part of the newly drilled wellbore section, for example
in case of a highly inclined or horizontal borehole
sections. As a consequence valuable information on the
surrounding formation cannot be obtained.
It is an object of the invention to provide an
improved logging system which overcomes the drawbacks of
the conventional system.
In accordance with the invention there is provided a
logging system for use in a borehole formed in an earth
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formation, comprising a tubular element to be installed
in the borehole, and a logging member including a conduit
having an inlet opening and being movable in radial
direction of the tubular element between a retracted
position in which the logging member is substantially
arranged within the tubular element and an extended
position in which the logging member extends beyond the
tubular element so that said inlet opening is in fluid
communication with the earth formation when the tubular
element is installed in the borehole, the logging system
further comprising an activating device for moving the
logging member between the retracted position and the
extended position thereof, wherein the tubular element forms one
of a wellbore casing, a wellbore liner and a drill string.
It is thereby achieved that that valuable drilling
rig time is saved since the tubular element forms an
integral part of the logging system and is to be lowered
into the borehole anyway. Thus there is no need to
separately lower a logging tool into the borehole by
wireline during periods between lowering/installing the
tubular element and drilling the further wellbore
section. Also, lowering of the tubular element into
highly inclined or horizontal welibore sections can be
done more easily than lowering of a wireline into such
sections. A further advantage of the logging system
according to the invention is that by moving the logging
member to its retracted position the tubular element can
be lowered into the borehole without being hampered by
the logging system and without the risk of damage to the
logging member. Further, by moving the logging member to
its extended position after the tubular element is
installed in the borehole, a characteristic of the earth
formation fluid (e.g. pressure or composition) can be
determined in a logging run.
Suitably the activating device is removably arranged
within the 'tubular element. Thus, after lowering of the
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tubular element Lzto the borehole and determination of
the fluid characteristic, the activating device can be
removed from the :ubular element and retrieved to surface
so that the interior of the tubular element is free from
obstacles in order to allow passage of wellbore tools or
selected fluids through the tubular element.
Preferably the tubular element is one of a wellbore
casing, a wellbore liner and a drill string.
The invention will be further described in more
detail and by way of example with reference to the
accompanying drawings in which
Fig. 1 schematically shows an embodiment of the
logging system of the invention in a first mode of
operation thereof; and
Fig. 2 schematically shows the embodiment of Fig. 1
in a second mode of operation thereof.
Referring to Figs. 1 and 2 there is shown a wellbore
casing 1 arranged in a borehole 2 formed in an earth
formation 4, which casing 1 has not yet been cemented in
the borehole 2 but is suspended from a drilling rig (not
show) at surface. The casing 1 includes an upper casing
section 6, an intermediate casing section 8 connected to
the upper casing section 1 by connector 9, and a lower
casing section 10 connected to the intermediate casing
section by connector 11. The intermediate casing
section 8 is provided with an opening 12 in which a
primary pad 14 and a telescoping member 16 are arranged.
The pad 14 is of cylindrical shape and has an outer
surface 14a facing the borehole wall and an inner surface
14b facing the interior of the casing section 8. At least
an end part of the primary pad at the side of the outer
surface 14a is made of elastomeric material.
The telescoping member 16 connects the primary pad 14
to the casing section 8, and is arranged to perform a
telescoping movement in radial direction (of the
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casing 1) so as to move the primary pad 14 between a
retracted position wherein the primary pad 14 is located
substantially within the outer radius of the casing
section 8 and an extended position wherein the primary
pad 14 extends beyond the outer radius of casing
section 8 and the outer surface 14a contacts the wall of
the borehole 2. Furthermore, the telescoping member 16
seals the primary pad 14 relative to the casing
section 18.
The primary pad 14 is provided with a bore 18
extending in radial direction of the casing section 8, in
which a conduit 22 is arranged in a manner allowing the
conduit 22 to slide through the bore 18 a selected
stroke. The conduit 22 has at its inner end a shoulder 24
which, when in contact with the inner surface 14a,
prevents further outward sliding of the conduit 22. A
compression spring 25, arranged between the shoulder 24
and the inner surface 14b of the primary pad 14, biases
the conduit 22 to a radially inward position thereof. The
conduit 22 is internally provided with a ball valve 26
including a ball 28 biased against a valve seat 30 by a
spring 32. The ball valve 26 prevents flow of fluid from
the exterior of the casing section 8 to the interior
thereof when the ball 28 is biased against the valve
seat 30.
The primary pad 14 is biased to its retracted
position by a leaf spring 29 extending along the outer
surface of the casing section 8 and being connected at
opposite ends thereof to the casing section 8. The leaf
spring 8 is provided with an opening (not shown) for
passage of the conduit 22 therethrough as the conduit 22
slides outwardly through the bore 18.
An activating device 34 is removably arranged within
the casing section 8 and latched to the casing wall by a
latching assembly (not shown). The activating device 34
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includes a secondary pad 36 of cylindrical shape and made
of elastomeric material, which secondary pad 36 is
arranged concentrically relative to the primary pad 14
and a jack 38 arranged to bias the secondary pad 36
5 against the primary pad 14 so as to move the primary
pad 14 between the retracted position thereof and the
extended position thereof. The activating device 34
furthermore includes a support member 40 for supporting
the jack 38 against the inner surface of the casing
section 8, an electric motor 42 for operating the
jack 38, a fluid chamber 44 provided with a fluid
pressure gauge (not shown), an electronic control/memory
unit (not shown) for controlling the electric motor 42
and the pressure gauge and for storing pressure readings
of the pressure gauge, and a battery (not shown) for
powering the control/memory unit and the electric
motor 42. The secondary pad 36 is provided with a tube 46
extending concentrically through the secondary pad 36 and
arranged to bias the ball 28 away from the valve seat 30
and to provide fluid communication between the conduit 22
and the fluid chamber 44 when the secondary pad is biased
against the primary pad 14.
The primary pad 14, the secondary pad 36, and the
conduit 22 are dimensioned such that, upon movement of
the secondary pad 36 against the primary pad 14, the
secondary pad 36 pushes against the conduit 22 which
thereby slides in radially outward direction through the
bore 18 and the opening of the leaf spring 29 until the
shoulder 24 contacts the inner surface 14b of the primary
pad 14.
Normal operation of the assembly referred to in
Figs. 1 and 2 is hereinafter described, whereby Fig. 1
shows the primary pad 14 in the retracted position and
Fig. 2 shows the primary pad in the extended position.
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During normal operation the activating device 34 is
latched into the casing section 8 by means of the
latching assembly, and the casing sections 6 and 10 are
connected to casing section 8 by the respective
connectors 9, 11. Then the casing 1, with the primary
pad 14 in the retracted position, is lowered into the
borehole 2. Lowering is stopped when the primary pad 14
arrives at a selected depth in the borehole where it is
desired to conduct a pressure measurement of earth
formation fluid such as oil or water. A wireless control
system (not shown) at surface is then operated so as to
induce the control/memory unit to operate the electric
motor 42 so that the motor 42 induces the jack 38 to bias
the secondary pad 36 against the primary pad 14. The
primary pad 14 thereby moves from the retracted position
to the extended position in which the outer surface 14a
of the primary pad 14 is biased against the borehole wall
(Fig. 2). Simultaneously the secondary pad 36 pushes
against the conduit 22 so that the latter protrudes
through the opening of the leaf spring 29 and extends a
short distance into the borehole wall, and the tube 46
biases the ball 28 away from the valve seat 30 and
thereby provides fluid communication between the
conduit 22 and the fluid chamber 44. As a result the
fluid chamber 44 communicates with fluid present in the
earth formation. The control/memory unit then operates
the fluid pressure gauge so as to measure the pressure of
the formation fluid and to store the resulting pressure
data in the electronic memory.
The electric motor 42 is then induced to retract the
jack 34 so as to move the secondary pad 36 radially
inward. As a result the primary pad 14 also moves
radially inward due to the biasing force from the leaf
spring 29. The primary pad 14 and secondary pad 36 remain
in contact until the primary pad 14 reaches its retracted
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position. Further radially inward movement of the
secondary pad 36 causes secondary pad 36 to become
displaced from the primary pad 14, and the tube 46 to
become displaced from the ball 28 so that the spring 18
biases the ball 28 against the valve seat 30 thereby
closing the ball valve 26.
If further earth formation fluid pressure
measurements at different borehole depths are desired,
the casing 1 is raised or lowered through the borehole 2
so as to relocate the primary pad 14 in the borehole 1 at
the desired depths. The procedure as described
hereinbefore is then repeated.
After completing the desired pressure measurements, a
suitable retrieving device (not shown) is lowered through
the casing 1 to the activating device 34 in order to
unlatch the activating device 34 from the casing
section 8 and to retrieve the activating device 34 to
surface. The pressure data is then read out from the
electronic memory at surface.
If no further earth formation fluid pressure
measurements are to be conducted the casing 1 is cemented
in the borehole 1. In case the borehole 2 is to be
further drilled, the latching assembly is drilled out of
the casing 1 before commencement of further drilling.
Instead of reading the pressure data from the
electronic memory after retrieval of the activating
device 34 to surface, the pressure can alternatively be
read by extending a data transfer line (e.g. an electric
conductor) from surface to the activating device 34 and
transferring the data in the form of electric signals
through the data transfer line to surface while the
activating device 34 is still latched to the casing 1.
