| Fluid | Relative Permittivity (( \varepsilon_r )) at ~1 GHz | |-------|------------------------------------------------------| | Fresh Water | ~78 - 80 | | Oil | ~2 - 4 | | Gas | ~1 - 2 |
) because the measurement is performed entirely on the tool pad. Operational Mnemonics : Common data channels associated with the tool include
| Feature | Detail | |---------|--------| | | Integrated into the bottom hole assembly (BHA), typically 1–2 m behind the bit | | Sensors | Multiple azimuthally oriented scintillation detectors (usually 2 to 16 sectors) | | Measurement | Natural gamma ray API (total count rate) | | Azimuthal Coverage | 360° around the tool | | Data Transmission | Real-time via mud pulse telemetry (compensated for limited bandwidth) and high-resolution memory recording | | Temperature Rating | Up to 150°C (302°F) | | Pressure Rating | Up to 25,000 psi (172 MPa) | | Rotation Speed | Optimal from 60–200 RPM |
Standard tools use coaxial antennas (loops parallel to the tool axis). The uses a combination of coaxial and tilted antennas. By measuring the phase shift and attenuation of EM waves as they pass through different geological layers, the tool calculates anisotropic resistivity (horizontal and vertical resistivity, Rh and Rv).
The Schlumberger NGI tool is a logging-while-drilling (LWD) tool designed to provide detailed information about the subsurface geology and geochemistry of a wellbore. This advanced tool combines nuclear and geochemical measurements to deliver high-resolution images of the formation, enabling drillers to make informed decisions about well placement, trajectory, and completion. schlumberger ngi tool
For a complete evaluation, combine NGI with:
: The tool utilizes a four-terminal measurement principle to overcome the "opaque" effect of nonconductive mudcakes, though its measurement depth is relatively shallow (roughly 0.2 inches) as it is performed directly on the tool pad.
While revolutionary, the NGI tool is not magic.
Unlike the old NGI, the iPZIG creates a true borehole image: | Fluid | Relative Permittivity (( \varepsilon_r ))
: Micro-electrode rows resolve geological variations down to fractions of an inch.
In the Permian Basin and Vaca Muerta, operators need to stay within a specific "landing zone" (e.g., 3 feet below an organic-rich clay boundary). The NGI tool’s deep directional detection identifies the approaching roof shale. The driller can then hold a 90-foot horizontal section with 100% net pay, a feat impossible with gamma-ray-only systems.
The Schlumberger NGI tool is a powerful asset in modern subsurface workflows, bridging detailed borehole imaging with geomechanical insight. When used alongside complementary data and interpreted by experienced teams, NGI outputs can meaningfully reduce drilling risk, optimize completions, and improve reservoir understanding.
When planning your next horizontal well, ask your SLB representative: "Is the NGI tool on the BHA?" If not, you are likely drilling blind. By measuring the phase shift and attenuation of
The represents a milestone in oilfield wireline logging, specifically engineered to deliver high-resolution borehole microresistivity imaging in challenging oil-based mud (OBM) environments. Developed by SLB (formerly Schlumberger), the NGI technology bypasses the historical physical limitations of traditional water-based mud imagers, providing geoscientists and reservoir engineers with photorealistic, core-like structural and stratigraphic evaluation directly from the borehole wall. The Evolution of Mud-Based Borehole Imaging
: By quantifying and differentiating between natural and induced fractures, engineers can better mitigate risks like sanding or borehole instability.
It provides a continuous, 360-degree view of the borehole wall, allowing geologists to accurately determine bed boundaries, dip angles, and sedimentary features like cross-bedding.
The NGI is typically run as part of an integrated wireline logging platform, such as the Platform Express
Uranium frequently precipitates alongside organic matter in low-oxygen depositional systems. By filtering out potassium and thorium, the NGI tool uncovers "computed gamma ray" anomalies, highlighting thin, highly localized sweet spots within unconventional organic shale plays. 3. Fractures and Fluid Migration Characterization
The Schlumberger NGI tool is a sophisticated device that consists of several components:
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