Subassembly electrical isolation connector for drill rod

Abstract

A subassembly electrical isolation connector for interconnecting adjacent tubular drill rods of a drilling system used in drilling bore holes in earth formations electrically isolates the inner connection of the drill rods. The connector comprises a housing, a mandrel, a connector for connecting the housing to a first tubular drill rod, a connector for connecting a mandrel to a second tubular drill rod and a device for interconnecting the housing and the mandrel in a manner to electrically isolate the housing from the mandrel with the housing overlapping at least a portion of the mandrel. The housing has an isolated end which is electrically isolated from the mandrel and the connector for connecting the mandrel to a second tubular drill rod. The mandrel has a conical tapered body portion which is located within the housing and the housing has a corresponding conical tapered inner surface. The conical taper for the housing and the mandrel converge inwardly away from the housing isolated end. Such arrangement provides enhanced strength to resist bending moments along the connector and resisting drilling forces. The tapered surfaces provide for a connector retrieval in the event of connector break-up due to excessive drilling forces. The subassembly is particularly useful in applications involving directional drilling in earth formations, particularly oil well drilling, the drilling of bore holes under river beds and other obstacles and earth formations, bore hole inspection systems, directional drilling in respect of geothermal wells, ventilation shaft drilling in mineral mining formation and the like.