GB676171A - Improvements in or relating to a method of and an apparatus for taking and orienting cores - Google Patents

Abstract

676,171. Marking cores to facilitate orientation. EASTMAN INTERNATIONAL CO. Sept. 7, 1950. No. 22070/50. Class 85. In an assembly of equipment for orientating a core, a sub 13 is inserted between the drill pipe 11 and core barrel B, said sub having at the lower end thereof a plate 22 and in the walls diametrically opposed magnets 18, 19. When the torsion is removed from the drill pipe after a core C has been drilled and before it is broken free at the base, a surveying instrument S is dropped down the drill pipe for determining the angle of inclination of the bottom of the bore. Said instrument comprises a magnetic disc cup that carries a sensitised disc, the cup taking up a predetermined position with respect to the magnets. Above said disc is a pendulum having associated therewith a light source and lens and a time switch so that, on operation of the switch, a mark is made on the sensitised disc, the position of the mark enabling the calculation of the required angle to be made. A spring-loaded plunger 27 at the head of the instrument marks the plate 22 when the instrument is correctly positioned. On the outside of the sub is marked an index line 20 which lies in the vertical plane of the magnets and, when the assembly is hauled out of the bore, a clamp K is positioned about the sub with a spring-loaded plunger engaging an indent 21 on the index line, said clamp carrying a sighting bar 29 the plane of which is a horizontal one at right angles to the vertical plane through the magnets. Another clamp K<SP>1</SP> is secured about the drill bit D, said clamp having a tapered holder 40 in which is positioned an arm 42 carrying a telescope 41 by the aid of which the clamp is adjusted until the two arms lie in the same vertical plane parallel to one another. The arm 42 is removed from the holder and a scribe arm inserted therein, the scribe arm being so shaped that a horizontal limb thereof is thus positioned in the vertical plane through the magnets. Thus a line scribed over the base of the core, in conjunction with the information from the survey instrument, enables the core to be oriented on a reader when released from the barrel.