Importance

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Abstract

A rotary drill bit comprising a bit body adapted to be secured to a drill string and to receive drilling fluid under pressure therefrom, the body having a plurality of nozzles for exit of the drilling fluid, and a plurality of depending legs at its lower end. The bit further includes a plurality of roller cutters, one for each leg, each cutter comprising a generally conical cutter body rotatably mounted on the respective leg, and a plurality of cutting elements thereon. The cutter body at its conical surface is formed of a material resistant to erosion by high drilling fluid which may impinge it. Each nozzle directs the drilling fluid to flow in a stream generally toward the cutter body of an adjacent roller cutter, with the stream impinging at least one cutting element on the cutter body and thereafter impinging a portion of the bottom of the well bore forward of the bottom of the adjacent roller cutter, whereby the drilling fluid sequentially impinges and cleans first cutting elements and then portions of the well bore bottom immediately prior to their engagement for enhanced drill bit cutting action.

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First Claim