EMF SACRIFICIAL ANODE SUB AND METHOD TO DETER BIT BALLING

摘要

A sacrificial anode sub (150) and method are dislosed which provide a lower voltage at the approximately located bit (202) than at the sacrificial anode (162) disposed on sub (150) to thereby deter bit balling. An electromotive force (emf) dynamo (180) is built into the sacrificial anode sub (150) to provide direct current voltage source for this purpose. Annular insulator (170) electrically insulates sacrificial anode (162) from tubular body (152). An electrical connection to drill bit (202) is made through threaded lower connector (160) with bit (202). Impeller (182) rotates in response to drilling fluid flow (184) to rotate the rotor assembly (186) of dynamo (180).