Abstract: Method and apparatus for applying the measuring pads of a logging sonde against the walls of a borehole. Dip measurements and geological investigation of earth formations traversed by a deviated borehole require that the measuring pads be pressed against the borehole walls by means of articulated arms which maintain the pads symmetrical and parallel with respect to the sonde. In the preferred embodiment, two independent resilient forces are applied to the pads. The first resilient force is substantially constant at all extensions of the arms in the borehole, while the second resilient force is adjustable to suit local parameters. The second resilient force is preferably adjustable from surface instrumentation while the sonde is making measurements in the borehole. The first resilient force is provided by independent leaf springs acting on each of the pads, while the second resilient force is preferably provided by a coil spring acting on each of the pairs of opposing arms.

Abstract: In order to increase the angular field of observation of a logging sonde usable, in particular for dip metering, the sonde is equipped with measuring pads each comprising two independent flaps. The flaps of the same pad are hinged to a central element which is held permanently parallel to the axis of the sonde body, and they are applied against the wall of a borehole by blade springs. Each of the flaps carries an array of electrodes. The flaps of each of the measuring pads are circumferentially offset relative to each other so that the angular field of observation is increased without increasing the diameter of the sonde, once the pads have been retracted.

Abstract: Dip measurements and investigation of geological formations traversed by a deviated borehole is carried out by means of an apparatus comprising a measuring sonde and a cartridge connected to a cable. The sonde carries four measuring pads regularly distributed by means of articulated arms which keep the pads parallel to the axis of the sonde. The opposite arms are forced to stay symmetrical in relation to the sonde.The sonde is connected to the cartridge so that its axis can depart angularly from the axis of the cartridge, enabling the latter to rest on the borehole wall. The pads have a length smaller than twice the transverse dimension D of the sonde.

Abstract: A logging tool in accordance with the invention comprises a unitized electrode assembly adapted to be removably mounted on a central mandrel. The unitized electrode assembly comprises a metallic tube that is encased within an electrically-insulating sheath. An insulating sleeve surrounding the sheath carries various electrodes that are separated from each other by insulating spacers.

Abstract: In the representative embodiment of the new and improved apparatus disclosed herein, a so-called "stuck-point indicator" or "freepoint-indicator" tool includes a deformation-responsive sensor tandemly supported between upper and lower selectively-operated tool anchors of a unique arrangement which, in the preferred embodiment of the tool, are cooperatively arranged to be sequentially engaged with longitudinally-spaced wall portions of a string of well pipe believed to be stuck in a well bore. In the disclosed embodiment of the tool, each tool anchor respectively includes a set of pivoted anchor members and actuating links adapted to swing the anchor members outwardly into anchoring engagement with the pipe wall for securing the tool against longitudinal movement in the pipe string.

Abstract: In the representative embodiment of the new and improved apparatus disclosed herein, a so-called "stuck-point indicator" or "freepoint-indicator" tool includes a deformation-responsive sensor tandemly supported between upper and lower selectively-operated tool anchors of a unique arrangement which, in the preferred embodiment of the tool, are cooperatively arranged to be sequentially engaged with longitudinally-spaced wall portions of a string of well pipe believed to be stuck in a well bore. In the disclosed embodiment of the tool, each tool anchor respectively includes a set of pivoted anchor members and actuating links adapted to swing the anchor members outwardly into anchoring engagement with the pipe wall for securing the tool against longitudinal movement in the pipe string.