Abstract: Shale oil is produced from a subterranean interval of oil shale, where the interval is initially substantially impermeable and contains a specified grade and thickness of oil shale. Said interval is conductively heated from borehole interiors which are kept hotter than about 600.degree. C. and are heated at a rate such that kerogen pyrolysis products formed within the oil shale create and flow through horizontal fractures which subsequently extend into fluid-producing wells that are positioned in specified locations.

Abstract: An electrical resistance heater capable of generating heat at different rates at different locations along its length comprises a continuous and unitary electrical conductor having a thickness which is different at different locations along its length.

Abstract: Hot liquid-containing water-swollen tar is produced from a tar sand by injecting steam into a well, which is at least initially open and substantially free of obstruction to vertical fluid flow throughout a long vertical interval from the bottom of the tar sand, by producing said liquid from the bottom of the tar sand and maintaining injection and production flow rates that keep the steam temperature above about 450.degree. F. at a pressure high enough to keep the produced liquid substantially free of steam and near to, but less than high enough to damage the reservoir.

Abstract: In treating a well, automatically controlled measurements of temperature with depth within a subterranean interval which can be longer than hundreds of feet, deeper than thousands of feet and hotter than 600.degree. C., are made by extending a slender measuring means conduit through the well and the zone to be measured and arranging an electrically responsive temperature sensing means and a means for spooling a metal sheathed telemetering cable for the electrical temperature responses so that the sensing means is lowered through the measuring conduit by gravity and raised within the conduit by spooling and temperatures and/or temperature with depths are measured while the sensing means temperature is substantially in equilibrium with the temperatures in the interval being measured.

Abstract: A well heater is installed in a well by spooling electrical cable assemblies for heating and supplying power, in proper sequence, on at least one spooling means, unspooling them and attaching them to a heat- and tension-stable support means as the resulting assembly is drawn into the well by a weight attached to the support means.

Abstract: Long intervals of subterranean earth formations are heated at high temperatures for long times with an electrical heater containing spoolable, steel sheathed, mineral insulated cables which have high electrical conductivities, enabling them to heat the earth formations at a substantially uniform rate of more than about 100 watts per foot at temperatures between about 600.degree. and 1000.degree. C., with a pattern of localized electrical resistances which are correlated with the heat conductivities of the earth formations and the heat stabilities of materials providing power and support for the heater.