Modified Johnson Model for Permeability Estimation in Oil Well Cement During Early Hydration

Permeability is believed to be one of the major factors contributing to the fluid infiltration. Failure
to control this property, especially during early hydration, may lead to secondary cementing operation that
requires additional cost or in worst case may damage the well. Some models have been successfully applied
in relating the cement permeability to its porosity. However, this models rather impractical for field use since
measured porosity must be established first. In this study, the measured electrical conductivity was used as a
tool to extract permeability of Class G oil well cement at elevated pressure up to 3000 psi and temperature up
to 65oC during the first 24 h of hydration. The relationship between permeability and normalized conductivity
follows power law correlation. Neither the Katz-Thompson equation nor Johnson equation differs much from
the measured result, but the latter is closer to the exact result. Better result was obtained once it is fitted to the
measured permeability data which resulting the modified version of Johnson model. New modified model is
satisfied to the measured permeability data generated from other cement samples.