A review of various scientific logging reports provides a window into the specifications of the NGI tool and its contemporaries.
These arrangements suggest the NGI was primarily a , likely employing a NaI(Tl) scintillation crystal and multichannel analysis to resolve potassium (K), uranium (U), and thorium (Th). It was placed at the top of the tool string to measure natural radioactivity before other tools’ nuclear sources irradiated the formation.
Readily integrates into comprehensive SLB Integrated Wireline Platforms . schlumberger ngi tool
| Feature | Specification | |---------|---------------| | | Approx. 4.5 m (15 ft) | | Diameter | 2.5 in (63.5 mm) – slimhole compatible | | Detectors | 3 BGO scintillators (Near, Far, Long Spacing) | | Max Temp | 350°F (177°C) | | Max Pressure | 20,000 psi (138 MPa) | | Logging Speed | Up to 60 ft/min (18 m/min) – spectral mode | | Vertical Resolution | 6 in (15 cm) – standard; 2 in (5 cm) – high-res mode | | Depth of Investigation | 6–12 in (15–30 cm) into formation (dependent on density) |
Contrary to popular belief, the NGI tool does not replace full LWD suites; it augments them. In a typical high-end BHA for a shale play, you might see: A review of various scientific logging reports provides
: Cartridge Gain values used for real-time signal adjustment. Quanta Geo Photorealistic Reservoir Geology Service | SLB
The Schlumberger NGI (Near-bit Gamma Imaging) tool is a logging-while-drilling (LWD) device positioned directly behind the drill bit. Its primary function is to provide real-time, high-resolution gamma ray measurements with directional sensitivity at the bit . Unlike conventional gamma ray sensors located 10–30 meters behind the bit, the NGI tool delivers near-instantaneous lithology detection, enabling precise geosteering, early formation evaluation, and optimized well placement—especially in thin-bedded or heterogeneous reservoirs. In a typical high-end BHA for a shale
: Identifies faults, fractures, and the spatial orientation (dip and strike) of geological layers.
The high-fidelity images provided by the NGI tool are essential for several key, downhole analyses:
| 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 |
Are you currently planning a wireline logging campaign, or are you looking to optimize data collection in an upcoming well? If you'd like to dive deeper, let me know: