Acoustics – Geophysical or subsurface exploration – Well logging
Reexamination Certificate
2000-03-14
2001-11-13
Nappi, Robert E. (Department: 2837)
Acoustics
Geophysical or subsurface exploration
Well logging
C181S105000, C181S112000, C181S122000, C175S081000, C175S083000, C175S230000, C367S035000, C166S382000, C166S206000
Reexamination Certificate
active
06315075
ABSTRACT:
TECHNICAL FIELD
The present invention relates to borehole logging tools, and in particular to aspects of an actuating mechanism for a seismic shuttle logging tool in which a sensor package is urged against the wall of a borehole.
BACKGROUND ART
Seismic shuttle logging tools are know for use in performing vertical seismic profile surveys from boreholes to evaluate the surrounding underground formations. A multi-shuttle seismic tool comprises a number of similar tools (shuttles) linked together by means of a cable and logged through a borehole while seismic signals are generated at the surface. At each measurement level, each shuttle is anchored to the wall of a borehole during a measurement operation by means of an anchoring arm. In VSP surveys, it is necessary to make measurements at a number of levels in a borehole so the tool anchoring must be released to allow the tool to be moved and then re-engaged at the next level. The time taken for the anchor to release and to re-engage can be a significant factor in the time taken to make a measurement at each level. In Schlumberger's Combinable Seismic Imager tool (CSI) the anchoring arm of each shuttle extended under spring bias and a drive motor is used to provide the anchoring force or retraction. Aspects of the CSI are described in U.S. Pat. No. 4,563,757; U.S. Pat. No. 4,575,831; U.S. Pat. No. 4,987,969; and U.S. Pat. No. 5,200,581. In particular, patents '757 and '831 relate in particular to the anchoring mechanism and procedure. A schematic figure from the patents is shown in FIG.
1
. This prior art arrangement includes a motor
35
, an output reducer
36
with an electromagnetic brake
37
and an output shaft to a coupling device
39
comprising a clutch
50
, a mechanical logic
51
and torque limiter
54
. The mechanical logic
51
includes studs located in helical, V-shaped, cam slots which serve to bring the clutch into engagement on operation of the motor. Drive is transmitted to a push rod
34
connected to the anchoring arms
31
,
32
by means of a ball screw
40
and nut
41
. The anchoring arms are urged away from the tool body
29
by a leaf spring
43
which is fixed to the tool body
29
and bears upon the arm
31
. When in the open position, a pad
30
at the end of the arms
31
,
32
engages the borehole wall and causes the tool body
29
to be pushed against the opposite side of the borehole where it can be anchored for use. The motor
35
is used to provide the extra anchoring force to the arms
31
,
32
and to withdraw the arms when the tool is run in or pulled out of the borehole. When the tool is to be moved to a different level, the action of the clutch
50
allows the motor to be disengaged and the arms held only by the force of the leaf spring
43
.
The present invention has as its object a tool which has an anchoring arm which can be anchored and released in a relatively short time and in which the anchoring mechanism can be relatively compact.
DISCLOSURE OF INVENTION
The present invention provides a borehole tool comprising a tool body having at least one sensor package and an anchoring mechanism, the anchoring mechanism comprising:
a) a drive mechanism including a motor, a drive shaft and a clutch;
b) an anchoring arm moveable between first and second positions relative to the tool body;
c) a push rod connecting the anchoring arm to the drive mechanism; and
d) a spring acting to bias the arm into a first position relative to the tool body;
characterised in that the push rod extends through the clutch mechanism and is engaged by the spring to bias the arm into the first position, and is also driven by the drive mechanism through the clutch to move the arm between the first and second positions.
The invention is particularly applicable to shuttle-type seismic borehole logging tools although may also be applicable to any other type of borehole tool which requires the tool body to be urged against the borehole wall. The provision of the push rod extending through the clutch mechanism allows the overall length of the anchoring mechanism to be reduced over that provided by the prior art device. The sensor package can be a separate package with one or more sensors mounted on the tool body or one or more sensors and associated electronics mounted in the tool body.
It is particularly preferred that a ball-bearing clutch is used which comprises a collar having a number of balls which engage in grooves in the push rod to allow the drive mechanism to move the arm. A spring loaded retaining ring can be provided to hold the balls in a driving position in the grooves when engaged by the collar.
The drive shaft is typically a drive screw and a nut is used to transmit the driving force to the push rod. Driving force can be applied either through the clutch or by bearing surfaces on the nut which engage directly extensions of the push rod. The two mechanisms can be used to provide reversible drive to the push rod.
The spring can be a coil spring which is located in the tool body around the drive mechanism. Other arrangements of springs or resilient biasing means can be used to urge the arm into the first position.
The arm can be mounted on a pivot on the tool body with the first position being extending away from the tool body and the second position being along the tool body. Thus, the spring can be used to urge the arm away from the tool body and the motor used to provide further drive in this direction for anchoring force, or to provide a counteracting drive to withdraw the arm to the tool body. By reversing the drive to release the clutch, the arm can be held under spring force alone while the tool is moved in the borehole.
An arm position sensor can be used to indicate the exact position of the arm after movement.
REFERENCES:
patent: 4130816 (1978-12-01), Vogel et al.
patent: 4184546 (1980-01-01), Nicolas et al.
patent: 4616703 (1986-10-01), Laurent et al.
patent: 4819760 (1989-04-01), Petermann
patent: 5528556 (1996-06-01), Seeman et al.
patent: 5829531 (1998-11-01), Hebert et al.
Christian Steven L.
Martin Edgardo San
Nappi Robert E.
Schlumberger Technology Corporation
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