As the petroleum industry matures, it must locate and extract oil
from deeper and deeper reservoirs under the surface of the earth. The
extraction of oil from deep underground, using oil wells is difficult due to
high viscosity and inclusion of asphalt. The viscosity can be reduced by either
irrigating with hot water, addition of chemicals, or by electric heating of the
pipelines. Electric heating technology is widely used by the oil industry
because of its low cost. A single phase AC source at 40-100 Hz is supplied to
the well wall to provide resistive heating. A basic set up is needed for
heating the oil pipe. The heating loop consists of the oil pipe and heater at
the bottom of the well. When current flows through the loop, it not only
increases the temperature at the bottom of the well but along the pipe due to
the resistance of its walls.
For an
example, we can say that a 50-Hz, 380-V, three-phase, AC power is converted to
a DC bus by the rectifier stage and then inverted using the IGBTs to variable
frequency ranging from 40-100 Hz. The heating efficiency is increased by 50
percent with this approach. The set has advantages of small volume and light
weight because of using IGBT in the inverter system.
