Schlumberger Ngi Tool
Schlumberger NGI (Next-Generation Imager) service is a high-resolution borehole imaging tool specifically designed for use in nonconductive (oil-based) mud environments. It was introduced as an evolution of the OBMI (Oil-Base MicroImager)
- High Th + low K → Kaolinite/Chlorite (good reservoir quality if sand).
- High K + moderate Th → Illite (can reduce permeability).
- Low Th + low K → Smectite (swelling clay risk).
| Tool | Purpose | |------|---------| | Density / Neutron | Total porosity, lithology | | Array Induction (e.g., AIT) | Deep ( R_t ) for true ( S_w ) | | Nuclear Magnetic Resonance (NMR) | Clay-bound water, capillary-bound water, permeability | | Elemental Spectroscopy (ECS) | Mineralogy for dielectric mixing law | schlumberger ngi tool
: Uses a four-terminal measurement method to overcome the insulating properties of oil-based and non-conductive mud systems. Dual Articulated Arms High Th + low K → Kaolinite/Chlorite (good
- Naturally occurring radioactive isotopes (primarily K-40, U-238, Th-232 series) emit gamma rays at specific, discrete energies.
- Gamma rays enter the BGO crystal, producing light flashes.
- A photomultiplier tube converts light into an electrical pulse whose amplitude is proportional to the gamma ray energy.
- The tool's electronics sort these pulses into 256 or 512 energy channels (a process called pulse height analysis).
When reviewing log headers or real-time data, you will encounter mnemonics specific to the NGI-X: : Borehole deviation (inclination). : Hole azimuth. : Pad-weighted azimuth (for imaging tools). : Relative bearing. G-Mnemonics | Tool | Purpose | |------|---------| | Density
Multi-Pad Configuration: Typically featuring four or more pads, the tool ensures high circumferential coverage of the borehole.
VR: Voltage Return (e.g., VRA1, VRA2 for Pad A Frequencies 1 and 2). AMP/PHA: Amplitude and Phase measurements per pad.