Development Of A Practical Ekl (Electrokinetic Logging) System

A new logging system called EKL (Electrokinetic Logging) has been developed. This system can estimate soil and rock permeability by measuring electrokinetic signals. Electrokinetic signals occur when Biot fast P-waves intersect interfaces where hydrogeological properties (e.g. permeability, porosity, fluid conductivity, fluid viscosity, or ionic concentration) change. Such interfaces generate Biot slow P-waves, which decay very rapidly and generate electrical signals. The EKL system measures these electrical signals to estimate the formation hydrogeological properties. The EKL sonde has a magnetostrictive source which emits acoustic waves with two fixed frequencies (around 454 Hz and 2260 Hz) radially in all directions and two electrodes located at about 3 cm and 33 cm apart from the source. Acoustic waves from the source are emitted continuously and electrical potentials generated by means of electrokinetic phenomena are measured at the electrodes. The pressure wave from the source propagates into the formation through the borehole water and generates electrokinetic signals in the permeable formation. The risetime of the generated electrokinetic signal is inversely proportional to the permeability of the formation. Field examples of the electrokinetic responses have shown good reproducibility and signal-to-noise ratio. Estimated permeability logs have also good agreement with the permeability obtained by the packer-test. These field examples have proven that this new EKL system can be a new practical logging technique for estimating soil and rock permeability in a borehole.