For decades, the industry has relied on a suite of logging-while-drilling (LWD) and wireline tools to map the subsurface. Among these, one name stands out when the target is thin-bedded reservoirs, anisotropic formations, or complex structural traps: .
: Four to eight multi-button pads conform directly to uneven borehole walls.
The tool transmits electromagnetic waves from one antenna to a receiver. By comparing the and attenuation between receivers, the complex dielectric permittivity (( \varepsilon^* = \varepsilon' - j\varepsilon'' )) is derived.
: These tools are often part of a broader Wireline Openhole Logging suite, combining resistivity, density, and sonic data to create accurate 3D reservoir models. Applications and Reporting schlumberger ngi tool
: Identifies faults, fractures, and the spatial orientation (dip and strike) of geological layers.
Quanta Geo service's high-resolution geological images accurately position 85 sidewall cores describe the natural fracture system. Ultrasonic Borehole Imager - Acoustic Imaging - SLB
Schlumberger recommends placing the NGI tool as close to the bit as possible (usually within 30-40 feet) to minimize the "measurement lag" between sensing a boundary and reacting to it. For decades, the industry has relied on a
: Provides critical data to decide where to place perforations or hydraulic fractures by identifying "hard streaks" or natural fracture networks.
Historically, standard logging tools measured basic physical properties like natural radioactivity, density, porosity, and resistivity. To get a direct reading of the formation's chemical composition—its mineralogy —a more advanced approach was needed. The was developed to directly measure the elemental makeup of the rock.
To learn more about how NGI data can enhance your formation evaluation, you can explore detailed case studies on SLB.com . The tool transmits electromagnetic waves from one antenna
The software runs a 1D or 3D inversion of the EM data. It creates a visual model of the reservoir showing:
In the high-stakes world of oil and gas exploration, understanding the true geometry of a reservoir is not just an advantage—it is a necessity. Drilling a well is an expensive gamble, and the difference between a commercial discovery and a dry hole often lies in the subtleties of formation evaluation.
Unlike older electrical imaging tools, the NGI delivers enhanced image quality by utilizing an improved array of pad-mounted electrodes, designed to operate in various mud environments, particularly oil-based muds (OBM). Key Technical Features
The NGI tool uses three scintillation detectors. BGO crystals are chosen for their high stopping power (efficiency) at high gamma ray energies.
| Fluid | Relative Permittivity (( \varepsilon_r )) at ~1 GHz | |-------|------------------------------------------------------| | Fresh Water | ~78 - 80 | | Oil | ~2 - 4 | | Gas | ~1 - 2 |