The NGI operates on the principle of dielectric dispersion. Water, oil, and gas have distinct relative permittivities (dielectric constants) at high frequencies:
| Fluid | Relative Permittivity (( \varepsilon_r )) at ~1 GHz | |-------|------------------------------------------------------| | Fresh Water | ~78 - 80 | | Oil | ~2 - 4 | | Gas | ~1 - 2 | schlumberger ngi tool
At high frequencies (megahertz to gigahertz), the measured dielectric permittivity is dominated by the water volume, because water molecules have a permanent dipole moment that aligns with the alternating electric field. Gas and oil do not. The NGI operates on the principle of dielectric dispersion
Thus, the NGI can compute water-filled porosity independently of salinity. Formally part of Schlumberger’s PeriScope Edge family, the
For drilling engineers and geologists looking to deploy the NGI, follow these best practices:
The Schlumberger NGI tool is a high-definition LWD resistivity imager designed specifically for real-time reservoir navigation. Unlike traditional propagation resistivity tools that provide average readings over a few feet, the NGI tool delivers ultra-high-resolution borehole images while drilling.
Formally part of Schlumberger’s PeriScope Edge family, the NGI tool is the hardware enabler for "look-ahead" and "look-around" capabilities. It utilizes a multi-spacing, multi-frequency array design that allows petrophysicists to see bed boundaries up to 18 feet away from the wellbore—long before the drill bit actually crosses them.