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Method and apparatus for corrosion inhibition in an electromagnetic heating system for heating a portion of a mineral fluid deposit adjacent an oil well or other mineral fluid well, in situ. The preferred apparatus includes a power source, that develops a high amperage heating current, over 100 ampe

Method and apparatus for corrosion inhibition in an electromagnetic heating system for heating a portion of a mineral fluid deposit adjacent an oil well or other mineral fluid well, in situ. The preferred apparatus includes a power source, that develops a high amperage heating current, over 100 amperes, at a heating frequency usually in a range of from 0.01 Hz or lower to 35 Hz, in a heating circuit that includes a main heating electrode downhole of the well and a return electrode. The power source also supplies a very low amplitude, controlled D.C. bias current to those electrodes, maintaining the main electrode at a neutral or negative polarity for corrosion protection. The D.C. bias current is monitored and maintained below a given minimum level, usually about one ampere, to extend the effective life of the return electrode and to minimize corrosion protection costs.

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A method of corrosion inhibition in an electromagnetic heating system for a mineral fluid well, the heating system including a heating circuit comprising a heating electrode located downhole in the well, and an electrical power source connected to the heating circuit and operating to maintain a high

A method of corrosion inhibition in an electromagnetic heating system for a mineral fluid well, the heating system including a heating circuit comprising a heating electrode located downhole in the well, and an electrical power source connected to the heating circuit and operating to maintain a high amplitude A.C. heating current in the heating circuit, the method comprising the following steps: A. applying a low D.C. bias voltage to the heating circuit, in addition to the high amplitude heating current, with a polarity to inhibit corrosion of the downhole heating electrode; B. sensing the D.C. bias current in the heating circuit; and C. adjusting the D.C. bias voltage to maintain the D.C. bias current sensed in step B below a given minimum level. In an electromagnetic heating system for an oil well or other mineral fluid well, including a main heating electrode located downhole in the well at a level adjacent a mineral fluid deposit, and a return electrode at a location remote from the main electrode so that an electrical current between the electrodes passes through and heats a portion of the mineral fluid deposit, electrical energizing apparatus comprising: a A.C. power source for generating an high amplitude A.C. heating current, of at least fifty amperes; a D.C. bias source for generating a low amplitude D.C. bias current having a polarity such as to inhibit corrosion at the main electrode; and connection means for applying both the A.C. heating current and the D.C. bias current to the electrodes of the well heating system.