Compensated Spectral Natural Gamma Ray

Principle

Gamma-ray spectroscopy

Max Temp	3500F (1750C)
Max Press	20000psi (137 900 kPa)
Max hole	20 in (510 mm)
Min hole	4.5 in (115 mm)

Vertical Resolution(90%)	standard 36 in. (917.28 mm) enhanced 18 in. (458.64 mm)
Depth of Investigatio(50%)	4 in. (90%: 11 in.) 102 mm (90%: 280 mm)

Precision (1 SD)

± 3% or ± 5 API whichever is larger

Accuracy:	± 5% or ± 5 API whichever is larger
Max hole	20 in (508 mm)
Primary Curves	GRKUT, GRKT, GRTH Uranium, Thorium, Potassium Concentrations
Secondary Curves	Fit Error, Stabilizer Counts, Noise, Source Factor, Uncertainties for each element

In order to use the latest technique of wireline logging and for more accurate lithology analysis of sedimentary and basement rock from 1997, Vietsovpetro L&TD has been using Halliburton’s CSNG™.

CSNG™ provides highly accurate measurements of potassium, uranium, and thorium by detecting the gamma rays they emit. The concentrations of these elements reveal petrological information to help ensure clean rock is not mistaken for shale or clay.

For example: with a standard gamma ray log, high gamma ray counts are frequently interpreted as shale. In the same environment, the CSNG could correctly attribute high gamma ray counts to the presence of uranium or potassium and correctly identify the rock as a potential reservoir.

The CSNG measures the entire gamma spectrum, from 0 to 3000 keV, in both open and cased holes, producing both a primary and a quality log in real-time.

Detect producible zones by accurately distinguishing reservoir rock from those containing clays. Sandstones generally have low potassium and thorium concentrations compared to shale.
Increase reservoir understanding with CSNG data. Fractured or highly permeable reservoirs can be discovered when high uranium concentrations appear with low potassium and thorium concentrations. High uranium and thorium counts with low potassium counts indicate a clean reservoir containing accessory minerals.
Determine clay types, volumes, and caction exchange capacity using CSNG elemental concentration data.
Locate radioactive tracers using the CSNG in Halliburton’s TracerScan™ service.
Identify lithology or determine average casing thickness when the tool is run with the Low-Z case.
Basement’s fracture zones quick indicator. Using Uran-Thor-Pota ratio