Recovery of underground hydrocarbons

The method of extracting hydrocarbons from an underground deposit of material containing hydrocarbons, which comprises:

• injecting a conducting aqueous solution into a portion of said underground deposit, and
• generating a varying magnetic field, at least a portion of said magnetic field including at least a part of said portion of said underground deposit into which said conducting aqueous solution has been injected, and
• collecting said fluid injected and fluids generated by the heating effect of said magnetic field on said portion of said underground deposit, and
• delivering said collected fluids to the input of a pressure controller, which substantially retards the flow of said collected fluids until the pressure at said input has risen to a selected value, corresponding to a selected temperature at which substantial pyrolysis occurs underground of hydrocarbons released by said heating effect of said magnetic field on said deposit containing hydrocarbons, but which is below the break-out value of fluids through the overburden of said deposit containing hydrocarbons, which passes fluids at said input to an external device at a rate which maintains said selected pressure substantially constant at the input to said pressure controller, and which passes said collected fluids substantially freely when said varying magnetic field is discontinued.