Prediction Equation for Permeability of Class G Oilwell Cement Under Reservoir Conditions

Experimental assessment of cement permeability is difficult to perform once the cement has been displaced into the wellbore, especially during early hydration. Failure to do so, it may lead to secondary cementing operation that requires additional cost or in the worst case may damage the well. This study proposes an empirical equation for permeability prediction using electrical conductivity at elevated pressure up to 3,000 psi and temperature up to 65 °C during the first 24 h of hydration. The relationship between permeability and normalized conductivity follows power law equation. Better correlation is achieved once the pore diameter parameter is included. The resulting equation is similar to that of Katz–Thompson equation with different constant values. Better agreement is observed for the new proposed equation during 24 h of hydration and also up to 28 days using other cement data. This paper also discusses a relationship between permeability and compressive strength of oilwell cement under reservoir conditions.