| Specification | Details | |---------------|---------| | | 4¾ in, 6¾ in (and other sizes) | | Position | Directly behind the drill bit (shortest sensor offset in the industry) | | Gamma Ray Detectors | Multiple azimuthally‑spaced scintillation detectors | | Measurements | Total gamma ray (gAPI) + Azimuthal gamma ray image + Spectral K‑U‑Th (when calibrated) | | Inclination | Dynamic, high‑frequency (helps correct for tool rotation) | | Max. Temperature | 150°C (302°F) | | Max. Pressure | 20,000 psi | | Data Transmission | Real‑time mud‑pulse telemetry + memory for high‑resolution playback |

A horizontal well targeting a 10-foot porous dolomite zone. Surrounding the target are dense, non-porous limestone and anhydrite.

The transition to the NGI tool offers several key improvements over conventional Formation MicroScanner (FMS) or earlier Formation MicroImager (FMI) devices:

: Telemetry Frame Counter for data synchronization.

By identifying planar features within the rock, the NGI tool allows geologists to calculate the dip (angle and direction) of the rock layers. This data is critical for building accurate structural models, mapping anticlines, and identifying faults. 3. Thin-Bed Evaluation

The NGI tool uses an array of pads to measure formation properties in high detail. Key technical aspects include:

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| Fluid | Relative Permittivity (( \varepsilon_r )) at ~1 GHz | |-------|------------------------------------------------------| | Fresh Water | ~78 - 80 | | Oil | ~2 - 4 | | Gas | ~1 - 2 |

But what exactly is the NGI tool? Why has it become a critical component of modern geosteering and reservoir characterization? This article provides a deep dive into the technology, applications, and operational benefits of the Schlumberger Near-bit Gamma and Inclination (NGI) tool.

– Developed specifically for unconventional oil and gas markets and high‑efficiency drilling applications, the iPZIG helps drillers “steer” a horizontal well within a thin, productive shale layer (the “sweet spot”). An operator in a North American shale play drilled a 5,000‑ft, 8½‑in lateral section using iPZIG at‑bit measurements to control well trajectory and stay in the target zone 100% of the time .

The NGI pad design is designed for better contact with the borehole wall, reducing artifacts and improving signal-to-noise ratios, resulting in clearer, more reliable images.

: The tool is designed to operate reliably under high-pressure and high-temperature (HPHT) conditions common in deepwater and unconventional wells.

: Produces images comparable to those from water-based mud tools, aiding geologists in identifying thin laminations, faults, and stratigraphic features. Primary Applications Fracture Characterization

) measurement. It achieves this through several advanced features:

Conventional resistivity tools often fail to detect gas in certain formations due to: