A device includes a channel having an inlet and an outlet, a first electrode disposed within the channel, and a second electrode disposed within the channel so as to define a gap between the second electrode and the first electrode. The device further includes a power source connected to at least one of the electrodes. The second electrode includes a lumen from a first end of the second electrode to a second end of the second electrode. The lumen is configured to introduce a carrier gas to the gap. The inlet is configured to introduce a process stream to the channel. The process stream comprises a viscous petroleum feed material. The power source is configured to produce a spark within the gap, thereby generating a plasma configured to reduce a viscosity of the viscous petroleum feed material and to form a processed petroleum material.