GB644466A - Apparatus for determining the dip of strata traversed by a bore hole - Google Patents

Abstract

644,466. Geological surveying; resistive measuring. SOC. DE PROSPECTION ELECTRIQUE PROCEDES SCHLUMBERGER. Dec. 31, 1947, No. 35096. Convention date, Jan. 1, 1943. [Class 37] [Also in Groups XX and XXXVIII] The angle of dip of earth strata is determined by lowering into a bore hole an assembly of at least three electrodes 37, 37<SP>1</SP>, 37<SP>11</SP>, Figs. 1, 1a, which are adapted to continuously engage the wall of the bore, and measuring the earth resistance to obtain at least three records 64, 64<SP>1</SP>, 64<SP>11</SP>, Fig. 3, which are generally similar but phase-displaced to an extent determined by the angle of dip. Each electrode may be in series with a recording instrument, and an A.C. source which is earthed, Fig. 5 (not shown). In an alternative arrangement, each electrode is earthed through a recorder, and an earthed D.C. source is connected to a further relatively large electrode in the bore hole. Preferably the electrodes are mounted in springy arms 36, Fig. 1, and the equipment kept axial of the bore hole by further springy arms 10. The orientation of the equipment is indicated by a magnetic needle 32, and its angle to the vertical by a ball 28 in a concave container 27 ; a source of light 26 is energized at will from the surface to record the position of the ball and the direction of the needle on a film 20, and a motor is similarly energized to step on the film, Fig. 5 (not shown). In a modification, pairs of electrodes 77, 78, Fig. 4, are mounted on articulated arms 76<SP>1</SP>, 79, mounted on a collar 80 which is pressed upwards by a spring 82, so that the elbows are urged outwards ; each arm 76 is connected by a pivoted linkage to a resistance 71, so that as each arm moves inwards or outwards, each resistance is moved upwards or downwards over fixed contacts ; these resistances are each connected to a D.C. source and a recorder, Fig. 8 (not shown), or are connected in series to a single source and a recorder, Fig. 9 (not shown), so that the records indicate the diameter of the hole. In this modification, each pair of electrodes is connected to a recording instrument, and an earthed D.C. source is connected to a further and relatively large electrode in the bore hole.