The method and improvement for recovery of hydrocarbons in situ from subterranean oil shale formations is disclosed by forming generally horizontal electrodes from the injection of molten metal into preheated or unheated fractures of the formation. A nonconductive spacing material is positioned in the casing of the bore hole between the electrodes. A fracture horizontally intermediate between the metallic electrodes is propped with a nonconductive granular material. Unterminated standing waves from a radio frequency (R.F.) generator are passed between the electrodes so as to heat the oil shale formation. The hydrocarbons in the formation are vaporized and are recovered at the surface by their migration through the intermediate fracture and tubing. By this method radial metallic electrodes can be formed at various depths throughout a subterranean oil shale formation so as to vaporize the hydrocarbons contained within the oil shale formation.
A method of completing a production well for the recovery of gas from a coal seam is disclosed. The well is of the type having a casing cemented in the well and the method comprises the steps of providing perforations in the casing above and/or below the coal seam, and hydraulically fracturing the coal seam through the perforations in the casing.
A single well method and apparatus for electrically applying heat and stimulating is comprised of a relatively lower surface area formation electrode and relatively high surface area overburden electrode extending downward into the borehole past low resistivity water zones. This long overburden electrode may be formed of nonmagnetic metal to reduce hysteresis losses in the electrode. This improved single well system causes most of power to be dissipated in the oil pay zone and thereby renders single well production economical.
A selectively electrically insulated, cemented and perforated tubular electrode provides a more effective system for electrically heating formations comprised of interbedded high and low electrical conductivity layers. The tubular electrode is located opposite the formation and is exteriorly insulated at an upper part of the formation and perhaps in low part of the formation. A central part of the tubular electrode is left free of electrical insulation. The tubular electrode is cemented in place and perforated at vertically spaced apart points into oil-bearing layers of the formation. The electrode may be a part of a casing string and the casing string specially designed to reduce alternating current hysteresis losses and current losses to the overburden.
A process and system for recovering hydrocarbonaceous products from in situ oil shale formations. A hole is drilled in the oil shale formation and a processing gas inlet conduit is positioned within the hole. A processing gas is pressurized, heated, and introduced through the processing gas inlet conduit and into the hole. The processing gas creates a nonburning thermal energy front within the oil shale formation so as to convert kerogen in the oil shale to hydrocarbonaceous products. The products are withdrawn with the processing gas through an effluent gas conduit positioned around the opening of the hole, and are then transferred to a condenser wherein a liquid fraction of the products is formed and separated from a gaseous fraction.
An electrode well is described which utilizes a hydraulic fracture filled with conductive proppant as an electrode of extended contact with a formation. A highly conductive section of cement liner around the casing delivers current to the proppant particles.
