Description

ApplicationsSchematic diagram of the Multi-Sensor Gamma Ray Tool.

Specifications

ODP Logging Services, Lamont-Doherty Earth Observatory, Rt. 9W, Palisades, NY 10964

Multi-Sensor GammaRay Tool

Logs from the MGT show more finely layered structurethan those of standard gamma tools, which can exhibitpronounced smoothing effects due to their bigger detec-tor size and lower sampling rate

The Multi-Sensor Gamma Ray Tool (MGT) is a completenatural gamma spectrometry system consisting of four gammaspectrometry sensors and a variety of electronics for pulseprocessing and analysis. Each sensor module includes an NaIdetector with an internal calibration source, programmablepower supply, digital pulse analyzer, and pulse heightstabilization circuitry. Individual calibration results for eachsensor are stored in microcontroller memory; thus, themodules are interchangeable and independently replaceable.Spectral data are collected from each of the four individualgamma ray modules, as well as from downhole accelerometerand temperature sensors, and transmitted uphole to the datareceiver in a surface panel. The MGT increases the verticalresolution of natural gamma ray log data by a factor of 3-4over conventional logging tools, allowing for detailedcharacterization of thin bed layering and sedimentary cycleswhen their gamma ray response is sufficiently large.

♦ Clay typing♦ Mineralogy♦ Ash layer detection

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MGT - HNGS ComparisonHole 1194b

MGTNGT

DEPTH, m

MGT Telemetry

MGT Measurement

Four detectors

spaced at 0.6m

Telemetry section

for data transmission

and to switch from

stand-alone to

combination mode

28.1 meters

33.7 meters

Zero

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The data repeatability of the MGT is excellent, as depicted in the figure above.

Deployment of the Multi-Sensor Gamma Ray Tool

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Hole 1179D

MGT Main and Repeat Run

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tac

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Depth, mbsf

11/2001