Methods are provided that include the steps of providing wells in a formation, establishing one or more fractures (12) in the formation, such that each fracture intersects at least one of the wells (16, 18), placing electrically conductive material in the fractures, and generating electric current through the fractures and through the material such that sufficient heat (10) is generated by electrical resistivity within the material to pyrolyze organic matter in the formation into producible hydrocarbons.
A method for lowering the temperature of a portion of a subsurface formation is provided. Preferably, the formation is an oil shale formation. The method includes the step of injecting a cooling fluid under pressure into a wellbore, with the wellbore having been completed at or below a depth of the subsurface formation. In one embodiment the wellbore has an elongated tubular member for receiving the cooling fluid and for conveying it downhole to the subsurface formation. The wellbore also has an expansion valve in fluid communication with the tubular member through which the cooling fluid flows. The method then includes the steps of injecting a cooling fluid under pressure into the wellbore, and expanding the cooling fluid across the first expansion valve. In this way, the temperature of the cooling fluid is reduced. The temperature of the surrounding formation is likewise reduced through thermal conduction and convection. In another embodiment, a partially frozen slurry is used as the cooling fluid.
A method for lowering the temperature of a portion of a subsurface formation is provided. Preferably, the formation is an oil shale formation. The method includes the step of injecting a cooling fluid under pressure into a wellbore, with the wellbore having been completed at or below a depth of the subsurface formation. The wellbore has an elongated tubular member for receiving the cooling fluid and for conveying it downhole to the subsurface formation. The wellbore also has an expansion valve in fluid communication with the tubular member through which the cooling fluid flows. The method then includes the steps of injecting a cooling fluid under pressure into the wellbore, and expanding the cooling fluid across the first expansion valve. In this way, the temperature of the cooling fluid is reduced. The temperature of the surrounding formation is likewise reduced through thermal conduction and convection.
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 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.
