US Patent 7509036 Inline downhole heater

A well bore fluid is being heated to prevent paraffin build-up in the production line by an electrical heating element lowered into a pre-determined subterranean location. The heating element is controlled by a control unit that is connected to a temperature sensor, which detects temperature in the vicinity of the heating element and energizes an above-the-surface electric power source to deliver sufficient electric power to the electric heating element to keep the paraffin substance in a liquefied state.