Schlumberger

SURVIVOR SDNSC HPHT
Slim Density Neutron Standoff Caliper Tool

Density and porosity measurements in real time

SURVIVOR SDNSC high-pressure, high-temperature (HPHT) slim density neutron standoff caliper tool provides density, porosity, and caliper logs at surface in real time; data is also simultaneously recorded in downhole memory. A cesium-137 source and rugged scintillation detectors are used for highly accurate determination of formation density and photoelectric index. For neutron porosity, the tool uses a low energy californium-252 source and helium-3 detectors, while tool standoff and caliper measurements are provided by a pair of ultrasonic transducers.

As the drillstring and tool rotate, the sensors make measurements at various points around the circumference of the borehole. Readings from the ultrasonic transducers are used to make porosity measurement environmental corrections, and also to provide high-quality bulk density and neutron porosity measurements with the help of a proprietary standoff weighting technique. The transducers are aligned with the density and neutron detectors to improve the accuracy of this algorithm, that gives the highest weight to density and neutron data acquired with the least standoff from the borehole wall. Thus, data of the best possible quality is ensured even when hole conditions are poor.

The tool can operate in environments with pressures up to 25,000 psi and temperatures up to 350 degF [175 degC]. It is available in a nominal collar size of 4 3/4 in, for use in hole sizes ranging from 5 7/8 in to 7 7/8 in.

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