Ideas to Design an in situ Diamond Drilling Core Splitter within Soft Rocks

Abstract

Diamond drilled cylindrical rock (core) from the earth is usually extracted using a drill rig. This is followed by splitting, at the surface with the aid of diamond impregnated saw blade, for good visual examination before sampling for analysis. The challenges in core splitting are imperfect division, time consuming, labour intensive and dust generation. This paper studied the wireline system of core barrel assembly and the device used in splitting of core (core splitting machine) at the surface, to provide ideas which would help design a mechanism that would take care of the splitting of the core in situ (i.e. at depth during the drilling process). Modifications of the core barrel assembly of the wireline system are such that the outer tube assembly is designed to have two ball bearings moulded with it. The back end assembly is designed to have a latching system which could operate independently. Also a static diamond cutting blade is inserted in the core lifter to split soft rocks or saprolite (with hardness of less than 5 on the Mohr’s scale) when a resultant feed force is applied. The stop ring in the inner tube should effectively grab the split core to prevent it from dropping and also protect the split core from washing away. Drilling at short intervals with controlled drill fluid usage is recommended in saprolite zone. Following the ideas provided, an in situ core splitter could be designed to eliminate hazards associated with conventional core splitting on the surface, save time and reduce dust generation.

Keywords: Design, In situ, Diamond drilling, Core splitter, Wireline system