DEVELOPMENT OF PREDICTIVE EQUATIONS FOR PERMEABILITY AND STRENGTH OF OIL WELL CEMENT USING ELECTRICAL IMPEDANCE

Oilwell cement plays an important role either to seal-off the casing or to isolate
the formation layers from the fluids infiltration that might cause a well bore damage. A
cautious evaluation of cement after displacement is coming to be crucial to secure the
long-term durability and integrity of wellbore. This work in turn is focused on the
utilization of electrical properties for predicting the permeability and compressive
strength of oil well cement.
At present work, an electrical impedance measurement has been used to detect the
conductivity evolution of oil well cement during early hydration. It was then followed
by an examination towards the potential existence of interface conductivity along with
its effects on various water cement ratios, curing temperature and also pressure. In
analyzing the interface conductivity, the evaluation of the electrical responses in the
form of conductivity dispersion characteristics has been done. Together with porosity
data, conductivity data consisting of bulk and pore solution conductivity were
examined to study several composite conductivity models to describe certain changes
in the electrical conductivity of oil well cement system.
Several empirical equations for predicting the permeability and compressive
strength of oilwell cement based on its electrical properties response have been
proposed. To validate the result, the proposed equations were experimentally
compared to other cement samples with different water cement ratios and curing
conditions. A comparison has also been made to the equation proposed by Katz�Thompson and Johnson's and also data from literatures. A good agreement between
the proposed equation and measured data then shows that it is feasible to obtain the
cement's strength and permeability in place using these electrical properties.
Permeability and compressive strength in mature stage, furthermore, can be predicted
by the proposed equations.