Electrical conductivity of Colorado oil shale to 900 °C

Abstract

Electrical conductivity of oil shale from the Anvil Points Mine, Colorado was measured to temperatures > 900 °C with conductance bridges operating at frequencies from 100 to 100 000 Hz. The conductivity of low, intermediate and high grade oil shales (15,124,233 ml kg −1, respectively) is dependent on water content up to ≈ 100 °C. At ≈ 120 °C, values of conductivity at ≈ 10 −7 S m −1 are observed for all grades. A strong, time-dependent, increase in conductivity, beginning at ≈400 °C, marks the loss of light hydrocarbons and the formation of a conductive char. The frequency dependence of conductivity-slightly less than a decade increase in conductivity per decade increase in frequency over the temperature range 100–400 °C-vanishes at temperatures near 500 °C. At 600–800 °C, the conductivity of these oil shales reaches a maximum value which is as much as 10 8 times larger than the conductivity near 250 °C.