Abstract: Low-flux-leakage cables and cable terminations for an A.C. electrical heating system that heats a fluid reservoir around a mineral fluid well, usually an oil well; the system utilizes A.C. electrical heating power in a range of 25 to 1000 Hz. The well has a borehole extending down through overburden formations and through a subterranean fluid reservoir; the well includes an electrically conductive upper casing in the overburden, an electrically conductive heating electrode located in the reservoir, and an electrically insulating casing between the upper casing and the heating electrode. The cable extends down through the upper casing and is connected to the heating electrode to supply electrical power to the electrode. The power cable has two or three electrical conductors which are electrically isolated from each other, enclosed within a steel sheath.

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.

Abstract: Electrical power sources and systems for heating in or adjacent to an oil well or other mineral well, or for heating other earth media, each comprising an A.C. heating generator that generates an A.C. heating current at a selected heating frequency substantially different from the conventional 50/60 Hz frequency used by power companies; the heating generator may comprise an A.C. to D.C. converter for developing an intermediate D.C. output of predetermined amplitude from a conventional 50/60 Hz A.C. input, and a solid state switching circuit for repetitively sampling the D.C. output of the converter at the selected heating frequency, usually in a range of 0.01 Hz (or even lower) up to about 35 Hz. A heating rate control varies the energy content and the frequency of the A.C. output to suit well requirements.

Abstract: Electrical heating system for mineral wells, particularly oil wells, in which the reservoir or "pay zone" is heat stimulated or some well components (e.g., the tubing) are heated, or both, by electrical power supplied to a multi-perforate electrode have the operating efficiency enhanced by effectively terminating the heating electrode, at both its top and bottom, at a distance inwardly of the pay zone equal to at least three times the diameter of the well casing. In some systems the electrical power connection to the main heating electrode is made through a section of the production tubing of the well, with an electrical contactor interconnecting the tubing and the electrode in the level of the pay zone; these systems also provide electrical isolation, within critical height limits, for the production tubing and the pump rod. Delivery of electrical power downhole of the well may be accomplished through an electrical cable, which may or may not be appropriately armored.

Abstract: 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.

Abstract: Corrosion inhibition apparatus in an electromagnetic heating system for in situ downhole heating in an oil well or other mineral fluid well that includes an A.C. power source for a high amperage, low frequency heating current (e.g. over 50 amperes at 0.01 to 35 Hz) and a D.C. bias source for generating a low amplitude (e.g., less than one ampere) current for corrosion inhibition, both sources connected to a downhole electrode. The bias source includes at least one semiconductor device, connected in the main A.C. heating circuit, in a bias circuit that develops a net D.C. voltage differential of the polarity required for corrosion inhibition in response to the A.C. heating current.

Abstract: Method and apparatus for enhancing liquid hydrocarbon production through a single traditional producing borehole recognizing traditional producing well spacing from a slowly producing formation by use of non-uniform heating through interrelated electrode arrays surrounding the borehole. Heating the formation around the borehole through an interrelated electrode array designed for the formations geometry and geophysics favorably redistributes the pressure gradient throughout the formation for a substantial distance beyond the borehole permitting net energy effective production. One optimum electrode array may consist of ring electrodes or electrode segments so disposed as to electrically approximate a ring. Electrically conductive well bore casing in the formation may be used as an electrode. A return electrode of low impedance disposed close to the surface of the earth may be utilized.