| 摘要 |
1,228,925. Oil wells. ELECTROTHERMIC CO. 10 Oct., 1968 [16 Oct., 1967; 30 Sept., 1968], No. 48133/68. Heading E1F. [Also in Division H5] An underground oil bearing formation is heated by the passage of electricity through water in the formation. Alternating current may be supplied through the casing and tubing of a well, with a fibre glass sleeve or spaced insulators being used to prevent contact being the casing and tubing. Connate water in the formation may be heated, while additional water containing conductive salts may be supplied from the surface through the tubing, through the annulus between the tubing or sleeve and the casing, or through a pipe between the tubing and casing. The rate of supply of water may be varied in dependence on the current flowing through the well or on whether the depth of water in the well is above or below an electric measuring instrument. Instead of the bottom of the casing and tubing acting as electrodes, a portion of the casing just above the formation may be replaced by a non-conductive sleeve or by concrete with the bottom of the tubing being connected by a centralizer to the portion of the casing within the formation so that the portions of the casing above and below the replaced portion act as electrodes. The casing may be replaced as a conductor by a tubing concentric with the other tubing and spaced therefrom by insulation. Current may be caused to flow between tubings of spaced wells. In this case if there is a conductive stratum above the formation the bottom of the casing is insulated therefrom by the casing either being coated with an epoxy resin or having a gap therein. A packer may be arranged below the gap and oil inserted above the packer and in the gap. In an example described the formation adjacent a central well is heated and oil withdrawn from the wells in an inner ring surrounding the central well. Current is then passed between the central well and the wells in the inner ring with oil being produced from wells in an outer ring. Water flood techniques may be used, or steam flood techniques used by heating the water in the formation under pressure and then releasing the pressure. |
