Note: Descriptions are shown in the official language in which they were submitted.
CA 02436069 2003-07-28
BOREHOLE LOGGING APPARATUS FOR DEEP WELL DRILLING WITH A DEVICE
FOR TRANSMITTING BOREHOLE MEASUREMENT DATA
BACKGROUND OF THE INVENTION
This invention relates to a borehole logging apparatus for deep well drilling,
with a
device for transmitting measured data obtained while drilling from a borehole
to the earth's
surface, with an elongated housing, which is adapted for insertion in the
drilling fluid conduit of
a drill string, includes at its influx end an entrance opening leading into a
central housing
conduit and has, downstream from the entrance opening, a sealing ring
effecting a seal
against the drill string, which further includes a bypass opening arranged
downstream from the
sealing ring and leading from the central housing conduit into the drilling
fluid conduit of the
drill string, and, downstream from the bypass opening, has a passageway
connecting the
central housing conduit with the drilling fluid conduit of the drill string,
said passageway being
adapted to be throttled at least in part by a controllable closure element of
a hydromechanical
signal transmitter arranged in the housing, said closure element being
repeatedly movable, at
controlled intervals and in response to signals characteristic of measured
data to be
transmitted, from a passing position into a throttling position and back again
into the passing
position in order to generate in the drilling fluid a coded series of positive
pressure pulses
corresponding to the signals.
In a borehole logging apparatus of the type referred to which is known from US-
2002-
0105858-A1 a flow regulator with a control piston is arranged in the housing.
The flow
regulator controls the cross-section of opening of the bypass opening in
response to the
pressure differential generated by a flow restrictor and the force of a
spring, in such manner
that the part of the drilling fluid current fed to the signal transmitter
through the flow restrictor is
maintained substantially constant, and the remaining excess drilling fluid
current is routed to
the drilling fluid conduit via the bypass opening. The control piston of the
flow regulator has a
throttling section controlling the cross-section of passage of the bypass
opening, and a
measuring section serving as a pressure sensor. The throttling section and the
measuring
section are interconnected by a tappet, and the throttling section disposed in
the housing
conduit disconnects the bypass opening from the signal transmitter and is
penetrated axially
by a throttling conduit forming the flow restrictor. With this configuration
the control action of
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the control piston can be influenced by the operation of the hydromechanical
signal
transmitter.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a borehole logging
apparatus of the
type initially referred to which enables the partial currents fed to the
signal transmitter and the
bypass opening to be adapted to different feed rates and drill string bores
automatically and
which enables the signal transmitter to produce sufficiently strong and
significant pressure
pulses at all feed rates.
It is further an object of the present invention to provide a borehole logging
apparatus
of this type in which the automatic adaptation of the partial currents fed to
the signal
transmitter and to the bypass opening to different feed rates and drill string
bores is not
affected by the operation of the hydromechanical signal transmitter.
According to the present invention the elongated housing accommodates in its
interior
a flow regulator having a control piston, which controls the current of
drilling fluid through the
bypass opening in response to the pressure differential generated at the
entrance opening and
to the force of a spring, in such manner that the drilling fluid current,
which is fed to the signal
transmitter, is maintained at levels optimal for the generation of significant
pressure pulses,
and the remaining excess drilling fluid current is routed to the drilling
fluid conduit via the
bypass opening. Advantageous embodiments are indicated in claims 2 to 5.
In the borehole logging apparatus of the present invention, the control piston
detects
the pressure differential occurring at the entrance opening of the housing due
to throttling. As
a result, the control movements of the signal transmitter and the attendant
flow variations at
the lower end of the housing conduit have no effect on the control action of
the control piston.
The borehole logging apparatus of the present invention is independent of the
delivery rate of
the drill fluid pumps within a wide working range and therefore also suitable
for different drill
string bores. By suitably designing the flow regulator, the drilling fluid
current fed to the signal
transmitter can be automatically adjusted to current values optimal for the
generation of
significant pressure pulses, which values are maintained during operation by
means of a
quantity-dependent regulation of the bypass cross-section. Depending on the
amount of
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CA 02436069 2003-07-28
drilling fluid delivered, the bypass current can be between zero and a value
equal to or even
greater than the drilling fluid current fed to the signal transmitter. By
virtue of the automatic,
pressure-independent adaptation of the bypass current to fluctuating drill
fluid delivery rates,
interruptions of drilling operations, conversion work on the borehole logging
apparatus and
faults resulting from unfavorable bypass cross-sections are avoided.
According to the present invention, provision may furthermore be made for the
measuring section of the control piston to be arranged in a chamber disposed
upstream from .
the entrance opening in the housing, which chamber is divided into two
compartments by the
measuring section, whereof the first compartment, which is located at the end
of the
measuring section remote from the tappet, is connected to the drilling fluid
conduit of the drill
string through a connecting bore, and whereof the second compartment, through
which the
tappet extends, is connected to the end of the housing conduit close to the
signal transmitter
through a longitudinal bore, through which the tappet is passed, and receives
therein a
compression spring bearing against the measuring section with a spring force.
The
configuration of the invention permits integrating the flow regulator into the
slim cylindrical
housing of a borehole logging apparatus using simple, low-cost components
while maintaining
a large cross-section of flow hardly impeding the drilling fluid current. As a
result, the outside
diameter of the borehole Jogging apparatus can be kept so small as to be
suitable for use with
deep drilling standard bores of coupling size 2 7/8" and larger and to be
withdrawable through
the drill string from the derrick. The configuration of the invention
furthermore ensures a
minimum of abrasion because sharp turns in the drilling fluid current are
avoided.
In order to achieve a favorable control characteristic it is possible for the
compression
spring to have a progressive characteristic. Alternatively, it is possible for
the opening cross-
section of the bypass opening to increase degressively as the travel of the
control piston
increases in the opening direction.
According to a further proposal of the invention, provision may be made for
the control
action of the control piston to be considerably dampened. This prevents the
pressure pulses
generated by means of the signal transmitter from setting the control piston
in vibration, which
would incur the risk of the control action and the service life of the flow
regulator being
impaired. Dampening is accomplishable simply by increasing the flow resistance
needing to
be overcome for filling and emptying the first and/or second compartment
bounded by the
measuring section.
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The present invention will be explained in more detail in the following with
reference to
an embodiment illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view of a section of a drill string and a
section of a
borehole logging apparatus of the invention with flow regulator and
hydromechanical signal
transmitter; and
FIG. 2 is a cross-sectional view of the throttling section of the control
piston of the
borehole logging apparatus of FIG. 1.
DETAILED DESCRIPTION
FIG. 1 shows the upper section of a borehole logging apparatus 1 arranged in
the
drilling fluid conduit 2 of a drill collar 3- of a drill string for deep well
drilling. The borehole
logging apparatus 1 comprises a housing 4 composed of several housing parts
bolted together
and having the form of an elongated cylindrical rod. Arranged in the section
of the housing 4
shown are a flow regulator 5 and a hydromechanical signal transmitter 6, while
further units
such as the drive of the signal transmitter 6, a measuring probe, a measuring
transducer, a
signal generator and an energy storage are arranged in the lower section of
the housing 4, not
shown. Provided at the upper end of the housing 4 is a catch hook 7 by which
the borehole
logging apparatus 1 is held by means of a gripper to enable it to be lowered
into the drill string
on a rope or pulled out again.
The illustrated section of the housing 4 has at its upper end a chamber 8 and
a
downwardly adjoining housing conduit 9 separated from the chamber 8 by a wall
10 and re-
ceiving the signal transmitter 6 at its lower end. Beneath the wall 10 the
housing conduit 9 is
in communication with the drilling fluid conduit 2 through entrance openings
11 and above the
signal transmitter 6 through bypass openings 12. The entrance openings 11 have
the effect of
a flow restrictor. Between the entrance openings 11 and the bypass openings 12
the drilling
fluid conduit 2 is interrupted by a constriction 13 formed by the drill collar
3, and the housing 4
is sealed against the constriction 13 by means of a seal 14. The drilling
fluid current conveyed
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through the drilling fluid conduit 2 is therefore forced to enter the housing
conduit 9 through the
entrance openings 11, leaving the conduit beneath the constriction 13 through
the bypass
openings 12 and/or the signal transmitter 6.
The flow regulator 5 comprises a control piston 15 having a throttling section
16 and a
measuring section 17 which are interconnected by a tappet 18. The throttling
section 16 is
arranged in the housing conduit 9 in the area of the bypass openings 12 in
such manner as to
be able to close the bypass openings 12 or open them wholly or in part. The
throttling section
16 is comprised of two concentric sleeves 19, 20 interconnected by two radial
walls 21. The
free annulus between the sleeves 19, 20 produces a conduit 22 through which
fluid flow is
directed to the signal transmitter 6. The measuring section 17 is
longitudinally displaceably
mounted in the chamber 8 and sealed against the chamber wall. It divides the
chamber 8 into
two compartments 23, 24. Several bores 25 extending through the housing 4
provide for
communication between the compartment 23 and the drilling fluid conduit 2. A
bore 26
through which the tappet 18 is passed provides for connection of the
compartment 24 with the
housing conduit 9. Furthermore, the compartment 24 houses a compression spring
27 acting
upon the measuring section 17 with a spring force. The compression spring has
a deflection
characteristic by which the spring force increases progressively when the
spring is
compressed.
The signal transmitter 6 disposed at the lower end of the housing conduit 9
has a
cylindrical, beaker-shaped rotor 28 and a stator sleeve 29 surrounding the
rotor. The stator
sleeve 29 is axially fixed in place in the housing 4 between an annular disk
30 non-rotatably
arranged in the housing 4 and a threaded ring 31, and is maintained in a
defined angular
position in a manner preventing relative rotation by positive engagement of a
claw within a
recess in the annular disk 30. The rotor 28 is of an axial length less than
the stator sleeve 29
and is equally mounted in the space between the annular disk 30 and the
threaded ring 31.
By means of a coupling 32 the rotor 28 is connected with a drive shaft 33 in a
non-rotating
relationship, taking support upon the drive shaft 33 in an axial direction so
it is in a mid-position
between the annular disk 30 and the threaded ring 31. As a result, the axial
end surfaces of
the rotor 28 are not in frictional contact with the opposite neighboring
surfaces. The drive shaft
33 is mounted with zero play in axial direction in the downwardly adjoining
section, not shown,
of the housing 4 by means of rolling thrust bearings. The rotary motion of the
rotor 28 is lim-
CA 02436069 2003-07-28
ited to an angle of rotation of, for example, 45° by claw-type
projections on its bottom, which
engage within recesses in the annular disk 30.
In the wall of the stator sleeve 29 provision is made for a symmetrical
arrangement of
passageways 34, with openings 35 of matching size being provided in the
opposite wall of the
housing 4. The passageways 34 and the openings 35 are separated from one
another in the
circumferential direction by respective closed wall portions. The wall of the
rotor 28 is likewise
provided with passageways 34 which, in the illustrated position of the rotor
28, lie opposite the
passageways 34, the passageways being likewise separated from each other by
closed wall
portion 36. The circumferential dimensions of the passageways 34 and wall
portions 37 are
coordinated so that on a rotation of the rotor 28 through the predetermined
angle of rotation
the wall portions 37 close the passageways 34.
Serving to drive the rotor 28 is a reversible direct-current motor linked to
the drive shaft
33 by means of a reduction gear and a flexible coupling. To generate pressure
pulse signals
the direct-current motor is powered by current of changing direction so that
it periodically
reverses its direction of rotation, moving the rotor 28 alternately into the
illustrated passing
position and into the closing position offset by an angle of 45°, for
example. The respective
end position of the rotor 28 is sensed by an angle-of-rotation transducer for
control of the
direct-current motor.
In operation, drilling fluid is conveyed through the drilling fluid conduit 2
of the drill collar
3 and the housing 4 of the borehole logging apparatus 1 in the manner
illustrated in the Figure
by the arrowed lines, with the drilling fluid current being produced by
drilling fluid pumps
connected to the drill string on the earth's surface. The drilling fluid
current entering the
housing conduit 9 at a pressure P1 is throttled to a pressure P2 < P1 as it
passes the entrance
openings 22. The pressure differential P1 - PZ becomes effective on the
measuring section 17
of the control piston 15 and attempts to displace the control piston 15 in the
direction of the
signal transmitter 6 until the pressure forces and the force of the spring 27
counterbalance
each other. The throttling effect of the entrance openings 11 and the force of
the compression
spring 27 are designed in relation to the hydraulic effective areas of the
control piston 15 so
that the pressure differential P1 - P2 produced by the drilling fluid current
in the presence of a
low delivery rate is not sufficient to overcome the spring force, hence
causing the control
piston 15 to be maintained in its upper stop position and close with its
throttling section 16 the
bypass openings 12 up to a small minimum cross-section. Nearly the entire
drilling fluid
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current is therefore routed through the signs! transmitter 6 in order to
enable it to produce
sufficiently strong and significant pressure pulses. With the delivery rate of
the drilling fluid
current increasing, the pressure differential P1 - P2 increases, too. By
virtue of the higher
pressure differential the control piston 15 is now moved downwardly against
the force of the
compression spring 27, and the bypass openings 12 are opened until the balance
is re-
established. When the delivery rate of the drilling fluid current continues to
increase, the
control piston 15 opens the bypass openings 12 a wider amount, whereby the
amount of by-
pass fluid increases. The amount of drilling fluid routed to the signal
transmitter 6 through the
conduit 22 also increases but the increase is lower and just high enough to
enable the signal
transmitter 6 to produce sufficiently strong and significant pressure pulses.
Hence the flow
regulator 5 is in a position to regulate the amount of bypass fluid between a
minimum value
and a maximum value determined by the maximum opening cross-section of the
bypass
openings 12. In the entire range of control the amount of drilling fluid fed
to the signal
transmitter varies to the extent to which the pressure differential P1 - P2,
which increases to
overcome the progressively increasing force of the compression spring 27,
effects an increase
in the amount of drilling fluid passing through the conduit 22. The variation
in the amount of
drilling fluid fed to the signal transmitter 6 is low in comparison with the
variation in the amount
of bypass fluid. It can be influenced by the design of the spring
characteristic of the
compression spring 27. In this connection a progressive spring characteristic
has proven to be
advantageous for achieving a convenient control characteristic. The same
effect can be
accomplished with a configuration of the bypass openings that tapers conically
in the direction
of opening movement of the control piston.
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