Development of a Novel Downhole Heating Tool for Paraffinic and Heavy Oil Wells

Abstract A downhole tool has been developed that provides efficient heating of wellbores in any rod-pumped oil and gas well. The tool does not use any electrical wires in the wellbore and has a minimal influence on existing pumpjack equipment. The downhole heat may be used for many applications including preventing paraffin formation in wells, the production of heavy oil, and the prevention of hydrate plugs. Present technologies use the galvanic transmission of electricity from the surface to supply in-well ohmic heaters. This requires cables to be fed down the well with the tubing string, surface transformers and controllers, and special penetrations of the well head and tubing hanger to accommodate the cables. The new tool presented here uses permanent magnets installed in a Halbach array in the tubing to induce eddy current heating in the well by converting the linear motion of the sucker rod to rotary motion of a conducting tube using a lead screw. No cables, surface equipment, or special penetrations are required. The tool directly integrates with existing pump jack equipment with no additional infrastructure required. By supplying heat directly to the downhole fluids, where it is needed, the tool can keep the crude oil above its cloud point or lower its viscosity greatly aiding oil recovery. The installation of the tool is accomplished during a regular workover operation. The heater magnet array (2 to 3 feet long) is screwed into the tubing string (just like another section of tubing). The lead screw is screwed into the sucker rod (just like another section of rod). The tool is typically installed in the tubing right below the location where paraffin is forming thereby providing heat at the location where it is needed (rather than heating the entire wellbore). Power to the tool is provided by the pump jack prime driver. The linear motion of a lead-screw installed in the sucker rod string is converted to the rotary motion of a metal cylinder. This generates eddy currents in the metal cylinder resulting in the generation of about 2KW of heat per foot of magnet length. All this inductively generated heat is transferred to the oil and water as they pass through the tool. The installed equipment does not interfere with the ability to remove the pump from the well and perform maintenance.