A well tool and method for heating and depositing first and second charges of selective temperature melting metal alloys for repairing failure spots along a section of a tubular conduit, such as casing, in a subterranean well. A fuel charge is provided and is ignited to first melt the lower temperature melting metal alloy charge and thereafter the higher temperature metal alloy charge, such that a metal precipitate is formed from the heated higher temperature melting metal alloy charge. The housing defines a sacrificial wall which is opened or cleared as the higher temperature metal alloy charge melts, thus enabling the precipitate of the higher temperature melting alloy charge to be discharged from the housing to form a bridge for subsequent movements thereacross of the lower temperature melting alloy charge, into the well immediate the area of the failure spots. The failure spots are filled and/or covered by the precipitate and the lower temperature metal alloy charge to enhance the integrity of the tubular conduit such that production or other efforts may be continued within the well.

A method for treating an oil shale formation comprising nahcolite includes providing a first fluid to a portion of the formation. A second fluid is produced from the portion. The second fluid includes at least some nahcolite dissolved in the first fluid. A controlled amount of oxidant is provided to the portion of the formation. Hydrocarbon fluids are produced from the formation.

A system for treating a tar sands formation is disclosed. A plurality of heaters are located in the formation. The heaters include at least partially horizontal heating sections at least partially in a hydrocarbon layer of the formation. The heating sections are at least partially arranged in a pattern in the hydrocarbon layer. The heaters are configured to provide heat to the hydrocarbon layer. The provided heat creates a plurality of drainage paths for mobilized fluids. At least two of the drainage paths converge. A production well is located to collect and produce mobilized fluids from at least one of the converged drainage paths in the hydrocarbon layer.

A system for heating a hydrocarbon containing formation is described. A conduit may be located in an opening in the formation. The conduit includes ferromagnetic material. An electrical conductor is positioned inside the conduit, and is electrically coupled to the conduit at or near an end portion of the conduit so that the electrical conductor and the conduit are electrically coupled in series. Electrical current flows in the electrical conductor in a substantially opposite direction to electrical current flow in the conduit during application of electrical current to the system. The flow of electrons is substantially confined to the inside of the conduit by the electromagnetic field generated from electrical current flow in the electrical conductor so that the outside surface of the conduit is at or near substantially zero potential at 25.degree. C. The conduit may generate heat and heat the formation during application of electrical current.

A method for treating an oil shale formation comprising dawsonite includes assessing a dawsonite composition of one or more zones in the formation. Heat from one or more heaters is provided to the formation such that different amounts of heat are provided to zones with different dawsonite compositions. The provided heat is allowed to transfer from the heaters to the formation. Fluids are produced from the formation.