| 摘要 |
495,867. Prospecting for minerals etc.; photographic apparatus. SOC. DE PROSPECTION ELECTRIQUE (PROCEDES SCHLUMBERGER). March 12, 1937, No. 7372. Convention date, March 18, 1936. [Class 37] [Also in Group XX] The direction, and, if desired, the value of the dip of the strata cut by a borehole are determined by lowering a supporting structure into the borehole and measuring the spontaneous potential differences existing at points in a given transverse layer, one movable, or more than one fixed or movable electrode in relation to the structure being provided, together with means for measuring the orientation of the electrode or electrodes. The measurements may be made with potentiometers or millivoltmeters between one electrode and earth potential, or between pairs of electrodes. Measurements of the inclination of the borehole are also made. In one arrangement, Fig. 2, electrodes 2 .. 4 are carried by lateral arms connected to the conductor cable 1 centred in the structure 5 by resilient endpieces 6, 7 contacting with the wall of the borehole. Also located in the structure 5 are a level 11, compass 12 and camera 9 for recording the orientation of the electrodes and inclination of the borehole axis. In a modification, a single electrode may be rotated by a motor in the borehole, or, as shown in Fig. 7, the three electrodes 2 .. 4 can be connected to segments 16 .. 18 over which a brush 19 is driven by motor 20, the output being delivered to the measuring instrument or instruments by conductor 43. The segments 16 .. 18 are of different length, so that a recording instrument will show traces of different thickness and thus identify the potential with a particular electrode. In a further modification, a single electrode is rotated in the borehole and is electrically connected to a brush sweeping over a collector having a single break in its circuit. Four electrodes may be employed in collecting the spontaneous potentials from points located at the corners of a square, the relationship of the potentials between pairs, or between each electrode and a common earth, being measured. |
