Downhole seismic exploration device and apparatus

• US 5,044,460 A
• Filed: 03/08/1990
• Issued: 09/03/1991
• Est. Priority Date: 07/24/1985
• Status: Expired due to Fees

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Kamata, Masahiro, Porter, Robert, Katayama, Shitomi, Mons, Francis
• Primary Examiner(s): Steinberger, Brian S.
• Application Number:
  US07/490,187
• Time in Patent Office: 544 Days
• Field of Search: 367/25-35, 367/911, 367/912, 181/102-106, 181/108, 181/112, 181/401, 73/151, 73/152, 324/323, 324/366, 324/368, 166/248, 166/250, 166/254, 175/40, 175/50, 335/288, 335/290
• US Class Current: 181/102
• CPC Class Codes: G01V 1/16 Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
• CPC Class Codes: G01V 11/005 Devices for positioning logging sondes with respect to the borehole wall centralising devices for drilling rods or pipes E21B17/10; setting or locking tools in boreholes E21B23/00; locating objects in boreholes E21B47/09
• CPC Class Codes: Y10S 181/401 Earth
• CPC Class Codes: Y10S 367/911 Particular well-logging apparatus
• CPC Class Codes: Y10S 367/912 Particular transducer

Abstract

A downhole seismic exploration device comprises a seismic detector such as a geophone and a magnetic clamp, supported by O-rings in an open cradle carrier which can be secured to a cable linking several such devices into an array. The array is lowered into a cased borehole and the magnetic clamps are operated to clamp the devices temporarily to the casing. Seismic signals detected by the geophones are transmitted to the surface via the cable, the O-ring supports acting to reduce or eliminate transmission of vibrations from the borehole fluid and the cable via the carrier to the geophone. The array is then unclamped and moved to another location in the borehole and the operation repeated. The magnetic clamp comprises a rotatable permanent magnet with radial poles disposed between a pair of parallel pole piece plates protruding on each side of the device and separated by non-magnetic blocks on eahc side of the magnet. When the magnet poles are aligned parallel to the pole piece plates the magnetic flux extends along closed paths entirely within the pole pieces and there is no clamping action. When the magnet is rotated 90° by a small motor the magnetic flux extends along the pole pieces and out of the device, clamping the device by magnetic attraction to the casing. A piezo bimorph element can be operated to vibrate the device to test the quality of the clamping before the acquisition of seismic data.

Claims

1. A device for use in geophysical exploration of earth formations traversed by a borehole, comprising:

sensor means having detecting means for detecting seismic acoustic data and having a clamping means for clamping the sensor means to a wall of a borehole;

carrier means for carrying the sensor means, the carrier means defined by a front end block, a rear end block spaced from the front end block, and a pair of side blocks extending in parallel between the front and rear end blocks, the front end block being adapted for connection to a first point of a cable and the rear block being adapted for connection to a second point of the cable, and at least one of the pairs of side blocks being formed with a conduit passage for receiving conductors of the cable; and

damping means, comprising two O-rings interposed between the sensor means and the carrier means, for acoustically isolating the carrier means from the sensor means when the sensor means is clamped to the wall of the borehole.

2. The device of claim 1, wherein the two O-rings are respectively mounted on the front end block and the rear end block to acoustically isolate the carrier means from the sensor means.

3. The device of claim 2, the sensor means having seats at opposite ends for respectively receiving the two O-rings.

4. The device of claim 3, the front end block and the rear end block each having shoulders that respectively abut the two O-rings.

5. A device for use in geophysical exploration of earth formations traversed by a borehole, comprising:

sensor means having detecting means for detecting seismic acoustic data and having a magnetic clamping means for clamping the sensor means to a wall of a borehole;

carrier means for carrying the sensor means and adapted for connection to a cable;

damping means comprising two O-rings interposed between the sensor means and the carrier means for substantially acoustically isolating the carrier means from the sensor means when the sensor means is clamped to the wall of the borehole.

6. The device of claim 5, the sensor means having seats at opposite ends for respectively receiving the two O-rings.

7. The device of claim 6, the carrier means having shoulders at opposite ends for respectively abutting the two O-rings.