Strength prediction of Class G oilwell cement during early ages by electrical conductivity

The compressive strength of oilwell cement
plays an important role in securing the long-term integrity
of wellbore. The cement’s strength development is experimentally
difficult to perform once the cement has been
displaced into the wellbore. Failure to monitor its development
especially during early hydration may lead to
secondary cementing operation or in the worst case may
damage the well. This paper proposes an empirical equation
for strength prediction of Class G oilwell cement 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 study used both porosity–strength correlations and strength–electrical properties relationship to produce predictive equation for strength of oilwell cement.
The proposed equation was experimentally compared to
cement samples with different water–cement ratios and
curing conditions to validate the result. A good agreement
is achieved between the proposed equation and the measured
data. Furthermore, the strength up to 50 days can be
predicted by the proposed equation