Schlumberger Ngi Tool

A unique feature of the NGI tool is its ability to detect resistivity contrasts below the bit. By analyzing the asymmetry in the EM signal, the tool can warn the driller of an approaching shale streak or a fluid contact before the bit penetrates it.

Step 1 – Quality Check Verify that the three detectors agree in smooth sections. Sudzenith divergences indicate borehole rugosity or heavy mud weight effects.

Step 2 – Compute Vsh (Shale Volume) Use the CGR (not total GR) in organic-rich or uranium-rich zones. [ V_sh = \fracGR_log - GR_cleanGR_shale - GR_clean ] But for NGI, use Thorium-based Vsh when uranium is unreliable. schlumberger ngi tool

Step 3 – Identify Clay Mineralogy

Step 4 – Identify Organic-Rich Zones

Step 5 – Geosteering Marker The spectral fingerprint is often unique to a stratigraphic layer, enabling precise correlation across wells.

It is important to note that Schlumberger has largely moved toward the NeoScope family of LWD services. The NeoScope integrates the near-bit concept but adds a crucial feature: resistivity at the bit. This allows drillers to see changes in porosity and fluid type instantly. A unique feature of the NGI tool is

However, the legacy NGI tool remains in active service in many regions (South America, Middle East mature fields, and North Sea) due to its lower cost and high mechanical reliability. For many operators, the "old" NGI is still the most cost-effective solution for gamma-guided geosteering.