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Abstract

A.C. electrical heating system for heating a fluid reservoir (deposit) in the vicinity of a mineral fluid well, usually an oil well, utilizes A.C. electrical power in a range of 25 Hz to 30 KHz. The well has a borehole extending down through an overburden and into a subterranean fluid (oil) reservoir. There is a well casing including an upper electrically conductive casing around the borehole in the overburden, and at least one electrically conductive heating electrode located in the reservoir to deliver heat to the reservoir. An electrically insulating casing is interposed between the upper casing and the heating electrode. An electrically isolated conductor extends down through the casing. The heating system further includes an electrical A.C. power source having first and second outputs; the power source is usually located at the top of the well. There is a downhole voltage-reducing impedance transformation network having a primary and a secondary; in one described construction this network includes a step-down transformer. The primary of the transformation network is connected to the outputs of the power source. The secondary of the transformation network is connected to the downhole heating electrode.

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First Claim