The tool also includes an accelerometer channel to improve data stacking by the precise measurement of logging speed. A specialized telemetry system developed for the MGT allows it to be combined with Schlumberger tool strings in a single logging operation, minimizing the required rig time to acquire the log.
Thin bed analysis. Spectral gamma ray logs provide one of the best means to investigate the mineralogy of thin-bedded sedimentary sequences, Increasing vertical resolution over currently available tools provides new opportunities for log analysis in reservoirs with rapidly changing lithology and for finer resolution of thin layering and in areas with low sedimentation rates. The added resolution provided by the MGT will be of particular use in paleoclimate studies.
Correlation between logging runs
Integration of core and logging data
Paleoclimatology. The added resolution provided by the MGT is particularly useful in paleoclimate studies.
The MGT response is affected by borehole size, mud weight, and by the presence of bentonite or KCl in the mud. KCl is sometimes added to the mud to stabilize freshwater clays which tend to swell and form bridges. This procedure takes place before logging operations start, and even though KCl is probably diluted by the time the tool reaches total depth, it can still affect the tool response.
|Temperature rating:||212° F (100° C)|
|Pressure rating:||10 kpsi (69 MPa)|
|Diameter:||3.375 in (8.6 cm)|
|Length (telemetry module):||9 ft (2.7 m)|
|Length (measurement module):||9.5 ft (2.9 m)|
|Weight:||350 lbs (151.1 kg)|
|Number of spectrometry modules:||4|
|Module spacing:||25.19 in (64 cm)|
|Detector size:||4×2 in (10×5 cm)|
|Maximum cable length :||40 ft (131.2 m)|
|Maximum logging speed :||900 ft/hr (275 m/hr)|
|Cable head connection:||Schlumberger style|
|Sample rate:||4 sec|
|Range (option 1):||±4 g|
|Range (option 2):||±25 g|
|Range:||0-10 kpsi (69 MPa)|
|Resolution:||1 psi (6.9 kPa)|
The MGT is usually run at the top of the Schlumberger string comprising the HRLA, APS, HLDS, and HNGS tools . The downhole switch in the MGT telemetry module provides switching of the signal and power lines between the MGT and the Schlumberger logging system.