GB1464464A - Drill comprising a tubular drill string and apparatus releasably connectable to the bottom of said drill string - Google Patents

Abstract

1464464 Drilling tools MINDRILL Ltd 25 April 1974 18071/74 Heading E1F A drill tool of the type capable of being run into and retrieved through a drill string is shown as including a core barrel 25 with a core bit 30 for drilling a hole which is reamed to a site to suit the drill string by cutter elements 68 carried by a tubular member 28 forming part of a central tubular assembly 27 axially movable within an outer tubular assembly 52 connected to the core barrel via a fitting 57 incorporating a detent ring 122, 123 adapted to retain the central assembly 27 in an upper position in which the cutter elements are retracted through radial windows 66 by fingers 84 pinned to member 28. The central assembly 27 carries a spear head 41 and can support the outer assembly 52 via shoulders 140, 141 during introduction or retrieval of the tool. The tool can be run in on a wireline, in which case the spear head will be in an upper position supporting the central assembly 27 via shoulders 47, 49 and allowing bypass flow via slots 120 and ports 125. Alternatively, the tool can be dropped through the drill string and in this case the bypass flow is allowed by a check ball 111. When the tool arrives in position, the outer assembly 52 engages a seat 61 in the drill string and although the central assembly 27 initially remains held in its upper position by the detent ring, the spear head is depressed by spring 44 to block the upper end of the outer assembly 52 so that the central assembly can be pumped downwards to cam the cutter elements 68 outwards to positions in which they are engageable by the lower end of the drill string 26 which can thereby be used to apply weight to the core bit 30. The downward movement of the central assembly is limited by abutment of shoulder 113 against member 121, and in the lower position of the central assembly a necked portion 114 of the spear head aligns with the top of the outer assembly 52 to permit flow of drilling fluid into radial ports in the central assembly. Downward movement of the central assembly 27 also functions to release dogs 92 which are then moved by springs through windows in the outer assembly and which engage in windows 108 in the drill string, upon rotation of the latter, and thereby serve to transmit drill string rotation to the tool. When the tool is to be retrieved, it is first lifted slightly by the drill string, via shoulders 59, 61 to break the core, and then the spear head is engaged by a wireline overshot and moved upwards to abut the central assembly (at 47, 49) and lift the latter to retract the dogs 92 and the cutters 68. The central assembly 27 eventually abuts the outer assembly 52 at 140, 141 and lifts the latter, the required bypass flow being permitted by slots 120 and ports 125. The tool may alternatively employ a solid bit in place of the core barrel.