GB1346503A - Shoe for use in apparatus for investigating earth formations surrounding a borehole - Google Patents

Abstract

1346503 Borehole logging SCHLUMBERGER INLAND SERVICES Inc 19 April 1971 [6 March 1970] 24205/71 Heading G1N A borehole logging electrode assembly shoe includes a plate of insulating plastics material in or on one face of which is mounted the electrode assembly, the arrangement being such that part of the electrode assembly is flexible and part rigid so as to be able to conform to the borehole wall. The sonde 1 includes two shoes 4 mounted by thrust arms 5, 6 for movement into and out of engagement with the bore wall 10. The major part of each shoe 4 consists of a flexible plate 12 of an elastomer reinforced by central back rib 20 including a rigid parallelopiped box 22 Fig.2 defining a cavity 30 and which is mounted on sole 8. Two central electrodes 14, 15 made of rigid metal pieces are screwed 41, on to the base of the box 22 adjacent the front surface 13 of the shoe and separated from each other by neoprene inserts 42, Fig.3 (not shown) such that the electrodes 14, 16 are slightly recessed with respect to plate 12 and insert 42 and have transverse dimensions not exceeding the width of box 22. Rectangular frame electrode 17 includes two flexible transverse sides 44, 45 composed of hard carbon steel spring blades which are screwed, Fig.4 (not shown) on to the base of box 22 in their middle part. The electrode proper includes conducting strips 48 welded to the middle portions of the spring blades and metal platelets 50, 51, 52 welded to the outer portions of the spring blades. The electrode elements are separated by insulation inserts so as to be recessed. The frame is completed by rigid connecting strips 60 set in the plate 12. Electrodes 16 and 18 are formed in a similar manner except that in the case of electrode 16 the transverse sides are only composed of conductive strips 48. The electrodes are connected to connectors 34 mounted in the cavity 30 which may be filled with grease.