A well heater is provided, the heater effective for heating earth surrounding a wellbore from the wellbore, the well heater including: a) a resistive heating element, the resistive heating element traversing a segment of the wellbore to be heated; b) more than one ceramic insulators, the ceramic insulators defining a channel through which the resistive heating element passes; and c) a support element connected to at least one ceramic insulator, the support element effective for conducting heat from the ceramic insulator and radiating heat to the wellbore wall, and to support the weight of the electrical resistance element and the ceramic insulators through the connection to the at least one ceramic insulator. The wellbore heater of the present invention is easily fabricated from available materials, and provides a reliable and inexpensive wellbore heater.

A method for heat injection into a subterranean diatomite formation is provided. The method utilizes a heater that is placed directly in the diatomite formation without cement around the heater. Diatomite is very soft, and will quickly fill in around the heater, operation of the heater will sinter the diatomite and significantly increase the original thermal conductivity and strength of the diatomite.

A heater is disclosed, the heater comprising: a heating element effective to generate radiant energy; a casing surrounding the heating element separated from the heating element; and support material between the casing and the heating element wherein the support material comprises a granular solid material that is translucent to radiant energy in the peak wavelength of energy which is radiated by the heating element at operating temperatures. The translucency of the support material is such that at least 50% of the radiant energy emitted by the heating element is radiated to the casing.

A method for heat injection into a subterranean diatomite formation is provided. A heater is placed in a wellbore within the diatomite formation, and the heater is then operated at a temperature above that which the heater could be operated at long term in order to better sinter the formation in the vicinity of the wellbore. The improved sintering of the diatomite significantly improves the heat transfer coefficient of the diatomite and thereby increases the rate at which heat can be injected from a constant limited long term heater temperature.

An electrical heater is provided, the electrical heater being useful for heating soil around a wellbore, and the heater including: a plurality of electrically conductive heater elements within a wellbore, each element spaced from the other elements and located around the circumference of a wellbore; and an electrically insulating filer surrounding the elements within the wellbore; wherein a metal casing around the heater is not present.