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.
A typical NGI log presentation includes: schlumberger ngi tool
By standardizing measurements such as across multi-pad arrays, the NGI system allows operator crews to strip away sub-surface noise and map complex geologic lithologies in real time. The Evolution of Subsurface Imaging Use the CGR (not total GR) in organic-rich
| Feature | Standard LWD GR | NGI Tool | |---------|----------------|----------| | | 10–30 m | 1–2 m | | Time lag | 15–45 min (depending on ROP) | <2 min | | Azimuthal imaging | Often unavailable or coarse | High-resolution, 360° | | Geosteering precision | Reactive | Proactive | | Thin bed resolution | Poor (<1 m beds smeared) | Excellent (<0.3 m resolved) | The Evolution of Subsurface Imaging | Feature |